As someone who [sadly] does 12 hour straight marathon gaming sessions in 3D on a 46" 3DTV between 2 and 3ft from my eyes, my initial response to this thread wanted to be Buuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuulllllllllllllllllllllllllllllllllllllllllllllssssssssssssshhhhhhhhhhhhiiiiiiiiiii.................. but much MUCH longer. According to Steam, which keep track of your gameplay, i have about 1500 hours of gaming in 3D. I usually play single player games straight through, like all last Saturday was Mass Effect 3 with no breaks but for food. No eye related anomalies. There is also a surprising lack of eye strain/headache talk on the 3D Vision board -not even one dedicated thread in the 3 years i've been an active member, i certainly can't remember any.