title: Visualization of Nerve Fiber Orientations in the Human Optic Chiasm Using Photomicrographic Image Analysis.
abstract: OBJECTIVE
  Hemidecussation of fibers entering the optic chiasm from the optic nerves is well recognized. The reason why bitemporal hemianopia results from chiasmal compression has not been fully explained. There is still a paucity of data relating to the precise details of the routes that the nerve fibers take through the chiasm and, in particular, where and how nerve fibers cross each other. This information is important to understanding why crossing fibers are selectively damaged as a result of chiasmal compression.
  
  
  METHODS
  An optic chiasm obtained at postmortem was fixed, stained, and sectioned to allow high-resolution photomicrographs to be taken. The photomicrographs were integrated to allow regions of interest across entire sections to be analyzed for fiber direction and crossing.
  
  
  RESULTS
  The results confirmed that fibers from the temporal retina pass directly backward in the lateral chiasm to the optic tract, whereas fibers from the nasal retina cross to the contralateral optic tract. Crossings take place in the paracentral regions of the chiasm rather than in the center of the chiasm (where the nerve fibers are traveling mostly in parallel). The paracentral crossing regions are distributed in a largely postero-superior to antero-inferior arrangement.
  
  
  CONCLUSIONS
  These findings clarify the precise locations and crossing angles of crossing nerve fibers in the chiasm. This information may help explain the clinical observation of junctional scotoma and will provide a much better basis for structural modeling of chiasmal compression which, in turn, will improve our understanding of how and why bitemporal hemianopia occurs.
authors.affiliation: Department of Neurology, The Canberra Hospital, Canberra, Australian Capital Territory, Australia 2Faculty of Medicine, University of New South Wales, Kensington, Sydney, New South Wales, Australia.
authors.forename: Neeranjali S
authors.initials: NS
authors.lastname: Jain
authors.affiliation: Department of Neurology, The Canberra Hospital, Canberra, Australian Capital Territory, Australia 2Faculty of Medicine, University of New South Wales, Kensington, Sydney, New South Wales, Australia.
authors.forename: Swaranjali V
authors.initials: SV
authors.lastname: Jain
authors.affiliation: School of Engineering and Information Technology, University of New South Wales, Canberra, Australian Capital Territory, Australia.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Engineering and Information Technology, University of New South Wales, Canberra, Australian Capital Territory, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Neely
authors.affiliation: School of Engineering and Information Technology, University of New South Wales, Canberra, Australian Capital Territory, Australia.
authors.forename: Murat
authors.initials: M
authors.lastname: Tahtali
authors.affiliation: Department of Anatomical Pathology, The Canberra Hospital, Canberra, Australian Capital Territory, Australia 5Australian National University Medical School, Canberra, Australian Capital Territory, Australia.
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Jain
authors.affiliation: Department of Neurology, The Canberra Hospital, Canberra, Australian Capital Territory, Australia 5Australian National University Medical School, Canberra, Australian Capital Territory, Australia.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Lueck
mesh_terms: D002102:Cadaver; D003251:Constriction, Pathologic / Q000150:complications; D006423:Hemianopsia / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009897:Optic Chiasm / Q000033:anatomy & histology* / Q000166:cytology; D010784:Photomicrography