Central Retinal Vein Occlusion


Central Retinal Vein Occlusion, also known as CRVO, describes the condition whereby a blockage occurs in the single vein which carries blood away from the retina at the back of the eye. This causes blood and excess fluid to leak from the vein into the surrounding retinal area, causing damage to the retina which can lead to blurred vision or loss of vision in some cases. There are two main types of CRVO, known as Non-Ischemic and Ischemic CRVO. Non-Ischemic CRVO can often present as a less-severe initial loss of vision, with a greater chance of later recovery of vision. In Ischemic CRVO, the initial vision loss may be more severe, the retina becomes starved of oxygen, leading to significant complications. While less common, the long-term vision loss associated with this form of the condition can be more severe. Central Retinal Vein Occlusion may lead to the development of a number of complications. These include macular oedema (swelling of the macula), high pressure within the eye (glaucoma) and growth of new blood vessels (known as neovascularisation).


This condition causes a very sudden but painless loss of vision. It can progress very rapidly over a number of hours or days. The condition can cause blurred or distorted vision and may also lead to vision loss. By the nature of blockage, all of the vision in the eye can become affected by this condition. Central Retinal Vein Occlusion normally occurs in one eye, however less often, it may occur in both eyes. In some cases, individuals may also notice floaters which appear as dark spots, lines or squiggles in their vision. These floaters are shadows formed by small pieces of blood which leak out of the central retinal vein and float in the vitreous fluid located in front of the retina. The occurrence of sudden, significant reduction in vision and the presence of floaters are symptoms which should not be ignored and require immediate investigation by an eye doctor.


The retina’s blood supply is supported by one main artery and one main vein. Anatomically, they are located side-by-side. The condition is caused by a blockage to the main vein which carries blood and fluid away from the retina. Atherosclerosis in the central retinal artery can press on the vein resulting in narrowing of the vein, causing slowing of blood flow through the vein and eventually stopping flow completely. Central Retinal Vein Occlusion (CRVO) leads to a leakage of the contents of the vein, including blood and fluid, into the retina which can significantly affect vision in the affected eye. There are a number of factors which are thought to increase the risk of Central Retinal Vein Occlusion. These include age (with people over 65 years most commonly affected), high blood pressure and high cholesterol levels, obesity, having glaucoma or raised intraocular pressure. People living with diabetes, blood clotting disorders or those who smoke may also be at a higher risk. Diseases which increase the tendency for blood flow to slow down or diseases which can result in inflammation within veins may also lead to CRVO. In particular, the macula, a region of the retina known for its role in central, detailed and colour vision can swell as a result of the leakage. This is known as macular edema and can cause blurred or distorted vision and may result in vision loss. In some cases of CRVO, the retina can become starved of oxygen (known as ischemia). To try and correct for this, new blood vessels grow to supply the retina with oxygen-filled blood. However, these blood vessels are abnormal in nature and can cause further damage- potentially leading to a condition known as neovascular glaucoma. This is where the abnormal blood vessels increase intraocular pressure which can cause pain and loss of vision.


Central Retinal Vein Occlusion (CRVO) is diagnosed through a number of eye tests which can be performed by a specialist eye doctor. The eye doctor will ask about a person’s medical history, including any family history of eye conditions. Individuals will receive a clinical eye examination of visual acuity where they may be asked to read letters off a chart (Snellen chart). They may also check intraocular pressure and examine visual field. The diagnosis is usually very obvious from the appearance of widening and winding nature (known as tortuosity, having multiple bends in structure) of the retinal veins on the surface of the retina leading to the blocked Central Retinal Vein. The doctor will also be able to see multiple areas of bleeding within the retina by examining the retinal surface with a special instrument, the ophthalmoscope. An individual may receive a number of imaging tests. Information about the condition may be identified using colour or wide-field fundus photography (which essentially takes photos of the back of the eye). Optical coherence tomography (OCT) can also be used to assess the various layers at the back of the eye. Individuals may undergo a fluorescein angiogram. This test uses special photography to examine the circulation of a dye (fluorescein), injected into an arm vein, through the blood vessels at the back of the eye. In addition, the eye doctor may request additional tests to examine overall health. These may include examining cholesterol levels, blood sugar levels and blood pressure. They may also enquire about other health conditions such as cardiovascular disease.


