Trabeculoplasty is a laser procedure that lowers eye pressure in people with glaucoma. It works by directing short pulses of laser light at the eye’s drainage tissue, called the trabecular meshwork, to help fluid flow out of the eye more efficiently. The procedure takes 10 to 15 minutes, is performed in an outpatient clinic, and has become a well-established first-line treatment for open-angle glaucoma.
How the Laser Lowers Eye Pressure
Your eye constantly produces a clear fluid called aqueous humor, which nourishes the front of the eye and then drains out through the trabecular meshwork, a tiny sponge-like tissue near the base of the iris. In open-angle glaucoma, this drainage tissue becomes less efficient over time, causing fluid to build up and pressure inside the eye to rise. That elevated pressure gradually damages the optic nerve and can lead to permanent vision loss.
Trabeculoplasty targets the meshwork directly. The laser energy triggers a biological response in the tissue: it stimulates cells to increase their “cleaning” activity, clearing debris that clogs the drainage channels. It also alters the surrounding structural material in ways that improve fluid outflow. The net result is lower intraocular pressure (IOP) without cutting into the eye or implanting a device.
SLT vs. ALT: Two Types of Trabeculoplasty
The original form, argon laser trabeculoplasty (ALT), has been used since the late 1970s. It effectively lowers pressure but causes thermal scarring of the drainage tissue. That scarring limits how many times ALT can be repeated, and its effectiveness tends to fade over the years.
Selective laser trabeculoplasty (SLT), introduced in the mid-1990s, uses 80 to 100 times less energy than ALT. Instead of burning the tissue broadly, SLT selectively targets pigmented cells within the meshwork while leaving surrounding cells and the overall tissue architecture intact. Both procedures lower eye pressure by similar amounts, but SLT’s gentler approach means it can potentially be repeated if the effect wears off. SLT has largely replaced ALT in clinical practice and is the version most people receive today.
Who Is a Candidate
Trabeculoplasty is used for several forms of glaucoma where the drainage angle remains physically open. The most common candidates include people with:
- Primary open-angle glaucoma whose pressure stays above target despite eye drops, or who have difficulty using drops consistently
- Pseudoexfoliation glaucoma, where flaky protein deposits clog the drainage system
- Pigmentary glaucoma, where pigment granules from the iris block outflow
- Ocular hypertension, meaning elevated eye pressure without confirmed nerve damage yet
It is not typically used for narrow-angle or closed-angle glaucoma unless the angle has been opened first with a separate procedure called an iridotomy.
SLT as a First-Line Treatment
Trabeculoplasty was long considered a backup option when eye drops failed. That changed with strong clinical trial evidence showing SLT works well as a first treatment. In the landmark LiGHT trial, nearly 70% of eyes treated with SLT first achieved their target pressure without needing any eye drops at all. Based on these results, both the European Glaucoma Society and the American Academy of Ophthalmology now support SLT as a first-line option, and the UK’s National Institute for Health and Care Excellence (NICE) has mandated it as an initial treatment choice.
This shift matters for patients because daily eye drops can be inconvenient, expensive, and cause side effects like redness, stinging, or darkening of the eyelid skin. Starting with laser treatment can delay or eliminate the need for drops entirely.
What the Procedure Feels Like
SLT is done in a standard clinic room, not an operating theater. You sit in front of a machine that looks like the slit-lamp microscope used during a regular eye exam. Before starting, a nurse puts in drops to constrict your pupil and prevent a pressure spike, followed by numbing drops so you won’t feel pain on the surface of the eye.
The doctor then places a small lens directly against the front of your eye to focus the laser. You’ll see bright flashes of light during treatment and may feel a mild sensation, but most people describe it as painless or only mildly uncomfortable. The entire procedure typically takes 10 to 15 minutes. You go home the same day.
How Well It Works
The pressure-lowering effect depends heavily on where your eye pressure starts. People with a baseline IOP above 18 mmHg tend to see the best results. In one large study, these patients experienced an average pressure reduction of about 5.4 mmHg at six months, roughly a 24% drop. Studies of SLT used alongside other treatments have reported reductions of around 29% lasting up to four years.
People whose starting pressure is already relatively low (18 mmHg or below) tend to see little benefit from the procedure. This is one reason your ophthalmologist may recommend it for some patients but not others.
How Long the Effect Lasts
SLT is not a permanent fix. A five-year retrospective study found that the pressure-lowering effect held in about 80% of eyes at three years and roughly 61% at five years. Among eyes that maintained their response without additional intervention, pressure stayed about 3.5 mmHg lower than before treatment at the five-year mark.
When the effect fades, SLT can often be repeated because it doesn’t scar the drainage tissue the way ALT does. Some patients undergo a second round of SLT several years after their first, though the evidence on how well repeat treatments perform is still developing.
Side Effects and Risks
SLT is considered low-risk, but mild side effects are common in the first few days. The most frequent is mild inflammation inside the front of the eye, which occurs in roughly 83% of treated eyes. This sounds alarming but is expected, usually painless, and resolves on its own within about five days. Your doctor will typically prescribe anti-inflammatory drops for a short course to manage it.
A temporary spike in eye pressure occurs in about 4 to 6% of cases, usually detected at the one-hour post-treatment check. This is why you’ll stay in the clinic briefly after the procedure so your pressure can be measured before you leave. The spike is almost always transient.
Other reported effects include mild eye pain or discomfort (about 5% of patients) and redness (about 5%). Serious complications like sustained pressure elevation or vision changes are rare.
What to Expect After Treatment
Most people return to normal activities the same day or the next day. Your vision may be slightly blurry for a few hours from the lens and drops used during the procedure. The full pressure-lowering effect doesn’t happen immediately. It typically takes a few weeks to reach its peak, and your doctor will schedule follow-up visits to measure your pressure and determine whether the treatment achieved the target.
If you were already on glaucoma eye drops before SLT, your doctor will decide whether to continue, reduce, or stop them based on your post-treatment pressure readings. That decision is usually made over the first one to three months as the treatment effect stabilizes.