Neovascular glaucoma (NVG) is a form of glaucoma in which new blood vessels close the angle of the eye. The angle of the eye is the angle between the iris and the cornea. The iris is the colored part of the eye and the cornea is the clear layer of cells covering the eye.
NVG is a rare condition that is most prevalent in elderly patients. The treatment for NVG is extremely difficult, but the condition is not life-threatening. Despite this, NVG is considered an emergency due to the possibility of complete blindness if left untreated.
What Causes Neovascular Glaucoma?
There are several different causes of neovascular glaucoma that are well-known. Diabetic retinopathy is one of the most common causes of NVG. NVG is, in fact, an advanced development of diabetic retinopathy. Diabetic retinopathy is a diabetic complication affecting the eyes. Diabetes is the cause of around 33 percent of all cases of NVG, although it is specific to patients who show diabetic retinopathy and not all diabetics.
Another cause of NVG is retinal vascular occlusive diseases. NVG can be a result of ischemic central retinal vein occlusion (CRVO), which is defined by the rapid onset of veins which create a blockage in the eye. Another cause of NVG is ocular ischemic syndrome. Ocular ischemic syndrome is a very serious condition that blinds patients due to a reduction of the blood flow to the eye, although it is uncommon.
Risk factors for these retinal diseases include age, high blood pressure, diabetes, and heart disease. However, for some types of vein occlusion, high eye pressure itself is a risk factor.
Neovascular Glaucoma Signs and Symptoms
The symptoms of neovascular glaucoma depend on the stage of the condition the patient is in. During the advanced stage, symptoms can include acute severe pain, headache, nausea, vomiting, light sensitivity, and reduced visual accuracy. Patients may also present with elevated eye pressure, red eye infection, swelling of the cornea, hyphema (collection or pooling of blood inside the cornea), severe rubeosis (where new blood vessels are found in the iris), retinal neovascularization (formation of new blood cells), and optic nerve cupping (increase in the depression in the middle of the nerve when viewed from the front).
Stages of Neovascular Glaucoma
There are three stages of neovascular glaucoma. The first stage is called rubeosis iridis. It often does not present any symptoms, but some patients report pain, redness, and light sensitivity. The pupils show poor reactivity when tested.
The second stage of neovascular glaucoma is called secondary open-angle glaucoma. In this stage, pain, redness, light sensitivity, and headaches are consistently present. The pupils are still poorly reactive in this second stage.
The third stage of neovascular glaucoma is referred to as secondary angle closure glaucoma. Symptoms in this stage include acute pain, headache, light sensitivity, nausea, and vomiting. Other symptoms include those mentioned above. In this stage, pupil reactions are distorted when tested.
Also read: Primary open-angle glaucoma: Causes, risk factors, and symptoms
How to Diagnose Neovascular Glaucoma
There are several ways to test for neovascular glaucoma. Blood tests may be performed to measure blood sugar levels. Blood sugar is often high in patients with NVG. This also relates to the prevalence of diabetes in patients with NVG. NVG can be associated with carotid artery disease, which is when a blockage or narrowing in the carotid arteries causes a decrease in the blood flow through them. Performing a Doppler study on a patient can determine if carotid artery disease is the cause of the patient’s NVG.
Other testing methods for NVG include:
- Tonometry, which measures intraocular pressure. In patients with NVG, this is usually high.
- Gonioscopy is performed to examine the anterior angle of the anterior chamber in the eye.
- Ophthalmoscopy examination is performed to observe the optic nerve, retina, and posterior chamber.
- A visual field test is performed to evaluate visual field loss.
- Optical coherence tomography is performed to examine high-resolution images of the anterior segment in the eye. This test can help to diagnose glaucoma and abnormality of the retina.
- Scanning laser polarimetry involves the use of polarized light to examine the eye and retinal nerve. An abnormal retinal nerve in the presence of increased intraocular pressure suggests NVG.
- Scanning laser ophthalmoscopy is a microscopic study of the retina and cornea, which helps to diagnose glaucoma and retinal disorders.
Neovascular Glaucoma Treatment and Prevention
The treatment for neovascular glaucoma relies heavily on the underlying cause of the issue. Treating the underlying cause of the condition will usually help to resolve the NVG as well. Other treatments focus on lowering the eye pressure through surgery or medications. Glaucoma drops are often prescribed to help bring down the pressure in the eye causing the NVG. If this course of treatment does not work, a tube shunt may be placed in the eye through surgery, as this will immediately reduce the pressure in the eye.
Due to the retinal ischemia (inadequate blood to the eye), increased pressure in the eye, and the resulting damage to the ocular nerve, visual prognosis is often poor. Prevention of NVG focuses on avoiding developing the most common causes of NVG, including vein blockages in the retina and diabetic retinopathy. In particular, controlling blood pressure and diabetes treatment are the most crucial paths of prevention for NVG. Patients suffering from diabetes who are 65 or older should get an eye exam every one to two years.
Neovascular glaucoma is a rare form of glaucoma caused by the formation of new blood vessels in the retina, blocking vision. The condition is most prevalent in elderly patients, and patients with high blood pressure as well as diabetes are most at risk for developing NVG. The most common symptoms include pain, redness, light sensitivity, headache, nausea, and vomiting. If left untreated, NVG can cause patients to go blind, so it should be treated as a medical emergency.
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