Primary open angle glaucoma (POAG) is the most common form of glaucoma in the world. It affects millions of people. Most of them do not know they have it.
That is the central problem with this disease. It causes no pain. It gives no warning. Vision loss begins at the edges, so slowly that patients rarely notice. By the time symptoms appear, significant damage has already occurred.
This article explains what open angle glaucoma is, who is at risk, what early symptoms to look for, and what treatment involves. It is written to help patients understand their diagnosis — and to help those at risk know when to act.
Key Facts at a Glance
- Open angle glaucoma is the most common type of glaucoma.
- It causes no pain and no early symptoms.
- Vision loss starts at the periphery and is irreversible.
- Early detection through regular screening is the only reliable protection.
- Treatment controls the disease. It does not cure it.
- Most patients retain good vision with early diagnosis and consistent care.
What Is Open Angle Glaucoma?
Glaucoma is a disease of the optic nerve. The optic nerve carries visual signals from the eye to the brain. When it is damaged, those signals are lost, permanently.
Open angle glaucoma is the most common form. In this type, the drainage angle of the eye, the channel through which fluid exits, remains open. But the drainage system works too slowly. Fluid builds up. Pressure rises. Over time, that pressure damages the optic nerve.
It is called “open angle” to distinguish it from angle closure glaucoma, where the drainage channel is physically blocked. In open angle glaucoma, the block is microscopic, within the drainage tissue itself.
Open angle glaucoma is also called primary open angle glaucoma, or POAG.
Why Open Angle Glaucoma Is Called the Silent Thief of Sight
Open angle glaucoma earns this name for a specific reason. The optic nerve has a large reserve. It can lose up to 40% of its fibres before central vision is affected.
The first areas of vision to be lost are peripheral, the edges of your visual field. Most people do not notice this loss. The brain compensates. The remaining eye fills in gaps.
By the time a patient notices blurring, blind spots, or tunnel vision, the disease is usually advanced.
This is why screening matters more than symptom awareness in glaucoma. Waiting for symptoms means waiting too long.
Early Glaucoma Symptoms: What to Look For
In the early stages, most patients have no symptoms at all. This is normal. It does not mean the disease is not progressing.
As the disease progresses, some patients notice:
- Gradual loss of side vision
- Small blind spots in the visual field
- Blurred vision
- Halos around lights, especially at night
- Difficulty adjusting from bright to dark environments
- Frequent changes in spectacle prescription
In advanced disease:
- Significant loss of peripheral vision
- Tunnel vision
- Difficulty reading or driving
These symptoms rarely appear early. If you notice them, see a glaucoma specialist promptly. Do not wait for your next routine check.
Who Is at Risk of Open Angle Glaucoma?
Anyone can develop open angle glaucoma. But some people carry a higher risk:
Age
Risk rises sharply after 40. After 60, the risk is significantly higher. Adults over 40 with any additional risk factor should have a dedicated glaucoma evaluation.
Family History of Glaucoma
Glaucoma is hereditary. If a parent or sibling has glaucoma, your risk is four to nine times higher than average. Family history is one of the strongest predictors of who will develop the disease. Regular glaucoma screening for first-degree relatives is essential.
Raised Eye Pressure
High intraocular pressure is the most important modifiable risk factor. But it does not tell the whole story. Some patients develop glaucoma with normal pressure (normal tension glaucoma). Others have raised pressure without glaucoma (ocular hypertension). Pressure alone does not confirm or exclude the disease.
Ethnicity
Open angle glaucoma is more common and more severe in people of African origin. It also tends to appear at a younger age in this group. People of South Asian origin have a higher-than-average risk of angle closure glaucoma.
Myopia (Minus Spectacle Power)
People with a high minus prescription are at increased risk of open angle glaucoma. The structural shape of a myopic eye places additional stress on the optic nerve.
Thin Central Cornea
A thin cornea is associated with higher glaucoma risk. It also affects how accurately eye pressure is measured. Pachymetry, corneal thickness measurement, is an important part of glaucoma risk assessment.
