Ординатура / Офтальмология / Английские материалы / Medical Contact Lens Practice_Millis_2005

Blurring can also be due to dryness, which is exacerbated during sleep. Topical lubricants may help, but if they prove insufficient, soft extended lens wear should cease, but wear may be improved with an RGP lens.

Blurring due to dryness may occur in dry environments or with nocturnal lagophthalmos when eye closure is incomplete while asleep. Overnight accumulation of mucus, viscous tear film and debris cause blurring that clears rapidly on blinking.

Displacement or loss

The most common cause of displacement or loss is eye rubbing, and this is particularly seen in the elderly and children. Overnight dryness may cause the lens to dehydrate and the lens edge to lift. The upper eyelid should be everted, a drop of topical anesthetic instilled and the upper fornix swept with a sterile glass rod to ensure that the lens is not on the eye.

General anesthetics

Patients using EW lenses should be advised to remove them before surgery under a general anesthetic. If this is not practical the nurse in charge and the anesthesiologist should be informed that EW lenses are being worn to prevent damage to the lens and the build up of deposits, which may occur in the interpalpebral aperture.

Lens adherence

Lens adherence is associated with a reduced postlens tear film, and means that lenses should be fitted more loosely so that there is adequate movement. Patients should check that the lens moves on the eye on waking, and a drop of normal saline applied to the eye on waking will improve movement and reduce adherence.

Corneal vascularization

Ingrowth of blood vessels into the peripheral cornea in response to hypoxia is most common with thick, soft, aphakic lenses used in EW (Fig. 8.1). It also occurs in deposit formation, with altered tear film

biochemistry, and stagnation of the tear film under the lens. Vessels are most common at the upper corneal periphery, and the eyelids should be lifted to examine them.

Deposit formation

Deposits are more likely to be found with EW and can cause a red eye due to toxic effects and mechanical trauma. They:

●reduce oxygen transmission through the lens

●may increase the area of adsorption of chemicals from eyedrops or care solutions

●may increase bacterial adherence (Fig. 8.2).

Subepithelial infiltrates

Corneal infiltrates are collections of cells that have leaked from nearby blood vessels. They are

Figure 8.1 Ingrowing vessels associated with extended wear of a soft lens.

Figure 8.2 Deposit formation on silicone hydrogel lens.

associated with inflammation due to hypoxia, toxins, bacteria, viruses and solution preservatives, and smoking has been shown to be a risk factor in EW.19 These noninfected infiltrates are believed to be due to hypersensitivity to a specific antigen. They are peripheral, whitish, nonstaining subepithelial opacities situated 1–2 mm from the limbus (Fig. 8.3). They are often multiple.

Other terms used to describe infiltrative lesions are infiltrative keratitis, asymptomatic infiltrative keratitis and asymptomatic infiltrates.

only weakly invasive, so there is inflammation bu not infection.23 For a diagnosis of CLARE to b made the cornea must be intact.

Contact lens-related microbial keratitis

Contact lens-related microbial keratitis is the most serious complication of contact lens wear. There is a 15-times greater risk of CLRMK with conventional EW soft lenses than with RGP lenses. The infection is often caused by Pseudomonas aeruginosa, but may be caused by other organisms, including

Serratia marcescens, Staphylococcus aureus or other coagulase-negative staphylococci and streptococci (Fig. 8.4), as well as Acanthamoeba spp.

In CLRMK the strain of bacteria causing infection is important because it can determine whether or not corneal integrity must be breached for infection to occur. Under experimental conditions, increased binding of P. aeruginosa and a higher risk of CLRMK was associated with lower Dk/L lenses.20 More bacteria were recovered from the EW contact lens after sleep than from a daily-wear lens. There were fewer PMNs, which was thought to suggest that EW might inhibit PMN recruitment and therefore increase the risk of infection.21

The incidence of ulcers among disposable EW lens users was found not to differ significantly from that for conventional EW users, but was significantly higher than for conventional daily-wear users.22

Figure 8.3 Sterile infiltrate.

Figure 8.4 Bacterial corneal ulcer.

