Colorlite Red-Green Color Blind Test
About the red-green color blind test
The goal of this test is to find where the gap is located in the “C shape” (known as a “Landolt Ring”) and to click on it. The test contains three series of images. The first series determines if you have a red-green deficiency. If you do, the second and third series determine which type of red-green deficiency and its severity. The second series contains purple-blue testing images. These determine if you have a red deficiency (protan). The third series contains purple-green images. These determine if you have a green deficiency (deutan). The number of the first image in the second or third series that you cannot distinguish the gap in represents the severity of color deficiency. For example, if you get 14 out of 14 right, you have normal color vision, 1 - 5 right is severe, 6 - 10 is moderate, and 11 or 12 is mild color vision deficiency. Also, if the purple-blue number is greater than the purple-green number than you may have a deutan color deficiency. If the purple-green number is greater than the purple blue number, than you may have a protan color deficiency. If both of these numbers are equal but you have a red-green deficiency (as determined by the first image series) then you may have a deutan color deficiency.
Sensitivity of the red-green color blind test
The maximum score on the test is 14 points for the red-green figures and 9-9 points for the purple-blue (protan) and purple-green (deutan) figures. The number of errors allowed is 3, but only if they are evenly distributed across the three tasks (i.e., red-green 1 error, purple-blue 1 error, purple-green 1 error). In case, there are 2 errors in one task (example red-green), the subject is already diagnosed as color blind. The test has a sensitivity of 98.21%, a specificity of 96.97%, a positive predictive value of 98.21%, and a negative predictive value of 96.97%. Based on our measurements, the online test has the same efficiency (98.21%) as the original Colorlite test book (96.25%), so its efficiency is acceptable. It can be seen that the test detects color blindness and its type with reliable efficiency. The Colorlite red-green online test distinguishes between protan and deutan forms of color blindness with adequate efficiency.