Comments on "Effect of Vergence Adaptation on Convergence Accommodation: Model Simulations

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Sreenivasan et al. have used an inappropriate measure to estimate convergence accommodation under closed-loop (CL) accommodation and vergence, which they then used to compare the two adaptation models. In [1, Fig. 8(b)], they used a dual-scale plot to exaggerate the small change in experimental dynamics, but such a plot could only appropriately provide a comparison of steady-state level responses. Quantitative analysis of the static model of accommodation and vergence showed that subtraction of CL and open-loop (OL) responses resulted in a small numerical value, which is close to the authors' experimentally derived value. The authors had assumed erroneously that such a difference would represent the convergence accommodation response. But their value is very different from the large numerical value for convergence accommodation calculated analytically. In the model simulations, the large difference in steady-state convergence accommodation levels for the two models provides a means to assess their appropriateness. Schor's model response exhibited a very small value. On the other hand, Hung's model response exhibited a large value, which is close to the level calculated analytically.