Understanding Open-Angle Glaucoma: The “Silent Thief of Sight”

Open-angle glaucoma is one of the leading causes of irreversible blindness — and it’s sneaky. Most patients feel perfectly fine, see normally, and notice nothing wrong… until the disease is already advanced. That’s why understanding this condition (and monitoring it regularly) is absolutely essential.

Let’s break down what it is, why it happens, and how modern treatments can protect your vision for life.

What Is Open-Angle Glaucoma?

Glaucoma is a group of eye diseases that damage the optic nerve — the “cable” that connects your eye to your brain. In most cases, this damage is caused by elevated eye pressure (intraocular pressure, or IOP).

Open-angle glaucoma is the most common form. The “angle” refers to the drainage angle between the iris and cornea where fluid leaves the eye. In open-angle glaucoma:

• The drainage angle itself is physically open

• But the drainage system is clogged internally, reducing fluid outflow

• This causes pressure to slowly build over time

The pressure increase is usually mild and very gradual — which is why patients typically have no pain, no redness, and no vision changes until the optic nerve becomes significantly damaged.

This form of glaucoma accounts for about 80–90% of all cases.

How Does Open-Angle Glaucoma Differ From Narrow-Angle Glaucoma?

Glaucoma isn’t a one-size-fits-all condition. The other major form — narrow-angle glaucoma — behaves very differently.

• Open-Angle Glaucoma

  • Drainage angle is open and normal

  • The problem is inside the drainage meshwork (slow clogging)

  • Vision loss is slow and silent

  • Almost always painless

  • Usually chronic and lifelong

• Narrow-Angle / Angle-Closure Glaucoma

  • Drainage angle is physically crowded or closed

  • Fluid can’t escape because the iris blocks the angle

  • Eye pressure can spike suddenly

  • Can cause severe pain, blurred vision, halos, nausea, and a red eye

  • This is an eye emergency requiring immediate treatment

Many people have a narrow angle anatomy and don’t know it. These patients can prevent angle-closure with a simple laser (LPI) once diagnosed.

Is Glaucoma Hereditary?

Absolutely — and strongly.

• Having a first-degree relative (parent, sibling, or child) with glaucoma dramatically increases your risk

• People of African, Hispanic, and Asian descent have higher genetic risk

• Certain gene variants (e.g., MYOC) are associated with early-onset forms of the disease

If glaucoma runs in the family, yearly eye exams are not optional — they’re essential.

How Open-Angle Glaucoma Is Diagnosed

A glaucoma workup is much more than “the eye pressure check.” Diagnosis involves multiple tests that build a complete picture of optic nerve health.

1. Eye Pressure Measurement (Tonometry)

Elevated pressure is a major risk factor — but many glaucoma patients have normal pressure (“normal-tension glaucoma”). That’s why pressure alone is not enough.

2. Gonioscopy

A quick exam of the drainage angle to determine whether it’s open or narrow.

3. Optic Nerve Evaluation

Dilated exam and photographs to assess:

• Nerve shape

• Cupping

• Rim thinning

• Hemorrhages

4. OCT (Optical Coherence Tomography)

A highly sensitive scan that measures the thickness of the nerve fiber layer and ganglion cell complex. This test can detect damage years before vision loss appears.

5. Visual Field Testing

A computerized test that maps your peripheral vision — where glaucoma damage usually begins.

6. Pachymetry

Measures corneal thickness, which affects the accuracy of pressure readings.

Why Regular Monitoring Is Critical

Most patients with open-angle glaucoma feel perfectly normal. No pain, no blurriness, no red eyes, no flashing warning signs.

The optic nerve can lose 30–40% of its fibers before the patient notices any change in vision.

This is why routine monitoring matters:

• Glaucoma is progressive

• You cannot sense the damage

• Early treatment prevents vision loss

• Missed checkups can allow silent progression

When caught early, glaucoma is one of the most treatable chronic eye diseases. When ignored, the damage is permanent.

Treatment Options for Open-Angle Glaucoma

While glaucoma damage can’t be reversed, reducing eye pressure can stop or dramatically slow down the disease. Today’s treatments are safer and more diverse than ever.

Let’s run through them.

1. Medications

Eye drops are often the first line of treatment and work in two ways:

Reduce Fluid Production

• Beta blockers (timolol)

• Carbonic anhydrase inhibitors (Dorzolamide, Brinzolamide)

• Alpha agonists (Brimonidine)

Increase Fluid Drainage

• Prostaglandin analogs (Latanoprost, Lumigan, Travatan)

• Generally once-per-night and very effective

Combination Drops

Convenient multi-med drops that improve adherence.

2. SLT: Selective Laser Trabeculoplasty

SLT is a gentle, non-invasive laser that improves drainage through the trabecular meshwork.

• Takes 5–10 minutes

• No recovery time

• No incisions

• Reduces dependence on drops

• Works as well as a first-line medication

• Can be repeated

• Proven in major studies (e.g., the LiGHT Trial) to be an excellent first-line treatment

SLT is one of the best evidence-based early options for open-angle glaucoma.

3. MIGS: Minimally Invasive Glaucoma Surgery

These procedures are performed during cataract surgery or as standalone surgeries in select cases.

Common MIGS options include:

• iStent / Hydrus Microstent

• Kahook Dual Blade (KDB)

• OMNI Canaloplasty / Trabeculotomy

• XEN Gel Stent (borderline between MIGS and traditional glaucoma surgery)

Benefits of MIGS:

• Safer than traditional surgery

• Small incisions

• Faster recovery

• Reduces pressure and medication burden

Ideal for mild to moderate glaucoma.

4. Traditional Glaucoma Surgeries

These are used when drops, SLT, and MIGS aren’t enough — typically for moderate to advanced glaucoma.

Trabeculectomy

Creates a new drainage channel (“bleb”) to lower eye pressure significantly.

Tube Shunts

Implants such as:

• Ahmed valve

• Baerveldt tube

These drain aqueous fluid to an external reservoir placed under the eyelid.

Traditional surgeries provide the most powerful long-term pressure lowering, but require more intensive postoperative care.

The Bottom Line

Open-angle glaucoma is common, hereditary, and usually symptom-free — which makes early detection and consistent monitoring absolutely critical. The good news? Modern diagnostics and treatments give us the tools to preserve your vision for life.

With the right combination of:

• Regular exams

• Imaging

• Pressure monitoring

• Medication

• Laser therapy

• And, when needed, surgical intervention

…we can keep glaucoma stable and protect the optic nerve for decades.

Author

Keith Kellum, MD Dr. Keith Kellum is a board certified ophthalmologist with over 25 years of experience. He has been very active and progressive in treating cataract, glaucoma and retinal diseases.