Hi,
Those lines suggest either Graphics Driver corruption or failing Graphics Hardware.
Monitor > Cable > Port on Computer > which is either connected to a Graphics Card in a slot on the Motherboard or to Onboard Graphics Hardware which is part of the Motherboard.
Go to either your Computer or Graphics Card Manufacturer's website > look for a Drivers and Download Section > look for your Computer or Graphics Card Model Number > your Operating System > Drivers for it: either Video / Graphics / Chipset (depending on wording there) > download and install the Drivers.
If that does not fix it, it would then appear to be a Graphics Hardware problem.
If a Desktop, either swap your Graphics Card with a good one.
Or if Onboard Graphics , you will have to install a Graphics Card in a slot in the Motherboard to see if that fixes the problem.
Cheers.