Also see 9.4, Acute Angle Closure Attack.

1. Perform prelaser peripheral iridotomy (LPI) gonioscopy to assess the baseline angle.

2. Inform the patient that they may experience ghost imaging after LPI due to the newly created iris defect. Preference for creation of the LPI at 3 and 9 o’clock to avoid the eyelid margin and prismatic tear film effect theorized to cause ghost images. Superior LPI discouraged even if completely covered by upper eyelid due to high rate of postoperative dysphotopsias.

3. Pretreat the eye with one drop each of apraclonidine 1% and pilocarpine (1% for lightly pigmented irides and 2% for darkly pigmented). As an alternative to pilocarpine, some ophthalmologists prefer to shine a bright light into the fellow eye immediately before engaging the laser or to employ bright ambient light. This allows for physiologic constriction of the operative pupil.

4. Recommended laser settings:

   • Power: 4 to 7 mJ (usually for a total of 12 to 21 mJ).

   • Spot size: 10 to 70 mm.

   • Shots/pulse: 3.

5. Anesthetize the eye (e.g., proparacaine drops).

6. Place an Abraham yttrium–aluminum–garnet (YAG) iridotomy contact lens cushioned with 2.5% hydroxypropyl methyl cellulose or lidocaine gel, positioning the magnification button above the anticipated site of iris penetration.

7. Focus the YAG beam on the predetermined iris location (see #2, above). Focus within an iris crypt if possible (see Figure A.15.1).

   Figure A.15.1: Laser peripheral iridotomy.

   

8. Engage the laser. There will be a gush of posterior iris pigment when the iris is completely penetrated. If not penetrated, advance the YAG beam to refocus on the newly created crater. Re-engage the laser until the iris is completely penetrated.

9. Administer one drop of prednisolone 1% and apraclonidine 1% after laser treatment.

10. Check post-LPI intraocular pressure. 

11. Treat inflammation with prednisolone 1% q.i.d. for 4 to 7 days. If the LPI required a significant amount of power (e.g., more than six triple shots), taper the steroids before discontinuation to prevent rebound inflammation.

12. Have the patient return within 1 to 2 weeks for IOP measurement, iridotomy evaluation, and gonioscopy.

NOTE Darker irides usually require more total power. Always start with a lower power and titrate up as needed for each individual patient. Pretreatment with an argon laser prior to YAG laser therapy is an option for patients with darker, thicker irides or concern for intraoperative bleeding. The argon laser coagulates the tissue to reduce bleeding and thins the iris, thus encouraging easier YAG laser penetration with less applied energy. Utilize spot size 50 um with an escalating power beginning at 300 mJ, 50 laser applications to 600 mJ, 50 laser applications, and finally 900 mJ, 50 laser applications with YAG laser to follow (as above).

NOTE Keep the lens perpendicular to the YAG beam to ensure good focus and laser concentration.