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B.B. Thomas, R.B. Aramant, S.R. Sadda, M.J. Seiler; Preservation of Optokinetic Response Following Retinal Transplantation in a Rat Model of Retinal Degeneration . Invest. Ophthalmol. Vis. Sci. 2003;44(13):505.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate visual acuity after retinal transplantation in a rat model of retinal degeneration. Using an optokinetic head-tracking apparatus, the time course of retinal degeneration and, following transplantation, the preservation of visual responses were studied. Methods: Pigmented s334ter-3 (rhodopsin mutant) rats, with rapid photoreceptor degeneration, were used as recipients. 16-27 day old pups were transplanted with fetal retinal sheets in one eye. The non-transplanted eye was used as a control. Rats were tested for head tracking responses in a rotating-drum apparatus according to Coffey et. al., modified to allow separate testing of each eye. Animals were tested weekly from 130-240 days of age, at a light intensity of 450 cd/m2, and a spatial frequency of 0.25 cycles/degree. The head tracking (HT) score per testing period (2 min/eye) was measured as the amount of time (seconds) the rat spent turning the head in the direction of drum rotation. Results: The s334ter-3 rats showed good visual tracking responses up to 137 days of age (HT score = 64.5±5.4 sec). After 145 days of age, a progressive loss of visual responses was observed and after 180 days, the visual sensitivity decreased steeply in both eyes. At 240 days of age, only very weak visual responses could be observed in non-transplanted rats (HT score = 8.8±2.9 sec). In these rats, there was no apparent difference in the temporal progression of visual loss between the right and left eye. In 30% of rats with retinal transplants, good preservation of visual responses was observed in the transplanted eyes whereas visual loss in the control eyes progressed as in a non-transplanted control rat. The HT score for transplanted eyes remained higher (23.25±8.9 sec) compared to the control eyes (8.25±4.6 sec) until the end of testing period (240 days). Conclusions: In non-transplanted s334ter-3 rats, good visual tracking responses can be observed even after the majority of the photoreceptors are degenerated. The progression of visual loss is fairly symmetric in both eyes, and weak head tracking responses can be observed even after 200 days of age. In contrast, in rats with retinal transplants, the magnitude and duration of visual responses can be preserved. This indicates that transplants have a beneficial effect on visual function. Supported by: Foundation Fighting Blindness, Anonymous Sponsor, Foundation for Retinal Research, Fletcher Jones Foundation, NIH EY03040.
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