moire pattern on screen

This sounds like a failed graphics card. I'd recommend taking the machine to your local Apple Store or AASP to be professionaly diagnosed.

Hello

simple way to try diagnose a visual problem is to take a snapshoot of part of screen you think is defective

- if your visual problem not appear on snapshoot file could be a screen problem

- if your visual problem can be see on snapshoot file could be a vram / mother board / graphic card problem

to take a snapshoot use cmd-shift-3 or cmd-shift-4 , that create file on desktop

second way is to plug an external display see if problem is same or not

HTH

Pierre