It appears after a certain amount of on-screen lights are being rendered you get this issue.
It's likely a driver issue (Yes, I saw you discussed how mac don't need drivers, it does, drivers run hardware and software for the computer).
Click on your apple logo, then click Software Update, then update.
If there is an update it should be included with the updates.
Also since you said it started happening recently, have you updated, change operating systems, or done anything could affect how your game runs?
It might be an issue with a compatibility breaking update or something.