Relationship between retinal structures and retinal vessel caliber in normal adolescents.

PURPOSE To describe the normal physiological relationship between retinal arteriolar and venular caliber and retinal nerve fiber layer (RNFL), macular, and optic nerve head parameters. METHODS The Sydney Childhood Eye Study assessed 2038 adolescents aged 12 years. Retinal vessel calibers were measured from digital fundus photographs using standardized protocols. Optical coherence tomography measurements of RNFL, macular, and optic nerve head parameters were obtained with the Fast-scan protocol of the Stratus OCT (Carl Zeiss Meditec, Inc., Dublin, CA). Mixed model analyses were performed. RESULTS After adjustment for covariates, each micrometer increase in RNFL thickness was associated with a 0.22-microm (0.15%, P < 0.0001) and 0.49-microm (0.23%, P < 0.0001) increase in mean arteriolar and venular caliber, respectively. This positive association existed across all RNFL quadrants (0.07%-0.24%, P <or= 0.002). Each micrometer increase in macular thickness (inner/outer) and cubic millimeter increase in macular volume was associated with a 0.12/0.15-microm (0.08%-0.10%, P < 0.0001) and 5.31-microm (3.53%, P < 0.0001) increase in mean arteriolar caliber and a 0.22/0.31-microm (0.10%-0.15%, P < 0.0001) and 10.95-microm (5.08%, P < 0.0001) increase in mean venular caliber, respectively. Finally, each millimeter increase in vertical optic disc diameter and each square millimeter increase in optic disc area was associated with a 2.83-microm (1.88%, P = 0.02) and 2.02-microm (1.35%, P = 0.01) increase in mean retinal arteriolar caliber and a 5.73-microm (2.66%, P = 0.001) and 5.02-microm (2.33%, P < 0.0001) increase in mean retinal venular diameter, respectively. CONCLUSIONS In normal adolescent retinas, thicker RNFL and macula parameters and larger optic discs correlate with larger retinal vascular caliber. Understanding these normal anatomic relationships is essential for determining their significance in studying the vascular etiology of ocular and systemic diseases.