Dry Eyes and Contact Lenses

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D.Ocular surface disease (OSD) is another term used to describe an unhealthy conjunctival and corneal epithelium. Damage to the cornea and conjunctival tissues can occur because of an abnormal tear film, leading to typical biomicroscopic signs such as irregular specular reflection and staining.

E.A National Eye Institute (NEI) workshop has defined dry eye as“a disorder of the tear film due to tear deficiency or excessive tear evaporation that causes damage to the intrapalpebral ocular surface and is associated with symptoms of discomfort.”3

II.Tear film abnormalities have been categorized by Jaanus and Holly.4,5 The NEI describes two major types of dry eye: tear-deficient and evaporative. CLIDE is among the causes of evaporative dry eye.3

A.OSD due to aqueous deficiency is usually referred to as keratoconjunctivitis sicca (KCS). Often, KCS is related to medical conditions. It is usually bilateral and produces a foreign body sensation and reduced lacrimation. This most common tear film abnormality usually results from a decrease in aqueous production by the lacrimal glands. It is commonly associated with primary Sjögren’s syndrome, the sicca complex, and is thought to be autoimmune in origin. Sjögren’s syndrome is associated with collagen-vascular and connective tissue disease, most often rheumatoid arthritis.6,7. It is more common in women who are postmenopausal, but may also occur in women who are pregnant or taking birth control pills, all of whom have elevated levels of estrogen and prolactin. Only 10% of cases are male. Ocular symptoms are often the first manifestation of Sjögren’s syndrome.8 The definition of Sjögren’s syndrome has narrowed in recent years. Rheumatologists define Sjogren’s syndrome as lymphocytic infiltration of the salivary glands. Typically, a biopsy of the salivary glands from the inside of the lower lip is performed. Wetting drops are normally prescribed for KCS as initial treatment.4 Immunomodulating treatments such as steroids or cyclosporine are indicated for more chronic cases.9

A closer look: Rheumatologists define Sjögren’s syndrome as lymphocytic infiltration of the salivary glands diagnosed by biopsy.

B.Mucin abnormality results from altered goblet cell function, resulting in a decrease in mucin production. The function of mucin is to enable the proper spreading of tears across the corneal surface. Dry spots occur in the tear film because of abnormal or inadequate mucin.4,10 Conditions that alter goblet cell function are ocular pemphigoid, Stevens-Johnson syndrome (SJS), allergic conjunctivitis, severe trachoma, contact lens wear, chemical burns, and excessive exposure to preserved ophthalmic preparations.11 Impaired goblet cell function can also result from marked vitamin A deficiency, although this is rare in developed

countries. In ocular cicatricial pemphigoid (OCP) and SJS, goblet cell loss results in immunoglobulin deposits at the basement membrane zone of the conjunctiva. Bullae appear at the conjunctival subepithelial level. Continued progression of this process results in shortening of the conjunctiva and symblepharon formation. Goblet cell density may also increase secondary to thermal and chemical injuries. The resulting ocular surface disorders differ from OCP or SJS at the cellular level, although clinically they appear similar.

C.A lipid abnormality is associated with meibomian gland disease (MGD), blepharitis, and acne rosacea. A lipid-deficient dry eye can also be associated with lid disorders caused by inflammation, trauma, or scarring after eyelid surgery. Normally, the lipid layer inhibits tear evaporation. Abnormalities in the lipid layer result in increased evaporation and insufficient tears.12 In contact lens wear, the lipid layer is disrupted and may be either very thin or incomplete, thereby increasing the tear evaporation rate, leading to CLIDE.13,14

D.Distribution problems such as abnormality of the lids or blink mechanism can predispose the eye to dryness.15 Any structural defect of the lid can interfere with tear film distribution. Poor lid apposition, scar tissue formation, exophthalmos, and lid retraction can lead to ocular surface disease. Restricted lid movement can result in exposure keratitis.4 Incomplete closure of the lids while sleeping constitutes lagophthalmos. Lid abnormality, or blink abnormality, can be caused by Bell’s palsy, thyroid-related eye disease, foreign body (including contact lenses), or lid trauma. Other lid abnormalities that prevent efficient resurfacing of the tear layer include ptosis, lid lag, lid retraction, and madarosis.

E.Epitheliopathy, or tear base abnormality, are alterations in epithelial morphology that can affect tear-film stability. Normally, microvilli on the epithelial surface help bind the mucous glycocalyx and water to the ocular surface. When the microvilli are compromised, nonwetting areas can result.4,10 Unhealthy microvilli, poor glycocalyx, or squamous metaplasia can result in ocular surface disease. Causes can be poor nutrition, chemical burn, Sjögren’s syndrome, OCP, SJS, recurrent corneal erosions, contact lens complications, trauma from entropion, or lash abnormalities such as trichiasis.16

F.Inflammatory changes typically occur in most forms of OSD, including infiltration of the lacrimal gland and ocular surface with inflammatory cells, and the production of proinflammatory substances such as cytokines.17,18 On this basis, dry eye may also be defined as“the result of a localized immune-mediated inflammatory response affecting both the lacrimal glands and the ocular surface.”19

G.“LAMBS” is a useful mnemonic device for remembering the dry-eye categories. L stands for lipid abnormality, A for aqueous abnormality, M for mucin abnormality, B for tear base or epitheliopathy, and S for surfacing abnormality due to lid or blink problems.20

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III.Causes of marginal dry eyes should be determined so that the most effective treatments can be prescribed. Several underlying conditions are associated with dry eyes and should be differentially diagnosed.

A.Lacrimal gland dysfunction can cause reduced tear flow and KCS.21 Viral and autoimmune disease (e.g., herpes, adenovirus, acquired immunodeficiency syndrome [AIDS]22); aging; and systemic medications such as diuretics, antihistamines, and antidepressants can all cause lacrimal gland dysfunction.

B.Meibomian glands secrete the lipid layer of the tear film. The meibum should be clear and resemble clean motor oil in appearance. When the gland is expressed, the meibum should puddle at the orifice. The orifices should not be pouting or distorted. If the meibum is waxy, cloudy, or toothpaste-like, there is MGD.23 Foaming of tears may also be indicative of MGD.24 Native bacteria such as Staphylococcus, systemic conditions such as acne rosacea, and pollution and make-up can cause malfunctioning meibomian glands. Other signs of MGD are rapid tear break-up time (TBUT), papillary hypertrophy, injection, contact lens deposits, and fluorescein staining.25 The meibomian glands can be massaged or expressed to remove the plugs at the openings. Lid hygiene and lid massages are recommended as the first treatment.

C.Blepharitis is associated with dry eyes. The tear evaporation rate is often 10 times faster than normal owing to lack of normal lipid secretions from the meibomian glands. There is a high correlation between blepharitis, MGD, and marginal dry eyes.23 A typical sign is an accumulation of scruff on the lids. Lid massages and scrubs are prescribed to clean up the dead cells.

D.The environment can exert a strong influence on tear film stability. Pollution, toxic fumes, and high levels of dust and fiber can disrupt the tear film. The majority of dry-eye soft lens patients indicate a sensitivity to cigarette smoke, smog, air conditioning, central heating, or some combination of these.26 Frequent use of ophthalmic medications containing harsher preservatives such as benzalkonium chloride (BAK) may also be related to dry-eye symptoms.

E.Blinking should be relaxed, frequent, and complete. Poor blinking has a detrimental effect on contact lenses. Proper blinking is important to replenish the tear film.27 Incorrect blinking has been related to dry eyes, corneal staining, and poor vision from soft lens dehydration. Proper blinking can be taught with blink exercises.28

A closer look: The tear film would not be stable if not for frequent blinking.27

1.The types of blinks are forced, twitch, incomplete, and complete.28

a.A forced blink occurs when the lower lid rises to complete the lid closure. The patient can detect forced blinking by placing the index finger just lateral to the outer canthus. Contraction of

the muscle can be felt with the finger if there is forced blinking. This type of blinking is not correct for contact lens wear.

b.A twitch blink involves a small movement of the upper lid. A twitch blink does not sufficiently cover the eye for contact lens wear.

c.An incomplete blink occurs when the upper lid covers less than two thirds of the cornea. Incomplete blinking leads to exposure and fluorescein staining.

d.A complete blink is ideal for contact lens wear. The upper lid covers more than two thirds of the cornea. There is sufficient coverage of the ocular tissues and contact lens.

2.Blink exercises are prescribed to train proper blinking. Normal blinking should occur at the rate of at least three times per minute.24 Normal blinks need to be relaxed, without any forced movement. Practicing correct blinking entails first relaxing, closing for a count of three, and then opening the eye momentarily (slightly wider than usual). The process is then repeated. Each practice period consists of 10 correct blinks. Ten practice periods per day are typically prescribed to correct poor blinking.28

3.Reading and computer use reduces the frequency and completeness of blinking.29,30 Learning to blink properly during these tasks is important. If problems with blinking are suspected, consider the patient’s reading or computer use habits.

IV. Many dry-eye problems can be prevented if the clinician is familiar with potential risk factors. Many of these risk factors are covered in standard questionnaires such as the McMonnies31 or Ocular Surface Disease Index (OSDI)32

(Fig. 21-1).

A closer look: Clinical history is one of the “gold standards” for diagnosis of dry eyes.31

A.Age and sex are predispositioning factors for dry eyes. There is a reduction of tear flow for patients older than age 40 years. The incidence of MGD increases with age.33 Women who are older than 40 are more likely to have postmenopausal reduction of tear flow and Sjögren’s syndrome.24,31,34

B.Different types of contact lenses pose different risk factors. Contact lens wear in itself requires a higher-quality tear film. If there are dryness symptoms with no lenses, dryness will certainly worsen with lenses. Gaspermeable lenses are better for dry eyes than soft lenses. Any type of lens stresses the tear film, however. Normally, the tear film is meant to cover the back of the lid and ocular surface. Contact lenses need enough tears to cover the back of the lid, the front of the lens, the back of the lens, the edge meniscus, and the ocular surface. If the lenses are soft, additional tears are necessary to wet the lens itself.1

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C.A past history of dry-eye treatment, such as use of drops, usually indicates a preexisting condition. Knowledge of past treatment strategies and their effectiveness is very helpful.

D.Symptoms indicative of dry eyes include foreign body sensation, tearing, burning, and dryness. The symptoms are usually worse at the end of the day.2 Patients suspected of having dry eye should be asked if any of the following nine key words describes how their eyes feel: hot, dry, burning, itching, smarting, scratchy, gritty, water, and tear. Be aware that, unfortunately, the signs do not always correlate with the symptoms. Different signs appear with different types of dry eyes, making diagnosis confusing and difficult.31

A closer look: Ninety-eight percent of watery eyes are related to ocular surface disease, not an overabundance of tears.5

E.Sensitivity to irritants sometimes translates into a dryness problem. Influential factors are: cigarette smoke, smog, air conditioning, central heating, swimming, and drinking alcohol. All of these factors have been shown to be related to dry eyes.31

F.Medications can produce dry eyes as a common side effect. Antihistamines, diuretics, tranquilizers, isotretinoin, and oral contraceptives may cause dryness. Medications for high blood pressure, digestive problems, and glaucoma are also related to dry eyes.24,31

G.Rheumatoid arthritis is related to dry eyes. A history of arthritis with dryness in the nose, mouth, chest, or vagina can be related to dry eyes.

