Retinal Vascular Caliber and Its Ocular and Systemic Correlates in Children Living at High Altitude

Background/Objectives: The retina is a highly metabolically active tissue that depends on precise vascular regulation. Childhood represents a critical period of ocular growth, and retinal vascular characteristics may provide insights into the relationship between microvascular development, ocular biometry, and refractive development. However, retinal vascular parameters in children living at high altitude remain poorly characterized. Our goal was to characterize retinal vascular caliber and evaluate its associations with ocular biometric parameters, refractive status, and peripheral oxygen saturation among children living at high altitude. Methods: This cross-sectional baseline analysis included 1410 children from the Lhasa Childhood Eye Study. Retinal vascular parameters, including central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), and arteriolar-to-venular ratio (AVR), were measured from fundus photographs using computer-assisted IVAN software. Ocular biometric parameters, cycloplegic refraction, and SpO2 were assessed. Multivariable linear regression and sensitivity analyses accounting for school clustering and ocular magnification were performed. Results: The mean age was 7.90 ± 0.49 years, and 47.6% were female. Girls had shorter axial length (AL) and larger CRAE and CRVE than boys. Longer AL was associated with smaller CRAE (B = −5.64, p < 0.001) and CRVE (B = −11.24, p < 0.001), while AVR was positively associated with AL (p = 0.03). Lower SpO2 was independently associated with larger CRAE (B = −0.35, p = 0.042), but not CRVE. After AL-based relative ocular magnification correction, the associations between AL and CRAE or CRVE were no longer significant. Myopic children had smaller CRAE and CRVE and higher AVR than non-myopic children. Conclusions: Retinal vascular caliber was associated with ocular biometric characteristics, SpO2, and refractive status in children living at high altitude. The attenuation of AL-related associations after magnification correction highlights the importance of accounting for ocular magnification in retinal vascular measurements.