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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    down before one eye, is identical with that for uniting with its base up before the other. If we consider the results of the examination in the horizontal direction in relation to those in the vertical, we shall be able to form an opinion concerning the presence or absence of equilibrium, and, if manifest deviating tendencies exist, of the direction and extent of such tendencies. It is not, however, to be as- sumed that these indications are absolute. They are, as a rule, correct so far as they are positive, but they do not of necessity permit us to determine the absolute degree of deviating tendency. Here, as in hyperopia, a latent anomalous tendency may exist but, unlike hyperopia, we have here no means of ascertaining at a single examination the absolute departure from the ideal standard. Notwith- standing no proof may have been obtained by these trials, latent tendencies of great importance may exist. Our tests determine the manifest conditions only, and it is a safe rule to consider that the deviating tendencies are never less than are shown by our trials, but that they may greatly exceed that which we are able to demonstrate. Having determined in this manner the approximate con- dition of muscular adjustment when no effort of accommo- dation is demanded, we may proceed to a similar examina- tion at a near point. For convenience we may adopt the distance at which the majority of people hold the page when reading. Tests made at the distance of one half metre will sufificiently indicate the tendencies when the eyes are in accommodation for near work. Here prisms of greater angle than those employed for producing diplopia at a distance will be required, but the determinations may be made in the same general manner. Presbyopic persons should be supplied with reading-glasses in making this test, and the glasses for myopes should be such as are suited for the prescribed distance. Terms by which we may express all the deviating tenden- cies which may be discovered in the manner indicated have been wanting. The imperfections of the nomenclature for ocular muscular anomalies have been discussed by myself in the articles already referred to, and a system of terms has