I detached a retina earlier this year and I can attest to the fact that it is no joke. Mine was caused by age and wear not heavy recoil but the end result is the same. I now have a small cabbage that rolls about in my eye with each movement. When target shooting I have to pause and wait for the cabbage to settle down to the bottom of the eye in order to obtain a clear sight picture. I can understand how it would be impossible for a sniper to function with this condition. I will be getting an operation early next year to clear the eye which the optometrist is not keen on. Hopefully all works well.