Utility of In Vivo Confocal Microscopy in Diagnosis of Acanthamoeba Keratitis: A Comparison of Patient Outcomes

Purpose:The aim of this study was to compare outcomes between cases of Acanthamoeba keratitis (AK) diagnosed and treated with or without the use of in vivo confocal microscopy (IVCM).Methods:We performed a retrospective comparative case series of 26 eyes of 23 patients diagnosed with AK at the Massachusetts Eye and Ear Infirmary over a 5-year period. The characteristics of all identified cases were summarized. We compared the time from presentation to diagnosis of AK (primary outcome), visual acuity, and rates of therapeutic penetrating keratoplasty between eyes diagnosed by culture-only group (n = 8) and by IVCM to diagnose AK (n = 9) and later confirmed by culture (IVCM/C group).Results:The diagnostic delay was significantly longer in the culture only group (25 +/- 29 days) compared with the IVCM/C group (3 +/- 3 days, P < 0.01). At 6 months, there was a significant difference in best-corrected visual acuity between the culture-only group (1.46 +/- 1.07, n = 7) and the IVCM/C group (0.22 +/- 0.22, n = 8), after adjusting for initial baseline visual acuity (P = 0.02). Therapeutic penetrating keratoplasty was performed in 50% of culture-only (n = 7) and 11% of IVCM/C group eyes (n = 9), but this was not statistically significant (P = 0.13).Conclusions:IVCM can expedite the diagnosis of AK, and its use as an adjunct tool in the diagnosis of AK may result in better patient outcomes compared with basing treatment decisions on corneal cultures alone.