For those in the wilderness who may have lost/broken their glasses, and cannot see well, it's fairly simple to make an approximation of a pin-hole occluder out of whatever you have (paper, cardboard, a leaf, etc.).
A pin-hole occluder is basically something with circles of small holes, see: http://en.wikipedia.org/wiki/Pinhole_occluder
Depending on the type of vision problem (mine is blurriness at all distances), the pin-hole occluder can allow you to see what you could not, before. I don't recall why it works, but the results are astonishing, and may help.
Learn to survive in the wilderness.