The retina can be compared to the photographic film inside camera. When the focused light hits the retina, a “picture” is taken. Messages about this picture are sent to the brain through the optic nerve.
Degenerations of the retina can occur in young adults and in old age. These may be inherited in some instances. Common diseases like diabetes and high blood pressure can also adversely affect the retina, sometimes leading to blindness. One of the most common retinal condition is retinal detachment. In this condition the retina gets detached from the back wall of the eye rather like peeling wallpaper.
Many sophisticated divices are available to detect glaucoma at very early stages thus preserving good vision.
Diabetic Retinopathy
Diabetes produces weakening of the blood vessel in the body. The tiny delicate retina blood vessels are particularly susceptible. This deterioration of retinal blood vessels, accompanied by structural changes in the retina may go through a series of changes may progress from one to the next.

Diabetic Retinopathy Seminar