An estimated 16.4 million adults are affected by retinal vein occlusion (RVO) (2.5 million due to central retinal vein occlusion and 13.9 million due to branch retinal vein occlusion).
Prior to going into how retinal vein occlusion is detected using an ERG, let's define what retinal vein occlusion is. Retinal vein occlusion occurs when the small vessels that carry blood away from the retina are blocked. As a consequence, the vein now cannot drain blood properly from the retina, resulting in bleeding and fluid leakage onto the retina from the blocked blood vessel, which can cause painless loss of vision. The reason why this can cause painless loss of vision is because it can lead to macular edema.
Macular edema occurs because all the blood that flowed back onto the retina can cause leakage and swelling beneath the macula. The macula is the part of your eye that's responsible for sharp, central vision. And when there's swelling and leakage underneath the macula, then this can result in a decrease in your vision.
A retinal vein occlusion can also result in neovascularization. It means there is new blood vessel growth on the retina. This occurs because of that blocked vein, blood can get to certain areas of the retina, so that area of the retina is deprived of oxygen and nutrients. In response, the body forms new blood vessels in that area. This is problematic because the new blood vessels that form are weak, leaky, and not normal, so they could break, leading to further swelling, and bleeding. It can also lead to eventual retinal detachments in severe cases of vein occlusions.
Generally, vein occlusions affect people with conditions that affect blood flow or people who fail to properly manage these medical conditions. Thus, for example, people who suffer from either diabetes, high blood pressure, or cholesterol, if they're not well managed, they're more likely to develop vein occlusions.
Some patients have subtle symptoms, while others have more obvious symptoms, like blurred vision or complete loss of vision. The vision can deteriorate over the next few hours or days. Vision loss can also occur suddenly in some cases. Typically, the vein occlusions are unilateral, meaning they occur primarily in just one eye.
There are two types of vein occlusion:
What's great about the ERG is it can better allow us to monitor your response to treatment. Typically, the treatment for vein occlusions involves either injecting various different medications into your eyes to stop swelling and stop new blood vessels from growing. We would also use various lasers in your eyes to prevent these weak leaky blood vessels from growing. So the RETeval ERG just better helps us to manage you. We use the OCT to find out about the structure of the retina, and this ERG gives us further information about the function of the retina so that we can manage you better or predict the progression of your vision loss.