Retinal Vein Occlusion, or RVO for short, is a condition in the back of the eye where a retinal vein is blocked. Central retinal vein occlusion or CRVO is caused by blockage of the central vein that supplies the eye. Branch retinal vein occlusion or BRVO is caused by a blockage of a branch vein.
Blockage of a vein causes blood to be ‘dammed up’ and fluid leaks out of the vein into the surrounding tissue. This leakage causes swelling or edema of the retina. Edema can damage the retina and lead to loss of vision. RVO usually occurs with sudden and painless loss of vision, but in some cases the condition develops slowly over days or weeks.
It is also possible that the retina suffers a decrease in blood supply at the same time. This is called “ischemic” (from the Greek ‘bloodless’) RVO. In these cases, the retina becomes so “starved” for oxygen that new blood vessels grow in various locations in the eye to improve the insufficient blood supply. Unfortunately these new vessels are in dangerous locations and are fragile and not properly formed leading to a variety of problems including a very dangerous type of blinding glaucoma. Ischemic RVO is therefore considered the more severe form of the disease.
BRVO and CRVO may occur at any age, but the majority of cases are seen in people over 50. Men seem to be affected slightly more often than women. There is no known way of prevention of RVO except by treating the conditions predisposing to blood clots, such as diabetes, high blood pressure, and clotting disorders. Increasing age – another important risk factor – is, unfortunately, untreatable. Patients with retinal vein occlusion require evaluation by their primary care doctor to assess for treatable risk factors.
The most common symptom of RVO is vision loss or blurring in part or all of one eye. The vision loss or blurring is painless and may happen suddenly or become worse over several hours or days. Sometimes there is a sudden and complete loss of vision.
Floaters in your vision may be another symptom of RVO. When retinal blood vessels are not working properly, the retina grows new, fragile vessels that can bleed into the vitreous, the fluid that fills the center of the eye. Blood in the vitreous clumps and is seen as tiny dark spots, or floaters, in the field of vision.
In severe cases of CRVO, the blocked vein may cause painful pressure in the eye. Ischemic CRVO can also cause neovascular glaucoma. This type of glaucoma is caused when abnormal blood vessels begin to grow inside the eye, causing the pressure in the eye to rise. Neovascular glaucoma is a serious condition that can cause pain and lead to severe vision loss. It may take three months or longer after CRVO occurs for neovascular glaucoma to appear.
Treatment of RVO can reduce the risk of permanent vision loss. Early treatment is important because once damage has occurred, the effects are more difficult to reverse.
There are now three different medications used by retina specialists to block the growth of new and leaking blood vessels in patients with RVO. These medications inhibit Vascular Endothelial Growth Factor (VEGF) and therefore are called anti-VEGF agents. VEGF stimulates the growth of new and leaky blood vessels, which contributes to retinal edema. The anti-VEGF medications are given by an intraocular injection administered in the office. All three medications have been studied extensively in thousands of patients and appear to be comparably safe.
Macular edema secondary to RVO is also treated with injections of steroid medications into the eye. These medications reduce the inflammation in the eye that may contribute to the leakiness of blood vessels.
To prepare for an injection, the eye is cleaned with antiseptic solutions and numbed with topical anesthetic gel or an injection of anesthetic into the eye. Injections are administered according to the patient’s response to treatment until the patient’s vision is stabilized and the leaking blood vessels have dried up. Ongoing treatment may be needed to control the disease.
The frequency and number of injections needed varies considerably among patients. The risks of intraocular injections include hemorrhage, retinal tear, and infection, all of which are very rare. The injection of steroid medications may increase the risk of cataract and elevated eye pressure (glaucoma).
Patients should call their doctor if they experience increased pain or decreased vision in the days following an injection as these symptoms could indicate a serious infection.
Thermal laser photocoagulation may be used in patients with macular edema from RVO or in patients with ischemic retinal vein occlusion.
The treatment of macular edema is called Focal Laser Photocoagulation. Focal laser treatment targets the abnormal blood vessels that leak and bleed. Focal laser may be used as adjunctive treatment to anti-VEGF or steroid injections to allow for a longer duration of effect. However, focal laser can destroy surrounding tissue and can therefore only be used on leaking blood vessels outside the center of vision (called the fovea).
(PRP) targets areas of the retina that are not receiving adequate blood flow and are sending signals to create new and abnormal blood vessels. PRP is used to treat patients with ischemic RVO who have certain high-risk characteristics. PRP can help prevent the complication of neovascular glaucoma but will not improve the patient’s vision.