Retinal Vascular Occlusion

 When the flow of blood from the retina is blocked, it is often because a blood clot is blocking the retinal vein. This condition is called retinal vein occlusion (RVO). Nerve cells need a constant supply of blood to deliver oxygen and nutrients. Blood vessels provide this supply. In a stroke, a small blood clot blocks the flow of blood through one of the arteries in the brain, and the area that is not getting blood becomes damaged.This same type of damage can happen anywhere in the body. When a retinal vein is blocked, it cannot drain blood from the retina. This leads to hemorrhages (bleeding) and leakage of fluid from the blocked blood vessels. There are two types of RVO:

• Central retinal vein occlusion (CRVO) is the blockage of the main retinal vein.

• Branch retinal vein occlusion (BRVO) is the blockage of one of the smaller branch veins.

• Macular edema: The macula is the small, central area of the retina that allows sharp, detailed vision, such as that necessary for reading. Blood and fluid leaking into the macula cause swelling, a condition called macular edema, which causes blurring and/or loss of vision.

• Neovascularization: RVO can cause the retina to develop new, abnormal blood vessels, a condition called neovascularization. These new vessels may leak blood or fluid into the vitreous, the jellylike substance that fills the inside of the eye. Small spots or clouds, called floaters, may appear in the field of vision. With severe neovascularization, the retina may detach from the back of the eye.

• Neovascular glaucoma: New blood vessels in certain parts of the eye can cause pain and a dangerous increase in pressure inside the eye.

• Blindness: The complications of RVO, especially if they are not treated, can lead to irreversible loss of vision.

Retinal vein occlusion happens when a blood clot blocks the vein. Sometimes it happens because the veins of the eye are too narrow. It is more common in people with diabetes, hypertension, raised  blood cholesterol and homocysteine levels as well as other conditions affecting blood flow.

The symptoms of retinal vein occlusion range from subtle to very obvious. There is painless blurring or loss of vision. It almost always happens in just one eye Retinal vein occlusion often causes permanent damage to the retina and loss of vision. It can also lead to other eye problems.

• Optical Coherence Tomography: This is a high definition image of the retina taken by a scanning ophthalmoscope with a resolution of 5 microns. These images can determine the presence of swelling and edema by measuring the thickness of your retina. The doctor will use OCT images to objectively document the progress of the disease throughout the course of your treatment.

• Ophthalmoscopy: The changes caused by RVO may be seen by examination of the retina with an instrument called an ophthalmoscope.

• Fluorescein angiography: This is a test procedure in which a dye that is injected into a vein in the arm travels to the retinal blood vessels. Special photographs allow the physician to see the vessels.

• Intravitreal injection of anti-vascular endothelial growth factor (VEGF) drugs: These drugs target VEGF, which is an important growth factor that causes macular edema.

• Intravitreal injection of steroid drugs: These drugs combat the inflammatory components which lead to edema.

• Focal laser therapy: This treatment provides lasers to areas of swelling to cause a reduction in edema.

• Pan-retinal photocoagulation therapy: This treatment is used when patients have new blood vessel formation following the retinal vein occlusion.

Return visits are recommended to monitor your disease progress. It is important to detect changes in your condition and formulate treatment plans to prevent or treat complications promptly and maximize visual gain.