H.Corneal exposure clearly places the patient at risk for dry eyes and damage to the ocular surface.

1.Graves’ disease and other thyroid problems are associated with corneal exposure. Exophthalmos and upper lid retraction cause incomplete corneal coverage by the lids. The tear film thins and the cornea can become damaged, with concomitant pathological changes in the tear film.35,36

2.Lagophthalmos is incomplete lid closure when sleeping. The patient is usually unaware of the condition. Often, family members report that the patient “sleeps with the eyes open.”31 Patients typically report itching, burning, or a foreign body sensation on awakening.

3.Epithelial basement membrane disorders are often associated with dry eyes. Irritation or foreign body sensations in the morning on awakening are classic symptoms.

I.Allergies predispose a patient to dry-eye problems with contact lenses. Treatment of the allergy should be the first priority before any other measures are taken. Ocular allergy may be treated acutely with a non-

steroidal antiinflammatory drug (NSAID) such as Acular (Allergan), a steroid such as Alrex (Bausch & Lomb), antihistamine such as Elestat

(Allergan/Inspire), or antihistamine/mast cell stabilizer such as Patanol (Alcon) or Zaditor (Novartis). Chronic symptoms are better addressed with a mast cell inhibitor such as Alocril (Allergan) or Alamast (Santen). Over-the-counter antihistamines are also available.37

V.One or more tests of tear function are necessary to properly assess dry eye. It is advisable to examine the eye in the biomicroscope with white light first before performing any tests. Manipulation of the lids and even blinking can unintentionally express the meibomian glands, changing the lipid layer.38

A.Schirmer’s test involves applying a paper strip to the lower lid and measuring the amount of wetting occurring over a specific time-period (usually 5 minutes).39,40 It may be performed with (Schirmer II) or without anesthesia (Schirmer I) to measure basal or reflex tear production, respectively. Although its accuracy has been questioned39,40 it is a mainstay of dry eye diagnosis and has recently proved useful in documenting the efficacy of new treatments for dry eye.41 If anesthesia is used, readings of 10 mm or less in 5 minutes are indicative of tear production problems.

A closer look: Schirmer I is without anesthesia; Schirmer II is with anesthesia.

B.The phenol red test, also called the cotton thread test and commercially available as Zone-Quick, is related to the Schirmer test. Instead of a paper strip, a 70-mm thread impregnated with phenol red is inserted into the lower lid for 15 seconds. When the thread absorbs the tears, color changes from red to yellow because of tear pH, and the amount of string that turns yellow is measured. The test is much less irritating and faster than the Schirmer test. A normal reading is greater than 15 mm, with less than 9 mm diagnostic for dry eye. The interpretation of this test has been called into question.42

C.TBUT is a generally accepted measure of tear film stability. Fluorescein is placed onto the ocular surface and the time it takes for dark areas to form is measured. Full-beam observation of the cornea is preferable to scanning the cornea with a narrow slit.43 Results of less than 10 seconds indicate a tear-film deficiency and probable contact lens intolerance.1,44 Reliability questions arise because the instillation of fluorescein can destabilize the tear film and affect results. Recently, a modified (smaller) fluorescein strip has been introduced that delivers less fluid to the tear film and provides more reproducible TBUT measurements.45 The narrowed strip is referred to as the DET test (not currently available).

D.An alternative to the standard TBUT is the noninvasive breakup time measurement (NITBUT), which circumvents the problem of tear film disruption.46,47 NITBUT entails projecting a grid or mire onto the tear layer and measuring the time it takes to disrupt. Typically, NITBUT is higher than TBUT because the application of fluorescein is omitted. A 10-second

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or less NITBUT test result indicates a suspect dry eye with a grid, and 5 seconds or less may indicate a dry eye with a keratometric mire.1

A closer look: Dry-eye damage can be demonstrated to the patient by having the patient look in the mirror after Rose Bengal staining.

E.Lacrimal equilibration time (LET) has been proposed as a simple test for dry eye. It involves the instillation of drop of Celluvisc (Allergan) in each eye and timing how long it takes to regain predrop visual acuity. Asymptomatic patients take 2 to 3 minutes to clear, and symptomatic patients take greater than 10 minutes to clear.48,49 Recently, the relationship between drop viscosity and duration of acuity loss has been reported in detail using contrast sensitivity testing.50

F.The specular appearance of the lipid layer can help in determining the quality and thickness of the tear film. A gray, thin layer may be too sensitive to evaporation, while a thick, colorful layer may leave lipid deposits.51 An instrument was developed to observe the lipid layer (the Tearscope, Keeler Instruments), but is no longer commercially available in the U.S. (see Chapter 3). More sophisticated research instruments have also been developed to study the interferometry of the lipid layer.52 When observed, the normal lipid layer may have a marble-like (marmoreal), flow, wave, or amorphous appearance, and may exhibit a more open or closed meshwork pattern. Both the pattern and the overall color correlate with tear stability and lipid layer thickness.12,52-56

1.Yokoi et al. classified the lipid layer appearance with an interferometer. They found correlation of severity of dry eyes with the classification system.

a.Grade 1 is a lipid layer somewhat gray in color with uniform distribution.

b.Grade 2 is somewhat gray in color and non-uniform distribution.

c.Grade 3 is a few colors and nonuniform distribution.

d.Grade 4 is many colors and nonuniform distribution.

e.Grade 5 has the corneal surface partially exposed.57

G.The tear meniscus or tear prism can be seen resting on the lower lid, using the biomicroscope. The tear meniscus can be evaluated according

to four characteristics: height, width, regularity, and curvature.

A height of 0.3 mm is considered normal. An abnormal tear prism has a lower height and appears uneven or scalloped.

1.An aqueous deficiency or lipid abnormality will affect the tear meniscus. A scanty meniscus appearance and areas of discontinuity are signs of tear abnormalities.

2.The tear meniscus may be classified with regard to zones of irregularity.

a.The intact category has no zones of irregularity and appears in the normal eye.

b.The intermittently nonintact category has zones of irregularity, but these are not always present. This is an abnormal meniscus.

c.In the permanently nonintact category, zones of irregularity are present at all times. A meniscus of this type indicates a risk for many dry-eye problems.

3.Peripheral height measurements are a simple and effective clinical technique described by Guillon. Central height (under the pupil) and peripheral heights (5 mm nasally and temporally) should be about equal. Differences between heights indicate irregularity.63

4.A pillar-like flare image can be detected by the patient as a result of the meniscus. When looking at a bare light bulb against a black background, the tear meniscus forms a flare image. The patient can report the time it takes for the pillar-like image to disappear. Dry-eye patients report disappearance in a short 3 to 10 seconds.64

5.Black line formation can be seen on the ocular surface immediately adjacent to the meniscus. Application of fluorescein enhances its appearance. The anterior and posterior surfaces of the tear in this thin area cancel each other out, forming the black line.65 The black line area is the most unstable part of the entire tear film. The black line can also be seen at the edge of rigid lenses while on the eye.

6.Recently, optical coherence tomography (OCT) has been used to study the tear meniscus, allowing quantitative analysis of its height and volume.66 With use of this method, typical meniscus heights in normal subjects are 0.15 to 0.20 mm, somewhat smaller than those seen with standard biomicroscopic measurements.

H.A lactoferrin test measures the amount of lactoferrin in the tears. Lactoferrin is a protein secreted in the tears primarily by the main lacrimal gland that has a role in ocular defense against pathogens. Because its concentration in the tear secretions should be fairly constant for most patients over time, its potential use as a marker of lacrimal gland function was recognized in the early 1980s,67 and an antibody-based test for its presence was developed for routine clinical use. The lactoplate and later the lactocard assays are relatively easy to administer, and some reports indicate that their results correlate well with other measures of dry eye.68 The technology has recently been improved with a quantitative reader for the test results, and is sold as the Touch Tear MicroAssay System (Touch Scientific). However, other reports indicate that the test is not a reliable indicator for some patient populations.69,70 The conclusion one reaches is that a lactoferrin test may be useful to confirm suspected lacrimal insufficiency as a cause of dry eye, and may assist in discriminating between aqueous deficiency and evaporative dry-eye problems.

I.Tear osmolarity measures the tonicity or salt content of tears. For years after it was first described, measurement of tear film osmolarity was touted as the “gold standard” in diagnostic techniques for dry eye.68,71-74 Numerous reports have demonstrated that the tear fluid becomes more hypertonic in most if not all dry eye patients,75-78 and tear osmolarity does

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appear to change predictably (increases with worsening, decreases with improvement) in most patients. Unfortunately, accurate measurement of osmolarity is technically difficult and subject to numerous sources of variability from day-to-day fluctuations to collection technique.79,80 More recently, a more user-friendly osmometer capable of processing the small volumes of human tear samples has been in development,81 which may allow tear osmometry to become accessible to routine clinical practice.

J.The condition of the cells of the ocular surface is usually assessed with one or more staining techniques. The hallmark of moderate-to-severe dry eye or OSD is increased staining, indicating deficiency in the mucin layer, damaged surface cells, or loss of epithelial barrier function.5

1.Fluorescein staining is a very simple and easy test that reveals dryeye problems. Dry-eye staining has been reported with one third of soft-lens wearers. Desiccation staining usually appears in the inferior portion of the cornea for lens wearers. Sometimes it takes the form of a“smile-shaped” stain in the inferior midperipheral cornea. Other times it is located in the central cornea. It is, however, rarely seen in the superior cornea. Desiccation staining can be light and punctate or progress to confluent patches. The most severe cases can progress even further to full-thickness erosions. Thin lenses are more likely to have desiccation staining than thicker lenses. High humidity and mid water thick lenses help alleviate dry-eye staining.1

a.Peripheral corneal desiccation, or 3- and 9-o’clock staining, can be related to dry eyes in gas-permeable (GP) lenses. Numerous factors cause this staining. If a tear abnormality is one of the predominant causes, treatment with lubricating drops should be initiated.

b.Staining may indicate areas of incomplete corneal epithelial barrier function and leads to increased risk for bacterial infections.1

c.Bulbar conjunctival staining is commonly seen with dry eyes, with or without contact lenses. The staining usually appears along the exposed horizontal bulbar conjunctiva.14 Conjunctival staining indicative of dry eyes can occur without the presence of corneal staining.

