Static Behavior of Accommodation and Vergence: Computer Simulation of an Interactive Dual-Feedback System

The complex static behavior of accommodation (focusing) and vergence (eye-turn) of the human eye was modeled as an interactive dual-feedback system. Accommodative and vergence biases accounted for responses under the no stimulus condition. Analytical expressions were derived for relating the linear parameters in the model such as controller and cross gains to variables whose values could be obtained directly from experimental data. These parameters were incorporated into an interactive computer simulation program of the model. The computer simulation program was also used to obtain by trial and error the nonlinear parameters such as the lens plant saturation, accommodative controller gain for negative accommodative error, and the non-linear portion of vergence controller gain. The model responses show good agreement with critical experimental data.