I’ve been doing a lot of computer work lately and I ended up with my eyes being tired and causing discomfort across my forehead. It wasn’t pain, it was more like pressure across my eyes and in the area that would be covered by a Lone Ranger mask.
There are tiny muscles that move your eyes left and right, up and down. The muscles that cause the most problems are right above your iris (if you’re looking straight into a mirror), and also on the very outside of your eyeball.
There is a simple technique (don’t do this if you’re wearing contacts) where you close your eyes and then put your fingertips right onto your eyeball. Then GENTLY press in toward the back of your eyeball (only go a little way, just enough to reach the muscle). If it’s in spasm, it will hurt. Stay on the point for about a minute and if you’re on the spasm it will begin to relax. Do the same to the outside of your eye.
You can see how to do these techniques by looking in my book, Treat Yourself to Pain Free Living. It’s easy to treat both of the muscles, but obviously you want to be especially careful to go gently.
It’s so easy to release eye strain. 
Have a great day,
Julie