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K. Valter-Kocsi, R. S. Albarracin; Photobiomodulation With 670nm Light Ameliorates the Effects of Light on the Morphology and Function of the Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):680.
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To test the efficacy of photobiomodulation in the model of light-induced photoreceptor degeneration.
Young adult albino SD rats were exposed to 24 h bright (1000 lux) continuous white light (BCL). Animals were divided into 3 groups. The first group was treated with 670nm red light (NIR) at 10J/cm2 using an LED array (Quantum Devices) 1xdaily for 5 days prior to light exposure (pre-treatment). The second group was treated immediately after the cessation of BCL for 5 days (post-treatment). The third group was treated 1 day prior to BCL, then 2x daily during and immediately after BCL (mid-treatment). Approriate controls were used. Retinal function was assessed 1wk after light exposure with scotopic full field flash ERGs. Animals were euthanised immediately after the last treatment or 1 week after BCL. To follow apoptotic cell death, the TUNEL technique was used, and ONL thickness was measured to assess the accumulative effects of light damage and NIR treatment. Immunohistochemistry was performed to assess the inflammatory status of retinas.
Photoreceptor function was significantly reduced in control retinas following light exposure, a-wave amplitude was reduced by 70-90% from baseline values. The decline of retinal function was significantly reduced in the NIR-treated animals where a-wave amplitude in the pre-treatment group dropped by only 30-50%. In all treatment groups, cell death was significantly lower than control: 5.13profile/mm in the pre-treatment group vs 208.5/mm in LD control at 0 day recovery. ONL showed significant thinning in the superior retina of the non-treated retinas when compared to the appropriate treated group. Inflammatory protein expressions were also decreased when compared to light-exposed non-NIR treated controls in all treated groups.
Photobiomodulation with 670nm light protects retinal function and structure following exposure to damaging light. Though the exact mechanism of action is not known, present results suggest that NIR treatment may regulate the tissue’s inflammatory response thereby providing protection against light-induced photoreceptor degeneration.
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