Abstract
Purpose To investigate the central thickness of Bowman’s layer in patients with keratoconus, healthy cornea and other corneal conditions in relation to corneal curvature and, epithelial and total corneal thickness in health, keratoconus (KC) and Fuchs’ endothelial corneal dystrophy (FED).
Methods Patients with keratoconus, FED and other dystrophies, and healthy subjects were included. Linnik and Mirau ultra high axial resolution line field spectral domain optical coherence tomography (UHR-OCT) devices were used to image the cornea, in addition to commercially available OCT and Scheimpflug devices. Measurements were undertaken in triplicate for each device at entry and then repeated at 3 and 6 months. A supervised automated segmentation process was used to extract the quasi-point thickness of the Bowman’s layer in the central cornea from the collected UHR-OCT images.
Results 37 patients with KC, 33 with FED and other corneal dystrophies and 18 healthy subjects were included. Central BT 14.32uM (SD:1.66) in KC, 15.45 (SD 1.88) in health and 15.20 (1.42) in FED. Central Bowman’s layer thickness, was associated with CCT (p<0.001 Bowman’s layer being ~3% of measured CCT), but not with age (p=0.25), diagnosis (p=0.81), sex (p=0.18), Kmax (p=0.37) or epithelial thickness (p=0.79). The ratio of BT to CCT was independent of diagnosis (p=0.85), age (p=0.72), sex (p=0.21) Kmax (p=0.53) and epithelial thickness (p=0.93). There was a significant association between epithelial thickness and the ratio of Kmax to CCT (R2=0.63, p<0.001).
Conclusions Changes to Bowman’s layer appear to be concurrent with changes in the corneal stroma. The ratio of BT to CCT is independent of age, sex, Kmax, epithelial thickness or diagnosis and may be a useful index.
