The issue you are describing could be related to either the LCD or to the video chip.
In order to figure it out, I would connect an external monitor or beamer to your Macbook Pro and would mirror the picture.
If there are no faults on the picture of the external monitor/beamer, your LCD is defective and needs to be replaced. If there are faults on the picture of the external monitor/beamer, too, your video chip creates the issue.
In case your video chip creates the problem, I would first check the cooling system in your Macbook Pro. Open the Macbook Pro and see if there are all openings free. Is there dust anywhere that you need to remove? Is your cooling fan still running? Just follow this guide.
I hope this helps.