Glaucoma is a group of eye diseases that damage the optic nerve, the cable connecting your eye to your brain. It’s one of the leading causes of irreversible blindness worldwide, affecting roughly 80 million people over age 40 as of 2024. The damage typically happens so gradually that most people don’t notice vision loss until the disease is already advanced, which is why glaucoma is often called “the silent thief of sight.”
How Glaucoma Damages Your Vision
Your eye constantly produces a clear fluid that nourishes its internal structures and maintains its shape. Normally, this fluid drains out through a small mesh-like channel near the front of the eye at the same rate it’s produced. When that drainage system doesn’t work properly, fluid builds up and pressure inside the eye rises. The normal range for eye pressure is below 22 mmHg; readings above that level raise concern.
That excess pressure pushes against the optic nerve where it exits the back of the eye, passing through a structure made of tiny collagen beams. This pressure obstructs the flow of nutrients and signals along nerve fibers. Over time, support cells in the nerve become overactivated and release harmful molecules, including free radicals, that injure and eventually kill nerve fibers. As more fibers die, blind spots develop in your visual field. The damage is permanent because optic nerve fibers don’t regenerate.
The Main Types of Glaucoma
Open-Angle Glaucoma
This is by far the most common form, accounting for the vast majority of cases. The drainage angle where fluid exits the eye looks normal and remains open, but the microscopic mesh tissue within that channel becomes clogged or resistant to flow. Think of it like a drain with a filter that slowly gets gunked up. Pressure rises gradually over months or years, and there are no symptoms in the early stages. You lose peripheral (side) vision first, developing patchy blind spots you may not notice because your brain compensates. Central vision is affected only in later stages.
Angle-Closure Glaucoma
In this form, the iris (the colored part of your eye) physically blocks the drainage channel. This can happen suddenly or build up over time. The acute version is a medical emergency: pressure spikes rapidly, causing severe eye pain, a bad headache, nausea, blurred vision, halos around lights, and eye redness. Without prompt treatment, significant vision loss can occur within hours.
Normal-Tension Glaucoma
Some people develop classic optic nerve damage even though their eye pressure never rises above the normal range. This puzzled researchers for years, but current thinking points to two factors. First, the structural support around the optic nerve may be unusually weak in some people, making it vulnerable even at normal pressures. Second, blood flow to the optic nerve may be compromised by vasospasm, a temporary tightening of small blood vessels. People with migraines or Raynaud’s phenomenon (cold-triggered circulation problems in the fingers) appear to be at higher risk. Small hemorrhages on the optic disc, a sign of local blood flow disruption, are more common in this form than in other types.
Who Is Most at Risk
Age is the single strongest risk factor. In a large UK study, glaucoma prevalence was 1.7% among people under 51 but jumped to 7.8% in those 63 and older. Average eye pressure also creeps upward with age, from about 15.2 mmHg in younger adults to 16.7 mmHg in those over 63.
Race plays a significant role. People of African descent have higher eye pressure and higher glaucoma rates in every age category compared to other groups, and they tend to develop the disease earlier. Having a first-degree relative with glaucoma roughly doubles your risk. Researchers have identified specific genes involved, including one called MYOC that, in certain variants, raises eye pressure by 1.6 to 2.7 mmHg depending on age. High myopia (severe nearsightedness) is another growing contributor. Projections estimate that by 2060, about 6 million additional cases of open-angle glaucoma will be linked to the global rise in nearsightedness alone.
How Glaucoma Is Detected
Because the most common type produces no symptoms until significant damage has occurred, screening is essential. The American Academy of Ophthalmology recommends a baseline eye disease screening at age 40, even if your vision seems fine. If you have risk factors like African ancestry, a family history, diabetes, or high myopia, earlier and more frequent exams are appropriate.
A comprehensive glaucoma evaluation involves several tests, none of which are painful:
- Eye pressure check (tonometry): A brief measurement, often using a small puff of air or a gentle probe that touches the surface of your eye after numbing drops. Readings above 22 mmHg warrant further investigation.
- Visual field test: You look into a machine and click a button when you see small lights appear in different spots. This maps your peripheral vision and reveals blind spots you may not be aware of.
- Optic nerve imaging: Specialized cameras photograph and measure the optic nerve head at the back of your eye, looking for thinning, swelling, or unusual cupping.
- Dilated eye exam: Drops widen your pupils so the doctor can directly examine the optic nerve and blood vessels inside the eye.
- Corneal thickness measurement: A thinner-than-average cornea can make pressure readings seem artificially low, potentially masking true risk.
- Angle exam (gonioscopy): A special lens placed on the eye lets the doctor see whether the drainage angle is open or narrow.
Treatment Options
Glaucoma treatment cannot restore lost vision. The goal is to lower eye pressure enough to slow or stop further nerve damage. For most people, treatment begins with prescription eye drops used daily.
Five classes of drops are available, and they work in different ways. Some reduce the amount of fluid the eye produces. Others improve the flow of fluid out of the eye, either through the natural drainage channel or through an alternative pathway in the eye wall. Your doctor may start with one type and add or switch based on how well your pressure responds and whether you experience side effects. Common side effects range from mild eye redness and stinging to dry mouth, fatigue, and occasionally headaches.
When drops alone aren’t enough, laser procedures can help. A quick in-office laser treatment can open up the drainage mesh or create a tiny new pathway for fluid to escape. The procedure takes minutes, and most people return to normal activities the same day.
Surgical Options
For more advanced or hard-to-control glaucoma, surgery creates a new drainage route. Traditional surgery (trabeculectomy) makes a small flap in the white of the eye to allow fluid to drain into a pocket under the eyelid’s lining. It’s effective but requires careful monitoring during recovery.
A newer category called minimally invasive glaucoma surgery (MIGS) uses tiny implants or micro-tools inserted through small incisions. Some of these devices bypass the clogged drainage mesh, others widen the eye’s natural drainage canal, and still others create a new exit path for fluid under the eye’s outer lining. MIGS procedures generally offer faster recovery and fewer complications than traditional surgery, though the pressure reduction is typically more modest. They’re often performed during cataract surgery for people who have both conditions.
For severe cases, drainage implant devices (small tubes connected to a tiny plate) can be placed in the eye to provide a permanent alternate drainage pathway.
Living With Glaucoma
Most people with glaucoma maintain useful vision for life when the disease is caught early and treated consistently. The biggest practical challenge is sticking with daily eye drops that treat a condition you can’t feel. Skipping doses is common, and pressure climbs back up quickly when treatment stops.
Regular follow-up visits, typically every three to six months, allow your eye doctor to track pressure trends and check for new nerve damage using the same tests from your initial evaluation. If your current treatment stops holding pressure at a safe level, the plan gets adjusted. With the global glaucoma burden projected to more than double by 2060, reaching nearly 193 million people, routine screening remains the most powerful tool for catching the disease before it takes vision you can’t get back.