Glaucoma is a group of eye conditions that damage the optic nerve, the cable of nerve fibers connecting your eye to your brain. It is one of the leading causes of irreversible blindness worldwide, and most forms progress so slowly that you won’t notice vision changes until significant damage has already occurred. The central problem in most cases is a buildup of fluid pressure inside the eye, though some people develop glaucoma even with normal pressure levels.
How Glaucoma Damages Your Vision
Your eye constantly produces a clear fluid called aqueous humor, which nourishes the front of the eye and then drains out through a mesh-like channel. When that drainage system becomes partially blocked or less efficient, fluid accumulates and pressure inside the eye rises. Normal eye pressure falls between 10 and 21 mmHg. When pressure climbs above that range, or sometimes even within it, the force presses on the optic nerve at the back of the eye.
That pressure disrupts the supply lines that keep nerve cells alive. Retinal ganglion cells, the neurons responsible for sending visual information to the brain, depend on a constant flow of survival signals traveling along their long fibers. Elevated pressure physically pinches those fibers where they pass through the back of the eye, choking off the transport of essential growth factors. Starved of these signals, the cells gradually die. Because the damage starts with nerve fibers serving your peripheral vision, you can lose a surprising amount of your visual field before you notice anything wrong.
Types of Glaucoma
Open-Angle Glaucoma
This is the most common form. The drainage channel looks structurally open, but the tissue inside it resists fluid flow more than it should. Pressure rises gradually over months or years. There are no symptoms in the early stages. Over time, patchy blind spots develop in your side vision, typically in the upper visual field first. By the time central vision is affected, the disease is advanced.
Angle-Closure Glaucoma
In this form, the iris physically blocks the drainage channel. It can happen slowly (chronic angle closure) or all at once. An acute attack is an ophthalmological emergency with an incidence of roughly 2 to 4 cases per 100,000 people per year in Europe. Pressure spikes rapidly and can cause permanent vision loss within hours if untreated.
The symptoms of an acute attack are distinctive: sudden eye pain or pain around the eye, a red eye, rapidly worsening or blurry vision, and multicolored halos around lights. About 44% of patients also experience nausea and vomiting, and roughly a third develop a headache on the affected side. Because these general symptoms can mimic a migraine or stomach illness, acute angle closure is sometimes misdiagnosed in emergency rooms. If you experience sudden eye pain with blurred vision and nausea, getting to an eye doctor or emergency department quickly is critical.
Normal-Tension Glaucoma
Some people develop optic nerve damage even though their eye pressure never rises above 21 mmHg. This form, called normal-tension glaucoma, may involve reduced blood flow to the optic nerve, oxidative stress, or structural weakness in the tissue supporting the nerve fibers. It tends to cause blurred vision that worsens gradually, followed by peripheral vision loss. It remains somewhat controversial whether this is a distinct disease or simply the lower-pressure end of the open-angle glaucoma spectrum.
Who Is Most at Risk
Age is the biggest non-modifiable risk factor. Your risk rises steadily after 40, which is why the American Academy of Ophthalmology recommends a baseline comprehensive eye exam at that age. Family history also matters: several chromosomal regions have been linked to inherited risk, though known genetic variants still explain only a small fraction of cases.
Race and ethnicity play a significant role. Black Americans are diagnosed with glaucoma about 10 years earlier than white Americans, progress faster, and are six times more likely to go blind from the disease in some age groups. The Baltimore Eye Survey found that glaucoma prevalence among people of African descent was six times higher than among white Americans in certain age brackets. Studies in Barbados and East Africa have confirmed similarly high rates. Latino populations also face elevated risk. Research into why has pointed to differences in how cells in the eye’s drainage tissue respond to stress, including variations in mitochondrial gene activity that may make the drainage tissue more vulnerable to degeneration.
Elevated eye pressure itself is the most important modifiable risk factor, and it appears about 12 years earlier in Black Americans. Other risk factors include extreme nearsightedness, a thinner cornea, and a family history of the disease.
