Central Retinal Vein Occlusion (CRVO)
Central retinal vein occlusion, also known as CRVO, is a condition in which the main vein that drains blood from the retina closes off partially or completely. This can cause blurred vision and other problems with the eye.
Symptoms- Blurry or distorted vision (due to swelling of the center part of the retina, known as the macula)
- Transient visual obscuration (mild symptoms that wax and wane)
- Pain, redness, irritation ( due to severe CRVO and secondary complications such as glaucoma, a disease characterized by increased pressure in the eye)
CRVO develops from a blood clot or reduced blood flow in the central retinal vein that drains the retina. There are many conditions which may increase the risk of blood clots.
Risk factors- Diabetes
- High Blood Pressure
- Deranged Lipid Profile
- Cardio vascular risks
- Low vitamin B12 levels
CRVO is typically a clinical diagnosis—that is, one based on medical signs and patient reported symptoms. When a retina specialist looks into the eye, there is a characteristic pattern of retinal hemorrhages (bleeding) and a diagnosis is made.
Fundus photos and Fluorescein Angiography (FA) is done to distinguish CRVO from conditions that may mimic it, and to assess closure of small blood vessels, or to search for or confirm growth of new abnormal vessels.
Swelling of the center of the retina, called macular edema is common, and to detect this and measure the amount of swelling, an optical coherence tomography (OCT) image is often obtained.
TreatmentIn patients with CRVO, vascular endothelial growth factor (VEGF) is elevated; this leads to swelling as well as new vessels that are prone to bleeding.
Intra-Ocular Injections: The most common treatment, based on results from powerful randomized clinical trials, involves periodic injections into the eye of an anti-VEGF drug to reduce the new blood vessel growth and swelling. Anti-VEGF drugs include bevacizumab (Avastin®), ranibizumab (Lucentis®) and aflibercept (Eylea®). In some cases, steroid injections or implants (Ozurdex) are used.
Although anti-VEGF drugs and steroids reduce the swelling, they are not a cure. As the drug leaves the eye and moves into the bloodstream, the effect in the eye wears off, so re-injection is often needed. A rare lucky patient needs only one injection, but the norm is a series of periodic injections over the course of a few years.
Laser treatment: sometimes additional laser treatment is done to prevent and treat secondary complications.
Types of CRVO- Non-ischemic CRVO — a milder type characterized by leaky retinal vessels with macular edema
- Ischemic CRVO — a more severe type with closed-off small retinal blood vessels
Patients with ischemic CRVO have worse vision with less chance for improvement. They have a tendency for the eye to cause new blood vessels to grow—and in the front of the eye; these new vessels can clog the outflow of normal eye fluids. The eye pressure goes up and glaucoma develops. In the back of the eye, new blood vessels may cause bleeding.