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Glaucoma: Symptoms, Types, Diagnosis and Treatment

Author: Dr Val Phua
Estimated reading time: 20 minutes

Glaucoma is a group of eye diseases that cause progressive damage to the optic nerve—the structure that carries visual information from the retina to the brain.

The damage is permanent. Vision already lost from glaucoma cannot currently be restored, but early diagnosis and appropriate treatment can often slow or prevent further deterioration.

Glaucoma is frequently associated with raised pressure inside the eye, known as intraocular pressure or IOP. However:

High eye pressure does not always mean that glaucoma is present.
Glaucoma can develop despite pressure readings within the statistically normal range.
The pressure that is safe for one optic nerve may be too high for another.
A single pressure measurement cannot diagnose or exclude glaucoma.

Most open-angle glaucoma develops slowly and causes no pain or obvious early symptoms. Peripheral visual-field loss can become substantial before the patient becomes aware of it.

This makes glaucoma one of the most commonly undiagnosed serious eye conditions. In the Singapore Epidemiology of Eye Diseases Study, more than 70% of participants found to have primary glaucoma had not previously been diagnosed, and over half already had moderate or worse visual-field damage in at least one eye.

Glaucoma is a major global cause of irreversible blindness. Earlier projections estimated that approximately 112 million people would be affected worldwide by 2040, with a disproportionate burden in Asia and Africa. Updated analyses continue to predict rising prevalence as populations age.

The Quick Answer

What Is Glaucoma?

Glaucoma is a progressive optic neuropathy in which retinal ganglion cells and their nerve fibres are damaged.

Typical changes may include:

Thinning of the retinal nerve fibre layer
Loss of retinal ganglion cells
Enlargement or deepening of the optic-nerve cup
Notching of the optic-nerve rim
Characteristic visual-field loss

The diagnosis is based on the overall clinical picture rather than one pressure value, one scan or one visual-field result.

What Are the First Symptoms?

Most patients with primary open-angle glaucoma have no early symptoms.

The disease may gradually affect:

Side vision
Contrast
Dark adaptation
Ability to detect moving objects
Visual confidence in crowded environments

Patients may not notice peripheral loss because:

The brain fills in missing information.
The other eye compensates.
Damage progresses gradually.
Central reading vision may remain good until late disease.

This is why routine comprehensive eye examinations are important, particularly for people with risk factors.

Can Glaucoma Cause Sudden Symptoms?

Most glaucoma is chronic and painless.

Acute angle closure is different. It may cause:

Severe eye pain
Headache
Redness
Sudden blurred vision
Halos around lights
Nausea
Vomiting

These symptoms require immediate emergency eye care because high pressure can damage the optic nerve rapidly.

Can Glaucoma Be Cured?

Glaucoma cannot currently be permanently cured, and established optic-nerve damage is irreversible.

Treatment can:

Lower eye pressure
Reduce the risk of further nerve damage
Slow visual-field loss
Preserve useful vision
Reduce the likelihood of blindness

Long-term randomised trials have shown that lowering IOP reduces glaucoma progression.

Does Everyone With High Eye Pressure Need Treatment?

No.

Raised pressure without detectable optic-nerve or visual-field damage is called ocular hypertension.

The decision to treat depends on the estimated risk of developing glaucoma, including:

Level of IOP
Corneal thickness
Age
Optic-nerve appearance
Visual-field findings
Family history
Life expectancy
Other ocular risk factors

In the Ocular Hypertension Treatment Study, the long-term risk varied substantially between low-, medium- and high-risk individuals. After 20 years, approximately one-quarter developed visual-field loss in at least one eye, supporting personalised rather than automatic treatment of every elevated pressure reading.

Understanding the Optic Nerve

What Is the Optic Nerve?

The optic nerve is composed of more than a million nerve fibres originating from retinal ganglion cells.

These fibres carry visual signals from the eye to the brain.

Glaucoma gradually damages these fibres.

What Is the Optic Disc?

The optic disc is the visible front surface of the optic nerve at the back of the eye.

During an examination, the ophthalmologist assesses:

Disc size
Cup size
Neuroretinal rim
Rim colour
Rim notching
Disc haemorrhage
Asymmetry between the eyes
Surrounding nerve-fibre layer

What Is Optic-Nerve Cupping?

The centre of the optic disc contains a depression called the cup.

Some healthy people naturally have large cups, particularly when the optic discs themselves are large.

Glaucoma is suspected when there is:

Progressive cup enlargement
Focal rim loss
Vertical elongation
Asymmetry
Disc haemorrhage
Corresponding OCT or visual-field damage

A large cup alone does not always mean glaucoma, and a small cup does not completely exclude it.

Understanding Eye Pressure

What Creates Eye Pressure?

A clear fluid called aqueous humour is continuously produced inside the eye.

It flows:

From behind the iris
Through the pupil
Into the anterior chamber
Towards the drainage angle
Through the trabecular meshwork
Into the eye’s venous circulation

IOP reflects the balance between aqueous production and drainage.

What Is the Drainage Angle?

The drainage angle is where the cornea and iris meet.

It contains the trabecular meshwork, the eye’s principal conventional drainage pathway.

