A static-free cleaner. No matter how high the resolution of your monitor, your images will still be blurry if they're covered in a layer of dust. All CRT screens produce a static charge that attracts more dust than surrounding surfaces do. Check your monitor's manual for the best cleaning methods, or purchase static-free alcohol wipes to clean that dirty screen. A glare fighter.
Glare is one of the main contributors to eyestrain and headaches.
If you can see reflections from lights and windows on your monitor, you may need an anti-glare device. A hood that extends over the top of the monitor can brighten an image washed out by harsh overhead lights. An anti-glare screen that fits over the front of the monitor can reduce reflections from windows and room lamps.