Alcaine

Differentiating between infectious keratitis and contact lens overwear.

As we've fit more patients with frequent replacement contact lenses, the serious problems associated with longerduration lens wear have decreased. However, even with frequent replacement, contact lens complications can arise. One of our most important jobs is determining whether these problems are infectious and whether they're caused by contact lens overwear. This case will illustrate some crucial steps in making the clear distinction.

THE CASE: Matthew was a friendly 17-year-old who'd been wearing soft contact lenses for 4 years. When he developed discomfort with his right lens, his aunt, who works for me, told him to come to my office.

I'd never examined Matthew before, but he told me he was fitted with disposable lenses at age 14 and had never had trouble wearing them. He said he was told he could sleep in them for 1 week, remove them for 1 night and then wear them for 1 more week before disposing of them. He also said that he was "pretty good" about sticking to this schedule.

Matthew added that the day before, his right eye suddenly began to hurt. When he looked in the mirror, this eye was red and swollen. He removed the old contact lens and put a new one in, but the situation didn't improve. In fact, the eye was sorer this morning, and now Matthew was sensitive to light. I detected no pus or mucus discharge, but the eye was tearing. Matthew still had his contact lens in when I saw him because the eye felt somewhat better with the lens than without. Before the problem started, he'd had no awareness of the lenses in his eyes.

Matthew's visual acuity with his contact lenses was 20/30 OD and 20/20 OS. His pupils were equally round and reactive. I found no evidence of extraocular muscle restriction.

Matthew didn't appear to be in much pain until my assistant removed the contact lens from his right eye. Almost immediately, tearing increased and the eye closed on reflex. We instilled a drop of 0.5% proparacaine (Alcaine) in the eye, which let Matthew keep it open and me more easily examine it.

A closer look

Slit lamp examination of the right eye showed diffuse bulbar conjunctival injection with no follicles or papillae on the palpebral conjunctiva. The cornea appeared to be fine. I saw no haze or edema until I raised the eyelid. A whitish opacity was apparent on the superior cornea. There was also engorgement of the superior limbal vessels, but no corneal neovascularization. I saw trace cells in the anterior chamber, but no flare.

Instilling sodium fluorescein (NaF1) dye gave me a better appreciation of the corneal lesion. The center stained positively, illustrating a small but frank ulceration. Surrounding the lesion was a ring of stromal edema.

The left eye was normal. There was no limbal vascular encroachment or corneal lesion, and the contact lens showed good coverage and movement.

Matthew had a corneal ulcer Before initiating treatment, I had to determine if the ulcer was sterile or infectious.

DISCUSSION: Contact lenses can increase the chances of ocular infection. Soft lenses, more than others, can harbor bacteria that adhere to their surfaces and become integrated into the matrix. These bacteria typically don't affect an intact cornea, but when the cornea's structural integrity is breached, they have a portal of entry. Lenses can mechanically abrade tissue or cause hypoxia. Hypoxia causes corneal cell death and epithelial breakdown. So a "sterile" hypoxic condition can become infectious if untreated. Contact-lensinduced edema also provides an avenue for corneal penetration.

Symptoms of a contact lensrelated infection are redness, pain, foreign body sensation and lens discomfort. In severe cases, patients complain of decreased visual acuity, photophobia and a purulent discharge. Upon examination you'll notice bulbar injection, focal corneal infiltrates (with or without an overlying epithelial defect) and limbal vascular engorgement. Iritis may also be present.

Usually, the more severe the signs and symptoms, the more severe the condition. But because of its size and restricted movement, a soft contact lens can mask corneal symptoms.

Corneal infiltrates represent an influx of polymorphonuclear leukocytes (PMNs) and other inflammatory cells migrating from the limbal vessels in response to an inflammatory stimulus. A study by Adam Gordon, O.D., MPH, and Gregory Kracher, O.D., showed that contact lens-related infiltrates had clinical characteristics that can help us in making a diagnosis.

The authors found that 93% of all such infiltrates were peripheral. Sixty-seven percent were found in the superior cornea beneath the upper lid, a hypoxic environment because oxygen doesn't penetrate the lid. This study showed that nearly all patients resumed contact lens wear after resolution of an infiltrate problem, but only on a daily wear basis.

A full recovery

Although this ulcer was superiorly located and peripheral, the frank epithelial break and iritis made me believe the infiltrate had become infected. I treated Matthew aggressively by instilling 1 drop of homatropine 5% to quiet the anterior chamber I prescribed ofloxacin (Ocuflox) 1 drop q1h OD. I also insisted that Matthew discontinue contact lens wear in both eyes.

The next day, Matthew's eye was markedly improved. The iritis, redness and discomfort were gone. Though the infiltrate was still present, it no longer stained with NaF1. I decreased the ofloxacin to q4h OD for 3 days, then added

fluorometholone (eFLone) q.i.d. to help clear the infiltrate.

After 15 days, the infiltrate was cleared, and I tapered the steroid and then discontinued the ofloxacin. Matthew was refit with 1-day disposable contact lenses and my staff stressed the need for proper compliance. His visual acuity continues to be 20/20 with contact lenses.

Matthew recovered completely, but his condition could've been serious. Remember: Contact lenses are medical devices. Both you and your patient must treat them as such.

CLINICAL PEARLS

Corneal infiltrates in contact lens wear can range from a minor nuisance to a potentially sight-threatening problem. Use these tips for guidance.

Sterile infiltrates occur more often than infectious keratitis. The cornea usually has an intact epithelium or a small defect.

Check the eyelids. Look for blepharitis; staphylococcal exotoxins can cause sterile peripheral infiltrates. Staphylococci are normally present on the eyelid margin. However, proliferation of these bacteria will often cause the exotoxins to produce the various signs and symptoms of this condition.

Check for the early signs of contact lens overwear. They include:

excessive haze upon waking

limbal vascular engorgement

a stinging sensation when the contact lenses are removed.

Ask the patient to describe his or her wearing schedule. This will often provide clues to overwear.

Topical steroids can be helpful in treating these cases, but only when the epithelium is intact.

When in doubt, treat the problem as infectious.

Contributing Editor Eric Schmidt, O.D., is Director of the Bladen Eye Center in Elizabethtown, N.C.

Copyright Boucher Communications, Inc. Apr 1999
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