Ординатура / Офтальмология / Английские материалы / Medical Contact Lens Practice_Millis_2005

Table 2.6 Development of dry eye disease

Stage 1 Reduced tear production or increased evaporation

Stage 2 Reduced conjunctival goblet cell density in conjunctiva

Stage 3 Increased epithelial cell loss Stage 4 Unstable corneal–tear interface

Lubrication

Artificial tear drops soothe the eye and act on stage 4 (destabilization of the corneal–tear interface) of the disease. They usually contain hydroxymethylcellulose, hydroxyethylcellulose or polyvinyl alcohol, and most contain preservatives, often benzalkonium chloride, which can be toxic to the epithelium and can bind to soft lenses.

Preservatives

Preservative-free drops, suitable for use with all types of lens are now available including Focus Clerz® (CibaVision), Refresh® (Allergan), and Vislube® (Chemedica). Ointment is best avoided because it breaks up the tear film and, even if used overnight, will coat the contact lens when it is inserted next morning.

Removing the preservatives benefits stage 3 (increased corneal epithelial desquamation) by improving the barrier function of the cornea, but animal experiments suggested that they may be associated with reduced goblet cell density.28

A further improvement in barrier function occurs if a balanced electrolyte solution (BES) is used, and this also maintains normal goblet cell density (stage 2 – loss of conjunctival goblet cells).

Hyperosmolarity

To reduce the hyperosmolarity of stage 1 (reduced tear production or increased evaporation), a hypotonic solution of less than 225 mOsm/L is needed to lower the osmolarity (normal 300 mOsm/L).

Conservation

If lubricants are insufficient to relieve the symptoms then punctal plugs may be tried. These

occlude the lower or upper punctum, or both, and prevent the tears draining away. Plugs made of gelatin or collagen may be used for a trial of occlusion, but silicone plugs last longer and have been shown to decrease tear osmolarity and Rose Bengal staining.29 Short-term objective and subjective benefits to contact lens wearers have been reported.30 If temporary occlusion is successful then permanent occlusion can be attempted by electrocautery, though recanalization may occur.

Contact lens wear

Mild cases of dry eye with high-water-content lenses should be changed to lenses with a lower water content or a thicker lens, and the wearing time reduced to minimize hypoxic changes. Some of the newer polymers hold water better and may relieve the condition, for example Proclear® lens (Coopervision).

Almost all tears (90%) are located in the tear meniscus. During the blink the upper eyelid dips down into the tear meniscus along the lower eyelid and pulls the fluid up over the eye as it opens. If there is a mild ectropion the tear meniscus is displaced and is in the wrong position for this to occur. However, it is possible to use a spherical lens with a prism ballast, which will plug the ectropion with the prism, allowing the tear film wedge to be maintained.

For moderately severe dry eyes it may be preferable to change to an RGP lens, which contains approximately 2% water, and provides more oxygen to the cornea.

Silicone hydrogel lenses have a low water content and may be useful in some cases, but silicone does not wet well and these lenses are made with special surfaces to improve wetting.

People with severe dry eyes should stop wearing contact lenses unless contact lenses are essential for vision, in which case frequent careful supervision is necessary and the risk of infection must be explained repeatedly in detail.

Patients with severe dry eyes may be more comfortable with the lenses than without, but risk corneal opacification and severe vascularization. A corneal graft may be needed to manage the opacities, but if the cornea is vascularized, graft rejection is more likely.

Patients can help by avoiding dry, smoky atmospheres, using humidifiers and ensuring that they blink correctly.

An adequate volume and quality of tear film is necessary for ocular health, good vision and comfortable, successful contact lens wear. Assessment of the tear film is therefore an important

examination in all contact lens wearers. An pre-existing condition should be treated, the appro priate lens material selected, and symptoms mini mized by use of lubricants. Punctal plugs may b considered if more conservative methods prov inadequate.

1.Albarran C, Pons A, Lorente A, et al. Influence of the tear film on the optical quality of the eye. Contact Lens and Anterior Eye 1997;20:129–135.

2.Bron A. Reflections on the tears. Eye 1997;11:583–602.

