To correlate in vivo confocal microscopy morphologic features (IVCM-MF) and Acanthamoeba cyst density (ACD) with final best-corrected visual acuity (BCVA) in Acanthamoeba keratitis (AK).

Retrospective cohort study.

Patient demographics, treatment outcome, and corresponding IVCM-MF performed at the acute stage of infection were analyzed. Inclusion criteria were microbiological positive AK cases seen at Moorfields Eye Hospital between February 2013 and October 2017. Statistical significance was assessed by multinomial regression and multiple linear regression analysis. Main outcome measure was final BCVA.

A total of 157 eyes (157 patients) had AK. Absence of single-file round/ovoid objects was associated with a BCVA of 6/36 to 6/9 (odds ratio [OR] 8.13; 95% confidence interval [CI], 1.55-42.56, P = .013) and ≥6/6 (OR 10.50; 95% CI, 2.12-51.92, P = .004) when compared to no perception of light to 6/60. Absence of rod/spindle objects was associated with a BCVA of ≥6/6 (OR 4.55; 95% CI, 1.01-20.45, P = .048). Deep stromal/ring infiltrate was associated with single-file round/ovoid objects (OR 7.78; 95% CI, 2.69-22.35, P < .001), rod/spindle objects (OR 7.05; 95% CI, 2.11-23.59, P = .002), and binary round/ovoid objects (OR 3.45; 95% CI, 1.17-10.14, P = .024). There was a positive association between ACD and treatment duration (β = 0.14, P = .049), number of IVCM-MF (β = 0.34, P = .021), and clusters of round/ovoid objects (β = 0.29, P = .002).

Specific IVCM-MF correlate with ACD and clinical staging of disease, and are prognostic indicators for a poorer visual outcome.