Notification of Alternative Means of Compliance

Transcription

1 United Kingdom Civil Aviation Authority Safety Regulation Group Licensing & Training Standards Notification of Alternative Means of Compliance Regulation Reference: COMMISSION REGULATION (EU) No 1178/2011 Annex: IV Part MED Subject: Colour Vision Summary: The advanced methods of colour vision do not include the most reliable, validated test, the Colour Assessment and Diagnosis (CAD) Test, which needs to be included. Implementing Rule: MED B.075 Colour vision 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. (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. (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. (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. Existing Acceptable Means of Compliance: AMC1 MED B.075 Colour vision (a) At revalidation, colour vision should be tested on clinical indication. (b) The Ishihara test (24 plate version) is considered passed if the first 15 plates, presented in a random order, are identified without error. (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, Beynes or Holmes-Wright lantern. This test is considered passed if the applicant passes without error a test with accepted lanterns. Alternative AMC - Colour Vision 1 of 35 October 2012

2 UK Alternative Means of Compliance: Alternative AMC1 MED B.075 Colour vision (a) At revalidation, colour vision should be tested on clinical indication. (b) The Ishihara test (24 plate version) is considered passed if the first 15 plates, presented in a random order, are identified without error. (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, Beynes or Holmes-Wright lantern. This test is considered passed if the applicant passes without error a test with accepted lanterns; or by (3) Colour Assessment and Diagnosis (CAD) Test. This is considered passed if the threshold is less than 6 SU for deutan deficiency, or less than 12 SU for protan deficiency. A threshold greater than 2SU for tritan deficiency indicates an acquired cause which should be investigated. Assessment: Assessed as meeting the Implementing Rule MED.B.075 There is a wide diversity of colour testing methods employed and standards used for the assessment of flight crew colour vision throughout the world, including between European States. Colour vision requirements based on historical lantern tests are open to interpretation, are not reliable and are not appropriate for aviation use. The Colour Assessment and Diagnosis Test developed at the Applied Vision Research Centre at City University, London, UK provides an accurate assessment of an applicant s colour vision and establishes with a high degree of accuracy whether the subject s colour vision meets the requirement to perceive correctly and rapidly the colour of lights involved in aviation colour-critical tasks. The relevant research papers are: 1) 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 standard Further information on the CAD test is in the attached presentation. Approved for submission to the Agency by: Dr Sally Evans, Chief Medical Officer Signature: Date: 14/09/2012 Alternative AMC - Colour Vision 2 of 35 October 2012

3 Colour Assessment and Diagnosis (CAD) Test Sally Evans Chief Medical Officer UK CAA

4 Joint Project UK CAA City University FAA (Part 3)

5 Colour Assessment and Diagnosis (CAD) Test Safety Human rights Applications

6 Scope Background Current tests of colour vision Visual Task Analysis The CAD test Safety critical colour discrimination

7 Background Requirements based on ability to perceive maritime coloured signal lights Absence of information about the specific colour vision needs of flight crew Lack of reliable, standardised tests

8 Colour Vision in Aviation CAA Paper 2006/04 Part 1: The Use of Colour Signals and the Assessment of Colour Vision Requirements in Aviation. click search for publication enter colour vision in search box

9 Current Colour Vision Primary Test Ishihara Plates

10 Current Colour Vision Secondary Tests Nagel Holmes Wright Beyne Spectrolux

11 Problems with Current Tests No test, including Ishihara 1 and anomaloscope, 2 assesses severity of colour vision loss Pass/fail variability (within-subject and inter-subject) is high 1 Lack of standardisation Correlation between outcomes of different tests is poor 1 Do not give reliable information about safe, minimum colour vision for flying 1 Squire TJ, Rodriguez-Carmona M et al (2005). Color vision tests for aviation: comparison of the anomaloscope and three lantern types. Aviat. Space Environ. Med. 76, Barbur JL, Rodriguez-Carmona M et al (2008). A study of unusual Rayleigh matches in deutan deficiency. Visual Neuroscience 25,

12 Terminology Normal trichromat Normal colour vision Deutan Abnormal R/G discrimination M -cone (green) abnormal Protan Abnormal R/G discrimination L -cone (red) abnormal

13 JAR Standard: Ishihara 15 plate Ishihara, no errors No protanope or deuteranope will pass Very small no of deutans will pass Some may be colour unsafe 15% of normal trichromats will fail

