If you have eyestrain it's possible you set the screen resolution too high and the refresh rate too low. Check desktop resolution and set it to something lik 70hz, 1280~ first and raise it higher step by step. But 70hz is about standard in making it not too straining.
Just because you CAN set it to 3840 doesnt mean you SHOULD set it so~ Actually, because you can set it to 3840 meaning you can run at 1920 at ease, and you should do so~