It doesn't require great force to depress a computer key. Be certain your office and desk lighting is correct. If not, change it, if possible. Bad lighting can cause irritating glare. Remind yourself to blink frequently to keep your eyes moist and comfortable while computing and reading.
Eye strain is a common computer user's discomfort.
Instead of laying papers flat, use a document holder next to the screen. Keep your neck as relaxed as possible, your chin slightly down and tucked in, your head straight ahead. If you do much copying, you might consider learning touch typing so that you can remain focused on the copy, and not have to switch back and forth from copy to keyboard, to monitor. If you are involved in graphics, don't strangle your mouse. You'll have as much accuracy when you hold it lightly.