Individuals with macular degeneration (MD) experience great variability in saccades direction and frequency, according to a study published in Vision Research. These findings suggest that the increased saccades noted during pursuit in patients with MD are unlikely to be catch-up saccades that attempt to keep the eye on the target.
Researchers enrolled 7 individuals with MD (mean age, 77.9 years; 4 women; 6 age-related macular degeneration [AMD]; 1 Stargardt’s disease) and 4 age-matched control individuals in the analysis. Patients underwent saccades testing in which they pursued high contrast targets moving in 1 of 6 possible directions (4 cardinal, 2 oblique). Patients viewed the targets binocularly and monocularly, and approximately 90 trials were performed per viewing condition.
Overall, participants with MD experienced larger variability in saccade direction—including those orthogonal to the target. Saccades in the non-target direction occurring during smooth pursuit were associated with peripheral retinal locus (PRL) eccentricity.
The number of saccades was not statistically different between individuals with MD and control group participants across all viewing conditions, and the number of saccades was higher during pursuit for participants in both groups (P <.001).
“Our study indicated that participant heterogeneity is an important factor to consider in future work,” according to the researchers. “Overall, our results suggest that those with MD are unable to fully overcome the limitations of consistently using an eccentric locus as an oculomotor reference for saccades during a smooth pursuit task.”
Study limitations include a small sample size and an inability to visualize the retinal locus used for pursuit due to the use of an eye tracker for eye position measurements.
Shanidze NM, Lively Z, Lee R, Verghese P. Saccadic contributions to smooth pursuit in macular degeneration. Vision Res. Published online July 20, 2022. doi:10.1016/j.visres.2022.108102