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Nature volume 50, pages 307308 | Download Citation



THE RESULTS OF IMPRUDENT SOLAR OBSERVATIONS.— Dr. George Mackay, of the Royal Infirmary, Edinburgh, has sent us a pamphlet “On Blinding of the Retina by Direct Sunlight”(J. and A. Churchill), being a study in prognosis, based chiefly upon accidents incurred during the observation of partial solar eclipses. Tyros in observations of the sun, and also many incautious astronomers, have sustained more or less permanent injury to the sight by looking at it or its image without the interposition of a dark glass, or similar absorber, of sufficient thickness. During the progress of partial solar eclipses, the laity often make incautious observations, and the results of gratifying such curiosity have furnished Dr. Mackay with the chief part of the clinical material for his study. The paper, which originally appeared in the Ophthalmic Review, opens with a historical survey of the few cases of ocular injury from exposure to sunlight, recorded in historical literature. There is a tradition that Galileo seriously impaired the sight of his right eye by his solar observations, but Dr. Mackay has not been able to trace the story to its origin. It is well known that, in his later years, Galileo became quite blind, but the loss of sight was apparently caused by an affection of the cornea, and not by injury to the retina. The earliest precise description of the subjective sensations consequent upon focussing solar rays upon the retina is due to Reid, a Professor of Moral Philosophy in the University of Glasgow. He observed the transit of Venus in May 1761, without taking any precautions to modify the intensity of sunlight, and the result was that he was afflicted with metamorphosia; that is, objects appeared to him in distorted forms. Very few other cases of similar ocular injury have been described. Fortunately for Dr. Mackay, the partial eclipse of the sun in June 1890, and that of June 1891, both visible at Edinburgh, furnished him with seven new cases of “Eclipse Blinding,” all of which he examined with great care, both with the ophthalmoscope and with type and colour-tests. The patients suffered from an impairment of visual acuteness, and, to most of them, dark spots appeared in their fields of vision. Sometimes these spots were fixed, and in other cases they oscillated rapidly. Dr. Mackay says that complete recovery from the injury, even in cases of only slight failure for test-type, is exceptional if investigated by sufficiently refined methods. It is pointed out that the treatment ought to be preventive: smoked and coloured glasses of the feeble shades ordinarily used by the public to view solar phenomena are quite insufficient. Experience shows that, to view the sun with impunity, even in January, it is necessary to use a glass so dark that no object illuminated by diffuse daylight is visible through it.

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