The angle may be:

Open
Narrow
Intermittently closed
Permanently closed by adhesions
Obstructed by pigment, inflammation, blood or abnormal tissue

What Is a Normal Eye Pressure?

Population pressure readings commonly cluster around the mid-teens, but there is no pressure value that is universally safe.

A patient may develop glaucoma with an IOP of 15 mmHg, while another may remain healthy with a pressure above 21 mmHg.

The significance of an IOP reading depends on:

Optic-nerve susceptibility
Corneal thickness and biomechanics
Pressure fluctuation
Existing damage
Age
Vascular factors
Treatment history

Can Eye Pressure Change During the Day?

Yes.

IOP may vary with:

Time of day
Body position
Medication timing
Exercise
Stress
Fluid intake
Measurement method
Previous eye surgery

A normal clinic reading does not guarantee that pressure is always normal.

The Main Types of Glaucoma

Primary Open-Angle Glaucoma

Primary open-angle glaucoma is a chronic progressive optic neuropathy in which the drainage angle is anatomically open.

Aqueous fluid still reaches the trabecular meshwork, but drainage resistance is increased.

It commonly:

Develops gradually
Causes no early pain
Affects peripheral vision before central vision
Requires lifelong monitoring
May occur with high or statistically normal IOP

Current guidelines recommend establishing an individual target pressure and monitoring both structural and functional progression.

Normal-Tension Glaucoma

Normal-tension glaucoma is a form of open-angle glaucoma in which characteristic nerve and visual-field damage occurs without repeatedly measured high IOP.

Possible contributing factors may include:

Greater optic-nerve susceptibility
Vascular dysregulation
Low blood pressure
Migraine
Raynaud-type symptoms
Obstructive sleep apnoea
Thin corneas
Unrecorded pressure peaks

Lowering IOP remains the principal proven treatment, even when the starting pressure is not high.

Ocular Hypertension

Ocular hypertension means that IOP is higher than expected without definite glaucomatous optic-nerve or visual-field damage.

It is a risk state rather than established glaucoma.

Long-term risk is higher with:

Greater IOP
Older age
Thinner central cornea
Larger cup-to-disc ratio
Abnormal visual-field indices

The OHTS findings support calculating overall risk rather than treating solely according to a threshold such as 21 mmHg.

Glaucoma Suspect

A person may be considered a glaucoma suspect because of:

Raised IOP
Suspicious optic-nerve appearance
Thin nerve-fibre layer
Family history
Disc asymmetry
Possible visual-field changes
Pigment dispersion
Pseudoexfoliation
Other risk factors

A suspect does not necessarily have glaucoma, but requires appropriate baseline testing and follow-up.

Primary Angle-Closure Suspect

A primary angle-closure suspect has a narrow or occludable drainage angle without established pressure-related damage, significant adhesions or glaucomatous optic neuropathy.

Not every anatomically narrow angle progresses.

Long-term data from the ZAP trial showed that prophylactic laser iridotomy reduced progression, but the absolute rate of serious progression in untreated community-screened eyes was relatively low. Treatment should therefore be individualised according to anatomy and risk.

Primary Angle Closure

Primary angle closure is present when a narrow angle is associated with features such as:

Raised IOP
Peripheral anterior synechiae
Previous acute angle closure
Evidence that the trabecular meshwork has been obstructed

Glaucomatous nerve damage is not yet necessarily present.

Primary Angle-Closure Glaucoma

Primary angle-closure glaucoma occurs when angle closure has caused glaucomatous optic-nerve damage.

It may develop:

Gradually without pain
Through intermittent episodes
After an acute attack
Through chronic progressive closure

Angle-closure disease is especially important in Asian populations. Many patients have chronic, asymptomatic disease rather than a dramatic acute attack.

Acute Angle-Closure Glaucoma

Acute angle closure occurs when the drainage angle becomes suddenly obstructed and IOP rises rapidly.

Symptoms may include:

Severe eye pain
Headache
Red eye
Sudden blur
Rainbow haloes
Nausea
Vomiting

The cornea may become cloudy and the pupil may be mid-dilated and poorly reactive.

Immediate treatment is required to:

Lower pressure
Clear the cornea
Relieve the angle closure
Prevent permanent optic-nerve damage
Protect the fellow eye

Secondary Glaucoma

Secondary glaucoma results from another ocular or systemic condition.

Examples include:

Steroid-induced glaucoma
Pseudoexfoliative glaucoma
Pigmentary glaucoma
Uveitic glaucoma
Neovascular glaucoma
Traumatic glaucoma
Lens-related glaucoma
Glaucoma after retinal surgery
Glaucoma after corneal transplantation
Glaucoma caused by tumours or abnormal tissue

Treatment must address both the raised pressure and the underlying cause.

Congenital and Childhood Glaucoma

Primary congenital glaucoma results from abnormal development of the drainage structures.

Possible signs include:

Excessive watering
Light sensitivity
Eyelid squeezing
Enlarged eye
Cloudy cornea
Increasing corneal diameter

Childhood glaucoma may also occur after:

Cataract surgery
Uveitis
Trauma
Developmental eye disorders
Steroid treatment

Congenital glaucoma often requires early surgery to protect the developing visual system.

