Understanding Glaucoma: A Complete Patient Guide

Understanding Glaucoma: A Complete Patient Guide, has been written by Dr Shibal Bhartiya, glaucoma specialist in Gurgaon, and last reviewed in March, 2026. Glaucoma is one of the leading causes of irreversible blindness in the world. In India, it affects an estimated 12 million people. Most of them do not know they have it.

This is the defining challenge of glaucoma. It does not announce itself. It causes no pain. It takes vision slowly, quietly, and permanently, starting at the edges, where you are least likely to notice.

This guide explains what glaucoma is, how it develops, who is at risk, how it is diagnosed, and how it is treated. It is written for patients who want to understand their disease clearly — and for those who want to know whether they should be screened.

Key Facts

• Glaucoma is a disease of the optic nerve — not simply a disease of eye pressure.
• It causes no pain and no early symptoms in most cases.
• Vision loss from glaucoma is irreversible. What is lost cannot be restored.
• Early detection through regular screening is the most powerful protection.
• Glaucoma is treatable. Most patients retain useful vision with early diagnosis and consistent care.
• Family history is one of the strongest risk factors. First-degree relatives need regular screening.

What Is Glaucoma?

Glaucoma is a group of eye diseases that damage the optic nerve. The optic nerve connects the eye to the brain. It carries the visual signals that create everything we see.

When the optic nerve is damaged, those signals are lost. The damage is permanent. No treatment can restore vision that glaucoma has already taken.

In most forms of glaucoma, raised intraocular pressure (IOP) — the pressure inside the eye — is the main driver of optic nerve damage. Fluid called aqueous humour constantly circulates inside the eye. When this fluid cannot drain properly, pressure builds up. Over time, that pressure damages the optic nerve fibres.

But glaucoma is not simply a pressure disease. Some patients develop optic nerve damage with entirely normal pressure. Others have high pressure for years without developing glaucoma. Pressure is important — but it is one factor in a more complex picture.

Why Glaucoma Is Called the Silent Thief of Sight

The optic nerve contains over one million nerve fibres. Glaucoma damages these fibres gradually. The nerve has a large functional reserve — it can lose up to 40% of its fibres before central vision is affected.

The first vision to be lost is peripheral — the edges of the visual field. This loss is so gradual that most patients do not notice it. The brain compensates. The other eye fills in gaps. By the time a patient realises something is wrong, the disease is often advanced.

There is no pain, and no redness in the early stages. There is no sudden change. Just quiet, steady, invisible loss.

This is why screening matters more than waiting for symptoms. In glaucoma, symptoms mean the disease is already advanced.

Types of Glaucoma

Glaucoma is not a single disease. It is a family of conditions. Understanding which type you have determines how it is managed.

Primary Open Angle Glaucoma (POAG)

This is the most common type. The drainage angle of the eye is open, but the drainage system works too slowly. Pressure rises gradually. Damage develops over years — often without any symptoms until late in the disease. POAG is the type most people mean when they say ‘glaucoma’.

Normal Tension Glaucoma (NTG)

In this type, optic nerve damage occurs despite normal eye pressure. Blood flow to the optic nerve, structural vulnerability, and other factors are involved. Normal tension glaucoma is often missed because doctors and patients assume that normal pressure means no glaucoma risk.

Angle Closure Glaucoma (Narrow Angle / PACG)

In this type, the drainage angle is physically blocked or too narrow. It can occur suddenly — an acute angle closure attack causes severe eye pain, blurred vision, redness, and nausea. But more often, it develops slowly and silently, just like open angle glaucoma. Angle closure is more common in people of Asian origin, in women, and in those with a plus spectacle number.

Ocular Hypertension

Eye pressure is raised, but the optic nerve shows no damage yet. This is not glaucoma — it is a risk state. Not all patients with high pressure develop glaucoma. But all need monitoring, and some need treatment.

Glaucoma Suspect

A patient is called a glaucoma suspect when one or more findings — suspicious optic nerve appearance, borderline pressure, or thin cornea — raise concern, but the diagnosis is not yet confirmed. Careful monitoring over time establishes whether glaucoma is developing.

Secondary Glaucoma

Secondary glaucoma arises as a consequence of another eye condition. Causes include pseudoexfoliation syndrome, pigment dispersion, uveitis, trauma, and steroid use. Treatment addresses both the underlying cause and the raised pressure.

Who Is at Risk of Glaucoma?

Anyone can develop glaucoma. But these factors significantly increase risk:

Family History

Glaucoma is strongly hereditary. If a parent or sibling has glaucoma, your risk is four to nine times higher than average. This is the single most actionable risk factor — it identifies who needs screening before symptoms appear. Regular family history glaucoma screening is essential for first-degree relatives.

