Effect of Diabetes on Central Corneal Thickness, Hysteresis and Optic Nerve Parameters

Abstract

Purpose: : To examine the relationships between central corneal thickness (CCT), cornea hysteresis (CH), and optic nerve parameters in diabetes.

Methods: : Prospective cross-sectional study of controls versus diabetic subjects graded for peripheral neuropathy under an approved UM IRBMED protocol. Bruchs-to-Bruchs distance (BBD), prelaminar nerve fiber layer thickness (PLNFL) and posterior displacement of the lamina cribrosa from Bruchs (PDLC) were measured with enhanced depth imaging (EDI) spectral-domain optical coherence tomography of the optic nerve. CCT was measured by ultrasound pachymetry and CH was measured using the Ocular Response Analyzer. The effect of diabetes on CCT, CH and optic nerve parameters were analyzed.

Results: : Preliminary results from 7 controls, 15 diabetic subjects with none-to-mild neuropathy, and 9 with severe neuropathy showed a high correlation between eyes for CCT (r=0.8, p<0.0001, Pearson correlation). CCT was increased in diabetes (545 μm in controls vs 584 μm in none-to-mild neuropathy, p=0.01, ANOVA and post-hoc test; 545 μm in controls vs 614 μm in severe neuropathy, p=0.0002; 545 μm in mild vs. 614 μm in severe neuropathy; p=0.058). CH was increased in diabetes (8.9 in controls vs 11.1 in mild and 11.4 in severe neuropathy, p=0.05, by ANOVA). There was a larger BBD associated with diabetes status (1388 μm in controls vs. 1525 μm in mild and 1571 μm in severe neuropathy, linear regression of the mean p=0.038), and thinner PLNFL (404 μm in controls vs 288 μm in mild and 223 μm in severe neuropathy). There was also a trend towards greater PDLC in patients with severe peripheral neuropathy (395 μm in controls and 361 μm in mild vs 461 μm in severe neuropathy).

Conclusions: : Our preliminary results corroborate that diabetes is associated with increased CCT. We present preliminary evidence that thickened CCT associated with diabetes has potential functional correlations with ocular biomechanics and structural correlations with optic nerve parameters. Further analysis with additional subjects and more detailed EDI evaluation is warranted.

Keywords: diabetes • optic nerve • cornea: clinical science