The CDC just released a report saying that the percentage of adult, non-institutionalized, civilian, diabetics who answer yes to the question "Do you have any difficulty seeing even with glasses" has declined, from almost a fourth, to a sixth.
Here's a fact you probably didn't know: Diabetes increases risk of multiple eye diseases.
Although the eye disease most associated with diabetes is diabetic retinopathy (the majority of people who have had any type of diabetes for at least twenty years have some retinopathy, although only a minority will actually go blind from it), diabetes also significantly increases risk of the other two major causes of eye diseases of adulthood: cataracts and glaucoma. Diabetics are also over represented among people who go blind from strokes or traumatic brain injuries.
There are also syndromes that cause both blindness and diabetes. For example, Wolfram Syndrome. Wolfram Syndrome is a recessive genetic disorder that causes a non-autoimmune type 1 diabetes, with onset in childhood (average age of diabetes onset in Wolfram Syndrome is 6 years). Roughly 1 in a 1000 people with childhood onset type 1 diabetes has Wolfram Syndrome; roughly 1 in 400,000 people is born with Wolfram Syndrome. The gene for Wolfram Syndrome was the first gene found that always causes type 1 diabetes. People with Wolfram's develop type 1 diabetes, but also a whole lot of other things including diabetes insipidus, hearing loss, weakness, atrophy of the eyes, and in adulthood, neurological degeneration that often leads to death. Wolfram Syndrome is probably under diagnosed.
Note: I am referring to the diabetes of Wolfram's as type 1 diabetes because it is caused by an inability to make insulin- the pancreas is the target of the disease, and it does not cause insulinn resistance. Some people prefer to see it as a different sort of diabetes.
Diabetes is also associated more strongly with autoimmune diseases that cause visual impairment, such as Graves' and MS.
Premature babies (who may develop retinopathy of prematurity) are slightly more likely to go on to develop diabetes later, although I don't think it's a very significantly increased risk.
There are some really rare syndromes that increase risk of diabetes and retinitis pigmentosa, but they're not generally related.
Macular degeneration, which is extremely common in old people, is associated with some lifestyle issues that are also associated with type 2 diabetes; despite that, I am not aware of any statistical correlation between the two diseases.