This fantastic eye chart — measuring 22 by 28 inches with a positive version on one side and negative on the other — is the work of German optometrist and American Optometric Association member George Mayerle, who was working in San Francisco at end of the nineteenth century, just when optometry was beginning to professionalise.
The chart was a culmination of his many years of practice and, according to Mayerle, its distinctive international angle served also to reflect the diversity and immigration which lay at the heart of the city in which he worked.
At the time it was advertised as “the only chart published that can be used by people of any nationality”. Stephen P. Rice, from the National Library of Medicine explains just how thoroughly thought through the different aspects of the chart were as regards the aim to be as inclusive as possible:
Running through the middle of the chart, the seven vertical panels test for acuity of vision with characters in the Roman alphabet (for English, German, and other European readers) and also in Japanese, Chinese, Russian, and Hebrew.
A panel in the center replaces the alphabetic characters with symbols for children and adults who were illiterate or who could not read any of the other writing systems offered.
Directly above the center panel is a version of the radiant dial that tests for astigmatism.
On either side of that are lines that test the muscular strength of the eyes.
Finally, across the bottom, boxes test for colour vision, a feature intended especially (according to one advertisement) for those working on railroads and steamboats.