Focus correcting screen With the rapid approach of VR, and being someone who's always needed glasses! I have been curious about this for a while. 
Is it possible to correct the focus of a lens by adjusting the image on a screen. So at present the image is distorted because althought it is perfect on the screen, the intermediate lens (i.e. the one in my eye!) is faulty. Would it be possible to change the screen image to compensate for that lens. 
My intuition tells me it isn't because everything is x distance away, but it would be good to get an actual scientific reason for this, and maybe what it would take to make that work (if it is / would be at all possible) 
 A: 
(image copied with permission from A Framework for Aberration Compensated Displays, by Fu-Chung Huang and Brian A. Barsky)
I looked into this once ... The answer is "Yes!" At least to some extent anyway.
If you know someone's exact vision impairment, and you know the exact distance between their eyes and the screen, then you can warp the display on the screen to compensate for their vision impairment.
...But it won't be perfect -- it will still be a bit blurry. And you have to sacrifice image contrast.
In other words, you can create a funny-looking black-and-white pattern which, through impaired vision, looks like a less-blurry image. That image will not be black-and-white though. It will be "darker-gray-on-lighter-gray". (That's what I mean by "sacrificing image contrast".)
You can learn more about this topic by reading papers like these:
Pre-compensation for high-order aberrations of the human eye using on-screen image deconvolution
A Framework for Aberration Compensated Displays
There is ongoing research to make these systems work even better. Very cool.
A: You can produce a real image, i.e. an image on some physical medium like a screen, that is out-of-focus, but you cannot use any optical system to produce a focussed version of that image on your retina.  The reason is that you lose all phase information when  generating the real image.  Now,  what should be available in any VR system is a perfectly focussed image which is then relayed (i.e. with a lens) to a focal plane at  some specified distance.  By adjusting the lens system, you can essentially add your eyeglasses prescription to the VR default focal length.
There is another way to generate an image on your retina:  use scanning light sources to "write" the image directly.  Again, intermediate optics can set the focal distance for such a system.  
I don't know which of these approaches current VR goggles use.
