If the lens is damaged you can replace it with a new Paralenz Lens Kit.
To replace the lens do as followed:
1) Unscrew the end-cap to avoid creating a vacuum
2) Unscrew the lens lock ring by rotating it counter clockwise
3) Loosen the front lens carefully with your fingers
4) Apply silicone grease around the o-rings on the new lens
5) Insert the new lens while rotating it slightly (try not to touch the glass with your fingers)
(Watch a video on how to change the lens below)