Contact lens-related peripheral ulcer

Contact lens-related peripheral ulcer (CLPU) results from hypersensitivity to S. aureus. It is characterized by focal excavation, infiltration and necrosis of the anterior stroma, but Bowman’s layer is intact, unlike in CLRMK. In all cases there is an epithelial defect, which eventually heals with the formation of a circular scar.

SILICONE HYDROGEL LENSES

The search for a lens that is safe to wear overnight has resulted in a new generation of lenses that have recently become available clinically. The lens polymers are a mix of hydrophobic and hydrophilic elements. They incorporate silicone, which provides high gas transmission, but has poor wettability, with a hydrophilic element to form a co-continuous biphasic structure, so that the material plays a part in transmitting oxygen and does not rely on the water content of the material. The result is a lens with high Dk/L, but low water content. Because of the poor wetting of the polymer, lenses are surface treated (PureVision™, Bausch & Lomb) or surface coated (Focus® Night & Day, CibaVision). A rigid high Dk lens is also now available (Table 8.2).

Early reports have suggested that silicone hydrogel lenses with Dks that vary from 99 to 140 barrers should meet the oxygen flux needs of the closed eye,24 and corneal swelling is less than is seen with Acuvue® lenses.25 There appeared to be no difference for deposits, post-lens debris, or lens wetting compared to etafilcon A26 and Maldonado-codina

found no difference in the ocular response at cellular level.27 Ocular redness was less than with a lower Dk lens.28,29

The previous generation EW lenses were unfortunately associated with a relatively high risk of corneal infections. A symposium held in 2002 reported that, compared with conventional lens use, they caused little if any increase in bacterial binding.30 However Beattie et al.31 reported a significantly greater attachment of Acanthamoeba to these materials than to conventional hydrogels, and thought this may be related to the polymer rather than the surface treatment.

Despite the improvement in corneal hypoxia, lack of movement and tear stagnation may prove to be factors in the etiology of CLRMK, and these are not altered with the new lenses (see Ch. 6).

Fitting silicone hydrogels

Balafilcon lenses are only available with 8.6 mm radius of curvature back optic zone radius, while lotrafilcon lenses are available in 8.4 and 8.6 mm radius of curvature. Discomfort may be caused if the lenses are too flat because the material is stiffer than conventional lens materials and tends to ruckle at the periphery. However care is needed to ensure that the fit is not too tight.

Complications

Post-lens debris

The presence of post-lens debris (see Fig. 5.9) has been noted with these lenses. The debris consists

of spherical, gray, translucent bodies, referred to as mucin balls. They are believed to consist of mucin and lipid. They have been associated with steeper corneal curvature, and with those patients who “never” use lubricants.32 The particles are removed by the blink, and when the lens is removed, indentations are seen in the ocular surface, which fill when fluorescein is instilled. They do not appear to affect clinical wear, but in severe cases, the use of lubricants and the reduction in the number of nights of EW minimized the condition.

The cause of post-lens debris is unknown, but may be associated with the stiffness of the lens material. During overnight wear there is less aqueous beneath the lens. This results in the formation of a more viscous, mucin-rich film beneath the lens. It is thought that the sheer forces created by the lens–corneal relationship cause this film to ball into spheres.

Superior epithelial arcuate lesions

A thin, white, staining arcuate lesion (see Fig. 5.8) is seen 1 mm or more from the limbus. The lesions associated with silicone hydrogel lenses are more likely to be paralimbal and have irregular edges. They may be due to the stiffer lenses, which do not conform to the limbus well, and may be associated with poor wetting or tight eyelids.

Other complications

Contact lens-associated papillary conjunctivitis has been reported with silicone hydrogel lenses. The stiffer material, lens edge design and wettability may be the cause. The incidence is higher than with conventional lenses, and care must be taken to examine the tarsal conjunctiva of all those wearing these lenses.

Comfort and dryness have been reported as similar to other lenses,33 but in our experience some patients suffer from dryness and cease to wear the lenses.

Risk factors include age. There is an increased risk of infiltrates in younger adults, which is exacerbated in this group by smoking.

Rare complications will not become evident until there is a large population of wearers.34

Therapeutic uses

A small series in which silicone hydrogel lense have been used as therapeutic lenses has bee reported.35 Cases included corneal erosions bullous keratopathy, corneal edema, corneal dys trophy, neurotrophic ulcer and after surgery.

