Glaucoma Surgery: Types, Benefits, Risks and What to Expect

Author: Dr Val Phua
Estimated reading time: 14–16 minutes

What Is Glaucoma Surgery?

Glaucoma surgery lowers the pressure inside the eye to reduce the risk of further optic-nerve damage.

The operation may:

Create a new drainage pathway
Bypass a blocked part of the natural drainage system
Open the existing drainage channel
Insert a tube or microscopic stent
Reduce the amount of aqueous fluid produced
Combine glaucoma treatment with cataract surgery

Glaucoma surgery cannot normally:

Restore optic-nerve fibres already lost
Reverse an established visual-field defect
Cure glaucoma permanently
Guarantee that eye drops will never be required
Remove the need for long-term monitoring

Its purpose is to protect the vision that remains.

The National Eye Institute advises that surgery cannot undo vision loss, but it can help protect vision and prevent further deterioration when medication or laser has not provided adequate control.

Why Does Glaucoma Damage Vision?

Glaucoma progressively damages the optic nerve, which carries visual information from the retina to the brain.

Eye pressure is the main modifiable risk factor.

The appropriate pressure differs between patients. A pressure that is acceptable for an eye with early, stable disease may be too high for an eye with:

Advanced visual-field loss
Damage close to central fixation
Rapid OCT progression
Previous loss in the other eye
Normal-tension glaucoma
A long remaining life expectancy

The ophthalmologist therefore establishes an individual target pressure.

Glaucoma surgery is considered when the pressure cannot be lowered sufficiently—or kept reliably low—using less invasive treatment.

When Is Glaucoma Surgery Needed?

Surgery may be recommended when:

Glaucoma continues progressing despite eye drops
Laser treatment has not achieved the target pressure
The pressure remains dangerously high
The glaucoma is advanced at diagnosis
Visual-field loss is approaching central fixation
Medication causes significant eye or systemic side effects
The patient cannot use drops reliably
Several medications are required but remain insufficient
The drainage angle is permanently scarred or closed
Previous glaucoma treatment has failed
Secondary glaucoma is unlikely to respond adequately to drops alone
A child has congenital or developmental glaucoma

Surgery should not always be viewed as a treatment of last resort.

The five-year Treatment of Advanced Glaucoma Study found that primary trabeculectomy produced lower pressure and better protection against disease progression than beginning with medication in patients who presented with advanced open-angle glaucoma, with a similar overall safety profile.

Does Surgery Mean the Glaucoma Is Very Severe?

Not necessarily.

Some operations are offered for mild or moderate glaucoma to:

Reduce medication dependence
Treat glaucoma during cataract surgery
Avoid long-term preservative exposure
Improve adherence
Intervene before severe damage develops

Other operations, particularly trabeculectomy and glaucoma drainage implants, are more commonly used when:

A low target pressure is required
Disease is advanced
Previous treatments have failed
The glaucoma mechanism is complex

The type of surgery provides more information than the word “surgery” alone.

What Are the Main Types of Glaucoma Surgery?

The principal operations include:

Trabeculectomy
Glaucoma drainage implant surgery
Minimally invasive glaucoma surgery
Subconjunctival microshunt surgery
Cataract or lens extraction for angle closure
Cyclophotocoagulation
Goniotomy or trabeculotomy for childhood glaucoma

These procedures lower pressure through different pathways and are not interchangeable.

Trabeculectomy

Trabeculectomy is a traditional filtering operation used to create a new drainage pathway from inside the eye to the space beneath the upper eyelid.

It remains one of the most effective operations for achieving a low eye pressure.

The National Eye Institute describes trabeculectomy as an operation in which a small opening is created beneath the upper eyelid so that excess aqueous fluid can drain away.

How Does Trabeculectomy Work?

During trabeculectomy, the surgeon creates:

A small opening beneath the conjunctiva—the transparent tissue covering the white of the eye.
A partial-thickness flap in the sclera.
A controlled internal opening through which aqueous fluid can leave the anterior chamber.
Sutures that regulate how much fluid flows beneath the flap.

The fluid collects in a small reservoir beneath the upper eyelid called a filtering bleb.

From the bleb, aqueous fluid is absorbed into surrounding tissues and blood vessels.

The bleb is usually hidden beneath the upper eyelid and is not normally noticeable during ordinary conversation.

What Is a Filtering Bleb?

A filtering bleb is an area where aqueous fluid collects beneath the conjunctiva after filtration surgery.

A healthy bleb allows controlled drainage while maintaining enough pressure to preserve the eye’s structure.

A bleb may appear:

Slightly raised
Pale or translucent
Diffuse
Located beneath the upper eyelid

A bleb is not a tumour or blister filled with pus.

It is the intended external drainage reservoir created by the surgery.

Why Is Mitomycin C Used?

The body naturally attempts to heal surgical wounds by producing scar tissue.

Excessive scarring may seal the new drainage channel and cause the pressure to rise again.

Antiscarring medication may therefore be applied during surgery.

The most commonly used agent is:

Mitomycin C

Another agent used in selected situations is:

5-fluorouracil

These medications reduce fibroblast activity and improve the likelihood that the drainage pathway remains open.

The concentration and duration are selected according to factors including:

Age
Ethnicity
Previous eye surgery
Inflammation
Conjunctival scarring
Type of glaucoma
The pressure target

A stronger antiscarring effect may improve filtration but may also increase the risk of:

A thin bleb
Leakage
Excessively low pressure
Late bleb infection

Who May Benefit from Trabeculectomy?

Trabeculectomy may be considered when:

Open-angle glaucoma is advanced
A low target pressure is required
Visual-field damage is progressing
Eye drops and laser are insufficient
Medication cannot be tolerated
The patient is young with severe disease
Pressure remains high despite several treatments
The conjunctiva remains suitable for filtration surgery

Trabeculectomy may also be used for selected:

Angle-closure glaucoma
Normal-tension glaucoma
Uveitic glaucoma
Juvenile glaucoma
Secondary glaucoma

The suitability depends on the individual eye.

How Low Can Trabeculectomy Lower the Pressure?

Trabeculectomy often achieves lower pressures than angle-based minimally invasive procedures.

It can sometimes produce pressures in the low teens or even below, which may be required for:

Advanced glaucoma
Rapid progression
Central-field involvement
Normal-tension glaucoma progressing at low pressures

The final result is not completely predictable.

The eye must maintain a balance between:

Sufficient drainage to protect the optic nerve
Sufficient pressure to maintain normal eye anatomy and vision

How Effective Is Trabeculectomy?

