Clinical Diagnosis of Infectious Keratitis by Focused Microscopy

To study the clinical diagnosis of infectious keratitis by focusing microscopy. The data and charts of 30 patients were retrospectively analyzed. Four types of structures were observed by confocal microscopy in the HRT type II Rostock corneal model: trophozoites, bimural cysts, charter rings, and bright spots. Thirty patients (mean age 30.8 years, range 17-61 years, 12 males and 18 females) were divided into four groups according to the diagnosis determined by late microscopy, culture, treatment response and course of keratitis. The four groups were infectious keratitis (AK), suspected infectious keratitis (AK-suspect), bacterial keratitis (BK), fungal keratitis (FK). Bright spots were found in 100%, 100%, 40% and 55% of AK, AK-suspect, FK and BK groups, respectively. Under in vivo confocal microscopy, the sensitivity for the presence of bright spots in infectious keratitis was 100% (95% confidence interval [CI] 73.5% - 100.00%) and the specificity was 50% (CI 24.7% - 75.4%). The sensitivity was 67% (95% CI 34) when the only sign of infectivity was bright spot was excluded and only those with cysts, trophozoites, or charter rings were counted. The specificity was 94% (95% CI 69.8% - 99.8%). The relatively high rate of bright spots in noninfectious keratitis challenges the hypothesis that bright spots seen by confocal microscopy are a specific indication of infectious keratitis.