Interstitial Keratitis Overview

Study Notes

Interstitial keratitis is a condition characterized by ulcerating vascular inflammation of the cornea's stroma.
It can lead to severe vision impairment and potential blindness.
Treatment, if administered early and appropriately, can be effective.

Congenital syphilis is a possible etiology, accounting for a proportion of bilateral cases.
Acquired syphilis, together with HSK (hypopyon-uveitis-keratitis), can also result in interstitial keratitis.
Unilateral interstitial keratitis is often associated with acquired syphilis.
Segmental involvement tends to be more likely in unilateral cases.

Posterior stromal scarring is a defining feature.
Presence of blood vessels should be noted
Distinction between superficial and deep blood vessel patterns is clinically significant.

Initial symptoms include pain, tearing, and photophobia, along with perilimbal injection.
Early signs often include sectoral superior stromal inflammation and the presence of keratic precipitates (KP).
Late signs might involve deep potassium vascularization, which can progress to intense corneal pink coloration.
Eventually, keratic scarring, ghost vessels, vision loss (reduced visual acuity), and irregular astigmatism or stromal opacification may be observed.

Ghost vessels are characterized by the presence of clearer lines, revealing the locations of former blood vessels within the cornea.

Salmon patch (deep stromal neovascularization) is frequently observed in association with interstitial keratitis associated with syphilis.

Deep stromal scarring and ghost vessels are diagnostic features
Cases involving seropositive adults and prior bilateral keratitis during childhood are examples

Dental deformities, including issues involving the CN VIII (vestibulocochlear) nerve.
Bone and cartilage abnormalities present in the form of saddle nose, saber shins, and frontal bossing.
Cognitive impairment is another potential complication.

Most cases manifest within the first two years of a child's life. This can also be seen through a later onset of an immune-mediated manifestation in a later decade.

Rare but possible causes include mycobacterium tuberculosis, mycobacterium leprae, Borrelia burgdoferi (Lyme Disease), measles, Epstein-Barr virus (infectious mononucleosis), Chlamydia trachomatis, leishmaniasis, and onchocerciasis.

Onchocerca volvulus is a nematode that can cause blindness, targeting human hosts.
Simulium blackfly is a vector.
Treatment involves ivermectin every six months and potential adjunct doxycycline.

Cogan syndrome is a rare autoimmune disorder affecting young adults
The syndrome often includes stromal keratitis (treated with topical steroids), vertigo, hearing loss, and urgent treatment with oral prednisolone and a systemic vasculitis component (e.g. polyarteritis nodosa).