Success depends on:

Definition of success
Target pressure
Previous surgery
Glaucoma type
Scarring response
Follow-up duration
Need for additional medication

The National Eye Institute states that trabeculectomy lowers pressure successfully in approximately seven out of ten people, although outcomes vary according to the eye and the definition used.

The five-year TAGS trial found that trabeculectomy provided better pressure reduction and protection against progression than primary medication in patients presenting with advanced glaucoma.

What Happens After Trabeculectomy?

Postoperative care is a major part of the treatment.

The eye may require:

Frequent steroid drops
Antibiotic drops for a limited period
Pressure checks
Adjustment of glaucoma medication
Removal or release of flap sutures
Laser suture lysis
Bleb massage
Antiscarring injections
Needling of scar tissue
Additional sutures if pressure is too low

The final drainage level is actively adjusted during healing.

The operation should therefore not be thought of as completed the moment the patient leaves the operating theatre.

What Is Laser Suture Lysis?

Sutures in the scleral flap regulate aqueous drainage.

If pressure remains too high because the flap is too tightly closed, the surgeon may use a laser to cut one or more sutures through the conjunctiva.

This allows more fluid to pass beneath the flap.

Laser suture lysis is commonly performed in the clinic after numbing drops have been applied.

What Is Bleb Massage?

The surgeon may gently press the eye to encourage fluid to pass through the new drainage pathway.

Selected patients may be taught a specific massage technique.

Bleb massage should only be performed when instructed.

Excessive or incorrect pressure may cause:

Excessive drainage
Low pressure
Bleeding
Injury to the eye

What Is Bleb Needling?

Scar tissue may form around a trabeculectomy or microshunt bleb and restrict drainage.

Bleb needling uses a fine needle to release scar tissue and restore aqueous flow.

An antiscarring medication may be injected at the same time.

Needling may be performed:

Soon after surgery
Months later
Years later

Moorfields Eye Hospital notes that needling may be required when scar tissue reduces drainage after trabeculectomy, microshunt or selected tube procedures.

What Are the Main Risks of Trabeculectomy?

Possible complications include:

Temporary blurred vision
Eye redness
Grittiness
Inflammation
Pressure that remains too high
Pressure that becomes too low
Shallow anterior chamber
Choroidal detachment
Bleeding
Bleb leakage
Cataract progression
Astigmatism or prescription change
Corneal problems
Infection
Need for further surgery
Permanent visual loss in rare cases

The National Eye Institute lists cataract, corneal problems, excessively low pressure and visual loss among recognised glaucoma-surgery risks.

What Is Hypotony?

Hypotony means that the eye pressure is too low.

This may occur when:

Too much fluid drains
The surgical wound leaks
The ciliary body temporarily produces less fluid
Inflammation is present
The scleral flap is too loose

Mild early hypotony may resolve without permanent harm.

More significant hypotony can cause:

Blurred or distorted vision
A shallow anterior chamber
Choroidal detachment
Retinal or macular folds
Hypotony maculopathy
Cataract-related problems
Permanent visual reduction

Treatment may include:

Adjusting medication
Pressure patching
Additional sutures
Injection of viscoelastic material
Repair of a wound leak
Surgical revision

Can the Pressure Remain Too High After Surgery?

Yes.

Possible causes include:

Early inflammation
Blood or debris blocking the opening
Tight flap sutures
Steroid response
Rapid scar formation
Encapsulation of the bleb
Long-term closure of the drainage pathway

Management may include:

Medication
Bleb massage
Laser suture lysis
Antiscarring injection
Needling
Surgical revision
Another glaucoma operation

Scarring is one of the principal reasons filtering surgery loses effectiveness.

What Is a Bleb Leak?

A bleb leak occurs when aqueous fluid escapes through a defect in the conjunctival surface.

A leak may occur:

Soon after surgery
Months or years later
After trauma
When a bleb becomes very thin

Possible symptoms include:

Excessive watering
Irritation
Blurred vision
Low pressure
A foreign-body sensation

A leaking bleb increases the risk of infection and requires assessment.

Can a Bleb Become Infected?

Yes.

Bleb infection can occur months or years after filtration surgery.

The infection may remain limited to the bleb, called blebitis, or spread into the eye, causing bleb-related endophthalmitis.

Endophthalmitis can cause rapid and severe visual loss.

Warning symptoms include:

Increasing redness
Eye pain
Light sensitivity
Discharge
Sudden blurred or reduced vision
A white or yellow appearance within the bleb
Eyelid swelling

These symptoms require immediate, preferably same-day, ophthalmic assessment.

Moorfields Eye Hospital emphasises that a bleb-related infection can spread into the eye and cause blindness unless treated promptly.

Is the Infection Risk Lifelong?

Yes.

A functioning filtering bleb remains present after the eye has healed.

Patients should remember that a painful red eye in an eye with a trabeculectomy bleb is never something to observe for several days without assessment.

Ordinary conjunctivitis can potentially spread into a vulnerable bleb.

Patients should tell any new eye-care provider that they have had filtering glaucoma surgery.

Can Contact Lenses Be Worn After Trabeculectomy?

Contact-lens wear over or near a bleb may cause:

Friction
Bleb breakdown
Leakage
Infection
Discomfort

Conventional contact-lens wear is therefore often avoided or approached cautiously after bleb-forming surgery.

Specialist fitting may occasionally be considered when the visual need is substantial and the bleb position permits it.

The glaucoma and contact-lens teams should assess the risk together.

Glaucoma Drainage Implant Surgery

A glaucoma drainage implant creates a new pathway through a small tube attached to a plate positioned on the white of the eye.

These devices are also called:

Tube shunts
Aqueous shunts
Glaucoma drainage devices
Glaucoma valves

The tube carries aqueous fluid from inside the eye to a reservoir around the plate.

The fluid is then absorbed by surrounding tissues.

The National Eye Institute notes that tube implants are used for several glaucoma types, including congenital, neovascular, traumatic and other complex glaucomas.

What Are the Main Types of Tube Implant?

Common devices include:

Ahmed glaucoma valve
Baerveldt glaucoma implant
Other non-valved or valved drainage implants

Valved Implant

A valved device is designed to restrict flow when pressure becomes low.

The Ahmed valve is a common example.

Non-Valved Implant

A non-valved implant does not contain a mechanical valve.

The tube may initially be tied closed with a dissolvable ligature to allow scar tissue to form around the plate before full flow begins.

The Baerveldt implant is a common example.

How Does Tube Surgery Differ from Trabeculectomy?

Both operations create an alternative drainage route.

