Daltonism

Colour blindness is a condition that affects our ability to distinguish and perceive colours.

Colour is a fundamental element integral to everyday life.

Many aspects of modern life increasingly require a correct interpretation of colours. Given the importance of colour as a communication element, it is understandable that colour vision defects lead to socio-cultural complications. These changes have an impact at various levels and can compromise the teaching/learning process and even the performance of certain professions.

The interest and curiosity about the phenomenon of colour vision, that is, the vision of colours, dates back to antiquity, with speculations made by several philosophers and scientists. But it was from the 18th century onwards that the first studies on colour vision began, with greater scientific rigour and impact. Among the various personalities who looked into this subject is John Dalton, who himself suffered from alterations in colour vision, which in 1798 gave rise to the term colour blindness.

As scientific knowledge evolved, it was discovered that the ability to distinguish colours depends on the light that is reflected by all the bodies and objects that surround us. That is, of the total set of light received by an object, part of it is absorbed, while the rest is reflected. The eye is able to identify the various wavelengths reflected, from which we highlight red (580nm), green (540nm) and blue (450nm). The combination of those 3 colours allows the vision of the whole colour spectrum.

The cells responsible for receiving the various light stimuli are the photoreceptor cells, located in the retina, especially in the macula, which has a higher concentration of cones, the receptor cells. The cones are the cells which enable us to see clearly during the day and to see colours. There is another type of photoreceptor, the rods, which are much more numerous in the peripheral retina, but they are specialised in night vision and only see on a greyscale (they see in black and white).

Some studies address the various difficulties that individuals with colour blindness face throughout their lives.

Colour is used as a teaching tool and is embedded in different areas of knowledge. At the beginning of their school career, some children perform less well because of the incorrect way they describe common objects and/or how they paint them.

As well as in education, colour interpretation plays an important role in many professional areas. There are professional careers that cannot be pursued by people with colour blindness, for example, military service.

In general, patients report difficulties with learning materials, teaching practices, interactions with peers and teachers, already from the onset of secondary socialisation.

In adulthood they mainly report difficulties related to decoding road signs. Patients develop some skills to overcome difficulties, related to their social, educational and work needs.

Despite its importance, the subject of colour vision disorders is often neglected and not given its due importance.

Colour blindness leads to the absence of perception of some colours or perception of a different colour from the real one. The scientific term for colour vision disorders is dyschromatopsia, which is the absence or deficiency in the perception of one or more colour spectrums.

Colour changes can be divided into two main groups - congenital and acquired defects.

Congenital defects, present from birth, constitute the majority of cases in the general population and reach 8%, of which 1% are women and 7% men.

Within acquired defects, the lesions found tend to affect blue colour perception more frequently, where the cause may be related to systemic pathologies, such as arterial hypertension and diabetes mellitus, for example, or due to ocular pathologies, such as pigmentary retinopathy.

Distinguishing the two types of alteration will ensure that the patient has the best possible referral.

Diagnosis of the type of colour blindness can be done with the help of colour vision tests such as the Ishiara and Farnsworth Tests.

A normal trichromatist identifies the entire spectrum visible to humans. An anomalous trichromat has alterations in the identification of one of the three primary colours. If the alteration occurs for the red colour it is called protanomaly, for the green light deutanomaly and for the blue light tritanomaly. Red-green axis defects are the most frequent, and it is estimated that 5% of men are deutanomalous as well. Effects involving the blue cones are rare.

Although there is no cure for colour-blindness, there are various strategies for the colour-blind population to reduce the difficulties experienced on a daily basis, such as, for example, the application of codes associated with each colour or through specialised glasses.

Even so, each colour-blind individual can create and develop their own strategies, always with the aim of making their daily life easier and more agile, without their visual impairment affecting their wellbeing and socio-cultural life.