Pseudoexfoliative Glaucoma

What Is Pseudoexfoliation?

Pseudoexfoliation is an age-related disorder in which abnormal fibrillar material accumulates in and around structures at the front of the eye.

It may be visible on:

The pupil margin
The front of the lens
The drainage angle
The zonules supporting the lens

Why Does It Matter?

Pseudoexfoliation may cause:

Higher and more variable IOP
More aggressive glaucoma
Asymmetrical disease
Weakened lens-supporting zonules
Greater complexity during cataract surgery

Pressure and visual-field progression may require closer monitoring.

Pigmentary Glaucoma

What Is Pigment Dispersion?

Pigment dispersion occurs when pigment from the back of the iris is released into the eye.

The pigment may accumulate within the trabecular meshwork and increase drainage resistance.

Who Is More Commonly Affected?

Pigment dispersion is often associated with:

Younger or middle-aged adults
Myopia
Deep anterior chambers
Characteristic iris configuration

Some patients experience temporary pressure elevation after exercise or pupil dilation.

Steroid-Induced Glaucoma

Which Steroids Can Raise Eye Pressure?

Pressure may rise after steroids given as:

Eyedrops
Eye ointment
Tablets
Inhalers
Nasal sprays
Skin creams near the eyes
Injections around or inside the eye
Systemic infusions

The risk depends on:

Steroid potency
Duration
Route
Individual susceptibility
Existing glaucoma
Family history
Age

Should Steroids Be Stopped?

Do not stop medically necessary steroid treatment without discussing it with the prescribing doctor.

The ophthalmologist may:

Reduce the dose
Change the preparation
Monitor IOP
Add pressure-lowering treatment
Treat the underlying inflammation using another strategy

Neovascular Glaucoma

What Causes It?

Severe retinal ischaemia can stimulate abnormal blood vessels to grow over the iris and drainage angle.

Possible causes include:

Proliferative diabetic retinopathy
Central retinal-vein occlusion
Ocular ischaemic syndrome
Other severe retinal vascular disease

Why Is It Serious?

The abnormal vessels are accompanied by scar tissue that closes the drainage angle.

The condition may cause:

Very high IOP
Severe pain
Redness
Rapid visual loss
Corneal swelling

Treatment may include:

Anti-VEGF injection
Retinal laser
Pressure-lowering medication
Glaucoma surgery
Treatment of the underlying retinal disease

Risk Factors for Glaucoma

Increasing Age

Glaucoma becomes more common with age.

Age also increases the likelihood that undiagnosed disease has already caused meaningful damage.

Family History

A parent or sibling with glaucoma increases risk.

Family members should know:

Which type of glaucoma is present
Whether it affects one or both eyes
Whether surgery was required
The age at diagnosis

High Intraocular Pressure

IOP is the most important modifiable risk factor.

The Early Manifest Glaucoma Trial demonstrated that treatment reducing IOP approximately halved the risk of progression.

Ethnicity

Primary open-angle glaucoma is more common and may be more severe in people of African ancestry.

Angle-closure disease is particularly important in Asian populations.

Singapore population studies have demonstrated substantial undiagnosed glaucoma across Chinese, Malay and Indian communities, underlining the importance of examination rather than relying on symptoms.

Thin Central Cornea

A thin cornea may:

Cause applanation pressure to read lower
Be an independent marker of increased glaucoma risk
Influence interpretation of ocular hypertension

Central corneal thickness is one component of risk assessment, not a direct mathematical correction that precisely reveals the “true” IOP.

Myopia

Moderate and high myopia are associated with increased open-angle glaucoma risk.

Diagnosis may be more difficult because myopia can cause:

Tilted optic discs
Peripapillary atrophy
Naturally thin nerve-fibre measurements
Atypical visual-field defects
OCT segmentation errors

Hyperopia and Shorter Eyes

Long-sighted eyes are often anatomically shorter and may have:

Shallower anterior chambers
Narrower angles
Greater angle-closure risk

Previous Eye Injury

Trauma may damage:

The trabecular meshwork
Lens
Iris
Ciliary body
Angle structures

Glaucoma may develop immediately or many years later.

Steroid Exposure

Some people are strong steroid responders and develop substantial IOP elevation.

Pseudoexfoliation or Pigment Dispersion

Both can increase the risk of secondary open-angle glaucoma.

Obstructive Sleep Apnoea

Sleep apnoea has been associated with glaucoma in observational research.

Patients with symptoms such as loud snoring, witnessed breathing pauses and excessive daytime sleepiness should seek appropriate medical assessment.

Vascular Factors

Possible relevant factors in selected patients include:

Very low blood pressure
Nocturnal hypotension
Migraine
Raynaud-type vascular symptoms
Cardiovascular disease

These associations do not mean that blood-pressure medication should be stopped. Management should be coordinated with the treating physician.

Symptoms of Chronic Glaucoma

No Symptoms

The most common early symptom is no symptom at all.

Peripheral Visual-Field Loss

As disease progresses, patients may have difficulty:

Detecting objects approaching from the side
Navigating crowds
Finding items on a table
Seeing steps
Avoiding door frames
Driving safely

Tunnel Vision

Advanced glaucoma may leave only a central island of vision.

