ED Decision 2019/002/R
(a) At revalidation and renewal examinations, colour vision should be tested on clinical indication.
(b) The Ishihara test (24 plate version) is considered passed if the first 15 plates, presented in a random order, are identified without error.
(c) Those failing the Ishihara test should be examined either by:
(1) anomaloscopy (Nagel or equivalent). This test is considered passed if the colour match is trichromatic and the matching range is 4 scale units or less, or if the anomalous quotient is acceptable; or by
(2) lantern testing with a Spectrolux, Beynes or Holmes-Wright lantern. This test is considered passed if the applicant passes without error a test with accepted lanterns.
(3) Colour Assessment and Diagnosis (CAD) test. This test is considered passed if the threshold is less than 6 standard normal (SN) units for deutan deficiency, or less than 12 SN units for protan deficiency. A threshold greater than 2 SN units for tritan deficiency indicates an acquired cause which should be investigated.
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