Trabeculectomy

Uses a scleral flap
Creates a filtering bleb directly over the surgical opening
Has no permanent tube or plate
Often achieves very low pressures
Requires intensive bleb management

Drainage Implant

Uses a permanent tube and plate
Directs fluid to a reservoir farther back under the eyelid
May be preferred in scarred or complex eyes
May have a delayed full effect with non-valved devices
Carries device-specific risks

Neither operation is universally superior.

Who May Benefit from a Drainage Implant?

Tube surgery may be considered for:

Previous failed trabeculectomy
Previous conjunctival surgery
Neovascular glaucoma
Uveitic glaucoma
Traumatic glaucoma
Congenital or childhood glaucoma
Aphakic glaucoma
Glaucoma after corneal transplantation
Eyes with extensive conjunctival scarring
Selected primary open-angle glaucoma
Complex secondary glaucoma

Tube implants are increasingly also used as primary incisional surgery in selected eyes without previous surgery.

What Is the Hypertensive Phase?

Some eyes—particularly after a valved implant—develop a period of increased pressure several weeks after surgery.

This may occur as the capsule around the drainage plate thickens during healing.

The hypertensive phase may require:

Temporary glaucoma medication
Continued observation
Adjustment of steroid treatment
Needling or revision in selected cases

The pressure may later improve as the capsule remodels.

Why Does a Non-Valved Tube Take Time to Work?

A non-valved tube may be tied closed temporarily so that a protective capsule develops around the plate before aqueous begins flowing freely.

During this period:

Pressure may remain high.
Glaucoma drops may still be needed.
A small temporary opening or internal stent may allow limited early drainage.

When the ligature dissolves, pressure may fall relatively suddenly.

Close monitoring is required because the eye can become too soft when the tube opens.

What Are the Risks of Tube Surgery?

Possible complications include:

Temporary blurred vision
Inflammation
Bleeding
Pressure that remains too high
Excessively low pressure
Shallow anterior chamber
Choroidal detachment
Tube blockage
Tube displacement
Tube exposure through the conjunctiva
Corneal endothelial-cell loss
Corneal decompensation
Double vision
Cataract
Infection
Need for revision or further surgery

A tube that becomes exposed can allow microorganisms to enter the eye and requires urgent repair.

Can the Tube Damage the Cornea?

Yes.

A tube placed in the anterior chamber may come close to the corneal endothelium—the cells maintaining corneal clarity.

Long-term endothelial-cell loss may contribute to:

Corneal swelling
Reduced vision
Need for corneal transplantation

Risk may be greater when:

The tube sits close to the cornea
The anterior chamber is shallow
A corneal graft is present
The endothelium is already weak
The tube moves with eye rubbing or blinking

Alternative tube positions may be considered in selected eyes.

Can a Tube Cause Double Vision?

Yes, although this is uncommon.

The plate and surrounding scar tissue may affect the movement of an eye muscle.

Double vision may be:

Temporary
Position-dependent
Persistent

Management may include:

Observation
Prism glasses
Strabismus treatment
Implant revision in selected cases

Trabeculectomy Versus Tube Implant

The optimal choice depends on:

Previous eye surgery
Conjunctival scarring
Target pressure
Corneal health
Glaucoma type
Age
Risk of hypotony
Surgeon experience
Ability to attend postoperative follow-up

The five-year Primary Tube Versus Trabeculectomy Study found similar overall failure rates between primary tube implantation and trabeculectomy in eyes without previous incisional surgery. Trabeculectomy required fewer glaucoma medications but had more early postoperative complications.

The earlier Tube Versus Trabeculectomy Study, which involved eyes with previous cataract or glaucoma surgery, found a higher five-year success rate with tube implantation, although both operations achieved pressure in the low teens.

These studies do not establish one operation as best for every patient. They demonstrate that the eye’s previous surgical history matters.

Minimally Invasive Glaucoma Surgery

Minimally invasive glaucoma surgery, or MIGS, refers to a group of procedures designed to lower pressure with less tissue disruption and a faster recovery than traditional filtering surgery.

MIGS generally has:

A favourable safety profile
Small internal incisions
Limited manipulation of the conjunctiva
Faster visual recovery
Moderate pressure-lowering ability

The 2026 American Academy of Ophthalmology guideline notes that MIGS usually provides less pressure reduction than trabeculectomy or aqueous-shunt surgery but has a more favourable safety profile.

Is MIGS One Operation?

No.

MIGS is a broad category.

Procedures may:

Bypass the trabecular meshwork
Remove or open trabecular tissue
Dilate Schlemm’s canal
Insert a trabecular microstent
Access the suprachoroidal pathway
Drain beneath the conjunctiva

Different procedures have different:

Mechanisms
Pressure-lowering effects
Safety profiles
Regulatory approvals
Evidence bases

The name of the specific operation matters.

Trabecular Microstents

Trabecular stents create a small bypass through the trabecular meshwork into Schlemm’s canal.

Examples include:

iStent devices
Hydrus Microstent

These are commonly implanted during cataract surgery in patients with open-angle glaucoma.

They may:

Reduce eye pressure modestly
Reduce the number of glaucoma drops
Improve access to the natural drainage system
Preserve the conjunctiva for future surgery

Goniotomy and Trabeculotomy Procedures

These procedures open or remove part of the trabecular meshwork.

Examples include:

Goniotomy
Kahook Dual Blade goniotomy
Gonioscopy-assisted transluminal trabeculotomy
Ab interno trabeculotomy

They aim to improve access from the anterior chamber to Schlemm’s canal.

Possible temporary effects include:

Blood reflux into the anterior chamber
Blurred vision
Pressure fluctuation
Inflammation

Canaloplasty

Canaloplasty procedures dilate or tension Schlemm’s canal to improve drainage through the natural outflow pathway.

They may involve:

A microcatheter
Viscoelastic injection
Internal suture placement
An ab interno or external approach

The expected effect varies according to the procedure.

Who Is a Good Candidate for Angle-Based MIGS?

MIGS is commonly considered for patients with:

Mild or moderate open-angle glaucoma
A cataract requiring surgery
Pressure controlled with several medications
Medication intolerance
Difficulty using drops
A target pressure in the mid or upper teens
Relatively preserved visual fields

It may also be considered as a standalone treatment in selected circumstances, depending on the device and local approval.

Who May Not Be Suitable for Angle-Based MIGS?

Angle-based MIGS may be insufficient when:

Glaucoma is advanced
A very low target pressure is required
Pressure is extremely high
The drainage angle is closed
Extensive angle scarring is present
Neovascular tissue obstructs the angle
Previous angle surgery has failed
Rapid progression requires more powerful pressure reduction

Trabecular MIGS relies on the downstream natural drainage system.

