Clinical lectures on amblyopia and amaurosis / by A. von Graefe ; translated from the German by Hasket Derby.

  • Graefe, Albrecht von, 1828-1870.
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Clinical lectures on amblyopia and amaurosis / by A. von Graefe ; translated from the German by Hasket Derby. Source: Wellcome Collection.

Provider: This material has been provided by the Woodruff Health Sciences Center Library at Emory University, through the Medical Heritage Library. The original may be consulted at the Woodruff Health Sciences Center Library, Emory University.

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    ments in the transparency of the refractive media. Since the classification has been completed, the worthlessness of most of these symptoms has become mani- fest. Let me briefly refer to some of them. The subjective appearances of light* both plain and colored, as also in the form of subjective pictures, occur to any extent in comparatively few amblyopic cases, and, when present, give more infor- mation as to the accompanying condition of the brain itself (as in encephalitis, delirium tremens) than as to the state of the amblyopia. Vastly more importance is to be attached to these phenomena in diseases of the deep-seated membranes, as they here not only sometimes indicate the duration of the progressive periods, but are even of importance as prodromal symptoms (as, for example, in cases of separation of the retina, where they may occur as white balls, drops, or in crescentic shapes, which I attribute to the tension near the equator). The weight laid on these symptoms formerly in cases of amaurosis is due in great measure to the fact that these cases were confounded with affections of the deeper structures. Again, these appearances may be present in their most intense form in an affec- tion, which (so far as it occurs idiopathically, involving neither the field nor the acuteness of vision) may be of some significance as relating to the cerebral eco- nomy, but never passes into amaurosis ; I mean the so-called hyperesthesia reti- nae. In cases of genuine amblyopia, misty or smoky vision is most intimately connected with a diminution of the central or eccentric acuteness of vision, and often only the direct indication of this on the part of the retina. It is at this <}ay hardly necessary to state that the pronounced mouches volantes we often meet in normal eyes (myoclesopsia) are in no wise indicative of amauro- sis. Their cause is partly optical, alterations of the state of refraction, of the range of accommodation, irregularities in the refractive media all facilitating the production of entoptical shadows of diffraction, partly depends on hyperesthesia of the retina, where shadows ordinarily invisible are brought out by the atten- tion concentrated on them. The favorable influence of convex glasses in amblyopia, as facilitating the re- cognition and survey of letters, has been used to aid the prognosis. This expe- riment, leaving out of account any mere correction of refraction, may be used in some cases to demonstrate the continuance of the acuteness of vision, and the full activity of the retina at its centre, gives us, however, in the end, no results that we could not have obtained from the examination of the central and eccentrio vision. The old division of amaurosis into active and passive has practically passed away; although it is not to be denied that in different forms, the relations of the acuteness and field of vision being apparently the same, the capacity of percep- tion is very differently affected by the amount of illumination, and that in this sense we may be said to be dealing with active and passive forms. It is well known that, in the case of a normal eye, the amount of illumination may vary within tolerably wide bounds ; for example, from bright daylight to much less, without exerting a perceptible influence on the acuteness of central or eccentric vision. It first becomes felt (in accordance with a yet undiscovered law) when the amount of illumination is reduced within certain bounds—for example, ap- proaches twilight. In the case of amblyopic eyes we find considerable fluctua- tions often produced by slight changes in the amount of natural, and generally by greater variations in the amount of artificial light. Where a decided dimimu