Dark eye rings

I suddenly found out that there are dark circles around my eyes. Then I thought, I definitely have enough sleep. I have 9-10 hours of sleep a day. Sometimes I have to drink a little alcohol for me to fall asleep better. 

Then I realised it must have been the ipad mini. I have been using my ipad mini most of the day to play games, up to 6 hours a day. Maybe more. Sometimes my eyes become warm but not bloodshot and the game will remind me to rest lol. 

So I conclude. Prolong usage of phone/ipad or any small screens will strain your eyes and cause dark eye rings.