Surgical Peripheral Iridectomy
David L. Epstein, MD, MMM
The second edition of Lectures on Glaucoma makes the following statement:
The first edition of Lectures on Glaucoma contained a detailed description of our preferred technique for doing a peripheral iridectomy. Peripheral iridectomy has become one of the commonly used operations for angle-closure glaucoma. All ophthalmic surgeons are capable of performing the operation well and have developed their own preferred technique. Suturing the wound is now al most universally practiced. For these reasons, we have decided to omit a detailed discussion of technique of iridectomy in this edition.
Since the advent of laser iridectomy, it is now rare for ophthalmology residents to perform a surgical peripheral iridectomy. Yet, as alluded to previously, there are certain situations when it is not possible to employ a laser technique (eg, cloudy cornea) when the ophthalmologist should be able to perform a surgical iridectomy. We should also not forget that there are areas of the world where lasers are not yet available.
Therefore, a few aspects of this surgical technique—often called the most underrated operation in ophthalmology—are presented in this chapter.
TECHNIQUE OF SURGICAL PERIPHERAL IRIDECTOMY
Either a limbal- or fornix-based flap is prepared over approximately 1.5 clock hours in one of the upper quadrants in order to save the other quadrant for possible future filtration surgery (Figure 65-1). The superotemporal quadrant is usually preferred for iridectomy so that, if cataract formation were to occur after a subsequent superonasal quadrant filtering operation, the cataract could be removed more easily from the side rather than from below. We usually prefer a fornix-based flap due to its better limbal exposure.
The key to the operation is the incision. For this purpose, a somewhat rounded knife blade, such as a No. 67 Beaver or No. 15 Bard-Parker (Katena Eye Instruments), is preferred to enter the eye so that it will slide over the iris without perforating it. A sharp blade is best avoided because it is apt to make a small hole in the iris and the iris will then not spontaneously prolapse. The incision must be perpendicular, clean, and wide enough so that the iris will spontaneously prolapse and will easily reposit. An irregular incision will catch iris tissue and prevent repositioning. In making the incision, when one gets the first gush of aqueous humor, one should not immediately withdraw the knife (as is instinct) but should continue to enlarge the opening to a full clock hour. One is more confident in doing this with a rounded rather than a sharp blade.
It is important to do this operation outside the eye rather than to reach inside to grasp the iris. If the incision is wide enough (and the iris is not penetrated by the knife), gentle pressure on the posterior lip of the wound will allow the pressure in the posterior chamber to spontaneously prolapse the iris into the wound, where it should be firmly grasped and cleanly cut. The cut iris tissue is inspected for pigment epithelium to ensure that full thick ness of the iris has been excised. Then, the iris is reposited by exerting a sweeping motion with the irrigator tip across the limbal incision. No instrument is placed into the eye. Repositing the iris is often the most difficult part of the procedure. Preoperative pilocarpine will often aid in this.
Figure 65-1. Technique of surgical peripheral iridectomy. (A) A fornix-based conjunctival flap is prepared with scissors. A knife with a rounded tip is brought forward to make the incision (B), which is perpendicular, clean, and accomplished by a slight rolling motion. After the first gush of aqueous, the incision is slightly extended and is then inspected (C). The anterior lip may be grasped with Colibri forceps, while the iris forceps gently depress the posterior lip (D) so that iris is spontaneously prolapsed into the wound where it is grasped with the iris forceps and is smoothly cut with fine scissors at the wound margin. No instruments should be placed inside the eye. The iris is reposited by a sweeping motion of the irrigator tip across the limbal incision (E). The pupil is observed to be round and the iridectomy patent. The wound and conjunctiva may be then closed by a variety of methods. Shown in (F) and (G) is the technique of incorporating the flap in which the posterior arm of a double-armed suture, having already been placed through the limbal wound, is passed a few millimeters posterior to the edge of the conjunctiva, and then the anterior arm of the same suture is placed (F) through the anterior edge and is then tied (G).
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