developed a tunnel-like vision. How do i fix it?!

throughout the past year and a half it feels like my ability to focus on something is getting harder and harder. On a computer monitor for example i know i used to be able to see like this: http://i121.photobucket.com/albums/o232/spencermarquardt/tunnelvision2.png . Anything within the circle i could see all at once equally with no problem. Now a days that window of focus is much smaller. Something like this: http://i121.photobucket.com/albums/o232/spencermarquardt/tunnelvision.png . Everything outside of the circle is just blurred out. Its annoying to have to rotate around a screen with my eyes to get the full picture. I know it didnt always used to like this. Is there anyway to reverse it?