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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.
Mandelbaum J. MEASUREMENT OF THRESHOLD INTENSITY. Arch Ophthalmol. 1940;24(6):1258. doi:10.1001/archopht.1940.00870060200015