Ace the Certified Ophthalmic Assistant Exam 2025 – Eye-Opening Success Awaits!

Pupillary distance is the measurement used to determine the distance between the optical centers of spectacle lenses. It is crucial to ensure that the lenses are aligned properly with the patient's eyes to provide optimal visual acuity and comfort.

The other options:

A. Pupil size: While pupil size is important for certain measurements like determining appropriate frame size in relation to the pupil center, it is not specifically used for determining the distance between optical centers of spectacle lenses.

B. Bridge width: Bridge width is the measurement of the distance between the two lenses at the bridge of the nose. It is not directly related to the distance between the optical centers of the lenses.

C. Lens thickness: Lens thickness is relevant for lens design and prescription, but it does not determine the distance between the optical centers of spectacle lenses.

Therefore, the correct answer is D.