This protocol refers to congenital and acquired colour vision deficiency (CVD).
Colour vision is the ability of the eye to distinguish objects based on the wavelengths (or frequencies) of light. A person's perception of colours is a subjective process where the reaction of the incoming light with specialised cells in the retina (cone cells) is interpreted by the brain. Differences in the function of cone cells and interpretation by the brain of the cone cell messages result in different people seeing the same object or light source in different ways.
Aviation-related occupations rely on colour displays, colour-coded charts and coloured signal lights to convey operational and safety information. It is important that aircrew and controllers can quickly and accurately receive and interpret safety information that is conveyed using colour.
Congenital CVD affects approximately 8% of the male population and less than 1% of the female population. The most common congenital CVD is related to the perception of red and green colours. Very rarely (less than 1% of male and female population) the perception of yellow and blue are affected.
Acquired CVD affects men and women equally and is more commonly affecting the perception of yellow and blue.
Whether CVD is congenital or acquired, it can also be made more severe due the use of certain medications and the presence of certain medical conditions.
Aeromedical Implications
Effect of aviation on condition
- Hypoxia – reduced sensitivity of retinal cone cells to light stimulus in hypoxic conditions. This means that people will experience reduced colour sensitivity with increasing altitude in the absence of supplementary oxygen. This will be amplified in the presence of congenital or acquired CVD.
Effect of condition on aviation
- Subtle incapacitation - impaired reaction / decision-making due to reduced ability to interpret information conveyed using colour cues.
- Incapacitation – inability or impaired ability to perceive time-critical and safety-critical information conveyed using colour cues during critical phases of flight.
Approach to medical certification
Based on condition
- For pilots: as per CASR 67.150 6c, 67.155 6c, an unrestricted medical certificate for congenital CVD will be issued if any of:
- Pass the initial assessment (tier 1) using Ishihara PIP
- If fail PIP, pass the secondary assessment (tier 2) using FALANT
- If fail FALANT, pass the tier 3 assessment of AOCVA or CAD
- At each stage of assessment, the Pilot has the choice to not advance to the subsequent level of assessment. Instead, they can opt to accept the restrictions and be granted a restricted medical certificate, allowing them to resume assessments until a later time.
- If a pilot with congenital CVD who has passed any of these assessments develops a medical condition or uses a therapy that may further impair CVD, they will require review by a designated aviation ophthalmologist who may recommend reassessment using a tier 3 test.
- If a pilot has acquired CVD, they will require review by a designated aviation ophthalmologist who may recommend single assessment or ongoing surveillance using a tier 3 test.
- If tier 3 assessment is not passed, certification will be individually assessed in consultation with a DAO and any other medical and operational SMEs as needed.
- For ATCs: as per CASR 67.160 6a
- Pass the initial assessment using Ishihara PIP.
Based on Treatment
- If an acquired CVD, management of the condition causing the CVD leads to normalisation of the colour sensitivity as demonstrated by passing a tier 3 test, AND the condition itself is stable (not deteriorating).
Demonstrated Stability
- Absence of any medical condition or medication/therapy that may cause acquired CVD or cause a worsening of congenital CVD
Risk assessment protocol - Information required
New cases
- If Tier 1 and 2 tests not passed, review by a DAO for assessment of eye health and suitability for tier 3 assessment. DAO review includes all items required for CASA eye assessment for medical certification.
- If Tier 2 and 3 not passed, review by consultant ophthalmologist to conduct and report a CAD test, OR result of AOCVA.
- For ATC, if tier 1 test is not passed, the applicant is ineligible for medical certification.
Renewal
For pilots with congenital CVD:
- AOCVA or CAD pass is enduring and does not need to be repeated unless the pilot develops a medical condition or uses a therapy that may further impair CVD.
For pilots with acquired CVD:
- Repeat assessment with AOCVA or CAD may be required on the recommendation of a DAO, based on the individual clinical features.
For ATCs with acquired CVD:
- Assessment with CAD may be required on the recommendation of a DAO, based on the individual clinical features.
Indicative outcomes
CASA Aviation Medicine colour vision assessment process, specifically for a Class 1 and 2 initial medical application.
Colour vision testing order:
- Test 1. Pseudoisochromatic Plate Test (PIP)
- Test 2. Farnsworth Lantern Test (FALANT)
- Test 3. Colour Assessment and Diagnosis (CAD)
- Test 4. Australian Operational Colour Vision Assessment (AOCVA)
Applicants who fail initial tests 1 and 2 can continue to test 3 or opt to skip to further operational assessment and complete test 4. If an applicant elects to skip test 3 and fails test 4, they are not permitted to take test 3.
Results and next steps for a pass on any test - the applicant receives a certificate with no colour vision deficiency restrictions.
Results and next steps for a fail on any test - the applicant may choose to either accept the restrictions for their class type or proceed with the next level of testing. After test 4 is reached, there are no further tests and applicant will need to accept the restrictions.
Restrictions for Class 1 certification include Not valid for night operations, not valid for passenger operations unless accompanied by another flight crew member who is not colour vision deficient, does not comply with ICAO 6.2.4.4.
Restrictions for Class 2 certification include not valid for night operations.
- Pilots who do not pass AOCVA or CAD may be issued restricted or conditional medical certificates that provide risk management for the safety implications of their colour vision deficiency. Restrictions may include:
- Class 2: not valid for night operations
- Class 1: not valid for night operations; for flight in daytime, valid for passenger operations with operational multicrew limitation with a non-colour-deficient flight crew member; does not comply with ICAO An1 Ch6 Std 6.2.4.4.
Favourable
- Absence of medical condition or medications/therapy that can cause acquired CVD or can worsen congenital CVD
Unfavourable
- Presence of medical condition or medications/therapy that can cause acquired CVD or can worsen congenital CVD
Pilot and Controller Information
- Colour is used in many aviation safety systems to convey important operational and safety information.
- Pilots and ATCs need to be able to perceive and interpret information that is conveyed using coloured cues to be able to exercise the privileges of their licences.
- Pilots who do not pass initial colour vision screening tests may be able to perceive and interpret colour-based information safely despite being unable to identify individual colours. Their ability to do so must be demonstrated using either the AOCVA or the CAD.
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Disclaimer
The clinical practice guidelines is provided by way of guidance only and subject to the clinical practice guidelines disclaimer.