Retinal Vein and Artery Occlusions
The Retinal Vascular System
From the moment you open your eyes in the morning to the minute you close them to sleep, your eyes are constantly working, even if you don’t realize it. As one of the busiest parts of the body, the eye requires a steady cycle of oxygen and nutrients coming in through the bloodstream. To support the function of sight, your retinas are supported by a small but complex network of blood vessels consisting of a central artery, a central vein, and many smaller branches. The central artery delivers freshly oxygenated blood with nutrients from the heart, while the central vein sends depleted blood back to the heart so that it can be recycled. The smaller branches deliver and drain the blood to various parts of the eye.
When the central artery, central vein, or one of their branches becomes obstructed or blocked, it is known as a retinal occlusion.
Retinal Vein Occlusions
When the veins that carry depleted blood away from the retina experience an obstruction, it is known as retinal vein occlusion. Occlusions of the retinal veins can result in damaging the ocular blood vessels, hemorrhaging inside the eye, or leaking of fluid into the retina. There are two types of retinal vein occlusion: central retinal vein occlusion (CRVO), which is when the obstruction occurs in the central vein, and branch retinal vein occlusion (BRVO), which is when the obstruction occurs in one of the central vein’s branches.
Retinal Artery Occlusions
When the central artery that carries oxygenated blood and nutrients to the retina becomes obstructed, it is known as a central retinal artery occlusion (CRAO). The branches of the central retinal artery can also become obstructed. When this happens, it’s known as branch retinal artery occlusion (BRAO).
CRAO most commonly occurs in older patients who are between 50 to 70 years old, especially patients who have carotid artery disease, a cardiovascular condition in which deposits of fatty debris known as plaque builds up in the arteries that support blood flow to the head, face, and brain. In most cases, CRAO is caused by blood clots in the carotid artery, also known as thrombosis. However, CRAO can also be caused by an embolism, which is when a blood clot develops in one part of the body and travels to a different part of the body through the bloodstream.
The sudden obstruction of the retina’s central artery can cause a wide range of vision issues, most notably a sudden and painless loss of vision. Patients who experience CRAO may also have difficulties in differentiating light from dark. This vision loss can be permanent and irreversible if not addressed immediately. If you experience a sudden loss of vision, seek out emergency medical care immediately.
Another thing that patients should be aware of is that CRAO can often be a sign of an impending brain stroke, which can cause lifelong disabilities or even death. Getting emergency care for a sudden vision loss may not only save your vision, but also potentially save your life.
Complications of Retinal Vein and Artery Occlusions
Retinal vein and artery occlusions on their own can have a detrimental effect on vision, which can be made worse by several complications.
If a retinal vein or artery occlusion causes hemorrhaging and fluid leaking into the retina, it can cause the macula to swell. This is known as macular edema. When macular edema occurs, it can cause blurry vision, vision loss, or both.
In some cases, because the retinal vascular system is not working properly, the eye attempts to grow new blood vessels to fix the issue. This process is known as neovascularization. However, the new blood vessels are abnormal and don’t function well. Instead of supporting ocular health, they break, leak, and bleed into the vitreous humor. As these substances seep into the vitreous humor and accumulate, they can clump together and cast shadows on the retina. These shadows appear as floaters in our field of vision. In severe cases, neovascularization can lead to retinal detachment.
Vein and artery occlusions can sometimes lead to neovascular glaucoma, which is when abnormal blood vessel growth occurs in the iris (the pigmented tissue of the eye that surrounds the pupil) and the drainage angles of the eye, causing pressure to build up painfully in the eye.
Treatment for Retinal Vein and Artery Occlusions
There are many ways that retinal vein and artery occlusions may be treated, depending on the circumstances. Some of these treatment options include:
- Intraocular injections of anti-vegetative endothelial growth factor (anti-VEGF) medications, which help to inhibit neovascularization complications
- Laser surgery
In some cases, your doctor may recommend a combination of these treatments.
Aside from treatment after the occurrence of a retinal vascular occlusion, it’s often recommended that patients who are at risk take preventative measures to reduce the chances of experiencing a retinal vein or artery occlusion. Patients who are most at risk tend to be older and have an underlying condition, such as:
- Vascular diseases
If you have any of these conditions, talk to your doctor about how you can prevent retinal vascular occlusive diseases.