EPITHELIAL KERATITIS

CHLAMYDIAL KERATITIS

All five principal types of chlamydial conjunctivitis (trachoma, inclusion conjunctivitis, primary ocular lymphogranuloma venereum, parakeet or psittacosis conjunctivitis, and feline pneumonitis conjunctivitis) are accompanied by corneal lesions. Only in trachoma and lymphogranuloma venereum, however, have they been blinding or visually damaging. The corneal lesions of trachoma have been the most studied and are of great diagnostic importance. In order of appearance they consist of (1) epithelial microerosions affecting the upper third of the cornea; (2) micropannus; (3) subepithelial round opacities, commonly called trachoma pustules; (4) limbal follicles and their cicatricial remains, known as Herbert's peripheral pits; (5) gross pannus; and (6) extensive, diffuse, subepithelial cicatrization. Mild cases of trachoma may show only epithelial keratitis and micropannus and may heal without impairing vision.

The rare cases of lymphogranuloma venereum have shown fewer characteristic changes but are known to have caused blindness by diffuse corneal scarring and total pannus. The remaining types of chlamydial infection cause only micropannus, epithelial keratitis, and, rarely, subepithelial opacities which are not visually significant.

Chlamydial keratoconjunctivitis responds to systemic sulfonamides (except for the rare C psittaci infections, which are sulfonamide-resistant), tetracyclines, or erythromycin.

DRUG-INDUCED EPITHELIAL KERATITIS

Epithelial keratitis is not uncommonly seen in patients using antiviral medications (idoxuridine and trifluridine) and several of the broad-spectrum and medium-spectrum antibiotics such as neomycin, gentamicin, and tobramycin. It is usually a superficial keratitis affecting predominantly the lower half of the cornea and interpalpebral fissure and may cause permanent scarring. The preservatives in eyedrops, particularly benzalkonium chloride, are a potent cause of toxic keratitis.

KERATOCONJUNCTIVITIS SICCA (SJÖGREN's SYNDROME)

Epithelial filaments in the lower quadrants of the cornea are the cardinal signs of this autoimmune disease in which secretion of the lacrimal and accessory lacrimal glands is diminished or eliminated. There is also a blotchy epithelial keratitis that affects mainly the lower quadrants. Severe cases show mucous pseudofilaments that stick to the corneal epithelium.

This keratitis of Sjögren's syndrome must be distinguished from the keratitis sicca of such cicatrizing diseases as trachoma and ocular pemphigoid, in which the goblet cells of the conjunctiva have been destroyed. Such cases sometimes still produce tears, but without mucus the corneal epithelium sheds the tears and continues to be dry.

Treatment of keratoconjunctivitis sicca calls for the frequent use of tear substitutes and lubricating ointments, of which there are many commercial preparations. When goblet cells have been destroyed, as in the cicatricial conjunctivitides, mucus substitutes must be used in addition to artificial tears. Topical vitamin A may help to reverse the epithelial keratinization. Moisture chambers or swim goggles may be required. Lacrimal punctal plugs and punctal occlusion are important in the management of advanced cases.

ADENOVIRUS KERATITIS

Keratitis usually accompanies all types of adenoviral conjunctivitis, reaching its peak 5-7 days after onset of the conjunctivitis. It is a fine epithelial keratitis best seen with the slit lamp after instillation of fluorescein. The minute lesions may group together to make up larger ones.

The epithelial keratitis is often followed by subepithelial opacities. In epidemic keratoconjunctivitis (EKC), which is due to adenovirus types 8 and 19, the subepithelial lesions are round and grossly visible. They appear 8-15 days after onset of the conjunctivitis and may persist for months or even (rarely) for several years. Similar lesions occur very exceptionally in other adenoviral infections, eg, those caused by types 3, 4, and 7, but tend to be transitory and mild, lasting a few weeks at most.

Although the corneal opacities of adenoviral keratoconjunctivitis tend to fade temporarily with the use of topical corticosteroids, and although the patient is often made temporarily more comfortable thereby, corticosteroid therapy may prolong the corneal disease and is therefore not recommended. No medication is needed.

OTHER VIRAL KERATITIDES

A fine epithelial keratitis may be seen in other viral infections such as measles (in which the central cornea is affected predominantly), rubella, mumps, infectious mononucleosis, acute hemorrhagic conjunctivitis, Newcastle disease conjunctivitis, and verruca of the lid margin. A superior epithelial keratitis and pannus often accompany molluscum contagiosum nodules on the lid margin.

10.1036/1535-8860.ch6

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