Ординатура / Офтальмология / Английские материалы / Contact Lenses in Ophthalmic Practice_Mannis, Zadnik. Coral-Ghanem, Kara-Jose_2003

240 C. Coral-Ghanem and M.D. Bailey

6.Discard contact lenses after swimming when the risk of infection is the greatest.

7.Have a pair of glasses in case the contact lenses are lost.

In the ocean:

1.Close the eyes underwater. After surfacing, blink rapidly to remove water from the eye. When contact lenses are in contact with salt water, they do not fit as tightly.

2.Have glasses available in case the contact lenses are lost.

56.How does one avoid contamination of the contact lenses with cosmetics or hair care products?

Cosmetics can deposit on the contact lenses and may cause allergic reactions; they can form a greasy film on the contact lens, obscuring vision and thereby reducing wearing time and comfort. We recommend the following practices:

1.Use unscented and hypoallergenic cosmetics.

2.Use cosmetics made by established companies with a record of quality control.

3.Wash hands thoroughly to remove any residue prior to handling of the contact lenses. Oily cosmetics are difficult to remove from the fingers and from the contact lens.

4.Apply cosmetics when the contact lens is already in place to reduce the risk of contaminating the lens. Presbyopic patients, however, may find it easier to apply makeup without a contact lens. They may wish to place the lens in position after cosmetic application.

5.Avoid iridescent eye shadow, because the particles may get into the eye and remain under the contact lens. Compact eye shadows are preferred over liquid, oils, or creams, which are more difficult to remove from the contact lens. Use eye shadow in moderate quantities only. Facial powder in a compact is preferred over loose powder and should be applied with care. Remove any excess powder from around the eyes.

6.Apply eyeliner with an attempt to avoid any obstruction of the meibomian glands. Otherwise, this may cause blepharitis, hordeola, or chalazia. For the contact lens wearer, pencil liners are better than liquids or pastes. Avoid using saliva to moisten the brush or cosmetic.

7.Wash mascara brushes frequently and change them every 3 months. Mascara brushes should not be shared. Mascara is a combination of greasy pigment, wax, and chemical preservatives, generally in a liquid base, which is an optimal medium for the growth of microorganisms.

8.Apply mascara lightly and distant from the base of the lashes. Never use a sharp object to separate the lashes. Avoid waterproof mascara and mascara designed to elongate the lashes. These con-

21. Maintenance and Handling of Contact Lenses 241

tain nylon and rayon fibers that are dry and may loosen, entering the eye. The tears carry these fibers under the contact lens, where they can irritate or cause injury to the cornea. Water-resistant mascara (not waterproof) is recommended for the contact lens user because it is soluble in water and may be removed easily with emulsifying agents. The waterproof mascara, however, requires using oily products to remove it. If these oily products remain on the lid margin, they may contaminate the contact lens, even after thorough rinsing.

9.Close and tightly cap the cosmetics immediately after use to avoid contamination. Do not expose cosmetics to heat.

10.Remove the contact lens before removing makeup.

11.When applying cream to the lids at night, take care not to touch the lashes, and preferably, after 20 minutes, remove the excess cream with a tissue. Cream can penetrate the eye during the night, entering the tear film and causing decreased vision in addition to burning and pain the next day.

12.Aerosol solutions and their sprays should be used prior to the insertion of the contact lens. If it is necessary to apply hair spray while wearing a contact lens, the eyes should be closed, and the place where the spray was applied should be left quickly, because the aerosol remains in the air for a period of time.

13.Avoid wearing contact lenses during hair coloring or chemical treatments to the hair.

14.Avoid the use of cosmetics and contact lenses in eyes that are red, inflamed, or infected.

References

1.Driebe WT Jr. Contact lens cleaning and disinfection. In: Kastl PR, ed. Contact Lenses. The CLAO Guide to Basic Science and Clinical Practice, vol 2. Dubuque, IA: Kendall/Hant Publishing, 1995:237–262.

