Evidence Based

Glaucoma

What Is Glaucoma?

Glaucoma is an eye disease that damages your optic nerve and can result in irreversible vision loss. Your optic nerve transmits visual information from the retina (the tissue in the back of your eye) to the occipital lobe (the area of your brain that processes vision). Vision loss occurs gradually, sometimes for several years before any symptoms develop.

Glaucoma is a leading cause of irreversible blindness around the world.

Types of Glaucoma and Their Causes

Glaucoma is divided into several subtypes. Some types of glaucoma are chronic and progress slowly, while other forms are acute and require prompt medical attention.

  • Primary open-angle glaucoma (POAG) is the most common form of glaucoma. POAG is associated with high eye pressure, which causes damage to the optic nerve. However, some people with normal eye pressure can also develop POAG. Typically, POAG progresses over several years before you may notice any symptoms.  
  • Angle-closure (narrow-angle) glaucoma occurs when the drainage structure in your eye, called the angle, is narrow. People with narrow angles have a higher risk of the angle closing up, which causes fluid to build up inside your eye. Your eye pressure may start to rise, resulting in damage to the optic nerve.

If the angle closes completely, your eye pressure increases rapidly. This is called acute angle closure and is considered an eye emergency as your eye pressure can reach extremely high levels. 

graphic showing the development of glaucoma

Secondary glaucoma is related to an underlying medical condition. Types of secondary glaucomas include:

  • Neovascular glaucoma occurs when abnormal blood vessels grow into the angle, interfering with fluid drainage. People with poorly controlled diabetes are at higher risk for this condition. High blood pressure or high cholesterol are other risk factors.
  • Pigmentary glaucoma occurs when pigment from the colored iris flakes off and accumulates in the eye’s drainage system. If enough pigment builds up in the angle, you can develop glaucoma. This condition is more common in men between ages 20 to 50, people with myopia (nearsightedness), and those with a family history.
  • Exfoliative glaucoma is associated with pseudoexfoliative material. These are white, flaky, protein-like deposits in the eye. These deposits can clog the drainage angle, leading to elevated eye pressure. This is the most common type of secondary glaucoma. Exfoliative glaucoma is more likely to affect people over 50 years old and those of Scandinavian or Mediterranean descent. 
  • Uveitic glaucoma is related to chronic eye inflammation called uveitis. Researchers are not entirely sure why uveitis causes elevated eye pressure. Some scientists think uveitis creates scarring and inflammatory cell build-up in the drainage system, preventing fluid from leaving the eye. Uveitis is primarily treated with steroid eye drops, which has a potential side effect of increased eye pressure. Uveitis is often associated with autoimmune disorders such as ankylosing spondylitis and inflammatory bowel disease.
Icon of a stressed eyeball crying

Glaucoma Symptoms

In the earlier stages of the disease, most people do not experience any symptoms. As glaucoma advances, you may experience symptoms such as:

These symptoms refer mainly to chronic glaucomas, such as primary open-angle glaucoma. Symptoms of acute angle-closure glaucoma are more severe and may include:

  • Severe eye pain
  • Foggy or blurry vision
  • Redness of the eye
  • Halos or colors around lights
  • Nausea and vomiting
  • Enlarged pupil

Acute angle closure requires immediate medical attention to lower your eye pressure before your eye suffers permanent damage and vision loss.


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Glaucoma Risk Factors 

Anyone may be at risk for glaucoma. However, these are some factors that increase your risk further:

  • Older age
  • Family history of glaucoma
  • High eye pressure
  • Thin corneas (the clear tissue covering the front of your eye)
  • Large optic nerve size 
  • Migraines
  • Diabetes
  • High blood pressure
  • Previous eye injury or surgery

Keep in mind that having these risk factors does not mean you will likely develop glaucoma. Your eye doctor needs to assess these factors along with other exam findings to determine your overall risk.

Glaucoma Treatment Options

Treatment varies depending on the severity and type of glaucoma you have. Additionally, you will need to address any underlying conditions. For example, a diabetic patient with neovascular glaucoma should ensure their blood sugar is well-controlled. 

It is important to note that there is no cure for glaucoma. The goal of treatment is to preserve vision and slow down glaucoma progression, but you cannot reverse any existing damage to the optic nerve.

