Glaucoma is a group of eye diseases that progressively damage the optic nerve, the cable of nerve fibers that carries visual information from your eye to your brain. It affects over 80 million people worldwide and is one of the leading causes of irreversible blindness. 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. This fluid drains out through a mesh-like channel where the iris meets the cornea. When that drainage system doesn’t work properly, fluid builds up and pressure inside the eye rises. Normal eye pressure falls between 10 and 20 millimeters of mercury (mmHg). When pressure climbs above that range, it can start compressing the nerve fibers at the back of the eye where they bundle together to form the optic nerve.
There are two leading explanations for how elevated pressure causes damage. One is mechanical: the pressure physically crushes nerve fibers as they pass through a sieve-like structure at the back of the eye. The other is vascular: high pressure reduces blood flow to the optic nerve, starving it of oxygen. Both mechanisms likely contribute in most cases. Once those nerve fibers die, they don’t regenerate, and the vision they carried is permanently lost.
Glaucoma typically destroys peripheral vision first. You lose the edges of your visual field so gradually that your brain compensates, and you may not realize anything is wrong until a significant portion of your sight is gone. Central vision, the sharp focus you use for reading and recognizing faces, is usually the last to go.
Types of Glaucoma
Open-angle glaucoma is by far the most common form, affecting roughly 53 million people globally as of recent estimates. In this type, the drainage channels in the eye look structurally open but become increasingly inefficient over time, like a slow-clogging drain. Pressure rises gradually over months or years, and there are no early symptoms. Most people discover it during a routine eye exam.
Angle-closure glaucoma is less common but far more dramatic. The iris physically blocks the drainage angle, causing a sudden spike in eye pressure. This can trigger severe eye pain, headache, nausea, blurred vision, and halos around lights. Acute angle-closure glaucoma is a medical emergency. Without treatment within hours, it can cause permanent vision loss.
There are also less common variants. Normal-tension glaucoma damages the optic nerve even though eye pressure stays within the typical range, suggesting that some optic nerves are simply more vulnerable to pressure or that blood flow problems play a larger role. Secondary glaucoma develops as a complication of another condition, injury, or medication. And congenital glaucoma is present from birth, caused by abnormal development of the eye’s drainage system.
Who Is Most at Risk
Age is the single strongest risk factor. Your risk roughly doubles with each decade of life, and the highest number of cases occurs in people between 70 and 79. Having a first-degree relative (parent, sibling, or child) with glaucoma nearly doubles your odds as well. Research from the Los Angeles Latino Eye Study found that a positive family history increased risk by about 92%.
Race and ethnicity also matter. People of African descent develop glaucoma earlier and more severely. Hispanic and Latino populations face elevated risk as age increases, and Native American ancestry has been linked to higher rates of elevated eye pressure. High myopia (severe nearsightedness) is an emerging concern: projections estimate that by 2060, around 6 million cases of early-onset glaucoma may appear in people aged 20 to 39 due to increasing rates of myopia worldwide. Other risk factors include diabetes, previous eye injuries, and long-term corticosteroid use.
How Glaucoma Is Diagnosed
A comprehensive glaucoma evaluation involves several tests, none of which are painful. The most familiar is the eye pressure check, or tonometry, often done with a brief puff of air or a gentle probe that touches the numbed surface of your eye. But pressure alone isn’t enough to diagnose glaucoma, because some people develop nerve damage at normal pressures while others tolerate high pressures without harm.
During a dilated eye exam, your doctor examines the optic nerve directly for signs of damage, looking for characteristic changes in its shape and color. Optic nerve imaging uses a machine that photographs each layer of tissue at the back of your eye. You simply rest your chin on the device and look into a lens while it captures detailed cross-sectional images over a minute or two. These scans can detect thinning of the nerve fiber layer before you notice any vision changes.
A visual field test maps your peripheral and central vision by having you click a button each time you see a small light flash in different parts of your field of view. This test reveals blind spots you may not be aware of and, when repeated over time, shows whether the disease is progressing. Your doctor may also measure corneal thickness, since thinner corneas can cause pressure readings to appear misleadingly low, and examine the drainage angle with a special lens to determine which type of glaucoma you have.
