Glaucoma: Why You Can Lose Vision Without Realising It

Glaucoma: Why You Can Lose Vision Without Realising It

Glaucoma is a group of eye conditions that slowly damage the optic nerve, the cable that carries what your eye sees to your brain. It is often called a “silent” threat to vision because the most common type causes no pain and no early warning signs. Side (peripheral) vision fades first, so you can keep reading, watching TV and recognising faces while damage quietly builds up.

Vision lost to glaucoma generally cannot be brought back. But when glaucoma is found early and treated, the damage can often be slowed or controlled, which helps protect the sight you still have. That is why regular eye examinations matter, especially if you are over 40, have a family member with glaucoma, or have conditions such as diabetes or high short-sightedness.

One type is different. Acute angle-closure glaucoma comes on suddenly with severe eye pain, and it is an emergency. Read the symptoms section below so that you know what to do.

What Is Glaucoma?

Each eye makes a clear fluid that continuously flows in and drains out through a tiny channel near the front of the eye. When the fluid drains poorly, pressure inside the eye, called intraocular pressure (IOP), can rise. Over time, this pressure can injure the optic nerve, which is made up of about a million fine nerve fibres. Once these fibres die, they do not grow back.

Eye pressure and glaucoma are linked but they are not the same thing:

•      High eye pressure raises the risk of glaucoma, but it does not mean a person definitely has it. Some people have raised pressure for years without any nerve damage. Doctors call this ocular hypertension and monitor it.

•      Glaucoma can also occur when eye pressure is within the statistically normal range. This is called normal-tension glaucoma, and its causes are less well understood.

Glaucoma is therefore not one disease with one set of symptoms and one treatment. There are several types, and they behave differently.

Why Can Glaucoma Damage Your Vision Without Warning?

In the common open-angle type, the pressure rises slowly and nothing hurts. Several things hide the damage from you:

•      Side vision goes first. The earliest patches of lost vision usually appear at the edges. Central vision, which you use to read and see faces, tends to stay sharp until late.

•      Your brain fills the gaps. The brain blends the images from both eyes and “paints over” small blind spots, so a missing patch in one eye often goes unnoticed.

•      The change is gradual. Slow loss over months or years is much harder to notice than a sudden change.

•      A normal-looking eye proves nothing. Glaucoma does not change how the eye looks, and clear central vision does not rule it out.

Waiting for symptoms can therefore mean waiting until a good deal of vision has been lost permanently. Vision lost from established glaucoma generally cannot be restored, but appropriate treatment can often slow or control further damage.

What Are the Types of Glaucoma?

•      Primary open-angle glaucoma. The most common type. The drainage channel looks open, but fluid drains too slowly. It progresses gradually and is painless.

•      Angle-closure glaucoma. The drainage angle is narrow or blocked, often by the iris. It can build slowly with few symptoms, or suddenly as an emergency (acute angle-closure).

•      Normal-tension glaucoma. Optic nerve damage occurs even though eye pressure measures within the normal range.

•      Secondary glaucoma. Caused by another problem, such as an eye injury, inflammation (uveitis), certain other eye diseases, or long-term steroid use.

•      Congenital glaucoma. Present from birth or early childhood because the drainage system did not develop properly. Signs in babies can include cloudy or enlarged eyes, excess tearing and sensitivity to light.

Symptoms and urgency differ by type, which is why a proper examination is needed to know which kind, if any, a person has.

What Are the Symptoms of Glaucoma?

Open-angle glaucoma often has no early symptoms. Later, symptoms may include:

•      Gradual loss of peripheral (side) vision, often in both eyes though one may be worse

•      Difficulty noticing objects or people to the side, or bumping into things

•      Progressive changes in the visual field, and in advanced cases, tunnel-like vision

By the time these are noticed, a significant amount of nerve damage may have occurred.

Raised pressure in this type can injure the optic nerve within hours to days, so quick treatment matters. Other eye problems, such as inflammation or injury, can cause similar symptoms, so any sudden painful red eye should be examined promptly.

Who Is at Higher Risk of Glaucoma?

