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Electrophysiology of the X-Ray Phosphene

1955; Radiation Research Society; Volume: 2; Issue: 4 Linguagem: Inglês

10.2307/3570239

1938-5404

Leo E. Lipetz,

Retinal Development and Disorders

This is the second of two papers dealing with the ability of ionizing radiations to arouse a sensation of light (a phosphene) on striking the eye. In the first paper (Lipetz, 1), the literature on the X-ray and radium phosphenes was critically reviewed. It was concluded that the most probable mechanism of the X-ray was a direct action of the rays on the photochemicals of the rods and cones of the retina. The radium was thought to be the sum of two phosphenes -one resulting from a fluorescence of the eye media produced by the radium's f-particles, and the other, a much dimmer one, resulting from the direct action of the radium's -y-rays on the retinal photochemicals. In this paper is described an attempt to test the validity of the proposed mechanism of the X-ray phosphene. The phosphene was detected objectively by measuring the electrical response at an optic nerve ganglion cell of a frog retina. Light and X-rays were found to have the same effect except for a few differences attributed to an injurious action of the X-rays. The threshold incident energies of light and of X-rays for a response were determined. These electrical responses to light are known to depend on the energization by light of visual purple, the photochemical of the rods. Moreover, light is known to bleach visual purple. According to the proposed mechanism of the X-ray phosphene, both statements should hold true for X-rays also. It was demonstrated that X-rays and other ionizing radiations bleached visual purple. The ratio of bleaching dose to threshold response dose of X-rays was determined and was compared to the ratio for light. The energies released in the retinal visual purple by light and by X-rays for a threshold response were calculated and compared. From these comparisons conclusions were drawn as to the validity of the proposed mechanism of the Xray phosphene.