What Is Gonioplasty? How Laser Iris Reshaping Works

Gonioplasty is a laser procedure that widens the drainage angle of the eye by shrinking peripheral iris tissue, pulling it away from the internal drain where fluid exits. Also known as argon laser peripheral iridoplasty (ALPI), it serves as a second-line treatment when other approaches fail to open a dangerously narrow angle, and it plays a distinct role in emergency settings where eye pressure spikes to sight-threatening levels. The procedure occupies a specific niche in glaucoma care, and understanding when it helps, when it falls short, and how it compares to related laser treatments matters for anyone facing angle-closure problems.

How the Laser Reshapes the Iris

Inside the eye, fluid called aqueous humor drains through a ring-shaped structure called the trabecular meshwork, located in the angle where the iris meets the cornea. When the peripheral iris bunches forward and blocks that drain, pressure builds. Gonioplasty addresses this by applying carefully placed laser burns to the outermost edge of the iris. These burns cause the iris tissue to contract and flatten, physically pulling the iris root away from the meshwork and reopening the drainage pathway.¹

The laser settings matter. The burns are placed peripherally, using relatively low power, a large spot size, and a long pulse duration. This combination heats the iris stroma enough to shrink its collagen without blowing a hole through the tissue, which is what a different procedure (iridotomy) deliberately does. The goal is contraction, not perforation. A ring of these burns around the iris periphery creates an even pull that opens the angle circumferentially.

Acute Angle-Closure Emergencies

Acute angle closure is one of the true emergencies in eye care. The drainage angle slams shut, eye pressure can double or triple within hours, and the result is severe pain, blurred vision, nausea, and potential permanent optic nerve damage if the pressure is not brought down quickly. Standard first-line treatment involves pressure-lowering eye drops and oral or intravenous medications. When medications alone cannot break the attack, gonioplasty offers a way to rapidly reopen the angle.

In a prospective randomized trial comparing gonioplasty to conventional medical therapy for acute attacks, the laser-treated group had lower eye pressure at 15 minutes, 30 minutes, and one hour after the start of treatment, with the differences being statistically significant. The gap between the two approaches narrowed and became insignificant from two hours onward, suggesting that gonioplasty’s main advantage is speed of onset rather than a fundamentally different endpoint.² That speed can be critical. When pressure is high enough to damage the optic nerve in minutes, getting it down faster buys time.

A study of medically unresponsive acute angle-closure cases found that gonioplasty produced a rapid and significant pressure reduction in all cases, and proved especially useful when laser iridotomy had either failed or could not be performed, often because the cornea was too cloudy from the high pressure to allow a clear shot at the iris.³ This is an important practical point: during an acute attack, corneal swelling frequently makes iridotomy impossible, whereas gonioplasty burns are placed more peripherally and can often still be delivered through the hazy cornea.

Longer follow-up data from a three-year study of medically refractory acute attacks showed that mean pressure dropped from roughly 32 mmHg at enrollment to about 18 mmHg two hours after gonioplasty, fell further to around 15 mmHg by day seven, and stabilized near 16 mmHg at the three-year mark with at least half the angle remaining open.⁴ Those numbers paint a picture of meaningful, sustained pressure control in eyes that had stopped responding to drugs.

Plateau Iris Syndrome

Plateau iris syndrome is probably the condition most closely associated with gonioplasty in day-to-day clinical practice. In this condition, the iris inserts forward on the ciliary body in an abnormal position, pushing the peripheral iris into the drainage angle even after an iridotomy has been performed. Normally, iridotomy resolves angle closure caused by pupillary block, where fluid trapped behind the iris bows it forward. But in plateau iris, the anatomy of the iris root itself is the problem, so making a hole in the iris does not fix the crowding.

The hallmark diagnostic clue is an angle that stays narrow or closed even after a successful iridotomy. Once that pattern is recognized, gonioplasty becomes the treatment of choice.⁵ The laser burns contract the peripheral iris, thinning and flattening it enough to pull it off the drainage structures that the iridotomy could not address.

A study of long-term outcomes found that gonioplasty was highly effective at eliminating the residual angle closure caused by plateau iris syndrome, and that the effect was maintained for years, although a small proportion of patients needed retreatment.⁶ For many patients with plateau iris, the procedure provides lasting relief from the threat of recurrent angle closure after iridotomy alone has proven insufficient.