Recognised risk factors include:

•      Increasing age, with risk rising from around 40 onwards

•      A family history of glaucoma, especially a parent, brother or sister

•      Higher-than-normal eye pressure

•      Severe short-sightedness (myopia) or long-sightedness, depending on the type

•      Diabetes, high blood pressure, migraine or poor circulation

•      A previous eye injury or certain eye surgery

•      Long-term corticosteroid use, including some steroid eye drops, ointments and tablets

•      Thin corneas or a thin optic nerve rim, which only an examination can show

Some guidance, such as the NHS and Mayo Clinic, also lists Asian, African or Caribbean heritage as a risk factor on average across populations. This does not tell you your own risk. Your individual risk depends on your age, family history, eye measurements and health conditions.

Having a risk factor does not mean you will definitely develop glaucoma, and glaucoma can occur in people with no family history. If you take steroids, please do not stop them yourself; tell your eye doctor so that your eyes can be monitored. Diabetes affects eye health more widely too; see our guide on diabetic retinopathy in Upper Assam.

How Is Glaucoma Diagnosed?

Glaucoma is diagnosed through a comprehensive eye examination. A single eye-pressure reading cannot confirm or rule it out, because glaucoma can occur with normal pressure and high pressure does not always mean glaucoma. Your ophthalmologist decides which tests are needed. They may include:

•      Eye-pressure measurement (tonometry). A quick, painless check of the pressure inside the eye.

•      Optic nerve examination. Looking at the nerve at the back of the eye, usually after the pupil is widened with drops.

•      Visual-field testing (perimetry). You press a button when you see small lights in your side vision, which maps any blind patches.

•      OCT imaging. Optical coherence tomography takes detailed scans of the optic nerve and the nerve fibre layer, and can show thinning, sometimes before vision tests change.

•      Gonioscopy. A special lens is used to look at the drainage angle and see whether it is open or narrow.

•      Corneal thickness (pachymetry). Corneal thickness can affect pressure readings, so it is measured when relevant.

Because glaucoma is a long-term condition, tests are often repeated over time to see whether anything is changing.

Can Glaucoma Be Treated?

Glaucoma cannot usually be cured, but it can be controlled. Treatment aims to lower the risk of further optic nerve damage. It generally cannot restore vision that has already been lost. Common approaches are:

•      Prescription eye drops. Often the first treatment for open-angle glaucoma. They lower pressure by reducing fluid production or helping it drain.

•      Laser treatment. Used for selected patients, for example to improve drainage in open-angle glaucoma or to create a small opening in the iris in some angle-closure cases.

•      Surgery. Considered when drops and laser are not enough, or in advanced or fast-moving glaucoma. Several procedures exist, and the choice depends on the type and stage of glaucoma.

•      Long-term monitoring. Regular follow-up visits and repeat tests check that treatment is working. The interval varies from person to person.

Please use glaucoma drops exactly as prescribed, and do not stop or change them without speaking to your ophthalmologist. Because glaucoma is painless, it is easy to feel that the drops are not doing anything. Missing doses can still allow damage to continue. This article cannot tell any individual which medicine, dose or treatment suits them; that is a decision for your ophthalmologist after examination.

Can Glaucoma Be Prevented?

It helps to separate preventing glaucoma from catching it early. There is no proven way to prevent glaucoma itself, and no single test, lifestyle change or supplement can promise to. What you can do is find it early and protect the vision you have:

•      Have regular eye examinations that suit your individual risk

•      Follow the monitoring schedule your doctor recommends

•      Tell your eye doctor about any family history and all the medicines you take, including steroids

•      Seek urgent care for sudden eye pain, redness, blurred vision or halos

•      If you have been diagnosed, follow your treatment to reduce the risk of further damage

A healthy lifestyle and good control of conditions such as diabetes and blood pressure support overall health, but they should not replace eye examinations.

How Often Should You Get Checked for Glaucoma?

