Mastering Iridotomy: A Comprehensive Surgical Approach to Managing Angle-Closure Glaucoma

Iridotomy is a critical ophthalmic procedure often performed to prevent or treat angle-closure glaucoma, a condition that can lead to irreversible vision loss if left untreated. This article delves into the nuances of iridotomy, providing a detailed exploration of its indications, preoperative evaluation, contraindications, surgical techniques, postoperative care, potential complications, and more. Designed to cater to surgeons, this comprehensive guide also covers the latest advances and offers practical insights into the cost, prognosis, and alternatives associated with iridotomy.

Indications for Iridotomy

Iridotomy is primarily indicated in the management of angle-closure glaucoma or its variants, such as primary angle-closure suspect (PACS), primary angle-closure (PAC), and primary angle-closure glaucoma (PACG). The procedure is also indicated in patients with pupillary block, where the flow of aqueous humor between the posterior and anterior chambers is impeded, leading to a rise in intraocular pressure (IOP).

Primary Indications:

• Acute Angle-Closure Glaucoma: This is an ophthalmic emergency characterized by sudden onset of pain, blurred vision, and increased IOP. Iridotomy is performed to relieve the pupillary block and reduce IOP.
• Chronic Angle-Closure Glaucoma: In cases where the angle gradually narrows, leading to chronic IOP elevation, iridotomy is performed as a preventive measure.
• Pupillary Block: Patients with anatomical predispositions leading to pupillary block are candidates for iridotomy to prevent the development of angle-closure glaucoma.
• Prophylactic Iridotomy: For patients with narrow angles but no significant rise in IOP, a prophylactic iridotomy may be recommended to prevent future angle closure.

Preoperative Evaluation

A thorough preoperative evaluation is essential to identify candidates for iridotomy and to plan the procedure effectively. The evaluation typically includes:

1. Comprehensive Eye Examination: Assessing visual acuity, anterior segment anatomy, and IOP.
2. Gonioscopy: This is a critical tool in diagnosing angle-closure glaucoma and determining the degree of angle closure. It helps identify the presence of peripheral anterior synechiae (PAS), which may influence the surgical approach.
3. Optical Coherence Tomography (OCT): Anterior segment OCT provides a detailed view of the iridocorneal angle and the depth of the anterior chamber, assisting in the assessment of the risk for angle closure.
4. Ultrasound Biomicroscopy (UBM): UBM is useful in evaluating the structures of the anterior segment, including the ciliary body and iris, and can help in planning the iridotomy site.
5. Assessment of Pupillary Block: Identifying the extent of pupillary block and determining whether it is the primary mechanism leading to angle closure.

Contraindications

While iridotomy is a relatively safe and effective procedure, it is contraindicated in certain situations:

• Corneal Opacities: Significant corneal opacities can hinder the surgeon's ability to visualize the iris, making the procedure risky.
• Flat Anterior Chamber: A shallow or flat anterior chamber may increase the risk of complications, such as corneal damage.
• Active Inflammation: Ocular inflammation, such as uveitis, can increase the risk of postoperative complications and is a relative contraindication.
• Peripheral Anterior Synechiae (PAS): Extensive PAS may limit the effectiveness of iridotomy, as the angle closure may be caused by factors other than pupillary block.
• Non-Pupillary Block Mechanisms: If angle closure is due to mechanisms other than pupillary block, such as plateau iris syndrome, alternative treatments should be considered.

Surgical Techniques and Steps

There are two primary methods of performing an iridotomy: laser iridotomy and surgical iridectomy. The choice of technique depends on the clinical scenario, the surgeon's expertise, and the available resources.

Laser Iridotomy: This is the most common technique used for iridotomy. It involves creating a small hole in the peripheral iris using a laser, typically the Nd

or argon laser.

Steps Involved:

1. Patient Preparation: The patient is seated at a slit lamp, and topical anesthesia is administered. Pilocarpine drops may be used to constrict the pupil, reducing the iris's thickness and making the procedure easier.
2. Gonioscopy Lens Application: A gonioscopy lens with a laser window is placed on the cornea to stabilize the eye and focus the laser beam.
3. Laser Application: The laser is focused on the peripheral iris, usually in the superior quadrant to reduce postoperative visual disturbances. Several shots may be needed to create a patent opening.
4. Post-Laser Examination: After the iridotomy, the patency of the opening is confirmed using gonioscopy or direct visualization.

Surgical Iridectomy: This is a more invasive procedure, usually reserved for cases where laser iridotomy is not feasible or has failed. It involves making a small incision in the cornea to access the iris and physically remove a portion of it.

Steps Involved:

1. Incision: A small corneal or limbal incision is made using a surgical blade.
2. Iris Grasping: A portion of the peripheral iris is grasped with forceps and excised with scissors.
3. Closure: The incision is closed with fine sutures, and the patency of the iridectomy is confirmed.

