Use of lactophenol cotton blue mounts of corneal scrapings as an aid to the diagnosis of mycotic keratitis

Abstract

Lactophenol cotton blue (LPCB) mounts of corneal ulcer scrapings were assessed as a diagnostic tool in cases of mycotic keratitis over a period of 15 months. We investigated 568 cases of ulcerative keratitis by microbiological techniques consisting of direct microscopic examination of LPCB mounts and Gram-stained smears as well as culture of material scraped from the ulcer. Fungi were isolated in large numbers on multiple media from the corneal scrapings of 179 patients (culture-proven mycotic keratitis). Direct microscopic examination of LPCB mounts of corneal scrapings yielded positive results in 140 (78%) of 179 culture-positive patients and negative results in 371 (95%) of 389 culture-negative patients. There was a significant difference between the percentage of positive results obtained by LPCB mounts and by Gram-stained smears in the culture-positive cases. The LPCB mount was positive in >80% of cases of keratitis due to Fusarium spp. and Aspergillus spp. The LPCB mount is strongly recommended as a simple, rapid, inexpensive, and sensitive diagnostic technique in cases of mycotic keratitis.