Glaucoma surgery is not one single operation. There are several surgical treatment options, and they lower eye pressure in different ways. Some procedures improve the eye's existing drainage system. Others create a completely new route for fluid to leave the eye. Certain laser procedures lower pressure by reducing how much fluid the eye produces. The main glaucoma surgery treatment options include:
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
- Trabeculectomy
- Glaucoma drainage implants or tube shunts
- Minimally invasive glaucoma surgery (MIGS)
- Minimally invasive bleb-forming procedures or microshunts
- Cyclophotocoagulation
- Lens or cataract surgery in selected forms of glaucoma
The right procedure depends on:
- The type of glaucoma
- How advanced the disease is
- The target eye pressure
- Previous glaucoma treatment
- Previous eye surgery
- Whether a cataract is also present
- The condition of the cornea and drainage angle
- The balance between pressure reduction and surgical risk
For a broader overview of glaucoma operations, see our main guide to Glaucoma Surgery.
What Is the Goal of Glaucoma Surgery?
Glaucoma damages the optic nerve, which carries visual information from the eye to the brain. Lowering intraocular pressure (IOP) is currently the main proven way to reduce the risk of further glaucoma damage. Surgery may therefore be used to:
- Lower eye pressure to an individual target
- Slow or prevent further optic nerve damage
- Reduce dependence on glaucoma eye drops
- Control glaucoma that continues to progress despite medication or laser treatment
Glaucoma surgery does not normally restore vision already lost from permanent optic nerve damage. Its purpose is mainly to protect the vision that remains.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
How Are Glaucoma Surgery Options Different?
| Type of Procedure | How It Lowers Eye Pressure |
|---|---|
| Trabeculectomy | Creates a new drainage pathway beneath the eyelid |
| Glaucoma drainage implant | Uses a tube and plate to redirect fluid outside the eye |
| Trabecular MIGS | Improves drainage through or around the trabecular meshwork |
| Canal-based MIGS | Opens or expands Schlemm's canal to improve natural drainage |
| Subconjunctival microshunt | Creates a controlled drainage pathway beneath the conjunctiva |
| Cyclophotocoagulation | Reduces production of fluid inside the eye |
| Lens extraction in selected angle-closure glaucoma | Creates more space in the front of the eye and can improve drainage-angle anatomy |
1. Trabeculectomy
Trabeculectomy is one of the longest-established and most powerful glaucoma operations. The surgeon creates a small opening that allows aqueous fluid to drain from inside the eye into a reservoir beneath the upper eyelid called a bleb. This bypasses the eye's normal drainage pathway and can produce substantial pressure reduction.
When Is Trabeculectomy Used?
It may be considered when:
- Glaucoma is advanced
- Eye pressure remains above target despite medication or laser
- Visual-field damage continues to progress
- A very low target pressure is needed
- Less invasive procedures are unlikely to lower pressure enough
Anti-Scarring Treatment During Trabeculectomy
The body naturally tries to heal any surgical opening. If too much scar tissue forms around a trabeculectomy, the drainage pathway can close. Surgeons may therefore use anti-scarring medicines such as mitomycin C during surgery. Postoperative follow-up is also especially important because sutures, inflammation and scar formation may need active management during the healing period.
2. Glaucoma Drainage Implants or Tube Shunts
A glaucoma drainage implant uses a small tube connected to a plate placed on the outside of the eye beneath surrounding tissues. Fluid flows through the tube toward the plate, where it is absorbed by nearby tissues. Common implant families include:
- Ahmed glaucoma valves
- Baerveldt glaucoma implants
- Other drainage devices depending on the country and surgical setting
When Is Tube-Shunt Surgery Used?
Tube surgery may be particularly useful when:
- A previous trabeculectomy has failed
- The eye has undergone previous operations
- Significant conjunctival scarring is present
- Neovascular glaucoma is present
- Uveitic or other secondary glaucoma is difficult to control
- The surgeon believes a tube has a better chance of remaining effective than another filtering procedure
Trabeculectomy vs Tube Implant
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Both operations can provide substantial pressure reduction. The choice depends heavily on the individual eye.
| Trabeculectomy | Tube Implant |
|---|---|
| Can achieve very low eye pressures | Can provide strong long-term pressure reduction |
| No permanent tube inside the eye | Uses a permanent drainage device |
| Heavily influenced by postoperative scar formation | Often useful in previously operated or scarred eyes |
| Requires intensive early postoperative follow-up | Has device-specific risks such as tube exposure or corneal contact |
3. Minimally Invasive Glaucoma Surgery (MIGS)
Minimally invasive glaucoma surgery refers to a growing group of procedures designed to lower eye pressure with less tissue disruption than traditional filtering surgery. MIGS has greatly expanded the surgical options available for people with glaucoma. Many MIGS procedures are particularly useful for mild-to-moderate open-angle glaucoma.
