title: Visual Impairments Following Term Neonatal Encephalopathy: Do Retinal Impairments Also Play a Role?
abstract: OBJECTIVE
  We investigated the effects of term neonatal encephalopathy on retinal function and structure.
  
  
  METHODS
  A rat model of term neonatal hypoxic-ischemic (HI) encephalopathy (Vannucci model) was used. Hypoxia-ischemia was induced by a left common carotid ligation followed by a 2-hour period of hypoxia (8% oxygen) in Long-Evans rat pups at postnatal day 10 (P10). Sham operated rats served as controls.. Retinal function was assessed at P30 and P60 by electroretinograms (ERGs), after which retinal histology was performed. Retinocortical function was assessed with visual evoked potentials (VEPs) at P60 and subsequently brain histology was performed.
  
  
  RESULTS
  The ERGs of the HI animals at P30 and P60 demonstrated a significant reduction in the scotopic and photopic b-wave amplitudes, but a preserved a-wave amplitude. The retinal histology of the HI animals confirmed that the photoreceptor layer remained intact, whereas the inner layers of the retina were damaged. The HI animals also showed reduced VEP P100 amplitudes, which correlated with reduced left cerebral hemisphere surfaces. There was no correlation between the severities of retinal versus cerebral injuries.
  
  
  CONCLUSIONS
  Our findings suggest that term neonatal encephalopathy resulting from HI induces functional and structural damages to the inner retina, while relatively sparing the photoreceptors. These findings raise the possibility that retinal injuries may contribute to visual impairments with or without the presence of brain injury in term asphyxiated newborns and, thus, warrant further studies with humans and animals to better understand the disease process.
authors.affiliation: Division of Newborn Medicine Department of Pediatrics, Montréal Children's Hospital, McGill University, Montréal, Quebec, Canada 2Department of Ophthalmology and Neurology-Neurosurgery, Montréal Children's Hospital-Research Institute, McGill University, M.
authors.forename: Suna
authors.initials: S
authors.lastname: Jung
authors.affiliation: Department of Ophthalmology and Neurology-Neurosurgery, Montréal Children's Hospital-Research Institute, McGill University, Montréal, Quebec, Canada.
authors.forename: Anna
authors.initials: A
authors.lastname: Polosa
authors.affiliation: Department of Ophthalmology and Neurology-Neurosurgery, Montréal Children's Hospital-Research Institute, McGill University, Montréal, Quebec, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Lachapelle
authors.affiliation: Division of Newborn Medicine Department of Pediatrics, Montréal Children's Hospital, McGill University, Montréal, Quebec, Canada.
authors.forename: Pia
authors.initials: P
authors.lastname: Wintermark
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D004596:Electroretinography; D005074:Evoked Potentials, Visual; D005260:Female; D020925:Hypoxia-Ischemia, Brain / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D010786:Photoreceptor Cells; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000473:pathology / Q000503:physiopathology*; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D014793:Visual Cortex / Q000503:physiopathology