The only danger is that you might get a bit of a headache if the optical centres are not in the correct position...or you may go slowly blind from glaucoma without being aware of it [like my local chemist ] because you are not smart enough to get someone to look in your eyes and check the intra-ocular pressures, optic nerves and visual fields every two or three years from the age of about 40 yrs or so .
CASA also prescribes that if they are reading lenses only , they must be 1/2 eye frames and not full sized lenses.
Flopt