blacklight

Is there an app to keep it on when I want it to be on? Cuz like I think my light sensor is broken

I have turned the brightness down all the way but the phone is still to bright for me. I have very sensitive eyes and when people call me in the middle of the night and I look over too see it I get blinded. Mayb someone knos of an app or something. This is something my phone company should take...