Glaucoma laser surgery is a group of outpatient procedures that use focused beams of light to improve fluid drainage inside the eye, lowering the pressure that damages the optic nerve. The most common type, selective laser trabeculoplasty (SLT), can reduce eye pressure by roughly 15 to 19 percent and keep nearly three quarters of patients free from daily eye drops for at least three years. Which laser procedure you receive depends on the type of glaucoma you have and how advanced it is.
How Eye Pressure Builds Up
Your eye constantly produces a clear fluid that nourishes internal structures and then drains out through a tiny mesh of tissue near the base of the iris. In open-angle glaucoma, this drainage mesh gradually becomes less efficient, so fluid backs up and pressure climbs. In angle-closure glaucoma, the iris physically blocks the drainage pathway. Either way, the rising pressure slowly damages the optic nerve, leading to irreversible vision loss. Laser surgery targets the specific point where drainage is failing.
Laser Trabeculoplasty for Open-Angle Glaucoma
SLT is now the most widely used laser procedure for open-angle glaucoma, the form that accounts for roughly 90 percent of cases. During treatment, short pulses of low-energy laser light are applied to the eye’s drainage tissue. This triggers a mild biological response: the tissue releases signaling molecules that attract immune cells, loosen the mesh structure, and widen the drainage canal behind it. The result is that fluid flows out more freely and pressure drops.
An older version called argon laser trabeculoplasty (ALT) works on the same drainage tissue but uses higher energy that causes small thermal burns. Because ALT permanently scars the tissue, it generally can’t be repeated. SLT leaves the tissue structurally intact, which is why it has largely replaced ALT and can be performed more than once if the effect fades over time.
How Well SLT Works
In clinical studies, SLT lowers eye pressure by an average of 2 to 4 mmHg, which translates to a 12 to 19 percent reduction depending on the time frame measured. A five-year retrospective study found that about 60 percent of treated eyes still maintained adequate pressure control at the five-year mark without needing another procedure. Among those who did need further intervention, roughly half opted for a repeat SLT session rather than moving to traditional surgery.
The landmark LiGHT trial, published in The Lancet, directly compared SLT to daily pressure-lowering eye drops as a first treatment in 718 patients. SLT provided more stable pressure control at lower cost, with 74 percent of laser-treated patients remaining drop-free for at least three years. Based on these results, many ophthalmologists now offer SLT as a first-line option rather than starting with daily medication.
Laser Iridotomy for Angle-Closure Glaucoma
When the iris itself blocks fluid drainage, the treatment is laser peripheral iridotomy (LPI). A laser creates a tiny hole through the iris, allowing fluid to flow directly from behind the iris to the front chamber. This equalizes pressure on both sides of the iris, pulls it away from the drainage angle, and restores outflow. LPI is used to treat acute angle-closure attacks and also as a preventive measure in the fellow eye of someone who has already had an attack, since the anatomical risk is usually present in both eyes.
LPI is also used in conditions where the iris bows backward, pressing against internal structures and releasing pigment that clogs the drainage system. By equalizing pressure across the iris, the procedure can halt pigment release and prevent further damage.
Cyclophotocoagulation for Advanced Cases
When other treatments have failed, cyclophotocoagulation takes a different approach. Instead of improving drainage, it reduces the amount of fluid the eye produces in the first place. The laser targets the tissue behind the iris responsible for fluid production, partially disabling it so less fluid enters the eye and pressure drops. This procedure has traditionally been reserved for eyes that haven’t responded to medications, other laser treatments, or conventional surgery. It is also used for painful end-stage glaucoma, particularly in neovascular glaucoma where abnormal blood vessels block drainage.
A newer version called micropulse cyclophotocoagulation delivers energy in tiny bursts rather than a continuous beam, which allows surrounding tissue to cool between pulses. This reduces the risk of overcorrecting pressure or causing long-term structural damage to the eye.
What the Procedure Feels Like
Most glaucoma laser procedures are done in a clinic or outpatient setting, not an operating room. You sit at a device similar to the one used during a routine eye exam. Numbing drops are placed in your eye, and a special contact lens is held against it to focus the laser beam. Each session typically takes 5 to 15 minutes. You may see brief flashes of light and feel a mild stinging or warmth, but the numbing drops prevent significant pain.
No sedation is needed for standard laser procedures like SLT and LPI. You stay awake and seated the entire time. Because no incision is made, there are no stitches and no surgical wound to heal.
Recovery and What to Expect Afterward
Most people can read, watch screens, and handle light daily activities within the first few days. Your doctor will typically prescribe anti-inflammatory eye drops for a short period after the procedure and may adjust your existing glaucoma medications. You’ll usually have a follow-up visit the next day, then every one to three weeks for the first two to three months while your pressure stabilizes.
Because these are outpatient procedures without heavy sedation, many patients can drive the following day, depending on comfort and vision in both eyes. If your eye pressure runs low in the early recovery period, you may be asked to avoid heavy lifting (over 10 pounds), bending at the waist, and vigorous exercise until your doctor clears you. Gentle walking is generally fine right away.
Risks and Potential Side Effects
The most common concern is a temporary spike in eye pressure shortly after treatment. In a study of over 400 eyes treated with LPI, about 11 percent experienced a pressure rise of 8 mmHg or more, and about 7 percent spiked above 30 mmHg. Patients with acute angle-closure glaucoma were at the highest risk for these spikes. Using pressure-lowering drops before the procedure can reduce the likelihood. These spikes are typically short-lived and managed in the clinic with additional drops.
Mild inflammation and temporary blurred vision are normal in the hours following any glaucoma laser procedure. Less common side effects include light sensitivity, minor bleeding inside the eye, and, rarely, damage to the cornea. With cyclophotocoagulation, there is a small risk of lowering pressure too much, which can cause the eye to soften excessively. This is one reason the procedure is generally reserved for cases where other options have been exhausted.
How Long Results Last
SLT is not a permanent fix. Its effect gradually fades as the drainage tissue returns to its previous state. A five-year study found that about half of treated eyes needed an additional procedure within that window, with an average time to re-intervention of roughly 34 months. Over 10 years, the re-treatment rate climbs to around 60 percent. The advantage of SLT over older laser techniques is that it can be safely repeated, giving patients the option of another round of laser treatment rather than moving directly to incisional surgery.
LPI, by contrast, creates a permanent physical opening in the iris. Once the hole is made, it typically stays open, though in some cases it can close over and need to be redone. For angle-closure glaucoma, a single successful LPI often provides lasting protection against future pressure crises.