Glaucoma surgery falls into four broad categories: laser procedures, micro-invasive glaucoma surgery (MIGS), conventional filtration surgery, and cyclodestructive procedures. The right option depends largely on how advanced the disease is, whether eye drops or laser treatment have already been tried, and how much pressure reduction your eye needs. Here’s how each type works and when it’s typically used.
Laser Trabeculoplasty
Laser trabeculoplasty is often the first surgical step for open-angle glaucoma, and some doctors now offer it as an alternative to daily eye drops right from the start. The most common version, selective laser trabeculoplasty (SLT), uses short pulses of low-energy light to target the eye’s drainage tissue without burning or scarring it. This triggers a mild inflammatory response that remodels the tissue, allowing fluid to drain more freely and lowering eye pressure.
SLT is performed in a clinic, takes only a few minutes, and can be repeated if the effect fades over time. The World Glaucoma Association considers it appropriate as an initial treatment for mild to moderate glaucoma and for ocular hypertension. It won’t produce the dramatic pressure drops that more invasive surgery can, but for many people it reduces or eliminates the need for daily drops.
Micro-Invasive Glaucoma Surgery (MIGS)
MIGS refers to a growing family of procedures that lower eye pressure through tiny incisions and with less tissue disruption than traditional surgery. These are best suited for mild to moderate glaucoma, particularly for people who can’t tolerate drops or whose pressure isn’t controlled by drops and laser alone. MIGS devices generally aim for a target pressure in the mid-teens or higher, so they’re often not powerful enough for advanced disease that demands very low pressure targets.
The procedures work through several different mechanisms:
- Tiny stents that bypass the drainage tissue. Devices like the iStent, iStent inject, and Hydrus microstent are placed inside the eye’s natural drainage channel (Schlemm’s canal) to let fluid flow past the point of greatest resistance. The Hydrus also acts as a scaffold, keeping the canal open over a longer stretch. These stents are frequently implanted during cataract surgery.
- Tissue removal to open the drain. Procedures like Kahook Dual Blade goniotomy and gonioscopy-assisted transluminal trabeculotomy (GATT) physically strip or cut away the drainage tissue rather than bypassing it with a device.
- Canal dilation. Techniques like ab interno canaloplasty thread a catheter through Schlemm’s canal to stretch it open and reduce resistance in the downstream drainage system.
- Subconjunctival shunting. The XEN gel implant creates a new drainage pathway from inside the eye to the space beneath the outer membrane of the eye, functioning somewhat like a miniaturized version of traditional filtration surgery.
Compared to trabeculectomy, MIGS produces a slightly smaller pressure reduction on average. One comparative study found trabeculectomy lowered pressure by about 9.8 mmHg versus 8.2 mmHg for MIGS. The tradeoff is a substantially lower risk of serious complications and a faster recovery.
Trabeculectomy
Trabeculectomy remains the reference standard for moderate to severe glaucoma. The surgeon creates a small flap in the white of the eye and removes a tiny piece of drainage tissue, allowing fluid to flow out of the eye and collect under the outer membrane in a small reservoir called a bleb. The fluid is then absorbed by surrounding tissue, which lowers eye pressure.
Five-year success rates range from 60% to 80%, and the procedure can achieve lower pressure targets than most MIGS options. That makes it the go-to choice when significant pressure reduction is critical to preserving remaining vision. The main risks include infection, which can remain a concern for years because the anti-inflammatory medications used after surgery suppress the eye’s immune defenses around the bleb. Permanent vision loss from trabeculectomy is possible but not a common lasting side effect.
Glaucoma Drainage Devices
When trabeculectomy isn’t suitable or has already failed, surgeons may implant a drainage device (sometimes called a tube shunt). A small silicone tube is inserted into the front of the eye and connected to a plate sewn onto the eye’s surface, routing fluid to a reservoir where it can be absorbed.
The two most widely studied devices are the Ahmed valve and the Baerveldt implant. The Ahmed valve has a built-in flow restrictor that limits how quickly pressure drops in the early days after surgery, which can reduce short-term complications. The Baerveldt implant has no valve, so it often achieves lower long-term pressures, but the surgeon must temporarily block the tube during healing to prevent the pressure from falling too fast. In head-to-head trials, intraoperative complication rates were similar: around 8% for the Ahmed and 12% for the Baerveldt, a difference that was not statistically significant.
Drainage devices are particularly useful when there is active abnormal blood vessel growth in the eye, a situation where trabeculectomy is generally avoided.
Cyclodestructive Procedures
Rather than improving drainage, cyclodestructive procedures reduce the amount of fluid the eye produces in the first place. They target the ciliary body, the tissue behind the iris responsible for making the fluid that fills the front of the eye.
The most refined version is endoscopic cyclophotocoagulation (ECP), which uses a tiny camera and laser inserted through a small incision. The surgeon can see the ciliary tissue directly and apply just enough laser energy to shrink it, limiting damage to surrounding structures. Treating the full 360 degrees of the ciliary body through two incisions produces lower pressures, greater medication reduction, and fewer treatment failures than partial treatment. In one study of patients with refractory glaucoma who had failed prior surgeries, ECP reduced average pressure from about 28 mmHg to 17 mmHg, a 34% decrease, with a 90% success rate.
Cyclodestructive procedures were traditionally reserved as a last resort, but the precision of ECP has led many surgeons to consider it earlier in treatment. It can also be combined with other MIGS procedures or performed alongside cataract surgery.
Sustained-Release Implants
A newer category blurs the line between medication and surgery. The bimatoprost intracameral implant, approved by the FDA in 2020, is a tiny biodegradable rod injected into the front of the eye during an office visit. It steadily releases a pressure-lowering drug over about 90 days, eliminating the need for daily drops during that period. It’s designed for people with open-angle glaucoma or ocular hypertension. The most common side effect is eye redness, reported in about 27% of patients, with eye pain, light sensitivity, and dry eye occurring in 5% to 10%.
How Surgeons Choose the Right Procedure
The stage of your glaucoma largely determines which surgery makes sense. For mild to moderate open-angle glaucoma, laser trabeculoplasty or MIGS procedures are typically the first surgical options. These carry lower risk and can often be done at the same time as cataract surgery. For angle-closure glaucoma, lens removal alone can sometimes resolve the problem by opening up the blocked drainage angle.
For advanced glaucoma or cases where less invasive options have failed, trabeculectomy and drainage devices offer the strongest pressure reduction. The World Glaucoma Association recommends considering surgery promptly for anyone who already has advanced disease at the time of diagnosis, since the risk of further vision loss outweighs the risks of the procedure.
What Recovery Looks Like
Recovery timelines vary by procedure. Laser and MIGS procedures typically involve minimal downtime, with most people returning to normal activities within days. Traditional filtration surgery and drainage devices require more caution. You’ll generally need to avoid lifting more than 10 pounds, bending over, and vigorous activity while eye pressure is still stabilizing. Swimming and hot tubs should be avoided as well, and depending on the procedure, that water restriction can be permanent because the surgical site remains a potential entry point for bacteria.
Post-operative visits are frequent in the first few weeks, especially after trabeculectomy, since the surgeon may need to adjust the drainage site to fine-tune pressure. Most people use anti-inflammatory eye drops for several weeks after surgery. Vision can fluctuate during healing, and it may take a month or more for your prescription to stabilize. Permanent vision loss from glaucoma surgery is rare, but some temporary blurriness during recovery is normal.