3.Chew C, Hykin PG, Jansweijer C, et al. The casual level of meibomian lipids in humans. Curr Eye Res 1993;12:255–259.

4.Gipson I, Inatomi T. Mucin genes expressed by the ocular surface epithelium. Prog Retinal Eye Res 1997;16:81–98.

5.Cope C, Dilly P, Kaura R, Tiffany, J. Wettability of the corneal surface: a reappraisal. Curr Eye Res 1986; 5:777–785.

6.Liotet S, Van Bijsterveld O, Kogbe O, Laroche L. A new hypothesis on tear film stability. Ophthalmologica 1987;195:119–124.

7.Lemp M. Report of the National Eye Institute/ Industry workshop on clinical trials in dry eyes. CLAO J 1995;21:221–232.

8.Murillo-Loez F, Pflugfelder SC. Dry eye. In: Cornea: Fundamentals of Cornea and External Disease, eds Krachmer JH, Mannis MJ, Holland EJ, vol. 2,

pp 663–687. New York: Mosby; 1997.

9.McMonnies C, Ho A. Patient history in screening for dry eye conditions. J Am Optom Assoc 1987; 58:296–301.

10.Bandeen Roche MK, Schein O, Munoz B, et al. Challenges to defining and quantifying dry eye. Invest Ophth Vis Sci 1995;36(Suppl.):S862.

11.Khurana AK, Chaudhary R, Ahluwalla BK,

et al. Tear film profile in dry eye. Acta Ophthalmol 1991;69:79–86.

12.Sweeney DF (ed). CCLRU Grading scales. In: Silicone Hydrogels, Chapter 6 Fig 6.2. Butterworth Heinemann; 2004.

13.Mengher LS, Bron AJ, Tonge SR, Gilbert DJ. Effect of fluorescein installation on the precorneal tear film stability. Curr Eye Res 1985;4:9–12.

14Guillon J-P. Non-invasive Tearscope Plus routine for contact lens fitting. Contact lens and Anterior Eye 1998;(Suppl. 21):S31–S40.

15.Elliott M, Fandrich H, Simpson T, Fonn D. Analysis of the repeatability of tear break-up time measurement techniques on asymptomatic subjects before, during and after contact lens wear. Contact Lens and Anterior Eye 1998;21: 98–103.

16.Farris RL. Contact lenses and the dry eye. In: International Ophthalmology Clinics: Dry Eye, eds Smolin G, Friedlander MH, pp 129–136. Boston: Little Brown; 1994.

17.Asbell P, Chiang B, Li K. Phenol-red thread test compared to Schirmer test in normal subjects. Ophthalmology 1987;94(Suppl.):128.

18.Chiang B, Asbell P, Franklin B. Phenol-red thread tes and Schirmer tear test for tear production in normal and dry eye patients. Invest Ophthalmol Vis Sci 1988 29(ARVO Suppl.):337.

19.Cho P, Yap M. Effect of contact lens wear on Hong Kong Chinese. J BCLA 1995;18:87–94.

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

21.Gilbard JP. Dry eye disorders. In: Principles and Practice in Ophthalmology, eds Albert DM, Jakobiec FA, pp 257–276. Philadelphia:

WB Saunders; 1994.

22.Bron AJ, Benjamin L, Snibson GR. Meibomian gland disease. Classification and grading of lid changes. Eye 1991;5:395–411.

23.Efron N, Brennan NA, Duldig AS, Russo NJ. Dehydration of hydrogel lenses under normal wearing conditions. CLAO J 1987;13:152–156.

24.Helton DO, Watson LS. Hydrogel contact lens dehydration rates determined by thermographic analysis. CLAO J 1991;17:59–61.

25.Tomlinson A, Cedarstaff T. Diurnal variation in human tear evaporation. J BCLA 1992;15: 77–79.

26.Hamano T, Sachiko M, Kotani S, et al. Tear volume in relation to contact lens wear and age. CLAO J 1990;16:57–61.

27.Temel A, Kazokoglu H, Taga Y, Orkan A. The effect of contact lens wear on tear immunoglobulins. CLAO J 1991;17:69–71.

