Observations of banding patterns (Vogt striae) in keratoconus: a confocal microscopy study

PURPOSE: To investigate Vogt striae in keratoconus using confocal microscopy. METHODS: The central cornea of 51 eyes of 29 subjects with keratoconus was observed using a slit-lamp biomicroscope, slit-scanning confocal microscope (TOMEY Confoscan 1), and corneal topographer (EyeSys 2000). RESULTS: Alternating dark and light bands were seen in the stromal images of 23 eyes examined. The bands corresponded with the appearance of Vogt striae on slit-lamp biomicroscopy examination. Bands were found most commonly in the posterior stroma. Posterior bands varied in width, ran mainly in a nearly vertical direction, and appeared to run a straight course through individual image frames. Keratocyte nuclei were located in between the bands. Posterior keratocyte density was unaffected by the presence of bands. Nerve fibers appeared to run a straight course through the bands. When present, bands in the anterior stroma showed greater variability in width and direction within a single frame. Bands were only present in the anterior stroma in more severe levels of keratoconus. The difference in banding pattern noted between the anterior and posterior stroma parallels the known collagen fiber arrangement in the anterior and posterior stroma. CONCLUSIONS: The bands apparent on confocal microscopy of the stroma of the keratoconic cornea correspond with Vogt striae on slit-lamp microscopy. It appears that these bands (and hence Vogt striae) represent collagen lamellae under stress. The stress pattern appears to radiate from the center of the cone and is consistent with the direction of striae when viewed with the confocal microscope.