• The following are the requirements for the medical certification of aircrew, including guidance material issued by the UK CAA Medical Department in relation to colour vision.

    Implementing Rules

    Acceptable Means of Compliance

    Guidance Material

    MED.B.075 Colour vision

    (a) Applicants shall be required to demonstrate the ability to perceive readily the colours that are necessary for the safe performance of duties.

    Class 1 and 2
    (a) At revalidation colour vision should be tested on clinical indication.

    Ishihara test to be conducted as per manufacturer’s instructions: test distance 75cm with plane of plates at right angles to line of vision under daylight or daylight simulated light (usually colour temperature around 6500K) allowing 3 seconds per plate for response. The plates should be presented to the applicant in a random order. Ishihara plates should be updated periodically or if showing any signs of fading.
    (b) Examination
    1. Applicants shall pass the Ishihara test for the initial issue of a medical certificate.
    2. Applicants who fail to pass in the Ishihara test shall undergo further colour perception testing to establish whether they are colour safe.
    (b) The Ishihara test (24 plate version) is considered passed if the first 15 plates, presented in a random order, are identified without error.

    Colour Assessment and Diagnosis (CAD) test is required if there are any errors on the first 15 plates.

    Part MED.A.010 defines colour safe as ‘the ability of an applicant to readily distinguish the colours used in air navigation and correctly identify aviation coloured lights.

    CAD tests should be conducted under CAA protocols (available on request). The CAD test will only pass as colour safe, those individuals who perform as well as individuals with colour vision in the normal range on the most difficult aviation colour vision tasks. See CAA papers:

    • CAA Paper 2006/04 Part 1 Minimum Colour Vision Requirements for Flight Crew: The Use of Colour Signals and the Assessment of Colour Vision Requirements in Aviation
    • CAA Paper 2006/04 Part 2 Minimum Colour Vision requirements for Professional Flight Crew: Task Analysis
    • CAA Paper 2009/04 Minimum Colour Vision Requirements for Professional Flight Crew: Recommendations for new colour vision standards.

    For further reading, see CAP 1429 Analysis of European colour vision certification requirements for air traffic control officers.

    Implementing Rules Acceptable Means of Compliance Guidance Material

    (c) In the case of class 1 medical certificates, applicants shall have normal perception of colours or be colour safe. Applicants who fail further colour perception testing shall be assessed as unfit. Applicants for a class 1 medical certificate shall be referred to the licensing authority.

    (c) Those failing the Ishihara test should be examined either by:

    1. Anomaloscopy (Nagel or equivalent). This test is considered passed if the colour match is trichromatic and the matching range is 4 scale units or less; or by
    2. Lantern testing with a Spectrolux, Beyne or Holmes-Wright lantern. This test is considered passed if the applicant passes without error a test with accepted lanterns.
    3. Colour Assessment and Diagnosis (CAD) test. this is considered passed if the threshold is less than 6 SU doe deutan deficiency, or less than 12 SU for protan deficiency. A threshold greater than 2 SU for tritan deficiency indicates an acquired cause which should be investigated.

    The UK CAA does not conduct lantern testing as servicing and output of the machines cannot be quality assured. If the AMS is to consider the result of a lantern test, the report should include clear detail of the protocol used, responses made and documentation of the calibration/maintenance of the equipment. Non-UK tests must have been conducted by an Aeromedical Centre in another Competent Authority.

    Class 1 applicants who fail advanced colour vision testing can request individual assessment by the Authority under MED.B.001 (“issued by the Licensing Authority”) and consideration will be given to restriction of privileges to “valid by day only” and “no public Commercial Air Transport” (VCL + SSL-ILA + SSL-NCAT).

    (d) In the case of class 2 medical certificates, when the applicant does not have satisfactory perception of colours, his/her flying privileges shall be limited to daytime only