Low hz (30 or 60) has a greater impact on eye fatigue than 120hz and above for a very simple reason. Blinking. Meaning you can afford to blink more often when playing at say 120hz as opposed to 60hz as you get twice the information in the same time frame and you don't miss as much information for blinking. I found this to be valid for any fast pace game like an fps or racing game where things happen very quickly and you need to pay attention.