Be it the fiery red, melancholic blue or vibrant yellow, colours are indispensable to life. Instilling emotions, feelings and thoughts, human beings have always assosiated colours with joy, pleasure or grief. After all, visual aesthetics do play an important role in creation, perception and shaping your responses. Have you ever wondered how different would the world be for those who cannot differentiate between some of the colours? Colour blindness or colour vision deficiency, a condition that came into limelight after John Dalton’s paper on extraordinary facts relating to the vision of colours, can be defined as the decreased ability to perceive differences between some of the colours that others can distinguish. It is often of genetic nature, but may also occur because of some eye, nerve, or brain damage, or exposure to certain chemicals. Here’s what Dr Kaushik Murali, Consultant Paediatric Ophthalmology, director Nanna Kannu Comprehensive Eye Care Programme for Children, Sankara Eye Hospital has to say about colour blindness in children What is color blindness and what are the different types? Colour blindness is used in colloquial terms to refer to the difficulty in distinguishing colours apart but a more correct term would be colour vision defect. Colour blindness is a misnomer because only a small percentage of people are unable to see any colour. Five to eight per cent of men and 0.5 per cent of women in the world are born colour blind. The defect can be inherited or acquired. There are three groups of inherited colour vision defects: monochromacy, dichromacy and anomalous trichromacy. The last two groups are subdivided into red-green and blue-yellow types of defects. Monochromacy-Rod monochromats, or complete achromats, are truly colour blind since they cannot distinguish any hues. Dichromacy is a less severe form of colour defect than monochromacy. Dichromats can differentiate some hues apart. The ability of anomalous trichromats to distinguish between hues is better than dichromats but still not normal.What should teachers, school nurses, and parents know about being colour blind? How can they help children? Children may have difficulty especially with close hues. With colour being an integral part of the education system, it becomes important that teachers are aware of the possibility of some of the children having defective colour vision. To maximise contrast it is always better to use a white chalk as opposed to coloured chalks on a dark board. Also, teachers may look to label pictures where the response requires colour determination. Most parents are unaware of their child having a problem as a preventive screening is often not done. It would be ideal to screen the child at one, three and five years of age for visual problems. The colour vision can be tested in all five-year-olds and most three-year- olds. Can you tell us about the pediatric colour vision test for three to six-year- old children? In children we use a variant of the Ischihara test which is based on an pseudoisochromatic principle. For the non verbals there are patterns that the child can follow. For older folks we prefer the FM 100 hue test which is a more elaborate test and also provides a computer based analysis of the particular colour variants affected and the extent of the same.How does the world look to someone who is colour deficient? The world is not black and white as most would assume. They do not learn to call red ‘green’ and vice versa. Protanomalous or deuteranomalous individuals can usually pass as a normal observer in everyday activities. They may make occasional errors in colour names, or may encounter difficulties in discriminating small differences in colours, but usually they do not perform very differently from the normal except on colour vision tests. The colour spectrum shifts depending on the colour affected and they may find differentiation especially difficult in dim light.
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