Aim-To study whether refraction of the eye, or some of its components is influenced by duration of insulin dependent diabetes mellitus. Methods-From the young cohort of the population based Danish Twin Register, containing 20 888 twin pairs born between 1953 and 1982, all twin pairs having one or both partners aVected with IDDM were searched. Autorefraction, autokeratometry, and ultrasonic biometric measurements were carried out on 45 twin pairs: 16 monozygotic (MZ) twin pairs, 14 dizygotic twin pairs of same sex (DZss), and 15 dizygotic twin pairs of opposite sex (DZos). To obtain an estimate of the influence of duration of diabetes, the intrapair diVerences in duration of diabetes were correlated with intrapair diVerences in refraction and each of its components. Results-Refraction was statistically significantly negatively correlated with duration of diabetes in the DZss group, and axial length correspondingly positively correlated. Surprisingly, refraction and axial length in the MZ group, adjusted for confounding factors, were correlated with diabetes duration in the opposite direction than in the DZss group, although not reaching statistical significance. Lens thickness was statistically significantly positively correlated with duration of diabetes in both MZ and DZ twins. Anterior chamber depth was negatively correlated with duration of diabetes in all the zygosity groups. Conclusions-Studies of relations between refraction and duration of diabetes show diverging results. In the MZ group, a tendency 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 decreasing anterior chamber depth with increasing duration of diabetes have been confirmed in this study. (Br J Ophthalmol 1997;81:343-349) Refraction and its components are influenced by both environmental and inherited factors. Twin studies have earlier described the importance of genes in refraction, by high concordance rates of refraction in monozygotic twins compared with dizygotic twins.

(BrJ Ophthalmol 1996; 80: 405-408)

This paper examines the possibility of using the surgical result in the first eye when planning the intraocular lens power for the second eye. Two methods were considered: (1) an empirical method by which one regards the second procedure as a repeat of the one in the first eye and calculates the power from the actual refractive error obtained in the first eye and (2) a theoretical method by which one measures the pseudophakic anterior chamber depth (ACD) of the first eye and uses this value to plan for the second eye. Based on the data from 136 second eye procedures using extracapsular cataract extraction, the prediction error of the empirical method ranged from -10.5 to +9.5 diopters. The error of the theoretical method ranged from -2.3 to +2.8 diopters, which was significantly more accurate than the empirical method (P < .001). We conclude that the fellow eye ACD may be used as a guideline for the assumed ACD of the second eye. However, such use of the fellow eye ACD could not be shown to improve power calculation predictions significantly.

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