Binocular astigmatism / [by H. Culbertson].

  • Culbertson, H. (Howard), 1828-1890.
Date:
[1888]
Catalogue details

Licence: Public Domain Mark

Credit: Binocular astigmatism / [by H. Culbertson]. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    cases of astigmatism before the investigation is regarded as complete. The use of glasses thus adapted has been suc- cessful in practice, with one or two exceptions, and in these the use of cylinders had to be dis- pensed with and spherical glasses employed. This defect in binocular vision does not occur, of course, in all cases of astigmatism ; but obser- vation has taught me that such errors are far from being uncommon. The following explanation offered of binocular astigmatism, seems more rational than any other with which I am familiar: If a perpendicular be raised anteriorly and hor- izontally midway between the eyes from a base line intersecting each fovea centralis; then, in test- ing each astigmatic eye separately, the axis of vision will, in vision 7'emotnni, be parallel to said perpendicular. If the ocular muscles are nor- mally balanced in action, the plane which cuts the visual axis in the cornea will be vertical. In the normal eye, its fellow being covered, during vision proximum, st/ll the visual axis may be par- allel to our perpendicular, and hence the angle of the axis of the cylindrical glass ma}' often be the same in remote and near vision, 7a/ie?i each eye is tested singly. In binocular vision, when astig- matism is present, the distance is so great, in re- mote vision, that the visual axes are each par- allel to our perpendicular and to each other, and when the ocular muscles are harmonious in action, types and astigmatic bars are seen in normal form. So will vision be perfect near at hand, in astig- matism, provided this due balance is maintained in these muscles ; but it is evident that, in prox- imal vision, the interni inferior oblique and su- perior and inferior recti muscles must exercise increased force and act in concert.