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Statistical artifacts in dynamic accommodation studies

Poster Details

First Author: A.Del Águila-Carrasco SPAIN

Co Author(s):    J. Esteve-Taboada   T. Ferrer-Blasco   N. López-Gil   R. Montés-Micó     

Abstract Details



Purpose:

To evaluate the effect of increase blinking in the calculus of the gain and the phase-lag of a dynamic accommodative response to a sinusoidally moving stimulus by means of computer simulations.

Setting:

University of Valencia, Spain

Methods:

The gain and the phase-lag of the accommodative response to a stimulus which vergence varies in a sinusoidal way from 1 to 3 D were obtained as follows: gain was calculated dividing the response amplitude by the stimulus amplitude, and phase-lag was computed as the distance in radians from the peak of the stimulus to the peak of the response. Matlab (Mathworks Inc.) was used for numerically simulate the effect of adding a defined number of blinks in the accommodative response following a uniform distribution. White noise was also added to the simulated response in order to achieve the maximum degree of similarity with real responses. In order to simplify the calculus, the temporal frequency of the stimulus was set to 0.24 Hz and it contained 10 cycles with total signal duration of 40.96 s.

Results:

The results obtained showed that as the number of blinks was increased, the gain of the accommodative response decreased. The average gain value was practically the theoretical one when there were no blinks in the signal; then it started to decrease linearly with the number of blinks. This happened regardless the difference in amplitude set for the two signals (stimulus and simulated accommodative response). As far as the phase-lag is concerned, it remained practically constant regardless the number of blinks added in the signal. The standard deviation of the phase-lag of all the iterations did increase as the number of blinks became greater.

Conclusions:

According to these simulations, when the number of blinks added to the simulated accommodative response becomes greater, the differences with the stimulus increase, modifying the gain of the accommodative response. This variation follows almost a linear function when plotting gain vs. number of blinks. The increase in the standard deviation of the phase-lag of all the iterations may indicate a more erratic behaviour in the accommodative response when the number of blinks becomes greater. Project funded by: ERC-2012-StG 309416-SACCO FINANCIAL INTEREST: NONE

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