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.
Astigmatism is caused by an eye that is not completely round. This is one type of refractive error. It is a common eye condition that's easily corrected by eyeglasses, contact lenses, or surgery. Astigmatism is a natural and commonly occurring cause of blurred or distorted vision. However, the real reasons still in not known. Diabetes is people who has high blood sugar. Prolonged high blood glucose are so easy to lead to changes in its shape, which has a deep effect on vision changes. Blurred vision is a common complaint leading to a diabetes diagnosis. While blurry vision is the most common symptom of astigmatism. So you need to take a good treatment options to your diabetes, if you already got it. Diabetes is one of the most diseases among human beings. Also it is one of diseases that is hard to heal. Do not eat too much things which contain high sugar. And take some physical care of eyes and keep eye health to avoid being caused by diabetes.