Glaucoma: Symptoms, Causes, Diagnosis & Treatment Guide

A population-based survey published in BMJ Ophthalmology found glaucoma in 3.2% of Bangladeshis over age 35, with another 10.1% classified as "glaucoma suspects" — figures that, extrapolated to the 2022 national census, point to roughly 1.9 million people over 35 already living with the disease. The more alarming number is how many of them know it: eye specialists estimate that about 90% of glaucoma patients in Bangladesh are unaware they have the condition, often until they have already lost significant, irreversible vision. Glaucoma earns its nickname — "the silent thief of sight" — honestly, and understanding how it develops, what it feels like (and often doesn't), and when testing matters is the best defense against losing vision you can never get back.

What Is Glaucoma?

Glaucoma is not a single disease but a group of eye conditions that share one outcome: progressive damage to the optic nerve, the cable that carries visual information from the eye to the brain. In most cases, this damage is linked to pressure building up inside the eye (intraocular pressure, or IOP), caused by a backup in the eye's internal drainage system. The eye constantly produces a clear fluid called aqueous humor, which normally drains out through a mesh-like channel called the trabecular meshwork. When drainage slows or the drainage angle narrows, fluid builds up, pressure rises, and over time this pressure — or sometimes poor blood flow to the nerve even without high pressure — damages the delicate nerve fibers that make up the optic nerve.

Once optic nerve fibers die, they do not regenerate. This is the central fact that shapes everything about how glaucoma is managed: treatment cannot restore vision already lost. It can only slow or stop further loss, which is why early detection changes outcomes dramatically.

Types of Glaucoma

Of all non-congenital glaucoma cases, roughly 85% are primary open-angle glaucoma (POAG), about 10% are primary angle-closure glaucoma (PACG), and about 5% are secondary glaucoma.

• Open-angle glaucoma: The drainage angle looks structurally open under examination, but fluid still drains too slowly. This form is chronic, painless, and progresses gradually — often over years — which is exactly why it goes unnoticed for so long.
• Angle-closure glaucoma: The angle between the iris and cornea narrows or closes outright, blocking drainage more abruptly. This can happen gradually with no symptoms (chronic angle-closure) or suddenly as an acute attack — a true eye emergency with severe pain, redness, and rapid vision loss.
• Secondary glaucoma: Triggered by another condition or exposure — eye injury, long-term steroid use, uveitis (eye inflammation), or diabetic eye disease, which can cause a particularly aggressive form called neovascular glaucoma.
• Congenital/childhood glaucoma: A rarer form present from birth or early childhood, caused by abnormal development of the eye's drainage structures.

A Dhaka Division study found primary open-angle glaucoma accounted for about 75% of glaucoma cases detected there, consistent with the global pattern of open-angle disease being the most common form.

Symptoms: Why Most People Miss It

This is the heart of the problem. Open-angle glaucoma typically causes no symptoms at all in its early stages. Vision loss begins in the peripheral ("side") field of vision, while central vision — the part used for reading, recognizing faces, and driving — is usually spared early on. Because the brain is remarkably good at filling in gaps using information from both eyes, people often don't notice anything is wrong until the damage is extensive. Tunnel vision, where only a narrow central field remains, is a late-stage sign, not an early one — by the time it appears, substantial and permanent damage has already occurred.

Acute angle-closure glaucoma is the opposite: it announces itself unmistakably and demands immediate action. Warning signs of an acute attack include:

• Sudden, severe eye pain
• A red eye
• Rapidly blurred vision
• Halos or rainbow-colored rings seen around lights
• Headache, nausea, and vomiting

Without urgent treatment, acute angle-closure glaucoma can cause blindness within days. Anyone with this combination of symptoms should go to an eye emergency department immediately, not wait for a routine appointment.

Who Is at Higher Risk?

• Age: Risk rises after 40 and increases further after 60 — age is the single strongest risk factor for open-angle glaucoma.
• Family history: Having a parent or sibling with glaucoma raises personal risk and is a reason to start screening earlier.
• Diabetes: Increases glaucoma risk generally, and diabetic retinopathy can trigger the aggressive secondary form, neovascular glaucoma.
• Refractive error: High myopia (nearsightedness) is linked to higher open-angle glaucoma risk; hyperopia (farsightedness) and naturally shallow anterior chambers — more common in older adults, particularly women — raise angle-closure risk.
• Long-term steroid use: Prolonged use of steroid eye drops, and sometimes oral or inhaled steroids, without medical supervision can raise eye pressure and trigger steroid-induced glaucoma.
• Past eye injury or thin cornea: Both are associated with elevated risk.

How Glaucoma Is Diagnosed

No single test diagnoses glaucoma — it is confirmed through a combination of findings from a comprehensive, dilated eye examination:

• Tonometry (eye pressure measurement): Commonly cited "normal" IOP ranges from about 10 to 21–22 mmHg, though eye pressure naturally fluctuates by more than 10 mmHg over a 24-hour period, so a single reading cannot confirm or rule out glaucoma on its own. An older rule of treating 21 mmHg as a strict cutoff is now considered outdated.
• Gonioscopy: A special lens is used to directly examine the drainage angle, distinguishing open-angle from angle-closure disease.
• Dilated optic nerve examination: The eye specialist examines the cup-to-disc ratio — essentially how much of the optic nerve head is "cupped out." A difference of 0.2 or more between the two eyes is considered highly suspicious for glaucoma, as is loss of the normal pink coloring of the nerve rim.
• Visual field testing (perimetry): Maps out blind spots and peripheral vision loss that the patient themselves usually cannot detect.
• Optical coherence tomography (OCT): A newer imaging test that can detect thinning of the nerve fiber layer before changes show up on a standard visual field test — catching damage even earlier.

