The progress of ophthalmic surgery : from the invention of the ophthalmoscope (in 1851) up to the present time : being an oration delivered before the North London Medical Society on February 11, 1863 / by John Zachariah Laurence.

  • Laurence, John Zachariah, 1828?-1870.
Date:
1863
Catalogue details

Licence: Public Domain Mark

Credit: The progress of ophthalmic surgery : from the invention of the ophthalmoscope (in 1851) up to the present time : being an oration delivered before the North London Medical Society on February 11, 1863 / by John Zachariah Laurence. 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.

    9/26 (page 7)
    an example of concurrent (or accommodative) action of the ocular muscles. In either case, if the natural equilibrium of force of the muscles is disturbed, the optic axes are no longer directed to the same points, and double vision ensues. If a nouWe ^ ' vision. convergent squint is thus induced, the resultant right-hand image belongs to the right eye, the left-hand one to the left. But if a divergent squint arises (either from excessive action of the external rectus, or deficient of the internal rectus), then the images are no longer corresponding, but crossed ones—i.e. the right-hand image will be perceived by the left eye, and vice versa. We can artificially produce these double images, either by mechanical pressure on the eyeballs, by their voluntary distantial misconvergence, or by prismatic glasses. In the above instances the double images exhibited simply a lateral separation; but you will readily understand that if the superior or inferior recti or obliqui be involved, the double images will also present corresponding diflFerences of elevation and inclination. You will further easily conceive that the ocular muscles may be so slightly affected (paralysed or contracted) as to render any deviations of direction of the eyeballs quite inappreciable to your eye. In such a case, we may, by an inverted order of ratiocination, utilise the relative positions of the double images for the determination of which of the muscles, and how, are affected ?—in a word, substitute for an objective, a subjective method of diagnosis. It is in the elaboration of such often highly complex problems, their solution by different degrees of tenotomy, by prismatic glasses, &c., that Prof. v. Grafe has so largely contributed to our exact knowledge of the subject. I may here remark, that for the cure of squint I have prac- strabis^ tised both the subconjunctival section of the ocular muscles and the old operation of Dieffenbach; and I must confess that, prepossessed as I was at first with the former operation, I have again reverted to the older one, which I believe, per- formed cautiously, with the addition of an ad libitum limiting suture, surpasses the subconjunctival one—not in certainty, but in the power it affords us of very nearly regulating our