There is no single schedule that suits everyone. How often you need a check depends on your age, family history, previous results and other risk factors. For general guidance, the American Academy of Ophthalmology recommends a complete eye examination around the age of 40, and its published schedule for adults without known problems suggests checks roughly every 2 to 4 years between ages 40 and 54, every 1 to 3 years between 55 and 64, and every 1 to 2 years from 65. The NHS advises an eye test at least every 2 years.

People with risk factors, or a diagnosis of glaucoma, are often advised to have checks more often. Please ask your ophthalmologist what interval is right for you.

Glaucoma Awareness and Eye Care in Dibrugarh and Upper Assam

Glaucoma can affect people anywhere, and living in Dibrugarh or Upper Assam does not by itself decide your risk. What matters is your age, family history, other eye and health conditions, and whether your optic nerve has ever been checked. Because glaucoma is painless, a check-up can easily be put off, and eye care is often sought only when something seems wrong. Awareness efforts such as World Glaucoma Week, observed every March, aim to encourage people to get tested before symptoms appear.

Drishti Netralaya’s glaucoma care page states that eye-pressure screening is available at its Dhemaji and Machkhowa centres, and that laser treatment and surgery are carried out at the main hospital in Dibrugarh.

The same page lists tests such as eye-pressure measurement, OCT, visual-field testing and gonioscopy.

To ask about an examination, you can call +91 6901274500 (also on WhatsApp) or use the contact page. If you have cataract and glaucoma together, your doctor can explain how the two are managed; our cataract surgery page has more on cataract care.

Frequently Asked Questions

Can glaucoma develop without symptoms?

Yes. The most common type, open-angle glaucoma, usually causes no pain and no early symptoms. Side vision is lost slowly, so it often goes unnoticed until damage is advanced.

Can glaucoma cause permanent blindness?

It can. Glaucoma is one of the leading causes of irreversible vision loss. However, when it is found and treated, further damage can often be slowed or controlled, and many people keep useful vision for life.

Does high eye pressure always mean glaucoma?

No. High pressure raises the risk, but some people have raised pressure without nerve damage (ocular hypertension), while others develop glaucoma with normal pressure. A full eye examination is needed.

Can glaucoma be cured?

Usually not. Glaucoma is generally managed rather than cured. Treatment aims to lower the risk of further optic nerve damage.

What is the difference between glaucoma and cataract?

A cataract is a clouding of the eye’s natural lens, and surgery can usually restore clearer vision. Glaucoma is damage to the optic nerve, and lost vision cannot generally be restored. A person can have both.

Who should consider a glaucoma examination?

Adults around the age of 40 and above, and anyone with a family history, diabetes, high short-sightedness, a previous eye injury, long-term steroid use or other risk factors. Your doctor can advise on timing.

What tests are used to diagnose glaucoma?

Eye-pressure measurement, an optic nerve examination, visual-field testing, OCT imaging, gonioscopy and sometimes corneal thickness measurement. The ophthalmologist chooses the tests that are appropriate.

Can glaucoma affect both eyes?

Yes. It often affects both eyes, though one eye may be worse than the other.

Can vision lost to glaucoma return?

Generally no. Treatment aims to protect the vision you still have. That is why early detection matters.

Is glaucoma treatment lifelong?

In most cases, yes. Glaucoma usually needs long-term treatment and regular follow-up, even after laser or surgery. Never stop prescribed drops without your doctor’s advice.

When is glaucoma an emergency?

Sudden severe eye pain, redness, blurred vision or halos, especially with headache, nausea or vomiting, can be acute angle-closure glaucoma. Seek emergency medical care immediately.

Conclusion: Get Your Eyes Checked

Glaucoma can go unnoticed because it usually causes no pain, side vision fades first, and the brain covers for the gaps. Vision that is lost cannot generally be restored, so regular, risk-appropriate eye examinations and consistent follow-up are the best way to protect the sight you have. An eye check cannot promise that no vision will be lost, but it gives the best chance of catching a problem while treatment can still help.

If you or a family member has not had an optic nerve and eye-pressure check, you can contact Drishti Netralaya to enquire about an eye examination. We will be glad to help you find the right next step.