28.Gilbard JP. Dry eye: pharmacological approaches, effects and progress. CLAO J 1996;22:141–145.

29.Gilbard JP, Rossi SR, Azar D, Heyda K. Effect of punctal occlusion by Freeman silicone plug insertion

on tear osmolarity in dry eye disorders. CLAO J 1989;15:216–221.

30.Virtanen T, Huotarik K, Harkonen M, Tervo T. Lacrimal plugs as a therapy for contact lens intolerance. Eye 1996;10:727–731.

For rigid lens wearers the influence of eyelid geometry on lens centration is such that:

●superior lens decentration is associated with a low upper eyelid position and a small aperture

●inferior decentration is associated with a high upper eyelid and a large aperture.1

Eyelid tension

Tight eyelids may make insertion difficult in the adaptation period, but this usually improves with time. An eyelid attachment may be difficult to achieve if the eyelids are too loose.

Eyelid tension is an important factor when fitting rigid, alternating, bifocal lenses because the lower eyelid needs to be high enough, and sufficiently tight, to push the lens up on downward gaze to center the reading portion over the pupil.

Blinking

A reduced blink rate occurs naturally when performing any visual task such as reading, driving, or using a VDU. The upper eyelids close over the globe and dip into the tear film meniscus at the lower eyelid margin and spread the tear film evenly over the surface of the eye as the eyelids open. A reduced blink rate may result in dryness and can result in 3 and 9 o’clock staining in RGP lens wearers. These patients must be advised to practise closing the eye gently and completely.

Distorted eyelids

Eyelids that are scarred and distorted may lead to dryness, and irritation of the eyelid margins by the lens edge. There is an increased risk of infection if stagnant pools of tear fluid are created.

Entropion

Entropion (Fig. 3.1) is the inversion of the eyelid and usually affects the lower eyelid. It is more common in the elderly when it is due to atrophy of the orbital tissues, but may also result from scarring of the posterior lamella of the eyelid.

Mild entropion may only become obvious if the eyelids are squeezed tightly together and then opened, when the eyelids remain rolled in.

Entropion may cause inflammation and ulcera-

the cornea. A large soft contact lens can be fitted until surgical correction can be carried out.

Ectropion

Ectropion (Fig. 3.2) is eversion of the eyelid and may be due to senile changes, scarring of the anterior lamella of the eyelid or facial nerve (cranial nerve VII) palsy. The puncta are everted resulting in poor lacrimal drainage and a stagnant pool of tears in the lower fornix, which predisposes to infection.

For mild ectropion it may be sufficient to reduce any inflammation affecting the eyelid, allowing the eyelid to return to its normal position. If there is a swelling or tumor, for example a cyst or granuloma, this should be removed. If simple measures are insufficient to achieve apposition of the eyelid and globe, surgery should be considered.

Figure 3.1 Entropion.

Many elderly people frequently dab at their eyes with a handkerchief, actively pulling the eyelid from the globe as well as risking the transfer of infection. They should be warned that this may aggravate the situation.

Eyelid overlap in the initial and settled position of a contact lens is important to achieve lens– eyelid attachment, and a lack of support from the eyelids will allow the lens to drop.1

If the ptosis is associated with rigid lens wea and it is difficult for the patient to stop wearin the lenses the condition may resolve if thinne RGP lenses with eyelid attachment are worn or i the patient is refitted with soft lenses.

Scleral lenses have been used to correct ptosi by incorporating a ledge or slot in the upper par of the lens in which the eyelid can rest. More usu ally surgical correction is necessary.

Ptosis

Drooping of the upper eyelid (ptosis) is sometimes seen in contact lens wearers and can occur during the adaptation period or any time later. It may be related to a defective or badly fitting contact lens. Jupiter and Karesh2 suggest that pulling the eyelids laterally followed by a harsh blink, as in the removal of a rigid lens, may be the cause, as in removal of a rigid lens. Alternatively they thought that inflammation and edema of the eyelid may result in the lens edge rubbing the eyelid, but comment that the palpebral conjunctiva was clear in such cases. Resolution occurred spontaneously when lens wear ceased.

