In 1905, Dr. Shinobu Ishihara became a surgeon in the Japanese military. A few years later, however, he shifted his emphasis to ophthalmology, which he researched at the University of Tokyo. By 1910, he was teaching at Japan’s Army Medical College and researching what he called “battlefield ophthalmology.” His goal was to help the army recruit the nation’s most capable soldiers.
A fellow doctor who was colorblind helped Ishihara develop the first charts for what would become the world’s most popular test of color vision deficiency. Known today as the Ishihara Color Test, it began humbly as a series of plates that Ishihara himself hand-painted with watercolors. In accordance with the doctor’s original goal, the test was first used to screen military recruits for color vision abnormalities.
Ishihara published his groundbreaking test in 1917 as a full-fledged University of Tokyo professor. It consisted of circular collections of colored dots of seemingly random sizes. To people with normal vision, one color of dots formed the background while the other formed recognizable symbols. Colorblind test takers would simply see collections of dots; no symbols would be apparent.
A full Ishihara Color Test includes 38 plates; the shorter version contains 24. In fact, it is common for testers to determine a subject’s colorblindness (or lack thereof) after showing just a few plates. The contemporary test features four plate types: transformation (normal and colorblind subjects see different figures), vanishing (only normal subjects see figures), hidden (only colorblind subjects see figures), and diagnostic (plates that help determine the kind and severity of subjects’ colorblindness). Though it is nearly 100 years old, the Ishihara Color Test remains the preferred test for colorblindness around the world.
Several kinds of colorblindness exist; over all, the deficiency is significantly more common in men than in women. Protanopia, which occurs in roughly one percent of men, involves a lack of long-wavelength retinal cones. People with this condition are generally unable to tell green, yellow, and red from one another. In addition, red, orange, and yellow appear unnaturally dimmed.
Individuals with deuteranopia, which also occurs in approximately one percent of men, lack medium-wavelength cones. Green, yellow, and red look the same to them. However, they do not experience an abnormal dimming of these colors. English scientist John Dalton remains perhaps the most famous “deuteranope” in history. Consequently, this deficiency is sometimes called Daltonism.