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To determine whether corneal hysteresis (CH) and corneal resistance factor (CRF) are altered in diabetes and whether these parameters are related to HbA1c.One randomly chosen eye of 35 healthy subjects and 31 patients with diabetes was examined. Patients with diabetes were divided into group 1 with HbA1c <7% (n= 14) and group 2 with HbA1c ≥7% (n= 17). CH and CRF were measured using ocular response analyzer (ORA); central corneal thickness (CCT) using ultrasound pachymetry; increased intraocular pressure (IOP) using Goldmann tonometer (IOPGAT), Pascal dynamic contour tonometer (IOPpasc), and ORA (IOPcc). As CH and CRF are dependent on IOP and CCT, they were adjusted for IOP and CCT resulting in CHcorr and CRFcorr.Mean HbA1c was 5.44 ± 0.46% in healthy subjects, 6.00 ± 0.78% in diabetic group 1, 8.58 ± 2.44% in group 2. CHcorr (p = 0.071) and CRFcorr (p = 0.067) were not statistically significantly different between healthy subjects and diabetic group 1, but significantly lower in healthy subjects compared to diabetic group 2 [CHcorr (p = 0.031), CRFcorr (p = 0.029)]. IOPpasc (p = 0.012), IOPGAT (p = 0.032) and HbA1c (p = 0.0001) were statistically significantly different between healthy subjects and all patients with diabetes (groups 1 + 2), but not age, sex and CCT. Over all patients with diabetes, CHcorr (p = 0.012,R2 = 0.197) and CRFcorr (p = 0.008,R2 = 0.217) were correlated to HbA1c but not in healthy subjects [CHcorr (p = 0.931,R2 = 0.0001), CRFcorr (p = 0.837,R2 = 0.001)].In poorly controlled diabetics, CHcorr and CRFcorr are significantly higher compared with those of the healthy subjects and patients with well-controlled diabetes. In diabetes, CHcorr and CRFcorr are correlated to HbA1c, suggesting that the biomechanical properties of the cornea are altered depending on the glucose control.