Diabetes, a disease that prevents your body from making or using insulin to break down sugar in your bloodstream, can affect your eyes and your vision. Fluctuating or blurring of vision, occasional double vision, loss of peripheral vision and flashes and floaters within the eyes may be symptoms related to diabetes. Sometimes the early signs of diabetes are detected during a thorough eye examination. Diabetes can cause changes in nearsightedness and farsightedness and lead to premature  presbyopia (the inability to focus on close objects). It can result in cataracts, glaucoma, a lack of eye muscle coordination (strabismus) and decreased corneal sensitivity. The most serious eye problem associated with diabetes is diabetic retinopathy, which, if not controlled, can lead to blindness.