Age related macular degeneration in monozygotic twins and their spouses in Iceland.

PURPOSE To examine the importance of genetic factors in age-related macular degeneration by using a twin study to compare the concordance of age-related macular degeneration in monozygotic twin pairs and their spouses. METHODS This was a prospective study that included 50 twin pairs and 47 spouses. Zygosity was determined by genetic laboratory testing. Macular findings were graded based on the grading system used by the Macular Photocoagulation Study Group and the International ARM Epidemiological Study Group. RESULTS The concordance of age-related macular degeneration was 90% in monozygotic twin pairs which significantly exceeded that of twin/spouse pairs (70.2%); p=0.0279. In the nine pairs that were concordant, fundus appearance and visual impairment were similar. Environmental factors and medical history were essentially the same in the twin pairs. CONCLUSION The statistically significant higher concordance of age-related macular degeneration in monozygotic twins compared to their spouses strongly suggests the importance of genetic factors.