Treatment With Eye Drops
The goal of all glaucoma treatment is the same: lower eye pressure enough to stop or slow further nerve damage. Eye drops are the most common first-line treatment. Several classes of drops work in different ways.
Prostaglandin analogs are often prescribed first. They lower pressure by improving the eye’s natural drainage pathways, helping fluid exit the eye more efficiently. They’re typically used once daily at bedtime and are generally well tolerated, though they can gradually darken the color of your iris and thicken your eyelashes over time.
Beta-blockers reduce how much fluid your eye produces in the first place. They can cause stinging after application and, because a small amount enters your bloodstream, may occasionally affect heart rate or breathing. Alpha agonists work through a dual mechanism, both reducing fluid production and improving drainage. Their side effects are broader and can include red or itchy eyes, dry mouth, fatigue, and dizziness. A fourth class, carbonic anhydrase inhibitors, also slows fluid production and can cause stinging on application.
Most people use one type of drop, but some need a combination of two or three to reach their target pressure. The biggest challenge with eye drops isn’t effectiveness but consistency. Using them every single day, often for the rest of your life, is harder than it sounds. Missed doses allow pressure to creep back up, and the disease can quietly advance.
Laser Treatment
Selective laser trabeculoplasty (SLT) has become a major option for open-angle glaucoma, sometimes used as the very first treatment instead of eye drops. During the procedure, a low-energy laser targets the eye’s drainage tissue to help it work more efficiently. It’s performed in a clinic, takes a few minutes, and requires no incision.
The results are encouraging. In a major study, nearly 75% of eyes treated with SLT achieved good disease control without needing daily eye drops over a 36-month follow-up period. About 58% reached that result from a single treatment session. If the effect fades over time, the procedure can often be repeated. For people who struggle with daily eye drops or experience significant side effects, laser treatment offers a practical alternative with a strong track record.
For angle-closure glaucoma, a different laser procedure called a laser peripheral iridotomy creates a tiny hole in the iris, allowing fluid to flow more freely and preventing the drainage angle from being blocked.
Surgery for Advanced Cases
When medications and laser treatment aren’t enough to control pressure, surgery becomes necessary. Trabeculectomy has long been the standard. The surgeon creates a small flap in the white of the eye to form a new drainage channel, allowing excess fluid to collect in a small blister-like pocket under the eyelid, where the body absorbs it. It’s effective at lowering pressure substantially but requires a recovery period and careful follow-up to ensure the new channel heals properly without scarring shut.
Minimally invasive glaucoma surgeries, collectively known as MIGS, are a newer category of procedures that use tiny devices or micro-incisions to improve fluid drainage with less tissue disruption. They’re approved for mild and moderate glaucoma and carry lower complication rates than traditional surgery. Recovery tends to be faster, and they’re often performed at the same time as cataract surgery. For mild and moderate disease, research shows MIGS performs comparably to trabeculectomy. Interestingly, in severe glaucoma, one study found that MIGS actually had a lower failure rate requiring repeat surgery than trabeculectomy.
Other surgical options include drainage implants, small tubes inserted into the eye that shunt fluid to a reservoir on the eye’s surface. These are typically reserved for cases where other approaches have failed or aren’t suitable.
Living With Glaucoma
Glaucoma is a lifelong condition. Treatment can slow or halt progression, but it cannot restore vision already lost. That makes early detection critical. The global number of people with open-angle glaucoma is projected to rise from about 80 million today to nearly 187 million by 2060, driven largely by aging populations and increasing rates of nearsightedness.
Regular eye exams are the only reliable way to catch glaucoma before it steals your sight. If you’re over 40, have a family history, or belong to a higher-risk group, comprehensive eye exams every one to two years give your doctor the baseline measurements needed to spot changes early. If you’ve already been diagnosed, sticking to your treatment plan and attending monitoring appointments are the most important things you can do to protect your remaining vision.