The term “tunnel vision” describes the late stage rather than the usual early presentation.

Central Visual Loss

Central vision may be affected:

In advanced disease
In normal-tension glaucoma with defects near fixation
When damage involves the macular ganglion-cell region
When another eye condition coexists

Difficulty in Dim Light

Patients may struggle with:

Dark corridors
Night driving
Moving between bright and dim environments
Low-contrast steps

Glare and Contrast Problems

Glaucoma may reduce functional vision even when ordinary high-contrast acuity remains good.

Falls and Mobility Problems

Advanced bilateral field loss may increase difficulty with:

Stairs
Kerbs
Obstacles
Crowded environments
Balance and mobility

How Is Glaucoma Diagnosed?

Medical and Family History

The ophthalmologist may ask about:

Family history
Steroid use
Eye trauma
Previous surgery
Migraine
Sleep apnoea
Cardiovascular medication
Diabetes
Current eyedrops
Adherence
Previous pressure readings

Visual-Acuity Testing

Visual acuity measures central high-contrast vision.

A person may have early or moderate glaucoma despite seeing 6/6.

Eye-Pressure Measurement

Common methods include:

Goldmann applanation tonometry
Non-contact air-puff tonometry
Rebound tonometry
Handheld applanation devices
Corneal-compensated measurements

One measurement provides only a snapshot.

Central Corneal Thickness

Pachymetry measures corneal thickness.

It helps interpret IOP and estimate glaucoma risk.

Gonioscopy

Gonioscopy uses a specialised contact lens to examine the drainage angle.

It determines whether the angle is:

Open
Narrow
Closed
Scarred
Pigmented
Abnormal after trauma
Affected by new vessels or pseudoexfoliation

Gonioscopy remains essential because ordinary examination cannot directly visualise the angle adequately.

Optic-Nerve Examination

The ophthalmologist assesses:

Cup-to-disc ratio
Neuroretinal rim
Disc haemorrhage
Nerve-fibre defects
Asymmetry
Progressive change

Optic-Disc Photography

Photography provides a permanent baseline for detecting changes over time.

Optical Coherence Tomography

OCT measures structures such as:

Peripapillary retinal nerve fibre layer
Ganglion-cell and inner plexiform layers
Optic-nerve head anatomy
Macular ganglion-cell complex

OCT can detect structural thinning before the patient notices symptoms.

However, scans may be misleading because of:

High myopia
Segmentation errors
Poor signal
Tilted discs
Retinal disease
Normal anatomical variation

The scan must be interpreted together with the clinical examination and visual field.

Visual-Field Testing

Automated perimetry measures how sensitive different parts of the visual field are.

Common tests include:

24-2
24-2C
30-2
10-2

The test may detect:

Nasal steps
Arcuate defects
Paracentral defects
Generalised depression
Advanced peripheral loss

Visual-field testing is subjective and may improve with practice. Repeat testing is often necessary before concluding that true progression has occurred.

Why Are Both OCT and Visual Fields Needed?

OCT measures structure.

Visual-field testing measures function.

One may show progression before the other. Long-term monitoring generally requires both.

Anterior-Segment OCT or Ultrasound

These tests may help evaluate:

Angle width
Iris configuration
Lens position
Plateau iris
Ciliary-body abnormalities

They complement but do not always replace gonioscopy.

What Is a Target Eye Pressure?

An Individualised Goal

A target IOP is the pressure range at which the clinician expects the risk of further damage to be acceptably low.

It depends on:

Starting pressure
Stage of glaucoma
Rate of progression
Age and life expectancy
Visual field in the other eye
Corneal thickness
Previous treatment
Other ocular disease

The Target Can Change

The target may need to be lowered if:

OCT continues to thin.
The visual field worsens.
Disc haemorrhages occur.
Damage threatens central fixation.
The patient has a long expected lifetime.
Progression occurs despite apparently satisfactory pressure.

A stable patient may not require the same low target as a rapidly progressing patient.

Measuring Progression

Why Repeat Testing Matters

Glaucoma management is not based solely on whether the pressure is “good today.”

The essential question is whether the optic nerve is stable over time.

Monitoring may include:

Serial visual fields
OCT progression analysis
Disc photographs
IOP trends
Examination of the optic nerve
Assessment of medication adherence

Rate of Progression

Some patients progress very slowly.

Others lose vision rapidly.

The treatment intensity should reflect:

Present damage
Speed of change
Years of vision the patient is expected to need

Treatment Principles

Lowering IOP Is the Main Proven Strategy

Current glaucoma treatment primarily lowers IOP through:

Eyedrops
Laser
Surgery
Lens extraction in selected angle-closure disease

IOP reduction slows progression even when the untreated pressure is not particularly high.

Treatment Does Not Improve Every Existing Defect

Treatment aims to preserve remaining vision.

Patients may not feel an immediate improvement because pressure-lowering treatment does not usually restore the visual field already lost.

Glaucoma Eyedrops

Prostaglandin Analogues

Examples include:

Latanoprost
Travoprost
Bimatoprost
Tafluprost

They mainly increase aqueous outflow.

