title: Virtual tissue engineering and optic pathways: plotting the course of the axons in the retinal nerve fiber layer.
abstract: OBJECTIVE
  As part of a larger project on virtual tissue engineering of the optic pathways, we describe the conditions that guide axons extending from the retina to the optic nerve head and formulate algorithms that meet such conditions. To find the entrance site on the optic nerve head of each axon, we challenge the fibers to comply with current models of axonal pathfinding.
  
  
  METHODS
  First, we build a retinal map using a single type of retinal ganglion cell (RGC) using density functions from the literature. Dendritic arbors are equated to receptive fields. Shape and size of retinal surface and optic nerve head (ONH) are defined. A computer model relates each soma to the corresponding entry point of its axon into the optic disc. Weights are given to the heuristics that guide the preference entry order in the nerve.
  
  
  RESULTS
  Retinal ganglion cells from the area centralis saturate the temporal section of the disc. Retinal ganglion cells temporal to the area centralis curve their paths surrounding the fovea; some of these cells enter the disc centrally rather than peripherally. Nasal regions of the disc receive mixed axons from the far periphery of the temporal hemiretina, together with axons from the nasal half. The model plots the course of the axon using Bezier curves and compares them with clinical data, for a coincidence level of 86% or higher.
  
  
  CONCLUSIONS
  Our model is able to simulate basic data of the early optic pathways including certain singularities and to mimic mechanisms operating during development, such as timing and fasciculation.
authors.affiliation: Department of Surgery (Ophthalmology), Faculty of Medicine, University of Granada, Granada, Spain.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Carreras
authors.affiliation: School of Computer Science, Department of Computer Science and Artificial Intelligence, University of Granada, Granada, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Medina
authors.affiliation: School of Computer Science, Department of Computer Science and Artificial Intelligence, University of Granada, Granada, Spain.
authors.forename: Mariola
authors.initials: M
authors.lastname: Ruiz-Lozano
authors.affiliation: School of Computer Science, Department of Computer Science and Artificial Intelligence, University of Granada, Granada, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Carreras
authors.affiliation: School of Computer Science, Department of Computer Science and Artificial Intelligence, University of Granada, Granada, Spain.
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Castro
mesh_terms: D000465:Algorithms; D001369:Axons / Q000648:ultrastructure; D003198:Computer Simulation; D006801:Humans; D008953:Models, Anatomic; D009898:Optic Disk / Q000166:cytology; D012165:Retinal Ganglion Cells / Q000166:cytology*; D023822:Tissue Engineering / Q000379:methods*; D014795:Visual Pathways / Q000166:cytology*
keywords: computer modeling; course of axons; optic pathways; retinal ganglion cell layer