Eye wear prescription, how long is it good for?

Every year or two. Most adults between ages of 20 and 60 will typically need to see if their glasses rx has changed at least every two years, more often if they have symptoms of blurred vision, difficulty seeing road signs, tv, or reading. Children less than 16 should be seen yearly as they are more likely to show rapid changes. Adults after 60 should be seen yearly because of the higher chance of eye diseases.