Relationship Of Nutrltion In Pregnancy And Astigmatism Formation In Twins

Background/Aim Astigmatism is a refractive error in which the unequal curvature of one or more ocular refractive surfaces prevents light rays from focusing at one point on the retina. Astigmatism is a very common refractive error in human, but its etiology is poorly understood. The role of genetic factors in the formation of astigmatism had been proven. Genetic effects on astigmatism accounted for 47% to 49% of total astigmatism. It is believed that environmental factors may play an important role in the development of this condition. The primary purpose of this study was to examine the association between nutritional status of pregnant mothers and the risk of astigmatism in twins.Methods This was a prospective cohort study. A total of 28 twin pairs (11 monozygotic [MZ] and 17 dizygotic [DZ]) aged between 3 months and 6months from Jiangsu Province Hospital were enrolled. Noncycloplegic refraction was measured by vision screening instrument 3,6,9,12 and 18 months after birth(delivery). The relationship between astigmatism and related factors of pregnant mothers and infants was analyzed. Meanwhile 56 cases of singleton were randomly selected as control group. Twins wih the value of astigmatism C1.0D≤C≤2.0D as group 1, twins wih the value of astigmatism C≥2.0D as group 2.Results Detection rate of astigmatism was 53.57%,43.75% respectively(cylinder power of 2.0 D or worse) in observed twins' group 3 months,12 months after birth(delivery),which was significantly higher than that of their parents(14.28%,cylinder power of 1.0 D or worse),and that of singletons. The value of astigmatism were correlated with family history. Morning sickness(OR=1.40,95%CI 1.10～5.13),BMD(OR=1.44,95%CI 1.30～6.19)and haemoglobin(OR=1.40,95%CI 1.03～2.78) of mother during midpregnancy,maternal serum magnesium (OR=1.39,95%CI 1.03～1.89) and vitamine A(odds ratio=1.03,95%CI 1.01～1.05) during delivery, umbilical vein vitamine D(OR=1.02,95%CI 1.00～1.04), birth weight(OR=1.02,95%CI 1.00～1.03)were correlated(P<0.05)with the formation of twins astigmatism. The vaive of astigmatism present at 3 months after birth decreased with months of age (regression analysis, r2=0.19, p<0.05),the value of twins astigmatism were much higher than that of singletons.The consistence of astigmatism with their parents in twins and singletons were 58.33%,57.14% respectively.The percentage of astigmatism with C≥1.0D in group 1 dropped to 13.23%,while it decreased very little in group 2.Conclusion Detection rate of twins astigmatism was significantly higher than that of singletons. The formation of astigmatism in twins was related with the level of maternal and fetal nutrition and other factors, noticeably morthers'morning sickness, haemoglobin and twins'birth weight. Further studies are needed. Corresponding nutrition instruction should be given to pregnant women to lower the risk of astigmatism.