The four parts of your eyes that diabetes can damage are:

The retina - the lining in the back of the eye that senses light coming in to the eys.

The vitreous - the jelly-like fluid that fillis the back of the eye.

The lens - at the front of the eye it focuses light onto the retina.

The optic nerve - main nerve of the eye to the brain

The retina damages happens slowly, due mostly to the tiny blood vessels in the eye. These vessela can swell, weaken and then clog. Once clogged they will not let enough blood into the eye.  Only a dilated exam will notice the damage at first, no loss of sight will occur in the early stages of the damage. Getting a eye exam once a year is the best preventative measure, along with keeping your blood sugar regulated. Laser treatment is also an option to improve this complication, your eye care professional will advise on the best course.Diabetic retinopathy is the name given to the most common eye problems due to diabetes. 

Eye damage from diabetes can also include cataracts, a cloud over the lens of your eye, and glucoma, pressure to your eyes main nerve.  These damages need professional help as they will need medical drops, surgery, and/or laser treatment to improve these complications.

Some retina damage signs to look for: