Colour blindness

 

Colour blindness

Colour vision deficiency, more commonly called colour blindness, is a common, often genetic, condition. It usually means an inability to distinguish certain colours. The commonest type is red-green deficiency, making it difficult to differentiate between shades of red and green, and creating confusion with brown, orange, and purple.

The second, rarer, form is blue-yellow deficiency, which affects the ability to discern blue, green, and yellow.

The rarest form of colour vision deficiency is absolute colour blindness, when an individual sees only shades of grey.

There is no cure for any version of colour blindness, but corrective contact lenses or glasses can help make colour identification easier, though they are unhelpful for blue-yellow deficiency. People can adapt by learning position rather than colour, in traffic lights, for example, or by adjusting contrasts on iPhone or computer screens.

Many years ago, I had in my class of eight-year-olds, a very diligent, painstaking boy. His teachers in the nursery/pre-school class had initially been concerned that all his drawings and colouring were black. They feared that he had significant psychological problems. In fact, he was colour-blind and a much-loved, precious child. He said he wanted to be a pilot or an air traffic controller when he grew up. Obviously, that was not going to be a suitable career path for him.

He was a delightful boy, and I often wondered how his life developed. I really wanted to ask him what colours he could identify in monochrome drawings in books, but resisted the urge. It was not my place to investigate, and it might have distressed him to be questioned, but I have always pondered what version of colour blindness he had.

Ishihara colour plates are used to discern colour vision deficiency. These show numbers or shapes on a dot pattern background. There are more sophisticated versions to identify specifics.