How to use the ophthalmoscope : being elementary instructions in ophthalmoscopy, arranged for the use of students / by Edgar A. Browne.

Browne, Edgar A. (Edgar Athelstane), 1841-1917.

Date:: 1883

Credit: How to use the ophthalmoscope : being elementary instructions in ophthalmoscopy, arranged for the use of students / by Edgar A. Browne. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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$depressed, examine their refraction. If depressed, they will ]ie beyond the principal focus of the eye, and will answer the tests for myopia; if elevated, tliey will lie within the principal focus, and V :1 answer the tests for hypermetropia. Sm^ . trunks form better guides than the larger vessels, as they require more accurate focussing, and hug the surface more closely. Three kinds of depression or excavations of the optic disc are to be distinguished. Of these, one is a congenital and innocent peculiarity, the others are pathological. (1.) The physiological pit is an exaggeration of the poms opticus. It is most frequently round or oval, but sometimes irregular in shape, whiter than the rest of the surface, and only involving a portion of the nerve-surface. It has no precise margin, but shelves gradually into the higher level. The vessels as they pass over the surface of the disc are seen to bend as they approach the centre, and in well-marked cases their point of entrance is so much out of focus as to be scarcely visible. Fig. 33 is a rough sketch of the appearances of a disc with a physiological depression in its centre, showing the mode in which the vessels dip down out of focus where the level of the nerve becomes depressed. Beneath is a sectional view showino-$