Abstract
Purpose: :
To investigate the genetic component of refractive errors and ocular biometrics using a classical twin design.
Methods: :
All twins currently living in Victoria aged 18 years or greater and of both genders were invited to participate through the Australian Twin Registry. Each subject underwent a general questionnaire, anthropometric assessment vision examination, cycloplegic refraction, ocular biometric assessment, slitlamp examination and individual blood samples were obtained via venepuncture. Myopia was defined as –0.5DS or worse in either eye.
Results: :
Out of 4158 twin pairs, 627 twin pairs consented to participate, giving this twin study an overall response rate of 15.1%. A total of 342 monozygotic and 267 dizygotic twin pairs with a mean age of 45 years (range 18– 88 years) were recruited and examined. The response rate for monozygotic twin pairs (20.4%) was almost double that of dizygotic twin pairs (11.7%). Myopia prevalence was approximately 25% in the study cohort. The case–wise concordance for refractive error was almost double in monozygotic twin pairs (0.78) compared to dizygotic twin pairs (0.47). The intra–pair correlation for refractive error, axial length, anterior chamber depth and keratometry was significantly higher in monozygotic twin pairs compared to dizygotic twin pairs (p<0.001).
Conclusions: :
Monozygotic twin pairs had a higher response rate than dizygotic twin pairs for all age groups. The myopia prevalence found in this twin study is comparable to that found in the general population. The significantly higher concordance for refractive error and higher intra–pair correlation for refractive error and ocular biometrics in monozygotic twin pairs compared to dizygotic twin pairs supports a genetic basis to myopia.
Keywords: myopia • genetics • refraction