Laser Iridotomy & Cyclodestructive Procedures

Laser Peripheral Iridotomy

A laser peripheral iridotomy (LPI) uses a YAG laser to punch a full-thickness hole through the peripheral iris. That opening equalizes pressure between the posterior and anterior chambers and relieves pupillary block, the mechanism behind angle-closure glaucoma. LPI is the definitive treatment for an acute attack, and it doubles as prophylaxis: the same procedure is done on a fellow eye, or on any eye found to have an anatomically narrow angle before an attack ever occurs.

LPI is performed with a Nd:YAG laser. Argon laser pretreatment is sometimes added first, mainly in thick, dark brown irides, where it makes the YAG perforation easier. The procedure is generally safe, but not risk-free: a transient IOP spike shows up in about one in twenty eyes within the first hour, and a small hyphema from an iris vessel is common and self-limited. For a fellow eye after a first acute attack, the stakes are higher. Left untreated, that eye has a 40% to 80% chance of developing angle closure within five to ten years, which is why prophylactic iridotomy there is standard rather than optional.

Cyclophotocoagulation: Reducing Production Instead of Improving Outflow

Laser trabeculoplasty lowers IOP by improving aqueous outflow. Cyclophotocoagulation does the opposite: it works by destroying secretory ciliary epithelium, cutting aqueous production off at the source. It is generally reserved for refractory glaucoma.

• Transscleral cyclophotocoagulation is the original continuous-wave technique. Excessive destruction of ciliary body tissue causes chronic hypotony, and in severe cases that progresses all the way to phthisis bulbi: a shrunken, non-functional globe. This is the variant most associated with that risk. Postoperative intraocular inflammation, ranging from a mild anterior chamber reaction to severe uveitis, is the more common complication overall and is managed with intensive topical corticosteroids.
• Micropulse transscleral cyclophotocoagulation delivers the same laser energy in repeated short pulses instead of a continuous beam. The pauses between pulses let the tissue cool, which limits collateral thermal damage to adjacent structures and carries a lower risk of inflammation and hypotony than the continuous-wave technique.
• Endoscopic cyclophotocoagulation (ECP) treats the ciliary processes directly, under endoscopic guidance, rather than through the sclera. It shares the same clear corneal incision used for cataract removal, which is why it's often performed as a combined procedure at the time of cataract surgery.