Age

Risk rises steadily after age 40. After 60, glaucoma is significantly more common. But glaucoma can develop at any age, including in young adults and children.

Raised Eye Pressure

High intraocular pressure is the most important modifiable risk factor. But it neither confirms nor excludes glaucoma. Pressure must always be interpreted alongside optic nerve appearance, visual fields, and OCT findings.

Ethnicity

Open angle glaucoma is more common and more aggressive in people of African origin, often appearing at a younger age. Angle closure glaucoma is more prevalent in people of Asian and South Asian origin. Indian patients carry a significant burden of both types.

Refractive Error

High myopia (strong minus prescription) increases risk of open angle glaucoma. High hyperopia (plus prescription) increases risk of angle closure glaucoma.

Thin Cornea

A thin central cornea is associated with higher glaucoma risk. It also causes eye pressure to be under-read by tonometry — meaning actual pressure may be higher than measured. Corneal thickness measurement (pachymetry) is an important part of glaucoma risk assessment.

Systemic Conditions

Diabetes, cardiovascular disease, and migraine all affect blood flow to the optic nerve and increase glaucoma risk. Sleep apnoea has also been linked to optic nerve damage.

Steroid Use

Prolonged use of steroid eye drops, nasal sprays, or oral steroids can raise eye pressure and cause steroid-induced glaucoma. Patients on long-term steroids need regular eye pressure monitoring.

Early Glaucoma Symptoms: What to Watch For

In the early stages, most patients have no symptoms at all. This is not unusual. This is what understanding glaucoma means. It is the nature of the disease. When symptoms do appear, they are often subtle:

• Gradual loss of peripheral vision
• Small blind spots in the visual field
• Blurred vision
• Halos around lights, especially at night
• Frequent changes in spectacle prescription
• Difficulty adjusting between bright and dark environments

In advanced disease:

• Significant narrowing of the visual field
• Tunnel vision
• Difficulty reading or driving

Symptoms of an Acute Angle Closure Attack

Acute angle closure is a medical emergency. Seek immediate care if you experience:

• Severe eye pain
• Sudden significant blurring of vision
• Red eye
• Coloured halos around lights
• Headache, nausea, or vomiting

Most patients with glaucoma never experience an acute attack. The chronic, silent form is far more common and far more dangerous over time.

Emergency contact number: +91 9818700269 | +91 8882638735

How Is Glaucoma Diagnosed?

No single test diagnoses glaucoma. Diagnosis requires a combination of assessments, interpreted together by a glaucoma specialist. This is why a dedicated glaucoma evaluation is different from a routine eye check. Recognising this is important for understanding glaucoma.

Eye Pressure Measurement (Tonometry)

Intraocular pressure is measured at every glaucoma appointment. The normal range is 10–21 mmHg. But normal pressure does not rule out glaucoma — and raised pressure does not confirm it. Pressure must be measured at multiple time points. It varies with time of day.

Optic Nerve Examination

The optic nerve is examined directly through a dilated pupil. A glaucoma specialist looks for cupping of the nerve, notching of the neuroretinal rim, asymmetry between the two eyes, and disc haemorrhages. This examination is the cornerstone of glaucoma diagnosis.

OCT – Optical Coherence Tomography

OCT measures the thickness of the retinal nerve fibre layer (RNFL) around the optic nerve. It detects structural damage before visual field loss appears. OCT is one of the most sensitive tools for early glaucoma detection and is essential for monitoring progression over time.

Visual Field Testing (Perimetry)

Perimetry maps the full extent of vision, central and peripheral. It detects and tracks functional loss caused by glaucoma. Serial visual fields over time are the primary tool for assessing whether glaucoma is progressing.

Gonioscopy

Gonioscopy uses a special contact lens to directly examine the drainage angle. It distinguishes open angle from angle closure glaucoma, a critical distinction because the two require different treatment. Gonioscopy is essential in every new glaucoma evaluation.

Pachymetry- Corneal Thickness

Central corneal thickness affects how accurately pressure is measured. A thin cornea causes pressure to be under-read. It is also an independent risk factor for glaucoma progression.

Why Routine Eye Tests Can Miss Glaucoma

Standard eye examinations focus on spectacle power, cataract, and retinal health. They do not routinely include gonioscopy, detailed optic nerve grading, OCT, or serial visual fields. A patient can have early glaucoma, and normal vision, and be told their eyes are completely fine at a routine check.

This is not negligence. It reflects the fact that glaucoma detection requires a dedicated, specialty-level evaluation, not a standard optometry appointment.

How Is Glaucoma Treated?

There is no cure for glaucoma. But treatment works. It lowers eye pressure and protects the optic nerve from further damage. Most patients with early diagnosis and consistent treatment retain good functional vision for life.

