Over time, increasing in the sugar level in blood will cause the blockage in small blood vessels that nourish the retina, inturn causes blocking off the blood supply. As a consequence, the eye seeks to make new blood vessels expand. These new blood vessels, however, do not form correctly and can quickly leak.
Early diabetic retinopathy- New blood vessels do not develop in this more common form, called nonproliferative diabetic retinopathy (NPDR) (proliferating).
When you have NPDR, the walls of the blood vessels in your retina weaken. Tiny bulges (microaneurysms) protrude from the vessel walls of the smaller vessels, sometimes leaking fluid and blood into the retina. Larger retinal vessels can begin to dilate and become irregular in diameter, as well. NPDR can progress from mild to severe, as more blood vessels become blocked.
Nerve fibers in the retina may begin to swell. Sometimes the central part of the retina (macula) begins to swell (macular edema), a condition that requires treatment.
Advanced diabetic retinopathy- Diabetic retinopathy, known as proliferative diabetic retinopathy, may progress to this more extreme form. Damaged blood vessels close off in this form, allowing new, irregular blood vessels in the retina to expand, which can leak into the translucent, jelly-like fluid that fills the eye core (vitreous).
Scar tissue stimulated by the formation of new blood vessels will gradually cause the retina to disconnect from the back of your eye. When new blood vessels interfere with the regular flow of fluid from the eye, pressure in the eyeball can build up. This will damage the nerve that brings images to your brain (optic nerve) from your retina, resulting in glaucoma.