Rigid high-Dk lenses

Gleeson and Albright 36 have shown that the tisilfo con RGP lens is safe for up to 30 nights of wear.

PATIENT INFORMATION FOR

FITTING EW LENSES

An accurate and informative brochure on EW lenses should be available to explain what the len can and cannot do, and the possible complication and risks. It should make clear the patient’ responsibilities to:

●wear the lens only as directed

●care for the lens in the manner agreed with th practitioner

●seek help and advice if symptoms occur

●contact the practitioner immediately if there i pain, severe discomfort, redness or photophobi

●remove the lens immediately if they have dis comfort, redness, blurred vision or discharge and contact the practitioner if the symptoms ar not resolving within 1 hour

●never to sleep in their lenses if the eye is uncom fortable or they are unwell.

Patients must be informed about how they ca contact the practitioner in an emergency, an arrangements must be made by the practice fo cover to be available out of hours. Finally a informed consent should be signed.

AFTER-CARE

At follow-up visits there should be a full review o the recent history. Visual acuity with the lens i situ and an over-refraction should be recorded and this is followed by slit-lamp examination, tak ing note of movement, centration, deposits an wetting. The lens is then removed and the ey examined. Initially there may be an increase i

microcysts but these generally settle to a low level within 3 months. Grading scales may help to monitor the condition of the eye. Accurate and detailed notes are particularly vital when new lens modalities are prescribed.

All practice staff need to understand the problems that may arise with EW, and that silicone hydrogels are entirely new. Appointments should be made as soon after waking as possible, patients must be seen the same day if there is an urgent

problem, and the practitioner or a named deputy must be able to be contacted at all times. Notes of any patient making an appointment should be checked at the time the appointment is being made, and it is helpful if notes of patients using EW lenses can be easily identified so that appointments can be made appropriately. In the event of the patient failing to attend the staff are alerted to contact the patient and remake the appointment as soon as possible.

1.Freeman RD, Fatt I. Environmental influences on ocular temperature. Invest Ophthalmol Vis Sci 1973;12:596.

2.Holden BA, Sweeney DF. The significance of the microcyst response: a review. Optom Vis Sci 1991; 68:703.

3.McNamara NA, Polse KA, Fukunaga SA, et al. Soft lens extended wear affects epithelial barrier function. Ophthalmology 1998;105:2330–2335.

4.La Hood D, Grant T. Striae and folds as indicators of corneal oedema. Optom Vis Sci 1990;67(Suppl.):196.

5.Holden BA, Mertz GW, McNally J. Corneal swelling response to contact lenses worn under extended wear conditions. Invest Ophthalmol Vis Sci 1983;24:218.

6.Holden BA, Mertz GW. Critical oxygen levels to avoid corneal oedema for daily and extended wear lenses. Invest Ophthalmol Vis Sci 1984;25:1161.

7.Rivera RK, Polse KA. Corneal response to different oxygen levels during extended wear. CLAO J 1991; 17:96–101.

8.Osborn GN, Zantos SG. Corneal desiccation staining with high water content contact lenses. CLAO J 1988; 14:81–85.

9.Sack RA, Tan KO, Tan A. Diurnal tear cycle: evidence for a nocturnal inflammatory constitutive tear fluid. Invest Ophthalmol Vis Sci 1992;33:626–638.

10.Willcox MDP, Morris CA, Thakur A, et al. Complement and complement regulatory proteins in human tears. Invest Ophthalmol Vis Sci 1997;38:1–7.

11.Carney FB, Morris CA, Willcox MD. Effect of hydrogel lens wear on the major tear proteins during extended wear. Aust NZ J Ophthalmol 1997; 25(Suppl. 1):

S36–S38.

12.Stapleton F, Willcox MDP, Morris CA, Sweeney DF. Tear changes in contact lens wearers following overnight eye closure. Curr Eye Res 1998;17:183–188.

13.Wright AR. Electron microscopy of cells collected by contact lens cytology upon eye opening. Poster presented at Am Acad Ophthalmol 1998.

14.Tan OKO, Sack RA, Holden BA, Swarbrick HA. Temporal sequence of changes in tear film composition in sleep. Curr Eye Res 1993;12:1001–1007.

