Assessment of Confocal Microscopy for the Diagnosis of Polymerase Chain Reaction–Positive Acanthamoeba Keratitis

In vivo confocal microscopy of the inflamed anterior segment: A review of clinical and research applications

“…On IVCM imaging, acanthamoeba cysts may appear as double‐walled cysts, signet rings and bright spots of less than 30 μm in diameter (Figure ) . However, inflammatory cells also appear as similar bright spots, and thus may easily be confused with acanthamoeba cysts leading to erroneous diagnosis.…”

“…De Craene et al examined 12 different microscopic signs on IVCM images of 50 Acanthamoeba PCR‐positive patients. These were compared with a control group of infectious and immune keratitis that can mimic acanthamoeba keratitis.…”

“…This figure was 98.2% for clusters and 48.2% for bright spots. If the diagnosis of acanthamoeba keratitis was made on presence of target images, clusters or trophozoite images (at least one of the three features), the positive predictive value of confocal microscopy was 87.5% and the negative predictive value was 58.5% …”

“…When excluding the cases where the only signs of Acanthamoeba were the bright spots, and only the cases where cysts, trophozoites, or signet rings were also present were considered, the sensitivity was 67% and the specificity was 94% . The importance of identifying double‐walled cysts, signet rings or trophozoites was further highlighted by De Craene et al who reported that these features are 100% specific for acanthamoeba. Despite their relatively low sensitivity (less than 11%), these features were pathognomonic of the disease …”

“…The importance of identifying double‐walled cysts, signet rings or trophozoites was further highlighted by De Craene et al who reported that these features are 100% specific for acanthamoeba. Despite their relatively low sensitivity (less than 11%), these features were pathognomonic of the disease …”