Purpose To evaluate the influence of refractive error and axial length (AL) on retinal vascular network geometry measurements in an adult Asian population. Methods This was a population‐based, cross‐sectional study on 2882 persons with diabetes in the Singapore Malay Eye Study (SiMES). Spherical equivalent refraction (SE) was assessed using an autokeratorefractometer and subjective refraction. AL was measured by IOL Master. Retinal vascular caliber, tortuosity, and branching characteristics were quantified from retinal fundus photographs using a semi‐automated computer‐assisted program according to a standardized protocol. Results In multivariate analyses adjusting for age, gender, education, smoking, blood pressure, diabetes status, and anti‐hypertensive medication use, longer AL and more myopic refraction were associated with narrower retinal arterioles and venules,(p ≤ 0.001 for all) and less tortuous (straighter) arterioles,(p < 0.001 for both). Longer AL and more myopic refraction were also associated with increased branching coefficients in both arterioles (p < 0.001 for both) and venules.(p = 0.02 and p < 0.001 respectively). Longer AL and more myopic refraction were associated with more acute branching angles in arterioles (p < 0.001 for both) but not venules. Conclusion Myopic refractive errors and longer AL are associated with narrower retinal arterioles and venules, less tortuous arterioles, and increased branching coefficients in both arterioles and venules. These findings provide insights into ocular blood flow in myopia, and also suggest that future studies evaluating these retinal parameters should account for the influence of AL and refractive error.

Purpose: To evaluate the relationships between refractive error, axial length (AL), and retinal vascular oxygen saturation in an adult population. Methods: This was a hospital-based, prospective observational study. The left eyes of phakic adult subjects without media opacity were analyzed. Subjective undilated manifest refraction was performed, and refractive errors were defined as myopia (spherical equivalent [SE], ,À1 D), emmetropia (SE between À1 D and þ1 D) and hyperopia (SE .þ1 D). Retinal oximetry was performed using the Oxymap system (Oxymap Inc., Reykjavik, Iceland). Multivariate linear regression models were constructed to assess the relationship between retinal vascular oxygen saturation, SE, and AL obtained with optical biometry, with adjustments for age, sex, race, blood pressure, hyperlipidemia, and diabetes mellitus. Results: There were 85 subjects, with mean age of 66.1 6 11.3 years. The majority were female (60%) and Chinese (84%). A total of 60% were myopic, 28% emmetropic, and 12% hyperopic. Mean SE was À5.29 6 6.51 D and mean AL was 25.30 6 2.99 mm. In multivariate analyses, more myopic SE and longer AL were associated with lower retinal arteriolar oxygen saturation (regression coefficient B ¼ 0.61 [95% confidence interval, 0.28, 0.95], P ¼ 0.001; and B ¼ À1.13 [95% confidence interval, À1.71, À0.56], P , 0.001, respectively). Subjects with myopic SE and AL also had lower retinal arteriolar oxygen saturation than emmetropes and hyperopes (P ¼ 0.03 and P ¼ 0.02, respectively). Conclusions: Eyes with more myopic SE and longer AL have lower retinal arteriolar oxygen saturation. Translational Relevance: This study provides direct evidence of a link between retinal oxygenation and hypoxia and myopia by using a novel device that quantifies retinal vascular oxygenation in vivo.

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