Abstract
Purpose :
To identify in vivo confocal microscopy (IVCM) cellular features in Acanthamoeba keratitis (AK) at diagnosis.
Methods :
Retrospective observational study of patients aged ≥16 years diagnosed with AK at Manchester Royal Eye Hospital from 2012 to 2018. AK diagnosis made by microbiology, IVCM-positive for double-walled cysts/bright spot sign/trophozoite or signet ring sign by experienced grader, or clinical suspicion of Acanthamoeba with improvement after anti-amoebal treatment. IVCM images were graded for morphological features by 2 ophthalmologists masked to clinical features and microbiological diagnosis. Statistical analysis performed in Stata 13.1, with fisher’s exact test for group comparisons.
Results :
Of the 27 patients included: 41% were male (n=11/27) with median age 29 years (range 16-71 years); 74% were Acanthamoeba culture-positive (n=20/27), 81% were IVCM positive for Acanthamoeba (n=22/27), 16 were both IVCM and culture-positive, 6 were culture-negative but IVCM-positive, and 1 was clinically diagnosed as AK (culture and IVCM negative). The main risk factor was contact lens wear (n=21/21). Median symptom duration at first presentation was 9 days (range 2-42 days), with average BCVA at presentation of logMAR 0.25 (range 0.0-Hand movements). Acanthamoeba appeared in IVCM as bright-spots (86%; 19/22: see image), double-walled cysts (59%; 13/22), signet-ring (23%; 5/22), trophozoites (18%; 4/22) and as lines/clusters in 1 patient. The main epithelial changes detected were: koilocyte appearance with perinuclear halo (64%; 14/22; see image) and hyper-reflective cell borders (59%, 13/22). Nerve beading in basal nerve plexus was observed in 27% (6/22), seen mainly with A. polyphaga (n=5/6, p=0.054). For both, anterior and posterior stroma, activated keratocytes (65%, n=15/23, and 72%, n=8/11, respectively) were the most prominent feature. Microtubules connecting adjacent keratocytes were visible in 52% (n=12/23), and mostly in A. polyphaga (n=8/12, p=0.036).
Conclusions :
Here we report novel IVCM features in AK of koilocyte appearance of epithelial, and microtubules between keratocytes. These may be initial morphological features of AK infection and could be used as an aid for earlier diagnosis. Larger studies are required to evaluate whether these features are specific to AK, and may therefore be clinically useful as diagnostic or prognostic biomarkers.
This is a 2021 ARVO Annual Meeting abstract.