What Is Glaucoma? Symptoms, Causes, Testing and Treatment.

Glaucoma is often called “the silent thief of sight.” The most common type doesn’t hurt and doesn’t blur your vision at first. It slowly damages the optic nerve while your eyesight seems perfectly normal. By the time many people notice a change, some of their side vision is already gone — and vision lost to glaucoma doesn’t come back.

Here’s the other side of that: glaucoma can be found early with a regular eye exam, long before you’d notice anything. And treatment can often stop the damage and protect the vision you have.

This guide explains what glaucoma is, who’s most at risk, how it’s tested, and how it’s treated. If you’re over 40, have family with glaucoma, or haven’t had a full eye exam in a while, it’s worth a few minutes.

Key Takeaways

• Glaucoma damages the optic nerve. It’s often, but not always, linked to high pressure inside the eye.
• The most common type (open-angle glaucoma) has no early symptoms and no pain.
• Vision lost to glaucoma can’t be restored. Treatment aims to slow or stop more loss.
• Risk goes up with age, family history, diabetes, and for some groups of people (listed below).
• Treatment includes eye drops, laser and surgery, all meant to lower eye pressure.
• A regular, full eye exam is the only reliable way to catch glaucoma early.

What Is Glaucoma?

At the back of your eye is the optic nerve. Think of it as the cable that carries pictures from your eye to your brain. Glaucoma is a group of conditions that damage this nerve, usually a little at a time. As the nerve is damaged, you lose vision — usually starting with your side (peripheral) vision and slowly moving inward.

Most cases are tied to pressure inside the eye. Your eye is always making a clear fluid, and that fluid drains out through a tiny channel. If the drain doesn’t work well, fluid backs up and pressure rises, pressing on the optic nerve. Think of a sink with a slow drain — the water level keeps climbing.

One important detail: not everyone with glaucoma has high eye pressure, and not everyone with high eye pressure gets glaucoma. Some people get nerve damage even when their pressure is normal. That’s why a real diagnosis looks at the nerve and your vision, not just a pressure number.

What Are the Main Types of Glaucoma?

Open-angle glaucoma (the most common)

The eye’s drain stays open, but fluid drains too slowly over time, so pressure rises little by little. There’s no pain and no early symptoms. Damage builds quietly over years, which is why regular exams matter so much.

Angle-closure glaucoma (less common, can be sudden)

The drain gets blocked and eye pressure can rise fast. A sudden attack is a medical emergency. Signs include severe eye pain, headache, nausea, blurry vision, halos or rainbow rings around lights, and a red eye. This type you feel — and it needs care right away.

There are other types too, including normal-tension glaucoma (nerve damage with normal eye pressure) and glaucoma caused by an eye injury, other eye conditions or some medicines. Your eye doctor will tell you which type you have.

What Causes Glaucoma, and Who Is at Risk?

Glaucoma happens when the optic nerve gets damaged. Often this is linked to pressure building up inside the eye, when fluid doesn’t drain the way it should. But glaucoma can also happen when eye pressure is normal, and doctors don’t fully know why.

Anyone can get glaucoma, but the National Eye Institute says you’re at higher risk if you:

• Are over age 60, especially if you’re Hispanic or Latino
• Are African American and over age 40
• Have a family history of glaucoma

Other things that raise your risk:

• High pressure inside your eye
• Diabetes, high blood pressure or heart disease
• Being very nearsighted or farsighted
• An eye injury in the past
• Using steroid medicines for a long time
• Asian background, for the angle-closure type

If several of these fit you, don’t wait for symptoms. Ask your eye doctor how often you should be checked.

What Are the Early Signs of Glaucoma?

For the most common type, there usually aren’t any. No pain, no blur, no redness. Your vision seems normal while side vision is slowly lost. Because both eyes are usually affected and your brain fills in the gaps, many people don’t notice until the damage is well along.

As open-angle glaucoma gets worse, you may notice:

• Patchy blind spots in your side vision
• Tunnel vision in later stages
• Trouble seeing in dim light

How Is Glaucoma Tested?

Because early glaucoma has no signs, it’s found during a full (comprehensive) eye exam. No single test tells the whole story, so the doctor looks at several:

• Eye pressure test (tonometry). Measures the pressure inside your eye. Most ophthalmologists use numbing drops and a device that gently touches the front of your eye. It takes just seconds.
• Optic nerve check. The doctor looks directly at the nerve, usually after drops widen your pupils.
• OCT scan. A quick scan, a bit like a detailed photo, that shows the layers of the optic nerve. It can show thinning before you’d notice any change.
• Visual field test. Maps your side vision to find blind spots you may not know about. It’s also used to track glaucoma over time.
• Gonioscopy. A special lens lets the doctor see the eye’s drain and tell whether it’s open or closed.
• Pachymetry. Measures how thick your cornea (the clear front window of your eye) is, since that affects pressure readings.

How Is Glaucoma Treated?

Treatment can’t bring back vision that’s already lost. Its job is to lower eye pressure and protect the vision you have.

Eye drops

Prescription eye drops are usually the first step. They lower eye pressure by helping fluid drain or by making less of it. Drops only work if you use them exactly as prescribed, every day — even when your eyes feel fine. Skipping doses is one of the biggest reasons glaucoma gets worse.

