A dual-mode dynamic model of the human accommodation system

Bulletin of Mathematical Biology
Madjid Khosroyani, George K Hung

Abstract

The function of the accommodation system is to provide a clear retinal image of objects in the visual scene. The system was previously thought to be under simple continuous (i.e., single mode of operation) feedback control, but recent research has shown that it is under discontinuous (i.e., two stimulus-dependent modes of operation) feedback control by means of fast and slow processes. A model using MATLAB/SIMULINK was developed to simulate this dual-mode behavior. It consists of fast and slow components in a feedback loop. The fast component responds to step target disparity with an open-loop movement to nearly reach the desired level, and then the slow component uses closed-loop feedback to reduce the residual error to an acceptable small level. For slow ramps, the slow component provides smooth tracking of the stimulus, whereas for fast ramps, the fast component provides accurate staircase-like step responses. Simulation of this model using a variety of stimuli, including pulse, step, ramp, and sinusoid, showed good agreement with experimental results. Thus, this represents the first dynamic model of accommodation that can accurately simulate the complex dual-mode behavior seen experimentally. The biological significance of ...Continue Reading

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Citations

Feb 2, 2006·Annals of Biomedical Engineering·Verica Radisavljevic-Gajic
Jan 25, 2011·Biomedical Optics Express·Karen M HampsonEdward A H Mallen
Sep 3, 2013·Vision Research·Alistair P CurdEdward A H Mallen
Mar 1, 2005·Vision Research·Clifton M Schor, Shrikant R Bharadwaj
Nov 18, 2005·Vision Research·Clifton M Schor, Shrikant R Bharadwaj
Jun 10, 2016·Journal of the Royal Society, Interface·John MiltonTamás Insperger
May 21, 2019·Optometry and Vision Science : Official Publication of the American Academy of Optometry·Carles OteroJaume Pujol

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