Hung G K
Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854-8014, USA.
IEEE Trans Biomed Eng. 1998 Mar;45(3):335-41. doi: 10.1109/10.661158.
The effect of parameter variation of a nonlinear static feedback control model of the accommodation system was investigated. Simulations of a MATLAB/SIMULINK model showed a nonlinear relationship between stimulus and response in which the response curve was above the 1:1 line in the region to the left of the crossover and below the 1:1 line in the region to the right of the crossover. At the crossover, the response curve exhibited an inflection that was constant and equal to the tonic accommodation value (ABIAS). Sensitivity analysis showed that increasing depth of focus (deadspace range between +/- DSP) increased the separation between the boundary lines of the deadspace region, with a larger separation associated with late-onset myopia and congenital nystagmus. Increasing accommodative controller gain (ACG) increased the slope of the function on either side of the deadspace, with lower ACG values corresponding to lower slopes that indicated an amblyopic deficit. Increasing ABIAS increased the accommodative level at the inflection region. In addition, the saturation level of the accommodative response decreased with increasing age, while the slope remained the same, which was consistent with the Hess-Gullstrand theory of presbyopia. The accuracy and relative simplicity of the model indicated that it could serve as a basis for further comprehensive investigation of the basic and clinical aspects of the accommodation system.
研究了调节系统非线性静态反馈控制模型参数变化的影响。MATLAB/SIMULINK模型的仿真显示，刺激与反应之间存在非线性关系，其中在交叉点左侧区域反应曲线高于1:1线，在交叉点右侧区域反应曲线低于1:1线。在交叉点处，反应曲线呈现出一个恒定的拐点，且该拐点等于张力性调节值（ABIAS）。敏感性分析表明，增加焦深（+/- DSP之间的死区范围）会增加死区区域边界线之间的间距，较大的间距与迟发性近视和先天性眼球震颤相关。增加调节控制器增益（ACG）会增加死区两侧函数的斜率，较低的ACG值对应较低的斜率，表明存在弱视缺陷。增加ABIAS会提高拐点区域的调节水平。此外，调节反应的饱和水平随年龄增长而降低，而斜率保持不变，这与老花眼的赫斯-古尔斯特兰德理论一致。该模型的准确性和相对简单性表明，它可作为进一步全面研究调节系统基础和临床方面的基础。
