Speaking to Business Post, the 52-year-old dad of two, whose granddaughter Isabelle turns two in May, said: "I actually went for an assessment to become a navigation officer in the Royal Navy and passed everything except the so-called 'Lantern Test
' to see whether you could identify a green light, a red light and a white light - that's when I found out that I was colour blind.
Other pseudoisochromatic screening tests and occupational lanterns were produced in different countries, and it became routine to use a pseudoisochromatic test to identify colour deficiency followed by a secondary occupational lantern test to determine colour-naming ability.
(7) Three new standards were proposed with the Ishihara test, the Farnsworth D15 (D15) test and an approved lantern test recommended for implementation (see Table 1).
(11) The recommended fail criterion for a lantern test is two errors on two runs (sequences) of nine colour pairs in photopic viewing but this can only be applied to the H-W lanterns and the FALANT.
Acceptance of these criteria particularly favours minimal/slight deuteranomalous trichromats that would have failed the lantern test and been rejected.
Frequently for potential candidates who are likely to face official lantern tests for some occupations seek an opportunity to experience a preliminary lantern test.
Therefore a lantern test is used for certain occupations to assist grading of visual ability and some details are described in the AOP Membership Handbook.
It was interesting to hear comments from a wife who sat beside her husband when he required a lantern test before his application for a flying licence.
Until recently, a failure on the Ishihara plates would have indicated the need for a Holmes Wright Lantern test to assess whether the applicant can recognise the colours used in aviation.
The majority of individuals with a colour vision defect make errors on a lantern test that simulates the red, green and white of maritime signals.
(72-75) The X-Chrom filter also does not affect the daltonian's performance on the Farnsworth Lantern test. (71,75) The lens does provide both chromatic and luminance cues on the D15 test and some patients do use the chromatic ones when performing the test.
Although lantern tests
are not used routinely in optometric practice, they are sometimes recommended for the assessment of colour vision for occupational purposes, especially for the railway, aviation and maritime industries.