The anomalies of the ocular muscles / by George T. Stevens.

  • Stevens, George T. (George Thomas), 1832-1921.
Date:
[1889?]
Catalogue details

Licence: Public Domain Mark

Credit: The anomalies of the ocular muscles / by George T. Stevens. Source: Wellcome Collection.

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    the question whether it is important to discover and to es- timate the degree of all these deviations—a subject which will engage our attention further on—we may here assume that alfare important, and that no just appreciation of the conditions which induce asthenopic or kindred troubles can be acquired which does not take them all into account. It becomes necessary, then, to establish some method of in- vestigating and of recording such anomalies. So long as the increased tension upon the interni, in the act of reading, or in other continued work at a like distance, was regarded as the main, if not the only important factor in the causation of muscular fatigue, aside from accommo- dative lesions, the test of the dot and line, as suggested by Graefe for this condition, appeared to answer the require- ments. This familiar test was made at reading distance, although Graefe counsels that, after having determined the degree of insufificiency for this distance, we should examine in the same way for greater distances. Without specifying the distances, he, in close relation to this part of the dis- cussion, mentions his experience at abduction and adduc- tion at a distance of six feet. This counsel, to determine the insufificiency at greater distances, judging from the literature of text-books, has been mainly disregarded, and indeed Graefe himself considered it of secondary, if not in most cases of little importance. The facts remain that in respect to this one test for a single condition there is not a well-established rule or custom. Even were complete uni- formity observed in the examinations or records of this condition of the ocular muscles, this method is quite inade- quate for the determination of several other conditions, and, as will be seen hereafter, extremely unreliable even for this one. No just appreciation of the muscular balance can be arrived at while the accommodation is considerably exer- cised. Hence the principal determinations should be made at such distance as to render the accommodation practically relaxed, and while the determination of the inclination of the visual lines in the act of accommodation may be of im- portance, and may throw some light upon the false tenden-