Neovascular Glaucoma: Stages & Treatment

What is Neovascular Glaucoma?

Neovascular glaucoma is an aggressive form of secondary glaucoma. It’s caused by the growth of abnormal blood vessels between the iris and the cornea.

The eye’s drainage angle between the iris and cornea controls the flow of aqueous humor (clear fluid of the eye). Aqueous humor gives the eye its shape and nutrients and controls intraocular pressure (IOP).

Glaucoma is an umbrella term for optic nerve damage caused by elevated IOP. There is no cure for glaucoma. However, early diagnosis and treatment can help slow disease progression. 

Effects of New Blood Vessel Growth on the Eye

New blood vessel growth can cover the eye’s drainage angle, disrupting the flow and drainage of eye fluid through the trabecular meshwork. The trabecular meshwork is the group of connective tissues where aqueous humor flows out of the eye.

A slight change in the filtration rate of eye fluid causes elevated intraocular pressure (IOP). Elevated intraocular pressure can lead to optic nerve damage (the communication pathway between the eye and brain), eventually causing glaucoma.

Factors Affecting Abnormal Blood Vessel Growth

New blood vessel growth can occur when blood flow to the eye decreases. The eye releases vascular endothelial growth factor (VEGF) proteins to compensate for low blood flow. This prompts new blood vessel growth and supplies the eye with more oxygen.

However, you must remember that neovascularization is a complex process. Other factors can also influence the extent and severity of neovascular growth.

These factors include:

• Signaling molecules
• Inflammatory mediators
• Genetic factors

Secondary vs. Primary Glaucoma

Primary glaucoma is the most common type of glaucoma. It typically affects people over 60 and is the second leading cause of blindness worldwide. 

Primary glaucoma can be either open-angle glaucoma or acute angle-closure glaucoma:

• The drainage angle remains open in open-angle glaucoma, but the intraocular pressure (IOP) slowly increases due to a clogged drainage system. This can lead to vision problems over time.³
• Acute angle-closure glaucoma develops when the drainage angle becomes blocked, causing a sudden spike in eye pressure. In this condition, damage to the optic nerve occurs faster than open-angle glaucoma and is a medical emergency.

Secondary glaucoma is characterized by elevated intraocular pressure caused by an underlying medical condition. Neovascular glaucoma is classified as secondary because an underlying medical condition causes elevated intraocular pressure.

What are the Symptoms of Neovascular Glaucoma?

The early stages of the disease are often asymptomatic. However, various symptoms will manifest as the disease progresses.

Recognizing the symptoms of neovascular glaucoma can help you slow down the disease’s progression. 

Symptoms of neovascular glaucoma include the following:

• Vision loss. Vision loss in neovascular glaucoma may range from mild blurry vision to significant loss of sight
• Pain. Pain in the eye may feel sharp, throbbing, or might feel like a constant ache
• Redness. Redness may result from the blood vessels enlarging

Neovascular glaucoma tends to progress quickly. Annual eye exams are essential for people with diabetes and those at risk for neovascular disease.

Neovascular Glaucoma Treatment

There is no direct treatment for neovascular glaucoma. Treatment of neovascular glaucoma includes reducing elevated IOP. 

Common ways to lower IOP include:

• Medicated eye drops. Some eye drops help eye fluid drain from the eye, which then lowers IOP 
• Laser treatment. This treatment is also called pan-retinal photocoagulation. It reduces VEGF secretion, decreasing new blood vessel growth 
• Anti-VEGF eye injections. These injections remove new blood vessel growth so that eye fluid drains properly
• Glaucoma Drainage Devices. These devices can help drain fluid from the eye to reduce elevated IOP

Surgical treatment is necessary when medications alone do not reduce eye pressure. Laser and traditional glaucoma surgery include:

• Tube shunt surgery. Implants a glaucoma drainage device to divert fluid into a reservoir and away from the eye
• Trabeculectomy. Creates a bleb (reservoir) to capture fluid and decrease IOP
• Cyclodestruction. A laser treatment that reduces fluid production  
• Laser iridotomy. Involves creating a small hole in the iris to open the drainage angle 

What Causes Neovascular Glaucoma?

There are various causes of neovascular glaucoma. Some of the most common causes of these conditions include:

Diabetes 

People with diabetes are 50% more likely to develop glaucoma. This disease can lead to further complications, such as proliferative diabetic retinopathy.

With diabetes, high blood sugar diminishes blood vessel integrity and causes them to leak. This decreases blood flow and damages the eye’s vascular system.

