Screening tool such as the Ishihara 24-plates are used to detect if there is red-green colour vision deficiency. Coloured numbers and lines are printed on each page. A score is given out of 24. For patients who don’t know numbers, there is a Colour Vision Testing Made Easy which uses symbols instead.

If the patient fails, tests like Farnsworth D-15 is a more detailed test, used to detect red-green and blue-yellow deficiencies (protan/deutan/tritan) and estimate the severity. This test requires the patient to arrange coloured caps in order of hue.

If further testing is required, patients can be referred to specialist centres that have FM-100 Hue test or anomaloscope. The FM-100 Hue Test measures fine hue discrimination and severity. This test is usually for those in the design, art and research fields. The anomaloscope or CAD test precisely measures red-green deficiencies and is used for official certifications such as for aviation licenses.