How Gonioplasty Differs from Iridotomy

Because both procedures involve lasering the iris, people sometimes confuse gonioplasty with iridotomy. They address different anatomical problems. Iridotomy punches a small hole through the full thickness of the iris, creating a bypass channel for fluid that is trapped behind it. This equalizes the pressure on both sides of the iris and allows it to fall back into a flatter position. It targets pupillary block, which is the most common cause of angle closure.

Gonioplasty does not create a hole. It applies surface burns to the outer iris to contract tissue and physically pull the iris away from the angle. It targets angle closure caused by mechanisms other than pupillary block, such as the forward iris insertion seen in plateau iris or the anatomical crowding in very small eyes. In practice, gonioplasty is almost always performed after iridotomy has already been done and the angle remains problematically narrow.

A randomized pilot study comparing iridotomy alone to iridotomy plus iridoplasty for primary angle-closure glaucoma found that adding gonioplasty reduced the extent of peripheral anterior synechiae (scar tissue gluing the iris to the angle wall) by one additional clock-hour compared to iridotomy alone. However, at the one-year mark, there was no significant difference in eye pressure, number of medications needed, need for surgery, or visual function between the two groups.⁷ That finding raises a genuine question about whether adding gonioplasty to iridotomy provides meaningful clinical benefit in typical angle-closure cases, as opposed to the more specific plateau iris scenario where the evidence is stronger.

Researchers have designed larger trials to settle this. One protocol is testing whether adding gonioplasty to iridotomy can reduce the three-year rate of angle-closure progression compared to iridotomy alone, working from the assumption that progression rates might drop from roughly 55% with iridotomy alone to about 35% with the combined approach.⁸ Until data from these larger trials are available, the evidence for routine use of gonioplasty alongside iridotomy remains preliminary.

What the Long-Term Evidence Actually Shows

Short-term results for gonioplasty tend to look encouraging, with rapid angle opening and pressure drops. The longer-term picture is more complicated and varies by condition. In plateau iris specifically, the most detailed long-term study followed 22 eyes over a mean of about four years. Roughly half of the eyes still had an open angle on examination at the last follow-up. But eye pressure had gradually crept back toward baseline levels, and the number of eyes requiring pressure-lowering medications doubled from the starting count. Only two eyes (about 9%) needed no medication or additional surgery at all. Three more eyes were controlled on medications alone. The remaining 77% ultimately required a surgical procedure, at an average of about four years after the initial gonioplasty.⁹

Those numbers deserve honest framing. Gonioplasty in plateau iris does open the angle and buy meaningful time, sometimes years. But for most patients, it is a bridge rather than a definitive cure. The iris tissue that was contracted by the laser can gradually re-thicken, the angle can re-narrow, and the underlying anatomical configuration does not change permanently. Many patients eventually need cataract surgery (which inherently widens the angle by removing the bulky natural lens) or glaucoma filtration surgery to maintain safe pressures long-term.

The three-year data from acute angle-closure cases cited earlier are somewhat more optimistic, with pressure staying in a safe range at three years in a group of medically refractory eyes.¹⁰ But acute attacks and chronic plateau iris represent different patient populations, and the long-term trajectory may differ accordingly.

Risks and Side Effects

Gonioplasty is generally considered a low-risk procedure compared to incisional surgery, but it is not risk-free. The most frequently reported complications are inflammatory flares inside the eye and temporary pupil dilation (mydriasis) after the procedure.¹¹ The inflammation is usually mild and self-limiting, managed with short-term anti-inflammatory eye drops. The pupil dilation typically resolves on its own, though it can cause light sensitivity and blurry vision for a day or two.

Other possible issues include transient spikes in eye pressure immediately after the laser session, which is why pressure is typically checked in the clinic before the patient goes home. Corneal endothelial burns can occur if the laser hits the wrong target, though this is uncommon with careful technique. There is also a theoretical concern about progressive damage to the iris pigment epithelium with repeated treatments, though significant clinical consequences from this appear rare.

Peripheral anterior synechiae, the scar-like adhesions between the iris and the angle wall, are worth monitoring. While gonioplasty can reduce existing synechiae in some cases, any procedure that causes inflammation near the angle carries a small risk of new synechiae forming. This is why follow-up examinations with gonioscopy, where the doctor uses a special lens to directly inspect the drainage angle, remain important after the procedure.

