This happened to me as well. I thought I was developing glaucoma or something. Had my eyes checked and they were fine, doctor said maybe some reading glasses might help. They do.
But I later learned that this is a symptom of anxiety:
When we are stressed, our eyes dilate to let in more light. But when they stay dilated due to chronic anxiety then it is hard to focus on fine details because a dilated eye is like a wide-opened aperture on a camera; it lets in lots of light but has a shallow depth of field and can't focus as easily. This is especially noticeable when things are close. This also explains why sometimes things appear more clear than usual, because your eyes are more sensitive to light. It can also cause halos, make you occasionally think you see some light out of the corner of your eye.