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# Understanding Pupillary Distance (PD)

Understanding Pupillary Distance (PD)

This measurement is the basic optical measurement to ensure that the center point of the eyes have been pinpointed and applied to the lenses. This is the convergence point of the two pupils for any particular distance.
So for far/distance the convergence point would be at around 20 feet and will be wider than the computer reading distance which is roughly 17" or for reading a book.

• Mono PD, this is where the measurement from the center of one pupil to the center of the face is different from the other. That is, the measurements could be Right :33 Left: 29.
• To find the binocular PD then Mono R + Mono L
• Higher power RX (+-5.00) may need to have mono PD according to some opticians, but it depends on the practitioner.
• Sometimes the PD is written as 33/29.5 this can be combined (62.5) or entered as is.
• If the prescription reads 60/57, then the first number is the distance PD and the second is the reading PD
• As for any changes in the PD measurement up to the age of 20 it will change as the body grows; after that there is no change with age. (Study on PD measurement)
• The average measurement is 60.5 mm
• 95% of Males measure 55-70mm
• 95% of Females measure 53-65mm
• kids measure 41-55mm