Possible effects include:

Eye redness
Longer or darker eyelashes
Darkening of the iris
Darkening of eyelid skin
Deepening around the upper eyelid
Rare inflammation or macular oedema in selected eyes

They are commonly used once daily.

Beta-Blockers

Examples include:

Timolol
Betaxolol

They reduce aqueous production.

Possible systemic effects include:

Slower heart rate
Lower blood pressure
Breathing difficulty
Fatigue
Worsening asthma
Masking low blood sugar symptoms

Inform the doctor if you have asthma, heart block, slow pulse or significant heart disease.

Alpha-2 Agonists

The principal example is brimonidine.

Possible effects include:

Allergy
Redness
Dry mouth
Fatigue
Drowsiness
Lower blood pressure

Brimonidine requires particular caution in young children because of central nervous-system effects.

Carbonic Anhydrase Inhibitors

Topical examples include:

Dorzolamide
Brinzolamide

Oral examples include:

Acetazolamide
Methazolamide

Possible effects of topical treatment include:

Stinging
Blurred vision
Bitter taste
Corneal problems in susceptible eyes

Oral acetazolamide may cause:

Tingling
Frequent urination
Fatigue
Altered taste
Electrolyte disturbance
Kidney stones
Rare serious blood disorders

Oral treatment is often used temporarily for significant pressure elevation.

Rho-Kinase Inhibitors

Examples vary by country and may include:

Netarsudil
Ripasudil

Possible effects include:

Marked conjunctival redness
Corneal verticillata
Small conjunctival haemorrhages
Eyelid irritation

Miotic Drops

Pilocarpine constricts the pupil and alters the iris configuration.

It may be used in selected angle-closure or other glaucoma situations.

Possible effects include:

Brow ache
Blurred distance vision
Reduced night vision
Smaller pupil
Retinal-detachment risk in susceptible eyes

Combination Drops

Combination products reduce the number of bottles and may simplify treatment.

However, they still require correct timing and technique.

How to Use Glaucoma Drops Correctly

One Drop Is Enough

The eye cannot hold several full drops at once.

Excess medication runs onto the face or into the nose.

A Practical Technique

Wash your hands.
Tilt your head back.
Pull the lower lid down gently.
Place one drop into the pocket.
Close the eye gently.
Press lightly at the inner corner near the nose.
Keep the eye closed for approximately one to two minutes.
Wait before using another type of eyedrop.

Nasolacrimal occlusion and eyelid closure can reduce systemic absorption.

Separate Different Drops

Leave several minutes between different medications to avoid washing one out with the next.

Do Not Stop Because the Eyes Feel Normal

Glaucoma is often asymptomatic.

The absence of discomfort does not mean treatment is unnecessary.

Tell the Doctor About Difficulties

Common barriers include:

Forgetfulness
Cost
Stinging
Allergy
Difficulty squeezing the bottle
Missing the eye
Running out early
Complex schedules

Laser or surgery may be considered when adherence or tolerance is poor.

Selective Laser Trabeculoplasty

What Is SLT?

Selective laser trabeculoplasty, or SLT, applies low-energy laser treatment to the trabecular meshwork.

It improves aqueous drainage in many eyes with:

Primary open-angle glaucoma
Ocular hypertension
Selected secondary open-angle glaucomas

Can SLT Be Used First?

Yes.

The LiGHT trial showed that SLT is an effective first-line option for open-angle glaucoma and ocular hypertension.

At six years, approximately 70% of patients initially treated with SLT remained free of pressure-lowering drops, with better long-term disease control and less need for incisional glaucoma or cataract surgery than patients initially treated with medication.

What Happens During SLT?

The eye is numbed.

A contact lens is placed on the eye, and laser spots are applied to the drainage angle.

The procedure generally takes a few minutes.

Does It Hurt?

Patients may feel:

Pressure
Mild discomfort
Bright flashes

Significant pain is uncommon.

Does It Work Permanently?

The effect may last for several years but can decrease over time.

SLT may sometimes be repeated.

Possible Risks

Possible effects include:

Temporary inflammation
Short-lived pressure elevation
Mild discomfort
Blurred vision
Inadequate pressure reduction
Rare prolonged inflammation

Laser Peripheral Iridotomy

What Is LPI?

Laser peripheral iridotomy creates a small opening in the peripheral iris.

This allows aqueous to move more freely from behind the iris to the anterior chamber and relieves pupil-block angle closure.

Who May Need It?

LPI may be used for:

Acute angle closure
Primary angle closure
Primary angle-closure glaucoma
Selected high-risk narrow angles
The fellow eye after an acute attack
Certain secondary pupil-block mechanisms

Does LPI Completely Cure Narrow Angles?

Not always.

After LPI, the angle may remain narrow because of:

Plateau iris
Large or forward-positioned lens
Peripheral anterior synechiae
Other anatomical factors

Further treatment may include:

Lens extraction
Iridoplasty
Glaucoma medication
Surgery

Should Every Narrow Angle Receive LPI?

No.

Long-term randomised evidence suggests that many community-detected angle-closure suspects have a relatively low absolute progression risk, although LPI reduces that risk.