15.Fleiszig SMJ, Efron N, Pier GB. Extended contact lens wear enhances Pseudomonas aeruginosa adherence to human corneal epithelium. Invest Ophthalmol Vis Sci 1992;33:908–915.

16.Fleiszig SMJ, Lee EJ, Wu C, et al. Cytotoxic strains of Pseudomonas aeruginosa can damage the intact corneal surface in vitro. CLAO J 1998;24:41–47.

17.Ramachandran L, Sharma S, Sankaridurg PR, et al. Examination of the conjunctival microbiota after eight hours of eye closure. CLAO J 1995;21:195–199.

18.Millis E. Corneal complications of extended wear soft lens in diabetes. Contactologia 1993;15:35–39

19.Cutter GR, Chalmers RL, Roseman M. The clinical presentation, prevalence and risk factors of focal corneal infiltrates in soft contact lens wearers. CLAO J 1996;22:30–37.

20.Imayasu M, Petroll M, Jester JV, et al. The relation between contact lens oxygen transmissibility and binding of Pseudomonas aeruginosa to the cornea after overnight wear. Ophthalmology 1994;101: 371–387.

21.Stapleton F, Willcox MD, Sansey N, Holden BA. Ocular microbiota and polymorphonuclear leucocyte recruitment during overnight contact lens wear. Aust NZ J Ophthalmol 1997;25(Suppl. 1):S33–S35.

22.Poggio EC, Abelson M. Complications and symptoms in disposable EW lenses compared with conventional soft daily wear and soft extended wear lenses.

CLAO J 1993;19:31–39.

23.Willcox MDP, Hume EBH. Bacteria isolated from contact lens induced acute red eye are not able to infect eyes, but bacteria isolated from microbial infectious keratitis can. Optom Vis Sci 1997;12S:74.

24.Brennan NA, Chantal Coles M-L. Models of oxygen flux through contact lenses for prediction of extended wear performance. Optom Vis Sci 1998;12S:75.

25.O’Donnell C, Maldonado-codina C, Patel A, et al. Corneal thickness and endothelial morphometry in a high Dk silicone hydrogel versus Acuvue. Optom Vis Sci 1998;12S:75.

26.Mckenney C, Becker N, Thomas S, et al. Lens deposits with a high Dk hydrophilic soft lens. Optom Vis Sci 1998;12S:75.

27.Maldonado-codina C, O’Donnell C, Mutalib HA, et al. In vivo confocal microscopy of the cornea following extended wear of Acuvue vs silicone hydrogel lenses. Optom Vis Sci 1998;12S:75.

28.Dumbleton K, Richter D, Simpson T, Fonn D.

A comparison of the vascular response to extended wear of conventional lower Dk and experimental higher Dk hydrogel contact lenses. Optom Vis Sci 1998;12:75.

29.Papas EB, Vajdic CM, Austen R, Holden BA. High-oxygen-transmissibility soft contact lenses do not induce limbal hyperaemia. Curr Eye Res 1997;16:942–948.

30.Cavanagh HD, Ladage P, Yamamoto K, et al. Effects of daily and overnight wear of hyper-oxygen transmissible rigid and silicone hydrogel lenses on

bacterial binding to the corneal epithelium: 13-month clinical trials. Eye Contact Lens 2003;29(1):S14–16.

31.Beattie TK, Tomlinson A, Seal DV. Surface treatment or material characteristic: the reason for the high level of Acanthamoeba attachment to silicone hydrogel contact lenses. Eye Contact Lens 2003;29:S40–43.

32.Dumbleton L, Jones L, Chalmers R, et al. Clinical characterization of spherical post-lens debris associated with lotrafilcon high-Dk silicone lenses. CLAO J 2000;26(4):186–192.

33.Fonn D, Dumbleton K. Dryness and discomfort with silicone hydrogel lenses. Eye Contact Lens 2003;29:S101–104.

34.Rogan M. What’s the risk? J Br Contact Lens Assn 1998;11:7–11.

35.Montero J, Sparholt J, Mély R. Retrospective case series of therapeutic applications of lotrafilcon A silicone hydrogel soft contact lens. Eye Contact Lens 2003;29:S54–S56.

