American Board of Opticianry (ABO) Practice Test

What is a distometer used to measure in a spectacle lens?

1. None of the provided options

2. b. Segment

3. c. Wet/dry

4. d. Base curve

The correct answer is: None of the provided options

A distometer is an optical device specifically designed to measure the distance between points on a lens, typically used in the context of spectacle lenses. The main purpose of a distometer is to check the optical parameters of lenses, such as the distance between the optical center of the lenses and other critical measurements required for accurate fitting and prescriptions. In the context of spectacle lenses, the most relevant measurement made with a distometer is the segment height, which is crucial for bifocal or progressive lenses to ensure proper alignment with the wearer's visual line of sight. However, the choices presented do not include that specific measurement, which leads to the possibility that "none of the provided options" is the correct selection. Each of the other choices refers to measurements or characteristics that do not accurately represent what a distometer measures. Segment, wet/dry, and base curve are pertinent to lens design and fitting, but they do not encompass the function of a distometer as primarily used in the optical field. In this case, recognizing that a distometer’s capabilities are not adequately represented in the provided options is key to choosing the correct answer.