Occupational color vision norms in India: Time to amend?

Dear Editor,

Ishihara plates and lantern tests are used for screening and classifying the severity of color vision deficiency (CVD) in India for professions in fields such as Indian Air Force, Army, and Navy.[1] These tests categorize color vision loss such as color perception (CP) ranging from CP-1 (best color vision) to CP-4 (worst).[1] However, there is well-documented evidence that these methods are not suitable to classify the severity of CVD.[2] The lack of suitability of these tests in occupational provisions has been questioned previously; however, the consequences and alternative recommendations were not discussed.[3] The results of the lantern test are more variable as compared with other color vision tests and not validated thoroughly.[2] In addition, the other disadvantages of lantern tests are the lack of availability and services.[4] There is a poor correlation between the number of plates read in an Ishihara test and severity of CVD loss.[2] The current norms are likely to result in the unfair exclusion of high-quality candidates with mild-to-moderate CVD. The norms also risk passing a few individuals with high severity of CVD [see Table 1], which can pose a huge economic and social cost in sectors such as aviation, maritime, and railways. The overall aim of any color vision test should be able to allow the employer and employee to mutually agree upon tasks that can be safely carried out by an individual with CVD to ensure the public health and safety in the professional environment.

Table 1

Description of color vision categories for various professional fields in India and predicted fail rate in normals and pass rate in individuals with CVD[2]

Category	Professional Field	Description	% normals who fail	% CVD who pass
				Protans	Deutans
CP-1	Air Force, Navy	Pass Martin Lantern test at 6 m*	0.0	0.0	21.66
CP-2	Aviation	Zero errors on Ishihara test	18.15	0.71	0.63
CP-3	Army, Aviation	Pass Martin Lantern test at 1.5 m/read correctly plates 22-25 in Ishihara test	-	-	-
CP-4	Disqualified from the above jobs	Failed Martin Lantern test	-	-	-

*Prediction rates are given based on Holmes Wright Type A lantern test - CIE recommended protocol[2]

Recommendations

Use Color Assessment and Diagnosis (CAD) test, which is a valid test for assessing the severity of color vision loss[2] and recommended as standard in the UK for the professions including aviation and rail network employees[2]

Measure visual performance in a real-world working environment will provide a better metric to the suitability of an individual for a specific job.[5]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.