Potential advantages include:
- Smaller incisions
- Faster recovery
- Lower risk of some serious complications
- Reduced dependence on glaucoma eye drops
- Ability to combine some procedures with cataract surgery
Trabecular Bypass MIGS
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
The trabecular meshwork is one of the main areas of resistance to aqueous-fluid drainage in open-angle glaucoma. Trabecular bypass devices create a small route through this tissue so fluid can reach the eye's natural drainage channels more easily. Examples include:
- iStent devices
- Hydrus Microstent
Goniotomy and Trabeculotomy Procedures
Some MIGS procedures do not leave a permanent implant inside the eye. Instead, they cut or remove a portion of the trabecular meshwork. Examples include:
- Goniotomy
- Kahook Dual Blade procedures
- Gonioscopy-assisted transluminal trabeculotomy (GATT)
- Other ab-interno trabeculotomy techniques
The aim is to allow aqueous fluid to move more easily into the collector channels beyond the trabecular meshwork. Temporary bleeding inside the front of the eye, known as hyphema, is relatively common after procedures that open the trabecular meshwork.
Canaloplasty-Based Procedures
Another group of procedures targets Schlemm's canal, part of the eye's natural drainage system. A microcatheter may be used to widen the canal and improve fluid movement. Depending on the technique, canaloplasty may be performed alone or combined with trabeculotomy. Examples include systems such as OMNI and other canal-based techniques. These operations preserve the eye's natural drainage route rather than creating a traditional external filtering bleb.
Is MIGS Better Than Trabeculectomy?
It depends on what the eye needs. Recent comparative research shows that trabeculectomy generally produces greater average eye-pressure reduction than minimally invasive glaucoma procedures.
MIGS, however, generally offers a more favourable safety profile. A simple way to understand the choice is: Mild-to-moderate glaucoma + modest pressure reduction required → MIGS may be sufficient.
Advanced glaucoma + very low target pressure required → trabeculectomy or another stronger filtering procedure may be more appropriate. The least invasive procedure is not automatically the best procedure if it cannot reach the pressure required to protect the optic nerve.
4. Minimally Invasive Bleb-Forming Surgery and Microshunts
Between traditional trabeculectomy and conventional trabecular MIGS is another group of operations sometimes called minimally invasive bleb-forming surgery. Terminology varies between ophthalmic publications and healthcare systems. Examples include devices such as:
- XEN Gel Stent
- PRESERFLO MicroShunt
How Do Microshunts Compare With Trabeculectomy?
Current evidence suggests that microshunts can provide meaningful pressure reduction with fewer postoperative complications in some comparisons. Trabeculectomy, however, generally remains capable of achieving a greater reduction in eye pressure. This means microshunts may be attractive when the surgeon is trying to balance:
- Strong pressure lowering
- Lower surgical invasiveness
- Postoperative complication risk
- The target pressure required
5. Cyclophotocoagulation
Most glaucoma operations focus on improving fluid drainage. Cyclophotocoagulation works differently. It applies laser energy to part of the ciliary body—the structure responsible for producing aqueous fluid. By reducing fluid production, eye pressure falls.
Techniques include:
- Continuous-wave transscleral cyclophotocoagulation
- Micropulse transscleral cyclophotocoagulation
- Slow-coagulation techniques
- Endoscopic cyclophotocoagulation in selected situations
When Is Cyclophotocoagulation Used?
It has traditionally been used for difficult or refractory glaucoma, particularly when:
- Previous surgery has failed
- Another incisional procedure is unlikely to succeed
- The eye has complex secondary glaucoma
6. Cataract Surgery as Part of Glaucoma Treatment
Cataract surgery is not primarily a glaucoma operation, but it can become an important part of the treatment plan. Removing the natural lens can lower eye pressure modestly in some people. It is particularly relevant when glaucoma and cataract occur together.
Cataract Surgery Plus MIGS
Many trabecular MIGS procedures can be performed during cataract surgery. This may allow the surgeon to:
- Treat the cataract
- Lower eye pressure
- Reduce glaucoma medication use
This approach is commonly considered in selected patients with mild-to-moderate open-angle glaucoma. However, cataract surgery with MIGS may not lower pressure sufficiently in advanced glaucoma.
7. Surgery for Angle-Closure Glaucoma
Angle-closure glaucoma requires a different approach because the drainage angle is physically narrow or blocked. In acute angle closure, pressure can rise rapidly and cause:
- Severe eye pain
- Redness
- Sudden blurred vision
- Halos around lights
- Headache
- Nausea and vomiting
Laser Peripheral Iridotomy
A laser peripheral iridotomy creates a tiny opening in the iris to help equalise pressure and reopen the drainage angle. Although patients sometimes hear this described as “laser surgery,” it is different from incisional glaucoma surgery.
Lens Extraction
In selected patients with angle-closure disease, removing the natural lens can deepen the front of the eye and widen the drainage angle. If significant glaucoma remains after treatment of the angle, additional glaucoma surgery may still be required.