2.Caroline PJ, Obin JB, Gindi JJ, et al. Microscopic and elemental analysis of deposits on extended wear soft contact lenses. CLAO J. 1985;311–316.

3.Kleist FD. Appearance and nature of hydrophilic contact lens deposits. II. Inorganic deposits. Int Contact Lens Clin. 1979;6:177–186.

4.Carney LG, Hill RM. pH profiles: part 1—one pH, or many? J Am Optom Assoc. 1975;46:1143–1145.

5.Brawner L, Essop DG. A review of contact lens solutions. Contacto. 1962;6: 49–51.

6.Burstein NL. Preservative cytotoxic threshold for benzalkonium chloride and chlorhexidine digluconate in cat and rabbit corneas. Invest Ophthalmol Vis Sci. 1980;19:308–313.

7.Shih K, Sibley MJ. The microbiological benefit of cleaning and rinsing contact lenses. Int Contact Lens Clin. 1985;12:234–242.

8.Patrinely JR, Wilhelmus KR, Rubin JM, Key JE. Bacterial keratitis associated with extended wear soft contact lenses. CLAO J. 1985;11:234–236.

9.Mayo MS, Schiltzer RL, Ward MA, Wilson LA, Ahearn DG. Association of Pseudomonas and Serratia corneal ulcers with use of contaminated solutions. J Clin Microbiol. 1987;25:1398–1400.

10.Donzis PB, Mondino BJ, Weismann BA. Bacillus keratitis associated with contaminated contact lens care systems. Am J Ophthamol. 1988;105:195–197.

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11.Penley CA, Willis SW, Sickler SG. Comparative antimicrobial efficacy of soft and rigid gas-permeable contact lens solutions against Acanthamoeba. CLAO J. 1989;15:257–260.

12.Liedel KK, Begley CG. The effectiveness of soft contact lens disinfection systems against Acanthamoeba on the lens surface. J Am Optom Assoc. 1996; 67:135–142.

13.Soni OS, Horner DG, Ross J. Ocular response to lens care systems in adolescent soft contact lens wearers. Optom Vis Sci. 1996;73:70–85.

14.Erickson OF. Drug influences on lacrimal lysozyme production. Stanford Med Bull. 1960;18:34.

15.Crandall DC, Leopold IH. The influence of systemic drugs on tear constituents. Ophthalmology. 1979;86:115.

16.Fraunfelder FT, Baico JM, Meyer SM. Adverse ocular reactions possibly associated with isotretinoin. Am J Ophthalmol. 1985;100:534.

17.Ensink BW, Van Voorst Vader PC. Ophthalmological side effects of 13- cis-retinoic therapy. Br J Dermatol. 1983;108:637.

18.Scott D. Another beta blocker causing eye problems. Br Med J. 1977;2:1221.

19.Mackie IA, Seal DV, Pescod JM. Beta-adrenergic receptor blocking drugs: tear lysozyme and immunological screening for adverse reactions. Br J Ophthalmol. 1977;61:354.

20.Almog Y, Monselise M, Almog CH, et al. The effect of oral treatment with beta blockers on tear secretion. Metab Pediatr Syst Ophthalmol. 1983;6:343.

21.Chizek DJ, Franceschetti AT. Oral contraceptives: their side effects and ophthalmological manifestations. Surv Ophthalmol. 1969;14:90.

22.Frankel SH, Ellis PP. Effect of oral contraceptives on tear production. Ann Ophthalmol. 1978;10:1585.

23.Valenic JP, Leopold IH, Dea FJ. Excretion of salicylic acid into tears following oral administration of aspirin. Ophthalmology. 1980;87:815.

24.Miller D. Systemic medications. Int Ophthalmol Clin. 1981;21:177.

25.Berman MT, Newman BL, Johnson NC. The effect of a diuretic (hydrochlorothiazide) on tear production in humans. Am J Ophthalmol. 1985; 99:473.

