Functional Alteration of Visual Receptor Units and Retinal Pigments by X-Irradiation

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Abstract
Single functional visual receptor units from the compound eyes of 40 Limulus polyphemus were examined for visible light and X-ray "phosphene" responses similar to those previously reported in electroretinogram studies of the whole vertebrate retina. Doses of X-rays many times those required to produce the ERG "phosphenes" or retinal surface potentials were ineffective in reducing the level of dark adaptation. However, reduced light response latency and reduced light threshold were consistently observed during exposure. Extracts and suspensions of retinal material prepared from the eyes of frogs (Rana catesbiana) were examined spectrophotometrically, during and after irradiation. No wavelength shifts of peak optical density were seen that might indicate the alteration of the extracts of formation of photoproducts during irradiation. Density increases consistently followed X-ray exposures of magnitudes up to 5000,000 times as great as the ERG "X-ray phosphene" threshold. Previous theories of visual phosphene production have not required a photochemical transducer. It is proposed that the "X-ray phosphene" may have a similar retinal origin.

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