Quantification of tracking eye movements in normal subjects

Area of Science:

• Ophthalmology
• Neuroscience
• Human Motor Control

Background:

• Voluntary tracking eye movements are crucial for visual-motor tasks.
• Understanding the interplay between smooth pursuit and saccadic eye movements is essential for diagnosing visual-motor deficits.

Purpose of the Study:

• To quantify the effects of increasing target velocities on smooth pursuit and saccadic eye movements.
• To investigate the influence of learning on tracking accuracy and eye movement parameters.

Main Methods:

• Analysis of voluntary tracking eye movements in 20 normal subjects at constant target velocities (10-60 degrees/s).
• Quantification of tracking ability using four parameters: velocity gain, amplitude, saccade frequency, and square wave occurrence.
• Repeated testing of 9 subjects to assess learning effects.

Main Results:

• Maximum velocity gain of smooth pursuit decreased from 0.98 to 0.75 with increasing target velocities.
• Smooth pursuit amplitude decreased, and superimposed saccades increased with higher target velocities.
• Saccades >10 degrees were more frequent at velocities >30 degrees/s; square waves occurred randomly.

Conclusions:

• Tracking accuracy diminishes with increasing target velocity due to reduced smooth pursuit and increased saccadic intrusions.
• Learning positively impacts tracking performance, suggesting adaptability in the oculomotor system.
• The study highlights the coordinated function of smooth pursuit and saccadic subsystems in voluntary visual tracking.