26.Coral-Ghanem C. Lentes de Vontato: Manual do Usuario. Joinville: Oftalmologia e Clinica de Lentes de Contato: Solucoes, 2002:41–44.

22

Complications Associated with Contact Lens Use

Newton Kara-Jose´,

Cleusa Coral-Ghanem,

and Charlotte E. Joslin

1.How do complications occur with contact lenses?

The contact lens wearer can have complications that either are directly induced by or are the result of existing problems that are aggravated by the presence of a contact lens. The contact lens is in direct contact with the eye and induces alterations through (1) trauma, (2) reduced corneal and conjunctival wetting, (3) decreased corneal oxygenation,

(4) stimulation of allergic and inflammatory responses, and (5) infection.

The principal causes of complications are:

●Inadequate lens-to-cornea fitting relationship

●Insufficient contact lens oxygen transmissibility

●The presence of preexisting ocular pathology

●Interference by environmental factors

●Intolerance of contact lens material

●Poorly maintained contact lenses

●Contaminated contact lenses and lens cases

●Use of incorrect contact lenses

2.What are the principal symptoms of complications?

Two principal symptoms alert one to ocular changes that can be attenuated by the use of contact lenses, delaying diagnosis of ocular lesions. They are:

1.Pain. All chronic contact lens wear contact lenses may cause corneal hypesthesia. Hydrophilic contact lenses are used to alleviate dis-

22. Complications Associated with Contact Lens Use 245

Conjunctiva

●Giant papillary conjunctivitis

●Superior limbic keratoconjunctivitis

●Infectious conjunctivitis

●Conjunctivitis secondary to mucoprotein deposits

●Conjunctival hyperemia

●Acute red eye

Cornea

●Superficial punctate keratitis

●Corneal de-epithelialization

●Corneal edema

●Corneal distortion

●Hypesthesia

●Desiccation: 3 and 9 o’clock position staining

●Sterile infiltrates

●NeovascularizationS

●uperior arcuate epithelial lesions

●Opacities

●Microbial keratitis

●Pseudodendritic keratitis

5.How does the cornea receive oxygen during contact lens wear?

The cornea is predominantly supplied with oxygen through the atmosphere, but small amounts of oxygen are also supplied through the aqueous and limbal vasculature.1,2 The amount of atmospheric oxygen pressure available to the eye through the tears in open eye conditions at sea level (155 mm Hg) is much greater than that available through the aqueous (55 mm Hg) or under closed eye conditions (55 mm Hg).3,4 Under closed eye conditions, the majority of oxygen to the cornea is supplied through the palpebral conjunctiva.5 Numerous factors beyond individual variability affect corneal oxygen demand, including corneal temperature and pH levels, previous ocular surgical history, previous contact use, and contact lens material and design.6–8

The use of contact lenses reduces the amount of oxygen available to the cornea, and this reduction is based on both lens design and lens material. Multiple measures exist for assessing the oxygen supply to cornea through a contact lens, but the most commonly used are oxygen permeability (Dk) and oxygen transmissibility (Dk/L). Oxygen permeability is a property of the lens material itself and is independent of lens design or thickness. Oxygen transmissibility is dependent on lens center thickness (L) and accounts for the difference in the oxygen availability to the cornea between lenses manufactured of the same material but with different center thickness (i.e., an aphakic lens versus a 3.00-

246 N. Kara-Jose´ et al.

D lens). Higher permeability and transmissibility values indicate more oxygen is available to the cornea.

Holden and Mertz9 determined the critical oxygen levels to avoid corneal edema in daily and extended wear contact lens use. These oxygen transmissibility levels, known as the Holden-Mertz criteria, suggest that Dk/L 24.1 10 9 is necessary for daily wear use and that Dk/L 87 10 9 is necessary for extended wear use.

