a study of the spectrum of acanthamoeba keratitis: a three-year study at a tertiary eye care referral center in south india

Purpose: To determine the epidemiological and clinical characteristics of Acanthamoeba keratitis and also to determine the sensitivity and specificity of smears in the detection of Acanthamoeba . Materials and Methods: A retrospective review of all culture-positive cases of Acanthamoeba keratitis seen between October 1999 and August 2002 was performed. Corneal scrapes were subjected to culture and microscopy using standard protocols. Results: Out of 3183 consecutive patients with clinically diagnosed corneal ulcers evaluated, 33 (1.04%) were found to be due to Acanthamoeba . Twenty-four out of 33 (72.72%) were less than 51 years of age ( P < 0.001). All patients were from rural areas ( P < 0.001) and 26 (78.79%) of them were agricultural workers ( P = 0.031). All 33 had history of corneal injury ( P < 0.001) and 28 (84.85%) patients had injury with mud ( P < 0.001). All 33 (100%) patients had previous medical treatment ( P =0.009) and 10 (30.3%) had used traditional eye medicines ( P =0.183). A clinical pattern of ring infiltrate was characteristic in 15 (45.45%) patients. The diameter of the corneal ulcer was more than 6mm in 27 (81.82%) eyes ( P < 0.001). Twenty-six (78.79%) patients had visual acuity of perception of light on initial presentation ( P < 0.001) and 24 (72.73%) had the same as their final visual outcome. The sensitivity of 10% potassium hydroxide (KOH) preparation was found to be higher ( P < 0.001) in the detection of Acanthamoeba cysts. Conclusion: The incidence of Acanthamoeba keratitis amongst the corneal ulcer patients was 1% in this setting and it was mainly due to corneal injury by mud. The KOH preparation is a sensitive diagnostic tool for the detection of Acanthamoeba . Delayed diagnosis or misdiagnosis and inappropriate antimicrobial therapy results in poor visual outcome.