Chronic open-angle glaucoma and associated ophthalmic findings in monozygotic twins and their spouses in Iceland.

Purpose: To determine the concordance of glaucoma and ocular parameters in monozygotic twins and their spouses.

Methods: This was a prospective study that included 50 twin pairs 55 years of age or older and 47 of their spouses. Zygosity was determined by genetic laboratory testing.

Results: The concordance of open-angle glaucoma in monozygotic twin pairs was 98.0%, which significantly exceeded that of twin/spouse pairs (70.2%). There was a significant association in mean intraocular pressure (IOP), mean axial length, anterior chamber depth, and refractive error in the twin pairs. However, there was no association between the twins and their spouses for these ocular parameters. Eight twin pairs were found to have pseudoexfoliation syndrome (PXFS), five of which were concordant. There was no association between glaucoma and mean axial length or glaucoma and refractive error in the twin pairs studied.

Conclusion: The statistically significant higher concordance of glaucoma--and the high correlation of mean IOP, mean axial length, anterior chamber depth, and refractive error--in twin pairs and the lack of association of these factors in twin/spouse pairs strongly suggests the importance of genetic factors for these ocular parameters.