Diabetes is a serious systemic disease typically featured as too high glucose accumulated in blood. Long term of high blood sugar level would lead to stiffening and narrowing of artery. Serious diabetes could lead to various disease of heart, brain, eyes, kidney, nerves and skin. But it won't cause astigmatism. Astigmatism is a refractive error, which is related to the curvature of cornea. It is related to genes. Because the curvature of cornea is not even, the light traveling through the cornea forms multiple focuses on the retina, which makes the vision blurry. So far, I see no clear proof that there is clear consequence between diabetes and astigmatism. Complications from diabetes would be dangerous and people might get blindness from it. But astigmatism is only a refractive error which could be easily corrected by glasses.
