The retina has veins that carry blood away from the retina (and ultimately back to the lungs and heart for oxygen replenishment and recirculation). Think of streams and rivers: tiny venules (creeks) combine to form streams or small rivers (branch veins) which combine to form one large river (the central vein, the “Mississippi River” of the retina).
For reasons that are not always clear, a blockage can develop in a vein, in either a branch vein or the central vein. Branch vein occlusions tend to happen in people over 45, often with some history of high blood pressure and perhaps diabetes and high cholesterol. Central vein occlusions tend to happen in patients over 60. When vein occlusions happen in patients under 40 we must consider a predisposition to blood clots, and we may send you to a hematologist (blood clotting doctor) for special tests.
These vein occlusions cause blood flow to “back up” into the retina, causing bleeding and swelling within the retina itself. This bleeding and swelling in the retina reduces vision.
We cannot do anything about the occlusion itself. Some exotic treatments, including injecting TPA (“clot buster” medicine) into the vein, dissecting the vein (sheathotomy), and making an incision in the optic nerve (radial optic neurotomy) have been initially greated with great fanfare but have not graduated to the level of widely-used, evidence-based interventions.
Currently, our main interventions for vein occlusions consist of laser and of injections of various types of medicines into the eye. These interventions try to improve the swelling in the retina and thereby stabilize and sometimes improve the vision. In the office we measure the swelling in the retina with the OCT machine.
One last note: patients with central vein occlusions are at significant risk of developing a special glaucoma called Neovascular Glaucoma in the first year after an occlusion. This neovascular glaucoma can take away the remaining vision in the eye and can also make the eye painful. Dr. Dahr may check your eye every 1-2 months for several months to make sure such a glaucoma is not developing. If such a glaucoma starts to develop, scatter laser and/or an injection may be considered. If neovascular glaucoma is caught at an early stage, the need for glaucoma surgery on the eye can often be avoided.