It cannot generally lower pressure below the level permitted by episcleral venous pressure and the remaining drainage channels.

How Effective Is MIGS?

The effect differs between devices.

In general, angle-based procedures:

Produce a modest additional pressure reduction
Reduce medication burden
Have a lower risk of severe hypotony than filtering surgery
Are often combined with cataract surgery

An American Academy of Ophthalmology report concluded that trabecular procedures combined with cataract surgery provide a mild additional pressure reduction over cataract surgery alone in hypertensive open-angle glaucoma.

The five-year HORIZON trial found that cataract surgery combined with a Schlemm’s canal microstent provided more durable pressure and medication control than cataract surgery alone in patients with mild-to-moderate open-angle glaucoma and cataract.

Does MIGS Replace Trabeculectomy?

No.

MIGS fills a treatment gap between:

Eye drops or laser
Traditional filtering surgery

MIGS is attractive when the goal is:

Modest pressure reduction
Fewer medications
Faster recovery
Lower surgical risk

Trabeculectomy or tube surgery remains more appropriate when:

The target pressure is very low
Glaucoma is advanced
The visual field is deteriorating rapidly
Previous lower-risk treatment has failed

Can MIGS Be Combined with Cataract Surgery?

Yes.

This is one of its most common uses.

The surgeon may:

Remove the cataract.
Implant an intraocular lens.
Perform the glaucoma procedure through the same or an additional small incision.

Combining surgery may:

Restore cataract-related vision
Lower pressure
Reduce medication use
Avoid a second operation

However, the cataract and glaucoma parts have separate goals.

The patient should understand whether the glaucoma procedure is expected to:

Reduce drops
Lower pressure modestly
Prevent future escalation
Reach a specific target

Will Cataract Surgery Alone Lower Eye Pressure?

Cataract surgery often lowers pressure modestly, particularly when the starting pressure is elevated or the drainage angle is crowded.

The effect is not predictable enough to replace glaucoma surgery when:

Very low pressure is required
Glaucoma is advanced
Progression is rapid
Several medications are already insufficient

The additional benefit of MIGS should be assessed against cataract surgery alone.

Subconjunctival Microshunts

Subconjunctival microshunts create a pathway from the anterior chamber to a bleb beneath the conjunctiva.

Examples include:

XEN Gel Stent
PreserFlo MicroShunt

They are less invasive than conventional trabeculectomy in some respects but still create a filtering bleb.

They should therefore not be grouped uncritically with angle-based MIGS.

How Does a Microshunt Work?

A small tube is positioned so that:

One end sits within the anterior chamber.
The device passes through the eye wall.
Aqueous fluid drains beneath the conjunctiva.
A filtering bleb develops.

Antiscarring medication is usually required.

The operation may involve:

An internal approach
An external conjunctival approach
Postoperative bleb needling
Antiscarring injections

Who May Benefit from a Subconjunctival Microshunt?

A microshunt may be considered when:

Greater pressure reduction is required than angle MIGS can provide
The surgeon wishes to avoid a traditional scleral flap
Open-angle glaucoma is inadequately controlled
Medication reduction is important
The conjunctiva is suitable

The exact role depends on:

Device
Regulatory availability
Target pressure
Glaucoma severity
Surgeon experience

Are Microshunts as Effective as Trabeculectomy?

Not necessarily.

A five-year randomised comparison found that both PreserFlo MicroShunt implantation and trabeculectomy reduced pressure and medication use, but the probability of surgical success was lower with the microshunt. Microshunt surgery generally produced fewer or less severe early complications but did not achieve the same degree of pressure control as trabeculectomy in all patients.

Microshunts may be appropriate when the target is around the mid-teens, while trabeculectomy may remain preferable when very low pressure is required.

Can a Microshunt Bleb Scar?

Yes.

Like a trabeculectomy, a subconjunctival shunt depends on controlled wound healing.

Scarring may cause:

Rising pressure
Reduced drainage
Bleb encapsulation
Need for antiscarring injections
Needling
Revision
Further surgery

Long-term follow-up remains necessary.

Cataract or Lens Surgery for Angle-Closure Glaucoma

The natural lens becomes thicker and moves forward with age.

In anatomically crowded eyes, the lens may push the iris towards the trabecular meshwork and narrow the drainage angle.

Removing the lens can:

Deepen the anterior chamber
Widen the angle
Reduce pupillary-block crowding
Lower pressure
Treat cataract
Reduce the risk of future angle closure

The 2026 AAO angle-closure guideline recommends considering lens extraction or incisional glaucoma surgery when the angle remains closed and pressure is not controlled adequately after laser or medication.

Does Lens Surgery Cure Angle-Closure Glaucoma?

No.

Lens removal improves the anatomy but does not reverse:

Existing optic-nerve damage
Permanent angle adhesions
Trabecular-meshwork damage
Visual-field loss

Some patients continue to require:

Glaucoma drops
Goniosynechialysis
MIGS
Trabeculectomy
Tube surgery
Continued OCT and visual-field monitoring

What Is Goniosynechialysis?

Peripheral anterior synechiae are permanent adhesions between the iris and the drainage angle.

During goniosynechialysis, the surgeon mechanically separates selected adhesions to expose the trabecular meshwork.

It is often combined with:

Cataract surgery
Angle surgery
Other glaucoma procedures

The likelihood of success depends partly on how long the angle has been closed and how healthy the trabecular meshwork remains.

Cyclophotocoagulation

Cyclophotocoagulation treats the ciliary body to reduce aqueous-fluid production.

Forms include:

Continuous-wave transscleral cyclophotocoagulation
Slow-coagulation treatment
Micropulse transscleral treatment
Endoscopic cyclophotocoagulation

It may be considered for:

Refractory glaucoma
Painful high-pressure eyes
Eyes with previous failed surgery
Neovascular glaucoma
Eyes unsuitable for conventional filtration
Selected eyes with useful vision

Cyclophotocoagulation is discussed separately from drainage surgery because it reduces fluid production rather than creating a new outflow pathway.

Childhood Glaucoma Surgery

Medication usually provides only temporary support in primary congenital glaucoma.

Surgery is the main treatment.

Common childhood procedures include:

Goniotomy
Trabeculotomy
Circumferential trabeculotomy
Glaucoma drainage implants
Trabeculectomy in selected cases
Cyclophotocoagulation for refractory disease

Angle surgery is generally the preferred initial treatment for primary congenital glaucoma when the anatomy permits it.

