Types of Glaucoma: What are the Differences in Causes

You may have heard about the eye condition, glaucoma. But how does it affect one’s eye and vision? Learn about the different types of glaucoma here.

What are the Types of Glaucoma?

There are many types of glaucoma each with different causes and characteristics.

The two main types of glaucoma are characterized by the angle between the colored part of the eye (iris) and the clear outer layer of the eye (cornea). This angle is also where the trabecular meshwork is located. The trabecular meshwork is the tissue responsible for draining the liquid from the eyeball and maintaining normal pressure inside the eyes.

If detected early, almost all forms of glaucoma can be treated with surgery, lasers, and medication to manage symptoms and prevent vision loss. 

Understanding the Angle

In a healthy eye, the angle is open and the trabecular meshwork properly drains the liquid from the eye at the rate at which the liquid is also being produced. 

In glaucoma patients, the drainage system is disrupted or blocked either because there is a clog in the trabecular meshwork or the pathway of the drainage system is damaged. This means that the liquid is not being drained properly leading to an increase in the pressure inside the eyes. 

Types of Glaucoma: Primary Open Angle Glaucoma

Primary open-angle glaucoma (POAG) is the most common form of glaucoma. It accounts for 90% of glaucoma cases. POAG is a progressive disease and often lacks any noticeable symptoms. This is why POAG is dubbed as the “silent thief of sight.”

POAG is characterized by a “normal angle,” so the angle is not blocked or narrow and is open as it should be. However, there is a clog in the trabecular meshwork, causing the eye’s pressure to increase gradually. Because pressure increase is gradual, deterioration is often also gradual and unnoticeable.

In people with POAG, blurring and distortion start in the side vision or peripheral vision. During its early stages, POAG would manifest minor to no symptoms.

Types of Glaucoma: Angle-Closure Glaucoma 

Angle Closure Glaucoma, also called narrow-angle glaucoma, is an uncommon type of glaucoma wherein the angle between the iris and the cornea is closed or too narrow that it blocks or disrupts the normal flow in the eye’s drainage system.

Compared to POAG, angle-closure glaucoma develops relatively quickly and has very noticeable symptoms such as sudden blurry vision, eye redness, vomiting, and severe eye pain. Angle-closure glaucoma can either be acute or chronic.

• Acute Angle Closure Glaucoma. This type of glaucoma has a sudden onset of symptoms known as acute angle-closure attack and is treated as a medical emergency. The rapid increase of pressure inside the eye can cause blindness in a matter of hours. 
• Chronic Angle Closure Glaucoma. This type of glaucoma progresses slowly and does not usually have any symptoms until the person will have an acute-angle closure attack. Around 30% of people with acute angle-closure glaucoma will have an attack. 

Types of Glaucoma: Normal-Tension Glaucoma

Normal-tension glaucoma, also known as low-tension glaucoma, is a type of disease wherein the pressure inside the eye is normal, but there is deterioration and damage in the optic nerve due to decreased blood flow. One out of three patients who are diagnosed with open-angle glaucoma has the low-tension type. 

The cause of normal-tension glaucoma is not yet well understood but it is speculated that this type of glaucoma can be due to medical conditions that impaired blood circulation.  

Just like POAG, normal-tension glaucoma barely manifests any symptoms and only becomes noticeable during its advanced stages. People who have heart problems, low blood pressure, and of Japanese ancestry are prone to having normal-tension glaucoma.

Types of Glaucoma: Secondary Angle Glaucoma

If angle glaucoma is associated with medications or medical conditions, it is now classified as secondary angle glaucoma. Types of secondary angle glaucoma include:

Pseudoexfoliative Glaucoma

A type of open-angle glaucoma caused by fibrillar material detaching from parts of the eye and blocking fluid from draining. This type of glaucoma is common in people of European descent.

Pigmentary Glaucoma

Pigment from the iris gets dislodged causing build up in the eye’s drainage system. Pigment granules can be dislodged from doing physical activities such as jumping and jogging. This type of glaucoma can happen in young people particularly, nearsighted men. 

Traumatic Glaucoma

Glaucoma can occur in people who have eye injuries caused by blunt trauma or eye penetration. If the eye injury has caused impairment in the eye’s drainage system such as inflammation, this can cause the angle to become narrow. This form of glaucoma can occur right after the injury or develop years later. 

Steroid-Induced Glaucoma

This is a type of glaucoma that is caused by medication. Steroid medication can increase intraocular pressure. In cases where the intraocular pressure will last long enough, it can cause glaucoma-related damage to the optic nerve. 

Neovascular glaucoma

This is a severe form of glaucoma that is caused by abnormal growth of new blood vessels in the iris. This disease is common in people with diabetes. 

Uveitic glaucoma

The uvea is the part of the eye that supplies blood to the retina. When the uvea is inflamed, blood flow is reduced causing damage to the optic nerve.

Childhood Glaucoma

In rare cases, children and infants may develop glaucoma. The disease can be due to developmental defects or underlying medical conditions. Childhood glaucoma is categorized based on the age of onset.

• Neonatal Glaucoma – at Birth
• Infantile Glaucoma – Infants aged 1-24 months old
• Late Onset Congenital Glaucoma – Children older than 2 years old

Key Takeaways

There are many types of glaucoma. The two main types are open-angle glaucoma and narrow-angle glaucoma. Glaucoma can also occur as a result of a medical condition or eye injury. The disease can also be induced by some medications. Glaucoma usually happens to older people but it can also happen to adults and children with medical conditions or developmental defects. 

Learn more about Glaucoma here.