Miotic Pupil
In some cases, the cataract operation can be performed in the surgeon's usual manner, with no special measures for the coexisting glaucoma. A previously common problem with cataract surgery in the glaucomatous eye, although one that is less common today, is the irreversible miosis from chronic miotic therapy. This became more important with the advent of phacoemulsification, in which adequate pupillary dilatation is needed to perform the surgery safely and effectively. A wide variety of techniques have been described to surgically enlarge the pupil. One approach is to make a sector iridotomy above, often with two inferior sphincterotomies (62), or multiple sphincterotomies and a peripheral iridectomy (63). If a sector iridotomy is made, some surgeons will elect to close it with sutures after implanting the lens (64,65), although it can be left open if the lens haptics are rotated horizontally away from the iridotomy. One study compared patients with sutured and unsutured sector iridotomies and found no difference in glare sensitivity (66).
Several iris retractors have been developed to mechanically enlarge a miotic pupil (67,68,69,70). One of these instruments is the three- or four-point Beehler Pupil Dilator, which has two or three extendable “microfingers†through 2.5- to 3.0-mm incisions and can dilate a 2- to 3-mm pupil to approximately 6 to 7 mm. Flexible nylon hooks (68,71,72) have also proven to be especially useful for cataract surgery (Fig. 44.1). Other techniques include mechanical stretching of the pupil (70), a variety of iris suture techniques (73,74,75), a maneuver of tucking the iris pillars of a sector iridectomy (76), and a pupil-expanding ring (77). It has also been suggested that phacoemulsification can be performed through a pupil of 4 mm or more if the capsulorrhexis is intact and the nucleus is fractured into small segments in the capsule (78), although success depends on the skill of the surgeon. In addition to stretching the pupil, the iris hooks can be inserted into the capsular bag under the anterior capsule, after performing capsulorrhexis to stabilize the lens capsule in eyes with weak or damaged zonules (e.g., exfoliation syndrome) (79,80,81,82).
