Glaucoma doesn’t shout. It doesn’t cause pain or blurry vision in the early stages. By the time you notice something’s wrong, the damage is often permanent. That’s why it’s called the silent thief of sight. Around 76 million people worldwide have it today, and that number is expected to climb to over 110 million by 2040. Most don’t know they have it until it’s too late.

What Actually Happens in Glaucoma?

At its core, glaucoma is damage to the optic nerve-the cable that sends visual information from your eye to your brain. This damage isn’t random. It’s usually tied to pressure inside the eye, called intraocular pressure (IOP). Normal IOP ranges from 10 to 21 mmHg. Anything above that raises your risk. But here’s the twist: not everyone with high pressure gets glaucoma, and not everyone with glaucoma has high pressure.

The real culprit is mechanical strain at the back of the eye, where the optic nerve exits. A mesh-like structure called the lamina cribrosa acts like a sponge-like barrier. When pressure builds up, this structure gets stretched. Studies show that in glaucoma patients, this area moves backward 30-50% more than in healthy eyes. That constant tugging damages the nerve fibers passing through it. These fibers are part of retinal ganglion cells, and once they die, they don’t come back.

It’s not just about pressure inside the eye. Your brain’s pressure-called intracranial pressure (ICP)-also matters. Think of it like water pressure in a hose. If the pressure outside the hose is low and the pressure inside is high, the hose bursts. In glaucoma, if your eye pressure is 20 mmHg and your brain pressure is only 10 mmHg, that 10-point difference is pulling on the optic nerve. That’s why some people with IOP under 15 mmHg still lose vision. This is called normal-tension glaucoma, and it’s especially common in Asian populations, making up nearly half of all glaucoma cases there.

Types of Glaucoma: It’s Not Just One Disease

There are several types, and each behaves differently.

Primary open-angle glaucoma (POAG) is the most common-about 90% of cases in the U.S. The drainage system in your eye slowly clogs over time. Fluid builds up. Pressure rises. You feel nothing. This form creeps up silently, often after age 50.

Normal-tension glaucoma (NTG) is the puzzling one. IOP stays below 21 mmHg, yet the optic nerve still gets damaged. Studies show that reducing IOP by just 30% in NTG patients cuts progression risk from 35% to 12% over seven years. That proves pressure-even if it’s "normal"-still matters. Some researchers believe poor blood flow to the optic nerve or autoimmune issues might be at play here.

Angle-closure glaucoma is less common globally but far more dangerous. It happens when the iris blocks the drainage angle suddenly. Pressure spikes fast-sometimes to 40 or 50 mmHg. Symptoms include severe eye pain, headache, nausea, and seeing halos around lights. This is an emergency. Without treatment, you can lose vision in days.

Secondary glaucomas come from other problems: eye injuries, inflammation, tumors, or even long-term steroid use. Pseudoexfoliative glaucoma, where flaky material clogs the drainage system, is especially aggressive and common in older adults.

How Do Doctors Diagnose It?

Since glaucoma shows no early symptoms, diagnosis relies on tools-not how you feel.

• Tonometry measures eye pressure. The gold standard is Goldmann applanation tonometry. It’s accurate, but pressure changes throughout the day-highest in the morning. That’s why a single reading can be misleading.
• Optical Coherence Tomography (OCT) takes ultra-detailed images of the optic nerve and retinal nerve fiber layer. It can detect thinning as small as 5-10 microns-thinner than a human hair. This is often the first sign of damage.
• Visual field testing (like Humphrey perimetry) checks your peripheral vision. It finds blind spots as small as 1 dB in sensitivity. Glaucoma eats away at your side vision first, so you won’t notice until it’s advanced.
• Fundus photography captures images of the optic disc. A larger cup-to-disc ratio means more nerve loss.

Doctors combine these tests. One alone isn’t enough. A person might have high pressure but a healthy optic nerve. Another might have normal pressure but clear nerve damage on OCT. Both need treatment.

Treatment: Lowering Pressure Saves Sight

The goal isn’t to cure glaucoma-it’s to stop it from getting worse. And the most proven way is lowering IOP.

Eye drops are the first line. Prostaglandin analogs like latanoprost reduce pressure by 25-33% with just one drop a day. But side effects are real: eyelashes grow longer, eyelids darken, and fat around the eyes can sink in. About 1 in 5 people stop taking them because of this.

Laser treatment (trabeculoplasty) opens up the drainage system. It works in 75% of cases at first, but effectiveness drops about 10% each year. It’s not a cure, but it can delay the need for surgery.

Surgery is for advanced cases. Trabeculectomy creates a new drainage channel. It’s 85-90% successful in the first year, but many scar over time. Newer options like MIGS (minimally invasive glaucoma surgery), such as the iStent, are safer and faster. They lower pressure by 20-25%, with 70-80% success at two years.

Target pressure isn’t one-size-fits-all. If you have mild glaucoma, doctors might aim for 18-21 mmHg. For severe cases, they’ll push it down to 12-15 mmHg. That’s a 30-50% drop from your baseline. The Early Manifest Glaucoma Trial showed that hitting this target cuts progression risk by half.

Why People Stop Treatment-and What Happens When They Do

Here’s the ugly truth: half of glaucoma patients stop their eye drops within a year. Only 25% are still using them after two years.

Why? Side effects. Forgetting. Cost. And the fact that they feel fine. If you don’t see changes, it’s easy to think, "It’s not working," or "I don’t need it anymore." But glaucoma doesn’t care how you feel. It keeps damaging your nerve fibers quietly.

A 2022 survey of 1,200 patients found 68% lived in fear of blindness. That anxiety is real. But the data shows: those who stick with treatment rarely lose vision. One patient on a forum wrote that after a trabeculectomy, their pressure dropped from 32 to 14 mmHg-and their vision stabilized for over 10 years. That’s the power of consistent care.

The Future: Beyond Pressure Lowering

Researchers are no longer just focused on pressure. They’re looking at ways to protect the nerve itself.

One promising area is neuroprotection. The drug brimonidine, originally used to lower pressure, may also directly protect nerve cells. In the LIBERTI study, NTG patients on brimonidine had 30% slower vision loss than those on timolol-even when pressure was equally low.

Other experiments are even more exciting. Oncomodulin, a natural growth factor, has triggered 40% axon regeneration in animal studies. CNTF implants (a nerve growth protein) preserved 2.5 dB more vision over two years in early trials. Gene therapy is being tested to fix the drainage system at the root level-early results show 25% IOP reduction in six months.

Home monitoring is also coming. Contact lenses like the Triggerfish sensor track pressure 24/7, with accuracy within 1.5 mmHg. AI-powered OCT analysis can now detect early glaucoma with 94% accuracy. These tools could make diagnosis faster and treatment more personal.

What You Can Do

If you’re over 40, get your eyes checked-even if you see fine. If you have a family history, start even earlier. Glaucoma runs in families. If you’re African, Hispanic, or Asian, your risk is higher.

Don’t wait for symptoms. If you’re diagnosed, take your drops every day. Set phone reminders. Talk to your doctor about side effects-there are alternatives. If your pressure is normal but you have nerve damage, don’t assume you’re safe. You still need treatment.

Glaucoma isn’t a death sentence. It’s a chronic condition, like high blood pressure. Manage it, and you keep your sight. Ignore it, and you risk losing it forever.