For tenotomy the eye is cocainized and the conjunctiva seized over the insertion of the muscle to be operated upon, and incised with a snip of the scissors. The incision may be small-4 or 5 millime tres (subconjunctival method)—or large S or 10 millimetres (open method). The subconjunctival tissue is then similarly raised and snipped through, down to the sclera. A strabismus-hook is now intro duced beneath the tendon, and made to lift it from the sclera. One blade of fine, but blunt-pointed, scissors is then slipped beneath the tendon close to its insertion, and the tendon is divided at this point by the scissors.
For a partial tenotomy a small con junctival incision is made over the centre of the tendon at its insertion, after which the tendon itself is caught up with the forceps and snipped through. Then, through the small central opening so made, a small strabismus-hook is intro duced and the tendon divided on either side, until only a thin margin remains, which can be readily stretched with the hook. The subsequent stretching of these margins permits a slight retraction of the whole tendon.
To increase the effect of a tenotomy by permitting a greater retraction of the divided tendon, its lateral connections may be divided and the tendon thus isolated from all its attachments that indirectly connect it with the eyeball. Another measure is to keep the eye forcibly rotated away from the tenoto mired muscle by what is called the thread operation. In this a suture is inserted near the divided muscular insertion and made fast over a roll of adhesive plaster so as to keep the eye in position for the divided tendon to slip as far back as pos sible.
A dvancement of the ocular muscles is done in several different ways. The natural insertions of the recti tendons are from five to nine millimetres back from I the margin of the cornea. The common operation is done through a free incision parallel to the corneal margin. The ten don is isolated, raised from the globe, its insertion divided, and brought forward to or near the corneal margin, where it is fixed by sutures. The sutures may be passed through firm scleral tissue or may only include conjunctiva and subcon junctival tissue, one passing above and another below the cornea. The former give the more certain and definite attach ment, but the latter are easier to insert. When a marked deviation is to be cor rected, advancement of one muscle is ac companied by tenotomy of its direct antagonist. Sometimes a portion of the advanced tendon is cut off (muscle-short ening). Sometimes the tendon is not divided at its insertion, but is folded upon itself, and so shortened (tendon- I tucking). Some operators do not at tempt to isolate the tendon, but pass su tures through the conjunction and cap sule of Tenon. This is spoken of as capsular advancement.
After an operation for strabismus it usually is best not to keep the operated eye bandaged for more than a few hours, or, at most, a day or two. It should be brought into use with the other eye as quickly as possible, and correcting lenses worn constantly, and such use made of the eyes, or such orthoptic exercises re sorted to, as will favor the perfecting of binocular movements and binocular vision.
Prisms, aside from their use as means of securing orthoptic exercise and train ing, are of value in relieving from some of the consequences of strabismus. In actual lateral squint they are scarcely ap plicable, because the squint is usually of such high degree that the necessary prism would be too thick and heavy to wear. But for vertical strabismus, or for latent squint, they are often of great practical service. The apex, or thin part, of the prism is turned iu the direction in which the eye turns or tends to turn. Thus, for right hyperphoria the prism for the right eye would be turned with its edge up, its base down. Turned in this way the prism does not "correct," but rather "permits" the deviation. But the prism removes the unpleasant effects of such a deviation, such as diplopia, or the strain of the ocular muscles neces sary to preserve parallelism of the visual axes. Prisms may be valuable aids in establishing binocular vision after an op eration on the eye-muscles or during re covery from paralysis of one or more of the ocular muscles.
In personal operation in cases of strabismus conjunctival incision is made close to the cornea, so as to leave no con junctiva at this spot. The muscle to be advanced is then slightly separated from the surrounding tissue, but not ex tensively freed. A pair of squint forceps is now applied, and two silk sutures are put into the muscle rather far back, and the latter is divided between the forceps and the sutures. The tendon is cut right away from its attachment tc the sclera. The sutures are then brought forward and inserted well into the episcleral tis sue, and as close to the corneal limbus as possible. If, now, the eye is rotated toward the divided muscle by an assist ant, the operator can tighten the sutures as much as possible. thus bringing the cut end of the muscle close to. or even overlapping, the cornea. In the latter case the free end may be incised in the middle. parallel to its fibres, so that the divided ends come to lie on each side against the margin of the cornea. In convergent squint atropine is applied to both eyes so as to induce more complete rest. Both eyes are bandaged for five days at least in divergent strabismus. and for several more days in convergent strabismus, so that there shall he no in ducement for the patient to use his two internal recti together. As soon as the advanced muscle or muscles are firmly attached, one eye is left open; and, after one or two weeks, methodical exercises of convergence are practiced with the proper correcting lenses before the eyes. It is important that the patient upon whom this operation is performed should be kept in bed with both eyes bandaged for the first few days. E. Landolt (Ar chives of Ophthal., Jan., '97).