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A. R. Scheler, E. Spoerl, L. E. Pillunat, A. G. Boehm; Effect of Diabetes on Corneal Biomechanical Parameters. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1761.
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To assess whether the parameters Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF) are altered in diabetic patients compared to healthy subjects and whether these parameters are related to HbA1c- values.
In a prospective clinical trial one randomly chosen eye of 35 healthy subjects and 31 diabetic patients was examined. Diabetic patients were divided into group 1 with HbA1c <7% (n=14) and group 2 with HbA1c ≥7% (n=17). CH and CRF were measured by the Ocular Response Analyzer (ORA), and central corneal thickness (CCT) by ultrasound pachymetry. IOP was evaluated using the Goldmann tonometer (IOPgold), the Pascal Dynamic Contour Tonometer (IOPpasc) as well as the ORA (IOPcc). Additionally, the HbA1c was measured. As CH and CRF are dependent on IOP and CCT these parameters were adjusted according to the following formula: CHcorr=CH-0.2mmHg x (18mmHg-IOPcc)+0.02mmHg x (540µm-CCT) respectively CRFcorr=CRF+0.1mmHg x (18mmHg-IOPcc)+0.02mmHg x (540µm-CCT).
The mean HbA1c-value of healthy subjects (n=35) was 5.44±0.46%, 6.00±0.78% of diabetes patients group 1, and 8.58±2.44% of diabetes patients group 2. Healthy subjects were statistically significant lower compared to diabetic group 2 in CHcorr (P=0.031) and CRFcorr (P=0.029). Additionally IOPpasc (P=0.012), IOPgold (P=0.032), and HbA1c-level (P=0.0001) were statistically significant different, but not age, sex, and CCT. There was no statistically significant difference between the healthy subjects and the diabetes patients of group 1 in CHcorr (P=0.071) and CRFcorr (P=0.067). Over all diabetic patients (n=31) CHcorr (P=0.012; R²=0.197) and CRFcorr (P=0.008; R²=0.217) were dependent on HbA1c. In the healthy subjects CHcorr (P=0.931; R²= 0.0001) and CRFcorr (P=0.837; R²=0.001) were not dependent on HbA1c.
CHcorr and CRFcorr are significantly higher in poor controlled diabetes and show a significant correlation to the current HbA1c-value. This suggests that the biomechanical properties of the cornea are altered in diabetes mellitus.
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