Contact lenses and eyeglass prescriptions significantly differ even though both are aimed toward correcting refractive errors. This is because contacts are worn directly on the eye’s surface while glasses are designed to rest 12 millimeters from the eyes. Consequently, the powers specified for each are different if the best vision is to be attained. Besides, contact lenses have additional specifications not found in eyeglass prescriptions. These include the base curve which is determined by the shape of the cornea, the diameter, lens brand or material, and date of expiry. People who desire to wear both contact lenses and eyeglasses will require two separate prescriptions.