How Doctors Monitor the Angle After Treatment

Beyond traditional gonioscopy, imaging technology has given doctors a way to measure angle changes more precisely. Anterior segment optical coherence tomography (AS-OCT) can capture cross-sectional images of the angle and measure the distance between the iris and the drainage structures in reproducible numerical terms. One study using AS-OCT to track eyes treated with gonioplasty for plateau iris and primary angle closure found statistically significant increases in angle measurements after the procedure: the angle-opening distance at 500 micrometers from the scleral spur increased, the cross-sectional area of the angle space increased, and the scleral spur angle itself widened from roughly 19.5 degrees to about 27 degrees.¹²

For patients, this means the doctor may take OCT scans before and after the procedure to document how much the angle has opened and to track whether it stays open over time. These measurements can also help identify plateau iris in the first place, by revealing the characteristic forward-positioned ciliary processes pushing the iris into the angle even after iridotomy.

Nanophthalmos and Other Uncommon Indications

Most gonioplasty discussions center on acute angle closure and plateau iris, but the procedure also serves a handful of rarer conditions. Nanophthalmos, a condition in which the eye is abnormally small in all dimensions, creates chronic angle-closure risk because everything inside the eye is proportionally crowded. The small eye leaves very little room for fluid to drain, and standard surgical interventions carry unusually high complication rates in these eyes because the altered anatomy makes filtration surgery particularly risky.

An early series looking at treatment approaches for nanophthalmos found that laser gonioplasty was successful in opening the angle in about 92% of treated eyes, a higher rate than achieved with laser iridotomy alone in the same patient group.¹³ Nanophthalmic eyes represent a scenario where the angle crowding is primarily mechanical and structural rather than driven by pupillary block, making gonioplasty a logical fit. The numbers in that series were small, but the finding is consistent with the broader principle that gonioplasty works best when the problem is peripheral iris configuration rather than fluid dynamics behind the pupil.

Iris and ciliary body cysts that push the iris forward can also cause secondary angle closure, and gonioplasty has been used in these cases to flatten the iris around the cyst and reopen the drain. This is an off-label, case-by-case application rather than a well-studied indication, but it follows the same mechanical logic.

Where Gonioplasty Fits in the Bigger Treatment Landscape

Angle-closure management has evolved considerably in recent years, and gonioplasty’s role exists alongside several competing or complementary options. Cataract surgery, or clear lens extraction in patients without significant cataracts, has emerged as a powerful treatment for angle closure because removing the natural lens and replacing it with a thin artificial one dramatically deepens the anterior chamber and opens the angle. In many cases, particularly for older patients with any degree of cataract, lens extraction may offer a more durable angle-opening effect than laser procedures.

Gonioplasty remains valuable precisely in the situations where lens extraction is not yet indicated, where an acute attack needs to be broken quickly, or where the anatomy (as in plateau iris) requires targeted iris reshaping that lens removal alone may not fully address. It is also far less invasive than incisional surgery, can be performed as an outpatient procedure in minutes, and does not carry the infection or hemorrhage risks associated with opening the eye surgically.

The evidence base, while supportive for specific indications, is thinner than ideal. Randomized controlled trials are still relatively few, sample sizes tend to be small, and long-term data beyond five years are scarce. Clinicians largely agree on its utility for acute angle closure refractory to medication and for plateau iris syndrome after failed iridotomy. Beyond those core indications, decisions about gonioplasty tend to be individualized, guided by the specific anatomy of the patient’s eye and the clinical judgment of the treating surgeon.

What the Procedure Feels Like

For patients heading into gonioplasty, the experience is typically straightforward. The eye is numbed with anesthetic drops, and a special contact lens is placed on the cornea to focus the laser and provide a view of the peripheral iris. The procedure involves a series of laser pulses, usually applied in a ring pattern around the outer iris. Each pulse feels like a brief, mild sting or a sensation of warmth. The whole process takes roughly 10 to 20 minutes per eye.

Afterward, the eye may feel irritated and light-sensitive, and vision can be blurry for several hours. Anti-inflammatory drops are prescribed for a few days to a week. A pressure check is done within the first hour or two after the procedure, and follow-up visits are typically scheduled at one day, one week, and then at longer intervals to monitor angle status and pressure. Most patients return to normal activities within a day, though some experience mild discomfort for two to three days. Unlike incisional glaucoma surgery, there are no sutures, no operating room, and no prolonged recovery period, which makes gonioplasty an appealing option when laser treatment is appropriate.