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J.N. Ver Hoeve, C.B. Y. Kim, T.M. Nork, E.A. Hennes, J.T. Eells, H.T. Whelan; 670 nm Photostimulation Improves Retinal Electrical Response Following Laser Lesions . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4823.
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To determine whether exposure to 670 nm light improves the electrical response of retina following laser lesions.
Female Long–Evans rats (N=31) were randomly assigned to groups that received a grid pattern of 256 75–micron diameter laser spots, or no lesions. Laser energy was adjusted to create a spot of non–hemorrhagic ablated retinal tissue at the photoreceptor–RPE level (Grade I or II). Laser–lesioned and normal eyes were exposed to 4 joules cm–2 of 670 nm light from a light–emitting diode (LED) array either once or twice per day, or received sham treatment. After seven days of treatment, and 24 h after the last LED exposure, the electroretinogram (ERG) was recorded to a photopic intensity series. The height of the b–wave as a function of intensity for each animal was fitted with a Naka–Rushton function and differences between groups were evaluated using one–way ANOVA.
Laser lesions without LED treatment resulted in a decrease in the sensitivity parameter and an increase in the semi–saturation constant of the Naka–Rushton curve as compared with unlesioned controls. Treatment with 670 nm light twice per day significantly increased the sensitivity parameter and decreased the semi–saturation constant compared with lasered eyes that received no treatment. Photostimulation also altered the shape of the post–b–wave ERG in lesioned eyes.
670 nm photostimulation is effective in preventing retinal damage following methanol intoxication in rats, slowing apoptosis in cell cultures exposed to tetrodotoxin or potassium cyanide, and increasing intracellular ATP production. This study extends these findings by showing that treatment twice per day with 670 nm light improves retinal function following thermal photoablative laser lesions.
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