Hello,
Yes you can keep it in nightmode. But your eyestrain will reduce only if you take breaks in between.
Every half hour take a few minutes of break, just keep your eyes closed.
Use a lubricant eyedrops available over the counter.
Wash your eyes with cool tap water.
Next Steps
Only if you take breaks and reduce screen time your eyestrain will reduce. we forget to blink when we are staring at the screen.
Health Tips
visit an eye clinic after a few months to check your eye power.