A closer look: Conjunctival staining indicative of dry eyes can occur without the presence of corneal staining.

d.Loss of corneal luster is another sign of dry eyes. The cornea appears dull and is accompanied by staining and a hyperemic conjunctiva.

2.Rose Bengal stains areas of inadequate mucous protection of the corneal epithelium.48,82 Typically, a 1% drop is applied to the eye,

which may be irritating. Applying the drop with a cotton-tip applicator reduces the amount of dye and provides less irritation. With a green biomicroscopic filter, corneal and conjunctival staining can be seen in dry-eye patients. The stain usually appears in the inferior nasal bulbar conjunctiva.48 Koh et al. has shown fluorescein staining with a yellow filter to be better at detecting conjunctival staining than Rose Bengal for mild to moderate dry eyes.83

A closer look: Fluorescein staining with a yellow filter is better at detecting conjunctival staining than Rose Bengal for mild-to-moderate dry eyes.83

3.Lissamine green is a newer stain that has also been used to demonstrate ocular surface damage in dry-eye disease, and has been recommended for observation of conjunctival changes. It may be applied via a moistened strip or as a liquid, and the dye is best observed in lowintensity white light. It is reported as less irritating than Rose Bengal.84

4.Hypofluorescence occurs when the eye does not fluoresce on the instillation of fluorescein. If the eye is dry, the dye accumulates in flakes on the conjunctiva. Fluorescence does not occur unless a saline drop is added or the patient forces blinking. The severity of dryness can be categorized by the time required for fluorescence after a saline drop is instilled. Immediate fluorescence is normal, and gradual fluorescence is considered subnormal.20

VI. Management of CLIDE usually involves wetting agents. If wetting agents are not effective, more complex options are necessary. Sometimes, the dry eye may be so intractable that lenses cannot be worn.

A.Wetting agents are commonly the first treatment prescribed for dry eyes with or without contact lenses. The disadvantage of drops is their short time of effect—a common complaint is that the drops work only for a few minutes after instillation.85

Generally, rewetting drops contain the following ingredients:

1.Isotonic saline base, sometimes supplemented with additional electrolytes (e.g., potassium, calcium, and magnesium), also including a buffer such as borate, phosphate, or citrate.

2.One or more lubricants such as a cellulosic polymer (e.g., carboxymethylcellulose [CMC], hydroxypropyl methylcellulose [HPMC]), or another ophthalmic demulcent such as povidone, dextran 70, or glycerin.

3.A preservative such as sorbic acid, polyhexamethylene biguanide (PHMB or Dymed®), polyquaternium-1 (Polyquad®), or oxychloro complex (Purite®), sometimes supplemented with EDTA.

4.Multipurpose-derived rewetting drops also contain a surfactant, which may assist in debris removal and lubrication.

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For the contact lens wearer, selection of a rewetting drop should address these issues:

a.How often does the patient need to use drops? Those needing drops only once or twice a day, or only when exposed to environmental irritation (e.g., dry or dusty conditions, or air conditioning) will gain adequate relief from any drop. In cases of more regular and frequent use, MPS-based drops containing harsher preservatives and surfactants should be avoided. For very frequent use or sensitive patients, nonpreserved drops (e.g., Refresh Plus, Allergan) may be indicated.

b.Is there an indication of rapid build-up of debris and deposits on the lens? In some cases, rewetters having an in- the-eye cleaning function (e.g., Clerz-2, Alcon, or Blink- N-Clean, AMO) may be useful. The in-the-eye cleaning function may also be useful for extended or continuous wear patients as a waking routine following overnight wear.

5.Sodium hyaluronate is a component of the newest contact lens rewetters. It is used in CIBA Vision’s Focus AQuify and AMO’s Blink Contacts. Sodium hyaluronate is the sodium salt of hyaluronan, a chain of repeating disaccharide units composed of D-glucuronic acid and D-N-acetylglucosamine. The center of the chain is relatively hydrophobic, whereas the side chains are more hydrophilic. This causes the sodium hyaluronate chain to resemble a twisting ribbon. One gram of sodium hyaluronate can bind up to 6 L of water.86 In the eye, studies suggest that sodium hyaluronate enhances water retention on the corneal surface and increases corneal wettability.87 When the eye is open, the polymer chains of a sodium hyaluronate solution applied to the eye are coiled randomly and are disorganized and entangled with one another, resulting in a high viscosity fluid. The higher the concentration of sodium hyaluronate, the more viscous the fluid. When a patient blinks, the sodium hyaluronate polymer chains align themselves in the direction of the shear force, decreasing viscosity. This allows for quick, even spreading of a sodium hyaluronate lubricating layer across the corneal surface without visual blurring. Between blinks, the sodium hyaluronate chains recoil to their high viscosity configuration. TBUT has also been shown to increase with the use of sodium hyaluronate containing eye drops.88

Table 21-1 lists some of the current lens rewetting drops available, with their ingredients. Note that most contain a lubricant for additional comfort, and the majority are preserved to provide multidose convenience.

A closer look: Prevention is the key when using drops. Use the drops frequently before the eye dries out.

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6.For patients with more persistent dry-eye symptoms, use of artificial tears is indicated. There are many of these, including both preserved and nonpreserved (unit-dose) products. Although many of these may be safe to use while wearing lenses, FDA labeling regulations do not allow a single product to be labeled for both contact lens rewetting and dry-eye treatment. Therefore, the conservative recommendation is to remove lenses prior to drop application, and to wait 15 to 30 minutes before lens insertion following drop use. For lens wearers, artificial tears containing potentially irritating preservatives such as BAK, cetrimide, or mercuric compounds as preservatives should probably be avoided. These compounds may accumulate in the lens and lead to a red, irritated eye.

Selection of an artificial tear for dry eye treatment should include attention to:

a.The lubricant: identity of the lubricant substance or demulcent and its concentration will determine viscosity and other properties such as mucoadhesion that will impact clinical benefit. Demulcents demonstrated to be effective include CMC and HPMC. Higher concentrations of either of these will be more viscous.

b.Preservative: dry eye drops are typically used frequently (2-6 times per day) over long periods, and applied to an already compromised corneal surface. Minimized exposure to potential further irritation from preservatives is recommended. Use of nonpreserved products, or transiently preserved products containing oxychloro complex (Purite, in Refresh products from Allergan) or perborate (Dissipate or GenAqua found in a variety of products) is preferred for chronic dry eye patients. BAK and EDTA should be avoided where possible.89

c.Other beneficial ingredients: additional electrolytes (potassium, calcium, magnesium, and zinc) may be present and are helpful in supporting healthy ocular surface metabolism.90,91 In addition, some products contain gelling agents (e.g., carbomer and guar gum) to add viscosity.

A closer look: Occlude the puncta with an index finger for 30 seconds to prolong contact time and benefit of an artificial tear.

B.Ointments are usually composed of petrolatum, mineral oil, and sometimes lanolin. The high oil content is not compatible with lens wear. Patients who are allergic to wool may react to lanolin. Ointments are meant to melt at eye temperature and disperse into the tears. Ointments have much longer retention times than drops do.4 Unfortunately, vision is temporarily blurred after instillation. The ointments are best used before sleeping, which makes them especially useful for lagophthalmos.

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Meibum in blocked glands has a high melting point, and application of heat and massage loosens the waxy meibum in the blocked glands. The washcloth can also be used to clean the lids of the scruff and flakes commonly seen with an associated blepharitis. Lid massage should be repeated for a total of two or three times. The glands are then expressed with firm digital pressure on the lower and upper lids. Lid massages should be performed at least twice a day. In the case of blepharitis, lowdose oral tetracycline or doxycycline has been suggested as a beneficial adjunct to lid scrubs and warm compresses.98,99 More recently, oral ciprofloxacin has also been suggested for a similar treatment effect, presumably due to its anti-inflammatory as well as antibiotic properties. The benefits of these medications are also thought to be due to improvements in meibomian oil quality or mobility within the lids. The role of androgen hormones in supporting meibomian gland function has been reported,100 and new treatments based on this concept are in development.25 Artificial tears containing a lipid component (e.g., Endura, Allergan; Soothe, Alimera) may also be useful in the management of MGD.

E.Punctal occlusion is used for tear preservation. It can be explained to patients that the tear film system is like a sink, with the inflow from the tear glands and the outflow through the puncta. Plugging the drain better allows the tears to remain on the surface of the eye. Collagen plugs that dissolve are useful as temporary plugs to determine the effectiveness of punctal occlusion in preserving tears.

1.The procedure is to place the plugs in both the upper and lower puncta of the most symptomatic eye. Both puncta should be occluded because the outflow from the nonoccluded punctum can compensate for the occluded punctum. The plugs are 3 mm in length and available in several diameters. Anesthetic drops should be used to reduce blink reflex and make the lids more flaccid. Holding the plug with a jeweler’s forceps in one hand and pulling the lid laterally to straighten the canaliculus with the other hand, the clinician advances the plug until it disappears. The plugs should be pushed below the lid margin.

2.After instillation, the patient should be warned that the plugs may be itchy. The plugs may be noticeable on extreme angles of gaze. Some clinicians instill an antibiotic drop in each eye after the procedure. Lubrication therapy should be continued. The plugs dissolve in a few days, resulting first in immediate relief, then a decline in comfort.

3.Once the usefulness of punctal closure has been determined with collagen plugs, a “permanent” plug, usually made of silicone, is inserted. There are several designs for these, including standard ones with a visible cap at the punctal orifice, those with a cavity so that tear drainage is slowed but not stopped, and intracanalicular plugs that are inserted wholly within the canaliculus. The most common problems with these punctal plugs are a high probability of

spontaneous extrusion, as plug life has been estimated from clinical studies in patient populations to typically range from 6 to 19 months.101,102 Secondarily, there will be some incidence of conjunctival abrasion from the protruding end.

4.For chronic dry eye patients who benefit from punctal occlusion, cauterization or other surgical occlusion of the punctate may be indicated. Several methods have been developed, including the use of thermal as well as laser technologies. Most reports indicate good success with these methods.103-106

5.Possible disadvantages are epiphora and irritation from a dislodged plug. It has also been argued that particularly in more severe dry eye patients, punctual plugs allow the accumulation of irritating proinflammatory substances on the ocular surface. Reduction of the inflammatory state of the eye with pulsed steroid or cyclosporine treatment (see below) may be appropriate prior to insertion of plugs.

F.Pharmacologic treatment to reduce the inflammatory basis of dry eye disease is available.

