In vivo confocal microscopy appearance of <i>Fusarium</i> and <i>Aspergillus</i> species in fungal keratitis.

Abstract

Clinical outcomes in fungal keratitis vary between <i>Fusarium</i> and <i>Aspergillus</i> spp, therefore distinguishing between species using morphological features such as filament branching angles, sporulation along filaments (adventitious sporulation) or dichotomous branching may be useful. In this study, we assessed these three features within Heidelberg Retina Tomograph 3 in vivo confocal microscopy (IVCM) images from culture-positive <i>Fusarium</i> and <i>Aspergillus</i> spp keratitis participants. Prospective observational cohort study in Aravind Eye Hospital (February 2011-February 2012). Eligibility criteria: age ≥18 years, stromal infiltrate ≥3 mm diameter, <i>Fusarium</i> or <i>Aspergillus</i> spp culture-positive. previous/current herpetic keratitis, visual acuity <6/60 in fellow eye, >80% corneal thinning. IVCM was performed and images analysed for branch angle, presence/absence of adventitious sporulation or dichotomous branching by a grader masked to the microbiological diagnosis. 98 participants were included (106 eligible, 8 excluded as no measurable branch angles); 68 were positive for <i>Fusarium</i> spp, 30 for <i>Aspergillus</i> spp. Mean branch angle for <i>Fusarium</i> spp was 59.7° (95% CI 57.7° to 61.8°), and for <i>Aspergillus</i> spp was 63.3° (95% CI 60.8° to 65.8°), p=0.07. No adventitious sporulation was detected in <i>Fusarium</i> spp ulcers. Dichotomous branching was detected in 11 ulcers (7 <i>Aspergillus</i> spp, 4 <i>Fusarium</i> spp). There was very little difference in the branching angle of <i>Fusarium</i> and <i>Aspergillus</i> spp. Adventitious sporulation was not detected and dichotomous branching was infrequently seen. Although IVCM remains a valuable tool to detect fungal filaments in fungal keratitis, it cannot be used to distinguish <i>Fusarium</i> from <i>Aspergillus</i> spp and culture remains essential to determine fungal species.