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Article
December 1940

MEASUREMENT OF THRESHOLD INTENSITY

Arch Ophthalmol. 1940;24(6):1258. doi:10.1001/archopht.1940.00870060200015

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Abstract

To the Editor.  —1 should like to call attention to an error which appeared in the article by Drs. Isaacs, Jung and Ivy in the October issue of the Archives (24: 698, 1940), entitled "Clinical Studies of Vitamin A Deficiency."In their graphs of data obtained on the Hecht-Shlaer adaptometer the threshold intensities are given logarithmically in terms of micromillilamberts. This is incorrect. Their normal data fall in a range similar to the range observed by Dr. Selig Hecht and myself; the correct unit of light intensity is the micromicrolambert (1 micromicrolambert is equal to 1/1,000 micromillilambert, or one billionth of a millilambert). Their intensities of brightness are in error, therefore, by 3 log units.Incidentally, they gave a wrong reference when quoting from the paper by Dr. Hecht and myself ; their footnote 28 should read : Hecht, S., and Mandelbaum, J. : The Relation Between Vitamin A and Dark Adaptation, J.

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