The first is pretty basic: every few minutes, try blinking your eyes slowly several times, or squeezing them shut to stimulate tear production. This will keep them moist, no need for drops!
The second involves eye rolling, and you can put as much or as little attitude into this as you want. Look left with just your eyeballs, and roll them upwards until you are now looking right. Now go back in the opposite direction. Do this looking down as well. This can be done around every 20 minutes while using a computer, or staring at a TV.
The third exercise just involves finding a spot that is more than 30 feet away and staring at it for 20 seconds. Then find another spot, and repeat. Next, start scanning the distance, moving to and focusing on a different spot for a second or two for about a minute. This will allow those ciliary muscles to relax! You can do this with a spot out of your window. It’s that easy, and can be done about every half hour.
Finally, give your eyes a break every hour or so by cupping your hands over your eyes, so that they are in complete darkness for a minute. This will give them a break from focusing, and will allow them to rehydrate.
See? So, in around 3 minutes for every hour of gaming you do, you can help to keep your eyesight intact, which will not only keep them sharp for gaming, but also the rest of your daily functions!