Associate Professor of Ophthalmology The Effects of Age and Diabetes on Corneal Hysteresis and Corneal Resistance Factor Irene C. Kuo, MD Associate Professor of Ophthalmology Wilmer Eye Institute The authors have no financial interest in the subject matter of this poster Kuo, Boston 2010

Co-authors Jonathan Tzu, MD Alisa Kim, MD Aimee T. Broman, MA

Introduction As viscoelastic tissue, cornea can be described by static resistance component and dynamic resistance component Ocular Response Analyzer (ORA, Reichert Ophthalmic Instruments, NY) measures intraocular pressure and corneal hysteresis, presumably measure of dynamic component. Kuo, Boston 2010

Introduction Aldehydes can induce enzymatic cross-linking Moreover, our group has found a negative association between diabetes (DM) and keratoconus (Kuo et al, Ophthalmology 2006) Other groups have reported that diabetic patients have higher corneal hysteresis (Hager et al, Graefes Arch Clin Exp Ophthalmol 2009; Goldich et al, J Cataract Refract Surg 2009) Kuo, Boston 2010

Purpose Does diabetes have an effect on corneal hysteresis measurements (CH) and corneal resistance factor (CRF) in patients seen in a glaucoma clinic, where measurements using the ORA were obtained as part of a previous study? Kuo, Boston 2010

Patients and Methods consecutive patients seen in Glaucoma Clinic between 12/2/03 and 8/25/04 Hysteresis measurements were obtained on pts aged 18 and over who had not had surgery in prior 90 days Hypothesis: CH is predicted by age, gender, race, central corneal thickness (CCT), edema, DM Kuo , Boston 2010

Statistical Methods Each eye was measured twice by ORA, and average was recorded CH was modeled in multiple regression model with age, gender, age, DM status, CCT, and edema. Measurements for each eye were entered in the regression Generalized Estimating Equations were used to account for correlation between eyes Kuo , Boston 2010

Results 452 eyes of 228 pts 56% were female 34 (15%) patients were diabetic No difference between diabetic and nondiabetic patients in age or sex CH was 0.69 mm Hg and CRF was 0.94 mm Hg in diabetic pts than in non-diabetic pts (p=0.02 and p=0.01, respectively), adjusting for age, gender, CCT, and edema Kuo, Boston 2010

Table 1 Predictors of corneal hysteresis measurements, using multiple regression with repeated measures; correlation between eyes was 0.37. Kuo, Boston 2010

Table 2 Predictors of corneal resistance factor measurements, using multiple regression with repeated measures. Kuo, Boston 2010

Conclusions Diabetic pts in a glaucoma clinic had higher CH and CRF than did non-diabetic pts, adjusting for age, race, gender, CCT, and corneal edema Results may reflect changes in corneal structure and biomechanics as a result of collagen cross-linking induced by hyperglycemia There was no association between DM and CCT Age was associated with decreased CH Kuo, Boston 2010

Conclusions Age and DM induce changes in corneal biomechanical properties, but had opposite effects on CH. What is the most appropriate parameter by which to measure mechanical properties of viscoelastic structure like the cornea? CH? Ocular rigidity? Other? Kuo , Boston 2010