Axial length and its associations in a Russian population: The Ural Eye and Medical Study

Purpose To assess the normal distribution of axial length and its associations in a population of Russia. Methods The population-based Ural Eye and Medical Study included 5,899 (80.5%) individuals out of 7328 eligible individuals aged 40+ years. The participants underwent an ocular and systemic examination. Axial length was measured sonographically (Ultra-compact A/B/P ultrasound system, Quantel Medical, Cournon d'Auvergne, France). Results Biometric data were available for 5707 (96.7%) individuals with a mean age of 58.8 +/- 10.6 years (range: 40-94 years; 25%, 50%, 75% quartile: 51.0, 58.0, 66.0 years, respectively). Mean axial length was 23.30 +/- 1.10 mm (range: 19.02-32.87mm; 95% confidence interval (CI): 21.36-25.89; 25%, 50%, 75% quartile: 22.65mm, 23.23mm, 23.88mm, resp.). Prevalences of moderate myopia (axial length: 24.5-<26.5mm) and high myopia (axial length >26.5mm) were 555/5707 (8.7%; 95% CI: 9.0,10.5) and 78/5707 (1.4%; 95% CI: 1.1,1.7), respectively. Longer axial length (mean: 23.30 +/- 1.10mm) was associated (correlation coefficient r(2) :0.70) with older age (P<0.001; standardized regression coefficient beta:0.14), taller body height (P<0.001; beta: 0.07), higher level of education (P<0.001; beta:0.04), higher intraocular pressure (P<0.001; beta: 0.03), more myopic spherical refractive error (P<0.001; beta:-0.55), lower corneal refractive power (P<0.001; beta:-0.44), deeper anterior chamber depth (P<0.001; beta:0.20), wider anterior chamber angle (P<0.001; beta:0.05), thinner peripapillary retinal nerve fiber layer thickness (P<0.001; beta:-0.04), higher degree of macular fundus tessellation (P<0.001; beta:0.08), lower prevalence of epiretinal membranes (P = 0.01; beta-0.02) and pseudoexfoliation (P = 0.007; beta:-0.02) and higher prevalence of myopic maculopathy (P<0.001; beta:0.08). In that model, prevalence of age-related macular degeneration (any type: P = 0.84; early type: P = 0.46), diabetic retinopathy (P = 0.16), and region of habitation (P = 0.27) were not significantly associated with axial length. Conclusions Mean axial length in this typically multi-ethnic Russian study population was comparable with values from populations in Singapore and Beijing. In contrast to previous studies, axial length was not significantly related with the prevalences of age-related macular degeneration and diabetic retinopathy or region of habitation.