1.Cyclosporin: Recent research has indicated that much of chronic dry-eye disease has an immune-based inflammatory component, so the recent approval of Restasis (Allergan), the 0.05% cyclosporine ophthalmic emulsion for treatment of chronic dry eye or keratoconjunctivitis sicca has been a welcome addition. This commercial product has been in development for a number of years and was approved by the FDA on the basis of significantly more patients improving in both signs and symptoms as compared to vehicle.41 It should be noted that the vehicle in this case is a castor oil emulsion very similar to Allergan’s Refresh Endura, so that this was quite a high hurdle. The use of the emulsion vehicle allows for the effective delivery of therapeutic levels of cyclosporine at a low total concentration. Indications for use state that Restasis is intended“to increase tear production in patients whose tear production is presumed to be suppressed due to ocular inflammation associated with keratoconjunctivitis sicca.”

Although systemically delivered cyclosporine is an immunosuppressive drug with potentially powerful effects, ocular administration of this low concentration of drug did not produce any detectable level of cyclosporine in the blood, and there were no significant systemic side effects reported. The primary ocular adverse reaction reported is transient burning and stinging upon instillation in 17% of patients. Despite the immunosuppressive properties of the drug, there was not an increase in ocular infection rate in patients using Restasis.

Administered topically in low concentration (0.05%) cyclosporine appears to be an immunomodulatory rather than an immunosuppressive agent. On the ocular surface, reduction in T cell counts107 and levels of cytokines108,109 have both been reported as a result of

464 SPECIAL TOPICS

cyclosporine use. These effects and possible direct effects on the lacrimal gland are presumably responsible for the observed clinical benefits.

a.Hom found cyclosporine to be effective for contact lens related dryness.110 Patients used cyclosporin A twice a day without contact lenses in place. After 5 weeks, cyclosporin A treatment showed statistically better results than the control in temporal bulbar conjunctival fluorescein staining, use of rewetting drops during lens wear ,and subjective evaluation of dryness measured with severity score.

2.Steroid pulse therapy. Prior to the approval of topical cyclosporine, the inflammatory nature of more severe forms of chronic dry eye had been recognized, and short courses or“pulses” of steroids have been recommended by some clinicians. A clinical trial of steroid treatment for moderate-to-severe dry eye has reported good results, but a significant incidence of adverse effects including elevated intraocular pressure and exacerbation or appearance of cataracts.111 Such use of steroids for dry eye needs to be closely monitored, and the risk for serious side effects is considered high for long-term use. With the introduction of “soft” steroids, particularly loteprednol etabonate (Lotemax or Alrex, Bausch & Lomb), indicated for ocular allergy, some authors have suggested their use for dry eye as well.112,113 Most likely, use of cyclosporine emulsion will replace steroids as a treatment of choice for the chronic inflammation associated with dry eye. As an additional alternative, the use of a topical nonsteroidal antiinflammatory medication for dry eye has also been reported on a pilot basis.114

G.Saline soaks can prolong wearing time. The soft lens is rehydrated at midday. It is soaked in saline for 15 minutes and then reapplied. A variation is keeping an extra set of lenses. At midday, the other pair of lenses is applied to the eye.

H.Environmental factors can be altered to optimize conditions for the patient with dry eyes. Low humidity, low atmospheric pressure, air pollution, and moving air promote more lens dehydration.44,115 Irritating factors such as wind and dust can create dryness.24

1.Humidifying the environment has been shown to relieve symptoms. The lipid layers inhibiting evaporation on soft lenses are very sensitive to humidity.116 Use of humidifiers for the home and office is recommended. Air purifiers are also useful to remove particles that irritate the eye.

A closer look: More than 75% of soft lens wearers reported alleviation of all dry-eye symptoms with high humidity.14

2.Avoiding drafts and excessive air conditioning is helpful. Exposing the eyes to direct ventilation hastens drying.1

3.Spectacles increase humidity at the ocular surface. Larger wraparound spectacles give the best results. Wearing spectacles for indoors and outdoors is also very helpful.24

A closer look: Sometimes dry eyes can be alleviated with something as simple as wearing sunglasses outdoors.

4.Shields and goggles can be prescribed for severe dry eyes. The humidity shields attach to the spectacles. The main drawback is the unusual appearance. Airtight goggles such as those used for swimming are the most effective.

I.Tarsorrhaphy is a surgical closure of the lids reserved for cases of severe, unresponsive disease, especially in nerve paralysis. Initially, the lateral third of the palpebral fissure is sutured shut. When this measure is insufficient, a complete tarsorrhaphy is performed.

J.Use of diluted blood serum (the patient’s own) as a therapeutic eye drop has been reported. Such autologous serum is extracted from collected blood by centrifugation, diluted to 10% with sterile saline, and used as an eye drop. It has been proposed that serum contains nutrients and growth factors that promote ocular surface healing and help suppress inflammation.117

K.It is useful to group the various dry-eye therapies into stages. The first stage is tried first, and if the treatments are ineffective, the treatments in the next stage should be initiated.20

1.First-stage dry-eye therapy consists of artificial tears and lid massages (if signs of MGD are present).

2.Second-stage dry-eye therapy consists of moist-chamber spectacles (shields and goggles), thicker artificial tears including gels and ointments, and medications such as cyclosporine.

3.Third-stage dry-eye therapy consists of punctal occlusion, possibly other surgical procedures, and use of autologous serum.

VII. The prognosis for dry eye is guarded in many cases. The treatment may represent only a maintenance strategy. Multiple evaluations may be necessary to establish the diagnosis and to determine the minimum treatment that produces results. Once a treatment plan has been shown to be effective, the clinician should provide follow-up care at appropriate intervals to encourage compliance and continued effectiveness.

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41.Sall K, Stevenson OD, Mundorf TK, Reis BL. Two multicenter, randomized studies of the efficacy and safety of cyclosporine ophthalmic emulsion in moderate to severe dry eye disease. CsA Phase 3 Study Group [published erratum appears in Ophthalmology 2000 Jul;107(7):1220]. Ophthalmology 2000;107(4):631-639.

42.Tomlinson A, Blades KJ, Pearce EI. What does the phenol red thread test actually measure? Optom Vis Sci 2001;78(3):142-146.

43.Cho P, Brown B. Review of the tear break-up time and a closer look at the tear break-up time of Hong Kong Chinese. Optom Vis Sci 1993;70(1):30-38.

44.Andres S. Factors of the precorneal tear film break up time (BUT) and tolerance to contact lens. ICLC 1987;14:103-107.

45.Korb DR, Greiner JV, Herman J. Comparison of fluorescein break-up time measurement reproducibility using standard fluorescein strips versus the Dry Eye Test (DET) method. Cornea 2001;20(8):811-815.

46.Cho P, Douthwaite W. The relation between invasive and noninvasive tear breakup time. Optom Vis Sci 1995;72(1):17-22.

47.Mengher LS, Pandher KS, Bron AJ. Non-invasive tear film break-up time: sensitivity and specificity. Acta Ophthalmol (Copenh) 1986;64(4):441-444.

48.Pflugfelder SC, Tseng SC, Yoshino K, et al. Correlation of goblet cell density and mucosal epithelial membrane mucin expression with rose bengal staining in patients with ocular irritation. Ophthalmology 1997;104(2):223-235.

49.Lavaux JE, Keller WD. Lacrimal equilibration time (LET): a quick and simple dry eye test. Optom Vis Sci 1993;70(10):832-838.

50.Ridder WH, III, Sawamura M, Tong J, Bender E. The effect of artificial tears in the tear layer on contrast sensitivity. Optom Vis Sci 2001;78:12s.

51.Korb DR, Greiner JV. Increase in tear film lipid layer thickness following treatment of meibomian gland dysfunction. Adv Exp Med Biol 1994;350:293-298.

52.Doane MG, Lee ME. Tear film interferometry as a diagnostic tool for evaluating normal and dry-eye tear film. Adv Exp Med Biol 1998;438:297-303.

53.Doane MG. Abnormalities of the structure of the superficial lipid layer on the in vivo dry-eye tear film. Adv Exp Med Biol 1994;350:489-493.

54.Guillon JP. Use of the Tearscope Plus and attachments in the routine examination of the marginal dry eye contact lens patient. Adv Exp Med Biol 1998;438:859-867.

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55.Guillon JP. Abnormal lipid layers. Observation, differential diagnosis, and classification. Adv Exp Med Biol 1998;438 (Lacrimal Gland, Tear Film, and Dry Eye Syndromes, ed 2. Sullivan et al., Plenum, New York):309-313.

56.Hamano T. The tear film and contact lens wear. In: Hamano H, Kaufman HE, eds. Corneal Physiology and Disposable Contact Lenses. Boston: ButterworthHeinemann, 1997:27-41.

57.Yokoi N, Takehisa Y, Kinoshita S. Correlation of tear lipid layer interference patterns with the diagnosis and severity of dry eye. Am J Ophthalmol 1996;122(6):818-824.

58.Doughty MJ, Laiquzzaman M, Button NF. Video-assessment of tear meniscus height in elderly Caucasians and its relationship to the exposed ocular surface. Curr Eye Res 2001;22(6):420-426.

59.Nichols KK, Nichols JJ, Lynn MG. The relation between tear film tests in patients with dry eye disease. Ophthalmic Physiol Opt 2003;23(6):553-560.

60.Oguz H, Yokoi N, Kinoshita S. The height and radius of the tear meniscus and methods for examining these parameters. Cornea 2000;19(4):497-500.

61.Yen MT, Pflugfelder SC, Feuer WJ. The effect of punctal occlusion on tear production, tear clearance, and ocular surface sensation in normal subjects. Am J Ophthalmol 2001;131(3):314-323.

62.Yokoi N, Maruyama K, Kinoshita S, et al. Dynamic changes in tear meniscus curvature at the rigid contact lens edge. Cornea 2003;22(3):226-229.

63.Guillon JP, Guillon M. The role of tears in contact lens performance and its measurement. In: Ruben M, Guillon M, eds. Contact Lens Practice. London: Chapman

& Hall Medical, 1994:453-483.

64.Fatt I. A measurable subjective patient response to the dry eye. CLAO

J1994;20(4):249-252.

65.Wong H, Fatt I, Radke CJ. Deposition and thinning of the human tear film.

JColloid Interface Sci 1996;184(1):44-51.

66.Jones LW, Rahman S, Leech R, et al. Determination of Tear Meniscus Height using a Novel Method Based upon Optical Coherence Tomography. ARVO Annual Meeting Abstract Search and Program Planner 2003:2461.

67.Stuchell RN, Farris RL, Mandel ID. Basal and reflex human tear analysis: II. Chemical analysis: lactoferrin and lysozyme. Am J Ophthalmol 1981;88(8):858-862.

68.Da Dalt S, Moncada A, Priori R, et al. The lactoferrin tear test in the diagnosis of Sjogren’s syndrome. Eur J Ophthalmol 1996;6(3):284-286.

69.Lucca JA, Nunez JN, Farris RL. A comparison of diagnostic tests for keratoconjunctivitis sicca: Lactoplate, Schirmer, and tear osmolarity. CLAO J 1990;16(2): 109-112.

