Sensitivity and specificity of confocal scan in the diagnosis of infectious keratitis

Abstract

Purpose: To compare the sensitivity and specificity of confocal scan with the results of corneal and/or contact lens case smear and culture in the diagnosis of infectious keratitis.

Methods: This was a diagnostic test study. Confocal scan and corneal and/or contact lens case smear and culture were performed in all patients with a clinical diagnosis of infectious keratitis at Labbafinejad Medical Center from 2004 to 2006.

Results: A total of 133 eyes of 133 patients with a mean age of 48.0 +/- 22.6 years (range, 9-83 years) were included in the study. Sixty-nine (51.9%) cases were men, and 64 (48.1%) were women. Twenty-eight cases (21%) were contact lens wearers; history of trauma and previous ocular surgery was present in 21% and 38.3%, respectively. Corneal and/or contact lens case smear and culture were positive in 71 eyes (53.4%), including 40 cases of bacterial, 16 cases of fungal, and 15 cases of acanthamoeba infection. Confocal scan was positive in 50 cases (37.6%), which revealed hyphae-like structures in 27 cases and cyst and/or trophozoite-like structures in 23 cases. The sensitivity and specificity of confocal scans were 100% and 84% for the diagnosis of acanthamoeba keratitis versus 94% and 78% for fungal keratitis, respectively.

Conclusions: In vivo corneal confocal scan is a rapid noninvasive tool for the diagnosis of acanthamoeba and fungal keratitis with high sensitivity and specificity compared with smear and culture. It may also be helpful in excluding fungal or acanthamoeba-like structures in cases with negative bacteriologic results and in early bacterial keratitis before clarification of microbiologic results.