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A. Sher, L.-S. Leung, T. Leng, H. Nomoto, Y. Paulus, R. Gariano, B. W. Jones, A. M. Litke, D. V. Palanker; Retinal Plasticity and Restoration of Function After Photocoagulation. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2482.
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While retinal photocoagulation is an effective treatment for a variety of retinopathies, its side effects include secondary loss of visual field and sensitivity, and retinal scarring. Histological studies show that in laser lesions milder than those in current clinical use photoreceptors from surrounding retina fill-in the damage zone without scarring. In order to evaluate the functional significance of this phenomenon, we characterized changes in retinal visual response during the healing of photocoagulation lesions.
Retinal photocoagulation lesions of Moderate and Barely Visible clinical grades were produced in rabbits with a 532-nm Nd:YAG laser, using beam diameter of 250 and 400 µm. Retinal functional properties were characterized by in-vitro multielectrode array (512 electrodes, 1.7 mm2 area) recording of retinal ganglion cells' (RGC) responses to spatiotemporal white noise stimulus.
One day after photocoagulation, the receptive fields of the RGCs had non-sensitive regions corresponding to the lesions’ size and shape, confirming the photoreceptor layer destruction. At one week the non-sensitive areas significantly decreased. Finally, after 2 months sensitivity was restored for the lesions with a smaller initial size while non-responsive areas over larger lesions were retained. The results were similar for the on-set and the off-set of light sensitive RGCs.
Filling of the damage zone by photoreceptors in smaller lesions results in the restoration of visual sensitivity for ON and OFF retinal pathways. This may allow for significant improvements in the treatment of retinopathy by photocoagulation. The phenomenon also establishes a model for study of the dynamic changes in retinal circuitry associated with loss and restoration of the photoreceptors, thus providing a valuable insight into processes occurring in degenerated and remodeling adult retinas, important for studies of retinal rescue through surgical or genetic means. The full extent and functional consequences of the observed retinal plasticity remain to be further explored.
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