Role of in vivo confocal microscopy in the diagnosis of infectious keratitis.

Purpose: To investigate the utility of in vivo confocal microscopy (IVCM) in the diagnosis of infectious keratitis (IK).

Methods: Retrospective chart review of 46 patients with a final diagnosis of IK were included in the study. All patients received IVCM corneal imaging using the Heidelberg Retinal Tomography III system. All available scans were randomized and analyzed in a masked fashion. Sensitivity and specificity of IVCM in diagnosing bacterial keratitis (BK), Acanthamoeba keratitis (AK), fungal keratitis (FK), and HSV viral keratitis (VK) were assessed.

Results: The pooled sensitivity and specificity of IVCM in identifying atypical IK (AK and FK cases combined) were 85.3% (95% CI 68.2-94.5%) and 100% (95% CI 74.7-100%), respectively. The sensitivity and specificity of IVCM in identifying BK were 66.7% (95% CI 35.4-88.7%) and 89.2% (95% CI 73.4-96.5%), respectively. The sensitivity and specificity of IVCM in identifying VK were 100% (95% CI 46.3-100%) and 93.2% (95% CI 80.3-98.2%). Additionally, IVCM was able to make the correct diagnosis in 8 out of the 11 atypical keratitis cases misdiagnosed clinically. In the AK subgroup, IVCM was more accurate than clinical assessment (16 vs. 11). In the FK subgroup, IVCM were as accurate as clinical assessment, but did correct one misdiagnosed cases by identfying fungal hyphae.

Conclusion: IVCM is an non-invasive imaging modality that can rapidly and accurately diagnose IK even for experienced corneal specialists. In complex cases of polymicrobial infection, IVCM may guide the correct clinical diagnosis and initiation of the appropriate treatment.