second2n0ne The fact that incorrect resolution causes eye strain is true. I have to look at different monitors for work.
I didn't delve deeply into the technical details, but the principle is that a pixel is a unit of the screen. When the resolution on the screen (in the game) does not match the resolution of the matrix or is not a multiple of it, the image becomes blurred, and the contrasting edges (for example, of fonts) become blurry. The eyes try to correct this blur by focusing back and forth. They get tired quickly and start to hurt. Or there may be a burning sensation, or itching, it varies for different monitors and eyes.
If Cleartype is enabled, then the resolution unit is not a pixel, but a subpixel (1/3 of a pixel). I don't know if it works in Heroes (DirectX). Sometimes turning off Cleartype helped with eye pain, and sometimes, on the contrary, turning it on.
If the resolution is slightly off from being a multiple of the matrix resolution, it is not noticeable. But ideally, it is better if it matches exactly.