An endeavour to show that insufficiency of the internal recti muscles and myopia have been erroneously associated : and that the muscular asthenopia of myopia is not the result of such insufficiency, but of the anomaly of refraction / by Samuel Theobald.

  • Theobald, Samuel, 1846-1930.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: An endeavour to show that insufficiency of the internal recti muscles and myopia have been erroneously associated : and that the muscular asthenopia of myopia is not the result of such insufficiency, but of the anomaly of refraction / by Samuel Theobald. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    AN ENDEAVOUR TO SHOW THAT INSUFFICIENCY OF THE INTER- NAL RECTI MUSCLES AND MYOPIA HAVE BEEN ERRONEOUSLY ASSOCIATED; AND THAT THE MUSCULAR ASTHENOPIA OF MYOPIA IS NOT THE RESULT OF SUCH INSUFFICIENCY, BUT OF THE ANOMALY OF REFRACTION. By SAMUEL THEOBALD, M D., OPHTHALMIC AND AURAL SURGEON OF THE EYE AND EAR DISPENSARY, BALTIMORE. Examined by means of the usual tests, which are employed for tlie detection of insufficiency of the internal recti muscles, there are but few cases of myopia which will not furnish the conditions considered sufficient to demonstrate the existence of this affection. Hence it is that, as the accuracy of these tests has been very generally accepted, insufficiency of the internal recti muscles has come to be looked upon as the rule, rather than the exception, in myopia; a recent writer upon this subject,^ stating that it exists in, perhaps, nine-tenths of all the cases of progressive my- opia ; while the same writer quotes Giraud Teulon as saying, that he regards the existence of staphyloma posticum “rather as an evidence of the insufficiency than of the myopia.” First, then, let us inquire what are the tests relied upon. There are two which are usually employed. In the first and less accurate one, the subject of the examination is directed to regard an object held in the median line at a short distance from the eyes (8 or 10). One eye is then excluded from vision by the hand, or by a screen placed before it, and the movement which it makes upon such exclusion is noted. If it is found to rotate outwards, while the uncovered eye continues in its former position, so that, when the hand is removed, a movement of convergence is required in order to restore binocular vision, weakness or insufficiency of the internal recti is assumed. The second test, which is more relied upon, and is based upon the inabil- ity of the eyes to overcome vertical diplopia, was devised by Yon Graefe. A black dot, with a fine line passing vertically through it, is drawn ‘ Dr, R. H. Derby, of New York, in an article upon Progressive Myopia and its Operative Cure, in the N. Y. Medical Journal, June, 1873.