PREVALENCE OF COLOUR VISION DEFICIENCY AMONG MEDICAL STUDENTS AND HEALTH PERSONNEL
The mean age of the respondents was 26 years (range 18-57 years). In the sample studied, 45 persons (3.2%) were found to have red-green colour vision deficiency. The sex-specific prevalence of colour vision deficiency, by ethnicity and category of personnel, is given in Table 1. The prevalence of colour vision deficiency was more in males than females (6.7% vs 0.4%, p<0.001). The ethnic difference in colour vision deficiency was not statistically significant in both genders. The prevalence rates of colour vision deficiency by category vary from 0.3% (for nurses, all females) to 8.2% (for medical assistants, all males).
The term “colour blindness” commonly used in daily practice is a misnomer. To our best knowledge, we have not come across any person who is totally colour blind, i.e. he/she should appreciate everything in life as black and white only. Instead, all the persons diagnosed as “total colour blindness” by Ishihara Chart could identify the primary colours correctly when shown each colour individually. In addition to Ishihara colour vision test plates, other methods such Naegel anamaloscope test and Franseworth-Munsell hundred hue test are also available to test for colour vision. These two tests are more sensitive and accurate, but time consuming; thus, not suitable for mass screening.4 The Ishihara test charts were chosen in this study because it is easier and quicker to perform; familiarisation with all the colours is not necessary since the answer given is in terms of numbers and not in terms of colours; the test is accurate for assessment of colour vision deficiency in mass screening.
The prevalence of colour vision deficiency in our sample of medical students and healthcare personnel was similar to reported rates in Western general population and healthcare workers.1 Our study did not find statistical significant difference in the prevalence of colour vision deficiency by ethnicity.
It is well known that people who are deficient in colour vision adapt to their deficiency by using cues. In a population-based cohort study, Cumberland found congenital colour defects confer no functional disadvantages in relation to educational attainment or unintentional injury, thus challenging the rationale for screening.5 It is generally accepted that colour vision deficient adults can drive safely because they can tell a stop sign by its shape and know which traffic light means “go” and which one means “stops” because they are always in the same order on traffic lights. However, technological changes (e.g. lower cost of colour printing, wide use of colour computer monitors) present additional problems for those with this deficiency.6 Is the problem faced by these people merely a minor inconvenience?
For the healthcare practitioners, detection of certain clinical signs require unimpaired colour vision, such as cyanosis, jaundice, retinal changes, colour of body fluids (e.g. haematuria), and blood in vomitus. When compared with normal controls in the performance of clinical tasks requiring colour differentiation, those who are colour vision deficient tend to perform poorer.7-12 The extent to which these difficulties translate into actual clinical errors in unknown. In our society where we are placing increasing emphasis on equal opportunity, people with colour vision deficiency need not face unnecessary discrimination.6,13 However, early detection of colour vision deficiency is helpful for those embarking on a healthcare profession. For the colour vision deficient doctors, disciplines such as anaesthesiology, emergency medicine, pathology, microbiology and dermatology may pose difficulties but psychiatry and neurology are less problematic.
This study was funded by International Medical University (project code 024/2002).
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- Reddy SC, Hassan M. Refractive errors and other eye diseases in primary school children in Petaling Jaya, Malaysia. Asian Journal of Ophthalmology 2006 (in press)
- Ishihara S. The series of plates designed as a test for colour deficiency, 24 plates edition. Tokyo, Japan, Kanchara & Co Ltd. 1998; p 1-9
- Newell FW. Ophthalmology- Principles and concepts. 8th edn,St Louis, Mosby-Year Book, Inc. 1996; p 157.
- Cumberland P, Rahi JS, Peckham.C.S. Impact of congenital colour vision deficiency on education and unintentional injuries: findings from the 1958 British birth cohort. BMJ. 2004;329:1074-5 [PubMed]
- Cole BL. The handicap of abnormal colour vision. Clin Exp Optom. 2004;87:258-75 [PubMed]
- Campbell JL, Spalding AJ, Mir FA, Birch J. Doctors and the assessment of clinical photographs--does colour blindness matter? Br J Gen Pract. 1999;49:459-61 [PubMed]
- Campbell JL, Spalding JA, Mir FA, Birch J. Doctors and the assessment of blood glucose testing sticks: does colour blindness matter? Br J Gen Pract. 2000;50:393-5 [PubMed]
- Campbell JL, Griffin L, Spalding JA, Mir FA. The effect of abnormal colour vision on the ability to identify and outline coloured clinical signs and to count stained bacilli in sputum. Clin Exp Optom. 2005;88:376-81 [PubMed]
- Koningsberger JC, van Norren D, van Niel JC, Dekker W. Does color vision deficiency in the endoscopist influence the accuracy of endoscopic diagnosis? An anonymous study with Dutch gastrointestinal endoscopists. Endoscopy. 1994;26:549-53 [PubMed]
- Spalding JA. The doctor with an inherited defect of colour vision: effect on clinical skills. Br J Gen Pract. 1993;43:32-3. [PubMed]
- Spalding JA. Medical students and congenital colour vision deficiency: unnoticed problems and the case for screening. Occup Med (Lond). 1999;49:247-52 [PubMed]
- Spalding JA. Confessions of a colour blind physician. Clin Exp Optom. 2004;87:344-9 [PubMed]
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