https://www.diabetesselfmanagement.com/blog/diabetes-and-your-eyes-more-than-retinopathy/
“According to WebMD, [Blurred vision] could just be a temporary problem that develops rapidly and is caused by high blood sugar levels. High blood sugar causes the lens of the eye to swell, which changes your ability to see. ... Diabetes can also cause blurriness or double vision due to hypoglycemia (low blood glucose).”