Also please refer to this thread where two users claim eye strain from a Dell UltraSharp:
https://www.reddit.com/r/Monitors/comments/4as1dj/ips_eye_strain_is_this_a_thing/One gets relief from a VA screen. However, they seem to believe it may not be the IPS that is to blame but the backlight that particular Dell uses.
But like I say, he got relief from a VA screen: "i assume its the ips panel as much of a bummer that is... i bought an ultrawide 3440x14400 samsung after that and had 0 issues with eye strain. its a VA panel..though i took it back because of colour banding/dithering/black crush issues."