The retinal vein is a blood vessel that drains blood from the eye. It consists of a central vein draining into the structures around the eye and a number of smaller branches for collecting blood from the capillaries inside the eye. The corresponding artery, bringing blood to the eye, is known as the retinal artery. Problems with the retinal vein are a very common cause of vision loss. During a routine eye exam, an ophthalmologist will usually check on the structure of the patient's eye to see if there are any problems with the retinal vein or other components of the eye.
Eye anatomy varies slightly from person to person. The retinal vein exits the eye through the optic nerve and may empty into the superior ophthalmic vein or the cavernous sinus, depending on the structure of a person's vascular system. The most common problem with this vein is retinal vein occlusion, where the vein becomes wholly or partially blocked.
In retinal vein occlusion, fluid cannot drain as readily from the eye. This will lead to an increase in pressure inside the eye. Fluid can build up and patients may start to experience vision problems. Persistent high pressure can cause glaucoma, leading to vision loss by damaging structures inside the eye. Sometimes, the patient does not experience pain or discomfort in association with the occlusion. The first sign of a problem may be blurred or changed vision, a sign of vision damage.
In a branch retinal vein occlusion, one of the subsets of the vein has a blockage, but the other branches still drain properly. Pressure will build up more slowly because the eye's drainage system is still functional. When the central retinal vein is the problem, pressure can increase very quickly because no fluid can drain from the eye, while the retinal artery continues to supply nutrient-rich blood to the retina, creating a fluid buildup.
In eye exams, doctors do a pressure test to see if the pressure inside the eye is too high, and they also look into the back of the eye to check for any problems with the retinal artery or vein, optic nerve, retina, and other structures. If the doctor identifies a problem, some follow-up testing to learn more about what is going on and why is necessary so the doctor can develop a treatment plan to address the issue. This may include medications, dietary changes, or surgery, depending on what is happening inside the eye.