Grading of Color Vision Defects

There are three stages in diagnosing color vision defects: identification (screening), classification and grading. There are three grades of color vision defects: mild, medium and strong. A device called an anomaloscope is able to screen, classify and grade color deficiencies; however, these devices are expensive, require specialized training and are used primarily in research labs and universities. Grading color vision defects should only be performed by a trained health care provider.

Instructions

• 1

  Conduct a color vision test to first identify the presence of a color deficiency. The most common tests use Ishihara Plates. These are designed to identify red-green color deficiencies, which is the most common defect. Ishihara Plates are usually comprised of random dots. The subject must identify a number or letter in the pattern of dots based on color differences alone. Additional plate tests can be used to identify blue-yellow deficiencies.

• 2

  Classify the type of color vision defect using pseudoisochromatic plates. These involve sorting a series of color plates in sequence by hue or into groups of grays and colors. These tests can be used to detect the difference between protanopia or deuteranopia (green-green vision defects) and tritanopia (blue-yellow defects).

• 3

  Conduct additional plate arrangement tests for comparison to the first tests, such as the Farnsworth panel D-15 and the Lanthony desaturated test, which has smaller differences in color. Comparing the results from these tests is used in grading the color defect.

• 4

  Compare the results between the different panel arrangement tests to determine if the defect is mild, medium or strong.