__________ is considered the usable area of optics in the contact lens.

__________ is considered the usable area of optics in the contact lens.

• A. Optic zone diameter (OZD)
• B. Central optical diameter
• C. Optical zone width
• D. Lens usable diameter

Answer: (A)

In contact lenses, the part that actually provides corrective power is the central region called the optic zone. The usable area of optics is defined by how large that central corrective region is, which is described by the optic zone diameter. This diameter is the measurement that tells you how much of the lens surface contributes to vision, and it should be sized to cover the pupil under different lighting so the eye sees through the corrective material consistently. The other terms aren’t the standard descriptor for this essential dimension, so optic zone diameter is the correct label for the usable optical area.

In contact lenses, the part that actually provides corrective power is the central region called the optic zone. The usable area of optics is defined by how large that central corrective region is, which is described by the optic zone diameter. This diameter is the measurement that tells you how much of the lens surface contributes to vision, and it should be sized to cover the pupil under different lighting so the eye sees through the corrective material consistently. The other terms aren’t the standard descriptor for this essential dimension, so optic zone diameter is the correct label for the usable optical area.