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Nevena Simic, Joanne Rovet; Visual development in preterm infants: Assessing the impact of transient thyroid hormone deficiencies. Journal of Vision 2009;9(8):1058. doi: 10.1167/9.8.1058.
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Preterm birth is associated with an increased risk of visual impairment. However, not all visual deficits can be fully explained by the typical prematurity morbidity factors. In addition, children born preterm often exhibit transient hypothroxinemia of prematurity (THOP) due to premature severing of the maternal supply of thyroid hormones. Because thyroid hormone (TH) is critically needed for multiple facets of early brain development, including the structures needed for visual processing, and because the maternal thyroid supply is essential throughout pregnancy, it is possible that THOP contributes to the visual impairments seen in preterm children. To test this hypothesis, we used both clinical tests and visual evoked potential (VEP) techniques to assess visual abilities in two cohorts of preterm infants whose TH levels were measured in the perinatal period. In the first cohort born 30 to 35 weeks gestation, we found associations between low TH levels and reduced visual attention at 3 months corrected age (Study 1) and poor visuomotor abilities at 12 and 18 months corrected age (Study 2). In the second cohort born 23 to 35 weeks gestation, THOP severity was negatively correlated with visual attention at 3 months corrected age (Study 3) and contrast sensitivity and color vision at 6 months corrected age (Study 4). These findings therefore suggest that TH is necessary for the development of early visual abilities and that THOP may partially explain the visual deficits of preterm infants.
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