Hey Dude...
well it seems u cant wear bifocal lenses...but u can wear glassess....!!
its something to do with the oxygen flow going to ur eyes which gets reduced when u wear lenses .... after a while when the lenses loses moisture and the eyes get dry also the effects are enhanced when u climb....also during rapid decompression there is a chance that the lens might fall out of ur eye. (one more reason y one needs to carry an extra pair of glasses with them)
also to wear normal lenses u need some 1 from dgca to approve them....