The spontaneous blink rate (SBR) is variable in humans. It increases rapidly during childhood before reaching a plateau in adulthood at 10-20 blinks/minute. Our aim was to compare the SBR during different visual tasks in children.
Thirty-nine healthy participants (mean age(SD):13.6(3.5)years, M=21), made horizontal and vertical visually-guided saccades, tracked a horizontal and vertical target, performed horizontal and vertical active sinusoidal head rotations in light and darkness while looking straight ahead (VOR task) or fixated straight ahead and in four directions of gaze. The eyes of each participant were videotaped and reviewed twice to determine the SBR. Parametric and non-parametric tests were used to analyze the data.
The median SBR during fixation straight ahead was seven blinks/minute, which was similar to the SBR during horizontal saccades and horizontal smooth pursuit tasks. The median SBR during vertical smooth pursuit and vertical saccades were significantly lower than during fixation (p≤0.042). The median SBR during the VOR task in light and horizontal VOR in darkness were significantly higher than during fixation (p=0.019-0.024).
The median SBR during visual fixation was lower than that reported previously in 5-14 years-old children during rest or 11-20 years-old subjects during quiet conversation. The median SBR was even lower during vertical smooth pursuit and saccades tasks. This may be due to differences in concentration required for visual fixation in general and vertical visual tasks more specifically. The higher SBR during the VOR may be due to drying of the eyes during head shaking.