Individuals with amblyopia, often known for reduced visual acuity, have been found to experience motion perception deficits, particularly at slower speeds. While fixation stability has been previously linked to motion processing, new research from the University of British Columbia suggests these two factors may not be as connected as once thought.
The study, published on April 24, 2025, investigated the relationship between fixation stability and motion perception deficits by assessing coherence thresholds during direction discrimination tasks. Led by researchers Kimberly Meier, Sarah Warner, and Mathias Spering, the research involved two groups: adults with amblyopia and healthy control participants.
Participants underwent testing to determine how well they could discern the direction of motion at slow (1 degree/second) and fast (30 degrees/second) speeds. While subjects with amblyopia exhibited elevated coherence thresholds at slow speeds—consistent with prior findings—no significant correlation was found between their fixation stability and motion perception ability.
“These results suggest motion perception deficits might not be due to poor input to the motion processing system due to unstable fixation, but rather due to processing deficits in motion-sensitive visual areas,” explained Meier. Despite displaying less stable fixation during motion tasks, subjects with amblyopia did not show different levels of stability depending on the speed of the stimuli.
The researchers utilized the Bivariate Contour Ellipse Area (BCEA) to measure fixation stability and found no correlation between visual acuity and stability. Typical visual acuity was not associated with the coherence thresholds, contradicting earlier assumptions connecting poorer fixation stability to decreased visual processing quality.
“While fixation instability has been established, its contribution to perceptual deficits is not supported by our findings,” said Warner. This key takeaway indicates the need to shift focus from merely observing lower fixation stability as the primary cause of motion perception issues.
The study adds to the body of evidence indicating the complexity of visual processing, especially for those with amblyopia. Although patients with amblyopia have difficulty integrating motion signals, this research provides clarity on how fixation is less likely to be the root cause of such deficits.
“Our study does not find convincing evidence to link fixation stability to performance on motion perception tasks,” Spering noted. This conclusion points toward the need for exploring other factors impacting motion perception, possibly within higher-order cortical processing mechanisms.
Future research may aim to investigate potential links between motion perception deficits and reflexive tracking responses, such as smooth pursuit or the optokinetic nystagmus (OKN) response, which could offer additional insights for steering treatments for amblyopia.
The team’s findings underline the importance of revisiting assumptions about how eye movements affect visual perception and could reshape approaches to diagnosing and treating motion perception deficiencies among individuals with amblyopia.