Iridectomy

Definition

Iridectomy is the surgical excision of a full-thickness portion of the iris. It creates a permanent opening (hole) in the iris that bypasses the pupil, allowing aqueous humor to flow freely from the posterior chamber to the anterior chamber.

Kanski's Clinical Ophthalmology, 10th ed.
Goodman & Gilman's Pharmacological Basis of Therapeutics

Types

Type	Description
Peripheral iridectomy	A small hole at the iris periphery; the most common type for glaucoma
Sector iridectomy	A wedge-shaped removal of a larger iris segment; used for iris tumors
Complete iridectomy	Removal of the entire iris (rare; reserved for diffuse pathology)
Iridocyclectomy	Iridectomy extended to include the ciliary body for tumors invading the angle

Indications

1. Angle-Closure Glaucoma (Primary indication)

The preferred management for angle-closure glaucoma is to create another pathway for aqueous humor to pass from the posterior to the anterior chamber. This equalizes pressure across the pupil, flattens the iris, and - if the iris is not adherent to the trabecular meshwork - opens the angle, reestablishes outflow, and lowers IOP. This is done by making a hole in the peripheral iris by either laser (laser iridotomy) or surgical incision (surgical iridectomy). - Goodman & Gilman's, p. 249

Narrow-angle (acute congestive) glaucoma is nearly always a medical emergency: drugs control the acute attack, but the long-range management is surgical, e.g., peripheral or complete iridectomy.
After IOP is controlled medically (IV acetazolamide, topical beta-blockers), definitive treatment is peripheral laser iridotomy/iridectomy. - Swanson's Family Medicine Review; Tintinalli's Emergency Medicine

2. As Part of Trabeculectomy

A peripheral iridectomy is created during trabeculectomy to prevent blockage of the internal sclerostomy (the surgically created filtration hole). Some surgeons omit this step in pseudophakic eyes, but there remains a small risk of iris prolapse into the sclerostomy site. - Kanski's Clinical Ophthalmology, p. 434

3. Iris Tumors

Sector iridectomy for small tumors
Iridocyclectomy for tumors invading the angle
Alternatives include brachytherapy or proton beam radiotherapy. - Kanski's Clinical Ophthalmology, p. 872

4. Anterior Chamber IOL Implantation

An iridectomy is created when inserting an anterior chamber (AC) IOL (e.g., after posterior capsule rupture during cataract surgery) to prevent pupillary block by the lens. - Kanski's Clinical Ophthalmology

Laser Iridotomy vs. Surgical Iridectomy

Feature	Laser Iridotomy	Surgical Iridectomy
Method	Nd:YAG or argon laser makes a hole in iris	Incisional excision of iris tissue
Setting	Outpatient, office-based	Operating room
Primary use	Pupillary-block angle-closure glaucoma	When laser fails or for other indications
Backup role	First-line	If laser fails to maintain a viable iridotomy

Surgical iridectomy is the definitive method of preventing further pupil block and may be required if laser fails to maintain a viable iridotomy. - Kanski's Clinical Ophthalmology

Mechanism of Action in Angle-Closure

In angle-closure glaucoma:

Aqueous builds up in the posterior chamber (ball-valve mechanism at pupil)
This bows the iris anteriorly (iris bombé)
The iris root presses against the trabecular meshwork, blocking outflow
IOP rises sharply

An iridectomy/iridotomy bypasses the pupillary block → equalizes pressure across the iris → iris flattens → angle reopens → outflow restored.

Complications

Non-patent iridectomy: After trabeculectomy, a non-patent peripheral iridectomy can cause pupillary block with iris bombé and high IOP with a flat bleb
- Treatment: Nd:YAG laser to the pigment epithelium at the iridectomy site, or creation of a new laser iridotomy. - Kanski's Clinical Ophthalmology, p. 434
Haemorrhage (hyphaema)
Cataract (sector iridectomy for tumors)
Diplopia/monocular double vision: An iridectomy defect is listed among causes of monocular diplopia due to an extra optical aperture. - Wills Eye Manual
Patients who have had an iridectomy can safely receive tricyclic antidepressants (which would otherwise be risky in narrow-angle glaucoma). - Kaplan & Sadock's Comprehensive Textbook of Psychiatry

Anesthesia Considerations

Peripheral iridectomy is classified as an open-eye surgical procedure, requiring careful anesthetic management to avoid raised IOP (e.g., from coughing, vomiting, or succinylcholine). - Morgan & Mikhail's Clinical Anesthesiology, 7th ed.

This is a shared conversation. Sign in to Orris to start your own chat.