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Joseph I. Pascal, M.D.
New York

Arch Ophthal. 1945;33(6):484.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

To the Editor:

—In the January 1945 issue of the ARCHIVES, page 1, appeared a lucid and simplified discussion on "Elementary Illumination for the Ophthalmologist," by Dr. Legrand H. Hardy and Dr. Gertrude Rand. The subject was thoroughly covered. There is, however, one point with reference to the units employed in illumination which, in my experience, has proved a stumbling-block to ophthalmologists and which can, perhaps, be still more simplified. This pertains to the difference and/or the relation between the foot candle (or the meter candle, or lux) and the lumen.

It is, of course, more scientific to define the foot candle in terms of the lumen, but it is easier to understand both by regarding them as different, in some such way as this : The foot candle may be thought of as a unit of "light pressure," or "light density," or "intensity of concentration of light," as Drs. Hardy . . . [Full Text PDF of this Article]

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