Certified Paraoptometric (CPO) Practice Exam 2025

Which measurement indicates the deepest part of the eyewire in multi-focal lenses?

1. Seg height

2. Pupillary distance

3. Vertex distance

4. Temple length

The correct answer is: Seg height

The correct answer is seg height, as it refers specifically to the segment height measurement in multifocal lenses. This measurement indicates the deepest part of the eyewire of the lens, which is crucial for proper fitting. The segment height is measured from the bottom of the lens or the frame to the line where the segment of the multifocal lens is positioned. It ensures that the patient has an unobstructed line of sight through the segment, allowing for effective visual correction at varying distances. The other measurements, while important in the fitting of eyewear, do not directly indicate the position of the deepest part of the eyewire in multifocal lenses. Pupillary distance is essential for aligning the lenses with the patient's pupils, vertex distance refers to the distance from the cornea to the back of the lens, and temple length is related to the arms of the frame that sit over the ears. None of these measurements provide information about the segment height, which is specifically designed for multifocal lens fitting.