Children require long-term monitoring because:

The eye continues growing.
Pressure may become difficult to measure.
Amblyopia may develop.
Corneal enlargement and scarring affect vision.
Additional surgery may be required.

How Is the Type of Surgery Chosen?

The decision depends on:

Glaucoma type
Open or closed drainage angle
Target pressure
Disease severity
Rate of progression
Previous eye surgery
Conjunctival scarring
Cataract status
Corneal health
Age
General health
Medication tolerance
Ability to attend frequent follow-up
Patient preference

Mild or Moderate Open-Angle Glaucoma with Cataract

Possible options include:

Cataract surgery alone
Cataract surgery with trabecular stent
Cataract surgery with goniotomy
Cataract surgery with canaloplasty
Cataract surgery with another MIGS procedure

Advanced Open-Angle Glaucoma

Possible options include:

Trabeculectomy
Glaucoma drainage implant
Subconjunctival microshunt in selected cases
Cyclophotocoagulation in selected eyes

Previous Failed Trabeculectomy or Scarred Conjunctiva

A glaucoma drainage implant may be favoured.

Neovascular or Complex Secondary Glaucoma

Possible treatments include:

Drainage implant
Cyclophotocoagulation
Trabeculectomy in selected circumstances
Treatment of the underlying retinal ischaemia or inflammation

Narrow-Angle or Angle-Closure Glaucoma

Possible treatments include:

Laser iridotomy
Cataract or lens extraction
Goniosynechialysis
Trabeculectomy
Tube implant
Combined procedures

What Happens Before Glaucoma Surgery?

The preoperative assessment may include:

Visual acuity
Eye-pressure measurement
Gonioscopy
Corneal examination
Optic-nerve evaluation
OCT
Visual-field review
Cataract assessment
Conjunctival examination
Review of previous surgery
General medical history
Medication review
Anaesthetic assessment

Patients should disclose:

Blood-thinning medication
Asthma
Cardiac disease
Diabetes
Kidney disease
Steroid use
Previous eye infection
Previous LASIK, PRK or SMILE
Allergy to medication
Difficulty lying flat
Pregnancy or breastfeeding

Should Blood Thinners Be Stopped?

Not automatically.

The risks of stopping anticoagulant or antiplatelet medication may be greater than the surgical bleeding risk.

The ophthalmologist and prescribing physician should consider:

Reason for the blood thinner
Previous stroke or heart attack
Cardiac stents
Atrial fibrillation
Type of surgery
Anaesthesia
Individual bleeding risk

Patients should never stop these medications independently.

What Type of Anaesthesia Is Used?

Many adult glaucoma operations are performed using:

Local anaesthesia around or within the eye
Intravenous sedation
Topical anaesthesia for selected MIGS procedures

General anaesthesia may be used for:

Children
Patients unable to remain still
Severe anxiety
Certain complex operations
Particular medical or communication needs

The patient is usually awake but should not feel sharp pain.

How Long Does the Operation Take?

The duration depends on the procedure.

Approximate operating times vary widely:

A simple MIGS procedure may add only a short time to cataract surgery.
Trabeculectomy often takes less than an hour.
Tube implantation may take one to two hours.
Combined or complex surgery may take longer.

The patient may spend substantially more time in the facility for preparation, anaesthesia and postoperative observation.

Will Both Eyes Be Operated on Together?

Filtering glaucoma surgery is generally performed on one eye at a time.

This allows:

Recovery of the first eye
Adjustment of treatment
Assessment of the surgical response
Preservation of vision in the untreated eye during healing

The National Eye Institute advises that when both eyes require glaucoma surgery, they are normally operated on separately.

What Should I Expect Immediately After Surgery?

The eye may be:

Patched or protected by a clear shield
Red
Watery
Gritty
Mildly sore
Light-sensitive
Blurred

Temporary blurred vision may result from:

Inflammation
Corneal swelling
Changes in pressure
Pupil-dilating medication
Astigmatism from sutures
Blood in the anterior chamber
Ointment
A change in spectacle prescription

Vision may fluctuate during the first several weeks.

Will Surgery Improve My Vision?

Glaucoma surgery is performed primarily to preserve vision, not improve it.

Vision may improve when surgery is combined with cataract removal.

Vision may remain unchanged when:

The optic nerve is damaged
No significant cataract was present
The operation is purely pressure-lowering

Temporary reduction in vision during recovery does not automatically indicate permanent damage.

Sudden or progressive visual loss still requires urgent assessment.

What Eye Drops Are Used After Surgery?

Postoperative medication may include:

Steroid drops
Antibiotic drops
Pupil-dilating or relaxing drops
Lubricants
Pressure-lowering medication when required

Steroid treatment is particularly important after filtering surgery because inflammation encourages scarring.

The dose may be frequent initially and gradually reduced over weeks or months.

Patients should not:

Stop steroids suddenly
Substitute another bottle
Restart old glaucoma drops in the operated eye unless instructed
Continue antibiotics beyond the prescribed period without advice

The National Eye Institute notes that postoperative anti-inflammatory and infection-preventing drops are used for several weeks after glaucoma surgery.

Should Previous Glaucoma Drops Be Continued?

This depends on the operation and the eye pressure.

After trabeculectomy or tube surgery, the old glaucoma drops in the operated eye are often stopped initially.

Drops should usually continue in the unoperated eye.

After MIGS, some or all medications may remain necessary until the response is measured.

Follow the written instructions rather than assuming that all previous medication should continue or stop.

How Frequent Are Follow-Up Visits?

Follow-up is usually more intensive after trabeculectomy or tube surgery than after ordinary cataract surgery.

Visits may occur:

The first day
Within the first week
Weekly or more frequently during early healing
At increasing intervals once the pressure stabilises

Additional visits may be needed for:

Suture adjustment
Bleb massage
Antiscarring injections
Needling
Pressure spikes
Hypotony
Inflammation
Tube opening

Frequent follow-up is part of achieving a successful result.

How Long Is Recovery?

Recovery depends on:

Operation type
Preoperative vision
Pressure stability
Inflammation
Need for postoperative adjustments
Work and lifestyle

Approximate expectations are:

MIGS

Often relatively rapid visual recovery
Frequently performed with cataract surgery
Activity restrictions may resemble cataract-surgery precautions

Trabeculectomy or Tube Surgery

Blurred vision may continue for several weeks
The eye may take one to three months to feel fully settled
Pressure may fluctuate during healing
The spectacle prescription may change

The National Eye Institute advises avoiding heavy lifting and selected activities for approximately two to four weeks after glaucoma surgery, with the exact restriction determined by the surgeon.

