Its a problem with your screen... could have been caused by external presseure on the sides of the monitor, or the contact of some electric device that has electronic waves on the monitor screen, or could be due to usage and voltage fluctutations...
You cant fix it, I am sorry bro... If you wana get over it, the option is to switch to a monitor, coz if you move into repairing it, then it starts off with a new VDU itself...