Approach
Keratitis should be suspected in any patient presenting with eye pain, redness, photophobia, discharge, or reduced vision.
The diagnosis is confirmed if a corneal lesion is seen on slit-lamp examination. Infection is a common cause of keratitis and should be ruled out in all cases.[3][4]
History
Significant components of history include nature and duration of symptoms, preceding eye trauma, past medical history, and past ocular history. It is important to ask about previous eye surgeries, dry eye, poor lid function, trichiasis, periocular skin lesions, and immune status. A complete list of systemic and ocular medications, especially topical corticosteroids and local anesthetics, should be elicited. If the patient is a contact lens wearer, determine lens care regimen and pattern of wear.[4][26]
Physical examination
The first part of the examination must be the measurement of visual acuity of each eye, preferably on a Snellen chart. Next an assessment of pupil function to look for an afferent pupillary defect can be elicited. Following this, a slit-lamp is used to examine both the affected eye and healthy eye. It is important to accurately note and describe any epithelial disease, stromal infiltrate, interstitial keratitis, or endotheliitis. An epithelial defect can be seen easily after staining the cornea with fluorescein. The corneal lesion should be measured in size and the location of the lesion in the cornea should be described. The presence of lid edema, discharge, conjunctival injection, corneal vascularization, corneal thinning, old corneal scars, scleritis, iritis, and hypopyon should be noted. If perforation of the globe is not suspected, intraocular pressure should be measured. If the primary care physician is not able to establish if the globe is perforated, intraocular pressure measurement should be left to the ophthalmologist. Finally, the fundus should be examined. If corneal infection is confirmed, a referral to an ophthalmologist is appropriate for further workup and treatment.
In addition to above history, a thorough review of systems should be obtained to assess any systemic involvement of autoimmune disease. It is important to remember that corneal findings could be the initial manifestation of systemic disease process in up to 25% of the patients who presented with peripheral ulcerative keratitis.[27]
Laboratory tests
Complete blood count may confirm systemic infection or indicate immune compromise. HIV serology is indicated if uncommon infections, such as microsporidiosis, are suspected.[5]
If peripheral ulcerative keratitis is suspected, test for possible underlying disorder (e.g., rheumatoid factor, antineutrophil cytoplasmic antibodies).
Corneal scraping
The corneal ulcer may be scraped by an ophthalmologist with a sterile spatula or blade and the sample sent for smear on microbiology slide and cultures. Polymerase chain reaction techniques can be used to identify the causative organism.[4][5][13]
Negative corneal scraping may indicate noninfectious keratitis (e.g., peripheral ulcerative keratitis, Mooren ulcer, and marginal keratitis).
Referral to an ophthalmologist
Keratitis is best handled by experienced ophthalmologists. While the primary care physician should conduct the initial interview, check vision, and perform a slit-lamp examination if possible, a referral to an ophthalmologist is recommended for further workup and treatment.[4]
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