Sensitivity and Specificity of Confocal Scan in the Diagnosis of Fungal and Acanthamoeba Keratitis

To determine the sensitivity and specificity of confocal scan in the diagnosis of fungal and acanthamoeba keratitis based on the results of corneal and/or contact lens case smear and culture. Confocal scan and corneal and/or contact lens case smear and culture were performed in all patients with a clinical diagnosis of infectious keratitis who were referred to Labbafinejad Medical Center from 2004 to 2006. A total of 133 eyes of 133 patients (52% male) with mean age of 48.0+22.6 years (range 9-83) were included in the study. Previous history of contact lens wear, ocular trauma and ocular surgery was present in 21%, 21% and 38.3%, respectively. Overall, corneal and/or contact lens case smear and culture were positive in 71 eyes (53.4%) for bacteria (40 cases), fungi (16 cases) and acanthamoeba (15 cases). Confocal scan was positive in 50 cases (37.6%) which revealed hypha-like structures in 27 cases (20.3%) and cyst and/or trophozoite-like structures in 23 cases (17.3%). The sensitivity and specificity of confocal scan were 100% and 84% for diagnosing acanthamoeba keratitis versus 93.4% and 77.8% for diagnosing fungal keratitis, respectively. In vivo corneal confocal scan is a rapid non-invasive tool for the diagnosis of acanthamoeba and fungal keratitis with high sensitivity and specificity based on smear and culture results. It may also be helpful in excluding fungal or acanthamoeba-like structures in cases with negative bacteriological results and in early bacterial keratitis before clarification of microbiologic results.