VR is still in a relatively young stage of its lifespan, and there are still some kinks to work out. A lot of people can simply put the headset on and not worry about any sort of issue, but for others, ocular discomfort or nausea can pose a problem.
Windows Central forum member Kram Devil recently created a thread asking for some advice about dealing with eye pain while using Windows Mixed Reality (WMR). In this case, a migraine came on after only a few minutes inside the headset.
Kram Devil mentions that there are a few potential solutions, like measuring and setting IPD, as well as swapping out the face foam for the type in a Rift or Vive. Since this isn't exactly motion sickness, Kram Devil is holding out hope that there will be a hardware solution.
There are already a few answers that attempt to alleviate Kram Devil's ocular issues, but nothing definite yet. If you've experienced the same issue and have come across a solution, head over to the forum and drop some advice. It would be a shame for VR to be completely abandoned by someone just starting down this road.