Postoperative Care

Postoperative care is crucial to ensure the success of the procedure and to minimize complications. The following steps are typically taken:

1. Topical Medications: Patients are prescribed topical corticosteroids to reduce inflammation and prevent synechiae formation. Antibiotic drops may also be used to prevent infection.
2. IOP Monitoring: Intraocular pressure should be monitored closely in the immediate postoperative period. A transient spike in IOP is common after laser iridotomy and may require short-term treatment with IOP-lowering medications.
3. Gonioscopy: Postoperative gonioscopy is performed to confirm the patency of the iridotomy and to ensure that the angle has opened adequately.
4. Patient Education: Patients should be informed about the symptoms of potential complications, such as pain, blurred vision, or persistent redness, and instructed to seek immediate medical attention if they occur.

Potential Complications

While iridotomy is generally safe, it is not without risks. Complications can arise both during and after the procedure, and surgeons should be vigilant in monitoring for these potential issues.

Intraoperative Complications:

• Corneal Burns: The laser energy can cause corneal burns if the gonioscopy lens is not properly aligned or if the cornea is not adequately lubricated.
• Hyphema: Bleeding from the iris is a common complication, particularly if the laser energy disrupts a blood vessel.

Postoperative Complications:

• IOP Spike: A transient increase in IOP is common after iridotomy, particularly with the Nd

laser. This may require temporary treatment with IOP-lowering medications.

• Inflammation: Inflammation of the anterior segment, or iritis, can occur after the procedure and is typically managed with corticosteroids.
• Dysphotopsia: Some patients may experience visual disturbances, such as glare or halos, due to light passing through the iridotomy.
• Closure of Iridotomy: In rare cases, the iridotomy may close spontaneously, necessitating a repeat procedure.

Different Techniques

The choice of technique for iridotomy depends on various factors, including the surgeon's experience, the patient's anatomy, and the available equipment.

Nd

Laser Iridotomy: This is the most widely used technique due to its precision and ability to create a clean, small opening in the iris. The Nd

laser is particularly effective in patients with darker irides, where the pigment absorbs the laser energy efficiently.

Argon Laser Iridotomy: The argon laser can be used alone or in combination with the Nd

laser. It is particularly useful in patients with lighter-colored irides, as the lower energy levels reduce the risk of complications such as iris bleeding.

Combined Argon and Nd

Laser: In some cases, a combined approach may be used. The argon laser is applied first to thin the iris, followed by the Nd

laser to create the iridotomy. This technique can reduce the risk of postoperative IOP spikes.

Surgical Iridectomy: While less commonly performed, surgical iridectomy remains a viable option in cases where laser techniques are not suitable. This may include patients with corneal opacities, extensive peripheral anterior synechiae, or failed laser iridotomy.

Prognosis and Outcome

The prognosis for patients undergoing iridotomy is generally favorable, particularly when the procedure is performed early in the disease process.

Acute Angle-Closure Glaucoma: In cases of acute angle-closure glaucoma, timely iridotomy can be sight-saving, relieving IOP and preventing optic nerve damage. The success rate is high, with most patients achieving long-term control of their IOP.

Chronic Angle-Closure: In patients with chronic angle-closure, the prognosis depends on the extent of optic nerve damage at the time of diagnosis. Iridotomy can effectively halt the progression of angle closure, but visual field loss that has already occurred is usually irreversible.

Prophylactic Iridotomy: For patients with narrow angles but no glaucoma, prophylactic iridotomy offers a preventive approach, with a low risk of complications and a high success rate in preventing angle-closure glaucoma.

Alternative Options

While iridotomy is the standard treatment for angle-closure glaucoma, alternative options may be considered in certain cases:

Lens Extraction: For patients with significant lens-induced angle closure, such as phacomorphic glaucoma, cataract extraction may be the preferred treatment. This can deepen the anterior chamber and open the angle, potentially eliminating the need for iridotomy.

Laser Peripheral Iridoplasty (LPI): LPI involves applying laser burns to the peripheral iris, causing it to contract and pull away from the trabecular meshwork. This can be an effective alternative in cases where iridotomy is not feasible or has failed.

Trabeculectomy: In patients with advanced glaucoma or those who fail to respond to iridotomy, trabeculectomy or other filtering surgeries may be necessary to control IOP.

Average Cost

The cost of iridotomy can vary widely depending on geographical location, the type of facility, and whether the procedure is performed in conjunction with other treatments. In the United States, the cost of laser iridotomy typically ranges from $1,000 to $2,000 per eye, including preoperative and postoperative care. Surgical iridectomy, being more invasive, may be more expensive, particularly if performed in a hospital setting.

Recent Advances

Recent advances in the field of iridotomy have focused on improving patient outcomes and reducing the risk of complications:

Laser Technology: Newer laser systems offer improved precision and control, reducing the risk of complications such as IOP spikes and dysphotopsia. The development of femtosecond lasers, which allow for even more precise tissue ablation, is an area of ongoing research.

Imaging Techniques: Advances in imaging, such as high-resolution anterior segment OCT, have enhanced the ability to assess the angle and plan the iridotomy. These imaging modalities allow for better preoperative planning and postoperative monitoring.

Minimally Invasive Glaucoma Surgery (MIGS): While not a direct alternative to iridotomy, MIGS procedures, such as the use of micro-stents, offer new options for managing angle-closure glaucoma in conjunction with or following iridotomy.