70.Yolton DP, Mende S, Harper A, Softing A. Association of dry eye signs and symptoms with tear lactoferrin concentration. J Am Optom Assoc 1991;62(3):217-223.

71.Gilbard JP, Farris RL, Santamaria J. Osmolarity of tear microvolumes in keratoconjunctivitis sicca. Arch Ophthalmol 1978;96:677-681.

72.Gilbard JP, Farris RL. Tear osmolarity and ocular surface disease in keratoconjunctivitis sicca. Arch Ophthalmol 1979;97:1642-1646.

73.Farris RL, Stuchell RN, Mandel ID. Tear osmolarity variation in the dry eye. Trans Am Ophthalmol Soc 1986;84:250-268.

74.Farris RL. Tear osmolarity—a new gold standard? Adv Exp Med Biol 1994;350:495-503.

75.Craig JP, Singh I, Tomlinson A, et al. The role of tear physiology in ocular surface temperature. Eye 2000;14(Pt 4):635-641.

76.Gilbard JP. Human tear film electrolyte concentrations in health and dry-eye disease. Int Ophthalmol Clin 1994;34(1):27-36.

77.Lee JB, Ryu CH, Kim J, et al. Comparison of tear secretion and tear film instability after photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg 2000;26(9):1326-1331.

78.Mathers WD, Dolney AM, Kraemer D. The effect of hormone replacement therapy on the symptoms and physiologic parameters of dry eye. Adv Exp Med Biol 2002;506:1017-1022.

79.White KM, Benjamin WJ, Hill RM. Human basic tear fluid osmolality. I. Importance of sample collection strategy. Acta Ophthalmol (Copenh) 1993;71(4):524-529.

80.White KM, Benjamin WJ, Hill RM. Human basic tear fluid osmolality. II. Importance of processing strategy. Acta Ophthalmol (Copenh) 1993;71(4): 530-538.

81.Wood JE, Nichols K, Nichols JJ. Tear volume, osmolarity, and ocular surface disease in patients with and without dry eye disease. Optom Vis Sci 2002;79(12s):253.

82.Feenstra RP, Tseng SC. What is actually stained by rose bengal? Arch Ophthalmol 1992; 110(7):984-993.

83.Koh S, Watanabe H, Hosohata J, et. al. Diagnosing dry eye using a blue-free barrier filter. Am J Ophthalmol 2003;136(3):513-519.

84.Foulks GN. Challenges and pitfalls in clinical trials of treatments for dry eye. The Ocular Surface 2003;1(1):20-30.

85.Golding TR, Efron N, Brennan NA. Soft lens lubricants and prelens tear film stability. Optom Vis Sci 1990;67(6):461-465.

86.Sutherland IW. Novel and established applications of microbial polysaccharides. Trends Biotechnol 1998;16:41-46.

87.Nakamura M, Hikida M, Nakano T, et al. Characterization of water retentive properties of hyaluronan. Cornea 1993;12(5):433-436.

88.Aragona P, Di Stefano G, Ferreri F, et al. Sodium hyaluronate eye drops of different osmolarity for the treatment of dry eye in Sjogren’s syndrome patients. Br J Ophthalmol 2002;86(8):879-884.

89.Noecker R. Effects of common ophthalmic preservatives on ocular health. Adv Ther 2001;18(5):205-215.

90.Bachman WG, Wilson G. Essential ions for maintenance of the corneal epithelial surface. Invest Ophthalmol Vis Sci 1985;26:1484-1488.

91.Caffery BE. Influence of diet on tear function. Optom Vis Sci 1991;68(1):58-72.

92.Prause JU. Treatment of keratoconjunctivitis sicca with Lacrisert. Scand J Rheumatol Suppl 1986;61:261-263.

93.Brennan NA, Efron N. Symptomatology of HEMA contact lens wear. Optom Vis Sci 1989;66(12):834-838.

94.Campbell R, Caroline P. Prism-sphere lens design reduces corneal staining. CL Spectrum 1994;9(4):56.

95.Lowther GE. The marginal dry eye and contact lens wear. ICLC 1988;15:333.

96.Shuley V, Collins M. Lid massage and symptoms of dryness in soft contact lens wearers. ICLC 1992;19(1):121-124.

97.Paugh JR, Knapp LL, Martinson JR, Hom MM. Meibomian therapy in problematic contact lens wear. Optom Vis Sci 1990;67(11):803-806.

98.Gilbard JP. Dry eye, blepharitis and chronic eye irritation: divide and conquer. J Ophthalmic Nurs Technol 1999;18(3):109-115.

99.Heiligenhaus A, Koch JM, Kemper D, et al. [Therapy of dry eye disorders]. Klin Monatsbl Augenheilkd 1994;204(3):162-168.

100.Sullivan DA, Sullivan BD, Evans JE, et al. Androgen deficiency, Meibomian gland dysfunction, and evaporative dry eye. Ann N Y Acad Sci 2002;966: 211-222.

101.Balaram M, Schaumberg DA, Dana MR. Efficacy and tolerability outcomes after punctal occlusion with silicone plugs in dry eye syndrome. Am J Ophthalmol 2001;131(1):30-36.

102.Tai MC, Cosar CB, Cohen EJ, et al. The clinical efficacy of silicone punctal plug therapy. Cornea 2002;21(2):135-139.

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103.Shalaby O, Rivas L, Rivas AI, et al. [Comparison of 2 lacrimal punctal occlusion methods]. Arch Soc Esp Oftalmol 2001;76(9):533-536.

104.Hutnik CM, Probst LE. Argon laser punctal therapy versus thermal cautery for the treatment of aqueous deficiency dry eye syndrome. Can J Ophthalmol 1998;33(7):365-372.

105.Friedlaender MH, Fox RI. Punctal occlusion for the treatment of dry eye. Adv Exp Med Biol 1998;438:1017-1020.

106.Murube J, Murube E. Treatment of dry eye by blocking the lacrimal canaliculi. Surv Ophthalmol 1996;40(6):463-480.

107.Kunert KS, Tisdale AS, Stern ME, et al. Analysis of topical cyclosporine treatment of patients with dry eye syndrome: effect on conjunctival lymphocytes. Arch Ophthalmol 2000;118(11):1489-1496.

108.Brignole F, Pisella PJ, De Saint JM, et al. Flow cytometric analysis of inflammatory markers in KCS: 6-month treatment with topical cyclosporin A [In Process Citation]. Invest Ophthalmol Vis Sci 2001;42(1):90-95.

109.Turner K, Pflugfelder SC, Ji Z, et al. Interleukin-6 levels in the conjunctival epithelium of patients with dry eye disease treated with cyclosporine ophthalmic

emulsion [In Process Citation]. Cornea 2000;19(4):492-496.

110Hom MM. Comparison of cyclosporin A versus a contact lens rewetter for contact lens intolerance: a pilot study. American Academy of Optometry, Tampa

2004.

111.Marsh P, Pflugfelder SC. Topical nonpreserved methylprednisolone therapy for keratoconjunctivitis sicca in Sjogren syndrome. Ophthalmology 1999;106(4): 811-816.

112.Karpecki PM, Solomon KD, Bucci FA, et al. Diminishing dryness. These preand postsurgical strategies combat dry eye throughout the LASIK experience. Optometric Management 2002[5]. 5-1-2002. BCI.

113.Morris S. Plugs, drugs and tears: a dry eye update, part two. Optometric Management 2002[10]. 10-15-2002. BCI.

114.Rolando M, Barabino S, Alongi S, Calabria G. Topical non-preserved diclofenac therapy for keratoconjunctivitis sicca. Adv Exp Med Biol 2002;506:1237-1240.

115.Timberlake GT, Doane MG, Bertera JH. Short-term, low-contrast visual acuity reduction associated with in vivo contact lens drying. Optom Vis Sci 1992;69(10):755-760.

116.Korb DR, Greiner JV, Glonek T, et al. Effect of periocular humidity on the tear film lipid layer. Cornea 1996;15(2):129-134.

117.Tsubota K, Goto E, Fujita H, et al. Treatment of dry eye by autologous serum application in Sjogren’s syndrome. Br J Ophthalmol 1999;83(4):390-395.

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sensitivity is also reduced, although simultaneous bifocals may show about the same reduction.11 Liability can be a problem if the practitioner fails to discuss and warn about the drawbacks of monovision in advance.12,13 Effects of suppression during long-term binocular vision are also potential problems.

E.Fitting monovision is virtually identical to fitting single-vision lenses. Both eyes are given the best lenses to maximize visual acuity.4,5

1.The near eye is usually the nondominant eye. The dominant eye is fitted with a distance lens. Studies have shown that choosing the dominant eye for distance does not necessarily produce better vision. Monovision visual acuity is not improved when eye dominancy is used as a guideline for selection.14

2.Occupational demands may dictate that the dominant eye be fitted for near. Sometimes, the left eye is chosen for distance. The rationale, disputed by some experts, is that while driving, the left eye is used for the side-view mirror.13

3.The sighting dominance test is the most common method of determining distance and near eyes. The patient is asked to produce a hole with his hands and place it up to one eye to view a distant target. The eye he or she chooses will be fitted as the distance eye.

4.The swinging-plus test can be used to select the distance and near eyes. The patient holds a +1.50 D lens over one eye while walking around the room and then repeats the procedure with the lens on the other eye. The eye most comfortable with the lens is designated as the near eye.15

5.Performing the near point of convergence test can help in determining the best eye for distance vision. The eye that loses fixation first can be chosen as the distance eye.

6.Computer dominance tests have shown to be effective. When compared against three other tests for dominance (sighting dominance, hand dominance, and perceived dominance), computer dominance testing correlated highly in determining the eye fitted at near in successful monovision subjects.16

F.Management of monovision may require several follow-up visits.

1.Adaptation time is usually 2 weeks, but some patients take up to 6 weeks. Normal adaptation includes hazy vision, eye strain, and variable suppression in the first weeks of wear. Adapting patients should be limited to nondemanding visual activities.12

closer look: Switching eye function (making the distance eye the near eye and the near eye the distance eye) can relieve even the vaguest symptoms.11

2.Common fitting problems associated with single-vision lenses (residual cylinder, dry eyes, wrong powers, and poor fit) should be ruled out first whenever there are problems.

3.Spectacle overcorrection is another option for monovision patients. Spectacles are specifically prescribed over contact lenses for driving or reading blur. The overcorrection can be done for distance, reading, or bifocally.

4.Adding minus to the near eye can relieve intermediate blur. Near vision will probably be compromised, however. If unsuccessful, modified monovision is an alternative strategy.

5.Low add power is sometimes insufficient to enable suppression. Increasing the add will be helpful, but it may bring the working reading distance too close.