Ptosis may be due to mechanical conditions increasing the weight of the eyelid, such as chalazion, active GPC, a contact lens embedded in the eyelid, or the presence of a tumor. Ptosis is common in the elderly (senile ptosis) due to degeneration of the levator aponeurosis. Scarring resulting in a loss of elasticity may also cause ptosis. A less common condition is a neurological lesion of the oculomotor nerve (cranial nerve III).

On examination the eyelid crease may be high or absent in cases of levator insufficiency. The patient may have a chin-up head posture if the condition is severe to see beneath the eyelid. It is important to ensure that the condition is a true ptosis and not an apparent ptosis due to a small eye or eyelid retraction on the other side.

The vertical height of the palpebral aperture should be measured and compared to that of the other eye.

The function of the levator muscle is assessed by placing the thumb firmly against the brow to prevent the action of the frontalis muscle. The patient is asked to look down as far as possible, and then to look up, and the movement of the eye-

Dermatochalasis

Dermatochalasis is a condition in which there i excess skin of the upper eyelid, and this may giv rise to a pseudoptosis.

Abnormalities of the lashes

Trichiasis is the acquired posterior misdirection o previously normal lashes. It can cause cornea damage, punctate staining and may result in ulcera tion and infection. A soft lens will provide tempo rary relief until the lashes can be removed wit forceps (epilation), electrolysis, cryotherapy o laser ablation.

Distichiasis

Distichiasis describes a second row of lashes aris ing from, or slightly posterior to, the orifices of th meibomian glands.

Disorders of the eyelids

Blepharitis

Blepharitis may result in trichiasis, loss of lashe and scarring of the eyelid, and predisposes t chalazion and stye (see Ch. 2).

Stye

A stye is an acute suppurative inflammatio involving the eyelash follicle and and the gland of Zeis and Moll, and is usually due to staphylo coccal infection.

There is a painful, red swelling at the base of th lash, which will normally resolve spontaneously but healing may be expedited by removing th eyelash, and with hot compresses. Antibiotics ar only necessary if the inflammation spreads t

lenses may aggravate the condition and any discharge will coat the lens.

Chalazion

A chalazion is a chronic granuloma of the meibomian glands that can occur when a meibomian gland becomes blocked. It presents as a welldefined firm swelling in the upper or lower eyelid and may be associated with a conjunctival granuloma, which can be seen when the eyelid is everted. Most commonly the lesion is single, but several may be present simultaneously, and more than one eyelid may be affected. It is common in patients with meibomian gland disease.

The cyst may resolve spontaneously when the patient’s own anti-inflammatory mechanisms remove the retained lipid. Sometimes the cyst becomes infected, usually with staphylococci, and is painful. The cyst may discharge either anteriorly or posteriorly.

Hot compresses are useful in the early stages, and antibiotics may be necessary if the lesion is infected or recurs. If the cyst persists for weeks, incision and curettage may be necessary.

Recurrent or atypical chalazia should be referred for biopsy to exclude the possibility of a basal cell or sebaceous carcinoma.

Chalazia may cause astigmatism from pressure on the globe and it is inadvisable to prescribe spectacles or fit contact lenses until the swelling has resolved.

Meibomian gland disease

Meibomian gland disease is described in Chapter 2.

Lacrimal system

The problems associated with dry eye have been dealt with elsewhere in this book (see Ch. 2).

A watering eye may cause problems for the contact lens wearer because of the increased risk of infection from a stagnant pool of fluid in the lower fornix or upward spread from an infection of the lacrimal sac. RGP lens fits may be less stable, and vision may be reduced.

Ectropion, eversion of the punctum, laxity of the lower eyelid or a foreign body blocking the

Table 3.1 Causes of a watering eye

Stimulation of production

Chalazion

Trichiasis

Adaptation to poor fitting contact lenses

Diminished drainage Ectropion, entropion

Poor apposition of puncta Foreign body blocking punctum

Obstruction of canaliculi or nasolacrimal duct

punctum can all give rise to inadequate drainage of tear fluid (Table 3.1). A careful search medial to and below the lower eyelid should seek evidence of swelling or tenderness of the lacrimal sac. Pressure applied over the sac may cause a reflex expulsion of discharge via the lower eyelid punctum. Pressure over the canaliculi with a glass rod may express pus or fungal concretions.

