Modern visits to the eye doctor can feel a bit like being a science experiment. Surrounded by machines that do all manner of things, and asked to do strange rituals (wait, I’m not really sure which one of the lenses is better – show me again?) – all of it can feel very disorienting. Really, though, modern eye science and the devices that come with it are examples of modern scientific marvels. It wasn’t so long ago that the entire ordeal was much simpler, and involved a device called an “optometer.”

In 1619, a scientist named Scheiner found that you could numerically determine just how bad someone’s eyesight was by covering the entire eye except for two spots, inducing double-vision in people needing correction, and then figuring out at what point in front of the eye the object looked single again. While Schiener’s “slit” optometer was the first kind to bear the name (given by W. Porterfield, who put the theory into practice with a sample device), similar mechanisms were invented that simply forewent the slit design. With these, a target was moved back and forth along a ruler placed in front of the eye, and the person being examined simply needed to tell the examiner when the image stopped being blurry.

Still, “optometer” is a name that was used for a great many devices. While many were more quantitative (in that they assigned a value for the poorness of vision), other devices used the name for a much simpler device. Rather than try and determine a number for how bad eyesight was, many clung to the method that has worked for hundreds of years – is this lens better, or that one? Many of these devices took the form of “lens wheels,” large disks with lenses punched out along the edges, which could be tested independently on each side of the eye until vision was “better,” according to the patient. Unlike modern devices, though, which are more properly called “phoropters,” these tools didn’t account for issues with binocular vision and treated each eye completely independently. Still, there is perhaps some comfort in the knowledge that, every time you sweat over if this or that lens is better, you’re participating in a ritual that is very, very old indeed.

Works Cited:

Atchison, David A., and W. Neil Charman. 2010. “Thomas Young’s Contribution to Visual Optics: The Bakerian Lecture ‘On the Mechanism of the Eye.’” Journal of Vision 10 (12): 16. https://doi.org/10.1167/10.12.16.

De Jong, and Paulus T. V. M. 2024. “A History of Visual Acuity Testing and Optotypes.” Eye 38 (1): 13–24. https://doi.org/10.1038/s41433-022-02180-6.

Gurnani, Bharat, and Kirandeep Kaur. 2026. “Autorefractors.” In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK580520/.

Science Museum Group. 1801. “Optometer, Europe, 1801-1900.” PhysicalObject. Science Museum Group Collection. https://collection.sciencemuseumgroup.org.uk/objects/co151988/optometer-europe-1801-1900.