Diabetes and Cardiovascular Disease
Both conditions affect blood flow to the optic nerve. They increase glaucoma risk and can accelerate progression.
How Is Open Angle Glaucoma Diagnosed?
No single test diagnoses glaucoma. Diagnosis requires a combination of assessments. A glaucoma specialist uses all findings together to reach a conclusion.
Eye Pressure Measurement (Tonometry)
Intraocular pressure (IOP) is measured at every glaucoma appointment. Normal pressure is between 10 and 21 mmHg. But normal pressure does not rule out glaucoma, and raised pressure does not confirm it. Pressure readings must be interpreted in context.
Optic Nerve Examination
The optic nerve is examined directly through a dilated pupil. Signs of glaucomatous damage include increased cupping, notching of the neuroretinal rim, and disc haemorrhages. This is a critical part of every glaucoma evaluation.
OCT (Optical Coherence Tomography)
OCT measures the thickness of the retinal nerve fibre layer around the optic nerve. It detects structural changes before visual field loss appears. OCT is one of the most sensitive tools for early glaucoma detection.
Visual Field Testing (Perimetry)
Visual field testing maps the full extent of a patient’s vision. It detects and tracks loss of peripheral vision. It is the primary tool for monitoring glaucoma progression over time.
Gonioscopy
Gonioscopy uses a contact lens to examine the drainage angle directly. In open angle glaucoma, the angle is open. This examination distinguishes open angle from angle closure disease, which requires different management.
Pachymetry (Corneal Thickness)
Corneal thickness affects pressure readings and independently influences risk. A thin cornea is a risk factor for glaucoma progression even when pressure appears normal.
How Is Open Angle 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 open angle glaucoma retain good functional vision throughout their lives with appropriate care.
The goal of treatment is not to restore lost vision. It is to preserve what remains.
Eye Drops
Pressure-lowering eye drops are usually the first treatment. Prostaglandin analogues (such as latanoprost and bimatoprost) are the most commonly used. They are given once a day, usually at night. Beta-blockers, carbonic anhydrase inhibitors, and alpha-agonists are other options. Some patients need multiple eye drops or a combination.
Eye drops work only if they are used correctly and consistently. Drop adherence is the single most important factor in preventing glaucoma progression.
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, not just an alternative to drops. The LiGHT trial showed that SLT first is safe, effective, and reduces the need for long-term drop use. It is an outpatient procedure that takes a few minutes.
Trabeculectomy (Glaucoma Filtration Surgery)
When drops and laser do not control pressure adequately, surgery may be needed. Trabeculectomy creates a new drainage pathway for fluid to exit the eye. It is highly effective at lowering pressure. It requires careful post-operative care and follow-up.
MIGS (Minimally Invasive Glaucoma Surgery)
MIGS procedures use microscopic instruments to improve drainage. They offer a lower risk profile than trabeculectomy. They are often combined with cataract surgery in patients who need both. MIGS is suitable for mild to moderate glaucoma.
Glaucoma Drainage Implants (Tube Shunts)
In complex or refractory cases, a small tube is implanted to drain fluid from the eye. This is used when other surgical options have failed or are not suitable.
What If Glaucoma Progresses Despite Treatment?
Some patients find their glaucoma progresses despite using drops correctly. This is one of the most distressing experiences a glaucoma patient can face.
If your glaucoma is progressing despite treatment, there are several reasons this may be happening:
- Your target eye pressure may need to be lower than currently achieved
- Your optic nerve may be particularly sensitive to pressure
- Blood flow factors may be contributing alongside pressure
- Your current drops may not be the most effective choice for your eye
In this situation, a structured glaucoma second opinion can bring significant value. A fresh assessment of your pressure targets, imaging, and treatment history can change the course of management.
Why Lifelong Monitoring Matters
Glaucoma is a lifelong condition. Even well-controlled glaucoma requires regular monitoring.
Follow-up appointments typically include:
- Eye pressure measurement
- Optic nerve assessment
- OCT imaging of the nerve fibre layer
- Visual field testing
- Review of drop technique and adherence
Missing follow-up appointments is the most common reason glaucoma causes preventable vision loss. Consistent, long-term care is the foundation of a good outcome.
