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November 1959


Author Affiliations

30 E. 40th St. New York 16.

AMA Arch Ophthalmol. 1959;62(5):917-918. doi:10.1001/archopht.1959.04220050177029

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To the Editor:  —On page 413, of the second edition (1939) of H. H. Emsley's "Visual Optics," the following explanation appears:"The student will understand why, although a positive cylinder produces a real focal line parallel to its axis, the observed streak is perpendicular thereto, in the following way; hold a disc of Maddox rods—at arm's length a metre or so away from the muscle light. Each rod or groove of the disc will be seen to produce a short focal line parallel to itself. Now slowly approach the disc towards the eye; it will be observed that each focal line blurs out in a direction perpendicular to its length, the blurs ultimately overlapping and forming a long streak perpendicular to the axes of the rods and of a width determined by the diameter of your pupil. On retreating from the light, with the rods close to the eye, the

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