[Philip Lelyveld comment - I tried it and couldn't see the effect.]
In current "flat" stereoscopic virtual reality headsets, each eye sees only one image. Depth of field is also limited, as the eye is forced to focus on only a single plane. In the real world, we see slightly different perspectives of the same 3D scene at different positions of our eye's pupil, said Gordon Wetzstein, an assistant professor of electrical engineering at Stanford. We also constantly focus on different depths.
The new light-field stereoscope technology – developed by Wetzstein along with researchers Fu-Chung Huang and Kevin Chen – solves that disconnect by creating a sort of hologram for each eye to make the experience more natural. A light field creates multiple, slightly different perspectives over different parts of the same pupil. The result: you can freely move your focus and experience depth in the virtual scene, just as in real life.
See the full story here: http://news.stanford.edu/news/2015/august/virtual-reality-headset-080315.html