6.High Dk lenses are preferred over thin low-water content lenses for low-plus monovision patients.17 More striae and folds were found for the thin low-water content lenses after 5 hours of daily wear.

II.Bifocal contact lenses are more complicated to fit but can offer many advantages over monovision. By definition, “bifocal” refers to a lens that has two powers and“multifocal,” to one with three or more powers. For simplicity, the terms will be used interchangeably throughout this section.

A.Selection involves careful screening that maximizes patient success for multifocals. The contraindications for lens wear are similar as for single vision lenses, but with additional considerations. Because the fitting process can be extensive, it is important to eliminate poor candidates as early as possible.

1.Personal characteristics: The most important factor in success is strong motivation to wear contact lenses. It is also important for the patient to understand and accept the potential visual limitations of bifocal contact lens correction. (The best candidates are those who are able to tolerate minor visual imperfections and whose occupations do not demand precise vision.) The patient must also be willing to return and pay for multiple office visits in order to achieve optimal fit, vision, and eye health.18

A closer look: The best bifocal contact lens candidates are those who are able to tolerate minor visual imperfections and whose occupations do not demand precise vision.

2.Physical characteristics: It is important to consider the ocular manifestations of advancing age. These include reduced tear quantity and quality; smaller pupil size; slower pupillary responsiveness; flaccid eyelids; decreased corneal sensitivity; and decreased best visual acuity due to cataract, macular degeneration, or other age-related changes.19,20 Regarding dry eye, it is not only more common with age, but it is induced by medications more likely to be taken by

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presbyopes. If the dry eye is mild to moderate and managed prior to the contact lens fitting, then lens wear can be successful. Severe dryeye patients, however, are poor candidates for contact lenses21 (see Chapter 21).

3.Prescription characteristics: Low refractive errors are not ideal for bifocal lens wearers. Patients with less than 1.00 D of hyperopia are poor candidates because they see “perfectly” without spectacles. Myopes with less than 1.25 D are accustomed to seeing without any correction for near. Lower success rates have also been found with higher add powers, high sensitivity to small lens changes during refraction, and cylinder greater than 0.75 D in soft bifocal lens wearers.

B.Adaptation can take many weeks. Within 3 to 4 weeks, the patient and practitioner should be able to decide whether to continue with bifocal lenses. Wearing the lenses for 8 to 10 weeks is a good sign because few patients discontinue after that time. Because of the longer, more difficult

adaptation period, it is important that the patient is motivated. The patient should be informed that there may be several lens changes. A follow-up visit should be scheduled about 1 week after dispensing each refit.

A closer look: Remember that even small, 0.25 D changes are significant to these patients.22

C.Bifocal fitting considerations are sometimes different than those for single-vision lenses.

1.It is important to apply trial lenses for bifocal contact lens fitting. Begin by following the manufacturer’s recommendations for initial lens selection. The manufacturers have collected data from thousands of successful patients, and their fitting guides are based upon this knowledge.23 Of course, it is not practical to own trial lenses for every bifocal that is available. Many laboratories have a fair exchange policy or will loan the practitioner a needed trial lens.

2.Wait at least 15 minutes for the lenses to settle into place. Use loose trial lenses and overrefract each eye separately. The prescription should then be refined with both eyes open for bifocal contact lenses. Because many designs depend on pupil size, understand a patient’s most common lighting environments. Overrefract and demonstrate the lenses in these illumination conditions.

3.Auxiliary glasses are sometimes needed for extremely small print. Some authors tell the patient that contact lenses will be adequate at least 80% of the time.1 A good way to communicate this is that the lenses will“meet most visual needs most of the time.”24 It is important to understand that some patients cannot be fit successfully with presbyopic (bifocal or monovision) contact lenses.25

A closer look: Be positive. The confidence that the practitioner has in prescribing presbyopic contact lenses is the key to motivating and instilling confidence in the patient.26,27

D.The use of modified monovision may determine the difference between success and failure with bifocal contact lenses. By definition, this entails emphasizing one eye for distance and one eye for near by utilizing bifocal contact lenses in one or both eyes. (Some sources define the latter as the modified bifocal approach.)23 As far back as 1985, studies showed modified monovision to be as subjectively preferable to patients as conventional monovision. There are several variations of modified monovision.

1.Use two bifocal lenses of the same design and prescribe the maximum lens power accepted by the patient: minus power (without over-minusing) for the distance eye and plus power (without compromising working distance) for the near eye.

2.Use two bifocal lenses of the same design and prescribe unequal add powers. Frequently, a lower add on the distance eye improves distance vision; the full add can be prescribed for the near eye to maximize near acuity.

3.Prescribe a single vision lens for one eye and a bifocal lens for the other eye.1 This may be beneficial for patients who require acute vision at one distance, such as truck drivers or bookkeepers. This option is also useful for monovision patients who complain of intermediate blur.

4.Use two different designs of bifocal lenses. A better-performing distance bifocal is used for the distance, dominant eye, and a better per-

forming near lens is used for the near, nondominant eye. For example, fit a Frequency 55 Multifocal Distance (D) lens (CooperVision, Fairport, NY) for distance and a Sunsoft Additions lens (CooperVision) for near.

III.Gas-permeable bifocals usually provide better optics than do soft bifocals. A. Selection: GP versus soft lenses

Selection for GP bifocal lenses entails many factors.28 Prior experience with GP lenses is an advantage. With today’s designs, however, even first-time lens wearers enjoy great success with this modality. Fulltime wearers can wear either GP or soft; for part-time wearers, soft are preferred. Soft bifocal trial lenses can be dispensed directly from a fitting inventory. Patients requiring high adds do best with a translating GP design. Lastly, astigmatic presbyopes benefit from the optics of GP lenses.

A closer look: The best contact lens choice for a newly presbyopic GP lens wearer is a GP bifocal.

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B.GP bifocal selection

1.The location of the corneal apex is an important selection factor with GP bifocals. For superior decentration of the apex relative to the pupil, aspheric lenses fitted with lid attachment, such as Essential GP (Blanchard Contact Lens, Manchester, NH),

Essential Xtra, Boston Multivision (Bausch & Lomb, Rochester, NY), and LifeStyle GP (Lifestyle GP Co., Sarasota, FL)—or translating designs—are better than aspherics that require perfect centration.

2.Pupil size should be considered. Small pupils work best with aspherics. Very tiny pupils, however, may prevent maximum near correction in a center distance design. Very large pupils, greater than 6 mm in diameter, can experience flare and poor visual acuity with both concentrics and aspherics.29 One approach is to fit pupils greater than 5 mm with translating lenses and less than 5 mm with aspheric lenses.30

3.For those who work on computers, a simultaneous design is appropriate.28 In general, if the patient spends more than 30% of the day on the computer, a concentric or aspheric is recommended. An aspheric is generally preferred because of its correction of intermediate distances.

4.For patients who work at an intermediate distance, at “arm’s length,” a simultaneous design is appropriate. These patients include beauticians, electricians, plumbers, and mechanics.

5.Lower-lid tangency to the limbus strongly affects a translating design.28 If the lower lid is below the limbus, a simultaneous design is better than an alternating lens. Translation depends partially on lower lid contact to enable movement on downgaze.

6.In the past, alternating designs were chosen for high add powers. Because both the distance and near portions of an alternating lens are spherical, the optics are crisp. Another advantage is the availability of almost any add power. In addition, pupil size and the technologic limitations do not play as large of a role as with simultaneous vision lenses. But technology with aspheric multifocals is improving, and many of today’s designs can be fit successfully for advanced presbyopes.31

C.Simultaneous designs present the distance, intermediate, and near corrections to the retina at the same time. The patient must involuntarily select the clearer image to view. If the patient is looking at near, the out- of-focus distance image must be suppressed, and when looking far away, the near image must be suppressed. Visual compromise is normal and adaptation is needed.

1.Usability in all fields of gaze is the most noted advantage of simultaneous designs. Patients appreciate the ease with which near objects can be viewed from any position.32

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by grinding two different curvatures on either the front or back surface. The polymethyl methacrylate (PMMA) deCarle bifocal has a centerdistance zone with the two curves ground onto the back surface. The

Mandell Seamless (Con-Cise, San Leandro, CA) and Front Surface

(Danker Labs, Sarasota, FL) are also center-distance concentrics but with the optics on the front surface.

E.Aspheric lenses can be either center-near or center-distance. E values (eccentricity values) are often used to specify different aspheric curvatures. Most aspheric lenses for presbyopia have e values of greater than

1.0.A moderate-to-high degree of flattening is required to induce enough add power in the periphery.33

1.Back aspherics are center distance. The power progressively changes from center to midperiphery. Better distance vision is a noted advantage over front aspherics. Lower add powers and poor centration with decentered corneal apexes are limitations. For decentration problems, consider front aspherics with spherical base curves. Back aspheric lenses are Unilens (Unilens Corp USA, Largo, FL); the VFL series (Conforma Contact Lenses, Norfolk, VA); and V/X Aspheric (Aero-GBF Contact Lenses, Kalamazoo, MI).

2.Front aspherics are center near. Near vision can be better with front aspherics than with back aspherics. An example is Asphero-F (Danker).

3.Most aspherics are fit steeper than flat K (Fig. 22-2). Base curves can be adjusted to achieve the best possible correction. Steepen the base curve if the lens is too flat or moves temporally. Flatten the base curve if the lens is too steep or moves nasally.34 Centration can also be enhanced by increasing the overall diameter of the lens. If excessive superior lid attachment exists, decrease overall lens diameter or thin the edge.

4.Patients sight through the peripheral areas of the aspheric lens when they look down. If they do not, they have insufficient near vision with a center distance design. If the lens moves too much with the eye on downgaze, a steeper base curve or larger diameter can be used.34

FIGURE 22-2 Initial base curves of rigid aspherics. Aspheric lenses are usually fitted steeper than K. The initial base curve choices for various aspheric bifocals are shown in relative order from flat (on K) on the left to steep on the right. (Adapted from DW Hansen. For more natural vision try aspheric rigid gas-permeable multifocals. CL Spectrum 1995;10[6]:15.)

FIGURE 22-5 Initial size and height. After taking measurements of the eye, the segment height and vertical and horizontal diameters can be calculated by using the formulas shown. The horizontal and vertical diameters are different if truncation is ordered. Vertical lens size = lower lid (LL) to superior limbus − 2 mm; segment height = lower lid (LL) to visual axis − 1.3 mm; horizontal lens size = add 0.4 mm to vertical.

drop quickly into position when looking straight ahead. When looking down, the lens should move up, covering part of the upper sclera. The lens position can be observed by gently lifting the upper lid while the patient is looking down.

