hi just jumping back in - @Dennis has some great information. I have prolific (new blood vessel growth) as well as background (non-prolific) areas of low blood flow on both my retinas.
It was simply explained to me like this: diabetes related small blood vessel damage eventually leads to poor blood flow. When the back of your eye has been without good blood flow, it can sometimes signal and trigger new blood vessel growth. It is these new blood vessels that have deformations and are likely to bleed. The bleeding is what causes blindness as it destroys the nerve cells, similar to splashing acid on delicate circuit boards (optical receptors)
It’s my unqualified observation that when I started taking care of myself, when my swings were minimized by switching to a pump and my standard deviation of blood sugar reading were lowered, that’s when I started growing blood vessels on my left eye. my right eye only has the background or low blood flow damage.
In my case, I ignored my diabetes for many years and I even smoked, causing more damage than would have otherwise been there due to diabetic wear and tear.