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CHAPTER CONTENTS

Conjunctival inflammation 95 Corneal inflammation 98 References 102

Further reading 102

A red eye is characteristic of inflammation, and ma be due to inflammation of the conjunctiva, epis clera, sclera or cornea, or structures within the eye It may be the direct result of lens wear, or a coinci dental finding unrelated to the lens. Lens-relate causes include acute and chronic hypoxia, len defects and damage, inadequate blinking, deposi formation, and a tight fitting lens. It may also b due to the care regimen or be patient related.

The most important cause of a red eye, associ ated with contact lens wear, is contact lens-relate microbial keratitis (see Ch. 6). A red eye is likely t be related to contact lens wear if it occurs onl when the lens is worn, occurs immediately th lens is inserted, increases with increased wearin time, or if the symptoms settle rapidly after th lens is removed.

A nonlens-related red eye problem may becom worse with lens wear, due to mechanical irritatio by the lens, hypoxia or reduced wetting. Thi chapter considers noncontact-related causes of red eye, which may pose diagnostic problems fo the contact lens practitioner.

CONJUNCTIVAL INFLAMMATION

The particular features of conjunctivitis are:

●dilatation of the conjunctival vessels, causin redness, which is greatest in the fornices an least near the limbus, and

●a discharge formed from an exudate from th dilated vessels, a cellular infiltrate, mucus an tear film.

A severe bacterial infection is characterized by a yellow mucopurulent discharge. A scant mucopurulent discharge is seen in chlamydial infection. A watery discharge is produced in viral and toxic conditions, while a white mucus discharge is more common in allergic conjunctivitis. In some cases there may be enlarged preauricular lymph nodes.

Bacterial conjunctivitis

In acute bacterial conjunctivitis (Fig. 9.1), the patient complains of a gritty sensation, and the eyelids are often stuck together on waking, and may have to be bathed open. There is marked injection and swelling (chemosis) of the conjunctiva, and there may be conjunctival hemorrhage. A few papillae may be present on the upper tarsal conjunctiva. The most common causative organisms are

Staphylococcus epidermidis, Staphylococcus aureus and Haemophilus influenzae.

Acute bacterial conjunctivitis does not generally affect vision, but the discharge may cause intermittent blurring.

Chlamydial infection

Chlamydia trachomatis causes a sexually transmitted disease that usually affects young people and causes a follicular conjunctivitis (Fig. 9.2). It causes a keratoconjunctivitis characterized by a mucopurulent discharge.

Large semitransparent follicles are found in the lower fornix, at the limbus, and on the bulbar

conjunctiva, and there may be an epithelial keratitis. A preauricular node is common.

Treatment is with topical tetracycline ointment or oral tetracycline, erythromycin or doxycycline. Tetracycline should not be used in pregnancy, nursing mothers or children because it may affect the teeth of the child. Patients should be referred to their doctor or local sexually transmitted disease clinic for urogenital investigation and contact tracing.

Viral conjunctivitis

There can be less conjunctival injection in viral disease than in bacterial infection, but there may be small hemorrhages, particularly in the upper tarsal conjunctiva. Follicles are present in the lower fornices and super tarsal plate, and enlarged preauricular glands may be felt.

Adenoviral keratoconjunctivitis

Adenovirus infection may present either as pharyngoconjunctival fever, usually in children, or as epidemic keratoconjunctivitis (Fig. 9.3), which is the form most likely to be encountered by the contact lens practitioner. The infection is highly contagious.

The virus spreads by contact between finger and eye, by sharing towels, pillows and items such as handkerchiefs, by applanation tonometers and similar instruments, and by splashing of the discharge-laden tear film with the blink. It is vitally

Figure 9.3 Adenovirus keratoconjunctivitis.

important for clinicians to wash their hands immediately after being in contact with an acute red eye because there is a very real risk of transferring the virus either to the next patient or to the clinician’s own eye.

Adenovirus infection causes a follicular reaction in the conjunctiva, and there is often an enlarged preauricular lymph node. Initially there is a diffuse punctate keratitis, which may resolve spontaneously or focal, white, nonstaining epithelial opacities may develop, which may be followed by anterior stromal infiltrates. The patient may complain of a sore throat and generalized malaise.

Tonometer prisms, if not disposable, must be rubbed to remove debris, then soaked in hypochlorite for at least 20 minutes. Slit lamps should be wiped down with hypochlorite solution or spray (see Ch. 10).

