20/20/20 rule

This comes from my optometrist, just had my eyes checked and the only problem I have is tired eyes from staring at a computer screen for hours and hours. He told me that I needed to look away from the computer every 20 minutes for at least 20 seconds and look at something 20 feet away. Good advice, so I thought I'd pass it on, our eyes are very important we need to be extremely careful about how we treat them.