It depends on lens material, if it transmits visible light(it must be clear or colorful) you can use it as a visible lens(maybe has some problem). Aberration can be considerable problem that you must take into account.

The focal length can be a little different than originally designed, because of the changes in refraction index.

If the lens is AR coated, this coating will not work properly and the visible light will get reflected - if you have high power system, beware!

Thanks guys for the answers