United Kingdom Civil Aviation Authority Safety Regulation ...europeancmoforum.com/media/DIR_65301/UK-ColourVision2012.pdf · Alternative AMC - Colour Vision 1 ... Med. 76, 421-429

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

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 http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=2407

1. 2) CAA Paper 2006/04 Part 2: Minimum Colour Vision requirements for Professional Flight Crew: Task Analysis http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=2408

2. 3) CAA Paper 2009/04: Minimum Colour Vision Requirements for Professional Flight Crew. Recommendations for new colour vision standard http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=3560 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

http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=2407�



CAD for EASA Sep 2012

Colour Assessment and Diagnosis (CAD) Test

Sally Evans

Chief Medical Officer UK CAA


Joint Project

• UK CAA

• City University

• FAA (Part 3)


Colour Assessment and Diagnosis (CAD) Test

Safety

Human rights

Applications


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


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


Colour Vision in Aviation • CAA Paper 2006/04 Part 1: ‘The Use of Colour Signals and

the Assessment of Colour Vision Requirements in Aviation’.

www.caa.co.uk/publications click ‘search for publication’ enter ‘colour vision’ in search box

http://www.caa.co.uk/publications


Current Colour Vision Primary Test

Ishihara Plates


Current Colour Vision Secondary Tests

Nagel Beyne

Holmes Wright Spectrolux


Problems with Current Tests • No test, including Ishihara1 and anomaloscope,2

assesses severity of colour vision loss • Pass/fail variability (within-subject and inter-subject) is

high1 • Lack of standardisation • Correlation between outcomes of different tests is

poor1 • 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, 421-429.

2 Barbur JL, Rodriguez-Carmona M et al (2008). A study of unusual Rayleigh matches in deutan deficiency. Visual Neuroscience 25, 507-516.


Terminology

• Normal trichromat – Normal colour vision

• Deutan

– Abnormal R/G discrimination – ‘M’-cone (green) abnormal

• Protan

– Abnormal R/G discrimination – ‘L’-cone (red) abnormal


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


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


Nagel Anomaloscope • Does not quantify well the degree of

loss of colour sensitivity • May not always detect colour deficiency


Task Analysis

• CAA Paper 2006/04 Part 2: ‘Task Analysis.

Airbus A321 and Boeing 757

www.caa.co.uk/publications click ‘search for publication’ enter ‘colour vision’ in search box



Internal Tasks


External Tasks


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


PAPI • Colour perception has to be accurate

and fast.

Too low Slightly low On slope Slightly high Too high


Perception of Colour: the CIE* diagram

*CIE (Commission Internationale de L’Eclairage) 1931 x,y chromaticity diagram

Yellow-Blue axis

Red-Green axis

= Normal threshold


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


Basis of the CAD Test • Uses data that describe statistical limits

of colour discrimination in normal trichromats

0.28 0.29 0.3 0.31 0.32 0.33

x

0.3

0.31

0.32

0.33

0.34

0.35

y

DeuteranopeProtanopeTritanope2.5% < P <97.5%"Standard Observer"


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.


Methods

Total of 182 participants: - 117 color deficient (77 deutan + 40 protan) - 65 normal trichromats - age ranging from 15-55 yrs

1 2 3 4 5 6 7 8 9

G/R W/G G/W G/G R/G W/R W/W R/W R/R

Red670 nm

Green546 nm

Yellow589 nm 2 degrees

1. PAPI 2. PAPI Signal Lights test 3. CAD test 4. Ishihara 5. Dvorine 6. Aviation Lights Test 7. Nagel Anomaloscope

1

2

3 4

5

6

7


Laboratory Simulation Schematic representation of optical set-up

Four stimulus channels derived from one light source

Random luminance variation

PAPI test

Viewing distance 4m

Visual angle ~1.4 min arc

Corresponds to approach

distance ~5.54km


Safety Critical Colour Discrimination

• CAA Paper 2009/04 Part 3: ‘Minimum Colour Vision requirements

for Professional Flight Crew’. www.caa.co.uk/publications click ‘search for publication’ enter ‘colour vision’ in search box

Gives evidence base for new colour vision

test and standards for flight crew.



Results

0.5 1 1.5 2CAD RG threshold units

0

20

40

60

80

100

PAPI

% c

orre

ct

Normals (n=65)

0 5 10 15 20 25RG threshold (CAD units)

0

20

40

60

80

100

Deutans (n=77)

0 5 10 15 20 25CAD RG threshold units

0

20

40

60

80

100

Protans (n=40)

0.5 1 1.5 2CAD RG threshold units

50

60

70

80

90

100

PAPI

% c

orre

ct


Results – effect of using a colour-corrected PAPI white

0 5 10 15 20 250

20

40

60

80

100

0 5 10 15 20 250

20

40

60

80

100

0.5 1 1.5 20

20

40

60

80

100

PAPI

(% c

orre

ct)

0 5 10 15 20 250

20

40

60

80

100

0 5 10 15 20 250

20

40

60

80

100

0.5 1 1.5 20

20

40

60

80

100

PAPI

% c

orre

ct

Normals Deutans Protans

RG thresholds (CAD units)

Standard WHITE

PAPI test

CC WHITE

PAPI test


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.


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


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.


CAD Assessment


Further Information

• www.city-occupational.co.uk/

• [email protected]

• City Occupational Ltd, Tait Building, C249, Northampton Square, London EC1V 0HB

mailto:[email protected]




Acknowledgements

• UK CAA

• City University, London

• Qinetiq

• FAA Federal Aviation Administration

Documents

United Kingdom Civil Aviation Authority Safety Regulation ...europeancmoforum.com/media/DIR_65301/UK-ColourVision2012.pdf · Alternative AMC - Colour Vision 1 ... Med. 76, 421-429