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. 2021 Feb 1;62(2):23.
doi: 10.1167/iovs.62.2.23.

The Flash-lag Effect in Amblyopia

Xi Wang  1   2 , Alexandre Reynaud  2 , Robert F Hess  2
Affiliations

The Flash-lag Effect in Amblyopia

Xi Wang et al. Invest Ophthalmol Vis Sci. .

Abstract

Purpose: Amblyopes suffer a defect in temporal processing, presumably because of a neural delay in their visual processing. By measuring flash-lag effect (FLE), we investigate whether the amblyopic visual system could compensate for the intrinsic neural delay due to visual information transmissions from the retina to the cortex.

Methods: Eleven adults with amblyopia and 11 controls with normal vision participated in this study. We assessed the monocular FLE magnitude for each subject by using a typical FLE paradigm: a bar moved horizontally, while a flashed bar briefly appeared above or below it. Three luminance contrasts of the flashed bar were tested: 0.2, 0.6, and 1.

Results: All participants, controls and those with amblyopia, showed a typical FLE. However, the FLE magnitude of participants with amblyopia was significantly shorter than that of the control participants, for both their amblyopic eye (AE) and fellow eye (FE). A nonsignificant difference was found in FLE magnitude between the AE and the FE.

Conclusions: We demonstrate a reduced FLE both in the AE as well as the FE of patients with amblyopia, suggesting a global visual processing deficit. We suggest it may be attributed to a more limited spatiotemporal extent of facilitatory anticipatory activity within the amblyopic primary visual cortex.

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Conflict of interest statement

Disclosure: X. Wang, None; A. Reynaud, None; R.F. Hess, None

Figures

Figure 1.
Figure 1.
(A) The left panel illustrates the physical stimuli. In this example, one bar moved horizontally rightward toward the vertical meridian in the left hemifield. The flashed bar is presented at the time when the moving and flashed bar are physically aligned. The right panel illustrates the typical perception: the moving bar is perceived to be ahead of the flashed bar. (B) Psychometric function of one representative participant in the experiment: Proportion of “left” response as a function of the relative timing of the appearance of the flashed bar. Negative value means the flashed bar was presented before the moving bar physically aligned with the flashed bar. Datapoints are fitted with a logistic function. PSE, point of subjective equality.
Figure 2.
Figure 2.
Mean FLE magnitude of the two groups under different contrast conditions (A–C). Results are compared between the eyes (filled versus open bars) of healthy control group and amblyopic group (blue and orange, respectively). FLE, flash-lag effect; DE, dominant eye; NDE, non-dominant eye; FE, fellow eye; AE, amblyopic eye. Error bars represent the standard errors. ***P ≤ 0.001; **P < 0.01; *P < 0.05.
Figure 3.
Figure 3.
FLE amplitude differences between the low contrast conditions and the full contrast condition in the two eyes (filled versus open bars). (A) control group. (B) amblyopic group. FLE, flash-lag effect; Error bars represent the standard errors. **P < 0.01; *P < 0.05.
Figure 4.
Figure 4.
Mean magnitude of FLE in experienced (dark color bars) and nonexperienced (light color bars) groups for controls (blue bars, left pair) and amblyopes (orange bars, right pair). FLE, flash-lag effect; EX, experienced group; NEX, nonexperienced group. Error bars represent the standard errors. n.s., not significant.
See this image and copyright information in PMC

References

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