Eye Material from Content Examples, Displacement texture?

Hello. I have tired to replicate the eye material from Content Examples but I end up with an eye without dilation.

I tried to pick apart the material from the Content Examples and found that the “EyeMidPlaneDisplacement_Example” seemed weird.

I tried to make my own texture, similar to that one. Didn’t work.
I tried to export the “EyeMidPlaneDisplacement_Example” which would be exported as an HDR-file.

I would then import it again, in a separate folder and it would import it as a Cube Map file.
I tried saving it in 32bit EXR-file and imported it that way. That worked but it didn’t make a difference.

Just what kind of file is that one?

Thank you very much!