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J. N. Ver Hoeve, C. B. Y. Kim, T. M. Nork, J. T. Eells, M. Wong-Riley, H. D. Hacker, J. Brown, H. T. Whelan; Neuroprotective Effect of 670 nm Light Following Retinal Laser. Invest. Ophthalmol. Vis. Sci. 2007;48(13):576.
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To evaluate the effect of near-infrared light on the retino-cortical response following focal laser ablation of photoreceptors and pigment epithelium.
Two groups were tested: In one group, 6 cynomolgus monkeys received 128 laser lesions (532 nm Diode: 75 microns, 100 mW, 100 ms) in a grid pattern covering the macula but sparing the fovea. In the second group, 12 rhesus monkeys received a single nd:YAG lesion (1064 nm, 1.3 mW) inferior to the fovea. The lasered eye of half of each group received treatment consisting of 4 joules cm-2 of 670 nm light from a high output LED array. The grid lesion group was treated once per day for 1 week; the YAG lesion group was treated twice per day for 1 week. Visual function was assessed with multifocal electroretinography (mfERG) and concurrently recorded multifocal visual evoked cortical potential (mfVEP). The stimulus was an array of equal-sized hexagonal patches presented at the standard 13.3 ms base rate. Animals were anesthetized with Nembutal during recordings.
Serial mfERG recordings initially showed an increase in amplitude immediately following grid lesions which then diminished in amplitude by 7 d following lesions. There were no differences in the mfERGs of the treatment groups. The single YAG lesion did not appreciably alter the mfERG. However, the cortical response to foveal stimulation, as assessed by the mfVEP, was relatively preserved in the 670 nm-treated animals compared with the sham-treated controls. Similarly, the foveal mfVEP was relatively preserved in the YAG-lesioned animals that were treated with 670 nm light when assessed 70 d after the lesion.
In addition to ablating tissue, retinal laser may result in secondary effects on tissue surrounding the lesion. If the injured tissue involves the fovea, a depressed cortical response is observed. Treatment of retinal tissue with near infrared light resulted in relative preservation of the retino-cortical pathway. The results are consistent with a neuroprotective role of photostimulation at the absorption spectrum of cellular cytochrome oxidase-c (J Biol Chem. 2005 11;280:4761-71).
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