Hi and Welcome. My Name is Ashik and I look forward to assisting you today with your question.
I'm sorry to say, but it seems like a hardware issue. This usually happens if there is any problem with the LCD or graphics card. We can try two hardware resets i.e PRAM reset and SMC reset and see if it works or not.
Follow the steps below to reset the SMC (System Management Controller);
- Shut down the computer.
- Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
- On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
- Release all the keys and the power button at the same time.
- Press the power button to turn on the computer.
Follow the steps below to reset the PRAM;
- Shut down your Mac
- Locate the following keys on the keyboard: Command, Option, P, and R.
- Turn on the computer.
- Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears and before the chime sound.
- Hold the keys down until the computer restarts and you hear the startup sound for two or three times.
- Release the keys and let the Mac bootup.
If the SMC and PRAM reset didn't work, then you have to take your Mac to the Apple Store to replace the LCD screen unfortunately. To confirm it is an hardware issue, you can take a screenshot and view the screenshot on another computer or device.
Press Command(Apple) + Shift + 3. This should create a screenshot of your Mac into desktop. Then copy that screenshot to another computer or phone and check if you can see the problem on the screenshot. If not, then we can confirm it is an hardware issue.
If you have any questions or would like any additional information, please don't hesitate to ask.