How the colour blind see coloured medication

Published in The Hindu on August 29, 2009

The colours of Warfarin tablets and containers, as seen by individuals with (A) normal and (B) deuteranopia (loss of medium-wavelength retinal receptors, which occurs in 1% of men). Asthma inhalers, as seen by individuals with (C) normal and (D) protanopia (loss of the ‘red’ or long wavelength retinal receptors, which occurs in 1 per cent of men). (B) and (D) were digitally altered with algorithms from Vischeck. The appearances shown in (B) and (D) are very similar to that for other kinds of red-green colour vision deficiency. Photo: The Lancet

One easy way to differentiate tablets is to look for their colours. That is also the reason why tablets come in different colours, and capsules have two colours. The red and black-coloured Becosules capules are a case in point.

The idea behind colour-coating medicines is to help people identify them quickly and correctly. Even the containers or strips are in specific colours. This is particularly useful to read the names of medicines on containers, especially the small print, which pose a challenge to those with poor vision. For those who are illiterate, colour-coding is the only resort to easy identification of drugs.

But colour-coding apparently fails in its purpose for those who are colour blind. “Eight per cent of men and 0.4 per cent of women have impaired colour-vision, of whom half are unable to recognise the main colours used in colour coding,” notes the journal The Lancet.

According to the journal, in a survey of 100 people with impaired colour-vision, 2 per cent had apparently confused their medication because they had mistaken the colour of tablets.

The photo published along with this article shows the appearance of warfarin tablets and containers to individuals who have normal vision and those with moderate or severe red–green deficiencies of colour vision. The pink tablet appears blue and the green tablet appears grey for those who are colour blind. [The brand names printed on the containers have been masked].

“People with red–green colour deficiency can recognise yellow, blue, grey, and white — perhaps manufacturers should incorporate this information into guidelines about the use of colour for tablet identification,” the journal notes.

Similarly, doctors and pharmacists have a role to play to avoid this problem. Patients should be instructed to identify tablets based on colour-coding only if they are certain that they (the patients) have a normal vision.