I'd suggest that you treat the cause instead of the symptom when it comes to strained eyes. Figure out what is causing it and do what you can to remedy it. If it's from the computer, there are glare reducing sheets that you can put over the monitor. They also make special glasses to wear that help with this.
If they're strained from reading small text or any text for long periods of time, try to make the fonts larger. If you're on your computer, you can do this by holding down the CTRL button and either scrolling forward with your mouse wheel or hitting the + key (don't need to use shift even though = is the default when using that key). You can make it smaller by scrolling back or hitting the - key while holding CTRL down.
Also, try turning down the brightness of your monitor. A lot of people have their monitors far too bright without realizing it.
If you want a good, free option check out the program called
f.lux. I swear by it. It keeps my monitor at the proper brightness level and adjusts the tones so that it's far less harsh on my eyes. It adjusts it throughout the day to match the time of day and how bright you need it. It will dim it in the evening, which will actually help you sleep better.
If all else fails, or even before you try any of this, see your optometrist. You could have vision problems and need glasses. Even if you've never needed them before, this stuff can come on over time. If you already have glasses, you might need to have your prescription adjusted for the same reason.
You can always try herbal remedies for relief, but it's best to figure out why you're having strain.