Mechanism of the Formation of X-Ray-Induced Phosphenes: I. Electrophysiological Investigations

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Abstract
To explore a possible mechanism of the formation of phosphenes detected by astronauts during space flights, the X-ray stimulation of the photoreceptor cells of the eye was investigated. The albino rat''s retina, maintained in culture by perfusion, was used. The electrophysiological response (ERG) induced by X-rays was identical to the ERG produced by a visible light stimulation. With this procedure only a direct interaction between incident radiation and retina induced such an ERG. Irrespective of using the isolated retina or the whole animal, ERG amplitude was proportional to the logarithm of the exposure on the retina. A comparison implied that, to obtain the same ERG amplitude, the incident energy on the retina must be about 5 .times. 106 times larger for X-rays (.hivin.E [mean energy] = 40 keV) than for visible light (.lambda. = 489 nm). The X-rays apparently act on the rod''s photosensitive molecule, rhodopsin.