Nasolacrimal obstruction may be relieved by syringing the tear ducts with saline. If this proves inadequate a dacryocystogram is performed, in which radiopaque fluid is syringed through the tear ducts. The resultant radiograph will identify an obstruction or constriction. If symptoms are severe and a block is identified a dacryocystorhinostomy is undertaken, in which a new channel is made for the tears into the nose. This is a major operation and should only be performed in patients who have recurrent infections or copious, persistent watering.

Tumors of the eyelids

Benign tumors

Benign tumors include keratoses, nevi and xanthelasma.

Keratoses These tend to occur in the elderly. Seborrheic keratoses are brown, greasy tumors with a warty surface, whereas senile keratoses are flat and scaly. The senile type may undergo malignant change to become a squamous cell carcinoma.

Nevi A nevus (mole) consists of nevus cells and may be pigmented or nonpigmented. Intradermal nevi occur on the eyelid margin as smooth,

Figure 3.3 Intradermal nevus.

dome-shaped lesions (Fig. 3.3), which are sometimes associated with hairs. They must be differentiated from malignant melanomas, and if removed removal must be complete and the excised area sent for histology to ensure that all the tumor has been removed.

Xanthelasma These lipid-filled swellings are most often seen at the medial aspects of both eyelids. They may be associated with diabetes mellitus and excess cholesterol, so such patients should be referred to their family doctor for investigation.

Malignant tumors

Concern should be aroused that a lesion may be malignant if it is recent, growing, itching, bleeding or ulcerating.

Basal cell carcinoma Basal cell carcinoma (BCC, rodent ulcer) (Fig. 3.4) is the most common malignant tumor seen in clinics. It is slow growing and commences as a firm nodular lesion with dilated vessels on the surface. If untreated a central ulcer forms with a rolled, raised, pearly edge in which bleeding may result from minor trauma. It is slow

Figure 3.4 Basal cell carcinoma (rodent ulcer).

growing and does not metastasize, but is highl invasive. Local surgical excision with a wide mar gin around the tumor is usually very successful BCCs are sometimes ignored, particularly by th elderly, and the tumor spreads locally and invade the eyelids, orbits or bone.

Squamous cell carcinoma Squamous cell carci noma is much less common than BCC, but devel ops much more rapidly and metastasizes to th regional lymph nodes. It may form a nodule, a ulcer or a papilloma.

Malignant melanoma Malignant melanom tends to spread from the conjunctiva and eithe forms a nodule or spreads superficially. Not all ar pigmented. It must be differentiated from benign nevus.

Kaposi’s sarcoma Kaposi’s sarcoma is a vascula red–brown lesion and is often associated wit human immunodeficiency virus (HIV) infection.

As part of every examination the contact len practitioner will inspect the eyelids and shoul refer any suspicious lesion for biopsy to identif the histology.

1.Carney LG, Mainstone J, Carkeet A, et al. Rigid lens dynamics: lid effects. CLAO J 1997;23:69–77.

2.Jupiter D, Karesh J. Ptosis associated with PMMA/ RGP contact lens wear. CLAO J 1999;25:159–162.

Key J. Comparative study of eyelid cleaning regimens in chronic blepharitis. CLAO J 1996;22:209–212.

Greiner JV, Leahy CD, Glonek T, et al. Effects of eyelid scrubbing on the lid margin. CLAO J 1999;25:109–113.

CHAPTER CONTENTS

Ocular characteristics of the aging eye 36 Contact lens correction 37

References 42 Further reading 42

A number of changes, other than presbyopia, occu in the older eye. These should be taken into accoun when considering contact lenses for older patients many of whom have worn lenses for most of thei adult life, and do not wish to start wearing specta cles. Of these older people, many are employed, bu practitioners will, however, be fitting many more very active retired and semiretired people who hav much greater aspirations than in the past. It i important to manage their expectations from th beginning, particularly if they are new to contac lens wear, and to discuss possible outcomes. The should realise that all types of presbyopic contac lens correction are a compromise and that vision i likely to vary under different lighting conditions.

