AW2725Q, OLED eyestrain?

I just bought the AW2725Q monitor and am primarily using it for photo editing. I know it is designed as a gaming monitor but I want to try HDR image processing and this monitor has gotten good reviews for its HDR output and was a lot cheaper than dedicated 4K HDR photo editing monitors. I've been using it for a couple of days and I seem to be getting a lot more eyestrain than I got with my 2017 5K Retina 27" iMac.  (The old iMac just didn't have the ability to handle intensive photo editing any more.)

Could this eyestrain be due to the HDR? Or to the OLED screen? I've tried turning the brightness down and changing the resolution for larger print and icon sizes, but these didn't seem to help. I am contemplating returning the monitor but wanted to get some input or suggestions before I do so. It seems like a nice monitor and I would really like to keep it if I can.