>>154
The biggest difference between the fresnel and the standard type lenses is what people refer to as the "sweetspot".
That area in the middle that is clear, has no distortion, or chromatic aberrations.
In the case of the fresnel lenses this sweet spot has everything to do with focus.
Regardless of how much you move the headset around or adjust IPD all the changes is the focus of the image and how much was clear in the middle.
This is because the ridges on the lens surface are not perfectly transparent from all angles.
Moving one way or another will cause other ridges to become slightly opaque and blurry,
but still maintain the same curvature so they don't distort.
People deal with focusing their eyes every day and at worse the problems most people will feel is eye strain or a headache.

In the case of the standard lenses the focus of the lens is almost non-existent.
Because you are looking through one giant magnifying glass everything is in focus across the whole FOV as long as you are in that sweet spot.
When you move from that sweet spot things start to bend and distort instead of going out of focus.
This is because the lens is still clear, but now you are looking through more or less curvature of the lens as you move it around.
From the ideal center you can look out and everything is straight and completely in focus.
This distortion is hard to compensate for without being able to do pupil tracking to dynamically distort the image to compensate for the lens.
Not to mention that because people don't deal with distortions in their vision like this their brains can interpret it
as something very bad happening which usually includes nausea.
Making people sick is generally very very bad for business.