When Can I Return to Work?

This depends on:

Type of surgery
Vision in the other eye
Job demands
Need to drive
Exposure to dust or water
Heavy lifting
Frequency of follow-up

Office-based work may resume earlier than:

Construction
Heavy manual work
Contact sport
Swimming instruction
Work in dusty or contaminated environments

Patients undergoing trabeculectomy or tube surgery should plan for repeated early appointments.

When Can I Drive?

Do not drive until:

Vision is adequate
The operated eye is comfortable
The other eye provides sufficient vision
The surgeon confirms that driving is appropriate
Legal visual requirements are met

Advanced glaucoma may affect driving through visual-field loss even when visual acuity is clear.

A binocular driving-field test may be required in selected cases.

What Activities Should Be Avoided?

Follow the individual surgical instructions.

Common temporary restrictions include:

Rubbing or pressing the eye
Heavy lifting
Straining
Bending with the head far below the waist
Contact sports
Swimming
Hot tubs
Dusty environments
Eye makeup
Getting soap or contaminated water into the eye

Reading, watching television and ordinary walking are generally permitted according to comfort.

Why Must the Eye Be Protected at Night?

A clear shield may be worn while sleeping to prevent:

Accidental rubbing
Pressure from the pillow
A finger entering the eye
Trauma during sleep

The duration depends on the procedure and the surgeon’s instructions.

Warning Signs After Glaucoma Surgery

Seek urgent eye care for:

Severe or increasing eye pain
Sudden reduced vision
Marked redness
Thick discharge
Increasing light sensitivity
Nausea or vomiting with eye pain
A new curtain or shadow
Trauma to the operated eye
Fluid leaking from the eye
A visible exposed tube
Pain or redness around a filtering bleb
Symptoms that worsen rather than improve

A painful red eye after trabeculectomy remains an emergency even many years after surgery because of the lifetime risk of bleb infection.

Can Glaucoma Surgery Fail?

Yes.

Failure may occur because:

Scar tissue closes the drainage pathway
The implant becomes encapsulated
The tube becomes blocked
The tube or stent moves
The operation does not lower pressure enough
The effect reduces over time
The glaucoma continues progressing at the achieved pressure

Failure does not necessarily mean the operation was performed incorrectly.

Wound healing differs substantially between patients.

What Happens If Surgery Fails?

Possible next steps include:

Restarting or adding eye drops
Laser treatment
Bleb needling
Antiscarring injections
Surgical revision
A second trabeculectomy
Tube implantation
A second tube
Cyclophotocoagulation
Another MIGS procedure in selected eyes

The next operation depends on:

Why the first operation failed
Conjunctival condition
Corneal health
Target pressure
Remaining vision
Glaucoma type

Will Eye Drops Still Be Needed?

Possibly.

The likelihood depends on the procedure.

Trabeculectomy

Many patients can stop or reduce medication, but drops may be restarted if pressure rises.

Tube Implant

Medication may still be needed, particularly during the early postoperative period or if the final pressure remains above target.

MIGS

Reducing the number of medications is often a primary goal, but complete medication independence is not guaranteed.

Microshunt

Some patients remain medication-free while others require additional drops.

Surgery can still be successful when medication remains necessary, provided the pressure and progression are better controlled.

Can Surgery Be Repeated?

Yes.

Repeated surgery may be necessary when:

The original pathway scars
Pressure later increases
Glaucoma progresses
The first procedure was intentionally conservative
A different drainage mechanism is needed

Each additional operation may become more complex because of:

Conjunctival scarring
Altered anatomy
Corneal vulnerability
Previous implants
Reduced tissue flexibility

This is one reason the sequence of glaucoma procedures is planned carefully.

Does Surgery Stop Glaucoma Permanently?

No.

Surgery lowers pressure.

The patient still has glaucoma and requires:

Pressure measurement
OCT
Visual-field testing
Optic-nerve examination
Monitoring of the bleb or implant
Review of medication
Assessment of the cornea and cataract

A stable pressure does not prove that the optic nerve is stable.

Progression may require a lower target.

Can Lost Vision Be Restored?

Established glaucomatous optic-nerve damage is generally irreversible.

Surgery may improve vision when blur was partly caused by:

Cataract
Corneal swelling from very high pressure
Medication-related ocular-surface disease
Acute pressure elevation

This improvement does not mean that lost optic-nerve fibres have regenerated.

Can Glaucoma Suddenly Worsen After Surgery?

Pressure and vision may fluctuate during recovery.

Urgent problems include:

Acute pressure elevation
Hypotony
Bleeding
Infection
Choroidal detachment
Tube blockage
Wound leakage
Severe inflammation

Prompt follow-up allows many complications to be corrected before permanent harm occurs.

Can Glaucoma Surgery Cause Cataract?

Trabeculectomy and other intraocular operations may accelerate cataract formation in a natural-lens eye.

This risk may be greater when there is:

Postoperative inflammation
Shallow anterior chamber
Very low pressure
Older age
Pre-existing lens opacity

Cataract surgery can usually be performed later, but operating after trabeculectomy may affect the bleb through inflammation and scarring.

The cataract and glaucoma plans should therefore be considered together.

Should Cataract and Trabeculectomy Be Performed Together?

Combined cataract and filtering surgery may be considered when:

Cataract significantly impairs vision
Glaucoma requires surgical pressure reduction
Two separate operations are undesirable

Advantages include:

One anaesthetic episode
Cataract treatment
Pressure lowering

Possible limitations include:

Greater postoperative inflammation
More scarring
Less pressure lowering than trabeculectomy alone in some eyes
More complex refractive planning

In selected advanced glaucoma, separate trabeculectomy followed by later cataract surgery may achieve a lower pressure.

Does Glaucoma Surgery Affect the Spectacle Prescription?

It can.

Trabeculectomy and tube surgery may temporarily or permanently alter:

Corneal curvature
Astigmatism
Anterior-chamber depth
Lens position
Tear-film quality

A new spectacle prescription should usually wait until the eye and pressure have stabilised unless temporary correction is needed.

Can Glaucoma Surgery Be Performed After LASIK or PRK?

Yes.

Previous corneal refractive surgery may affect:

Pressure measurement
Corneal biomechanics
Interpretation of the glaucoma risk
Choice of tonometer

It does not usually prevent trabeculectomy, tube or MIGS surgery.

Pre-LASIK pressure and corneal records are useful when available.

Can Surgery Be Performed on a Patient with Only One Seeing Eye?

