LONG-TERM INFLUENCE OF INSULIN-DEPENDENT DIABETES-MELLITUS ON REFRACTION AND ITS COMPONENTS - A POPULATION-BASED TWIN STUDY

Aim - To study whether refraction of the eye, or some of its component s is influenced by duration of insulin dependent diabetes mellitus. Me thods - From the young cohort of the population based Danish Twin Regi ster, containing 20888 twin pairs born between 1953 and 1982, all twin pairs having one or both partners affected with IDDM were searched. A utorefraction, autokeratometry, and ultrasonic biometric measurements were carried out on 45 twin pairs: 16 monozygotic (MZ) twin pairs, 14 di-zygotic twin pairs of same sex (DZss), and 15 dizygotic twin pairs of opposite sex (DZos). To obtain an estimate of the influence of dura tion of diabetes, the intrapair differences in duration of diabetes we re correlated with intrapair differences in retraction and each of its components. Results - Refraction was statistically significantly nega tively correlated with duration of diabetes in the DZss group, and axi al length correspondingly positively correlated. Surprisingly, refract ion and axial length in the MZ group, adjusted for confounding factors , were correlated with diabetes duration in the opposite direction tha n in the DZss group, although not reaching statistical significance. L ens thickness was statistically significantly positively correlated wi th duration of diabetes in both MZ and DZ twins. Anterior chamber dept h was negatively correlated with duration of diabetes in all the zygos ity groups. Conclusions - Studies of relations between refraction and duration of diabetes show diverging results. In the MZ group, a tenden cy to reduced axial length and corresponding hyperopia with increasing duration of diabetes was found. However, in the DZ group of same sex the opposite tendency was found. Increasing lens thickness and decreas ing anterior chamber depth with increasing duration of diabetes have b een confirmed in this study.