Glaucoma is called the silent sight thief because most people who have it don't know until significant, permanent damage has already happened. It's the second leading cause of irreversible blindness in the world — and one of the most preventable when it's caught early. Here's what every adult should know.
What glaucoma actually is
Glaucoma is a group of diseases that damage the optic nerve — the cable that carries visual information from the eye to the brain. Most cases are linked to elevated pressure inside the eye, but a meaningful number occur at "normal" pressures (so-called normal-tension glaucoma).
The damage typically starts in the peripheral vision and slowly progresses inward over years. Because the brain fills in missing peripheral information, most patients literally don't notice anything is wrong until the disease is advanced. By the time central vision is affected, much of what's been lost is permanent.
The two main types
Open-angle glaucoma is by far the most common form. The drainage angle inside the eye is open but isn't draining fluid efficiently, pressure rises gradually, and the optic nerve slowly deteriorates. It's painless and silent.
Angle-closure glaucoma happens when the drainage angle gets physically blocked. The pressure can spike suddenly to dangerous levels, causing severe eye pain, blurred vision, halos, nausea, and a hard red eye. Acute angle-closure is a medical emergency — go to the ER, not a clinic.
Who's at risk
Risk factors for primary open-angle glaucoma include age (incidence climbs sharply after 60), family history of glaucoma, African or Hispanic ancestry, high myopia, diabetes, prolonged use of certain steroids, and a history of significant eye trauma.
If any of those apply to you, regular dilated eye exams are not optional. Glaucoma is much easier to manage than to reverse.
How it's detected
A proper glaucoma evaluation looks at multiple things together:
Eye pressure — measured with a tonometer. Important data, but normal pressure does not rule out glaucoma.
Optic nerve appearance — examined during the dilated retinal exam. Doctors look for cupping, thinning, hemorrhages, and asymmetry between eyes.
OCT imaging — a quick, painless scan that measures the thickness of the nerve fiber layer around the optic nerve. Extremely sensitive to early damage and one of the most important developments in modern glaucoma care.
Visual field testing — measures your peripheral vision in detail. Tedious but essential — it's where functional damage shows up.
Corneal thickness (pachymetry) — affects how accurately eye pressure readings reflect true pressure.
How it's treated
The cornerstone of glaucoma treatment is lowering eye pressure, even in normal-tension cases. Studies consistently show that pressure reduction slows or stops progression for most patients.
Prescription eye drops are usually the first-line treatment. Prostaglandin analogs like latanoprost are commonly used once nightly and are highly effective. Beta-blockers, alpha agonists, carbonic anhydrase inhibitors, and combination drops are all in the toolkit.
Selective laser trabeculoplasty (SLT) is an in-office laser procedure that improves drainage. It's safe, repeatable, and increasingly used as a first-line treatment instead of (or alongside) drops.
Minimally invasive glaucoma surgery (MIGS) — a category of small implantable devices and procedures, often combined with cataract surgery, that lower pressure with much less recovery than traditional glaucoma surgery.
Traditional filtering surgery (trabeculectomy, tube shunts) is reserved for more advanced cases where less invasive options haven't been enough.
What you can do
Get regular comprehensive eye exams. Adults over 40 should be screened at least every two years; over 60 or with risk factors, yearly. If glaucoma runs in your family, your eye doctor needs to know.
If you're diagnosed and prescribed drops, take them as directed — every single day. Glaucoma drops only work if they're in the eye. Skipping doses is one of the most common reasons treatment fails.
Lifestyle factors that may help include cardiovascular health, regular moderate exercise, not smoking, and managing diabetes. None of those replace medical treatment, but they support the eyes generally.
The bottom line
Glaucoma is the disease that justifies your eye exam habit more than almost anything else. It's painless, it's silent, and by the time it announces itself, the damage is permanent. A few minutes of imaging and a visual field test, every couple of years, is the most cost-effective thing you can do for the back half of your visual life.