 Ishihara had just completed his graduate studies in ophthalmology in Germany when war broke out in Europe and World War I had begun.While holding a military position related to his field, he was given the task of creating a color blindness test.Ishihara studied existing tests and combined elements of the Stilling test, named after the German ophthalmologist Jakob Stilling, with the concept of pseudo-isochromaticism to produce an improved, more accurate and easier to use test.