Seeing in Colour

8 November 2021
Testing for colour blindness

A recent scientific instrument acquisition reveals how tests for colour blindness were developed in the late 19th century.

Among The scientific instruments of the Macleay Collections is this dome-shaped, black-painted lantern – a recent acquisition from the University’s Discipline of Physiology. A clue as to its use and significance is provided by an engraved copper plate on the base, reading ‘Edridge Green Colour Perception Lantern’.

Frederick William Edridge-Green (1862–1953) was an English physician. He earned his Doctor of Medicine in 1889 and was awarded a gold medal for his thesis on colour vision and colour blindness. Colour vision deficiency had become a subject of increasing interest in the 19th century following a rise in transportation accidents.

Researchers theorised certain incidents could be explained by colour-blind workers misinterpreting coloured signal lights. When Swedish physiologist Frithiof Holmgren developed a test for colour blindness in the 1870s (requiring examinees to match coloured samples of wool), it quickly became a standard examination for employees and recruits in the railway and shipping industries.

Edridge-Green’s thesis and subsequent publications strongly criticised the use of the Holmgren Wool Test. In a series of experiments, he found a number of ‘dangerously’ colour-blind people were still able to pass the test. Further, he argued, to best determine a worker’s capacity to safely perform a job, colour-blindness tests should better represent what employees were expected to do in the field. As a result, he recommended an alternative test of his own design – the Edridge-Green Colour Perception Lantern.

Edridge-Green first described his lantern test in 1891. The updated version seen here was likely made after 1920. It is fitted with an electric lamp and features five rotatable discs, each with an operating handle. The discs are variously fitted with coloured filters, used to represent the signal lights encountered by railway and ship workers; clear, ground and ribbed glass filters, simulate weather conditions like rain, fog, and clear skies; and differently sized apertures imitate how signal lights would appear from a distance.

A scale on the reverse indicates which options have been selected. To successfully pass the test, candidates had to accurately name each coloured light produced alone, and in combination with the modifying glass filters and apertures.

Edridge-Green’s work attracted much attention, but his criticisms of the widely accepted Holmgren Wool Test surrounded him with controversy. His research and Colour Perception Lantern were both rejected, even after he was made a member of the International Code of Signals committee in 1892.

That same year, after being presented Edridge-Green’s work, The Royal Society voted to continue recommending the Holmgren test for assessing ship and railway workers. Despite these setbacks, Edridge-Green continued to campaign for the acceptance of his lantern test and over the years, professional opinion gradually shifted.

Researchers began validating Edridge-Green’s work and also noted faults with the Holmgren test. Finally, in 1915, the Board of Trade chose to cease use of the Holmgren test and instead adopted a lantern test based on Edridge-Green’s design. The Royal Navy and the railways soon followed suit and in 1936, he was awarded the Thomas Gray Memorial Prize for his invention.

Edridge-Green maintained an interest in colour vision throughout his lifetime and regularly visited the manufacturing facilities of his Colour Perception Lantern right up until his death in 1953. His obituary in The Lancet (25 April 1953, p.856) described him as “... the inventor of the first efficient test for colour-blindness”. Today, several transport industries still utilise lantern tests for colour blindness.

Written by Kelsey McMorrow, Curatorial Assistant, Macleay Collections, Chau Chak Wing Museum

Banner image: Edridge-Green Colour Perception Lantern (SC2021.16_07)

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