Horizontal distorted, scambled lines on laptop screen,but not external screen

[BigDickie]

Hi guys, my macbook pro 13' 2011 has been having major screen issues. I've posted an image below of the startup screen. The issues doesn't resolve and continues onto the home screen. I've attached it to an external monitor and it looked perfect. Any ideas what may be the issue? Thanks

 

[Samuelsan2001]

Screen failing, it's unusual but possible, it could also be a screen connection cable issue.