Contact lenses can be divided into three main types based on the mechanism through which the cornea is oxygenated during lens wear:

1.Polymethylmethacrylate (PMMA) lenses, also known as hard contact lenses, are infrequently used today because they are impermeable to oxygen (Dk 0). In eyes fitted with PMMA lenses, corneal oxygenation is dependent entirely on oxygen dissolved in the tear film and on lacrimal exchange with the blink.

2.As the name implies, rigid gas permeable lenses are a technical advancement beyond PMMA lenses. Oxygen is supplied to the cornea through the lens material in addition to lacrimal exchange with the blink. Up to 20% of the tear volume is exchanged per blink.10 Rigid gas permeable (RGP) lenses currently are available with an oxygen permeability up to Dk 250.

3.Hydrogel, or soft contact lenses, are nearly entirely dependent on oxygen diffusing across the lens material. Only 1% of the tear volume is exchanged with each blink.10 The highest oxygen permeability currently available in hydrogel lenses is Dk 140.

6.What causes corneal edema in contact lens use? What is the clinical presentation of patients with corneal edema, and how is it managed?

Causes and Mechanism of Action

Corneal edema in contact lens use may result from either acute or chronic hypoxic corneal conditions. Most commonly, the hypoxia is caused by a continuum of two factors: (1) Contact lens materials are inappropriately selected given the individual corneal physiologic demands and the patient’s contact lens wearing schedule. (2) Contact lenses are inadequately fitted.

Types of Corneal Edema

Epithelial Edema

Epithelial edema resulting from contact lenses is rare in healthy corneas, but it can result from hypoxia. Lens type alters the amount of corneal hypoxia.

22. Complications Associated with Contact Lens Use 247

PMMA lenses

The PMMA lenses are most likely to cause epithelial edema because they are oxygen impermeable.11

Soft and Rigid Gas Permeable Contact Lenses

In soft contact lens wear, historical data are rather inconclusive about the corneal epithelial edema response to hypoxia based on measurements conducted using instruments with limited reproducibility. Optical coherence tomography (OCT), a new method of optical imaging with very high instrument reproducibility for corneal thickness measurements, demonstrates that corneal epithelial thickness does not increase in response to transient hypoxia resulting from eye closure (3 hours) with soft contact lens wear.12

Similar studies examining transient epithelial thickness changes during rigid gas permeable contact lens wear have not been performed with OCT. However, studies have been conducted that examine different measures of epithelial stress under hypoxic conditions. The effects of epithelial hypoxia can also be examined by measuring the changes in the permeability of the corneal epithelium, such as that which occurs following overnight wear of RGP lenses.13 In RGP lenses, the increase in epithelial permeability in overnight wear is dependent on the dose of hypoxia, with medium Dk lenses increasing permeability more than high Dk lenses.14 This suggests that transient epithelial edema resulting from hypoxic stress could occur if hypoxic levels were sufficient, such as that reported with PMMA lenses.11

Hypotonic Tear Film

Epithelial edema in healthy corneas can be created by a hypotonic tear film (from excessive epiphora or reflex lacrimation).15

Stromal Edema

Stromal edema occurs frequently from all types of contact lens wear. Corneal stromal swelling develops following both acute and chronic hypoxic conditions. Following transient, overnight wear of contact lenses, stromal swelling increases, with lower Dk/L lenses producing greater stromal swelling than higher Dk/L lenses. Similar outcomes resulted in chronic conditions after 1 month of continuous wear.12,16

Corneal Edema and Lens Material

In 1984, Holden and Mertz determined the critical oxygen levels necessary to avoid corneal edema in daily and extended wear contact lens use. Subsequent research has supported these findings and demonstrated that materials of increasing oxygen permeability produce decreasing amounts of corneal edema.17 Significant advances in polymer technology have allowed the recent development of contact lens materials with excellent oxygen permeability that produce no increase in corneal thickness when lenses are worn overnight compared to baseline, pre–contact lens thickness. With the advent of this new technology,

248 N. Kara-Jose´ et al.

the Food and Drug Administration (FDA), in the fall of 2001, approved two new silicone hydrogel contact lenses for up to 30 nights of continuous wear. The oxygen permeability of these new lenses (at a Dk 110 and 140, balafilcon and lotrafilcon, respectively) offers a better safety profile to prevent corneal edema in both continuous and daily wear.

