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Arch Ophthalmol. 1999;117:1191.

	Since this article does not have an abstract, we have provided the first 115 words of the full text and any section headings.

WIDMARK has made a series of experiments with a grating spectroscope in order to determine the sensibility of the retina for ultraviolet rays. He finds the following. The normal human eye perceives only a small portion of the ultraviolet rays. The limit of the visible spectrum varies with different individuals, but usually lies within L-M. The rays are perceived directly, and not through fluorescence. Older persons recognize fewer of the ultraviolet rays than younger. This is especially noticeable in persons over sixty-five. The lens is the chief factor in preventing the visibility of the extreme rays, and after its removal the violet end of the visible spectrum is considerably elongated.

Reference: Arch Ophthalmol. 1898;27:417.