Retinal Arterial Constriction With Aging May Modulate Vascular Perfusion of the Eye

Abstract

Purpose: : Gross alterations in the physical integrity of retinal vessels are visible clinically and pathognomonic of ocular and systemic disease. However, fine changes in vessel caliber escape detection in routine clinical examinations. Furthermore, the physiological implications of sub-clinical changes in vessel caliber are largely unknown. In the present study we evaluated the relationship between the caliber of retinal vessels over the majority of their length and cardiovascular function as indexed by the brachial blood pressure.

Methods: : Digital color fundus photographs of the right eye were taken by the same examiner in each subject of a cohort of 91 healthy adult volunteers (age range: 20-80 yrs). A Vessel Map program (Imedos.de) was used to measure the diameters of paired arteries and veins in the superior and inferior quadrants. Measurements were made from the ONH distally to include a standard 2700microm length of vessel. Individual vessel thickness profiles were plotted as a function of subject age and retinal locus. Each subject's systolic and diastolic pressures, and heart rate were measured twice as was the IOP. These parameters were used to calculate the Ocular Perfusion Pressure (OPP=BPmean-IOP). Subsequently, each parameter was plotted as a function of age. Linear regression analyses were used to identify parameter trends (p=0.05).

Results: : The systolic (p=0.001) and diastolic (p=0.053) pressures increased with age but the IOP (p=0.319) and heart rate (p=0.913) were unchanged over the 60-year test range. As a result, the calculated OPP increased with age (p=0.006). While the diameter for all arteries combined decreased with age (p=0.005) veins did not change caliber (p=0.151).

Conclusions: : The progressive decrease in retinal arterial caliber with age may counter the concurrent increase in the OPP. We interpret this interaction between the OPP and arterial caliber as a form of ocular blood flow regulation in healthy subjects.

Keywords: blood supply • aging • retina