I've tried placing the monitor anywhere between 3 and 4 feet away as my desk allows, give or take a few inches. It doesn't really seem to matter. I used all the settings suggested here, including the profile at first. I have not applied the profile since having the system built because I don't feel like it gave me an improvement. I may still use it down the road but it is not a factor when it comes to the eye strain. I've varied brightness between 0 and the recommended 12.5. It doesn't appear to be that either. There is something more that I don't understand going on here I think, and given some comments on this thread I am wondering if I am not using a returned monitor that has voltage problems or something along those lines.
I already am talking to newegg about it given the way it shipped, but I want to explore every option and see what the best course of action is before progressing any further.
Are the lagom inversion tests really messed up? It would be too bad to have to return the monitor over something like that, but if it hurts your eyes it can't be the right monitor for you.
What are you viewing when your eyes start hurting? If it's text, there's probably some setting that can be adjusted that will help. If it's images, I wouldn't know what the problem might be. Hopefully someone else gets here because I know very little about eye strain..