Help with computer problem.

[Guardians]

Sooo..i have a little bit of a problem. The problem is that I recently noticed that the left top part of my screen is slightly darker than the right side. The differences is only noticable if you look from far right to far left immediately. I use a Dell all in one Studio One touch screen. Windows 7. How can I fix this or yeah.

screenie:




ps. No i am not blind or w.e lol.