To determine whether chronic systemic hypertension alters the response of photoreceptors to photic stress.
Spontaneously hypertensive rats and strain-matched, normotensive Wistar-Kyoto rats were exposed to green fluorescent light (490 to 580 nm, 180 to 200 foot-candles) for 24 hours. Retinal changes were evaluated by histopathologic examination, morphometry of the outer nuclear layer, and rhodopsin levels.
Before light exposure, spontaneously hypertensive rats developed elevated systolic blood pressure and showed mild sclerosis of choroidal vasculature. After exposure, retinas of the spontaneously hypertensive rats revealed exaggerated light damage with increased loss of photoreceptor cells, more distortion, and shortening of the inner and outer segments relative to the normotensive Wistar-Kyoto rats. The outer nuclear layer thickness and rhodopsin level were significantly lower in spontaneously hypertensive rats than in the normotensive Wistar-Kyoto rats by day 14 after light exposure.
Photic injury to photoreceptor cells was exaggerated in spontaneously hypertensive rats. This may have clinical relevance given the association of both systemic hypertension and light exposure in patients with age-related macular degeneration.