What could cause vision to become blurry while working at computer? he's 45, myopia, no other prob

Eye Dr. can evaluate: People may not blink enough when working with computers or reading books, allowing the corneas to become drier and mildly blur the vision. A diabetic with fluctuating blood sugars can get temporary vision changes. Someone with cataracts can get vision changes as his pupils dilate or constrict in different lighting brightness, depending on where the cataracts are. It could also just be presbyopia.

Probably presbyopia: Myope with full correction at the computer might feel a little presbyopic (loss of accommodation with age starting in the 40s). If the blurriness can be cleared with artificial tears, then dry eye might be component. An eye exam can identify any other causes.

Presbyopia: Presbyopia is the likely culprit, the need for additional correction at near occurs in your 40's. If the patient is a low myope then removing glasses on the computer could help. Otherwise, bifocals or drugstore readers over contacts. Also "computer vision syndrome" can be caused by dryness or even just the need for reducing glare and taking occasional breaks from the monitor.