The goal of treatment is not to restore lost vision. It is to preserve what remains.

Eye Drops

Pressure-lowering eye drops are the most common first-line treatment. Prostaglandin analogues (latanoprost, bimatoprost, travoprost) are given once daily and are the most widely used. Other classes include beta-blockers, carbonic anhydrase inhibitors, and alpha-agonists. Some patients need combinations.

Drop adherence, using drops correctly and consistently, is the single most important factor in preventing glaucoma progression. Missing doses allows pressure to rise and damage to continue.

SLT Laser: Selective Laser Trabeculoplasty

SLT is a laser treatment that improves drainage from the eye. It is now recognised as a first-line option, equivalent to eye drops, based on the LiGHT trial. SLT is an outpatient procedure. It is repeatable. It reduces the need for long-term drops in many patients.

Laser Peripheral Iridotomy (LPI)

LPI is the primary treatment for narrow angle glaucoma and angle closure risk. A small laser opening in the iris allows fluid to bypass a blocked drainage pathway. It is an outpatient procedure performed under topical anaesthetic.

Trabeculectomy

Trabeculectomy is the gold standard surgical procedure for glaucoma. It creates a new drainage pathway — a small flap in the eye wall — allowing fluid to drain and pressure to fall significantly. It is used when drops and laser cannot achieve adequate pressure control. It is highly effective but requires careful postoperative management.

MIGS: Minimally Invasive Glaucoma Surgery

MIGS procedures improve drainage through very small incisions, with a lower risk profile than trabeculectomy. They are suitable for mild to moderate glaucoma and are often combined with cataract surgery. They offer a meaningful reduction in pressure and drops, but cannot achieve the very low pressures that trabeculectomy provides.

Glaucoma Drainage Implants

In complex or refractory cases, a small silicone tube drains fluid from the eye to a plate on its surface. Tube shunts are used when trabeculectomy has failed or is unlikely to succeed.

Observation

Not all glaucoma requires immediate treatment. In patients with very early disease, low risk of progression, and reliable follow-up, careful monitoring may be the appropriate initial approach. Observation is not inaction, it is structured, evidence-based surveillance.

Why Lifelong Monitoring Is Essential

Glaucoma is a lifelong condition. Controlled glaucoma is not cured glaucoma.

Regular monitoring continues throughout a patient’s life, even when pressure is well controlled and vision is stable. The reason is simple: glaucoma can change. Pressure can rise. Progression can resume. A bleb can scar over. A drop that worked for years can stop working.

Follow-up appointments typically include eye pressure measurement, optic nerve assessment, OCT imaging, and visual field testing. The frequency depends on the severity of disease and rate of progression.

Missing follow-up appointments is the most common reason glaucoma causes preventable vision loss.

When to Seek a Glaucoma Second Opinion

A second opinion in glaucoma is not about distrust. It is about getting clarity on a disease that is often complex, lifelong, and consequential.

Consider a structured second opinion if:

• You have been told you have glaucoma but are uncertain about the diagnosis
• You have been advised surgery and want to understand whether it is the right next step
• Your glaucoma is progressing despite treatment
• Your current treatment plan feels unclear or uncertain
• You want an independent assessment of your pressure targets and monitoring plan

Glaucoma second opinions are particularly valuable before major surgical decisions. The best surgical decision is an informed one.

Does Glaucoma Cause Blindness?

Glaucoma is a leading cause of irreversible blindness worldwide. But for most patients diagnosed early, the answer is no, glaucoma does not cause blindness.

The patients who go blind from glaucoma are almost always those who were diagnosed late, who did not receive appropriate treatment, or who stopped attending follow-up. With early diagnosis, correct treatment, and consistent long-term care, most patients retain functional vision for life.

Glaucoma is not a sentence. It is a manageable chronic disease, when managed.

When to Seek a Glaucoma Evaluation

You should have a dedicated glaucoma evaluation, not just a routine eye test, if:

• You are over 40 and have a first-degree relative with glaucoma
• You have been told your eye pressure is raised or borderline
• Your optic nerve has been described as suspicious
• You have a strong minus or plus spectacle power
• You have diabetes, high blood pressure, or a history of migraines
• You use steroid drops, nasal sprays, or oral steroids long-term
• You have never had a detailed optic nerve assessment
• You have noticed any loss of peripheral vision or other visual changes

Early detection is simple. The consequences of missing it are not.

Frequently Asked Questions About Glaucoma

What causes glaucoma?

Most glaucoma is caused by impaired drainage of fluid from the eye, leading to raised intraocular pressure that damages the optic nerve over time. In normal tension glaucoma, damage occurs despite normal pressure, suggesting blood flow to the nerve and structural vulnerability also play a role. Secondary glaucomas are caused by other eye conditions, medications, or systemic disease.

