Axial myopia may be a risk factor for primary open-angle glaucoma

The authors of this study investigated the association of refractive error and ocular biometry with primary open-angle glaucoma (POAG). They sought to determine whether the relationship between myopia and POAG is mediated by axial length or other factors, such as corneal curvature or lenticular changes with age.

This study was part of the Singapore Malay Eye Study, a population- based cross-sectional survey that examined 3,280 people between ages 40 and 80 years old. Participants underwent a standardized clinical examination, including slitlamp biomicroscopy, Goldmann applanation tonometry, refraction, dilated optic disc assessment and measurement of axial length and central corneal thickness.

After adjusting for possible confounders, participants with moderate or high myopia (less than -4.0 D, right eyes) were more likely to have POAG. This association remained significant after controlling for central corneal thickness. People with longer axial lengths had three times the risk of POAG of those with normal axial lengths, independent of central corneal thickness (P = 0.03). However, myopia was no longer associated with POAG after controlling for axial length, suggesting that axial myopia may be the main biometric constituent underlying POAG risk.

This study is unique since it not only confirms the association of myopia and POAG found in other studies but also demonstrates an association between increasing axial length and POAG. The finding of a significant association between axial length and POAG largely explains the association between myopia and POAG and may support a theory involving the association of connective tissue changes with longer axial dimensions as a potential mechanism for POAG.