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Stimulus Unpredictability in Time, Magnitude, and Direction on Accommodation

Otero, Carles, PhD1,2*; Aldaba, Mikel, PhD2; Díaz-Doutón, Fernando, PhD2; Vera-Diaz, Fuensanta A., PhD, FAAO3; Pujol, Jaume, PhD2

Optometry and Vision Science: June 2019 - Volume 96 - Issue 6 - p 424–433
doi: 10.1097/OPX.0000000000001384
ORIGINAL INVESTIGATIONS
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SIGNIFICANCE The effect of predictability in changes of time, magnitude, and direction of the accommodation demand on the accommodation response latency and its magnitude are insignificant, which suggests that repetitive accommodative tasks such as the clinical accommodative facility test may not be influenced by potential anticipation effects.

PURPOSE The purpose of this study was to investigate the effect of stimulus' time, magnitude, and direction predictability, as well as their interactions, on accommodation latency and response magnitude.

METHODS Monocular accommodative response and latency were measured in 12 young subjects for nine different conditions where the stimulus accommodative demand changed several times in a steplike fashion for a period of 120 seconds. Each change in accommodative demand could have different time duration (i.e., 1, 2, or 3 seconds), magnitude (1, 2, or 3 diopters), and/or direction (i.e., accommodation or disaccommodation). All conditions were created permuting the factors of time, magnitude, and direction with two levels each: random and not random. The baseline condition was a step signal from 0 to 2 diopters persisting for 2 seconds in both accommodative demands. After each condition, subjects were asked to provide a score from 1 to 5 in their perceived predictability.

RESULTS Friedman test conducted on the perceived predictability of each condition resulted in statistically significant differences between the nine conditions (χ2 = 56.57, P < .01). However, repeated-measures analysis of variance applied to latency and accommodative response magnitude did not show significant differences (P > .05). In addition, no correlation was found between the perceived predictability scores and both latency and accommodative response magnitudes between the most predictable and the most unpredictable conditions.

CONCLUSIONS Subjects were able to perceptually notice whether the stimulus was predictable or not, although our results indicate no significant effect of stimuli predictability on either the accommodation latency or its magnitude.

1Vision and Eye Research Unit, School of Medicine, Anglia Ruskin University, Cambridge, United Kingdom

2Center for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Terrassa, Spain

3New England College of Optometry, Boston, Massachusetts *carles.otero@anglia.ac.uk

Supplemental Digital Content: Appendix Figure A1 (available at http://links.lww.com/OPX/A401). Comparison between the most predictable (no. 1) and unpredictable conditions (no. 9) for different inferior limits of the latency algorithm. The y axis is the number of cases where latency is <40 milliseconds. The x axis is the inferior limit set in latency algorithm; that it, we have allowed the algorithm to compute latencies from 0 (0 millisecond), 1 (−40 milliseconds), 2 (−80 milliseconds)…, 14 samples (−560 milliseconds) before the starting position of each accommodative transition.

Appendix Table A1 (available at http://links.lww.com/OPX/A402). Median latency obtained for each subject and experimental condition in accommodation (0 to 2 diopters) and disaccommodation (2 to 0 diopter). ACC = accommodation; DIS = disaccommodation.

Appendix Table A2 (available at http://links.lww.com/OPX/A403). Median accommodative response obtained for each subject and experimental condition in accommodation and disaccommodation. ACC = accommodation; DIS = disaccommodation.

Submitted: June 26, 2018

Accepted: February 17, 2019

Funding/Support: Ministerio de Economía, Industria y Competitividad, Gobierno de España (DPI2014-56850-R); H2020 European Research Council; and Davalor Salud, S.L.

Conflict of Interest Disclosure: None of the authors have reported a financial conflict of interest.

Author Contributions: Conceptualization: CO, MA, FD-D, FAV-D, JP; Data Curation: CO, FD-D; Formal Analysis: CO; Funding Acquisition: JP; Investigation: CO, FD-D, FAV-D; Methodology: CO, MA, FD-D, FAV-D; Project Administration: JP; Resources: FD-D, JP; Software: CO, FD-D; Supervision: CO, MA, FAV-D, JP; Validation: CO; Visualization: CO; Writing – Original Draft: CO, MA, FAV-D; Writing – Review & Editing: CO, MA, FD-D, FAV-D, JP.

Supplemental Digital Content: Direct URL links are provided within the text.

Online date: 17 5, 2019

© 2019 American Academy of Optometry