Interstitial keratitis is chronic, nonulcerative inflammation of the mid-stroma (the middle layers of the cornea) 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 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 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 cause 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.
The specific etiology must be determined. The stigmas of congenital syphilis, vestibuloauditory symptoms, history of an expanding rash, and tick exposure support specific etiologies. However, all patients should have serologic testing, including all of the following:
Patients with negative serologic test results may have Cogan 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 urgent referral to an otolaryngologist.
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 treat these patients.
Cogan syndrome is a rare autoimmune disease involving the eye and the inner ear.
Cogan syndrome affects young adults, with 80% of patients between 14 yr 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 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 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 symptoms include sensorineural hearing loss, tinnitus, and vertigo.
A diastolic heart murmur may be present when aortitis is significant. Claudication may be present if limb vessels are affected.
Diagnosis is based on clinical findings and exclusion of other causes (eg, syphilis, Lyme disease, Epstein-Barr virus infection) by appropriate serologic tests. Urgent evaluation by an ophthalmologist and otolaryngologist is indicated.
Untreated disease may lead to corneal scarring and vision 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 2012 by Melvin I. Roat, MD, FACS
Content last modified November 2012