Figure 4

Model of nerve fiber bundle trajectories. (A–C) The topographic organization of optic nerve fiber bundles is highly stereotyped in the human retina (adapted with permission from ref.³²). Fundus images from 55 human eyes (A) were superimposed by translation in order to center the foveola (B), followed by rotation and zooming to align the center of the optic disc (C). Electrical stimulation (red circle) of a nerve fiber bundle could antidromically activate ganglion cell bodies peripheral to the point of stimulation (small black circles), leading to percepts that appear elongated along the direction of the underlying nerve bundle trajectory. (D–E) The location and orientation of each subject’s implant (Subject 4 shown here) was estimated by combining their postsurgical fundus photograph (D, bottom) with a baseline presurgical image in which the fovea had been identified (D, top) to produce a registered image (E; □: foveal pit, o- optic disc). The horizontal raphe (D, white line) was approximated by fitting a parabola to the main vascular arcade and finding the tangent to the parabola inflexion point. (F) The extracted landmarks were then used to place a simulated array on a simulated map of nerve fiber bundles.