Here’s a detailed look into how diabetes compromises the eye’s vascular system:

1. The vascular endothelial growth factor (VEGF) triggers the body to create new, less effective blood vessels
2. These blood vessels cover or clog the drainage angle to promote healing
3. A clogged drainage angle decreases the fluid flow rate
4. Intraocular pressure increases
5. Neovascular glaucoma develops

Annual eye exams and maintaining healthy blood sugar levels are the best ways to prevent secondary glaucoma in people diagnosed with type 1 and type 2 diabetes.³

Ocular Ischemic Syndrome

Ocular Ischemic Syndrome (OIS) is a rare vision-threatening condition that can lead to ocular hypoperfusion. It can result in a blockage of blood vessels in the eye. 

When OIS appears suddenly, it can lead to brief episodes of reduced blood flow and blockage of the eye’s arteries.

Over time, it can also cause problems like retinal damage and the growth of new, abnormal blood vessels.⁹

Chronic Retinal Detachment

People who experience chronic retinal detachment may also develop neovascular glaucoma. Retinal detachment usually results in:

• Retinal capillary obstruction (obstruction of vessels that carry blood away from the eye) 
• Chronic retinal ischemia (restriction of blood supply to the retina)

People who experience these eye problems may experience neovascular glaucoma even after experiencing retinal attachment.

Anterior Segment Neovascularization 

Anterior segment neovascularization is when the front part of the eye has an abnormal growth of blood vessels. It compromises the iris and the cornea and can eventually lead to neovascular glaucoma.

Other common causes of neovascular glaucoma include:

• Tumors
• Central retinal vein occlusion (decreased blood flow to the eye) 
• Ocular inflammatory diseases
• Systemic vascular disorders
• Ischemic retinal diseases
• Peripheral anterior synechiae

Risk Factors for Neovascular Glaucoma

People with systemic vascular disease are at a higher risk of developing neovascular glaucoma triggered by:

• Diabetic retinopathy
• Retinal vein blockage
• High blood pressure
• Heart disease

Controlling high blood sugar and managing heart health help prevent neovascular glaucoma. 

Diagnosing Neovascular Glaucoma

An annual comprehensive eye exam is essential for people with diabetes and vascular disease. Neovascular glaucoma is diagnosed during this exam.

Here’s what you can expect from the exam:

• An ophthalmologist will check for new blood vessel growth, retina damage, and changes in intraocular pressure
• They will assess optic nerve damage by looking at the back of the eye
• They will conduct vision field tests to look for blind spots in peripheral vision (side vision)
• They will conduct visual acuity tests and screen for central and distance vision changes

The first goal of a neovascular glaucoma treatment plan is to reduce eye pressure and prevent further damage to the optic nerve. The second goal is to treat the underlying cause of an ischemic retina (decreased blood flow).

Complications of Neovascular Glaucoma

If not addressed promptly, neovascular glaucoma can lead to various complications, such as:

• Progressive blindness. The main concern of untreated neovascular glaucoma is the progression of vision loss. As IOP continues to rise, damage to the optic nerve continues, leading to a gradual decline in visual acuity
• Corneal edema. Elevated IOP may result in corneal edema (swelling of the eye). This can also lead to cloudy or blurred vision
• Chronic pain. One common symptom of neovascular glaucoma is pain in the eye. When you don’t address this condition, the pain may worsen and lead to chronic pain
• Secondary infections. Failing to manage neovascular glaucoma can make it more prone to secondary infections that threaten your eye health

How to Prevent Neovascular Glaucoma

While there is no cure for glaucoma, patients with neovascular glaucoma can prevent the disease from progressing further. Here are some ways to reduce the risk of the disease:

• Controlling high blood sugar. Diabetic patients must control their blood sugar by reducing carb intake and eating foods high in fiber
• Lowering high blood pressure. You can lower your blood pressure by eating less salt and exercising regularly
• Managing heart disease. Quitting smoking and limiting alcohol intake can lead to a healthy heart
• Eye exams. People with diabetes need regular eye exams to check for any warning signs of glaucoma
• Take medications as prescribed. If diagnosed with diseases that can progress to neovascular glaucoma, taking medications as prescribed is a must

Summary

Neovascular glaucoma is secondary glaucoma caused by new blood vessel growth between the iris and cornea. This leads to a disturbance in fluid rate and elevated intraocular pressure.

Early glaucoma typically doesn’t have many symptoms. However, warning signs of neovascular glaucoma include redness, pain, and vision loss.

Neovascular glaucoma is diagnosed during a comprehensive eye exam. If you have diabetes or are at risk of vascular disease, getting an annual eye exam and glaucoma screening is essential.