Discordant Unilateral Myopia in Adult Female Monozygotic Twins Discordant Refraction in Monozygotic Twins
Mohamed Dirani BOrth&OphthSc(Hons) 1,2
Matthew Chamberlain MBBS 1
Pam Garoufalis BSc BOrth(Hons) 1,2
Christine Chen MBBS 1,2
Robyn H. Guymer MBBS PhD FRANZCO 1
Paul N. Baird BSc(Hons) PhD 1,2
1 Centre for Eye Research Australia, University of Melbourne, Australia
2 Vision Cooperative Research Centre, Sydney, Australia
Purpose: We present the first single case study of extremely discordant monozygotic twins for refraction, which provides an insight into the complexity of myopia.
Method: The twins were recruited through the Australian Twin Registry (ATR). Each individual completed a general questionnaire, vision examination and a blood test. Visual acuity was examined using the LogMAR chart at 3m. Cycloplegic (tropicamide 1%) refraction using the Topcon (KR 8100 model) auto-refractor and ocular dimensions (axial length, keratometry, anterior chamber depth) were obtained using the IOL master (Carl Zeiss P/L).
Results: A pair of female monozygotic twins aged 62 years with highly discordant refraction is reported. One twin member has myopic anisometropia with a difference of 7D while her identical twin has no evidence of anisometropia and is mildly hypermetropic in both eyes.
Conclusion: The twins medical and birth history fail to explain the discordance in refraction between the twin pair. There is no marked difference in environmental exposures and medical history between the twins to explain the discordance in refraction. It is possible that the discordant refraction is a result of inter-uterine trauma to twin one during embryonic development or possible injury of being born second to her twin.