When to Seek a Glaucoma Evaluation or Second Opinion
You should see a glaucoma specialist if:
- You are over 40 and have not had a glaucoma evaluation
- A parent or sibling has glaucoma — family history glaucoma screening is essential
- You have been told your eye pressure is raised
- You have a strong minus spectacle number
- You have diabetes or a history of cardiovascular disease
- You have noticed any loss of peripheral vision or other visual changes
- Your glaucoma is progressing despite drops and you want a second opinion
- You are unsure whether your current treatment plan is optimal
Detecting open angle glaucoma early is the most important step. Early diagnosis, correct treatment, and consistent follow-up prevent most cases of glaucoma-related vision loss.
Frequently Asked Questions
Is open angle glaucoma the same as POAG?
Yes. POAG stands for primary open angle glaucoma. It is the most common form of glaucoma. ‘Primary’ means there is no underlying disease causing it — it develops on its own.
Can you have open angle glaucoma with normal eye pressure?
Yes. This is called normal tension glaucoma. About a third of open angle glaucoma patients have pressure within the normal range. Eye pressure is important but it is not the only factor that determines glaucoma risk.
Is open angle glaucoma hereditary?
Yes. Glaucoma runs strongly in families. First-degree relatives of a glaucoma patient have a four to nine times higher risk of developing the disease. If a parent or sibling has glaucoma, you need regular glaucoma screening — not just a routine eye test.
Can glaucoma be cured?
No. Glaucoma cannot be cured. Any vision lost to glaucoma is permanent. But treatment controls the disease effectively in most patients. With early diagnosis and consistent care, most patients retain useful vision for life.
What is the difference between open angle and closed angle glaucoma?
In open angle glaucoma, the drainage angle of the eye is open but drains too slowly. In angle closure glaucoma, the drainage angle becomes blocked. They have different risk factors, presentations, and treatments. A glaucoma specialist can distinguish between them using gonioscopy.
How quickly does open angle glaucoma progress?
Open angle glaucoma usually progresses slowly — over years or decades. But rate of progression varies between patients. Some progress slowly even without treatment. Others progress faster, especially at higher pressures or with a thin cornea. This is why regular monitoring matters even in patients with well-controlled pressure.
Can lifestyle changes help glaucoma?
Lifestyle changes do not replace treatment. But regular moderate exercise, avoiding inverted head positions, and reducing caffeine intake may have modest effects on eye pressure. Sleep position and stress can also affect pressure. Discuss specific activities with your glaucoma specialist.
Where can I see a glaucoma specialist in Gurgaon for open angle glaucoma?
Dr Shibal Bhartiya is a fellowship-trained glaucoma specialist and Clinical Director of Ophthalmology at Marengo Asia Hospitals, Sector 56, Gurugram. She offers comprehensive evaluation for open angle glaucoma, ocular hypertension, and glaucoma suspects, as well as structured second opinions for patients whose glaucoma is progressing despite treatment. Visit drshibalbhartiya.com or call +91 88826 38735.
Open angle glaucoma causes no symptoms until it is advanced. By then, the damage is done. The best protection is a proactive evaluation — not waiting for a sign that something is wrong.
Screening is simple. The risk of missing it is not.
Open Angle Glaucoma Evaluation in Gurgaon
If you have been diagnosed with open angle glaucoma, ocular hypertension, or glaucoma suspect — or if you have a family history of glaucoma — a dedicated glaucoma evaluation provides:
- Accurate risk assessment with OCT, visual fields, and gonioscopy
- A clear explanation of your results
- A personalised treatment or monitoring plan
- A structured second opinion if your glaucoma is progressing despite treatment
Read the research articles
This article has been written by Dr Shibal Bhartiya, a fellowship-trained 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 here on PubMed and Google Scholar
Consultation Information
Dr Shibal Bhartiya
Glaucoma Specialist | Neuro-Ophthalmology | Second Opinions
www.drshibalbhartiya.com
+91 88826 38735