Treatment is more strongly considered when additional risk factors are present, such as:

Very narrow anatomy
Elevated IOP
Synechial closure
Symptoms
Family history
Need for frequent pupil dilation
Limited access to emergency care
Use of medications that may precipitate closure

Lens Extraction for Angle Closure

Why Can the Lens Cause Angle Closure?

The natural lens becomes thicker with age and may crowd the anterior chamber.

Removing it can:

Deepen the chamber
Open the drainage angle
Reduce pupil block
Lower IOP
Reduce medication requirements

Cataract Surgery

When a visually significant cataract and angle closure coexist, cataract extraction may treat both problems.

Clear-Lens Extraction

In selected patients with primary angle closure or angle-closure glaucoma and high IOP, lens extraction may be considered even when the lens is not significantly cloudy.

The EAGLE trial found that early clear-lens extraction provided better pressure control, quality-of-life outcomes and cost-effectiveness than standard initial laser iridotomy-based care in the trial’s selected population. It should not be applied automatically to every narrow angle.

Minimally Invasive Glaucoma Surgery

What Is MIGS?

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

Procedures may act by:

Bypassing the trabecular meshwork
Removing part of the trabecular meshwork
Dilating Schlemm’s canal
Creating a subconjunctival drainage pathway
Accessing the suprachoroidal space

Who May Benefit?

MIGS is commonly considered for:

Mild or moderate glaucoma
Patients undergoing cataract surgery
Reducing medication burden
Patients who do not yet require very low target pressures

Limitations

Many MIGS procedures produce more modest pressure lowering than trabeculectomy.

They may be insufficient for:

Advanced glaucoma
Rapid progression
Very low target IOP
Severe angle closure
Extensive scarring
Some secondary glaucomas

The choice depends on the specific device, glaucoma type and target pressure.

Trabeculectomy

What Is Trabeculectomy?

Trabeculectomy creates a new drainage pathway from inside the eye to a controlled reservoir under the upper eyelid called a filtering bleb.

It can achieve substantial IOP reduction and remains important when a very low target pressure is required.

When Is It Considered?

Possible indications include:

Advanced glaucoma
Progression despite drops and laser
Very low target pressure
Medication intolerance
Failure of less invasive surgery

Postoperative Care

Recovery requires close follow-up because the drainage pathway may need adjustment through:

Suture manipulation
Laser suture lysis
Additional medication
Anti-scarring injections
Bleb needling

Possible Risks

Risks include:

Pressure that is too low
Shallow anterior chamber
Bleeding
Cataract progression
Infection
Bleb leak
Scarring and failure
Reduced vision
Rare severe intraocular infection

Glaucoma Drainage Implants

What Is a Tube Shunt?

A glaucoma drainage implant uses a small tube to carry aqueous from the anterior chamber to a plate positioned beneath the conjunctiva.

When Is It Used?

Tube surgery may be considered for:

Previous failed trabeculectomy
Neovascular glaucoma
Uveitic glaucoma
Eyes with significant conjunctival scarring
Complex secondary glaucoma
Selected primary glaucomas

Possible Risks

Potential complications include:

Low pressure
Corneal endothelial damage
Tube blockage
Tube exposure
Double vision
Bleeding
Infection
Need for revision

Cyclophotocoagulation

What Does It Do?

Cyclophotocoagulation applies laser energy to the ciliary body to reduce aqueous production.

Forms include:

Continuous-wave transscleral treatment
Micropulse treatment
Endoscopic treatment

When Is It Used?

It may be used for:

Refractory glaucoma
Painful eyes with poor visual potential
Eyes unsuitable for filtering surgery
Selected eyes with useful vision
Treatment after previous surgery

The treatment plan depends on the severity and the laser system used.

Cataract Surgery and Glaucoma

Can Cataract Surgery Lower Eye Pressure?

Cataract extraction may lower IOP modestly in some open-angle eyes and more substantially in certain angle-closure eyes.

The effect is variable and may not replace glaucoma treatment.

Combined Cataract and Glaucoma Surgery

Cataract surgery may be combined with:

MIGS
Trabeculectomy
Tube surgery
Goniosynechialysis
Endoscopic cyclophotocoagulation

The choice depends on:

Glaucoma stage
Target pressure
Number of drops
Angle anatomy
Cataract severity
Surgical risk

Which Intraocular Lens Is Suitable?

A monofocal or toric monofocal lens is often preferred in moderate or advanced glaucoma because it preserves contrast and provides straightforward optics.

Multifocal or trifocal lenses require caution because glaucoma may already reduce:

Contrast sensitivity
Visual fields
Low-light function

Selected patients with very early stable disease may still be considered for certain enhanced lenses after careful counselling.

Follow-Up After Treatment

Pressure Alone Is Not Enough

A successful pressure reading does not prove that the glaucoma is stable.

Follow-up may include:

IOP measurement
Visual fields
OCT
Optic-disc photographs
Gonioscopy
Medication review
Assessment of side effects
Review of adherence

How Often Is Follow-Up Needed?

The interval depends on:

Glaucoma type
Disease stage
Target pressure
Rate of progression
Recent treatment
Adherence
Stability of testing

Advanced or unstable glaucoma requires more frequent review than a low-risk stable suspect.

