First, these tiny blood vessels swell and weaken. Some blood vessels then become clogged and do not let enough blood through. At first, you might not have any loss of sight from these changes. This is why you need to have a comprehensive eye exam once a year even if your sight seems fine.
As diabetic retinal problems get worse, new blood vessels may grow. These new blood vessels are weak. They break easily and leak blood into the vitreous of your eye. The leaking blood keeps light from reaching the retina.
You may see floating spots or almost total darkness. Sometimes the blood will clear out by itself, but you might need surgery to remove it.
Over the years, the swollen and weak blood vessels can form scar tissue and pull the retina away from the back of the eye. If the retina becomes detached, you may see floating spots or flashing lights.
You may feel as if a curtain has been pulled over part of your vision. A detached retina can cause loss of sight or blindness if you don't take care of it right away.