An important and often-missed point: eye pressure within the "normal" range does not rule out glaucoma. A form called normal-tension glaucoma causes real optic nerve damage even when IOP measurements look unremarkable, which is why the optic nerve exam and visual field testing matter just as much as the pressure reading.

Treatment: Slowing the Disease, Not Reversing It

Because nerve damage already done cannot be undone, every glaucoma treatment has the same goal: lower eye pressure (or otherwise protect the optic nerve) enough to stop further loss. Treatment typically follows a stepwise path.

1. Eye drops (usually first-line)

Prostaglandin analogues, such as latanoprost, are generally the first choice — they improve fluid drainage and are highly effective at lowering pressure, usually with once-daily dosing. Beta-blockers such as timolol work differently, reducing how much fluid the eye produces. When one medicine isn't enough, doctors may add other classes, including alpha-agonists like brimonidine or carbonic anhydrase inhibitors like dorzolamide. These medicines are available in Bangladesh under various brand names; a pharmacist or treating doctor should confirm the exact product and schedule for an individual patient.

2. Laser treatment

Selective laser trabeculoplasty (SLT) helps the eye's natural drainage system work better in open-angle glaucoma, though its effect can fade over time and is not a permanent cure. For angle-closure disease, laser peripheral iridotomy creates a small opening in the iris to relieve the blockage and is considered definitive treatment — including as an emergency procedure during an acute attack.

3. Surgery

When drops and laser aren't enough to control pressure — typically in more advanced disease — traditional surgeries like trabeculectomy or tube-shunt implantation create new drainage pathways. Newer minimally invasive glaucoma surgeries (MIGS) were developed specifically to offer a safer alternative to these traditional operations, usually for earlier or moderate disease.

Managing an acute angle-closure attack

This is an ophthalmic emergency. Immediate treatment usually combines pressure-lowering medication (such as oral or intravenous acetazolamide) with pilocarpine eye drops to constrict the pupil, followed by laser iridotomy — ideally the same day — to prevent permanent vision loss.

Special Considerations

• Elderly adults: Age itself is the leading risk factor, and because symptoms are absent until late, routine screening — not waiting for symptoms — is the only reliable way to catch disease early in this group.
• People with diabetes: Should have regular dilated eye exams covering both diabetic retinopathy and glaucoma risk, since diabetic eye disease can trigger secondary glaucoma.
• Long-term steroid users: Never continue steroid eye drops beyond a doctor's prescribed course without monitoring — unsupervised long-term use is a recognized, preventable cause of glaucoma.
• Those with a family history: Should mention it to their eye doctor and consider starting screening earlier than the general population.
• Pregnant women: Any existing glaucoma medication plan should be reviewed with both an eye specialist and obstetrician, since medication choices may need adjusting during pregnancy.

Glaucoma vs. Cataract: Don't Confuse the Two

Both are common, age-related eye conditions, and a person can have both at once — but they are fundamentally different diseases with different outlooks.

• What goes wrong: A cataract is clouding of the eye's natural lens. Glaucoma is progressive damage to the optic nerve, usually linked to internal eye pressure.
• Reversibility: Cataracts can be fully corrected with lens-replacement surgery, and cataracts do not grow back. Glaucoma damage is permanent — treatment can only prevent further loss, not restore vision already lost.
• Typical symptoms: Cataracts cause gradually blurred, hazy vision, glare, and faded colors. Glaucoma usually causes no early symptoms at all, with peripheral vision loss as the first sign when one appears.
• Diagnosis: Cataracts are seen directly on a slit-lamp exam of the lens. Glaucoma requires pressure measurement, angle examination, optic nerve assessment, and visual field testing together.
• One does not fix the other: Cataract surgery can modestly lower eye pressure in some patients, but it is not a treatment for glaucoma, and glaucoma treatment does not clear a cataract.

When to See a Doctor

Seek emergency care immediately if you or someone around you develops sudden eye pain, a red eye, rapidly blurred vision, halos around lights, headache, nausea, or vomiting together — this combination can signal an acute angle-closure attack, and every hour of delay risks permanent vision loss.

Book a routine comprehensive, dilated eye exam — even with zero symptoms — if you are over 40, have a family history of glaucoma, have diabetes, have high myopia, or have used steroid medications long-term. Since open-angle glaucoma causes no early warning signs, screening is the only way most people will catch it before damage accumulates.

Prevention

• Get a comprehensive dilated eye exam on a regular schedule after age 40, more frequently with any risk factor above — this is the single most effective preventive step, precisely because symptoms don't come first.
• Keep diabetes and blood pressure well controlled.
• Never use steroid eye drops beyond what a doctor prescribes, and never restart them without supervision.
• Protect your eyes from injury during sports, work, and household tasks.
• Know and share your family's eye-health history with your doctor.
• Treat sudden eye pain with redness and vision change as an emergency, not something to wait out overnight.

The Bangladesh Picture

Experts and researchers describe glaucoma as a growing but under-recognized public health problem in Bangladesh. While the national blindness survey found cataract responsible for about 80% of blindness nationally against roughly 1.2% from glaucoma, the far bigger concern is awareness: the Bangladesh Glaucoma Society has noted there is still no comprehensive government data on how many glaucoma patients exist nationally or which type predominates, and the National Eye Care Plan has historically centered on cataract services since 2005. Advocates have called for the plan to add dedicated glaucoma screening and treatment capacity, arguing that a disease affecting an estimated 1.9 million people over 35 — most of whom don't know it — deserves a stronger national response.

Sources: Population-based glaucoma prevalence research published in BMJ Ophthalmology, reporting from the Bangladesh Glaucoma Society and national eye-care experts, and general clinical guidance on glaucoma diagnosis and management.