#280 Lensometer

The Lensometer, an American Optical trademark, is an instrument used primarily by optometrists and opticians to identify and to verify eyeglass prescriptions. The Lensometer determines the optical characteristics of lenses, such as power or focal length. It can also be used to correctly mount in frames and to properly orient uncut lenses before grinding into finished products. The first Lensometer to be successfully marketed on a commercial scale and widely used was the Wellsworth Lensometer, produced by the American Optical Company (AO) and introduced in 1921. Prior to the Lensometer, optical professionals had no practical method to check if custom-made lenses produced to an individual prescription were of the proper power. In 2008, the Vision Council Lens Technical Committee conducted a study of the accuracy of commonly used devices for measuring lenses available on the market today. They found that modern commercial lensometers are no more accurate than the Wellsworth Lensometer introduced commercially 100 years ago. More than half of all adults wear prescription eyeglasses. This means a significant part of the world’s population wears are product whose accuracy is at least partially due to the Lensometer. If you wear glasses, it’s likely your optometrist used a lensometer to determine their power.

Landmark Location

Southbridge, Massachusetts, USA

Landmark recognition date

March 2023

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