Albarracin R, Eells J, Valter K
Research School of Biology.
Purpose.
We tested the hypothesis that near-infrared (NIR) light treatment (photobiomodulation) would attenuate bright light damage in the albino rat retina.
Methods.
Young adult Sprague-Dawley (SD) albino rats were raised in dim (5lx) cyclic light then exposed to bright (1000lx) continuous light for 24h. Animals were treated with 670nm light (9J/cm(2)) using an LED array before, during or after light exposure. Retinas were examined for function, structural changes, cell loss, and markers of stress and inflammation at 1week and 1month after exposure to damaging white light.
Results.
Bright light caused photoreceptor-specific cell death in control retinas. Significant up-regulation of stress and neuroprotective factors, and the presence of activated microglia was also noted following light damage. Photobiomodulation profoundly attenuated histopathological alterations in all three treatment groups. NIR treatment also abolished microglial invasion of the retina and significantly reduced the presence of stress and neuroprotectant molecules. Bright light-induced reductions in photoreceptor function were significantly ameliorated by photobiomodulation in animals treated before and during light damage. Photoreceptor function was initially reduced in animals treated following bright light damage but recovered by one-month post exposure.
Conclusions.
NIR photobiomodulation is protective against bright light-induced retinal degeneration even when NIR treatment is applied after light exposure. This protective effect appears to involve a reduction of cell death and inflammation. Photobiomodulation has the potential to become an important treatment modality to prevent or treat light-induced stress in the retina. More generally, it could be beneficial in the prevention and treatment of retinal conditions involving inflammatory mechanisms.
Invest Ophthalmol Vis Sci 2011 Mar 18