Is glaucoma hereditary?

Yes. Glaucoma has a strong genetic component. If a parent or sibling has glaucoma, your risk is four to nine times higher than average. Family history glaucoma screening for first-degree relatives is strongly recommended from age 40, or earlier if other risk factors are present.

Can you have glaucoma with normal eye pressure?

Yes. Normal tension glaucoma is a well-recognised condition in which the optic nerve sustains damage despite pressure within the normal range. Normal pressure does not exclude glaucoma. A proper glaucoma evaluation assesses the optic nerve directly, not just the pressure reading.

Can glaucoma be cured?

No. Glaucoma cannot be cured. The vision already lost cannot be restored. But treatment controls the disease effectively in most patients. With early diagnosis and consistent care, most patients retain useful vision throughout their lives.

What is the difference between early and advanced glaucoma?

Early glaucoma involves optic nerve damage that has not yet affected the functional visual field. Vision remains normal. Advanced glaucoma has caused significant peripheral, or in severe cases central, visual field loss. Early glaucoma can be managed to prevent progression. Advanced glaucoma requires treatment to prevent further loss.

What tests are needed to diagnose glaucoma?

A complete glaucoma evaluation includes eye pressure measurement (tonometry), optic nerve examination through dilated pupils, OCT imaging of the retinal nerve fibre layer, visual field testing (perimetry), gonioscopy to examine the drainage angle, and corneal thickness measurement (pachymetry). No single test is sufficient. Diagnosis requires all findings to be interpreted together.

How often should a glaucoma patient be seen?

This depends on the severity of disease, rate of progression, and stability of pressure control. Patients with controlled, stable early glaucoma may be seen every 6–12 months. Those with active progression, recent treatment changes, or advanced disease need more frequent monitoring, sometimes every 1–3 months.

Can glaucoma affect both eyes?

Yes. Glaucoma usually affects both eyes, though often one eye is more severely affected than the other. Each eye is assessed and managed individually. Treatment may differ between the two eyes.

Is surgery always necessary for glaucoma?

No. Most patients are managed successfully with eye drops and/or laser. Surgery is needed when drops and laser cannot achieve adequate pressure control, when disease is progressing despite treatment, or when pressure needs to be lowered significantly and sustainably to protect the optic nerve.

Where can I see a glaucoma specialist in Gurgaon?

Dr Shibal Bhartiya is a fellowship-trained glaucoma specialist and Clinical Director of Ophthalmology at Marengo Asia Hospitals, Sector 56, Gurugram. She offers comprehensive glaucoma evaluations, second opinions, and the full range of glaucoma treatments including laser, trabeculectomy, and MIGS. She is also a Research Collaborator with Mayo Clinic, Florida. Visit drshibalbhartiya.com or call +91 88826 38735.

Glaucoma does not need panic. It needs clarity, consistency, and the right specialist.

Early detection, thoughtful risk assessment, and steady follow-up protect vision over decades. Most patients with glaucoma live full, visually intact lives, when their disease is found early and managed well.

Explore Related Topics

This page is the starting point. Each topic below has its own dedicated guide on this site:

• Open Angle Glaucoma 
• Narrow Angle Glaucoma 
• Ocular Hypertension 
• Glaucoma Surgery in Gurgaon 
• Glaucoma Specialist in Gurgaon 
• Glaucoma Second Opinion 
• Laser or Eye Drops for Glaucoma 
• Can Glaucoma Be Cured? 
• Is My Glaucoma Getting Worse? 

Glaucoma Evaluation in Gurgaon

Diagnosed with narrow angles, angle closure, borderline eye pressure? Advised laser? A second opinion, or a structured glaucoma evaluation can provide:

• An accurate assessment of your actual risk level
• Clarity on whether treatment is necessary at this stage
• A personalised monitoring or management plan

Read the research articles

This article has been written by Dr Shibal Bhartiya, a glaucoma specialist in Gurgaon known for ethical, patient-centred glaucoma care and independent glaucoma second opinions. She is also a research collaborator with Mayo Clinic, Jacksonville, Florida, USA.

She has published peer-reviewed research on glaucoma laser and surgeries, examining how treatment decisions should balance medical evidence, patient preferences, and long-term vision outcomes.

These peer-reviewed articles discussing glaucoma treatment are benchmarks for glaucoma surgeons globally, and can be accessed on PubMed and Google Scholar

Consultation Information

Dr Shibal Bhartiya
Glaucoma Specialist | Neuro-Ophthalmology | Second Opinions

www.drshibalbhartiya.com
+91 88826 38735