Stenopeic Lorgnette 1900 | Antique Eye Exam Tool

A Precision Tool for Diagnosing Astigmatism

This stenopeic lorgnette dates to around 1900 and served a very specific diagnostic purpose. Examiners used it to determine the axis of astigmatism during the course of a refraction. No clear consensus exists on who first developed the stenopeic slit lorgnette. However, the instrument was described by Edmund Landolt in 1920, though this example likely dates back to around 1900 based on its construction.

How the Stenopeic Lorgnette Works

At first glance, this instrument resembles an old ophthalmoscope. It has a similar disc-on-handle shape and overall silhouette. Unlike an ophthalmoscope, though, this device carries no mirror. Examiners never used it to view the fundus of the eye. Instead, a slot holds a corrective lens in place during testing. This particular specimen carries a biconvex glass lens with +18 diopters of power, etched directly onto the lens edge for easy reference.

Three Slits for Precise Measurement

The stenopeic lorgnette features three different slits of varying widths. Between these slits sit five small holes of different diameters. Examiners used these holes to narrow the central bundle of light rays reaching the eye. This combination of slits and pinholes let the practitioner isolate specific meridians of the eye, an essential step in diagnosing astigmatism before modern instruments like retinoscopes and autorefractors became standard.

A Rare Diagnostic Instrument

This particular stenopeic lorgnette carries no apparent maker’s mark, which is common for specialized diagnostic tools of this era. Instruments like this rarely survive intact, since many diagnostic tools from this period were eventually replaced by more automated refraction equipment. Collectors interested in the broader history of astigmatism diagnosis may also want to browse our eye exam equipment collection for related instruments from the same period.