Colour vision test screens for aquired or hereditary colour vision defects. It assesses macular cone and optic nerve function. Refering to Young and Helmholtz´s theory, there are three different types of cones that differ depending on the photopigment they contain. Each of these photopigments has different sensitivity to light of various wavelenghts; therefore they are reffered to as blue, green and red cones. Ishihara colour test is classified as a »gold standard« which tests for green-red deficiency, red-green blindness also known as protanopia. More than 99% people with some kind of colour deficiency suffer from green-red deficiency . Approximatelly 8% of men and 0.5% of women suffer from colour deficiency, because it is a recessive, gender-related trait (encoded on the chromosome X) and therefore the tendency of having it is in favour of male population . Ishihara test is to detect red-green colour deficeincy but not tritan defects. The Hardy-Hand-Rittler (HRR) pseudoisochromatic test also detects tritanopia (blue-yellow shades) . The following test combines both Ishihara and HRR tests so all colour deficiencies may be detected. While a practitioner writes down the test results, in the intervening period the client may fill in the colour test on the electronic device.
Equipment and set-up:
The client wears full correction for near and holds the test at around 40 cm. Test is performed monocularly so one eye must be occluded. The trial frame could also be used. Starting the test the client is asked to identify the sign/mark on the picture and to press the predicted answer.
Interpreting the results:
The application will show the score of how many correct and wrong asnwers the client has got. If the client missed several answers it would show which colour deficiency it might be.