Laser scanning in vivo confocal analysis of keratocyte density in keratoconus.

PURPOSE: Keratoconus is a form of progressive noninflammatory corneal ectasia. Although abnormalities have been documented at every level of the keratoconic cornea, the exact underlying pathophysiologic process remains unknown. This study aimed to determine the keratocyte density in human corneas with keratoconus imaged by laser scanning in vivo confocal microscopy.

DESIGN: Prospective cross-sectional study.

PARTICIPANTS: Thirty-six eyes of 26 subjects with keratoconus compared with 33 eyes of 33 control subjects.

METHODS: Subjects were assessed via ophthalmic examination, computed topography, and laser scanning in vivo confocal microscopy.

MAIN OUTCOME MEASURES: Anterior and posterior stromal keratocyte density.

RESULTS: Mean age was 34.7+/-12.1 years in the control group, 38.4+/-11.0 years in the keratoconic with no contact lens wear group, and 38.5+/-10.3 years in the keratoconic with contact lens wear group. No significant difference was noted in age or gender between the groups. Mean keratocyte density in the control group was 786+/-244 cells/mm(2) in the anterior stroma and 293+/-35 cells/mm(2) in the posterior stroma. Anterior keratocyte density was higher than posterior keratocyte density (P<0.001). Anterior keratocyte density was significantly lower in contact lens-wearing keratoconic subjects in comparison with controls (463 vs. 786 cells/mm(2); P<0.001). Posterior keratocyte density was significantly lower in keratoconic subjects with no contact lens wear (236 vs. 293 cells/mm(2); P<0.001) and in keratoconic subjects with contact lens wear (208 vs. 293 cells/mm(2); P<0.001). In subjects with keratoconus, anterior keratocyte density correlated with central corneal thickness (r = 0.426, P = 0.012) and inversely with steepest keratometry values (r = -0.383, P = 0.028).

CONCLUSIONS: Keratocyte density is significantly lower in subjects with keratoconus, and the decline in keratocyte density correlates with indices of disease severity. In vivo confocal microscopy offers the opportunity to study early microstructural changes in the keratoconic cornea.