Older patients are liable to have longer, mor complicated medical histories than younge patients, and both systemic disease and medica tions may influence successful lens wear, fo instance many drugs can cause dry eyes.1

A history of previous ocular or refractive sur gery can affect the type of lens prescribed. A few patients still need contact lens correction afte cataract surgery because an intraocular lens (IOL)

●was deemed unsuitable

●failed to correct the refractive error completely

●has been removed because of complications.

In some cases, where one eye has been fitte with an IOL, it may be necessary to fit the unoper ated eye with a contact lens to avoid anisometropi and achieve binocular vision.

It is also useful to fit a temporary contact len that corrects for near vision after one IOL has bee

implanted to see whether a patient would prefer correction for near or distance vision when the second IOL is inserted.

If the patient is a previous lens wearer it is important to ensure that any problems that arose with vision or tolerance are considered.

The older patient has many and varied interests. Correction may be needed to play games such as bridge or golf, or to read the church service book. Many of this age group are either already using a computer or take an interest in computers in their retirement, and many attend art classes. Some are studying for degrees. A high percentage need to drive either because of lack of transport where they live or because of disabilities.

During the ophthalmic examination special attention should be paid to ensure that there is no evidence of glaucoma, and a careful refraction is needed to exclude an organic cause of reduced vision.

If there is a reduction in vision that cannot be corrected, or evidence of loss of visual field, then monovision or bifocal contact lenses should be avoided. Many of these patients have dry eyes and this can affect the success of contact lens wear.

OCULAR CHARACTERISTICS OF THE AGING EYE

Eyelids

With increasing age there is a loss of muscle tone and the eyelids become more lax, often with reduced movement (Table 4.1). Hill2 noted that the horizontal length of the palpebral aperture becomes less with age, especially in the primary position and in upward gaze. There is reduced tear film drainage due to shortening of the intercanthal line, and there is poor function of the superior levator muscle and a gradual weakening of the lower eyelid retractors. The lateral canthus becomes lax and moves medially.

The reduction in eyelid tension allows the eyelids to ride over a rigid lens more easily, but makes lens removal more difficult. It is often better to remove the lens using two hands. The lower eyelid is pushed against the globe of the eye with the index finger of one hand and the upper eyelid margin should be held against the globe with the index

Table 4.1 Characteristics of the aging eye

Laxity and loss of eyelid tone Reduced tear film drainage Reduced, less stable tear film

Reduction in the number of active meibomian glands Gradual fall in levels of lysozyme and lactoferrin Reduced corneal sensitivity

Decreasing immune system activity Reduced pupil size

Altered refractive state

Increased risk of glaucoma, cataract and macular changes

finger of the other. The eyelids must be open slightly wider than the diameter of the lens; this may be helped by asking the patient to look surprised. Bringing the eyelids together with the fingers should eject the lens. RGP lens wearers may be taught to use a suction device, but care must be taken to ensure that the lens is on the cornea before removal is attempted or corneal damage may occur.

Changes in muscle tone may result in entropion or ectropion. Entropion may cause corneal staining as the inturned lashes brush the cornea. This may be relieved by a soft contact lens. In cases of ectropion there is a greater risk of infection because the stagnant pool of tears that forms is readily colonized by microorganisms.

The number of active meibomian glands from which secretion can be expressed decreases with age, but the lipid layer thickness remains the same.3 It is postulated that this is due to the retention of tears that occurs with advancing years.

Both forced and reflex blinking should be examined to ensure proper wetting of the lens.

Normal eyelid function may be affected by systemic disease such as Parkinson’s disease and Bell’s palsy, and eyelid surgery often affects the position of a lens and may cause poor lens wetting.

Tear film

A relative, rather than an absolute, deficiency of the tear film is more common in older than in younger patients.

There is a linear decline in tear production4 and tear volume,5 and patients with a reduced volume showed a higher incidence of complications with each of the contact lenses tested. The reduced tear