How is an optical prescription for contact lenses different from that for glasses?

An optical prescription for contact lenses is distinct from that for glasses primarily because it includes specifications such as the base curve and diameter. These measurements are critical for the proper fit of contact lenses on the eye, ensuring comfort and optimal vision. The base curve refers to the curvature of the contact lens that closely matches the curvature of the wearer's cornea, while the diameter indicates the width of the lens. Glasses, on the other hand, do not require these specific measurements since they sit away from the eye and do not need to conform to the contours of the cornea.

The other options mention aspects that are not unique to contact lens prescriptions. For instance, while contact lens prescriptions can be formatted differently, the term "different format" is too vague and can refer to various styles of writing prescriptions, not necessarily defining the fundamental differences. A customer signature might be needed generally for any eyewear dispensing but is not specifically related to contact lenses alone. Furthermore, prescriptions for both glasses and contact lenses are typically written for both eyes, depending on the individual's vision needs, so the claim that it is only for one eye is inaccurate.