Fragmentation in Bowman Layer: An In Vivo Confocal Microscopy Study

The aim of this study was to study the in vivo ultrastructure of Bowman layer with confocal microscopy in keratoconus patients with a spectrum of disease severity. Fifteen eyes of 12 patients with keratoconus were enrolled in this study. Patients were stratified into 2 severity groups (mild to moderate and advanced) based on maximum keratometry, posterior radius of curvature, and thinnest pachymetry obtained with anterior segment tomography. All study subjects underwent in vivo confocal microscopy (Heidelberg Retina Tomograph III Rostock Cornea Module, Heidelberg Engineering GmbH, Heidelberg, Germany) of the cornea. Seven eyes were classified as having mild-to-moderate keratoconus (mean age 29.14 ± 8.32 years) and 8 eyes were advanced (mean age 31.00 ± 8.62 years). In vivo confocal microscopy showed intact Bowman layer in all eyes with mild-to-moderate keratoconus. Fragmentations in Bowman layer were seen in 20% of eyes (3 eyes) with advanced keratoconus. We did not document ruptures in Bowman layer in mild-to-moderate keratoconus suggesting that Bowman layer fragmentation is a late manifestation of keratoconus and not a sign of early ectatic disease as historically reported.