A cooperative patient and an adequate view of the iris are necessary. Lowering the IOP before iridotomy is helpful in reducing corneal edema that may be present in acute angle closure and in allowing perfusion of the iris constrictor muscle. IOP reduction can also help to alleviate pain, which in turn improves patient cooperation. Topical, oral, and intravenous ocular hypotensive medications can all be used to lower IOP, and pain control can also be achieved with oral analgesics. IOP reduction can also be achieved by performing a careful paracentesis. Pretreatment of the iris with a green laser is useful in patients with a higher risk of bleeding (eg, in patients on anticoagulation or antiplatelet therapy).
A topical hypotensive agent is administered before the iridotomy to prevent postoperative IOP spikes. Pilocarpine is instilled to constrict the pupil, which in turn stretches the iris and allows for easier iris penetration by the laser. However, pilocarpine may be ineffective in patients with prolonged acute angle closure resulting in iris constrictor muscle ischemia.
An Abraham iridotomy lens with methylcellulose is used in this procedure. Prior to performing iridotomy, the surgeon should evaluate the iris to consider where to place the iridotomy, which should be located as far peripherally as possible. Making the iridotomy in an area where the iris is thinner (an iris crypt, for example) lessens the amount of energy needed. The Nd:YAG and green lasers can be used to create an iridotomy. In patients with thicker and darker irides, some surgeons advocate pretreatment with a green laser to thin the iris before using the Nd:YAG laser to penetrate the iris (Table 13-3). When the laser pierces through the iris, a release of fluid and pigment into the anterior chamber will usually be seen. Transillumination is useful in locating the iridotomy but does not signify patency. The iridotomy should be of sufficient size. There is evidence that creating a larger iridotomy in eyes with small iridotomies can help deepen the anterior chamber.
Table 13-3 Laser Settings for Peripheral Iridotomy and Iridoplasty
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.