Events Calendar

AME Dept. Seminar

Speaker: Prof. Alfredo Sedun, University of Southern California

Talk Title: Engineering the Human Eye

Abstract:
The human eye reflects elements of design that represent an interesting tension between the rules of evolution (you need a path between steps and each step must at least not have a negative value added) and all sorts of tradeoffs between benefits that would have selection value. We will look at this process by asking how we might design such a system taking the following steps.

1) How big should it be?
a. Too small and you have >1.2mm aperture limit of diffraction
b. Too large and it’s neurologically (and metabolically) expensive
2) Do you grow it after birth (axial length changes require new focal lengths)?
3) How many pixels (separation of less than 30 seconds of arc = diffraction gratings)?
4) Scotopic vs Photopic (predator or prey)?
5) Transient or sustained (integrating over space or time)?
6) Duality approach of M & P cells (How is the hawk eye superior?)
7) Color vs B&W
8) How many color cones do we want (predator vs prey)?
9) Did you forget the heat sink?
10) Super-sustained RGCs (melanopsin) for
a. Pupils
b. Circadian rhythms

How do you get there from here: 10 step plan notwithstanding that evolution doesn’t have a trajectory.
1) Discriminating light vs dark = photopigment on a membrane (phototaxis and circadian rhythm)
2) Direction of light (light wall or just a cup)
3) Focus for better resolution (almost close the cup for pinhole aperture)
4) Maintain transparency (close with cornea, use aqueous and vitreous and IOP for sphere).
5) Movable iris to increase light
6) Lens to focus when pupil is not a pinhole
7) Deal with optic nerve that leaves the eye and makes a big blind spot (how do you keep the pressure in when you have an exit?).
8) Put psychophysical filters into the eye to decrease data and limit optic nerve head size by using Bipolars, Horizontals, Amacrine). Edges matter more than filler.
9) Fovea and eye movements
10) M & P cell parallel processing


Biography: Flora Thornton Chair of Vision Research, Professor of Ophthalmology and Neurological Surgery, Doheny Eye Institute, USC-Keck School of Medicine

Host: Professor Firdaus Udwadia

Location: Seaver Science Library (SSL) - 150

Audiences: Everyone Is Invited

Contact: April Mundy