Treatment with 670-nm light protects the cone photoreceptors from white light-induced degeneration

The light-induced photoreceptor damage model has been used to characterise pathological mechanisms of retinal degenerative diseases and to test potential therapeutic strategies for these conditions. This model is characterised by two fundamental processes that are common to many retinal degenerative conditions; photoreceptor cell death and loss of retinal function. In the present study, we explored the effects of 670-nm light, on cone structure and function using the light damage model in rat retina. Irradiation with 670-nm light has been shown to be beneficial in treating various disease conditions, both in humans and animal models. Sprague-Dawley rats were exposed to bright white light (BL) for 24 h. Animals were divided into three groups (n = 8/group). Each group received 670-nm light treatment at 9 J/cm ² using an LED array 1× daily for 5 days prior to light exposure (pre-conditioned), immediately after cessation of BL for 5 days (post-conditioned) or 1 day prior to BL, then 2× daily during and immediately after BL (mid-conditioned). Assessment of retinal function (ERG), structure (histology), changes in protein expression (immunohistochemistry) and gene expression (RT-qPCR) were evaluated 7 days after light exposure. Damaging effects of white light on the photoreceptor population, function and structure were ameliorated by 670-nm light in the treated groups compared to the non-treated animals (p < 0.05). Present results suggest that treatment with 670-nm light may provide long-term stability of the retina against white light-induced degeneration.