American Board of Opticianry (ABO) Practice Test

What type of PD best compensates for facial asymmetry?

1. Binocular PDB

2. Monocular PD

3. Average PD

4. Segment Height

The correct answer is: Monocular PD

The correct choice for compensating for facial asymmetry in pupillary distance (PD) adjustments often takes into account individual variations in facial structure. A value that is typically used to address significant facial asymmetries is larger than smaller values, such as the one indicated in the correct option. In cases of pronounced facial asymmetry, a larger PD adjustment enables the optical centers of the lenses to align more accurately with the patient’s pupils, leading to better visual comfort and performance. A larger negative value like -7.50 can be used when there is a need to shift optical centers to accommodate the differences in the placement of the eyes, providing optimal lens positioning. Smaller PD adjustments, such as -1.00 or -2.00, might not have the same compensatory effect on symmetry, as they could keep the optical centers closer to the average measurements without effectively addressing significant deviations. Therefore, a higher negative PD value is more appropriate when facial features do not align symmetrically, as it facilitates better visual alignment and ultimately enhances the overall experience for the wearer.