Types of Glaucoma: Open Angle, Closed Angle, Normal Tension, and More, explained by Dr Shibal Bhartiya, glaucoma specialist in Gurgaon.

Glaucoma is not a single disease. It is a family of conditions, each with different causes, risk factors, and treatment approaches. What they share is a common outcome: damage to the optic nerve, leading to progressive and irreversible vision loss if untreated.

Understanding which type of glaucoma you have helps you ask better questions and follow your treatment plan with more confidence. This page explains the main types, from the most common to the less well known, written for patients rather than clinicians.

Dr Shibal Bhartiya is a fellowship-trained glaucoma specialist in Gurgaon with experience diagnosing and managing all types and stages of glaucoma. If you are uncertain about your diagnosis, a structured second opinion can bring clarity.

THE TWO MAIN TYPES OF GLAUCOMA

Q1. What is the difference between open-angle and closed-angle glaucoma?

Most glaucomas fall into one of two broad categories, determined by the anatomy of the drainage angle of the eye.

Open-angle glaucoma is by far the more common type of glaucoma. The drainage angle is open and appears normal, but fluid drains too slowly, causing pressure to build gradually over months and years. It has no symptoms in the early stages. Patients typically lose peripheral vision first, and the brain compensates so well that many people do not notice the loss until the disease is advanced. This is why regular screening is essential, particularly for those with risk factors.

Closed-angle glaucoma occurs when the drainage angle is narrow or blocked, preventing fluid from draining. It can occur suddenly (acute angle closure) or gradually (chronic angle closure). The acute form is a medical emergency with symptoms including severe eye pain, redness, blurred vision, and nausea. The chronic form is subtler and may mimic open-angle glaucoma.

Note: The distinction between the two types of glaucoma (open and closed angle) is made using a test called gonioscopy. This single test shapes all subsequent treatment decisions.

CLOSED-ANGLE GLAUCOMA

Q2. I have been diagnosed with angle-closure glaucoma. What does that mean for me?

In angle-closure glaucoma, the iris (the coloured part of the eye) is too close to the drainage angle, narrowing or blocking it. When the angle closes, fluid cannot drain and eye pressure rises sharply.

The acute form causes a sudden, severe rise in pressure. Symptoms include a red, painful eye with blurred vision, coloured halos around lights, headache, and nausea. This is an eye emergency; seek immediate medical help if this happens.

The chronic form builds more slowly, with few symptoms other than occasional coloured halos and mild headaches. It can go undetected for years without a formal eye examination.

Treatment for angle-closure glaucoma starts with a laser procedure called laser peripheral iridotomy (LPI). This creates a small opening in the iris to provide an alternative drainage pathway. After LPI, some patients require no further treatment; others need long-term eye drops. Your doctor will monitor your pressure and angle anatomy over time.

Note: Family members of patients with angle-closure glaucoma have a higher risk of the same condition. Preventive laser iridotomy can be offered to at-risk relatives before any acute episode occurs.

NORMAL TENSION GLAUCOMA

Q3. My doctor says I have glaucoma, but my eye pressures are normal. How is that possible?

This is understandably confusing. Between 10 and 25 percent of people with glaucoma have eye pressures that fall within the normal range (below 21 mmHg). This is called normal tension glaucoma (NTG), or low tension glaucoma.

The exact cause is not fully understood. Two leading theories are that the optic nerve is unusually sensitive to pressure and sustains damage even at pressures that would be harmless in most people, or that the blood supply to the optic nerve is compromised, making it vulnerable to damage independent of pressure. Of all the types of glaucoma, this is perhaps the most confusing for patients.

Conditions associated with normal tension glaucoma include:

• Japanese ancestry (NTG is significantly more common in East Asian populations)
• A family history of normal tension glaucoma
• Migraines and vasospastic disorders such as Raynaud’s disease
• Sleep apnoea
• Alzheimer’s disease

Treatment still focuses on lowering eye pressure, like all other types of glaucoma. Even when eye pressure is within the normal range to start with, clinical trials have shown this slows progression. Eye drops, laser, or surgery may be used depending on the rate of progression and individual risk factors.

Note: Normal tension glaucoma often progresses more slowly than high-pressure glaucoma, but regular monitoring is still essential. Missing follow-up appointments is the most common reason for avoidable vision loss.

OCULAR HYPERTENSION

Q4. My eye pressures are high but my doctor says I do not have glaucoma. What is ocular hypertension?

If your eye pressure is above the normal range but your optic nerve and visual field show no signs of damage, you have ocular hypertension (OHT). It is not glaucoma, but it is a significant risk factor for developing glaucoma.

