Haussler’s Pupilometer c.1900
Haussler’s Pupilometer is a charming and historically interesting antique interpupillary distance measuring instrument dating to around 1900. It is presented with its original illustrated instruction card. The card is headed “Haussler’s Pupilometer: The Accurate P.D. Measure for Refractive Results” — adding wonderful period charm and provenance to this appealing piece.
What Is Interpupillary Distance?
Interpupillary distance — or P.D. — is the measurement between the centers of the two pupils. It remains fundamental to the correct fitting of spectacles and other optical equipment to this day. Without an accurate P.D. measurement, lenses cannot be correctly centered in front of each eye. Incorrectly centered lenses cause eyestrain, headaches, and poor visual comfort. Learn about interpupillary distance and spectacle fitting.
How Haussler’s Pupilometer Works
The Haussler’s pupilometer featured crosshairs carefully centered over the subject’s pupils. This allowed the examiner to measure the exact distance between them. The P.D. reading was taken from the top scale on the device. Optical lenses correctly positioned in front of each eye allow light to pass through the optical center of the lens. This gives the clearest and most comfortable vision possible.
Price and Significance
When first released, Haussler’s pupilometer carried a retail price of $3.00 — a significant sum at the time. This reflected both the advanced technology of the period and the precision required to manufacture such a finely calibrated instrument. Very few examples survive with their original illustrated instruction cards intact.
Collectibility
This Haussler’s pupilometer is a delightful artifact of early 20th century optometric practice. It is a reminder that the careful science of interpupillary measurement has always been at the heart of good optical dispensing. Complete examples with original cards are increasingly hard to find.
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