What is Ishihara Colour Blindness Test for Sailors?

A voyage on a ship requires seafarers to engage in a range of tasks involving symbols, markers, maps and signals for navigation. It is therefore important that they possess good eyesight.

A maritime career comes with innumerable surprises. It is a growing and ever-expanding industry which endows upon people a diverse array of opportunities. It is therefore a prerequisite for applicants to apply for several tests that will validate their qualifications.

One such prescribed test is the Ichihara colour blindness test which determines an individual’s eyesight function. It is a very reliable test that seafarers have to undertake during the recruitment process.

Accidents at sea because of defects in eyesight are a severe issue and can lead to disastrous consequences. A colourblind person cannot work as a maritime officer since they must be able to discriminate between colours of all kinds.

In a standard engine room, everything has a colour associated with it. Everything is appraised, controlled, and handled based on its colour, from the burner flame, pipeline markings, and lubrication colour to the wiring in panels. It is why colourblind people are unacceptable in the maritime field.

UMS Engine Control Room

About the Ishihara Colour Blindness Test

The Ishihara Colour Blindness test was developed by a Japanese doctor, Dr Shinobu Ishihara in 1917. He was a professor at the University of Tokyo. The test has since become a prerequisite in the marine world.

The test allows doctors to determine whether or not a person can identify and distinguish between various colours. Colour blindness is a broad term that covers a wide range of issues.

For example, some people are entirely colourblind, meaning they can’t recognise any colour, while others can only recognise a few colours. However, the two types of colour blindness: monochromacy and dichromacy, are the most popular.

Monochromacy is a sort of colour blindness in which people cannot distinguish between colours. In contrast, dichromacy is a type of colour blindness in which only two or three colours becomes indistinguishable.

Some military tasks require the ability to discriminate between hues, particularly those used for signal lights and flares, for operational or safety reasons.

Some Navy and Marine Corps combat operations occupations, as well as Army and Air Force Special Operations and Aviation jobs, require soldiers to be able to differentiate brilliant reds and greens.

colourblindness test

Process of the Ishihara Colour Blindness Test

The Ishihara test aims to see if people who want to be sailors can recognise and discern yellow, green, and red colours. Colour blindness is of two types: protanopia and Deuteranopia.

They are relatively uncommon, affecting fewer than 1% of the male population; yet, because seafarers must have perfect vision, the occurrence of this impairment will force aspiring seamen to give up their dream.

There are 38 plates in all, numbered from 1 to 38.

The numbers, however, stands as difficult to comprehend. They’re dispersed and random and sprayed on a dish covered entirely in coloured dots. A person is termed colour blind if they are unable to detect any colour difference in the coloured plates and numbers.

The dots on the circular plate may have colours- yellow and green. The numbers that lie along the coloured dots can be either red or brown.

Protanopia situation is detectable through the effective colour combination of an eye test. Alternatively, the dots on the circular plate may be colours- red and brown.

The numbers that lie along the coloured dots can be green and yellow colours. This type of Ishihara colour blindness test helps to find out the existence of Deuteranopia in a person.

Around 24 plates are examined to confirm that a person has a form of colour blindness and without bias. The number of plates tested can be used to determine the amount of Ishihara colour blindness.

Many maritime accidents and catastrophes become effectively avoidable with the help of an eye test.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

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8 Comments

  1. My eye vision -right eye 6/60 and left eye 6/6 .And i am btech mech. holder .Can i join merchant navy

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