Question

Common Causes of Errors in using a PD ruler: There will be an error in measurement if the measurer;s PD differs significantly from the subject's because the _______ are not parallel. The above error will be ____ if the PD ruler is not tilted on the subject's nose so the the scale is in the most recessed area. (the most recessed area corresponds to the approximate position where the spectacles will be worn).

Answer 1

Common causes of measurement errors with a PD ruler include differences in PD and improper ruler positioning.

Step-by-step explanation:

The common causes of errors in using a PD (Pupillary Distance) ruler include:

1. Difference in PD measurement between the measurer and the subject, which leads to non-parallel vision axes.
2. Improper positioning of the PD ruler on the subject's nose, resulting in an inaccurate measurement.

To reduce errors, it's important to ensure that the measurer's PD closely matches the subject's PD, and the PD ruler is correctly positioned on the nose at the most recessed area, where spectacles will be worn.