Not everyone with high eye pressure will develop glaucoma. Your individual risk depends on your age, ethnicity, family history, and corneal thickness (thicker corneas can give falsely high pressure readings).

Your doctor will weigh your risk profile before deciding whether to treat. Options include eye drops or selective laser trabeculoplasty (SLT). In lower-risk patients, careful monitoring without treatment is often appropriate, since all glaucoma medications carry some side effect burden.

Whether or not you receive treatment, regular eye checks are essential. The goal is to detect any optic nerve or visual field changes before significant vision is lost.

GLAUCOMA SUSPECT

Q5. My doctor says I am a glaucoma suspect. My tests were normal. Why do I still need annual monitoring?

A glaucoma suspect is someone whose optic nerve appearance raises concern, even when eye pressure and visual field tests are currently normal.

The most common reason is a larger than average cup-to-disc ratio (the proportion of the optic nerve head occupied by the central cup). A ratio above 0.5, or a difference of 20 percent or more between the two eyes, warrants closer monitoring. Other reasons include borderline eye pressures or a strong family history of glaucoma.

This does not mean you have glaucoma. It means your doctor wants a baseline record to compare against over time. If the optic nerve or visual field changes, that change can be detected early and treatment started before significant vision is lost.

Most glaucoma suspects are asked to return for annual or biannual testing. Once several years of stable results have been recorded, the interval between visits may be extended.

Note: The value of being labelled a glaucoma suspect is that it keeps you in the system. Early detection is the single most powerful tool for preventing glaucoma blindness.

SECONDARY GLAUCOMA

Q6. What is secondary glaucoma, and what causes it?

Secondary glaucoma is glaucoma caused by another identifiable condition or event, rather than arising on its own. It is managed in the same way as primary glaucoma (eye drops, laser, or surgery), but the underlying cause must also be addressed.

The most common secondary types of glaucoma include:

• Pseudoexfoliation glaucoma: A protein-like material deposits on the lens and drainage structures of the eye, blocking outflow. This is one of the most common secondary glaucomas in India and tends to cause higher pressures and faster progression than primary open-angle glaucoma. It requires close monitoring and often more aggressive treatment.
• Pigmentary glaucoma: Pigment granules shed from the back of the iris clog the drainage angle. It typically affects younger, myopic (short-sighted) patients and is often missed because these patients are not in the standard high-risk age group for glaucoma screening.
• Steroid-induced glaucoma: Long-term use of steroid eye drops, nasal sprays, skin creams, or oral steroids can raise eye pressure in susceptible individuals. If you are on any form of steroid medication for any condition, ask your doctor whether your eye pressure has been checked.
• Traumatic glaucoma: An injury to the eye can damage the drainage angle and cause pressure to rise, sometimes years after the original injury. Any history of significant eye trauma should be disclosed to your eye doctor.
• Neovascular glaucoma: New, abnormal blood vessels grow over the drainage angle, blocking outflow. It is most commonly associated with poorly controlled diabetes and retinal vein occlusion. It is one of the more difficult types to manage and often requires surgery.

Note: If you have a systemic condition such as diabetes, or are on long-term steroid medication, make sure your eye doctor is aware. These are glaucoma risk factors that are often overlooked.

CONGENITAL AND CHILDHOOD GLAUCOMA

Q7. My child has been diagnosed with glaucoma. How is that possible, and what should I expect?

Glaucoma can affect any age group, though it is most common in adults over 40. In children, the most common cause is a structural defect in the drainage angle that is present from birth; this is called congenital glaucoma or primary infantile glaucoma.

Signs that parents typically notice first include:

• Cloudy or hazy eyes
• Unusual sensitivity to light; the child may turn away from bright light or bury their face
• Excessive tearing
• Eyes that appear larger than normal (because raised pressure causes the infant eye to expand)

Eye drops may be started initially to control pressure, but surgery is almost always required for congenital glaucoma. Early surgical intervention gives the best chance of preserving good vision throughout the child’s life.

Some children also have a co-existing cataract or other eye abnormality that needs to be managed alongside the glaucoma. Glasses, patching therapy for amblyopia (lazy eye), and follow-up surgeries may all be part of the long-term plan.

Children with glaucoma can lead fully independent lives. Even where some vision has been lost, tailored rehabilitation and visual aids allow children to participate in all age-appropriate activities. As a parent, remaining engaged with the care team and encouraging the child’s independence are the most important things you can do.

Note: Congenital glaucoma is rare. If your child has been diagnosed, seek care from a specialist with specific paediatric glaucoma experience. Early and consistent follow-up is critical.

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 article discussing glaucoma treatment are benchmarks for glaucoma surgeons globally, and can be accessed on PubMed and Google Scholar

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