Routine colour vision testing is carried out when required using the Ishihara test. If the applicant passes, no further testing is required.
If an applicant fails the Ishihara test (please note that the criteria for a pass vary depending on the authority or agency for whom the test is conducted) further colour vision testing may be undertaken:
- CAD test. This is a computer-based test acceptable to the UK CAA for EASA Class 1 and 2 certification, and European Class 3 certification for air traffic control officers. Since May 2023 it has also been accepted by the FAA. Please note that for UK CAA and EASA certification, it is only necessary to pass the test once; for FAA certification the test must be passed at each medical. Please see the FAA Color Vision Guidance for full details. We recommend that applicants arrange comprehensive colour vision testing by Dr Adrian Chorley of Aviation Vision Services, or at City University, London – follow link to “Book an appointment with the AVOT centre”.
- Farnsworth Lantern test. (This is similar to the Holmes-Wright Lantern, which was used by the UK CAA for professional pilots until it was superseded by the CAD test); pairs of coloured lights are displayed, the applicant has to name the colours. It is acceptable to a number of authorities, including the US FAA. We are able to carry out this test, please note that for FAA certification the test must be passed at each medical.
- Trafford anomaloscope: This is a modern electronic anomaloscope, working on the principle of the Nagel anomaloscope; the applicant views a left half of a disc which emits light from a yellow monochromatic LED, and a right half of a disc which emits a light comprising a mixture of red and green. He adjusts the red/green mixture and the brightness of the monochromatic yellow until both halves appear to have identical colour and brightness; the range of red/green mixtures which achieve this (the “matching range”) are noted, this gives an indication of the type of colour vision anomaly. It is of scientific and educational interest, however it is not used for certificatory purposes.