Client/In-Game Flickering Issue

So i played plenty of games all season and never had an issue until now. I decided to play rammus one match instead of my usual champions but I dont think rammus was the trigger or really is the issue as it looks to be a previous issue from a while back. I have a mac on the newest update el capitan or something like that. Basically my screen flickers non top. I looked it up for solutions and i saw some but they didn't work. Only one i didnt try was one that voided my teemo warranty or something like that. I also didnt want to mess up and screw up. So yea i need help. It flickers on client although not much and flickers horribly in game. I can still play but its gonna give me a seizure soon.