Can Glaucoma Be Prevented?

Not Every Case Can Be Prevented

Age, anatomy and genetics cannot be changed.

Severe Vision Loss Can Often Be Prevented

The most effective preventive actions are:

Comprehensive eye examinations
Early detection
Appropriate treatment
Correct use of medication
Reliable follow-up
Protection from eye injury
Careful monitoring during steroid use

Glaucoma blindness is far more likely when disease remains undiagnosed or treatment is inconsistent.

Lifestyle and Glaucoma

Exercise

Regular moderate aerobic exercise supports general health and may temporarily lower IOP in some people.

Patients should discuss activities involving:

Heavy straining
Breath-holding
Prolonged head-down posture
Inverted yoga positions
Tight goggles pressing on the eye

with their ophthalmologist when glaucoma is advanced or pressure-sensitive.

Blood Pressure

Both uncontrolled hypertension and excessively low ocular perfusion may be relevant.

Do not change blood-pressure medication without consulting the treating physician.

Sleep Apnoea

Patients with probable sleep apnoea should seek assessment and appropriate treatment.

Diet and Supplements

A balanced diet supports general health.

No vitamin, herbal remedy or nutritional supplement has been proven to replace pressure-lowering treatment.

Caffeine

A large caffeine dose may temporarily raise IOP in some individuals.

Ordinary moderate intake is not automatically prohibited, but patients with unstable glaucoma can discuss their intake with their ophthalmologist.

Cannabis

Cannabis can lower IOP briefly but has:

Short duration
Psychoactive effects
Cardiovascular effects
Inconsistent dosing
No proven long-term ability to preserve the visual field

It is not recommended as routine glaucoma treatment.

Glaucoma and Driving

Why Visual Fields Matter

Driving requires:

Peripheral awareness
Detection of moving vehicles
Pedestrian detection
Lane positioning
Hazard recognition
Night vision

A patient may maintain good central acuity while having significant field loss.

Can a Person With Glaucoma Drive?

Driving ability depends on:

Visual acuity
Binocular visual field
Disease severity
Rate of progression
Local licensing standards
Functional confidence

Advanced bilateral glaucoma may make driving unsafe even when the patient can read the number plate or eye chart.

Glaucoma During Pregnancy

Medication Review Is Important

Some glaucoma medicines may have potential effects during:

Pregnancy
Labour
Breastfeeding

Treatment should be reviewed before conception when possible.

Do Not Stop Drops Independently

Uncontrolled IOP can damage the optic nerve.

The ophthalmologist and obstetric team may adjust:

Medication choice
Dosing
Nasolacrimal occlusion
Laser timing
Surgical planning

Glaucoma in Children

Possible Warning Signs

Seek examination for:

Enlarged eye
Cloudy cornea
Excessive watering
Light sensitivity
Persistent eyelid squeezing
Reduced visual behaviour
Eye asymmetry

Treatment

Childhood glaucoma often requires surgery because developmental abnormalities of the drainage angle may not respond adequately to drops alone.

Long-term follow-up is required for:

Pressure control
Vision development
Amblyopia
Refractive error
Corneal clarity
Optic-nerve health

Common Myths

“Glaucoma Always Means High Eye Pressure”

False.

Normal-tension glaucoma occurs without consistently elevated clinic IOP.

“Normal Eye Pressure Means I Do Not Have Glaucoma”

False.

Diagnosis also requires examination of the optic nerve, OCT and visual fields.

“Glaucoma Causes Pain”

Most chronic glaucoma is painless.

Acute angle closure and some secondary glaucomas can be painful.

“I Will Notice Glaucoma Early”

Usually not.

Peripheral visual loss may become substantial before symptoms are recognised.

“Treatment Restores Lost Vision”

Current treatments mainly prevent or slow further loss.

“If My Pressure Is Low, I Can Stop the Drops”

The pressure may be low because the treatment is working.

“Glaucoma Drops Only Affect the Eye”

Some drops can affect the heart, lungs, blood pressure and nervous system.

“Laser Is Used Only When Drops Fail”

False.

SLT is an evidence-based first-line option for many patients with open-angle glaucoma or ocular hypertension.

“Glaucoma Surgery Permanently Cures the Disease”

Surgery lowers pressure but does not eliminate the need for lifelong monitoring.

“A Visual Field Test Is Unnecessary if the OCT Is Normal”

False.

Structure and function provide different information, and neither test is perfect.

Frequently Asked Questions

What Is the Difference Between Glaucoma and Ocular Hypertension?

Glaucoma involves optic-nerve damage.

Ocular hypertension means raised IOP without definite glaucomatous damage.

What Is a Glaucoma Suspect?

A glaucoma suspect has findings or risk factors that increase the likelihood of developing glaucoma but does not yet meet definite diagnostic criteria.

Is 21 mmHg the Cut-Off for Glaucoma?

No.

There is no universal diagnostic threshold.

Some patients develop damage below 21 mmHg, while others tolerate higher pressure.

Can Glaucoma Affect Only One Eye?

Yes.

It may begin in one eye or be much more advanced in one eye.

