Angle-Closure Glaucoma: Iridotomy

Core Messages

››When performing peripheral laser iridotomy, different laser settings and laser sources may be necessary depending on the iris color and thickness.

››If it is difficult to penetrate the iris to complete an iridotomy, various adjustments can be made to laser settings.

››Complications of laser iridotomy vary from tran­ sient to long-term.

››A surgical iridectomy is always an option if laser iridotomy is not possible.

55.1  What Settings Should Be Used

to Perform Laser Peripheral

Iridotomy (LPI)?

To avoid transient intraocular pressure (IOP) elevation, 1% apraclonidine hydrochloride ophthalmic solution should be administered 1 h before LPI. Brimonidine 0.15–0.2% has also been reported to be effective in preventing a transient IOP elevation associated with LPI [1, 2]. The more dilated a pupil is, the thicker the iris stroma will be and the higher the laser power necessary to complete the LPI. Therefore, the pupil should be maximally constricted before the procedure. For this purpose, 1–2% pilocarpine ophthalmic solution should be administered 30 min to 1 h before the procedure is

K. Kashiwagi

Department of Ophthalmology, University of Yamanashi, Chuo, Yamanashi, Japan

e-mail: kenjik@yamanashi.ac.jp

started. Shining a bright light in the fellow eye during the procedure will also accomplish pupil constriction by the consensual light reflex. IOP should be controlled as much as possible before the procedure. Steroid ophthalmic solution should be administered if there is inflammation in the anterior chamber.

55.1.1  Settings for Argon LPI

An LPI-specific laser contact lens, such as the Abraham lens, that has a high power plus segment should be used. This lens helps to concentrate the laser energy onto the iris and prevents stray energy from reaching the posterior segment after penetration. In general, argon LPI is performed in two steps (Table 55.1). The purpose of the first step is to contract iris tissue. The purpose of the second step is to penetrate the iris and cleanup the LPI. In general, the first step employs a larger spot size, longer duration, and lower power, while the second step employs a smaller spot size, shorter duration, and higher power. Once penetration is confirmed in the second step, for final touch-up of the iridotomy the laser settings can be changed to a longer duration and lower power.

55.1.2  Settings for Nd-YAG LPI

One should again use a lens compatible with the Nd-YAG laser. An Abraham iridotomy lens works well. Laser power for Nd-YAG LPI varies depending on the particular laser used. One should refer to the laser’s manual to confirm the appropriate power. In general, the number of pulses is between 1 and 4 and laser