What Is Glaucoma and How Is It Treated?

What causes glaucoma?

The optic nerve carries visual signals from the retina to the brain. Glaucoma damages the nerve fibers in that nerve, creating blind spots in your vision. The most common mechanism involves the fluid pressure inside the eye (called intraocular pressure, or IOP).

The eye continuously produces and drains a clear fluid called aqueous humor. When drainage is impaired, pressure inside the eye rises, and sustained elevated pressure can compress and damage the optic nerve over time.

However, high pressure does not always cause glaucoma, and some people develop glaucoma with normal IOP — a type called normal-tension glaucoma. Reduced blood flow to the optic nerve and other factors also contribute in some cases.

The main types are:

• Primary open-angle glaucoma (POAG) — the most common form. The drainage angle between the iris and cornea is open and appears normal, but drainage is functionally impaired, leading to gradual pressure buildup. It progresses silently over years. 1Ref 1Gedde SJ, Vinod K, Wright MM, Muir KW, Lind JT, Chen PP, Li T, Mansberger SL; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Panel (2021).Primary Open-Angle Glaucoma Preferred Practice Pattern.POAG definition, diagnosis workup (tonometry, perimetry, OCT, gonioscopy, pachymetry), risk factors including race and family history, treatment ladder (drops, laser, surgery)
• Primary angle-closure glaucoma — the drainage angle physically narrows or closes, causing pressure to rise suddenly or gradually. Acute angle closure can be a medical emergency. 2Ref 2Gedde SJ, Chen PP, Muir KW, Vinod K, Lind JT, Wright MM, Li T, Mansberger SL; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Panel (2021).Primary Angle-Closure Disease Preferred Practice Pattern.Angle-closure glaucoma definition, acute presentation as emergency, laser peripheral iridotomy treatment
• Normal-tension glaucoma — optic nerve damage occurs despite normal IOP; vascular and other factors are involved.
• Secondary glaucoma — caused by another condition (such as inflammation, injury, steroid use, or certain medications).
• Congenital/developmental glaucoma — present from birth; rare.

What are the early signs of glaucoma?

Primary open-angle glaucoma — by far the most common type — typically has no early symptoms. That is why it is often called "the silent thief of sight." By the time most people notice vision changes, significant optic nerve damage has already occurred.

When symptoms do appear in advanced cases they include: - Loss of peripheral (side) vision, often in patches - Tunnel vision in late-stage disease - Blurred vision

Acute angle-closure glaucoma, by contrast, comes on suddenly and is a medical emergency: - Sudden severe eye pain - Headache, nausea, vomiting - Sudden blurred or hazy vision - Halos around lights - Eye redness

Anyone experiencing these symptoms suddenly should seek emergency care immediately. [2, 3]

Who is at higher risk for glaucoma?

Risk factors for primary open-angle glaucoma include:

• Age — risk increases substantially after 60
• Family history — having a first-degree relative with glaucoma meaningfully increases risk
• Elevated intraocular pressure — though not diagnostic on its own
• African ancestry — POAG is more common and often more severe in people of African descent; it can also appear at younger ages
• Thin central cornea — associated with higher glaucoma risk regardless of measured IOP
• Myopia (nearsightedness) — associated with increased risk, particularly for normal-tension glaucoma
• Diabetes and high blood pressure — associated with elevated risk in some studies
• Long-term use of corticosteroid medications — can raise IOP

Hispanic/Latino adults are also at elevated risk and develop glaucoma at younger ages on average than non-Hispanic white adults. [1, 3]

How is glaucoma diagnosed?

Diagnosis requires a comprehensive eye examination by an ophthalmologist. Key components include:

• Tonometry — measuring intraocular pressure
• Ophthalmoscopy (funduscopy) — examining the optic nerve head for signs of damage, including "cupping" (enlargement of the optic cup relative to the disc)
• Visual field testing (perimetry) — mapping your peripheral vision to detect early loss
• Optical coherence tomography (OCT) — imaging that measures the thickness of the retinal nerve fiber layer; can detect damage before visual field loss appears
• Gonioscopy — a specialized contact lens exam to assess the drainage angle
• Pachymetry — measuring corneal thickness, which affects IOP interpretation

A single high IOP reading does not diagnose glaucoma. Conversely, normal IOP does not rule it out. The combination of findings across these tests is what an ophthalmologist uses. 1Ref 1Gedde SJ, Vinod K, Wright MM, Muir KW, Lind JT, Chen PP, Li T, Mansberger SL; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Panel (2021).Primary Open-Angle Glaucoma Preferred Practice Pattern.POAG definition, diagnosis workup (tonometry, perimetry, OCT, gonioscopy, pachymetry), risk factors including race and family history, treatment ladder (drops, laser, surgery)

How is glaucoma treated?

Treatment cannot restore vision that has already been lost, but it can prevent further damage. The goal is to lower intraocular pressure to a target level that protects the remaining optic nerve.

Eye drops Medicated drops are usually the first line of treatment. They work by reducing aqueous fluid production or improving drainage. Different classes of drops have different mechanisms; your ophthalmologist may prescribe more than one if a single drop does not reach the target pressure. Consistent use is critical — missing doses allows pressure to rise. 1Ref 1Gedde SJ, Vinod K, Wright MM, Muir KW, Lind JT, Chen PP, Li T, Mansberger SL; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Panel (2021).Primary Open-Angle Glaucoma Preferred Practice Pattern.POAG definition, diagnosis workup (tonometry, perimetry, OCT, gonioscopy, pachymetry), risk factors including race and family history, treatment ladder (drops, laser, surgery)

Laser treatments - *Selective laser trabeculoplasty (SLT)* — treats the drainage tissue in the angle to improve outflow. Often used as an alternative or addition to drops; can be repeated. - *Laser peripheral iridotomy (LPI)* — creates a small opening in the iris to relieve pressure in angle-closure glaucoma.

Surgery - *Trabeculectomy* — creates a new drainage channel in the eye wall. - *Minimally invasive glaucoma surgery (MIGS)* — a growing group of procedures with smaller incisions and faster recovery, often done at the time of cataract surgery. - *Glaucoma drainage devices* — implanted tubes that help drain aqueous fluid.

Surgery is typically reserved for cases where drops and laser treatment have not controlled pressure adequately, or when pressure needs to be reduced significantly.

All people with glaucoma require lifelong monitoring, as the disease can change over time and treatment may need adjustment. [1, 3]