In vivo confocal microscopy: corneal changes of hydrogel contact lens wearers

To evaluate the corneal findings in hydrogel contact lens wearers by in vivo confocal scanning microscopy. One hundred and forty-two eyes of 71 myopic contact lens wearers (group 1) and 142 eyes of 71 non-contact lens wearers (group 2), whose age, gender and refractive error matched, were enrolled in order to detect the corneal changes by in vivo confocal microscopy through the central cornea. The average age was 25.5 ± 5.7 (16–52) and 25.6 ± 5.6 (17–49) in groups 1 and 2, respectively. The mean duration of contact lens wear was 43.9 ± 15.3 (6–240) months. Anterior keratocyte density was 667.5 ± 128.3 cells/mm² in group 1 and 821.4 ± 136.7 cells/mm² in group 2 (P = 0.001). Posterior keratocyte densities of groups 1 and 2 were 540.2 ± 87.6 cells/mm² and 628.2 ± 72.4 cells/mm², respectively (P < 0.001). Endothelial cellular density was 2611.2 ± 298.4 cells/mm² in group 1 and 2643 ± 218.2 cells/mm² in group 2 (P = 0.52). Ratio of polymegethism was 44.6 ± 8.8% in group 1 and 31.3 ± 4.7% in group 2 (P < 0.001). Epithelial cellular enlargement was observed in eyes wearing contact lenses with a mean Dk/t ratio of 26.5 × 10⁻⁹ ± 5.9 (8.9–32 × 10⁻⁹). Stromal microdots occurred with contact lenses with a mean Dk/t ratio of 13.2 × 10⁻⁹ ± 17.5 × 10⁻⁹ (8.9–20 × 10⁻⁹). In vivo examination of the cornea with confocal microscopy revealed a number of changes. These changes can be attributed both to the mechanical and the hypoxic effects of soft contact lenses. In soft contact lenses with a high Dk/t ratio, these changes would be less frequent.