So the going doesn't get tough

Optometric Management, Apr 2000 by Suche, Kimberly A, Shovlin, Joseph P, Epstein, Arthur

How to keep minor problems minor for contact lens wearers.

With advanced technology and newer materials giving us more solutions and contact lens options, more people are successfully wearing contact lenses today than ever before. So, in order to avoid serious problems, you must be aware of the types and effects of minor soft contact lens complications. Here, we'll discuss the consequences of several complications and present the steps you can take toward preventing their escalation.

CORNEAL STAINING

Contact lenses can create the following corneal staining problems:

Arcuate staining. Arcuate staining in the midperipheral cornea just below the pupil is reported with soft lenses of various designs, water contents and fitting relationships.

"Smile" arcuate staining is often associated with a loose-fitting soft lens made of crofilcon material. The rigidity of this polymer is probably a factor in the etiology of the irritation. Patients typically show no symptoms except in severe cases.

To manage the problem, select a steeper base curve radius or use a hydrogel lens material.

Epithelial splitting. A horizontal or arcuate lesion, usually adjacent to the superior limbus, characterizes this complication of hydrogel lens wear (see figure at right).

The lesion appears as diffuse, scattered punctate dots aligned in a linear or arcuate fashion in the superior cornea under the upper lid. At first the patient is asymptomatic, but later she'll complain of lens awareness, burning, itching and redness.

The cause of this problem appears to be a combination of mechanical and hypoxic effects. Tight-fitting, "stiff" hydrogel lenses can be a culprit.

Have the patient discontinue lens wear for a few days to a few weeks. Then refit her into new lenses, preferably with a plannedreplacement or disposable-lens material. If the condition recurs, refit her into a rigid gas permeable (RGP) lens material.

* Diffuse epithelial staining. Contact lens solutions can cause diffuse epithelial staining (bottom of next page). An immediate hypersensitivity reaction is a common response to solution preservatives. In a delayed hypersensitivity response, the chemicals in the solutions act as haptens and combine with tissue protein to initiate a response. This results in diffuse staining, dendriform lesions, infiltration and even neovascularization. Eyes become red and patients complain of a burning sensation.

This reaction is most common in patients with an history of hypersensitivity to various antigens. Determine by a thorough case history whether the patient has asthma, hay fever or allergic dermatitis. If she's wearing soft lenses, changing solutions - preferably to an oxidative system - should eliminate the problem.

Disposable contact lenses or regular, proper lens cleaning supplemented with enzyme use will minimize protein buildup and preservative concentration when a rare toxicity issue is a concern.

Poor patient compliance with a care regimen for reusable contact lenses can also cause diffuse epithelial staining. Debris accumulates on the back surfaces of the lenses and eyes burn and become red. Again, emphasize regular, thorough lens cleaning, supplemented by weekly enzyme use.

As you can see, there are many differential diagnoses for corneal staining associated with soft contact lens wear. You should understand the importance of fluorescein evaluation of the corneal epithelium on contact lens follow-up visits. Fluorescein evaluation lets you adjust the fit of the lens, or change the replacement cycle or solution regimen before more of the corneal epithelium is compromised and your patient becomes at risk for infection.

EDEMA

Edema can manifest in three different ways:

Superficial punctate keratitis (SPK). If a toxic (solution preservative) or mechanical cause for SPK can be eliminated, hypoxic stress is often to blame. The immediate cause of this problem is probably premature desquamation of stressed superficial cells, which leaves microscopic gaps on the corneal surface where fluorescein pools. Many clinicians believe that the longer SPK exists, the greater the likelihood of microbial infection, especially during extended contact lens wear when the epithelium may never have the opportunity to heal completely.

Treat SPK by providing more oxygen to the eye. You can do the following:

fit a lens of higher oxygen transmission.

increase tear pumping.

reduce wearing time.

Corneal edema in a contact lens wearer is the classic sign of hypoxic stress. Edema from soft lens wear is difficult to observe because it's generally spread over the entire epithelium. Hypoxia reduces the epithelial healing rate by slowing the mitotic activity and thinning the epithelial cells. You must modify or discontinue your patient's lens wear when the epithelium is compromised. Wearing lenses under these conditions increases the likelihood of infection, especially in patients who are susceptible or whose immunity is compromised.

Epithelial microcysts. These microcysts (see figure on the next page) were first reported in patients using soft lenses on a continual basis. The cysts are small, transparent epithelial inclusions. They develop over 2 to 3 months and originate at the deeper layers of the epithelium. They migrate anteriorly. If they reach the surface, they cause a break in the epithelium and stain variably with fluorescein.