Visual phenomena connected with the yellow spot / by F.W. Edridge-Green.

  • Edridge-Green, F. W. (Frederick William), 1863-1953.
Date:
1910
Catalogue details

Licence: In copyright

Credit: Visual phenomena connected with the yellow spot / by F.W. Edridge-Green. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    [Reprinted from the Journal of Physiology, Vol. XLI. Nos. 3 <b 4, November 9, 191 VISUAL PHENOMENA CONNECTED WIT] YELLOW SPOT. By F. W. EDRIDGE-GREEN, M.D., F.R.C.S., Beit Medical Research Fellow1. (From the Institute of Physiology, University College, London.) I propose considering a certain number of subjective and entoptic phenomena connected with the yellow spot. I. Various appearances in the field of vision due to peculiarities of the yellow spot. 1. Loew&s experiment. If we look at a clear white surface through a solution of chloride of chromium, which is of a celadon green colour, we shall see a purple spot in the centre which varies in size and shape, with different persons. On careful examination it will be found to consist of three portions, the centre corresponding to the fovea appears as a bright purple disk, the middle corresponding to the non-vascular portion of the yellow spot appearing as a dark green ring, and lastly Loewi’s ring corresponding more or less accurately to the outer feeble yellow portions of the yellow spot which appears as a purple ring surrounding the central portion and possessing a diameter twice or three times as large. 2. Apparent size of regions of yellow spot in field of vision. The region corresponding to the yellow spot occupies a considerable area in the field of vision. I find that the visual angle which any portion subtends can be easily measured by projecting the after-image of an object occupying a known visual angle on the sky above a house. A comparison is easily made in both cases with portions of the house. If an observer look straight at the cloudless sky, preferably about three hours before the sun sets, for about ten to twenty seconds, a disk or an ellipse with the long diameter horizontal and which is to me of about nine degrees appears in the sky. Inside this is a central darker portion of about two degrees in each diameter and this surrounds a central 1 A paper read in the Phys. Section of the Brit. Med. Ass. 1910. PH. XU. 18