Retinal microvasculature measurements in full-term newborn infants

Objective: Currently, there are no published data on retinal microvasculature size in human infants born at term. The purpose of this study was to determine the normal retinal microvasculature measurements in human infants born at term with normal birth weight and to compare these results with measurements in children and adults. Methods: Retinal arteriole and venule measurements were obtained in a cohort of 20 full-term infants. Digital retinal images were obtained from both eyes after pupillary dilation using a digital retinal camera. Measurements of vessel diameter were then obtained using semi-automated software. Results: Twenty infants (9 female infants and 11 male infants) were analyzed. The retinal arteriole diameter was 66.8–123.0 μm (mean, 85.5 (14.3) μm), and the venule diameter was 102.0–167.8 μm (mean, 130.0 (16.0) μm). There were no differences in the arterial or venule diameters between the male and female infants (83.2 (12.2) vs. 88.3 (16.9); P=0.4372; 124.3 (16.0) vs. 137.0 (18.0); P=0.08). The arteriovenous ratio was found to be 0.66 (95% CI 0.62–0.71). The coefficient of correlation between the retinal arterioles and venules was 0.56. The retinal arteriole and venule diameters increase as a person matures. The arteriovenous ratio also increases with age. Conclusion: In newborn infants, retinal venules are significantly larger than retinal arterioles. The arteriovenous ratio is smaller in neonates compared to adults indicating the retinal arteriole diameter increases at a different pace compared to retinal venule. Sex does not influence the retinal microvasculature size in infants. The presence of spontaneous retinal hemorrhage and the inability to account for refractive errors were the main limitations of this study.