When measuring segment height for a progressive addition lens, which method is correct?

When measuring segment height for a progressive addition lens, the correct method involves measuring from the center of the pupil to the lowest portion of the eyewire. This approach ensures that the visual axis is properly aligned with the progressive lens, which is essential for providing the wearer with optimal vision across different viewing distances.

Measuring from the center of the pupil is critical because it represents the point of focus for most individuals, allowing the lens to perform effectively in providing both distance and near vision. The lowest portion of the eyewire is also significant since it is where the lens construction begins to transition from distance to near vision; therefore, proper measurement ensures that the transition happens at the right point, enhancing the wearer's experience.

This method also takes into consideration the natural positioning of the lenses in relation to the eyes, thereby minimizing any potential for visual disturbances. Using other methods may not accurately capture this alignment, and hence could lead to discomfort or a poor visual experience for the patient.