Laser treatment

Some laser treatments lower pressure, often in a short office visit. For open-angle glaucoma, laser can help fluid drain. For angle-closure, it can open or prevent a blockage. Laser may be used first or along with drops.

Surgery

When drops and laser aren’t enough, surgery can make a new path for fluid to drain or place a tiny device to help it drain. Your eye doctor will explain which option fits your eyes and, if needed, who performs it.

Can You Prevent Glaucoma?

You can’t fully prevent it, but you can give yourself the best chance to protect your sight. Most of it comes down to finding it early and sticking with treatment.

• Get regular full eye exams. This is the most important step, especially if you’re over 40 or have risk factors.
• Know your family history, and tell your eye doctor.
• If you’re diagnosed, use your drops exactly as prescribed. Phone reminders help.
• Take care of your overall health — including diabetes and blood pressure.
• Protect your eyes from injury, and use steroid medicines only with a doctor watching.

When Should You See an Eye Doctor?

If you’re over 40, have family with glaucoma, or are in a higher-risk group, schedule a full eye exam even if your vision seems perfect. That’s exactly when glaucoma is easiest to miss and best to catch. The National Eye Institute says people at higher risk need a comprehensive dilated eye exam every 1 to 2 years. Your eye doctor will tell you how often you should come in.

Treat sudden severe eye pain, headache, nausea, blurry vision and halos around lights as an emergency. Get care right away.

Living With Glaucoma

Glaucoma is something you manage over time, a bit like high blood pressure — a steady routine, not a crisis.

The key is sticking with it. Keep every follow-up visit so your doctor can check that your pressure is controlled and your vision is stable. Never stop your drops just because you feel fine — feeling fine isn’t the same as being under control.

If you’ve lost some side vision, better lighting, low-vision tools and a few changes at home can help you stay safe and independent, especially with driving and stairs. And because glaucoma runs in families, encourage your relatives to get checked too.

Frequently Asked Questions

What are the early signs of glaucoma?

For the most common type, there usually aren’t any. It doesn’t hurt and doesn’t blur your vision at first. Side vision is lost slowly, and most people don’t notice until later. That’s why a regular eye exam matters more than how your eyes feel.

What is normal eye pressure?

The American Academy of Ophthalmology says normal eye pressure is generally between 10 and 21 mmHg (the unit used to measure it). But a normal number doesn’t rule out glaucoma — some people have nerve damage at normal pressure, and some have higher pressure with no damage. Your doctor decides what’s healthy for your eyes.

What happens during a glaucoma test?

It’s part of a full eye exam. You’ll get numbing drops, and a small device gently touches the front of your eye for a few seconds to measure pressure. The doctor also checks your optic nerve, often after drops widen your pupils, and may do a scan or a side-vision test.

What does glaucoma look like?

At first, most people notice nothing at all. Over time, glaucoma usually takes side (peripheral) vision first, so it can start to feel like looking through a tunnel. Center vision often stays clear until later, which is why many people don’t notice until damage is done. Angle-closure glaucoma is different: it can come on fast with eye pain, a bad headache, blurry vision and halos around lights. That needs care right away.

Can glaucoma be cured?

No. But early treatment can often stop the damage and protect your vision. Vision that’s already lost can’t be restored, which is why finding it early matters so much.

Can you go blind from glaucoma?

Glaucoma can cause vision loss and blindness if it isn’t found and treated. Finding it early and sticking with treatment is the best way to protect your sight.

Is glaucoma hereditary?

Family history is one of the strongest risk factors. If a parent, brother or sister has glaucoma, tell your eye doctor. You may need to be checked earlier and more often.

Does diabetes raise your risk of glaucoma?

Diabetes is linked to a higher risk of glaucoma. People with diabetes already need a yearly dilated eye exam to check for diabetic eye disease — that same visit is a good time to check for glaucoma.

Do I have to use glaucoma eye drops forever?

For most people, yes. The drops only work while you’re using them, and skipping doses lets pressure creep back up. If drops are hard for you to use, talk to your doctor about other options instead of stopping.

Can you have glaucoma in just one eye?

Yes, it can start in one eye or be worse in one eye. It often affects both eyes over time, which is why your doctor checks both.

How often should I get checked for glaucoma?

It depends on your age and risk. People at higher risk need a comprehensive dilated eye exam every 1 to 2 years, according to the National Eye Institute. Your eye doctor will set a schedule that fits you.

Get Checked for Glaucoma Close to Home

Glaucoma works quietly, which is why the exam matters more than how your eyes feel. Dr. James Powers and our team check for glaucoma at our St. Petersburg, Clearwater and New Port Richey offices, and we check your insurance before your visit.

• New Port Richey — 5413 US Highway 19, New Port Richey, FL 34652
• Clearwater — 2565 Enterprise Rd, Clearwater, FL 33763
• St. Petersburg — 603 7th St S, St. Petersburg, FL 33701

More guides: Cataracts · Macular degeneration · Dry eye · Parts of the eye

Sources: National Eye Institute, “Glaucoma” (nei.nih.gov); American Academy of Ophthalmology, “Eye Pressure Testing” and “Eye Pressure” (aao.org).

This article is general information, not medical advice for your eyes. For advice about your own eyes, call us or see your eye doctor.