This 3D animation from The Human Atlas explains the causes and physical effects of Diabetic Retinopathy. 

During normal vision, light passes through the cornea on the outer surface of the eye, and then through the pupil and the lens, focusing on the retina. The retina is a delicate, light-sensitive lining located at the back of the eye.

A person with diabetes can develop damage to the blood vessels that provide nourishment to the retina. When blood vessels in the retina are damaged, they may leak, swell, or develop brush-like branches and extensions. This damage can lead to diabetic retinopathy.

People with diabetic retinopathy may experience blurred vision, blank areas, or glare when in bright light. As the disease develops, cloudy vision, blind spots, and floaters may occur. Floaters are small spots that float across the field of vision.

Left untreated, diabetic retinopathy can lead to blindness. It is important that persons with diabetes get regular eye examinations.