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Selective photoreceptor damage in albino rats using continuous blue light. A protocol useful for retinal degeneration
M J Seiler1, O L Liu, N G Cooper
1Department of Ophthalmology & Visual Sciences, University of Louisville, KY 40202, USA. mjseil@athena.louisville.edu
Purpose:
To develop a retinal degeneration model with selective photoreceptor loss and RPE sparing, to be used as recipient for evaluating retinal transplants.
Methods:
Albino rats were exposed to blue light, continuously, for 1-7 days (24-168 h) in a specially designed cage. Eyes were histologically analyzed at periods between 2 h and 8 months after the light exposure. Electroretinograms (ERGs) were recorded from some rats at 12-216 days after exposure. Using behavioral methods, visual thresholds of some rats were determined before exposure and re-measured between 18 and 52 days following exposure.
Results:
Apoptotic nuclei appeared exclusively in the photoreceptor layer after 1-5 days exposure to blue light. Light microscopy revealed that 2-4 days of light exposure reduced the outer nuclear layer (normally eight to ten rows) to 1 row of cells in the central retina and to two to three rows in the periphery, both in the superior and the inferior retina. Average ERG a- and b-wave amplitudes of light-damaged rats were both reduced by about 98%. Visual performance in the behavioral test was substantially impaired.
Conclusions:
Continuous exposure of albino rats to moderate blue light for 2-5 days selectively eliminates most of the photoreceptors while leaving the RPE initially intact.