Glaucoma - Types, Symptoms, Causes & Treatment

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What is Glaucoma?

Glaucoma is an umbrella term for eye diseases that damage the optic nerve (communication pathway between the eye and the brain). Increased intraocular pressure (IOP) causes glaucoma, which eventually damages the optic nerve. This leads to vision loss and blindness if left untreated.

The front part of the eye produces aqueous humor (the clear fluid that nourishes and gives eye shape). Eye fluid travels through the pupil (opening at the center of the eye that allows light to enter) and drains through a drainage angle (trabecular meshwork of canals). If the balance of fluid is off even slightly, eye pressure can increase, causing glaucoma. 

Glaucoma affects about 3 million Americans and is a leading cause of blindness worldwide. It has been called the "silent thief of sight" because there are usually no symptoms until the late stages of the disease.1

There is no cure for glaucoma, but it can be treated and managed to slow progression and prevent vision loss if caught early. Glaucoma is diagnosed during a routine comprehensive eye exam by a licensed ophthalmologist. 

graphic showing the development of glaucoma

Types of Glaucoma

Optic nerve damage caused by an increase in eye pressure can happen in various ways, leading to different types of glaucoma. 

The most common type of glaucoma is primary open-angle glaucoma, which accounts for 74% of all glaucoma cases.3 

Open-Angle Glaucoma

Open-angle glaucoma occurs when the drainage angle is open, but a clog of the trabecular meshwork disrupts the flow of eye fluid. This leads to an increase in eye pressure. 

Many people don’t know they have increased eye pressure until advanced stages of the disease when vision changes bring them to an eye doctor. 

Acute Angle-Closure Glaucoma

Angle-closure glaucoma occurs when the drainage angle is blocked. This blockage causes a sudden spike in eye pressure, resulting in immediate vision changes, such as:

  • Hazy or blurred vision
  • Headache
  • Severe eye pain 
  • Nausea or vomiting
  • Rainbows or halos around light 

Angle-closure glaucoma is a medical emergency and can lead to blindness if not treated early. 

Secondary Glaucoma

Secondary glaucoma is when an underlying medical condition or event causes an increase in IOP. Causes of secondary glaucoma can include:

  • Inflammation
  • Eye injury or blunt force trauma
  • Diabetes complications
  • Certain medications (steroids)

Secondary glaucoma can stem from either open-angle or angle-closure glaucoma. Types of secondary glaucoma include:

  • Steroid-induced glaucoma from the use of steroid eye drops or systemic steroids
  • Trauma-induced glaucoma, which is typically caused by blunt force trauma
  • Uveitic glaucoma, which causes inflammation in the middle layer of the eye
  • Neovascular glaucoma, when newly formed blood vessels cover the drainage angle. It's typically associated with diabetes 
  • Exfoliative glaucoma, which is caused by a flaky material clogging the drainage angle 
  • Pigmentary glaucoma, which is caused by pigment flakes from the iris blocking the drainage system

Childhood Glaucoma

Childhood glaucoma, also called congenital glaucoma, occurs when an infant's drainage canal does not develop properly before birth. It’s typically diagnosed within the first year of life and is often hereditary. This type of glaucoma is rare.

If treated early, children with glaucoma experience minimal vision changes and lead full lives.

Normal-Tension Glaucoma 

Normal-tension glaucoma is also called normal pressure glaucoma or low pressure glaucoma. It’s a form of open-angle glaucoma that damages the optic nerve in the absence of elevated eye pressure. 

Many people with normal-tension glaucoma also experience:

  • Problems with the vascular system (blood vessels)
  • Migraine headaches
  • Cold feet and hands
  • Low blood pressure 
  • Optic nerve hemorrhages 

What Causes Glaucoma?

Glaucoma is caused by fluid build-up in the front of the eye, leading to increased eye pressure in the optic nerve. This high pressure is also called ocular hypertension. However, not everyone with ocular hypertension develops glaucoma.

If left untreated, glaucoma will cause irreversible damage and eventually blindness. People can get glaucoma in one or both eyes.

Anyone can get glaucoma, but certain groups and factors increase the risk. These groups and factors include:

  • Anyone over age 60
  • African Americans over age 40 
  • Family history of glaucoma
  • Diabetes or uncontrolled blood sugar
  • Eye injuries
  • Severe myopia (nearsightedness) 
  • History of steroid use
  • High blood pressure (hypertension)
  • Low blood pressure (hypotension), including people with hypertension who are overtreated with medication
  • Thinner corneas (less than .5 mm)

Symptoms of Glaucoma

Glaucoma typically doesn't have any symptoms until the later stages, when vision starts to change. The first warning signs are blind spots in your peripheral vision (side vision).

Common symptoms of glaucoma include:

When to See an Eye Doctor

Routine comprehensive eye exams are critical in maintaining eye health and catching early warning signs. It’s essential to see an eye doctor if you notice any vision changes, including:

It’s recommended that anyone over 35 at high risk for glaucoma should get an annual eye exam. 

