Certainly not exclusively. We have a pretty thorough understanding of vision loss with age, and almost all of it is caused in the optics part of the system (tha

Certainly not exclusively. We have a pretty thorough understanding of vision loss with age, and almost all of it is caused in the optics part of the system (that's why you can compensate with glasses or eye surgery for such a long time), not in the optic nerve or after it. Hearing is pretty similar, no idea about smelling.