A method for providing a contact lens for a patient. According to this method, an optical preform is selected, and a resting position of the optical preform on the patient's eye is determined. An optical feature is also located on a patient's eye. Then, a reference position is located on the surface of the optical preform coincident with the optical feature on the patients eye, when the optical preform is in the resting position. Finally, the optical modification is provided on the optical preform at a location based on the reference position on the optical preform, either by machining the preform itself or by machining a mold that is subsequently used to form the lens.