I can't comment on lenses for eyewear, but lenses for cameras is significantly more complex. High end camera lenses use a diverse range of glass through methods

I can't comment on lenses for eyewear, but lenses for cameras is significantly more complex. High end camera lenses use a diverse range of glass through methods such as doping, are polished and have complex anti reflective coatings applied. A modern lens may have a large very strong front element, with a series of smaller fragile elements behind it. Each lens may have a different anti-reflective coating applied. You may be able to 3D print a lens, but at least for high end cameras this technology is going to have very little impact.