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Visual abilities at 6 months in preterm infants: impact of thyroid hormone deficiency and neonatal medical morbidity

Nevena Simic1, Carol Westall, Elizabeth V Astzalos

  • 1Department of Psychology, University of Toronto, Toronto, Canada.

Thyroid : Official Journal of the American Thyroid Association
|February 11, 2010
PubMed

Insights

Preterm infants often have lower thyroid hormone (TH) levels, impacting their visual development. This study links reduced TH in early life to poorer contrast sensitivity and color vision in preterm infants.

Area of Science:

  • Neonatal Medicine
  • Endocrinology
  • Ophthalmology

Background:

  • Preterm infants face risks including neonatal morbidity, transiently reduced thyroid hormone (TH) levels, and impaired visual abilities.
  • Understanding the interrelationship between TH levels and visual development in preterm infants is crucial.

Purpose of the Study:

  • To investigate the association between thyroid hormone levels in the early postnatal period and visual abilities in preterm infants.
  • To compare the visual abilities of preterm infants with those of healthy term infants at 6 months corrected age.

Main Methods:

  • 62 preterm infants (stratified by gestational age) and 31 healthy term infants were studied.
  • Thyroid hormone levels (free thyroxine, triiodothyronine, thyroid-stimulating hormone) were measured at 2, 4 weeks, and 40 weeks postconceptional age.
  • Visual acuity, contrast sensitivity, and color vision were assessed using electrophysiological techniques.

Main Results:

  • Preterm infants showed reduced contrast sensitivity at low temporal frequencies and slower blue-yellow color processing compared to controls.
  • No significant differences were found in visual acuity between preterm and term infants.
  • Reduced contrast sensitivity and slower color vision processing in preterm infants were associated with lower TH levels, lower gestational age, and medical morbidities.

Conclusions:

  • Reduced thyroid hormone levels in the early postnatal period partially explain the weaker visual abilities observed in preterm infants.
  • These findings highlight the critical role of thyroid hormones in visual system development during early life.
Abstract

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