First of all we see with our brains, not our eyes, and eye-brain manipulation can be amazing. For example, there are contacts that allow one eye to see near and the other far--and the brain makes it work (visual cortex--google it). There are others that have bifocals built-in that move around the eye when you look up or down and the brain will compensate. The fixed focus issue has been discussed lots and no one knows the lasting effect, but we do know--the brain compensates.
The one big issue you have to look out for (especially for kids) is that since each eye is seeing a different image off of a screen, that those images are not farther apart than the distance between normal eye centers. If so, your eyes must diverge out from center and this causes a lot of muscle strain--especially in anyone young, whose head has not fully developed. Some 3D films compensate for this by not allowing the image for distant objects to widen more than 2.5 inches. The distance of your head to the screen makes a difference as well, as this width becomes less noticeable the farther away you are.
The other problem is flickering of shutterglasses, since the right eye and left eye are shut off when the other is on. This can cause a seizure in some people, again especially kids.
And, in the realm of amazing--scientists have done experiments where people wear optical glasses that invert the image to each eye. After several days, the wearers have indicated the images turn right-side up and they can see normally again. When they take the glasses off, the images to each are seen upside down, and they have to go through a couple of days to adjust back to normal--amazing...again, our brains adjust.
http://www.spiritalchemy.com/blog/se...nus-experiment