Abstract
Abstract: :
Purpose: To study the age-dependence of autoregulation of human retinal arterioles in vivo using a non-invasive device, the Retinal Vessel Analyser (RVA, Zeiss, Germany). Methods: Two groups of healthy subjects were studied: Group 1 consisted of nine persons in the age range of 20-29 years and group 2 consisted of eleven persons in the age range of 50-59 years. In each person the diameter of the retinal arterioles was measured continuously over a 9-minute period. After a 3-minute baseline measurement (baseline I), isometric exercise (lifting a weight in straight arm) was performed for 3 minutes, and finally another baseline measurement was performed over a 3 minute period (baseline II). The mean arterial blood pressure (MAP) was measured once during each period. This procedure was repeated five times with increasing weight (½, 1, 1½, 2, and 2½ kg). Results: In group 1, isometric exercise caused a significant rise in mean arterial blood pressure (MAP) and a significant reduction of the diameter of the retinal arterioles. The maximal response occurred at 2½ kg giving a 22.5% rise in MAP (±2.4, p=0.00003) and a 4.6% decrease on arteriolar diameter (±0.9, p=0.001). In group 2, isometric exercise also caused a significant rise in MAP to reach a maximum of 19% (±2.0, p=0.000004) when lifting 2½ kg in straight arm, but without any significant change in the diameter (0.4% increase in diameter, ±1.1, p=0.82). Conclusions: Arterial hypertension elicited by isometric exercise induces a compensatory retinal vasoconstriction in young persons, but not in older persons. This indicates that retinal autoregulation decreases with age.
Keywords: retina • clinical research methodology