It blinds 400 Canadians every year. Poorly regulated and high levels of sugar in the blood can cause changes in the optics of the eye, resulting in blurred vision and changes in eyeglass prescriptions. The condition may also interfere with focusing of the eye. Control of the blood sugar level usually corrects these problems.
Diabetes can also cause cataracts, a clouding of the lens inside the eye that blurs vision.
Diabetes can cause double vision when it affects the nerves that control the alignment and movement of the eyes. It can also cause the optic nerve to be more easily damaged by glaucoma. In the early stages of diabetic retinopathy, called nonproliferative or background retinopathy, small blood vessels weaken and leak fluid or tiny amounts of blood, which distort the retina. At this stage the person may have normal vision or may note blurred or changing vision. Although 25 per cent of people with diabetes have some degree of nonproliferative retinopathy, the condition does not progress to more severe problems in most.