Evaluation of Contact Lens-Induced Changes in Keratoconic Corneas Using In Vivo Confocal Microscopy

PURPOSE. To quantitatively analyze laser scanning in vivo confocal microscopy (IVCM) images of all corneal layers in contact lens-wearing and noncontact lens-wearing keratoconus patients. METHODS. The study population included rigid gas permeable (RGP) contact lens-wearing keratoconus patients (group 1; N = 29), keratoconus patients who did not wear contact lenses (group 2; N = 30), and subjects who neither had keratoconus nor wore contact lenses (group 3; N = 30), with groups 2 and 3 matched to group 1 by age and sex. The central cornea was examined with IVCM in all subjects. The mean duration of contact lens wear was 5.50 +/- 3.68 years (range, 2-15 years). RESULTS. Eyes with keratoconus showed significantly lower basal epithelial cell and anterior and posterior stromal keratocyte densities, as well as subbasal nerve fiber density, nerve branch density, and nerve fiber length compared with healthy control subjects. Furthermore, compared with group 2, group 1 had significantly lower basal epithelial cell density (4920 +/- 476 cells/mm(2) vs. 4503 +/- 461 cells/mm(2), P = 0.001) and anterior stromal keratocyte density (561 6 91 cells/mm2 vs. 464 6 55 cells/mm2, P < 0.001), but there was no significant difference for posterior stromal keratocyte density (P = 0.808), endothelial cell density (P = 0.699), or subbasal nerve fiber density (P = 0.142), nerve branch density (P = 0.614), and nerve fiber length (P = 0.850). CONCLUSIONS. Significant corneal microstructural abnormalities were observed in eyes with keratoconus. RGP contact lens wear was associated with a further reduction in the basal epithelial cell and anterior stromal keratocyte densities, but with no effect on posterior stromal keratocyte density, endothelial cell density, or corneal nerve morphology.