Contact lens prescriptions and eyeglasses prescriptions are not the same. They are significantly different because eyeglasses lenses are positioned approximately 12 millimeters from your eyes, whereas contact lenses rest directly on the surface of your eyes. If you want to wear both contact lenses and eyeglasses, you will need too separate prescriptions. You can request a copy of your glasses prescription at the conclusion of your comprehensive eye exam. But a contact lens prescription cannot be written by your eye doctor and given to you until he or she performs a contact lens fitting or has access to your previous prescription and has evaluated the fit of your current lenses.
No you can't. Although there is a correlation between the power of the contact lenses and your glasses prescription, there are other details for a contact lens that you have to specify including the make and material, the back curve and the diameter. The only way to obtain a prescription for contact lenses is to have a fitting and trial by a qualified contact lens practitioner or optometrist and then ongoing after care to make sure the lenses are suitable and are safe for your eyes.
No. Eyeglass prescriptions and contact lens prescriptions differ. Eyeglass prescriptions differ in that they do not provide the necessary parameters needed to properly prescribe contact lenses. You must be fitted for contact lenses and the prescription will include contact lens brand name, base curve, and diameter that are not components of an eyeglass prescription.