Prescription for glasses is different from that for contacts because the contacts are placed on the eyeballs directly while glasses are a little far from eye.So the power of the contacts is slightly less nearsighted than the power of glasses.
Yes, the prescription on your glasses is different to that on your contact lenses. Because eyeglasses are usually about 12 millimeters from the eye while contact lenses are posotioned directly on the tear film of the eye, so the prescription on the contact lenses are less nearsighted.
Yes,you need.The power you need for contacts is usually 0.5 lower than glasses,because the contacts are put directly in your eyes while the glasses are a little far away from your eyes.