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Bulletin of Mathematical Biology

, Volume 64, Issue 2, pp 285–299 | Cite as

A dual-mode dynamic model of the human accommodation system

  • Madjid Khosroyani
  • George K. HungEmail author
Article

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 this model is that it can be used to quantitatively analyze clinical deficits such as amblyopia and accommodative insufficiency.

Keywords

Slow Component Fast Component Amblyopia Ciliary Muscle Accommodative Response 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Society for Mathematical Biology 2002

Authors and Affiliations

  1. 1.Department of Electrical EngineeringTarbiat Modarres UniversityTehranIran
  2. 2.Department of Biomedical EngineeringRutgers UniversityPiscatawayUSA

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