Cognitive, behavioural, environmental and genetic associations of myopia in the Twins Early Development Study

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Myopia, or short-sightedness, occurs when the image of a viewed object is not focused accurately onto the retina (refractive error), specifically in myopia the image is focussed in front of the retina. This results in the observer seeing a blurred image and requires correction in the form of glasses or contact lenses. Myopia is the most common eye condition worldwide. Failure of adequate correction of myopia leaves a child with a visual disability that can affect development, education and future prospects. The World Health Organization (WHO) has identified 153 million people who are visually impaired due to uncorrected refractive errors. The identification and treatment of myopia is now a WHO priority within their initiative to eliminate avoidable blindness.People with myopia, especially those developing myopia in childhood, as they are likely to become highly myopic by adulthood, are additionally at risk of sight threatening problems such as retinal "wear and tear" degeneration or retinal detachment. The number of people with myopia is increasing; in some countries up to 80% of children leaving school are myopic, and we believe this means that there is going to be an increasing problem of blindness in middle aged and older people due to this common problem. It is not known what is driving this increase although it is known that both a person's genes and environment are influential; previous studies have identified potential risk factors such as prolonged close work, urbanisation and lack of outdoor light. The aim of this study is to examine the complex influence of genes and environment on a person's risk of developing myopia in a large cohort of British twins. The unique Twins Early Development Study (TEDS) consists of over 10,000 twins who have been studied since birth to their current age of around18 years old. TEDS researchers have assessed the relative influence of nature (genes) and nurture (environment) on aspects of cognition, language, behaviour and education. Previous research has yielded interesting findings on shared genetic influences for diverse learning disabilities and abilities. We plan to correlate this data with the level of myopia at the age of 18. Sophisticated statistical techniques will be used to investigate the relative effects and interactions between a person's genes and their environment on the risk of developing myopia. We also plan to use advanced genetic techniques to identify potential genetic variations (changes in the DNA) that could cause myopia in this age group using DNA that 4,000 of the twins have previously provided.This research will be carried within Kings College London by collaborators from both TEDS and the Department of Genetic Epidemiology and Twin Research (TwinsUK). The research will be undertaken by researchers in ophthalmology (doctors specialising in eye diseases), in partnership with geneticists and statisticians.We hope this research will provide novel information on why myopia develops and why the incidence is increasing. A estimate of the level of myopia in this age group within the UK will be obtained and an increased undertstanding of the environmental and genetic influences causing the disease, which can only be obtained from twin studies. This may enable targeted lifestyle modifications or development of treatments that could reduce myopia development or progression in the future.