Is it common for PRK for astigmatism to only last 3 years?

Monovision usually reduces glasses dependence but there are situations at distance or at near where glasses might be needed. The problem with monovision is what works well at age 45 sometimes doesn't work will at age 55 or 60. However, it usually is effective for more than 3 years. Contact lens trials to mimick the intended correction before surgery are instructive by rarely done unfortunately.