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Describe interstitial keratitis with its causes and management.

Ophthalmology · 3rd Professional

Interstitial keratitis is a non-ulcerative inflammation of the corneal stroma, with the epithelium and endothelium intact, characteristically accompanied by deep stromal vascularisation.
It is an immune response to a microbial antigen, not a direct infection of the cornea.

Cause	Features
Congenital syphilis	Historically the commonest cause, accounting for the great majority of cases. Bilateral, appearing between 5 and 20 years, and part of the hutchinson triad — interstitial keratitis, hutchinson’S teeth (peg-shaped, notched upper central incisors) and eighth nerve deafness. Other stigmata: saddle nose, frontal bossing, rhagades, sabre tibia and Clutton joints
Acquired syphilis	Unilateral, sectoral, and milder
Tuberculosis	unilateral and sectoral, affecting the lower cornea; an important cause in India
COGAN’S syndrome	Non-syphilitic interstitial keratitis with vestibulo-auditory symptoms — tinnitus, vertigo and progressive deafness. An autoimmune vasculitis; the deafness becomes permanent unless systemic steroid is given promptly, so it is an emergency of hearing rather than of sight
Others	Leprosy; onchocerciasis; Lyme disease; herpes simplex and zoster (the commonest cause of unilateral interstitial keratitis today); mumps; measles; and Epstein-Barr virus

Acute (progressive) stage — 2 weeks: pain, photophobia, lacrimation and blepharospasm; ciliary congestion; and a diffuse or sectoral stromal haze with cellular infiltration, giving a ground-glass appearance.
Associated anterior uveitis with keratic precipitates → florid (vascularisation) stage — 2 months: deep stromal vessels grow in from the limbus.
Because they lie in the deep stroma and are seen through a hazy cornea, they appear as a dull reddish-pink patch — the salmon patch of hutchinson, which is characteristic → The cornea may become so opaque and vascularised that the iris cannot be seen → regressive stage — 1 to 2 years: the inflammation subsides, the haze clears from the periphery inward, and the vessels empty → healed stage: the vessels remain as empty, non-perfused ghost vessels, which are pathognomonic of past interstitial keratitis and persist for life; with variable stromal scarring, thinning and irregular astigmatism

All questions in Diseases of the Cornea