How Glaucoma Is Diagnosed
Because the most common form has no early symptoms, glaucoma is usually caught during a routine eye exam. Your eye doctor uses several tools to build a complete picture:
- Tonometry measures the pressure inside your eye. The gold standard is a small device pressed gently against your numbed cornea.
- Ophthalmoscopy lets the doctor examine the optic nerve directly, looking for signs of cupping (a hollowing out of the nerve head that signals damage).
- Visual field testing maps your peripheral vision to detect blind spots you may not have noticed.
- Pachymetry measures corneal thickness, which affects how accurately pressure readings reflect true internal pressure. A thinner cornea can make pressure appear lower than it really is.
- Optical coherence tomography (OCT) uses light waves to create a cross-sectional image of the nerve fiber layer at the back of your eye. It can detect thinning of that layer before you experience any vision loss, making it one of the most valuable tools for early detection.
- Gonioscopy uses a special lens to inspect the drainage angle directly, which determines whether you have open-angle or angle-closure disease.
No single test confirms glaucoma. Diagnosis comes from combining pressure readings, nerve appearance, nerve fiber thickness, and visual field results over time.
How Often to Get Screened
The American Academy of Ophthalmology recommends a comprehensive eye evaluation at age 40, then repeat exams every 2 to 4 years for people aged 40 to 54 with no risk factors. Between 55 and 64, that window narrows to every 1 to 3 years, and after 65, every 1 to 2 years. If you have risk factors like African or Latino heritage, a family history of glaucoma, or high eye pressure, more frequent exams starting earlier make sense, though no specific schedule has been standardized for higher-risk groups.
Treatment: Lowering Eye Pressure
All current glaucoma treatments work by reducing pressure inside the eye. Even in normal-tension glaucoma, lowering pressure further has been shown to slow damage. Treatment cannot restore lost vision, only preserve what remains, which is why early detection matters so much.
Most people start with prescription eye drops. These fall into a few main categories based on how they lower pressure. Some reduce the amount of fluid your eye produces, essentially turning down the faucet. Others increase the rate at which fluid drains out, either through the eye’s natural drainage channel or through an alternative pathway in the surrounding tissue. Prostaglandin-based drops, which boost drainage, are among the most commonly prescribed first-line treatments because they’re effective and typically used just once a day. Other drop types work by slowing fluid production or combining both approaches.
The biggest challenge with eye drops is using them consistently. Missing doses allows pressure to creep back up, and many people struggle with the daily routine, especially when the drops cause side effects like redness, stinging, or blurred vision.
Laser and Surgical Options
When drops aren’t enough or aren’t tolerated well, laser procedures can open or improve the drainage pathway. For angle-closure glaucoma, a laser can create a tiny hole in the iris to relieve the blockage.
Traditional surgery (trabeculectomy) creates a new drainage channel for fluid to leave the eye. It is effective but involves more tissue disruption and a longer recovery. A newer category called minimally invasive glaucoma surgery, or MIGS, uses tiny devices inserted through a small corneal incision from inside the eye. These procedures cause less tissue disruption, carry a more favorable risk profile, and allow faster recovery compared to traditional surgery. They’re best suited for mild to moderate disease and are sometimes performed at the same time as cataract surgery.
For more advanced cases, drainage implants or traditional surgery may still be necessary. Your doctor’s recommendation will depend on how far the disease has progressed, how high your pressure is, and how well you’ve responded to other treatments.
Living With Glaucoma
Glaucoma is a lifelong condition. Once diagnosed, you’ll need regular monitoring, typically every 3 to 12 months depending on severity, to check whether the disease is stable or progressing. Treatment adjustments are common. Many people go through several eye drop formulations or eventually add laser or surgical treatment as the disease evolves.
The vision already lost to glaucoma cannot be recovered, but with consistent treatment, most people retain functional vision for life. The real danger is in not knowing you have it. Because the most common form steals peripheral vision silently over years, routine eye exams remain the single most effective way to catch glaucoma before it causes damage you can feel.