Because it will exercise your eyes and can stretch out your neck.
You also should not be sitting like that. That's what is hurting your neck.
Why would I need to do that?
When you go to sit back down, keep your feet flat on the floor and keep your back straight against the chair. Try to keep your head a bit lower than level. Also don't bend your arms so much. You'll feel better- trust me.
Wow, my eyes feel better already..
Now that I've told you, that's my cue to leave. Be safe when you work!