Systemic hypertension exaggerates retinal photic injury
S. Li, T. T. Lam, J. Fu and M. O. Tso
Georgiana Dvorak Theobald Ophthalmic Pathology Laboratory, Department of Ophthalmology and Visual Sciences, University of Illinois, Chicago, College of Medicine, USA.
OBJECTIVE: To determine whether chronic systemic hypertension alters the
response of photoreceptors to photic stress. METHODS: 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.
RESULTS: 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. CONCLUSION: 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.
