Screen Resolution not changeable

Hello and sorry for my bad english,
I have the problem that the original screen resolution of my pc are 1366*768 but in Rohan I can only change between:
1024*768, 1280*720 and 1280*800.
But this setting hurts in my eyes.
My question is: "How I can change the settings to 1366*768?"

And the answer: "Press "O" and you will see towards the top middle and there will be a screen resolution section. Click on the arrow, and you can select your preferred resolution." Doesn't work because 1366*768 are not in this box.
Please help me.

The simple answer is, that you can't change it to that res atm. You'll just have to use whatever works best from the selectable options available, or buy a new monitor.

But I know that it was possible to change the screen resolution to 1366*768 in the past.