Your eyes have lots of little blood vessels that help keep them healthy and working properly. Sometimes, however, one of these blood vessels can get blocked, kind of like a traffic jam on the highway.
When this happens in a vessel called the "retinal vein," we call it a retinal vein occlusion. Just like when there's a traffic jam on the highway, things can't get through the blocked blood vessel. This means less blood gets to the part of your eye that the blocked vessel was supplying, and that can cause problems.
People with retinal vein occlusion might notice things like blurry vision, black spots in their vision, or even sudden vision loss.
One important thing to remember is that this isn't something you can just "walk off" like a scraped knee. If you think you might have a retinal vein occlusion, it's important to see your eye doctor as soon as possible. They can help figure out what's going on and how to treat it.