title: Altered anterior visual system development following early monocular enucleation.
abstract: OBJECTIVE
  Retinoblastoma is a rare eye cancer that generally occurs before 5 years of age and often results in enucleation (surgical removal) of the cancerous eye. In the present study, we sought to determine the consequences of early monocular enucleation on the morphological development of the anterior visual pathway including the optic chiasm and lateral geniculate nucleus.
  
  
  METHODS
  A group of adults who had one eye enucleated early in life due to retinoblastoma was compared to binocularly intact controls. Although structural changes have previously been reported in late enucleation, we also collected data from one late enucleated participant to compare to our early enucleated participants. Measurements of the optic nerves, optic chiasm, optic tracts and lateral geniculate nuclei were evaluated from T1 weighted and proton density weighted images collected from each participant.
  
  
  RESULTS
  The early monocular enucleation group exhibited overall degeneration of the anterior visual system compared to controls. Surprisingly, however, optic tract diameter and geniculate volume decreases were less severe contralateral to the remaining eye. Consistent with previous research, the late enucleated participant showed no asymmetry and significantly larger volume decreases in both geniculate nuclei compared to controls.
  
  
  CONCLUSIONS
  The novel finding of an asymmetry in morphology of the anterior visual system following long-term survival from early monocular enucleation indicates altered postnatal visual development. Possible mechanisms behind this altered development include recruitment of deafferented cells by crossing nasal fibres and/or geniculate cell retention via feedback from primary visual cortex. These data highlight the importance of balanced binocular input during postnatal maturation for typical anterior visual system morphology.
authors: Department of Psychology, York University, Toronto, Canada ; Centre for Vision Research, York University, Toronto, Canada ; Department of Ophthalmology and Visual Sciences, The Hospital for Sick Children, Toronto, Canada.
authors: Krista R
authors: KR
authors: Kelly
authors: Larissa
authors: L
authors: McKetton
authors: Keith A
authors: KA
authors: Schneider
authors: Brenda L
authors: BL
authors: Gallie
authors: Jennifer K E
authors: JK
authors: Steeves
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015353:Eye Enucleation; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009897:Optic Chiasm / Q000473:pathology; D009900:Optic Nerve / Q000473:pathology; D012175:Retinoblastoma / Q000601:surgery; D013223:Statistics as Topic; D013477:Superior Colliculi / Q000473:pathology; D015349:Vision, Monocular; D014793:Visual Cortex / Q000473:pathology; D014795:Visual Pathways / Q000473:pathology*; D055815:Young Adult
keywords: Anterior visual system development; Lateral geniculate nucleus; Monocular enucleation; Optic chiasm; Retinoblastoma