Landolt´s rings, Korean letters and Arabic figures employed as test types in three kinds of international test charts printed in Korea were measured with a micrometer having accuracy of 1/1,000 inches.
It was found that considerable errors of the dimensions compared with the theoretical values of the Landolt´s rings and inequality of the size of the letters between the test charts were present.
These errors will result in an inaccurate determination of, the visual acuity.
The author examined the cognoscibility of the Korean letters, Arabic figures and some pictures in order to determine the standard size of each test type which may enable to design a test chart for accurate visual measurement.
The new Korean test chart for adults composed with Landolt´s rings, Korean letters and Arabic figures, and another test chart for children and illiterates composed with pictures such as airplane, jeep, umbrella, bird, dog, butterfly, and fish were designed with a photographic method.
In these test charts, three horizontal lines for indication, red, green and purple in color, were added between the test types, planning to detect the undiscovered colorblind at the same time of vision test.
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