If you have diabetes mellitus, your body does not utilize sugar properly. Many years of abnormal blood sugar levels can damage blood vessels in the retina, the visual tissue lining the back wall of the eye. The retina senses light and color which is then interpreted in the brain. The damage to the retinal vessels is known as diabetic retinopathy.
If left untreated, diabetes can lead to blindness, therefore regular eye exams are recommended.