Medication 

Medications are the primary form of treatment for most types of glaucoma. Typically, glaucoma medication consists of eye drops that you need to use daily. The drugs work by either increasing the amount of fluid draining out of the eye or reducing the amount of fluid your eye produces. 

A new glaucoma medication that can replace daily eye drops is an implant the surgeon injects into your eye. This implant releases glaucoma medication into your eye over an extended period. If your eye pressure does not respond to eye drops, or if you have acute angle closure, the eye doctor may prescribe oral medication to lower the eye pressure further.

Laser treatments 

These treatments include trabeculoplasty or iridotomy. During a trabeculoplasty, the surgeon uses the laser to treat the drainage angle, helping to increase the amount of fluid flowing out of your eye. An iridotomy uses a laser to create a small hole in the iris. This procedure is performed on people at risk for angle-closure glaucoma. 

Glaucoma surgery 

This surgery involves creating ways for fluid to drain out of your eye. A trabeculectomy forms a fluid channel through the sclera (white part of the eye). Another type of surgery involves glaucoma drainage devices, which are small implants the surgeon places into the eye to drain fluid. 

Minimally invasive glaucoma surgeries involve techniques that are less invasive than the surgeries mentioned above. While they may not be as effective as the other types of procedures, they are considered a safer option.

Common Questions & Concerns 

Understanding glaucoma can be difficult, especially since many people with the condition are symptomless. These are some common concerns regarding glaucoma:

Is Glaucoma Hereditary?

Many forms of glaucoma are hereditary. Several genes influence primary open-angle glaucoma, as opposed to a single gene. Scientists have also identified genes that are associated with exfoliative glaucoma and pigmentary glaucoma. Knowing your family history is a key component in determining your risk level for glaucoma.

How Do Doctors Test for Glaucoma?

Since most people who have glaucoma are asymptomatic, the only way to know you have glaucoma is to have an eye doctor diagnose you. Some of the tests your eye doctor may perform: 
- Measuring your intraocular (eye) pressure
- Examining your optic nerve under the microscope, which may include an eye dilation
- Administering a visual field (peripheral vision) test
- Checking your drainage structure with a special lens called a goniolens
- Imaging your optic nerve tissue using ultrasound-like technology called optical coherence tomography  

Is Glaucoma Cancer?

No, glaucoma is not a type of cancer. However, some eye tumors can damage the drainage structure of the eye, leading to glaucoma.

How Do I Prevent Glaucoma?

There is no particular regimen that can prevent glaucoma. In general, you should practice good health habits such as not smoking, exercising regularly, eating a healthy diet, and controlling your blood sugar and blood pressure. Taking these steps may reduce your risk of glaucoma. Above all, early detection of glaucoma via routine eye exams is the best way to prevent vision loss.

Is Glaucoma Painful?

Most cases of glaucoma are not painful. Many people are not aware they have glaucoma until their eye doctor diagnoses the condition, since they do not have symptoms. The exception is if you have acute angle-closure glaucoma, in which you may experience severe eye pain. 


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Author: Melody Huang, O.D. | UPDATED June 2, 2020
Resources

Kaiser, Peter K., and Neil J. Friedman. The Massachusetts Eye and Ear Infirmary Illustrated Manual of Ophthalmology. Saunders, Elsevier, 2009.

Kreft, D., et al. “Prevalence, Incidence, and Risk Factors of Primary Open-Angle Glaucoma - a Cohort Study Based on Longitudinal Data from a German Public Health Insurance.” BMC Public Health, vol. 19, no. 851, 1 July 2019, doi:10.1186/s12889-019-6935-6.

Meier, Nathan F., et al. “Physical Activity, Cardiorespiratory Fitness, and Incident Glaucoma.” Medicine & Science in Sports & Exercise, vol. 50, no. 11, Nov. 2018, pp. 2253–2258., doi:10.1249/mss.0000000000001692.

Tham, Yih-Chung Y., et al. “Global Prevalence of Glaucoma and Projections of Glaucoma Burden through 2040.” Ophthalmology, vol. 121, no. 11, Nov. 2014, pp. 2081–2090., doi:10.1016/j.ophtha.2014.05.013.

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