Is Laser Treatment the Same as Glaucoma Surgery?
Not exactly. Patients often encounter the phrase “laser glaucoma surgery,” but laser procedures and incisional operations are usually considered separate treatment categories.
For open-angle glaucoma, selective laser trabeculoplasty (SLT) improves drainage through the natural drainage system and is commonly used before incisional surgery. For angle closure, laser peripheral iridotomy can address blockage of the drainage angle.
Cyclophotocoagulation is another laser-based treatment but acts by reducing aqueous-fluid production. If laser and medication do not achieve the target pressure—or if the glaucoma is sufficiently advanced—incisional surgery may be considered.
Which Surgery Is Used for Advanced Glaucoma?
Advanced glaucoma usually requires a lower target eye pressure because the optic nerve has less remaining reserve. Procedures capable of substantial pressure reduction therefore become particularly important.
Options may include:
- Trabeculectomy
- Glaucoma drainage implants
- Selected subconjunctival microshunts
- Cyclophotocoagulation in appropriate cases
Which Surgery Is Used for Mild-to-Moderate Glaucoma?
When glaucoma is less advanced and the target pressure does not need to be extremely low, MIGS may provide an attractive balance between effectiveness and safety. Options may include:
- Trabecular bypass stents
- Goniotomy
- Trabeculotomy
- GATT
- Canaloplasty-based procedures
What If the First Glaucoma Surgery Fails?
Glaucoma surgery does not always control pressure permanently. If pressure rises again, treatment depends on why the original procedure has become less effective. Options may include:
- Restarting or adding glaucoma eye drops
- Laser treatment
- Revision of an existing bleb or drainage pathway
- Needling of a bleb or microshunt in selected cases
- Glaucoma drainage-device implantation
- Repeat filtering surgery
- Cyclophotocoagulation
How Does a Surgeon Choose Between the Treatment Options?
The decision starts with the target eye pressure. The surgeon then considers:
- Current IOP
- Amount of optic nerve damage
- Rate of visual-field progression
- Open or closed drainage angle
- Previous laser treatment
- Number of glaucoma medications
- Previous cataract or glaucoma surgery
- Risk of scar formation
- Corneal health
- Whether a cataract is present
- Ability to attend intensive postoperative follow-up
Comparing Glaucoma Surgery Treatment Options
| Procedure | Typical Role | Pressure-Lowering Potential | General Trade-Off |
|---|---|---|---|
| Trabeculectomy | Advanced glaucoma or very low target IOP | High | Powerful pressure reduction but more intensive recovery and monitoring |
| Tube shunt | Advanced, secondary or previously operated glaucoma | High | Strong pressure control with device-specific risks |
| Trabecular/canal MIGS | Mild-to-moderate open-angle glaucoma | Usually moderate | Favourable safety profile but may not reach very low pressures |
| Subconjunctival microshunt | Selected open-angle glaucoma requiring stronger reduction | Moderate to high depending on procedure | Attempts to bridge the gap between MIGS and traditional filtering surgery |
| Cyclophotocoagulation | Refractory or selected glaucoma | Variable | Non-incisional pressure reduction by decreasing aqueous production |
| Cataract surgery + MIGS | Cataract with suitable mild-to-moderate glaucoma | Usually moderate | Treats both conditions during one surgical session |
Does Glaucoma Surgery Eliminate Eye Drops?
Sometimes, but this should not be guaranteed. Some patients become medication-free after surgery. Others need fewer drops. Some continue to require medication to reach their individual target pressure. Needing eye drops after surgery does not automatically mean the operation failed. The real goal is adequate protection of the optic nerve.
Does Glaucoma Surgery Cure Glaucoma?
No. Glaucoma remains a lifelong condition after surgery. Even when pressure is well controlled, patients still require:
- Eye-pressure checks
- Optic nerve assessment
- OCT testing when appropriate
- Visual-field monitoring
The Bottom Line
Glaucoma surgery treatment options now range from minimally invasive procedures to powerful traditional filtering operations, and each has a different role. Trabeculectomy remains one of the strongest options when advanced glaucoma requires very low eye pressure.
Glaucoma drainage implants provide another major option, particularly for previously operated, secondary or difficult-to-control glaucoma. MIGS has greatly expanded treatment for mild-to-moderate open-angle glaucoma by improving natural drainage with smaller incisions and generally fewer serious complications.
Subconjunctival microshunts occupy a middle ground between conventional MIGS and traditional filtering surgery, offering meaningful pressure reduction through a controlled external drainage pathway. Cyclophotocoagulation lowers pressure differently by reducing aqueous-fluid production and remains important in difficult or selected glaucoma cases.
Lens extraction and laser peripheral iridotomy also play important roles in the treatment of angle-closure glaucoma. Most importantly: The best glaucoma operation is not necessarily the newest, smallest or most powerful procedure. It is the procedure that can safely reach the eye pressure needed to protect that particular patient's remaining optic nerve and vision.
