There is a line slightly underneath the middle of the screen.

Put the summary of the bug you're having here

What I expected to happen was...:
I expected that my screen would function like normal

What actually happened was...:
I opened my minecraft world and there was a line in my vision.

Steps to Reproduce:
1. I opened the minecraft world.
2. Then I began moving my mouse to look around.
3. Then the line appeared.

4. I tried to restart en reinstall minecraft but the line was still there.