So I have a 21.5" iMac and have never had a problem. Decided to get another monitor to help with the workflow. After about 15 minutes, my eyes were hurting. Been playing with the settings all day and nothing is helping. Acer 23' IPS http://www.amazon.com/Acer-H236HL-bid-23-Inch-Widescreen/dp/B00AZMLIDQ/ref=sr_1_3?ie=UTF8&qid=1403066035&sr=8-3&keywords=acer+23+inch+monitor Any suggestions?