Twins provide clue to myopia development

UK research has found that the development of myopia is strongly linked to genetics and that its worldwide increase may not be closely associated to changes in lifestyle. The research, carried out at the Twin Research Unit at St Thomas' Hospital in London, indicated that a gene called PAX6 plays a 'crucial' role and concerns that the global increase could be due to children spending more time playing computer games or surfing the internet may be overstated. A genome-wide scan of 221 pairs of twins from the unit's database, published in August's American Journal of Human Genetics, found a significant link to four 'chromosome regions', including PAX6. Previous research by the same group suggested that genes were by far the most important factor with a heritability of 89 per cent Ð environmental factors only accounted for 11 per cent. Ophthalmologist Chris Hammond, honorary consultant at the unit and lead author of the new study, said the reasons for myopia were not well understood. 'Changes in lifestyle mean more time focusing on close objects Ð such as computer screens, mobile phones and books Ð are a factor, but our study now suggests these lifestyle factors may only have a major effect on genetically susceptible people. 'Our new research indicates that PAX6, which is already known to be fundamental to eye development and which is the sole gene causing a rare visually impairing condition called aniridia, is strongly linked to myopia. 'The genome-wide scan shows significant linkage to four chromosome regions Ð the largest one is right in the region of the PAX6 gene.' He called for further examination of PAX6 to find out where the mutations occur. 'Our research is great ammunition for mums and dads who are looking for ways to keep their children entertained during the long summer holidays,' said Hammond. 'It shows that children should balance any close reading with outdoor activities, especially if both parents are myopic.' He recommended moving the TVfurther away from the sofa and not allowing children to use computers 'for hours on end'. Professor Tim Spector, unit director said: 'Twins are a wonderful natural experiment that provide a scientific basis for assessing the relative importance of your family history or lifestyle factors in causing diseases and behaviours. 'This study shows the enormous power and potential of twin studies to help us first identify diseases that are primarily genetic Ð and then find the genes causing them.' If you are a twin (identical or non-identical) aged over 15 who would like to volunteer for the unit's work Ð or know patients who might be interested in volunteering Ð go to www.twinresearch.ac.uk to find out more.