Abstract
The purpose of this study was to better understand the role of ocular pigmentation and genetics in light-induced retinal damage. Adult pigmented [Long Evans (LE) and Brown Norway (BN)] and albino [Sprague Dawley (SD) and Lewis (LW)] rats were exposed to a bright cyclic light for 6 consecutive days and where compared with juvenile animals exposed to the same bright light environment from postnatal age 14 to 28. Flash ERGs and retinal histology were performed at predetermined days (D) post-light exposure. At D1, ERGs were similar in all adult groups with no recordable a-waves and residual b-waves. A transient recovery was noticed at D30 in the LW and LE only [b-wave: 18% and 25% of their original amplitude respectively]. Histology revealed that BN retina was the most damaged, while LE retina was best preserved. SD and LW rats were almost as damaged as BN rats. In contrast, the retina of juvenile BN was almost as resistant to the bright light exposure as that of juvenile LE rats. Our results strongly suggest that, although ocular pigmentation and genetic background are important factors in regulating the severity of light-induced retinal damage, the age of the animal at the onset of light exposure appears to be the most important determining factor.
Highlights
In animal models of light damage, when strain differences are taken into consideration, the retina of pigmented animals is usually reported to be more resistant to damage compared to that of albino strains [1,2,3], suggesting that ocular pigmentation does protect the retina from light-induced damages
This study showed that the retina of adult pigmented Brown Norway (BN) rats was more susceptible to bright light exposure compared to the retina of albino WS rats, it was shown to be less responsive to the antioxidant therapy [5]
ERGs of recognisable morphologies could only be recorded from LW and Long Evans (LE) rats (D15, D31 and long term recordings) while only severely depressed ERGs could be recorded from BN and SD rats irrespective of time post exposure
Summary
In animal models of light damage, when strain differences are taken into consideration, the retina of pigmented animals is usually reported to be more resistant to damage compared to that of albino strains [1,2,3], suggesting that ocular pigmentation does protect the retina from light-induced damages. This was not the objective, this claim was recently put to test in a study which compared the protective effect of blueberry extract (potent antioxidant) on the retina of pigmented Brown-Norway (BN) and albino Wistar (WS) rats exposed to bright light [5]. This study showed that the retina of adult pigmented BN rats was more susceptible to bright light exposure compared to the retina of albino WS rats, it was shown to be less responsive to the antioxidant therapy [5]
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