Discordant Duane's Retraction Syndrome in Monozygotic Twins

To evaluate whether differences in the intrauterine environment caused discordant Duane's retraction syndrome in monozygotic twins. Pathology records were reviewed to determine monozygosity. Discordant Duane's retraction syndrome was present in twin boys with identical genetic foundations who had different intrauterine environments. The placenta indicated areas of anastomosis between the two umbilical cords suggestive of twin-to-twin transfusion that resulted in a visible growth discordance. Intrauterine environment influences ocular development, and twin-to-twin transfusion may cause Duane's retraction syndrome.