Adult-Onset Myopia - The Genes in Myopia (GEM) Twin Study
Mohamed Dirani 1*,
Sri N Shekar 2,
and
Paul N. Baird 3
1 Ophthalmology, Centre for Eye Research Australia, East Melbourne, Victoria, Australia
2 Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
3 Centre for Eye Research Australia, Melbourne, Victoria, Australia
* To whom correspondence should be addressed. E-mail: m.dirani{at}pgrad.unimelb.edu.au.
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Abstract |
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Objective: We wished to report the frequency of adult-onset myopia in a large cohort of Caucasian twins that were assessed as part of the Genes in Myopia (GEM) twin study. We also quantified the genetic contribution in adult-onset myopia using the classical twin model.
Methods: All twins aged 18 years or older were invited to participate in the GEM twin study through the Australian Twin Registry (ATR). Each twin underwent a standard questionnaire and a comprehensive eye assessment, including cyclopleged objective examination. Adult-onset myopia was defined as having the first spectacle/contact lens correction at the age of 18 years or older. Myopia was defined as spherical equivalent worse than or equal to -0.50 diopters (D).
Results: A total of 1224 twins (690 monozygotic twins and 534 dizygotic twins) aged between 18 to 86 years were recruited into the GEM study. A total of 96 twins
(96/347 = 27.7%) comprising 50 MZ and 46 DZ twins were first prescribed optical
correction for their myopia at the age of 18 years or older. A significantly higher MZ intra-pair correlation, r = 0.61, compared to that in DZ twins, r = 0.16, p<0.01)
for spherical equivalent was found in twins with adult onset myopia.
Conclusion: We identify adult onset myopia as a relatively common condition, with approximately one-quarter of myopia being acquired in adulthood years. To our knowledge, the GEM twin study is the first study of its kind to provide evidence to support a genetic component in adult-onset myopia.
Key Words:
refractive error, myopia, optics
