Abstract
Purpose :
To quantify inter & intra-day variability of microsaccades in a cohort of young, healthy controls.
Methods :
We used a custom-built retinal tracker, the TSLO, to record microsaccades in a cohort of 14 healthy controls, ages < 40 years, at 9 different time points (3x a day (morning, afternoon & evening), for 3 days). Each session had 3 videos recorded per eye (6 traces per subject per session). Individuals were instructed to fixate for 10s on the upper right-hand corner of a 5°x5° imaging raster. Microsaccade characteristics of frequency, amplitude, peak velocity, & peak acceleration were calculated & compared for all time points to determine inter & intra-day variability & overall variation between subjects. Descriptive statistics were used to characterize measures of central tendency & variation for each of the microsaccade metrics.
Results :
Our sample consisted of 14 participants, 121 sessions, & 608 traces. Participants had an average (std) microsaccade frequency of 0.84 Hz (0.52), average amplitude of 0.32° (0.11), average peak velocity of 43.68 °/s (14.02), & average peak acceleration of 13,920.04 °/s2 (4,186.84). In general, we found only modest evidence of variability between traces, with consistently higher peak velocity &/or acceleration values for the 1st trace of each session. Trace 2 had a significantly lower average peak velocity of 3.93 °/s (p=0.02) & lower peak acceleration of 1,312.30 °/s2 (p=0.023) than trace 1. Additionally, trace 3 had a significantly lower average peak acceleration than trace 1 by 1,657.14 °/s2 (p=0.009). We detected a negligibly higher vertical velocity of 1.75 °/s (p=0.017) in trace 3 when compared to trace 2. Microsaccade frequency was the only metric to have a significant time of day difference, with evening values being slightly higher than morning recordings (0.098 Hz, p=0.007). We found no statistically significant differences in day-to-day measurements & no significant learning effect from session to session was observed in the metrics.
Conclusions :
Utilizing our fixation stimuli & a 10 second recording paradigm, trace 1 showed statistical differences when compared to subsequent traces within a session. We saw a modest increase in the number of microsaccades between morning & evening sessions. No statistically significant differences in day-to-day measurements of microsaccades were observed, revealing no significant learning effect.
This is a 2021 ARVO Annual Meeting abstract.