Before we look at the correction options for colour blindness, let us first understand what colour blindness is all about.
Colour blindness means one does not see colours in a usual way and cannot distinguish between specific colours. The eye functions like a camera and helps capture images and focus them on the innermost layer of the eyeball called the retina.
This layer consists of special nerve cells and pigments that help communicate with the brain. There are two types of pigments in the retina, namely ‘Rods’ and ‘Cones’. The rods have only one type of pigment and sensitive to light. Rods are responsible for night vision, while the cones have several kinds of pigments present in three types of cone cells. The cones are responsible for colour vision, and each cone cell reacts to a particular wavelength of light. The three-cone cells are responsible for perceiving red, blue, and green light wavelengths.
These three cone cells work together and enable us to see the entire spectrum of colours. When the cones have all the various photo-pigments, the eye sees all colour. An absence or deficiency of one or more of the photo-pigments results in colour vision blindness or simply colour blindness.
Colour blindness can be mild, moderate or severe. In severe colour blindness, there are no pigments present in the cone cells. The person sees colour in shades of grey, and this rare condition is called achromatopsia.
In certain mild forms of colour vision, one can detect or see colours in bright light but cannot distinguish colours in dim light. The severity of colour blindness is detected by an optometrist or an ophthalmologist with the help of various colour vision tests. Approximately 40% of the colour blind are unaware of their condition, while the remaining may experience problems with their everyday life.
Worldwide approximately 350 million people suffer from colour blindness affecting 1 in 12 men (8%) and 1 in 200 women (0.4%). Colour blindness is vastly a hereditary (genetic) condition with females being carriers, affecting males more than females. In a small percentage of the population, colour blindness is acquired secondary to certain long-standing diseases like diabetes, multiple sclerosis, or certain medications or even due to injury.
Inherited colour blindness remains stable throughout life in contrast to colour blindness which is acquired.
Red-Green colour blindness is the most common type of colour blindness, which is hereditary and exists with different degrees of severity. In Red-Green colour blindness, there could either be a deficiency or absence of red or green photo-pigments. Hence, viewing colours containing these pigments would be a challenge. Blue-Yellow colour blindness is usually acquired in nature and occurs due to deficiency or absence of blue photopigment.
Colour confusion is the most common symptom experienced by the colour blind. They tend to misidentify a colour presented compared to a person with normal colour vision. Interpreting colour coded information in graphs, maps and charts could be frustrating for a colour blind. It is essential to identify colour blindness so that an appropriate coping strategy can be suggested or counselling for career choice can be given. Colour blindness could be a disability in few careers like armed forces, aviation industry, drivers, designers and other jobs which require colour discrimination. The colour blind experience normal vision in all other aspects and only need certain adaptation and coping strategies to perform everyday activities.
There is no cure for colour blindness; however, there are specific contact lenses and glasses that have special filters to help a colour blind person perceive colours based on the type and severity of their colour blindness.
These help colour perception and help detect shades of colour previously unseen and help to see colours brighter and sharper. However, these corrective aids cannot be used to pass a medical (eye) examination for job requirements where colour vision is a mandatory requirement.
Also, caution should be exercised using these since, on certain occasions, it has even lead to colour confusions. Hereditary colour blindness, which is stable, can be helped with these aids. Acquired colour blindness usually returns to normalcy once the cause has been identified and treated. Recommendations for the type of contact lenses or glasses can be made by an optometrist/ophthalmologist only after a thorough eye examination to determine if the condition is genetic or acquired and after understanding its severity.