Natural history. Zoology. Luminous Spectra on the Retina.

The Year-Book of Facts in Science and Art
Exhibiting the Most Important discoveries and Improvements of the past year,
in mechanics and the useful arts; natural philosophy; electricity; chemistry; zoology and biology; geology and geography; meteorology and astronomy.
By John Timbs,
editor of "the Arcana of Science and Art."
London:
David Bogue, Fleet Street,
MDCCCXLIX (1849)A paper has been read to the British Association, "On the Luminous Spectra exerted by Pressure on the Retina, and their Application to the Diagnosis of the Affections of the Retina and its Appendages," by Dr. A. Waller. These observations relate to the luminous spectra which appear in the field of vision when the eyeball is compressed, or when the head has received a sharp blow, and in various other circumstances. After having described the discoveries of Sir Isaac Newton and others, the author goes on to relate his own observations, and finds that these spectra vary according to the part of the eyeball which is compressed. If compressed at the upper part they appear to be most bright, and consist of several concentric rings alternately bright and dark. He shows that these spectra may be employed with great advantage as a means of discriminating the diseases of the retina and optic nerve from those which affect the crystalline lens, the iris, and the other parts in front of the retina. In amaurosis, glaucoma, and other affections of the nervous parts, the spectra are found to become more faint in proportion as the nervous powers are injured, and are entirely absent when the visual powers are more deeply impaired. On the other hand, in those numerous affections of the eye where the rays of light can no longer form their images on the retina on account of the opacity of the parts which they have to traverse, the ocular spectra are found to be unimpaired in their brightness. The author cited numerous cases in confirmation of this statement.

— Athenæum, No. 1087.