Eye strain is a big problem for me, and I get a lot of headaches while playing for a long time, or sometimes even short sessions. Are there any tricks to help? - Natali
There are! But let's get the disclaimer out of the way: if you're having serious headaches, consult a doctor. I am not a doctor, but I do know someone who knows an ophthalmologist, Dr. Michael Hawkeswood, and I consulted with him while writing this. Dr. Hawkeswood is more of a doctor than I'll ever be, because I am not at all a doctor. I am zero percent a doctor.
That settled, the common advice for avoiding eye strain (which Dr. Hawkeswood confirms) is to look away from your display now and then and focus on a distant object. You've got to stretch out those eye-focusing ciliary muscles! (Note: 'stretch out' is probably not the term a doctor would use.) If you're playing a multiplayer game, the easy thing to do is to look away after every match. Study the most distant object in the room, or silently peer out your window, with the bonus effect of creeping out anyone outside.
And while you're stretching your eyeballs, take a look at your lighting situation. It's good idea to keep your room evenly lit while avoiding screen glare as much as possible. You don't want light coming from directly behind your display (I say, with a window behind my desk) or pointed directly at it. And though it's unlikely that you have florescent lights above your desk, avoid those.
Also, remember to blink. It sounds silly, but every eye care provider I've referenced notes reduced blinking as a cause of computer eye strain. Here's the word on it from The Vision Council:
"On average, a person going through his or her daily routine blinks about 18 times per minute. However, spending significant amounts of time staring at a screen causes blink rates to reduce, resulting in dry, itchy or burning eyes."
Eye drops may help, or you could put a Blink-182 poster above your display to remind yourself (may backfire as Mark Hoppus's smirk is known to cause bewildered, unblinking staring).
If just taking eye breaks and reminding yourself that pop punk was a thing isn't helpful, one option is to try a product like Gunnar glasses, which filter artificial blue light and are said to help relax the ciliary muscles. I'm skeptical of all health products marketed to me on the internet, but I know people who swear by them. Ars Technica had a pretty good experience with the glasses, and confirmed with an optometrist that they are beneficial, but also noted that you may be able to find a cheaper pair that does the same thing. Dr. Hawkeswood was more skeptical. I say: if they work for you, that's great! They're at least worth a try if you have constant eye strain problems, though it is a lot of money to spend when better lighting and more breaks may be all you need.
But before buying special glasses, go to an optometrist. You may need corrective lenses, and you should be getting regular check ups anyway (like, more than once every five years, which I have a terrible habit of doing). It doesn't matter if you've had perfect vision your whole life—I can say from experience that my astigmatism has altered my vision into my late 20s.
But assuming your eyes are healthy and you're only experiencing minor headaches (if you're taking medication for headaches more than twice a week, Mayo Clinic suggests that you see a physician), here's one last tip: try f.lux. It isn't exactly designed to alleviate eye strain, but it feels worth mentioning anyway. F.lux is a lightweight program that adjusts the color temperature of your screen according to the time of day, mimicking daylight during the day, and warming it to the temperature indoor lighting at night. It's primarily said to benefit sleep, as recent research suggests that looking at blue light before bed can keep you up, but I find it makes my screen generally easier to look at. It may not help with gaming (you'd want to warm up your display's color settings for that), but I love it when I'm working.
As for gaming alone, here's the recap: keep your room evenly lit (ideally not with florescent lights), but not so bright as to cause glare. Look away from your display every 20 minutes or so and focus on something distant. Don't forget to blink. And see an optometrist—if the optometrist looks blurry, you probably need corrective lenses. Ask the optometrist about that once you find her.