Corneal Edema and Lens Fit

Because the cornea receives nearly all the oxygen through the atmosphere or the precorneal tear film, all contact lenses can reduce the amount of oxygen to the eye to the point of clinical significance. As described earlier, lenses that require lacrimal exchange to oxygenate the cornea may be more likely to cause corneal edema if they are inadequately fitted. Other factors that alter the oxygen supply to the cornea include:

1.Effects of refractive power on lens thickness (i.e., an aphakic lens versus a 3.00-D lens)

2.Effects of lens design on lens thickness, including:

●Prism ballasting for astigmatism correction

●Eccentric lenticularization

●Bifocal segments

3.Status of lens surface, i.e., presence of lens deposits

The ‘‘overwear syndrome’’ develops as a result of prolonged lens wear in hypoxic conditions. It is classically seen with PMMA lenses and hence is infrequently seen today compared with the past. Patients may develop large abrasions from excessive contact lens wear and remain initially asymptomatic because the hypoxic conditions create corneal hypesthesia. After removal of the contact lens and following gradual return of corneal sensation, severe pain develops from the corneal abrasion. Treatment should initially focus on the corneal abrasion, including prophylactic antibiotics and cycloplegic agents to alleviate pain, and should later focus on refitting the patient into a more oxygen permeable lens material.

Symptoms and Signs of Epithelial Edema

Sclerotic scatter illumination at the slit-lamp biomicroscope can be used to detect corneal epithelial edema, also known as central corneal clouding. Epithelial edema is usually central and reduces the transparency of the cornea, so a cloudy area is obvious when viewed against the dark background of the pupil. Epithelial edema may create symptoms of light sensitivity, glare, and halos. PMMA wearers were also found to have an increase in myopia and steepening of the cornea associated with epithelial edema.

22. Complications Associated with Contact Lens Use 249

Symptoms and Signs of Stromal Edema

and Associated Findings

Microcysts

Microcysts likely represent pockets of cellular breakdown products. They are likely to be extracellular as the epithelial turnover rate is only 7 days, but resolution of microcysts requires a few months following discontinuation of lens wear. Microcysts are visible in the epithelium and migrate from the deep epithelium anteriorly until they reach the surface of the cornea, at which time they stain with sodium fluorescein dye. There is a link between microcysts and corneal hypoxia, and they are traditionally seen in three conditions: (1) upon initiation of contact lens wear; (2) under hypoxic contact lens–wearing conditions, such as extended wear; and (3) when the cornea again receives adequate oxygenation, such as with discontinuation of contact lenses or when the lens material is changed to allow a significantly higher oxygen amount of oxygen to the cornea.18–20

Stromal Striae and Folds

Striae develop if the level of stromal edema exceeds 5% and may represent refractile changes resulting from collagen fibril separation with increasing stromal hydration. If the level of stromal edema exceeds 10%, posterior stromal folds develop that represent a buckling of the cornea relative to Descemet’s membrane.21

Stromal Vascularization

Both superificial and deep stromal vascularization can develop in the presence of persistent corneal edema. Further detail is provided later.

Treatment of Corneal Edema

1.Select a lens material with a higher oxygen permeability.

2.Decrease contact lens wearing time.

3.Provide an optimal contact lens fit.

7.How do contact lenses influence epithelial integrity, and what changes are visible clinically?

Causes and Mechanism of Action

Contact lenses alter the physiology and morphology of the epithelium and can influence corneal integrity. The intact corneal epithelium serves as the first line of defense against microorganisms, and only a few organisms, including Neisseria gonorrhoeae, Corynebacterium diphtheriae, and Listeria species, have penetrated an intact epithelium.22 Physiologic changes in the epithelium that result from contact lens wear can include