The following are warning signs of a medical emergency. Seek care right away if you experience:

  • Sudden loss of vision in one or both eyes
  • Sudden blurry, hazy, or double vision 
  • Flashes of light
  • Dark spots in your side or central vision 
  • Halos or rainbows around light
  • Severe eye pain

How is Glaucoma Diagnosed?

Glaucoma is diagnosed during a comprehensive eye exam by a licensed ophthalmologist. The exam consists of a series of tests to check the overall health of the eyes. Many exams dilate the pupils. This allows the eye doctor to look at the retina, optic nerve, and the back of the eye. 

Tonometry is another critical eye test that measures intraocular pressure in both eyes. High IOP is a common sign of glaucoma and possible optic nerve damage.

Other tests used to diagnose glaucoma include:

  • Visual acuity test (distance and clarity)
  • Visual field test 
  • Measure corneal thickness
  • Look at the drainage angle 

Treatment Options for Glaucoma

There is no cure for glaucoma, and optic nerve damage is irreversible. However, many glaucoma treatments can help slow the progression of the disease and minimize vision loss.

Medication 

The first goal of treatment is to reduce intraocular pressure to prevent further optic nerve damage. Lowering IOP can be done with prescription eye drops, which will have to be administered for the rest of your life.

Various types of medicated eye drops are available, including:

  • Beta-blockers, which reduce the amount of fluid in the eye, lowering pressure
  • Alpha-adrenergic agonists, which increase outflow and minimize the production of eye fluid
  • Carbonic anhydrase inhibitors, which reduce eye fluid production
  • Miotic or cholinergic agents prostaglandins, which increase eye fluid outflow
  • Prostaglandins, which increase eye fluid outflow

Laser Surgery

Laser therapy is used to treat glaucoma when medications alone do not lower eye pressure. It aims to repair and unblock the drainage angle.

Types of laser therapy used to treat glaucoma include:

  • Trabeculoplasty opens clogged channels in the drainage angle 
  • Iridotomy creates a small hole in the iris (colored part of the eye) to drain eye fluid

Glaucoma Surgery

Glaucoma surgery is necessary when medication and laser treatment don’t work to reduce eye pressure. 

The type of surgery needed depends on the drainage system issue. Options include:

  • Trabeculectomy (filtering surgery), which opens the sclera (white part of the eye) and removes part of the trabecular meshwork to help eye fluid drain freely
  • Drainage implant (tube), which is placed on the sclera (white part of the eye) to help fluid drain out of the eye and reduce eye pressure
  • Cataract surgery replacement of the lens (helps focus light on the retina) can help reduce eye pressure for people with narrow-angle glaucoma. 

Glaucoma Risks and Complications

Glaucoma is a severe eye disease that can lead to vision loss and blindness if not treated. While the condition is typically not life-threatening, it can affect quality of life. 

Because glaucoma can be asymptomatic in the early stages, it’s essential to get routine eye exams. 

Can You Prevent Glaucoma?

While glaucoma can’t be cured or prevented, there are lifestyle changes that can help slow disease progression, including:

  • Annual comprehensive eye exams
  • Exercise 
  • A healthy diet
  • Not smoking
  • Eye protection 
  • Blood sugar and pressure control

Glaucoma Outlook and Prognosis

Catching glaucoma early can slow progression and minimize vision loss and optic nerve damage. People diagnosed with glaucoma will likely use medicated eye drops to maintain normal eye pressure for the rest of their lives. 

Laser therapy and glaucoma surgery can also help minimize vision loss and prevent blindness.

Summary

Glaucoma is an umbrella term for eye diseases that damage the optic nerve. The condition is caused by increased intraocular pressure. It results in vision loss and eventual blindness if not treated early. 

Glaucoma is typically asymptomatic until the advanced stages of the disease. The first warning sign of glaucoma is changes in peripheral vision (side vision). 

Early detection is vital to minimize vision loss and prevent blindness. Glaucoma is diagnosed during an annual comprehensive eye exam. These exams are recommended for anyone experiencing symptoms or with a high risk of developing glaucoma.

10 Cited Research Articles
  1. Don’t let glaucoma steal your sight!” Centers for Disease Control and Prevention. 
  2. Glaucoma: The ‘silent thief of site.’ National Eye Institute 
  3. Kapetanakis, V., Chan, M., Foster, P., Cook, D. “Global variations and time trends in the prevalence of primary open angle glaucoma (POAG): a systematic review and meta-analysis.” British Journal of Ophthalmology, Ltd. 18 Aug. 2015.
  4. Primary open-angle glaucoma.” American Academy of Ophthalmology. 
  5. Angle-closure glaucoma.” American Academy of Ophthalmology. 
  6. Secondary glaucoma.” BrightFocus Foundation. 
  7. Childhood glaucoma.” Glaucoma Research Foundation.
  8. Normal-tension glaucoma.” BrightFocus Foundation. 
  9. Glaucoma.” University of Michigan Kellogg Eye Center 
  10. What is glaucoma? Symptoms, causes, diagnosis, treatment.” American Academy of Ophthalmology. 
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