My MacBook Pro Retina display backlight doesn't work The backlight on the display of my MacBook Pro 15 retina early 2013.

I have tried to make it brighter by pressing F2 but it didn't work, and when I bring a light from the back of the display exactly near the Apple logo I can see my login screen.
You can try to reset the SMC by following the steps here.

If that doesn't work it looks like your backlight is broken, and you should ask for a replacement if you still have Apple Care.