Yes, when the expected benefit outweighs the risk.

The decision requires careful consideration of:

Current pressure
Rate of progression
Remaining visual field
Consequences of doing nothing
Surgical alternatives
Ability to attend intensive follow-up
Surgeon experience

Avoiding surgery is not necessarily the safest option when the remaining optic nerve is actively deteriorating.

Can Elderly Patients Undergo Glaucoma Surgery?

Yes.

Chronological age alone does not determine suitability.

The assessment includes:

General health
Ability to lie still
Anaesthetic risk
Life expectancy
Rate of progression
Severity of damage
Treatment burden
Patient goals

An older patient with rapidly progressing advanced glaucoma may benefit significantly from surgery.

Can Surgery Be Used in Normal-Tension Glaucoma?

Yes.

Normal-tension glaucoma may progress even when pressure is within the statistical normal range.

Surgery may be considered when:

Progression is confirmed
Eye drops and laser cannot achieve a sufficiently low target
Medication causes unacceptable side effects
Visual-field loss threatens fixation

These eyes require careful pressure control because the therapeutic range between the target pressure and hypotony may be relatively narrow.

Frequently Asked Questions

Is glaucoma surgery painful?

The eye is numbed during surgery.

Patients may feel pressure, movement or light but should not feel sharp pain.

Mild postoperative discomfort is common.

Will I be awake?

Many adults are awake with local anaesthesia and sedation.

General anaesthesia is used in selected circumstances.

Will the operation remove my glaucoma?

No.

It lowers pressure but does not eliminate the lifelong disease.

Does surgery improve vision?

It primarily preserves vision.

Vision may improve when cataract surgery is also performed.

Is trabeculectomy still used now that MIGS exists?

Yes.

Trabeculectomy remains one of the most effective ways to achieve a very low eye pressure and is particularly important in advanced or rapidly progressing glaucoma.

Is MIGS safer than trabeculectomy?

MIGS generally has a more favourable safety profile and faster recovery.

It usually provides less pressure reduction.

Is a tube safer than trabeculectomy?

The risks differ.

Tube surgery may be more successful in eyes with previous surgery or scarring, while trabeculectomy may require fewer postoperative medications and can achieve very low pressure.

Which operation has the highest success rate?

There is no universal answer.

Success depends on:

Target pressure
Glaucoma type
Previous surgery
Follow-up duration
Definition of success

Is a microshunt the same as MIGS?

Subconjunctival microshunts are sometimes grouped under MIGS, but unlike ordinary angle-based MIGS, they create a bleb and share some filtration-surgery risks.

Can surgery be performed before trying every eye drop?

Yes.

Primary trabeculectomy may be appropriate for advanced glaucoma, while MIGS may be offered during cataract surgery before the patient requires multiple medications.

Can I stop my drops before surgery?

Only when instructed.

Continue the usual medication unless the surgical team provides a different plan.

Why do I need so many steroid drops after trabeculectomy?

Inflammation promotes scar formation, which can close the new drainage pathway.

Steroids help control inflammation and scarring.

Can steroid drops raise pressure after surgery?

Yes.

The surgical team balances the need to prevent scarring against the possibility of a steroid pressure response.

Why is my pressure high immediately after surgery?

Possible causes include:

Inflammation
Tight sutures
Blood
Viscoelastic material
Tube ligation
Early scarring
Steroid response

Why is my pressure very low?

The eye may be draining too freely or producing less fluid temporarily.

The surgeon will assess whether treatment is needed.

Why is my vision blurry even though the pressure is lower?

Possible causes include:

Corneal swelling
Inflammation
Hypotony
Astigmatism
Dilating drops
Cataract
Blood in the eye
Ointment

Can the bleb burst?

A bleb can leak or become damaged, particularly if it is thin or injured.

Do not rub the eye.

Can I feel the tube implant?

The plate and tube are normally covered by the eyelid and conjunctiva.

Some patients notice mild awareness during early healing.

Can the tube be seen?

The external plate is hidden beneath the eyelid.

A small part of the tube may be visible to an eye doctor inside the eye.

Can airport security detect a glaucoma implant?

The implant is very small and does not normally trigger airport security systems.

Can I have an MRI with a glaucoma implant?

Most modern glaucoma drainage devices and stents are MRI compatible under specified conditions.

The patient should provide the implant name to the radiology team.

Can I fly after surgery?

Flying may be possible once the surgeon confirms that the eye is stable.

Different advice applies when a gas bubble has been placed inside the eye.

Can I swim after surgery?

Swimming is generally avoided during early healing because of infection risk.

Resume only after approval from the surgical team.

Can I bend down?

Brief gentle bending may be unavoidable, but prolonged deep bending, heavy lifting and straining are commonly avoided during the early recovery period.

Can I sleep on the operated side?

Follow the surgeon’s instructions.

Avoid direct pressure on the operated eye.

Can I read after surgery?

Yes, according to comfort.

Reading does not damage the operation, although vision may initially be blurred.

Can I use a phone or computer?

Yes, according to comfort.

Screen use does not cause surgical failure.

When can I wear eye makeup?

Wait until the eye has healed and the surgeon approves it.

Old eye makeup should be discarded when contamination is a concern.

Can I rub my eye after it has healed?

Forceful rubbing should remain avoided, particularly over a bleb or tube.

Can I have cataract surgery after trabeculectomy?

Yes.

The cataract surgeon must protect the filtering bleb and minimise postoperative inflammation.

Will cataract surgery damage the bleb?

It can increase inflammation and scarring, which may reduce bleb function.

The risk must be monitored.

Can a failed trabeculectomy be repaired?

Sometimes.

Options include:

Needling
Revision
Antiscarring treatment
A new filtration site
Tube implantation

Will I still need visual-field tests after surgery?

Yes.

Pressure control is intended to prevent field progression, but fields must be repeated to confirm stability.