2.Discomfort is a major factor in discontinuation. Translating designs are often thick and heavy.45 A patient may have discomfort with a translating GP bifocal because of the thickness and prism required. Patients with extrasensitive lids and poor adapters are not ideal candidates for a Tangent Streak Bifocal. A simultaneousvision lens (especially aspheric) or monovision would provide better comfort.

3.Three and 9 o’clock staining or peripheral corneal desiccation (PCD), is another disadvantage of the thick and heavy translating designs. Korb and Exford theorized that PCD was caused by a lid gap.46 This occurs when the edge of the lens holds the lid away from the cornea. Lenses can be modified to enhance wetting and decrease staining. Solutions include thinning the edges, changing the diameter, or facilitating proper blinking.

4.Encyclorotation can cause poor near vision and is influenced by lid movement. The upper lid moves up and down like a windshield wiper.47 The lower lid moves in a horizontal, transverse motion. As the upper lid moves downward, the lower lid moves toward the medial canthus. This lid action results in nasal rotation of a bifocal lens on blink. Rotation increases on downgaze.39

a.Changing the prism axis helps achieve better lens orientation by adjusting the amount of rotation. This works well when the rotation is stable but not with an unstable lens. Increasing the prism does produce benefits with an unstable lens.41 Some practitioners automatically assume there will be encyclorotation. Depending on the amount of rotation, a suggested adjusted axis would be 100 to 105 degrees for the right lens and 75 to 80 degrees for the left lens48 (Fig. 22-6). Both adjusted axes

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Changing prism axis. Rotation of 15 degrees in each eye is shown above. The dotted line indicates a prism axis of 90 degrees. The solid lines are 90-degree reference lines. The prism axes have rotated 15 degrees nasal. To correct for this, assume that the next lens ordered will also rest at 15 degrees rotation. For 15 degrees nasal rotation, a prism axis of 105 degrees for the right eye and 75 degrees for the left eye should be ordered. Adjusted prism axes are shown below. The dotted lines are the adjusted prism axes. The truncation shows that the lenses are no longer rotating with the adjusted axes.

are 10 to 15 degrees base in. Changing the base apex changes the location of the prism apex (the thinnest part of the lens).39 When placed at the proper axis, the base apex can be used to orient the lens in the desired location. The manufacturer suggests changing the base apex by no more than 20 degrees.49,50

A closer look: Order the prism axis in the same direction as the excessive rotation.51

b.Reduction of the diameter can decrease rotation on downgaze if lid capture is the cause.39 Because of the upper lid forces, lessening the lid contact can help stabilize the lens.

c.Increasing the prism can help stabilize rotation.52 More prism especially will steady a fluctuating rotation.

d.Changing truncation orientation will stabilize the lens whenever the lower lid is causing the rotation. Modifying the truncation can better fit an oblique lid angle or lid slope (Fig. 22-7).

5.Inadequate translation causes poor near vision. It occurs for a number of reasons.52 The lens may be too large and unable to move upward; when this occurs, excessive superior lens impingement can be seen on downgaze with a fluorescein pattern.49 This problem can be addressed by reducing the diameter. When the lower lid is not catching the lower lens edge, widening the truncation may help. Little or no movement on blink also results in poor translation. Flattening the lens is necessary if the fit is too tight; a steep lens resists the lower lid push. An optimal interaction between upper lid and lens edge is the key to adequate translation.

6.Lateral decentration of lenses, especially on downgaze, results in poor near vision. Macalister and Woods showed with video that increasing the size of the lens and steepening it are the most useful strategies. Of the two, increasing size is better than steepening the lens. Making the lens both larger and steeper is the most effective, however.39

7.Rotation and decentration together commonly cause poor near vision. Macalister and Woods showed that increasing lens diameter reduces rotation and provides coverage for a lateral decentration. If a stable rotation is the only problem, changing the prism axis is better than increasing lens diameter.39

8.Poor distance vision occurs when the pupil is not within the distance zone on primary gaze. Close observations can determine the cause.

a.If the segment height is too high, it can be lowered by truncation. Whenever possible, aim high when ordering segment heights.53 Segment heights are easier to lower (with modification) than raise.

FIGURE 22-7 Changing truncation. If the lower lid is at an oblique angle and causes the lens to rotate, the truncation can be changed to help stabilize the lens. On the left, a lens is rotated because of the obliquely aligned lower lid. The dotted line indicates the prism axis of the lens at 90 degrees. On the right, truncation was changed to match the lower lid, allowing the lens to stabilize in the proper position.

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b.A lens riding too high must be lowered. Remember that the ideal fit is an inferiorly positioning lens. A lens picked up far too superiorly with the blink will result in fluctuating distance vision. Increasing the prism by 0.50 prism diopters or thinning the upper edge of the lens can minimize the effects of the upper eyelid.27 If there is no upper lid contact, flatten the periphery, base curve, or both.

A closer look: Consider the Essential GP if the upper lid holds the lens too high.

c.A slow recovery after a blink is called lens lifting or slow return. The lens drops too slowly into position, causing visual distress as the segment crosses the pupil. Increasing the prism makes the lens drops faster.41 A smaller lens also has a faster return.39

d.Flare at night can be caused by a dilated pupil looking through either the segment or the lens edge. Decreasing the segment height solves the former; increasing the lens size solves the latter.

9.Variable vision can be created by excessive movement of a flat lens. Make certain there is an alignment fit. If the fit is already aligned, check for unsteady rotation and consider increasing prism.49

10.Studying reorders and lens modifications will improve Tangent Streak Bifocal problem-solving. A study by Remba carefully reported the treatment strategies needed for refitting.40

a.The most common reorder was for increased prism to remedy lens lifting and unsteady rotation (Fig. 22-8).

b.Lens modifications were most frequently performed on the truncation (Fig. 22-9). It was either reshaped to enable consistent translation or recut to lower segment heights. The other most common modification was thinning or tapering the edges for comfort. Modification plays a key role in fitting the Tangent Streak Bifocal.

H.The X-Cel Solution is a crescent-shaped alternating bifocal. Its unique one piece “no jump” design eliminates the shifting of the image that occurs with many designs of alternating lenses. This happens when the patient switches between near and distance vision (Fig. 22-10).

I.The Solitaire II bifocal is a segmented translating lens with prism made by Tru-Form Optics (Euless, TX). It may be ordered with or without truncation. In addition, it incorporates a small aspheric midrange between distinct distance and near zones on the front surface of the lens. This represents an improvement over the original Solitaire lens. In one study, 83% of the patients were satisfied with the original Solitaire, but some dropped out because of the lack of intermediate vision.54

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J.The Tangent Streak Trifocal (Fused Kontacts) follows the same design guidelines as the Tangent Streak Bifocal. The difference is a 1-mm-wide intermediate zone located between the distance and near areas. Of 16 patients dissatisfied with the Tangent Streak Bifocal, 12 were refitted successfully with the Tangent Streak Trifocal.55

K.New technology is producing lenses with both simultaneous and translating features. Several examples are listed below.

L.The PresbyLite II (Lens Dynamics, Golden, CO) is a translating bifocal design with a “wedge”sector near zone and a small “triangle”intermediate zone. The intermediate zone is optimally fitted within the pupil, resulting in a simultaneous alternating system. A large distance viewing area allows up to 30 degrees of nasal rotation. The thin design is not truncated, but ballasted with 1.5 D of prism.

M.The LifeStyle GP lens is a lid-attachment aspheric lens that uses translation to see through the distance, intermediate, and near zones. Patients whose lenses ride high with a lot of lid tension do well with this lens.56 With-the-rule astigmats and prior gas-permeable lens wearers are ideal candidates.43 Computer users are also successful with this lens. Those

with pupil sizes of 5 mm diameter or more may be marginal candidates, however.45 The lens is considered to have a +1.75 add.56 There are two diameters, 9.0 and 9.5 mm. The 9.0-mm diameter is the initial lens of choice.57

1.The “equivalent base curve” or secondary aspheric curve is the 1.2-mm-wide fitting curve.57 The goal is a midperipheral alignment fit. An equivalent base curve equal to or 0.1 mm flatter than flat K is the starting point.34 The lens is designed to ride high under the upper lid and translate on downgaze (Fig. 22-11).

2.Inferior decentration can be remedied by changing to a largerdiameter lens with a flatter base curve.

3.A superiorly decentered lens may result in blurred distance vision. A decentered lens can make the patient view through the near area.57 The diameter can be decreased to 9.0 mm (if initially 9.5 mm) and slightly steepened.

4.Poor translation into reading position may be due to a steep lens. The reading vision will appear blurred.57 The lens should be flattened.

N.The Essential GP and Essential Xtra are translating aspheric lenses. In primary gaze, the patient looks through the central portion of the lens. On downgaze, the Essential translates upward, enabling use of the intermediate and near optics of the lens. This minimizes image degradation as compared with a purely simultaneous vision lens. In addition, perfect centration is not critical and the design is not limited by varying pupil size.

Another unique feature is Blanchard’s proprietary “S Form” technology, which provides a true aspheric back surface where up to +2.75 D of add can be compressed, as opposed to traditional computer numerically controlled lathes that simulate asphericity with a series of spherical cuts. The spaces

FIGURE 22-11 The Lifestyle GP (Lifestyle GP Company, Sarasota, FL) has a central prescription zone for distance and near. The darker area represents distance power progressing outward to near power. The surrounding fitting zone or equivalent base curve on the back surface is shown below.

or“risers” between these cuts increase the area over which the add is contained, resulting in less add, especially for smaller pupils and lenses not designed to translate.58 In a study of a wide range of patient ages and prescriptions, 100% of patients dispensed the Essential GP remained in the lens after 1 month of wear and demonstrated good acuity at all distances.59

1.The lens can be ordered in three add powers: Series I, up to +1.50; Series II, +1.50 to +2.25; and Series III, +2.50 and up.

2.The Essential Xtra incorporates S-Form posterior aspheric geometry that is steeper throughout the entire base curve. This creates a posterior surface in the paracentral area of lens which has less bearing on the cornea, and should result in less corneal flattening (sometimes produced with back aspheric designs). This also lowers edge lift, which increases comfort and minimizes unwanted lid action on the lens. The aspheric power change also begins farther from the axial center of the lens. This creates a larger distance optic zone, which means less impact of the add on distance vision.60

O.The CSA Enhancement is a Concentric S-Form Add applied to the front surface of an Essential or Essential Xtra lens. The combination of poste-

rior and anterior add creates a segmented translating aspheric multifocal. From +.50 to +2.00 D of additional power can be placed in an annulus on the front surface. Because the power is 360 degrees, no prism or truncation is needed.

P.The Essential Solution (X-Cel Contacts) is a segmented translating aspheric multifocal combining the Essential GP aspheric back surface and the X-Cel Solution segmented front surface.

