Second step. Iris forceps are inserted and the flap of iris and capsule is withdrawn and as much of it removed as possible. A more or less triangular opening usually results.
Ziegler’s operation.
Instruments. Ziegler’s knife needle, speculum, fixation forceps.
The object of the operation is to cut a V-shaped flap in the iris and underlying capsule, folding the flap backwards on its base so as to form a triangular opening in the iris membrane to serve as a pupil.
First step. The knife needle is entered at the corneo-sclerotic junction with the blade turned on the flat and is passed completely across the anterior chamber to within 3 mm. of the apparent iris periphery. The knife is then turned edge downwards, and carried 3 mm. to the left of the vertical plane (Fig. 104).
Second step. The point is now allowed to rest on the iris membrane, and with a dart-like thrust the membrane is pierced. Then the knife is drawn gently up and down with a saw-like motion, without making much pressure on the tissue to be cut, until the incision has been carried through the iris tissue from the puncture in the membrane to just beneath the corneal puncture. This movement is made wholly in a line with the long axis of the knife, the shank passing to and fro through the corneal puncture, loss of the aqueous being avoided in the manipulation (Fig. 105).
Third step. The pressure of the vitreous will now cause the edges of the incision to bulge open immediately into a long oval. The knife-blade is raised until it is above the iris membrane, and is then swung across the anterior chamber to a corresponding point on the right of the vertical plane. Owing to the disturbance in the relation of the parts made by the first cut, this point is somewhat displaced and the second puncture must be made 1 mm. further over.
| Fig. 105. Iridotomy by Ziegler’s Method. Showing the first incision and the position of the second. | Fig. 106. Iridotomy by Ziegler’s Method. Final step; the triangular flap of iris attached at its base is turned downwards. |
Fourth step. With the knife-point again resting on the membrane, a second puncture is made and the incision is carried rapidly forward by the sawing movement to meet the extremity of the first incision at the apex of the triangle, thus making a V-shaped cut. Care must be taken that the pressure of the knife-edge on the tissue shall be most gentle, and that the second incision shall terminate a trifle inside the extremity of the first, in order that the last fibres may be severed and thus allow the apex of the flap to fall down behind the lower part of the iris membrane (Fig. 106). When the operation has been completed the knife is turned on the flat and withdrawn.