Diagnostic performance of corneal epithelium- and Bowman’s layer thickness mapping in patients with unilateral Keratoconus

Purpose: To investigate the role of corneal epithelium- and Bowman’s layer-thickness (ET and BLT) changes as possible early biomarkers of keratoconus (KC) development. Methods: In this cross-sectional study patients with unilateral KC (UKC) and a group of healthy controls underwent polarization sensitive optical coherence tomography (PS-OCT) for the evaluation of corneal ET and BLT. These values were compared among three subgroups of eyes, i.e., eyes with KC, topographically and tomographically normal fellow eyes (FE) of patients with UKC, and healthy eyes (HE). Results: Twelve patients with UKC (12 eyes with KC and 12 FE) and 21 healthy age-matched controls (HE) were included. While KC eyes showed the typical epithelial “doughnut pattern” on epithelial maps, there were no differences in ET between FE and HE. BLT was significantly higher in FE compared to HE (average BLT p = 0.049, minimum BLT p = 0.02, nasal-inferior quadrant p = 0.04) as weIl as KC eyes (average BLT p = 0.048, minBLT p = 0.04, nasal-inferior quadrant p = 0.03). Conclusions: Increase in BLT seems to occur before epithelial thinning in FE of patients with UKC. Since many of KC patients develop the disease bilaterally, Bowman’s layer thickening might represent an early biomarker of KC-development.