The base curve is vital when fitting a lens. The curve of the lens should fit the curve of the eyeball so it sits properly on the eye. If too flat or too curved, the light will not be focused correctly on the retina.
yes this is very importent, your base curve is what helps the contact fit to your eye and if it is not correct then the contact will move around and cause irritation
The base curve is critical in fitting contact lenses. If you get the wrong base curve, your lenses will move or "flip" on your eyes due to the improper fit.
I think its not critical the base curve when fitting a contact lens as long the lens is made for your and you ask the doctor first before using the contact lense.