Abstract
Purpose :
The purpose of this study was to test the hypothesis that caffeine consumption alters fixational eye motion (FEM) including microsaccade and drift parameters as measured by tracking scanning laser ophthalmoscopy (TSLO).
Methods :
Forty-five subjects (34 female) with a mean age of 30 years (range 22-59) participated in the study. Participants reported after at least 10 hours without caffeine consumption. After informed consent, participants FEM was measured with at least three, 10-second videos per eye per task using a custom-built TSLO with a 5x5-degree imaging raster. The three fixation tasks with respect to the imaging raster included: upper-right corner (UR), free fixation on the center (Free), and a blinking dot (Dot). The subjects were then provided either a 100mg caffeine pill (23 subjects) or a placebo (22 subjects) and measurements were repeated after one hour. Offline, custom MATLAB software was used to stabilize the videos, extract eye motion at 480 Hz, and compute quantitative measures of FEM. A multivariable model controlling for covariates (sex, eye, task, etc) was used to compare TSLO FEM measurements.
Results :
No differences were found at baseline between the caffeine and placebo groups. No differences were found in any comparisons between fixation target types. After caffeine/placebo, no significant differences were seen in the number of microsaccades or any microsaccade parameter (amplitude, acceleration, etc). Significant differences were seen in drift components of FEM comparing the two groups after caffeine/placebo, specifically the drift amplitude after caffeine was 0.82° vs after placebo 1.04° (P<.001). Mean drift horizonal (P=.02) and vertical (P<.001), drift proportion (P=.01), and blink frequency (P<.001) were also statistically significantly different between groups.
Conclusions :
Caffeine and placebo groups exhibited similar FEM for microsaccades parameters, but differed in drift parameters and blink rate, indicating that fixational drift and blink rate may be impacted by caffeine intake. Further evaluation will be necessary to conclude if caffeine must be considered when using TSLO measurements of FEM in clinical studies.
This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.