Operation. Under adrenalin and cocaine. First step. The patient is made to look away from the side on which is the muscle to be advanced, and the conjunctiva over the muscle is freely divided with scissors, by a curved incision with the convexity towards the cornea, and dissected back.
Second step. The capsule of Tenon is button-holed by a small incision well above or below the tendon. A tenotomy hook is passed beneath the tendon and its expansion and brought out through a small hole in Tenon’s capsule on the opposite side of the tendon. The smooth blade of Prince’s forceps is then inserted in place of the hook, and the tendon with its expansion is grasped between the blades. The forceps are given to an assistant, who should avoid all traction on the muscle. The eye is then rotated in the direction of the muscle to be advanced, and tenotomy of the opposing muscle is performed by the open method.
Fig. 133. Advancement by the Three-stitch Method. Showing the sutures in position. A firm hold on the sclerotic to the corneal side of the wound is essential to the success of the operation.
Third step. The muscle to be advanced and its expansion, which are clamped between the blades of Prince’s forceps, are separated from the globe with the scissors and given again to the assistant to hold. Three strong silk sutures are passed in the following order, middle, upper, and lower, first through the conjunctival and episcleral tissue on the corneal side of the wound and then as far back as possible through the muscle and out through the conjunctiva near the cut margin on the other side of the wound (Fig. 133). Care should be taken that the middle stitch is passed through the episcleral tissue exactly opposite the horizontal plane of the cornea and the central portion of the tendon. The portion of the tendon and capsule within the grasp of the forceps is then removed with scissors by cutting close to the blades of the Prince’s forceps, taking care not to cut the sutures.
Fourth step. The middle suture should be first tightened to the extent required to bring the eye straight. The upper and lower sutures are then tied.
If, on testing with the Maddox rod, the error be found to be slightly over-corrected by the advancement, the eye can be drawn back by taking a firm hold with the conjunctival stitch over the tenotomy wound. The conjunctival stitch may be removed on the fourth day, but the stitches holding the advanced muscle in position should not be removed till after the tenth day. Atropine in both eyes is desirable, especially when there is any tendency to convergence. Glasses should be worn on uncovering the eyes.
Complications. 1. The eyes may not be straight after the operation. No further operation for rectification should be undertaken for at least two or three months. If there be a tendency to convergence, glasses should be worn and atropine used. Small latent errors may be corrected by prisms. If the muscular error be insufficiently corrected tenotomy may be performed on the other eye. If the muscular error be over-corrected it may also require tenotomy on the other eye, the adjustment by tenotomy being more accurate than that by advancement.
2. Thickening over the site of the advanced muscle usually disappears in a few months.
Other complications as described under tenotomy may occur (see [p. 250]).