The measurement of corneal epithelial thickness in response to hypoxia using optical coherence tomography

PURPOSE: To determine if corneal epithelial thickness increases in association with corneal edema induced by wearing soft contact lenses during eye closure. DESIGN: Experimental study. METHODS: One eye (randomly selected) of twenty noncontact lens wearers (10 males and 10 females, age 35.6 ± 9.6 years) was patched during 3 hours of soft contact lens (SCL) wear and the contralateral eye acted as a control. Corneal and epithelial thickness of both eyes was measured before and after SCL wear using optical coherence tomography (OCT). RESULTS: Immediately after contact lens removal, total corneal thickness was increased significantly by 13.8 ± 2.3% (mean ± SD) compared with baseline (P < .0001, paired t test) and after 100 minutes was still 4.5 ± 2.3% thicker than baseline (P < .0001, paired t test). The control eyes showed no change in total corneal thickness (P > .05, paired t test). Immediately after contact lens removal, corneal epithelial thickness was increased by 1.7 ± 4.8%, but this change was not statistically significant (P > .05, paired t test). Following contact lens removal, epithelial thickness changed significantly (Repeated measure analysis of variance [Re-ANOVA]: F_(7,133) = 4.91, p_H-F < 0.001) over the next 100 minutes with thinning recorded at 60, 80, and 100 minutes (P < .05, paired t test). There was no significant change over time in epithelial thickness of the control eyes (Re-ANOVA: F(4, 76) = 0.91, p_H-F = 0.464). CONCLUSION: OCT demonstrated that corneal epithelial thickness does not increase in response to hypoxia from SCL wear and eye closure, in contrast to a significant increase in total corneal thickness.