I am 38, male, was diagnosed with type 1 diabetes last year, and I have been on insulin twice since then. In between these times, I have been able to control my blood sugars with diet and exercise. When I first started taking insulin last year, my eyesight (which had deteriorated before I was diagnosed), came back to normal (20/20) for a couple of weeks. I am again on insulin since last month and the same thing happened, but again only for a couple of weeks. After that, my eyesight began to deteriorate whether I take insulin or not. Can you please give me an explanation of why this is happening?

First, people with type 1 diabetes cannot control their blood sugar with diet and exercise alone. So, the type of diabetes you have is questionable from your information. It is true that there is a honeymoon period during which insulin may not be needed for a short period for type 1, but for this to occur twice, sounds more like type 2 diabetes.

Secondly, vision can shift with changes in blood sugar. For a given shift in blood sugar (say, high), the vision can become blurry or clear. The same holds true for a shift back to normal blood sugar from high. When the blood sugar is normal, the way you see at that time is your true vision, and it may be blurry. True stability may take several weeks, and during this time, your vision may fluctuate slightly.

Stable consistent normal blood sugar is important for your health. For eyeglasses to be accurate, the vision testing ideally should be done when blood sugars are normal, and the prescribed glasses are only reliable with controlled, stable, normal blood sugar.

In addition, people without diabetes who wear glasses can have “natural” changes in their vision. Therefore, your vision change can be due to blood sugar fluctuations or “natural” or a combination thereof.

CAG