Now rotate eyes up and down for 10 mins and then left to right 10 times without any strain,wait a second and close your eyes with palms, donot touch eyeballs , do it for two minutes.
Do this four to eight times a day, whenever you feel strained and whenever you have free time. it takes a maximum of five minutes, but it will give refreshment to your mind like anything else.
During the nights , go to terrace or any open place, select a star in the sky, and just stare it until you close your eyes for the first time. if you do like this eyesight is not going to increase. it may not be decreased, but surely wont increase :)