Navigation lights, buoys, flags, signals, chart symbols and many alarms and displays rely on colour. For this reason colour vision is assessed in seafarer medical examinations, and requirements are particularly important for deck duties.
Colour vision deficiency
Colour vision deficiency — often called colour blindness — usually means difficulty distinguishing certain colours, most commonly reds and greens. It is usually inherited, is more common in men than in women, and many people are unaware they have it until they are tested.
How it is tested
Screening often uses pseudo-isochromatic plates (such as the Ishihara test), where numbers are hidden in patterns of coloured dots. Some authorities accept or require additional tests, such as lantern tests or other approved methods, if a screening test is failed. The tests accepted vary by country.
Validity of colour-vision certification
Under the MLC, 2006 and STCW, a certification of colour vision is valid for a maximum of six years.
Why test early
If you are considering a deck career, find out about your colour vision before committing to training. Your national maritime authority’s rules decide which duties are affected and which tests are accepted.
Online colour-vision tests are not reliable: screens, brightness and settings vary. Only a test conducted under the conditions required by your authority counts.
Frequently asked questions
Can I check my colour vision online?
Online tests are for interest only. Screen colours vary, so only a properly conducted test with an approved method counts.
Does colour vision deficiency stop me working at sea?
It depends on the duties and your national rules. Some duties have strict colour-vision requirements and others do not. Ask your maritime authority or examiner.
Sources
- International Maritime Organization — STCW Convention and Code — Regulation I/9, Section A-I/9 (opens in a new tab)
- ILO / IMO — Guidelines on the medical examinations of seafarers (2011) (opens in a new tab)
Links go to the original publishers. SeafarerFit is not affiliated with or endorsed by these organizations.
SeafarerFit provides educational information, health calculators, screening tools and medical-examination preparation resources. It does not provide diagnosis, treatment, medical certification or official determination of fitness for sea service.