Differential Associations of Myopia with Major Age-Related Eye Diseases
The authors of this population-based, cross-sectional study aimed to determine the associations of myopia and axial length (AL) with major age-related eye diseases, including age-related macular degeneration (AMD), diabetic retinopathy (DR), age-related cataract and primary open-angle glaucoma (POAG).
They included 3,400 Indians in Singapore (75.6% response rate) aged 40 to 84 years and determined refractive error by subjective refraction. The authors also determined AL by noncontact partial coherence laser interferometry and defined AMD and DR from retinal photographs according to the Wisconsin Age-Related Maculopathy Grading System and Airlie House classification system, respectively. They clinically diagnosed age-related cataract using the Lens Opacity Classification System (LOCS) III system and defined glaucoma according to International Society for Geographical and Epidemiological Ophthalmology criteria. Main outcome measures were AMD, DR, age-related cataract and POAG.
Myopic eyes (spherical equivalent [SE] <–0.5D were less likely to have AMD (early plus late AMD) (odds ratio [OR], 0.45; 95% confidence interval [CI], 0.25–0.79) or DR (OR, 0.68; 95% CI, 0.46–0.98) compared with emmetropic eyes; each millimeter increase in AL was associated with a lower prevalence of AMD (OR, 0.76; 95% CI, 0.65–0.89) and DR (OR, 0.73; 95% CI, 0.63–0.86), the authors reported. They found that myopic eyes were more likely to have nuclear (OR, 1.57; 95% CI, 1.13–2.20) and posterior subcapsular (OR, 1.73; 95% CI, 1.10–2.72) cataract, but not cortical cataract (p=0.64) and that each millimeter increase in AL was associated with a higher prevalence of posterior subcapsular cataract (PSC) (OR, 1.29; 95% CI, 1.07–1.55), but not nuclear (p=0.77) or cortical (p=0.39) cataract. They also noted that eyes with high myopia (SE <–6.0D) were more likely to have POAG (OR, 5.90; 95% CI, 2.68–12.97); each millimeter increase in AL was associated with a higher prevalence of POAG (OR, 1.43; 95% CI, 1.13–1.80).
In conclusion, myopic eyes are less likely to have AMD and DR, but are more likely to have nuclear cataract, PSC and POAG. The associations of myopia with AMD, DR and POAG are mostly explained by longer AL. However, the association between myopia and nuclear cataract is explained by lens refraction rather than AL.