Antibiotics are not effective against viral disease, but may be useful if secondary infection is present. Antiviral agents are not effective. Topical corticosteroids will suppress the inflammation, but are only used in severe cases because the inflammation may recur when the treatment ceases. Dark glasses relieve the photophobia, and are helpful in preventing the spread of the infection by reducing spray caused by blinking.

Allergic conjunctivitis

Allergic conjunctivitis (see Ch. 8) is characterized by itching, puffiness of the eyelids, chemosis (which may be severe), moderate injection and a stringy,

white mucus discharge. Papillae are present in th upper tarsal conjunctiva.

Superior limbic keratoconjunctivitis

The superior limbic keratoconjunctivitis o Theodore is a bilateral condition of unknown eti ology that occurs most often in middle-aged women, and may be associated with thyroid dis ease. Patients complain of a foreign body sensa tion, burning, photophobia and mucus discharge.

There are papillae in the superior tarsus, and hyperemia and thickening of the superior, bulba conjunctiva, which is most marked at the limbus Punctate epithelial erosions may be seen on th upper cornea, and these lesions and those on th superior bulbar conjunctiva stain with fluorescein and Rose Bengal. Many patients have corneal fila ments that can be removed with acetylcysteine 5% eye drops.

Superior limbic keratoconjunctivitis may resolv spontaneously, but topical lubricants should b prescribed and a large, soft therapeutic contac lens may be helpful. If these measures fail, cauteri zation of the superior bulbar conjunctiva may b considered.

Thimerosal sensitivity

In the past some soft lens contact lens solution and eye drops were preserved with thimerosal This can result in a noninfective condition in pre viously sensitized individuals. It causes injection of the superior conjunctiva and marked cornea vascularization, which extends centrally, preceded by tongues of hazy epithelium. All drops and solutions containing thimerosal should be stopped and replaced with nonpreserved solutions, and the lenses replaced. Most thimerosal-containing solutions are no longer available in the UK.

Pinguecula

A pinguecula is a common, often bilateral creamy yellow lesion in the interpalpebral aperture, media or lateral to the limbus (Fig. 9.4). These lesions ar often noted by contact lens wearers and give ris to considerable anxiety. They consist of degenerat collagen fibers of the conjunctival stroma, covered

Figure 9.5 Staining pingueculum.

by a thinned epithelium. They may become calcified. Pingueculae may cause alteration in tear flow with subsequent conjunctival drying, which may be demonstrated by staining with fluorescein, and the conjunctival vessels become dilated (Fig. 9.5).

The patient can be reassured as to the nature of the lesion. If the lesion enlarges, becomes chronically inflamed or is causing great anxiety it can be excised surgically.

Pterygium

Characteristically pterygia occur in those who have been exposed to sun and wind. A pterygium (Fig. 9.6) is an invasive inflammation in which there is a breakdown of the limbal barrier as a result of focal limbal irradiation of basal epithelial cells and stem cells.1 The pterygium affects the

anterior stromal lamellae with degeneration of the collagen fibers. It demonstrates more vascularization than seen with pingueculae. Initially small opacities arise at the medial limbus, and a wingshaped fold of conjunctiva extends onto the cornea. A line of iron deposition (Stocker’s line) may precede the head where there is stagnation of the tear film.

Recent work2 has shown that topical nonsteroidal anti-inflammatory drugs, such as 0.1% indomethacin, reduces inflammation and may be preferable to treatment with topical corticosteroids. The pterygium may be removed surgically if it endangers the visual axis or if it is very unsightly. There is, however, a considerable risk of recurrence, and in nearly all cases a visible scar. Surgical excision is performed by grafting free conjunctiva, usually from the bulbar surface of the same eye. Alternatively -irradiation or mitomycin C are equally effective (i.e. 20% recurrence rate over 5 years rather than 50%).

CORNEAL INFLAMMATION

Bacterial infections

The most serious inflammatory condition of the external eye associated with contact lens wear is microbial keratitis, but it may also occur in the absence of a contact lens. The ulcers are often characteristic of the causative organism. Staphylococcus aureus and Streptococcus pneumoniae tend to produce small, yellowish opaque changes in the