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Interstitial
keratitis is chronic, nonulcerative inflammation of the middle layers
of the cornea (ie, mid-stroma) that is sometimes associated with
uveitis. The cause is usually infectious. Symptoms are photophobia,
pain, lacrimation, and vision blurring. Diagnosis is by slit-lamp examination
and serologic tests to determine the cause. Treatment is directed
at the cause and may require topical corticosteroids.
Interstitial keratitis, a manifestation of certain corneal infections, is rare in the US. Most cases occur in children or adolescents as a late complication of congenital syphilis (see Infections in Neonates: Congenital Syphilis). Ultimately, both eyes may be involved. A similar but less dramatic bilateral keratitis occurs in Cogan's syndrome, Lyme disease, and Epstein-Barr virus infection. Rarely, acquired syphilis, herpes simplex, herpes zoster, or TB may cause a unilateral form in adults.
Symptoms and Signs
Photophobia, pain, lacrimation, and vision blurring are common. The lesion begins as patches of inflammation in the middle corneal layers (ie, mid-stroma) that cause opacification. Typically with syphilis and occasionally with other causes, the entire cornea develops a ground-glass appearance, obscuring the iris. New blood vessels grow in from the limbus (neovascularization) and produce orange-red areas (salmon patches). Anterior uveitis and choroiditis are common in syphilitic interstitial keratitis. Inflammation and neovascularization usually begin to subside after 1 to 2 mo. Some corneal opacity usually remains, causing mild to moderate vision impairment.
Diagnosis
The specific etiology must be determined. The stigmas of congenital syphilis, vestibuloauditory symptoms, history of an expanding rash, and tick exposure support a specific etiology. However, all patients should have serologic testing, including all of the following:
Patients with negative serologic test results may have Cogan's syndrome, an idiopathic syndrome consisting of interstitial keratitis and vestibular and auditory deficits. To prevent permanent vestibuloauditory damage, symptoms of hearing loss, tinnitus, or vertigo require referral to an otolaryngologist.
Treatment
Keratitis may resolve with treatment of the underlying condition. Additional topical treatment with a corticosteroid, such as prednisolone 1% qid, is often advisable. An ophthalmologist should be consulted.
Cogan's
Syndrome
Cogan's syndrome
is a rare autoimmune disease involving the eye and the inner ear.
Cogan's syndrome affects young adults, with 80% of patients between 14 and 47 yr. The disease appears to result from an autoimmune reaction directed against an unknown common autoantigen in the cornea and inner ear. About 10 to 30% of patients also have a severe systemic vasculitis, which may include life-threatening aortitis.
Symptoms and Signs
The presenting symptoms involve the ocular system in 38% of patients, the vestibuloauditory system in 46%, and both in 15%. By 5 mo, 75% of patients have both ocular and vestibuloauditory symptoms. Nonspecific systemic complaints include fever, headache, joint pain, and myalgia.
Ocular:
Ocular involvement includes any combination of the following:
Ocular symptoms include irritation, pain, photophobia, and decreased vision. Ocular examination shows a patchy corneal stromal infiltrate typical of interstitial keratitis (see Corneal Disorders: Interstitial Keratitis), ocular redness, optic nerve edema, proptosis, or a combination of these symptoms.
Vestibuloauditory:
Vestibuloauditory symptoms include sensorineural hearing loss, tinnitus, and vertigo.
Vascular:
A diastolic heart murmur may be present with significant aortitis. Claudication may be present if limb vessels are affected.
Diagnosis
Diagnosis is by clinical findings and exclusion of other causes (eg, syphilis, Lyme disease, Epstein-Barr virus infection) by appropriate serologic tests. Evaluation by an ophthalmologist and otolaryngologist is important.
Treatment
Untreated disease may lead to corneal scarring and visual loss and, in 60 to 80% of patients, permanent hearing loss. Keratitis, episcleritis, and anterior uveitis can usually be treated with topical prednisolone acetate 1% q 1 h to qid. To treat deeper ocular inflammation and especially to treat vestibuloauditory symptoms before they become permanent, prednisone 1 mg/kg po once/day is begun as soon as possible and continued for 2 to 6 mo. Some clinicians add cyclophosphamide , methotrexate , or cyclosporine for recalcitrant cases.
Last full review/revision October 2008 by Melvin I. Roat, MD
Content last modified October 2008
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