Certified Ophthalmic Assistant Practice Exam

What measurement determines the distance between the optical centers of spectacle lenses?

1. Pupillary distance

2. Optical distance

3. Inter-pupillary distance

4. Lateral distance

The correct answer is: Pupillary distance

The measurement that determines the distance between the optical centers of spectacle lenses is known as the pupillary distance, often abbreviated as PD. This measurement is crucial for ensuring that the optical centers of the lenses are aligned with the patient's pupils, optimizing visual acuity and comfort. When the lens optics are properly centered over the eyes, it minimizes any potential distortion and ensures that the wearer has the best possible vision through the lenses. Pupillary distance is typically measured in millimeters and is used in the fitting of eyeglasses. The accuracy of this measurement is essential, particularly for those with stronger prescriptions, as misalignment can lead to visual discomfort or blurred vision. It is important for dispensing opticians and ophthalmic assistants to understand and measure this distance correctly. Other terms like optical distance, inter-pupillary distance, and lateral distance may be used informally or in different contexts, but pupillary distance is the specific and correct measurement used to describe the distance between the optical centers of spectacle lenses.