Glaucoma is experienced by nearly 3 million adults in the U.S. over the age of 40, and open-angle glaucoma (OAG) is the most common form of glaucoma. Primary open-angle glaucoma (POAG) is responsible for 70 to 90% of those cases. The BrightFocus Foundation has glaucoma expert Yvonne Ou, MD, explain the basics about POAG to help you make informed decisions about your eye health.

What is open-angle glaucoma?

Glaucoma is an umbrella term for a group of degenerative eye diseases that affect the optic nerve. The optic nerve is the primary means of transport for visual data from your retina to your brain. Different types of glaucoma are defined by how the damage manifests in the eye.

The “open angle” in primary open-angle glaucoma refers to the open configuration of the eye’s internal drainage system, between the iris (the colored part of your eye) and the cornea (the transparent covering at the front). This is where the aqueous humor (fluid produced in the eye) drains out and enters your circulatory system, regulating your eye’s internal pressure.

Increased internal eye pressure, or intraocular pressure (IOP), is the most significant risk factor in the development of OAG. There is no defining number or limit, however, that determines whether or not you have glaucoma. Every individual’s optic nerve has an eye pressure level that it can withstand, and numbers in the high range are not necessary to define glaucoma.

What are the symptoms?

Open-angle glaucoma is chronic and progressive, but it’s usually asymptomatic in its early to moderate stages. Unlike some other forms, such as acute angle-closure glaucoma, OAG does not generally cause pain, eye redness, or immediate central vision damage—even when eye pressure is high.  

This type of glaucoma occurs in both eyes, though one eye is typically worse than the other. Vision loss from OAG begins in the peripheral (side) visual field. The healthier eye can often compensate for the “bad” eye for years until the disease is quite advanced. 

In advanced glaucoma, you may notice fuzziness or darkness in your peripheral vision and may experience challenges while driving. As the disease continues to progress, the noticeable damage extends from the peripheral vision toward the central vision, eventually affecting other activities, such as reading, cooking, sewing, etc. 

Until that happens, your central vision may remain at 20/20, which is another reason why many people are unaware that they have glaucoma.

What are the risk factors?

The risk factors for open-angle glaucoma are mostly the same as those for glaucoma in general. 

These include:

• Increased eye pressure
• Age 40 or above (risk increases with age)
• Family history of glaucoma (especially a first-degree relative, i.e., parent, sibling, child)
• African American or Hispanic race/ethnicity
• Thin corneas
• High blood pressure
• Overtreated or low blood pressure
• Type 2 diabetes or high blood sugar
• Myopia (severe nearsightedness)

How is OAG diagnosed?

Open-angle glaucoma is diagnosed with a comprehensive eye exam by your eye doctor. 

The examination includes:

• Eye pressure measurement 
• Examination of your optic nerve and retina with eye dilation
• Examination of your eye drainage angle using a special mirrored lens
• Test of your peripheral vision 

Your doctor may also take scans of your optic nerves (optical coherence tomography, or OCT). 

What treatments are available?

All types of glaucoma are currently treated to lower IOP and preserve your remaining vision without adverse side effects, thus helping you maintain quality of life.

Treatment methods include:

• Medication, usually in the form of eye drops, that lower eye pressure by:
  • Improving eye fluid drainage,
  • Reducing eye fluid formation
  • Both of the above, in combination
• Selective laser trabeculoplasty (SLT), which targets the tissues that drain eye fluid
• Surgery, which can take the form of:
  • Minimally invasive glaucoma surgery (MIGS)
  • Trabeculectomy, which creates an alternative drainage path in the eye
  • Tube shunt surgery, which is like trabeculectomy but with the implantation of a fluid shunt

Research is ongoing to find improved methods of treating and preventing all forms of glaucoma. Speak with your eye doctor about which treatment options are best for you. 

*Ou, Y. (2018, July 16). Open-Angle Glaucoma: Are There Symptoms? BrightFocus Foundation. https://www.brightfocus.org/glaucoma/article/symptoms-open-angle-glaucoma

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