What Is Glaucoma, How Does It Damage Vision Without Symptoms, and What Are the Latest Treatments?

Research-informed explainer — last updated April 12, 2026

Glaucoma is the world's leading cause of irreversible blindness, and its defining cruelty is that it destroys optic nerve fibers silently — most people feel nothing and see nothing unusual until half or more of those fibers are gone. Modern imaging technology, particularly optical coherence tomography (OCT), now allows specialists to detect glaucoma damage years before you would notice any change in your vision, making regular monitoring the single most important intervention after diagnosis.

This article draws on research from five physicians who collectively shaped how glaucoma is understood, detected, and treated. Tien Wong, M.D., at Houston Methodist Hospital, co-authored the definitive global prevalence study projecting that 111.8 million people will have glaucoma by 2040 (6,737 citations). Felipe Medeiros, M.D., Rodgers Endowed Professor and Vice Chair of Research at Bascom Palmer Eye Institute, published the most-cited clinical overview of glaucoma pathophysiology and treatment in JAMA (3,932 citations) and the primary open-angle glaucoma disease primer in Nature Reviews (632 citations). Joel Schuman, MD, Co-Director of the Glaucoma Service at Wills Eye Hospital, co-invented OCT and published the first quantification of nerve fiber layer thickness in glaucoma using OCT (872 citations) — the measurement now standard in every glaucoma practice. Jeffrey Liebmann, MD, Glaucoma Service Director at New York-Presbyterian Hospital, published on glaucomatous macular damage (854 citations) and a randomized trial comparing brimonidine to timolol in preserving visual function (386 citations). Janey Wiggs, MD, PhD, at Massachusetts General Hospital, identified 68 genetic loci associated with intraocular pressure and primary open-angle glaucoma in a landmark genome-wide association study (380 citations).

What happens inside a glaucomatous eye

The optic nerve carries visual information from the retina to the brain through roughly 1.2 million nerve fibers. In glaucoma, those fibers die progressively, starting at the periphery of the visual field. Because humans use two eyes together and the brain compensates for peripheral losses, most patients lose 30–40% of their nerve fibers before noticing any change in daily vision.

The most common form — primary open-angle glaucoma — occurs when the eye's drainage system becomes less efficient over time, causing intraocular pressure (IOP) to rise. Elevated IOP compresses and starves the optic nerve. However, as Dr. Medeiros's JAMA review details, up to 40% of glaucoma cases occur at "normal" IOP (below 21 mmHg), meaning pressure alone is an incomplete picture. The real target is the health of the optic nerve and nerve fiber layer, assessed primarily through OCT.

According to the primary open-angle glaucoma primer co-authored by Dr. Medeiros, risk factors beyond elevated IOP include advanced age, Black or Hispanic ethnicity (two to four times higher prevalence than white populations), positive family history, thin corneas, and large cup-to-disc ratio on optic nerve examination.

The genetics of risk

Dr. Wiggs's genome-wide association study identified 68 loci influencing intraocular pressure and glaucoma susceptibility — establishing that genetic risk is real, polygenic, and increasingly measurable. A first-degree relative with glaucoma roughly doubles your lifetime risk. While genetic testing for glaucoma is not yet standard clinical practice, family history should prompt earlier and more frequent screening, typically beginning at age 40 rather than 60.

How glaucoma is detected before you lose vision

The key insight from Dr. Schuman's original OCT work is that structural damage precedes functional loss. OCT measures the thickness of the retinal nerve fiber layer (RNFL) around the optic nerve with micron-level precision — without any dye injection, contact with the eye, or discomfort. When RNFL thickness falls below age-adjusted normative values (shown as color-coded maps on the scan printout), it signals nerve fiber loss that may not yet appear on a visual field test.

Dr. Medeiros's study evaluating RNFL, optic nerve head, and macular thickness measurements in 162 patients found that OCT had strong diagnostic accuracy for glaucoma detection, with the RNFL being particularly sensitive for early disease. The macular ganglion cell complex — also measurable by OCT — provides complementary information, especially for detecting glaucoma damage that predominantly affects central rather than peripheral vision, as described in Dr. Liebmann's analysis of glaucomatous macular damage.

Visual field testing (perimetry) remains essential but is subjective and variable. The current standard of care pairs annual OCT imaging with visual field testing every six to twelve months, allowing the treating physician to track the rate of progression and adjust treatment before meaningful functional loss occurs.

Treatment: from drops to surgery

The goal of treatment is to lower IOP sufficiently to halt further nerve fiber loss. The required target pressure varies by patient — someone with very advanced damage needs a lower pressure than someone caught early.

Eye drops: Prostaglandin analogs (latanoprost, bimatoprost, travoprost) are first-line for most patients, reducing IOP by 25–35% with once-daily dosing. Beta-blockers, alpha-agonists (including brimonidine), and carbonic anhydrase inhibitors are added when a single agent is insufficient. Dr. Liebmann's Low-Pressure Glaucoma Treatment Study found that brimonidine preserved visual function significantly better than timolol in patients with normal-tension glaucoma, suggesting a possible neuroprotective effect beyond IOP reduction alone.

Laser trabeculoplasty (SLT): Selective laser trabeculoplasty applies brief pulses of low-energy laser to the drainage angle, improving outflow and lowering IOP by 20–30%. It can be used as first-line treatment or to reduce drop burden. Effects typically last 3–5 years and the procedure can be repeated.

Minimally invasive glaucoma surgery (MIGS): A rapidly expanding category of procedures — iStent, Hydrus microstent, goniotomy, canaloplasty — that improve aqueous humor drainage with fewer risks than traditional surgery. MIGS is typically performed at the time of cataract surgery for patients with mild to moderate glaucoma.

Trabeculectomy and tube shunts: Traditional filtering surgeries that create or reroute a new drainage pathway. Reserved for patients with advanced glaucoma or those unresponsive to drops and laser. More effective at lowering IOP than MIGS but carry higher risks of hypotony, infection, and need for revision.

Monitoring: what "stable glaucoma" actually means

A diagnosis of glaucoma does not mean you will go blind. It means you require lifelong monitoring to ensure the disease is not progressing. "Stable" means that serial OCT scans show no significant thinning of the nerve fiber layer over time and visual field tests show no new or expanding defects. Most people treated appropriately maintain useful vision for their entire lives.

The challenge is adherence. Studies consistently show that 30–50% of glaucoma patients do not take drops as prescribed — and because there are no symptoms to prompt compliance, the stakes of missed doses are invisible until the next clinic visit reveals progression.

Questions to ask your doctor

• What is my current nerve fiber layer thickness, and is it changing between visits?
• What intraocular pressure target are you aiming for in my specific case?
• Should I be considering laser treatment as a first-line option to avoid daily drops?
• Given my family history, should my adult children be screened?
• How quickly is my glaucoma progressing, and when would you recommend surgery?
• Are my current drops containing preservatives that could be worsening ocular surface symptoms?

The bottom line

Glaucoma silently destroys optic nerve fibers over years, but today it can be detected on OCT before you notice any symptoms — and treatment that lowers intraocular pressure prevents further damage in the vast majority of patients. The threat is not the diagnosis itself but rather delayed diagnosis and inconsistent treatment. If you are over 40 with a family history, high eye pressure, or relevant risk factors, a comprehensive glaucoma evaluation with OCT imaging is the most important step you can take to protect your vision.