The central vein of the retina draws worn blood from the retina. In rare cases, mostly in middle-aged and old people, this vein, or one of its branches, may be clogged by blood clot. When this happens, the blood and tissue fluid begin to leak out of the clogged vein, causing a blurred vision (after a few hours).
This disorder, called central retinal vein occulsion, is often associated with initial stages of chronic glaucoma simplex or high blood pressure. It is rarely caused by a blood disease in which the blood is clotting faster than normal – e.g. in polycythemia.
As you are young, it is more likely that the leaked blood will be naturally resorbed through the retina wall, and the vision will improve after a few months. If there is no resorption, the vision will be permanently blurred because there is currently no drug for that disorder. Sometimes new blood vessels are created and complications arise. If this occurs on the retina itself, the vessels are fragile and hence prone to rupturing and bleeding, causing a new blur of vision, but this blurred vision can be spontaneously repaired, especially in young people. If the blood vessels are created on the surface of the iris, they can cause a type of glaucoma with complete loss of vision on the affected eye.
Because only a small branch of the vein is blocked in this disorder, a patient may not even be aware of it, but it can be detected by a ophthalmoscope on a routine eye examination. This is a good reason to go to such an inspection. Treating a possible root cause of this disorder – e.g. high blood pressure – can prevent further development of the disease.