Fig 1.
Haploscopic system and representative examples of vergence movements measured with the experimental set-up.
(a) Schematic representation of the haploscopic system used in the present study: (1) and (2) monitors, (3) and (4) cold mirrors, and (5) chin rest. The three circles in each screen represent three different stimulus positions. The two green stimuli drive the same convergence angle as a real stimulus placed at 40 cm in front of the subject, represented by the light green circle. Thus, this is the stimuli’s starting position (0 PD). Relative to this position, the yellow and blue stimuli in the two monitors drive fusional divergence and convergence, respectively. (b) and (c) Representative examples of vergence movements measured with EyeLink (in blue) during a negative fusional vergence amplitude measure with the smooth objective test (b), and a positive fusional vergence amplitude measure with the step objective test (c). The vergence demand driven by the stimuli is shown in black. The red and green vertical lines represent the time of the break and recovery points determined objectively.
Fig 2.
Boxplots of the median and interquartile range (IQR) of the fusional vergence amplitudes measured with the four tests.
Base-In (BI) break points (a), BI recovery points (b), Base-Out (BO) break points (c), and BO recovery points (d) measured with the four tests. * indicates statistically significant differences between the tests (corrected p-value < 0.008). PD (Prism Dioptre), Subj. (Subjective), and Obj. (Objective).
Fig 3.
Bland-Altman plots comparing the results obtained with the smooth and step subjective tests.
(a) Base-In (BI) break point, (b) BI recovery point, (c) Base-Out (BO) break point, and (d) BO recovery point. Black horizontal lines correspond to the mean of the differences between tests, and red horizontal lines show the 95% limits of agreement. Black dots correspond to the participants who did not exhibit loss of motor fusion and were assigned a break point of 40 PD.
Fig 4.
Bland-Altman plots comparing the results obtained with the smooth and step objective tests.
(a) Base-In (BI) break point, (b) BI recovery point, (c) Base-Out (BO) break point, and (d) BO recovery point. Black horizontal lines correspond to the mean of the differences between tests, and red horizontal lines show the 95% limits of agreement. Black dots correspond to the participants who did not exhibit loss of motor fusion and were assigned a break point of 40 PD.
Fig 5.
Bland-Altman plots comparing the results obtained with the smooth objective and subjective tests.
(a) Base-In (BI) break point, (b) BI recovery point, (c) Base-Out (BO) break point, and (d) BO recovery point. Black horizontal lines correspond to the mean of the differences between tests, and red horizontal lines show the 95% limits of agreement. Black dots correspond to the participants who did not exhibit loss of motor fusion and were assigned a break point of 40 PD.
Fig 6.
Bland-Altman plots comparing the results obtained with the step objective and subjective tests.
(a) Base-In (BI) break point, (b) BI recovery point, (c) Base-Out (BO) break point, and (d) BO recovery point. Black horizontal lines correspond to the mean of the differences between tests, and red horizontal lines show the 95% limits of agreement. Black dots correspond to the participants who did not exhibit loss of motor fusion and were assigned a break point of 40 PD.