Confocal microscopy of corneal sub-basal nerve plexus: a quantitative and qualitative analysis in healthy and pathologic eyes.

PURPOSE To validate corneal sub-basal nerve plexus examination by in vivo corneal confocal microscopy. METHODS Five parameters of corneal sub-basal nerve plexus in 250 human eyes (nerve fiber length, number of fibers, number of beadings, branching pattern, fiber tortuosity) acquired using in vivo corneal confocal microscopy (Confoscan 4.0; NIDEK Co Ltd) were analyzed. The first operator repeated the parameter analysis twice, performing the 2 evaluations 4 weeks apart. The second operator analyzed the cases once. RESULTS Intraoperator reproducibility of nerve fiber length, number of fibers, and number of beadings (intraclass correlation coefficient [ICC] = 0.96, 0.96, and 0.93, respectively) and interoperator reproducibility (ICC = 0.94, 0.95, and 0.87, respectively) were very good. Intraoperator reproducibility for branching pattern was good (ICC = 0.74), whereas interoperator reproducibility was very good (ICC = 0.81). Reproducibility of fiber tortuosity was good both at intra- and interoperator levels (ICC = 0.69 and 0.60, respectively). CONCLUSIONS Corneal confocal microscopy with the NIDEK Confoscan 4.0 represents an in vivo, noninvasive, and reproducible diagnostic technique for the analysis of sub-basal corneal nerve plexus. Methods used to analyze quantitative and qualitative variables were highly reproducible.