Papillary Trunk Bifurcation Angles as Major Determinants of Ocular Perfusion: A Cross-Sectional Study

Abstract

Background: Notable work has been done by Cecile and Murray in as early as 1926, on the structural and topological aspects of vasculature based on the concept that blood vessel size and arrangement is such that it provides blood flow with minimum energy loss. In the theoretical analysis of arterial networks, the existence of geometric optimisation for enabling functional adequacy has long been suggested, but observational studies have not yet fully corroborated these theories. Data on branching or bifurcation angles of retinal microvasculature is not only insufficient but also inconclusive. Aim: Attending to this gap in information, we compared the central retinal artery (CRA) branching angles of known diabetics with healthy subjects and explored their possible role in determining the circulatory adequacy of human retina. Methods: This study was done on North Indian subjects attending retina clinics of prominent tertiary centers of north India during 2019 through 2020. Fundus images were acquired through convenience sampling from 860 consecutive eyes of 430 subjects. Fluorescein fundus angiography was followed up for diabetics. CRA branching angles from digitalized fundus photographs of known diabetics and healthy subjects was analyzed through semi-automated digital image management tool and the readings were clinically correlated to note the occurrence and severity of retinopathic perfusion defects was Results: We found marked differences between CRA branching angles among diabetics and healthy subjects and a significant correlation between branching anless and the occurrence and severity of retinopathic perfusion defects. Discussion and Conclusion: The orientation of retinal blood vessels on the fundus plane is not merely ‘a matter of chance’ in the anatomic chronicle of the human body; rather, it has biological heralds and functional consequences. Direction, branching, angles; all determine the efficacy and abundance of blood flow in the human retina that hold indispensible relevance for optimal vision and might be subtle indicators of micro vascular damage in disease states. This study has elucidated retinal vascular geometrics of healthy and diseased Indians, a knowledge that can improve our understanding of ‘abnormal features’ and ‘natural variants’ in retinal vascular architecture. In this study, we quantified the ‘structural factors’ behind perfusion defects of the Diabetic retina.