14 Secondary Tests: HW Lantern Normal trichromats who failed Ishihara will all pass HW lantern So a mixture of deutans and normal trichromats will pass HW lantern some of deutans may be colour unsafe All protans and some deutans will fail HW, though some may have sufficient chromatic sensitivity to be colour safe

15 Nagel Anomaloscope Does not quantify well the degree of loss of colour sensitivity May not always detect colour deficiency

16 Task Analysis CAA Paper 2006/04 Part 2: Task Analysis. Airbus A321 and Boeing click search for publication enter colour vision in search box

17 Internal Tasks

18 External Tasks

19 Safety Critical Colour Discrimination Tasks Tasks with no redundancy (other cues): PAPI Parking lights (much less hazard) Tasks with more redundancy or that are less demanding in terms of colour perception: Runway threshold, centre-line, lead-off, taxiway, stopway lights Navigation lights Rotating beacons on ground vehicles EFIS, maps, VASIS

20 PAPI Colour perception has to be accurate and fast. Too high Slightly high On slope Slightly low Too low

21 Perception of Colour: the CIE* diagram Yellow-Blue axis Red-Green axis = Normal threshold *CIE (Commission Internationale de L Eclairage) 1931 x,y chromaticity diagram

22 The CAD Test Determines threshold for perception of R/G and Y/B colour signals CAD has 100% specificity and 100% sensitivity for assessing whether an individual has normal colour vision (ie is a normal trichromat or not) CAD can quantify the severity of colour vision loss Cannot be learnt

23 Basis of the CAD Test Uses data that describe statistical limits of colour discrimination in normal trichromats 0.35 Deuteranope Protanope Tritanope 2.5% < P <97.5% "Standard Observer" 0.34 y x

24 Measures Threshold for Colour Perception Uses Dynamic Luminance Contrast Noise ie background contrast changes continuously to mask luminance cues. Can determine threshold for perception of pure colour signal.

25 Methods 1. PAPI 2. PAPI Signal Lights test 3. CAD test 4. Ishihara 5. Dvorine 6. Aviation Lights Test 7. Nagel Anomaloscope Total of 182 participants: color deficient (77 deutan + 40 protan) - 65 normal trichromats - age ranging from yrs G/R W/G G/W G/G R/G W/R W/W R/W R/R Green 546 nm Yellow 589 nm Red 670 nm 2 degrees

26 Laboratory Simulation Schematic representation of optical set-up Four stimulus channels derived from one light source Random luminance variation Viewing distance 4m Visual angle ~1.4 min arc Corresponds to approach distance ~5.54km PAPI test

27 Safety Critical Colour Discrimination CAA Paper 2009/04 Part 3: Minimum Colour Vision requirements for Professional Flight Crew. click search for publication enter colour vision in search box Gives evidence base for new colour vision test and standards for flight crew.

28 Results Normals (n=65) Deutans (n=77) Protans (n=40) PAPI PAPI % correct correct CAD RG threshold units CAD RG threshold units RG threshold (CAD units) CAD RG threshold units

29 Results effect of using a colour-corrected PAPI white Standard WHITE PAPI test PAPI % correct Normals Deutans Protans CC WHITE PAPI test PAPI (% correct) RG thresholds (CAD units)

30 High Levels of Colour Deficiency A few individuals with high level of protanomaly or deuteranomaly passed PAPIs. Not considered colour safe due to very poor chromatic sensitivity likely to affect colour discrimination in other colour related tasks.

31 Minimum Colour Vision Requirements Based on level of colour vision loss below which an individual cannot perform safety critical colour perception tasks with the same accuracy as a normal trichromat = CAD threshold of 6 SN (CAD Units) for Deutans = CAD threshold of 12 SN (CAD Units) for Protans Ie If below these limits the applicant can perform the PAPI test as fast and accurately as a normal trichromat SN = Standard Normal

32 Using the CAD Test Fast-CAD for screening (to replace Ishihara) takes 30 seconds 94% of all applicants will pass and no further testing needed Full-CAD establishes class of colour vision loss and whether pass (colour safe) or fail (colour unsafe). Approx 50% of all colour deficient applicants will pass.

33 CAD Assessment

34 Further Information City Occupational Ltd, Tait Building, C249, Northampton Square, London EC1V 0HB

35 Acknowledgements UK CAA City University, London Qinetiq FAA Federal Aviation Administration