Both eyes still require monitoring.

Can Glaucoma Cause Headaches?

Chronic open-angle glaucoma usually does not.

Acute angle closure may cause severe headache, eye pain, nausea and vomiting.

Can Glaucoma Cause Floaters?

No.

Floaters arise from the vitreous.

New flashes, numerous floaters or a curtain require retinal assessment.

Can Glaucoma Cause Complete Blindness?

Yes, if sufficiently advanced.

Early detection and effective treatment substantially reduce this risk.

How Quickly Does Glaucoma Progress?

The rate varies greatly.

Some patients remain stable for decades, while others progress rapidly.

Serial OCT and visual-field testing help estimate the rate.

How Often Should I Check My Eye Pressure?

The interval depends on glaucoma type, severity, treatment and stability.

Eye pressure alone is not a complete glaucoma check.

Can Eye Pressure Be Checked at an Optician?

Pressure screening may identify some at-risk patients, but a complete glaucoma assessment also requires evaluation of:

Optic nerve
Drainage angle
Corneal thickness
OCT
Visual field

Can Glaucoma Be Diagnosed From OCT Alone?

No.

OCT may produce false-positive or false-negative results and must be interpreted with the full clinical examination.

Why Must I Repeat the Visual Field?

Visual fields have a learning effect and natural variability.

Repeated tests help confirm genuine defects and progression.

Is SLT Better Than Drops?

Both can be effective.

SLT avoids daily medication and has strong first-line evidence, while drops may be preferable or necessary in other situations.

Can SLT Be Repeated?

Often, yes.

The response to repeat treatment varies.

Will I Still Need Drops After Laser?

Possibly.

Some patients remain drop-free, while others require medication immediately or later.

When Is Glaucoma Surgery Needed?

Surgery is considered when:

Pressure remains above target
Damage progresses
Drops are not tolerated
Adherence is unreliable
Very low pressure is required
The glaucoma mechanism requires surgery

Can I Have Cataract Surgery if I Have Glaucoma?

Yes.

Cataract surgery may be performed alone or combined with glaucoma treatment.

Can I Use Steroid Drops if I Have Glaucoma?

Sometimes, but pressure should be monitored.

Use steroids only when prescribed.

Should My Family Members Be Checked?

Yes.

First-degree relatives should inform their eye-care professional about the family history and have appropriate comprehensive examinations.

When to Seek Emergency Eye Care

Seek immediate assessment for:

Sudden severe eye pain
Redness with blurred vision
Rainbow haloes
Headache with eye symptoms
Nausea or vomiting
Sudden major visual loss
A very hard or painful eye
New symptoms after glaucoma surgery
Significant trauma
Increasing pain or discharge after an operation

These symptoms may indicate:

Acute angle closure
Severe pressure elevation
Infection
Bleeding
Surgical complication
Another ophthalmic emergency

A Glaucoma Assessment Checklist

Risk Factors to Mention

Family history
Previous high IOP
Steroid use
Eye trauma
High myopia
Previous surgery
Sleep apnoea
Migraine
Raynaud symptoms
Blood-pressure treatment
African or Asian ancestry
Previous angle closure

Tests That May Be Required

Visual acuity
IOP measurement
Pachymetry
Gonioscopy
Dilated optic-nerve examination
Disc photography
OCT nerve-fibre analysis
Ganglion-cell analysis
Visual-field testing
Anterior-segment imaging

Questions to Ask

Do I have glaucoma, ocular hypertension or only suspicious findings?
Is my angle open or narrow?
What stage is the disease?
What is my target pressure?
Is the optic nerve progressing?
How often do I need OCT and visual fields?
Are drops, SLT or surgery most appropriate?
What side effects should I watch for?
Am I using my drops correctly?
Should my relatives be screened?
Is my driving vision safe?

The Bottom Line

Glaucoma is a group of diseases that progressively damage the optic nerve.

The main types include:

Primary open-angle glaucoma
Normal-tension glaucoma
Ocular hypertension
Primary angle-closure disease
Secondary glaucoma
Congenital and childhood glaucoma

Most chronic glaucoma causes no early symptoms.

The diagnosis requires assessment of:

Intraocular pressure
Optic-nerve appearance
Retinal nerve-fibre thickness
Ganglion-cell structure
Visual fields
Drainage-angle anatomy
Corneal thickness
Change over time

Eye pressure is important, but glaucoma is not defined by pressure alone.

Treatment aims to preserve remaining vision by lowering IOP through:

Eyedrops
Selective laser trabeculoplasty
Laser peripheral iridotomy
Lens extraction
Minimally invasive glaucoma surgery
Trabeculectomy
Drainage implants
Cyclophotocoagulation

The visual loss caused by glaucoma is permanent, but severe disability is not inevitable.

Early diagnosis, an appropriate target pressure, correct treatment and reliable long-term follow-up give patients the best chance of maintaining useful vision throughout life.

The most important principle is:

Do not wait for glaucoma symptoms before having your optic nerves checked—by the time chronic glaucoma becomes noticeable, significant vision may already have been lost.

References

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National Eye Institute. Glaucoma. National Institutes of Health. Updated November 26, 2025.