Because your not blinking your eyes are drying out, so they make tears to lubricate themselves. You need eye drops from the chemist. Ask for hypro mellose. A few drops keeps your eyes moist so you will see better. This was an old post same subject.
http://www.oople.com/forums/showthread.php?t=18768
If you cant afford the drops then you need a mate to help you moisten your eyes like this
works for me