A new in vivo confocal microscopy prognostic factor in Acanthamoeba keratitis

To identify prognostic factors associated with poor outcomes in Acanthamoeba keratitis (AK).

Patients with AK treated at the Beijing Tongren Hospital between January 2008 and January 2012 were included. All patients had corneal scrapings and/or cultures positive for Acanthamoeba and visible cysts on in vivo confocal microscopy (IVCM) examination. Therapeutic penetrating keratoplasty was performed in patients who experienced disease progression or lack of improvement on topical therapy. Patient demographics, clinical characteristics, previous treatment, and IVCM characteristics of the cysts were evaluated. Patients defined as poor outcomes were those requiring therapeutic penetrating keratoplasty. Logistic regression was used to estimate the odd-ratio identifying prognostic factors associated with a poor outcome.

Twenty-nine eyes of 29 patients were diagnosed as having AK over the study period. IVCM showed clusters and/or chains of Acanthamoeba cysts in 9 patients. Fifteen patients underwent therapeutic penetrating keratoplasty. A late-disease stage on presentation, a deep location of cysts, and clusters or chains of cysts observed with IVCM were significantly associated with a worse outcome. On multivariate analysis, only clusters or chains of cysts observed with IVCM were independently associated with a poor prognosis.

The presence of clusters or chains of Acanthamoeba cysts could be a new IVCM criterion allowing the identification of AK patients requiring therapeutic penetrating keratoplasty.