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S. A. Kondapalli, C. J. Roberts, A. Mahmoud, P. A. Weber, J. Peterson; The Effect of Diabetes on Biomechanical Properties of the Cornea. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4631.
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Diabetes mellitus (DM) has been found to have a protective effect against progression of ocular hypertension to primary open angle glaucoma. We investigated the possibility that the protective effect is secondary to biomechanical stiffening of the cornea secondary to non-enzymatic collagen glycosylation, by evaluating the effect DM has on the biomechanical properties of the cornea in vivo.
Subjects (n=18) with DM type I and II were recruited from an ophthalmology clinic. Patients with previous eye trauma, invasive eye surgery, corneal edema or corneal disease were excluded. The patients age, race, how many years they have had diabetes and their blood glucose control were recorded as reported by the patient. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with the Reichert Ocular Response Analyzer (ORA). Also, ORA infrared (IR) and pressure signals were recorded and analyzed with custom software to extract the height of the first and second IR waveform peaks (peak 1 and 2), which have been reported as an indication of corneal stiffness. Subjects (n=18) from an ongoing study of the normal aging population were age matched and recorded as controls. T-tests were used to compare groups.
Diabetic subjects, eleven of whom were female, had a mean age of 51+14.5; controls had a mean age of 50+11.3 with ten females. By analyzing the waveform data, the diabetic group was noted to have a significantly greater (p<0.0001) peak 1 mean of 808.2±111.4 than the non-diabetic group peak 1 mean of 642.9±96.9. Peak 2 analysis indicated that diabetic group average of 645.4±155.3 was significantly greater (p=0.0005) than the non-diabetic group average of 484.8±109.3. No significant differences were found in CH and CRF values between groups, with the diabetic mean CH of 10.52+1.61 and non-diabetic mean of CH of 10.69+1.77 (p= 0.77). The diabetic mean CRF was 10.62+1.67 while non-diabetic mean CRF was 10.98+1.6 (p= 0.77).
In this preliminary study, our data indicate that diabetic corneas are biomechanically "stiffer" than non-diabetic corneas based on peak 1 and peak 2 analysis, which may be a factor in the sparing of diabetic eyes from developing glaucoma. Additionally the difference in corneal stiffness was not detected by the viscoelastic properties CH and CRF, indicating the importance of waveform analysis. Future work includes increasing the number of subjects, examining the role of race in diabetic corneas, as well as investigating the relationship between length of time having a diabetes diagnosis and stiffness of the cornea.
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