Progressive/PAL/No-line bifocal measurement
With the patient gazing straight ahead into the distance, mark the center of the pupil. The distance from the lowest point on the frame to the center of the pupil in millimeters is the fitting height.
Progressive Measurement
Lined Trifocal measurement
With the patient gazing into the distance, mark the lower edge of the pupil. The distance from the lowest point on the frame to the lower edge of the pupil in millimeters is the fitting height.

Lined Bifocal measurement
With the patient gazing into the distance, mark the lower edge of the iris. The distance from the lowest point on the frame to the lower edge of the iris in millimeters is the fitting height.
Bifocal Fitting Height