A manual and atlas of medical ophthalmoscopy / by W.R. Gowers.

Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: A manual and atlas of medical ophthalmoscopy / by W.R. Gowers. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    thin glass, is especially useful for this purpose. A plane mii'ror may be employed instead. If this is not available, the light of the illuminating lamp should be tui-ned low. It is as essential to be aware of the normal variations in colom' for the estimation of a pathological pallor of the optic- disc, as it is for the recognition of congestion. The varia- tions on the negative side are not, perhaps, so considerable as are those on the positive side, but they are sufficient to render familiarity with the appearance of the normal disc essential to prevent mistakes in estimating the slighter degrees of atrophy. As a rule, the disc becomes paler as life advances, and a slight grey tint becomes mingled with the red, but the latter is still perceptible. The physiological cup, if slight, is often indistinct late in life. Thus, a tint which is normal in the old, would be suggestive of atrophy in the young. Again, when the general fundus is unusually dark, the disc will seem to be abnormally pale, simply as an effect of con- trast. In ansemia, also, the disc may become paler, but the change of tint from this cause is not considerable, and is insignij&cant in comparison with the normal variations in colour of the disc. It never constitutes an element of diflB.culty in the recognition of atrophy. When a pathological pallor of the disc is pronoujiced, it extends over the whole area of the disc, but commencing pallor may be most marked in that part of the disc which is normally palest, i.e., the temporal side, where the nerve fibres- are least numerous. The change in this part, however, is only of significance in individuals in whom the physiological cup is small, and the temporal half of the disc normally possesses a distinctly vascular tint. In a great number of cases, in which the physiological excavation is large, and slopes gradually to the sclerotic ring on the temporal side, this portion of the disc may be normally almost as pale as in atrophy. The part on which attention should be chiefly fixed is, therefore, that which normally possesses considerable vasculaiity, the nasal portion. The tint may be observed to become gradually paler, the red sometimes simply fading, and leaving a white colour in its place ; in other cases a grey