Q: I have been selected as a plant operator in a gas industry. I am suffering from colour blindness. I have been working in a fertilizer-petrochemical industry for the last 17 years. I am able to segregate red, green & blue. How can I detect these colours, in spite of suffering from colour blindness? I am unable to say numbers in ishihara chart. But I can distinguish all the colours. I have not faced any problem for the last 17 years and have been able to distinguish colours on the computer or pipelines. In the ishihara test, I am able to do 3 charts out of 24. If I am unable to find out colour variation, then I should not be able to find even a single chart. How could this happen? How can I distinguish colours, if I am colour blind? Is there any other test for colour vision instead of Ishihara test? Is a person with colour blindness unfit for the plant operation job?

A:This condition is called Incomplete Red-Green blindness and is more common than people realise. This is an inherited condition and present in about 8% of men and 1% of women. You are born with it and you may have other blood relatives with this condition. You will have no difficulty in identifying colours separately but only when it is mixed with various hues. I myself detected this condition when experimenting with charts when I was a medical student but it has not stopped me from doing anything. Practical difficulties that you may face are trying to match tie with a shirt or carpet with a curtain, etc. You will not have any problem identifying traffic lights either. This is a static condition and does not get better or worse ever. Railway drivers, airline pilots and telecom engineers are not allowed with this condition, as they have to deal with critical subtle colours. You should not have any difficulty with your work. Only thing you must know, is you need good preferably daylight to distinguish fine differences in colour. There are several tests to detect colour blindness but Ishihara is still simplest and best. I think this should not affect your job but only your company can say its requirement. If they don't notice or enquire about this condition you don’t have to mention it yourself.