You have diabetes
If left untreated or uncontrolled, diabetes causes progressive damage to your nerves. Polyneuropathy, a common form of diabetes nerve damage, can injure the network of nerves in more than one part of the body, including the front layer of the eye, the cornea. This interferes with tear production, causing you to blink less often, which means tears evaporate more easily.
One study found that three quarters of people with both diabetes and nerve damage had dry eyes, versus 44% of people with diabetes, but no nerve problems, and less than 30% of people without diabetes. In all, more than half of all people with diabetes have dry eyes.
Once nerve damage has happened, there’s little you can do about it. The key is to prevent it beforehand is to control your blood sugar, and treat the dry eye with over-the-counter or prescription drops if you develop the condition.