Maintain Good Posture
You may not realize your posture and eyes are connected, but maintaining the proper sitting position while you work is actually the first line of defense against eye strain.
When you sit down at your computer, make sure your feet are flat on the floor and your wrists are slightly elevated, rather than resting on your keyboard. Your screen should be positioned just below your natural line of sight.
Increase Your Font Size
If you notice yourself squinting to try to read the text on your computer screen, increase your font size. This can reduce some of the stress on your eyes and prevent unnecessary strain.
You can also invest in a bigger monitor, which naturally increases the size of whatever you're working on (If in your budget of course!)