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Q.ContinuVu (Essilor Laboratories of America, Dallas, TX) is a progressiveadd multifocal lens that eliminates the need for prism or truncation. The

lens is designed to simulate the natural progressive design found in glasses. Prescription range is custom made with add power to +3.00 D. Available diameters are 9.3 to 10.3 mm.

R.EZEyes (ABBA Optical, Inc., Stone Mountain, GA) is a hybrid multifocal that includes a progressive aspheric posterior surface combined with a segmented anterior surface. The lens also has an aspheric transition zone for added visual and wearing comfort. The segmented anterior surface

gives additional near power to the aspheric lens. Patients who require more than a +1.75 D add can benefit from the higher add powers. Prescription range is up to +4.00 D add in 0.25 D steps. Available diameters are normally about 9.6 mm, but the lenses can be customized.

IV. Soft lens bifocals have many designs similar to GP bifocals.

A.Simultaneous vision in soft lenses is similar to vision with GP bifocals in that both the distance and near vision—both distance and near bundles of light—are on the retina at the same time. The patient must learn to selectively suppress the unfocused image while looking at the properly focused image.

1.Superior distance stereoacuity for simultaneous designs is the major performance advantage over monovision.5 Being able to see near work in all fields of gaze is another advantage.

2.Reduction of visual acuity related to decentration and changes in illumination is the major drawback. Simultaneous bifocals give a reduction of scotopic (dim illumination) vision.61 There are two types of simultaneous bifocals: concentric and aspheric.

B.Concentric simultaneous bifocals have a distance and near zone within the pupil. Concentric bifocals are available as center-distance or center-near.

1.The zone-check technique is used to determine the location of the concentric zones while the lenses are on the eye. A +4.00 D trial lens

is hand-held over the eye while being viewed with a direct ophthalmoscope. The +4.00 D lens magnifies the reflex so that the zones can be seen within the pupil.

2.Pupil size plays an important role with center-near designs. At near, the miosis associated with the near reflex helps to clear the near images. The unfocused distance rays are blocked, leaving the focused near rays of light.

3.The LL-Bifocal by Lombart Lenses in Largo, FL (formerly the Bisoft by CIBA Vision, Duluth, GA) is one of the oldest centerdistance concentric designs. Because it is concentric, there are theoretically higher add powers available than with aspherics.11 In one study, however, a comparison with a pair of concentric distance lenses was not made because the pilot acceptance rate was too low (5%).22

4.Vistakon (Jacksonville, FL) has made various improvements to the original center-distance design. The Acuvue Bifocal was the first 2-week disposable bifocal lens. It is manufactured in 58% water content material with an ultraviolet (UV) blocker and an inversion indicator. The design features five alternating zones with a center distance zone. This enables better distance vision in dim illumination (dilated pupil) than a traditional center-distance concentric lens. It also helps negate the effect of pupil size. A modified bifocal fitting approach with this lens helps preserve good distance vision and provides intermediate acuity.23

5.The Lifestyle MV2 (Lifestyle) is a monthly replacement lens that utilizes a modified monovision approach. The lenses are similar to single-vision lenses, except they have a spherical central intermedi-

ate zone. One lens has distance power in the periphery with an additional +0.50 D centrally; the other lens has near power in the periphery with an additional −1.25 D centrally.

C.Aspheric soft bifocals can be either center-distance or center-near. One study compared monovision with an aspheric bifocal and found that 80% preferred the aspheric.62 Legacy back aspheric soft bifocals, such as Hydrocurve II (CIBA Vision) and VX (Aero-GBF), have distance power in the center.63 Higher add powers are a common goal among bifocal aspheric manufacturers. The inherent limitation of aspheric designs is lower add powers. Greater eccentricity results in higher add powers for Hydrocurve II and VX lenses than some of their obsolete peers. However, center-distance aspheric lenses are limited by the fact that, as the eye focuses at near, the pupil constricts. This makes it difficult to utilize the near power located in the midperiphery of the lens. As a result, few of these lens designs remain on the market today.

1.The VX has an eccentricity value of 1.6 and is hyperboloidal in the central section. The distance power is usually −0.25 to −0.50 higher because of the high eccentricity.64

2.Special considerations should be kept in mind with aspheric soft bifocals. Pushing the plus is highly recommended for many of these lens designs because add power is usually limited in aspherics. The more plus prescribed, the better for near. Some manufacturers recommend pushing the plus at distance to an acceptable visual acuity of 20/25. Sometimes more minus at distance is necessary, however. The visual axis can be located nasal to the geometric center of the pupil and contact lens. This anatomic variation forces the patient to sight through additional plus, and more minus is needed to compensate.

a.Hyperopes tend to have better success with aspherics than do myopes. Additional plus of a progressive add power is tolerated well because these patients may have a small amount of latent hyperopia.

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b.Low-add monovision patients needing better near stereopsis may be good candidates for aspheric bifocals.63

c.Centration and pupillary sizes are concerns for aspherics, as with other simultaneous lenses. The effects of decentration on an aspheric were calculated and graphed by Charman et al.65,66 Use of centered lenses with smaller pupils obstructs the light rays that pass through the peripheral regions. Decentered lenses and larger pupils do not block the peripheral distortions, and vision is affected.

D.Front aspheric lenses, primarily center-near designs, make more sense than center-distance designs for optimizing near vision. Because the pupil constricts when reading, center-near aspherics often provide better close vision, and as a result, there are more of these lens designs on the market.

1.The Unilens 38 is one of the original yearly replacement center-near lenses.67 It is now available in a planned replacement program. The initial diagnostic power is determined by adding the spectacle

sphere power plus one-half the add. Low-to-moderate adds to +1.50 D are the best candidates for the Unilens.68 The Unilens

Softsite, another center near aspheric, can provide add powers from +1.75 to +2.50.

2.Newer designs provide excellent optics while incorporating better materials and a shorter wearing schedule. Quattro (Blanchard) and Sunsoft Additions (Ocular Sciences, Inc./CooperVision, Concord,

CA) are quarterly replacement lenses. The former, which utilizes Blanchard’s proprietary S-Form technology to provide up to +2.25 D of add, is fitted using the modified monovision philosophy. The latter, made of 55% methafilcon A, comes in three add powers (Fig. 22-12).

3.Focus Progressives (CIBA Vision), introduced in 55% water vifilcon A, can be fit for 1-week extended wear or for between 2 and 4 weeks of daily wear. The initial power is chosen by adding half of the add to the vertexed spherical equivalent spectacle refraction. The add is highly concentrated in a small near zone to maximize distance

vision. There is just one add power, reported by CIBA Vision to be up to +3.00 D. This can serve as an advantage in that the lens either works or it doesn’t.23 An additional advantage is the availability of the design in 69% water nelfilcon as the first daily disposable multifocal lens.

4.The SofLens Multifocal (Bausch & Lomb, Rochester, NY) is marketed as a 2-week replacement lens. It comes in two base curves and two add powers.

E.Several designs combine aspheric and concentric features.

1.The Frequency 55 Multifocal and the UltraVUE 2000 DW

(CooperVision) are uniquely designed lenses that fit the dominant eye with a“D” lens and the nondominant eye with an“N” lens. The

FIGURE 22-12 The Ocular Sciences (Concord, CA) Sunsoft Additions multifocal has near power in the center and changes to distance power in the periphery. The dark areas represent near power.

D lenses have a spherical central zone for distance surrounded by an aspheric intermediate-to-near zone. The N design has the near power centrally surrounded by an aspheric intermediate-to-distance ring. The Frequency 55 goes one step further, encircling the aspheric zones with spherical near and distance annular rings, respectively. Both lenses are manufactured in 55% methafilcon A for frequent replacement (monthly—Frequency 55 and quarterly—UltraVUE 2000 DW). The versatility of these lens designs enables them to fit a wide variety of patients, including full presbyopes.23 Failed monovision patients, however, may not be optimal candidates.

2.Proclear Multifocal (CooperVision) has the same design as the Frequency 55 Multifocal. The difference is the Proclear material (omafilcon A). The manufacturer claims the phosphorylcholine (PC) molecules in the polymer helps to attract and bind water to their surface.

3.Simulvue 38, by Unilens, is a center-near concentric. Simulvue has an aspheric transition between the center-near and distance

zones that reduces secondary visual images. The lens is prescribed for patients with adds up to +3.00.69

F.Soft toric multifocals are available in center-distance or center-near designs; the optics and options are better than ever.

1.The UCL Multifocal Toric (United Contact Lens, Everett, WA) is an

aspheric, center-distance lens with the ability to correct 3 D of astigmatism and provide +3.00 D of add.

2.Westcon Contact Lens (Grand Junction, CO) manufactures two toric center-near bifocals: a concentric (Horizon 55 Bi-Con Toric) and an

aspheric (Horizon Progressive). Both provide cylinder correction of up to 5 D; the concentric can be ordered up to a +4.00 add; the aspheric corrects up to +3.00.

3.The Essential Soft Toric Multifocal (Blanchard) has a front aspheric, center-near design with posterior toricity and a double

slab-off for stability. With use of a slight modified monovision approach, effective adds up to +2.50 can be achieved.

FIGURE 22-14 The echelettes in a magnified view. A small portion of the back surface is pictured. The groove-like echelettes are located on the back surface and fill with tears. The change in indices and the shape of the echelettes diffract the light.

completely incorporated into the lens. However, lens awareness increases with lens instability; patients with loose lids, lower lid below limbus, and small apertures are not good candidates for the Triton.74

A closer look: Refitting failed bifocal lenses with monovision can be quite effective.22

V.The optical mixture describes the type of vision a contact lens bifocal lens patient experiences. Because of the many variability factors, a patient does not have pure bifocal vision at all times. Whether intentional or not, some form of modified monovision is taking place at some times. Realistically, most bifocal patients have an optical mixture of monovision, simultaneous, and alternating vision. The optical results are located somewhere on the “face of the pyramid” shown in Fig. 22-15.75

VI. Best overall bifocal vision is usually achieved with rigid gas-permeable translating or alternating designs. Unfortunately, bifocal contact lenses are perceived by many practitioners as difficult to fit. Much of the contact lens literature is devoted to stepwise approaches to fitting. A video diagnostic fit may be the best way to learn how to fit alternating designs. Use of additional

494 SPECIAL TOPICS

Alternating Vision

FIGURE 22-15 Optical mixture. Vision with bifocal contact lenses is usually somewhere between monovision, simultaneous, or alternating vision. The type of vision is usually located somewhere on the face of the pyramid. (Adapted from WJ Benjamin, IM Borish. Presbyopia and the influence of aging on prescription of contact lenses. In: Guillon M, Ruben CM, eds, Contact Lens Practice. London: Chapman & Hall, 1994:828.)

prism, as small as one-quarter diopter, can make a large difference in enhancing rigid alternating lens performance. Other key points demonstrated are the importance of an alignment fit and distinguishing between a light blink and a full blink.

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