A Practical Comparison of Glaucoma Operations

Procedure	Main mechanism	Typical role	Main limitation
Trabeculectomy	Creates a new filtering bleb	Advanced glaucoma or very low target pressure	Intensive follow-up, hypotony, scarring and bleb infection risk
Tube implant	Drains through a tube to a plate	Complex glaucoma, scarring or previous failed surgery	Device exposure, corneal damage, diplopia and possible ongoing drops
Trabecular MIGS	Improves the natural drainage pathway	Mild-to-moderate open-angle glaucoma, often with cataract surgery	Usually provides modest pressure lowering
Subconjunctival microshunt	Creates a controlled bleb through a small tube	Intermediate option between MIGS and trabeculectomy	Scarring, needling and bleb-related risks
Lens extraction	Deepens the anterior chamber and opens the angle	Angle closure with cataract or lens crowding	Does not reverse permanent angle or optic-nerve damage
Cyclophotocoagulation	Reduces aqueous-fluid production	Refractory or selected uncontrolled glaucoma	Inflammation, hypotony and possible retreatment
Goniotomy or trabeculotomy	Opens the developmental drainage system	Primary congenital and selected childhood glaucoma	May require repeat or additional surgery

A Practical Surgical Pathway

Step 1: Confirm Progression and Target Pressure

Review:

Eye-pressure trend
Optic nerve
OCT
Visual field
Treatment adherence
Remaining lifetime risk

Step 2: Identify the Glaucoma Mechanism

Determine whether the angle is:

Open
Narrow
Closed
Scarred
Abnormal from trauma
Obstructed by new blood vessels

Step 3: Review Previous Treatment

Consider:

Eye drops
Laser
Cataract surgery
Previous glaucoma surgery
Conjunctival condition

Step 4: Match the Operation to the Required Pressure

Mild or moderate disease with cataract: consider MIGS.
Very low target: consider trabeculectomy.
Previous surgery or complex secondary glaucoma: consider tube implantation.
Intermediate target with suitable conjunctiva: consider microshunt.
Angle closure with lens crowding: consider lens extraction.
Refractory disease: consider cyclophotocoagulation.

Step 5: Discuss Benefits, Risks and Alternatives

Alternatives may include:

Additional medication
Preservative-free drops
Selective laser trabeculoplasty
Repeat laser
Observation in selected stable disease
A different surgical procedure

Step 6: Plan Postoperative Care

Confirm:

Drop schedule
Follow-up visits
Activity restrictions
Transport
Work leave
Emergency contact instructions

Step 7: Monitor Long-Term Stability

Continue:

Pressure measurement
OCT
Visual fields
Bleb or implant examination
Corneal assessment
Review of medication

Common Myths About Glaucoma Surgery

“Surgery restores the vision glaucoma has taken.”

False.

Existing optic-nerve damage is usually permanent.

“Surgery means the glaucoma is cured.”

False.

Pressure can rise again and monitoring remains lifelong.

“MIGS is always better because it is newer.”

False.

MIGS is safer and less invasive but usually less powerful than trabeculectomy or tube surgery.

“Trabeculectomy is outdated.”

False.

It remains an important operation when a very low pressure is required.

“A tube is only used after trabeculectomy fails.”

False.

Tube implantation may be chosen as the first incisional operation in selected complex or scarred eyes.

“A normal pressure after surgery means I no longer need OCT or fields.”

False.

The optic nerve may progress despite a pressure that appears normal.

“The operation is finished once I leave the theatre.”

False.

Postoperative adjustment and scar control are essential parts of filtration surgery.

“A painful red eye years after trabeculectomy is probably ordinary conjunctivitis.”

False.

It may be a bleb infection and requires urgent assessment.

The Bottom Line

Glaucoma surgery lowers eye pressure to protect the optic nerve.

It does not normally restore vision already lost.

The principal operations include:

Trabeculectomy: creates a new drainage pathway and filtering bleb. It is highly effective when a low target pressure is required.
Glaucoma drainage implant: uses a tube and plate to divert aqueous fluid and is particularly useful in complex or previously operated eyes.
MIGS: improves natural drainage with less tissue disruption and faster recovery, but generally provides more modest pressure reduction.
Subconjunctival microshunts: create a filtering bleb through a small device and sit between angle MIGS and traditional trabeculectomy.
Lens extraction: opens crowded drainage angles in selected angle-closure eyes.
Cyclophotocoagulation: reduces aqueous-fluid production in refractory or selected uncontrolled glaucoma.
Goniotomy and trabeculotomy: are central treatments for congenital and childhood glaucoma.

No operation is best for every patient.

The correct procedure depends on:

Type of glaucoma
Target pressure
Severity and progression
Previous surgery
Corneal and conjunctival health
Cataract status
Ability to attend postoperative follow-up
Individual priorities

Filtering surgery requires active postoperative management. Sutures may need adjustment, antiscarring treatment may be given and blebs may require needling.

Long-term monitoring remains essential because:

Scar tissue may develop.
Pressure may rise again.
Additional medication may be required.
The optic nerve may progress despite an apparently acceptable pressure.

The aim of glaucoma surgery is not simply to produce a lower pressure reading. It is to achieve a pressure low enough—and stable enough—to preserve useful vision for the rest of the patient’s life.

References

Gedde SJ, et al. Primary Open-Angle Glaucoma Preferred Practice Pattern. Ophthalmology. 2026.
National Eye Institute. Glaucoma Surgery. Updated December 2024.
National Institute for Health and Care Excellence. Glaucoma: Diagnosis and Management. Guideline NG81. Reviewed March 2025.
King AJ, et al. Five-Year Results of the Treatment of Advanced Glaucoma Study. Ophthalmology. 2024.
Gedde SJ, et al. Treatment Outcomes in the Primary Tube Versus Trabeculectomy Study After Five Years. Ophthalmology. 2022.
Gedde SJ, et al. Postoperative Complications in the Primary Tube Versus Trabeculectomy Study During Five Years of Follow-Up. Ophthalmology. 2022.
Gedde SJ, et al. Treatment Outcomes in the Tube Versus Trabeculectomy Study After Five Years. American Journal of Ophthalmology. 2012.
Ahmed IIK, et al. Long-Term Outcomes from the HORIZON Randomised Trial for a Schlemm’s Canal Microstent Combined with Cataract Surgery. Ophthalmology. 2022.
Richter GM, et al. Trabecular Procedures Combined with Cataract Surgery for Open-Angle Glaucoma: An American Academy of Ophthalmology Report. Ophthalmology. 2024.
Panarelli JF, et al. Ab Externo MicroShunt Versus Trabeculectomy in Primary Open-Angle Glaucoma: Five-Year Randomised Trial Results. Ophthalmology Glaucoma. 2025.
Scheres LMJ, et al. Five-Year Follow-Up with the PreserFlo MicroShunt for Open-Angle Glaucoma. Eye. 2025.
American Academy of Ophthalmology. Primary Angle-Closure Disease Preferred Practice Pattern. Ophthalmology. 2026.
Moorfields Eye Hospital. Bleb Needling.
Moorfields Eye Hospital. Bleb-Related Infection.
Kaur K, et al. Primary Congenital Glaucoma. StatPearls. Updated 2024.