At present, there is no treatment for established Central Retinal Vein Occlusion (CRVO). If CRVO is identified at a very early stage, before total blockage has occurred, lowering of pressure within the eye, using drugs such as Carbonic Anhydrase Inhibitors, may promote better flow through the vein and prevent total blockage. However, there are treatment options for the complications of the condition. In some cases, treatment may not be required immediately and instead the condition will be monitored. Without treatment, some vision may be regained although each individual case may be different. If macular oedema (swelling at the macula caused by leakage of blood from abnormal, leaky blood vessels) develops, the eye doctor may use a treatment known as an anti-VEGF (vascular endothelial growth factor) inhibitor or a steroid injection to control the swelling of the macula which occurs. Anti-VEGF works by stopping a protein which causes the growth of abnormal, leaky blood vessels at the back of the eye, leading to swelling of the macula. This treatment is delivered by means of an injection into the jelly-filled centre of the eye. The same treatment is frequently used for patients with the wet-type of age-related macular degeneration. This is not normally painful, as you will receive an anaesthetic which numbs the area. A number of injections of anti-VEGF may be delivered over time to ensure the treatment works. Another treatment option can be provided using steroids, which works to control the swelling in the macula. Steroids can be delivered by injection of a slow-release form of steroid or by injecting a small device (about the size of a small grain of rice) containing the steroid is delivered by injection into the eye. From this device, the steroid is released steadily into the eye over time. A particular form of laser treatment (known as panretinal photocoagulation) can be used to treat the growth of abnormal, leaky blood vessels which can occur as a complication of the condition. This can also be used to treat cases of high eye pressure caused by the growth of leaky blood vessels. No matter what level of vision a person may have, it is important to look after the eyes. To find out more about what can be done to take care of the eyes on a daily basis, please visit our Tips for Good Eye Health.


Research efforts have actively focused on delivering treatments which can treat the complications of Central Retinal Vein Occlusion (CRVO). These include studies to identify how the anti-VEGF (vascular endothelial growth factor) and steroid treatments work to control swelling and how laser treatment can control the growth of abnormal, leaky blood vessels. Researchers continue to examine these treatments to find more efficient ways of using them. Most notably, researchers are looking to increase the length of time between doses of anti-VEGF treatment whilst delivering optimum levels of benefit. More recently, researchers have investigated new treatments and treatment avenues for the condition and its complications. One such example involves an antibiotic known as minocycline, which is regularly used to treat bacterial infections. Researchers suspect that macular oedema, which can occur as a result of CRVO, may be caused by inflammation. Researchers are now investigating whether this antibiotic may be able to prevent such inflammation and potentially prevent macular oedema. A surgical technique known as retinal vein cannulation with the addition of a tissue plasminogen activator (tPA; which works by breaking down clots in blood vessels) is also being tested for CRVO. This technique will try to flush the blockage out of the vein and clear the blood vessels. Another intervention being tested is Aganirsen (a DNA antisense oligonucleotide) which is designed to target a particular region of RNA (the instruction manual from which proteins are made) involved in the growth of new blood vessels in the eye, known as ocular neovascularisation. This intervention is being examined through topical application, in this case being delivered to the surface of the eye.


Receiving a diagnosis can be overwhelming for anyone, but this is not a journey that you have to make alone. There are many groups and resources available to provide support for people living with Stargardt Disease. Fighting Blindness offers a free and confidential counselling service (Insight Counselling). For further information please contact insight@fightingblindness.ie or call 01 6746496. We also offer support groups for people with a visual impairment to share their feelings and experiences with others facing the same challenges. Please consult the support groups section of our website here to access the latest timings and days for the various support groups we offer. For further information please contact insightgroups@fightingblindness.ie or call 01 6746496.


Féach provides support for parents of children living with sight loss in Ireland. ChildVision is the national education centre for children with sight loss in Ireland. NCBI (National Council for the Blind in Ireland) provides support and services for people living with sight loss in Ireland. Irish Guide Dogs for the blind helps individuals and their families to achieve improved mobility and independence.         Last Updated: 27th March 2019