In a recent study published in the journal Heliyon, researchers conducted an evaluation of oculomotor function changes during prolonged computer usage using an eye tracker to collect data on eye movement at various intervals of screen time.
The increasing use of digital devices in all fields of occupation is resulting in a range of vision-related symptoms referred to as Computer Vision Syndrome (CVS), affecting close to 90% of individuals who spend at least three hours every day looking at a computer screen.
Prolonged screen time has been associated with an increase in various ocular problems, such as eye irritation, strain, redness, and double or blurred vision. This also affects the individual’s ability to concentrate and, subsequently, their productivity.
The eye tracker has been an important invention for measuring the physiological and psychological aspects of an individual, with widespread applications in studying autism spectrum disorders, education, cognition, and mental state, as well as during criminal investigations.
It can measure various aspects of oculomotor function, such as gaze position, pupil diameter, saccade, blinking, nystagmus, and gaze duration. The steady tracking of objects in motion, also known as smooth pursuit, has also been studied using the eye tracker and is indicative of cognitive processes such as learning, attention, prediction, and selection.
About the study
In the present study, postgraduate students between the ages of 22 and 25 studying at a university were recruited as participants, and only those individuals who had normal vision and no history of neurological or any other significant disease, psychiatric disorder, or ocular surgery were included. Data was obtained using an eye tracker mounted to a computer monitor and calibrated for each experiment.
The experiment consisted of a gaze task, a smooth pursuit task at two different speeds, and a saccade task, with the participant being asked to track a moving or motionless target on the screen while the eye tracker recorded the movement data. The researchers used a grey background with a target comprising a black outer circle and a red inner circle. The number of pixels varied for the saccade and gaze tasks.
The gaze task involved the participants looking at nine targets on the screen that appeared sequentially on the screen, and they were required to look at the target for 10 seconds. They were instructed to look at the inner red circle for each target and switch quickly to the inner red circle of the next target as soon as it appeared. For the smooth pursuit experiment, the participants were instructed to focus on the inner red circle and follow the target as it moved across the screen.
The saccade task used a matrix composed of nine rows and nine columns, with 18 numbered boxes, where the target appeared randomly in any box on the matrix, and the participants were required to locate the target as soon as it appeared and call out the number of the box. The data from all three tasks were collected at 60 minutes and 90 minutes of continuous screen time.
The results indicated that long periods of looking at the computer screen decreased oculomotor function, and reductions in the stability and focus of the gaze were observed with increasing screen time. The smooth pursuit function and eye saccade speeds were also observed to decrease with increasing time spent looking at the computer screen.
The accuracy of the gaze was found to decrease during the gaze task after an hour of looking at the screen, and the saccade task reported an increase in saccade latency.
Furthermore, studies have reported that the saccade index is linked to attention, and the physiological changes that occur due to prolonged screen time, such as headaches, double or blurred vision, eye fatigue, and back and neck pain, impact the gaze precision, increasing the number of saccades.
The total gaze time is correlated to the concentration with which the subject gazes at the target, and it was found that the difference in absolute gaze time increased with increasing screen time, also indicating a decrease in search performance.
Overall, the study quantificationally demonstrated that prolonged screen time and working on digital devices worsens oculomotor function, with reduced gaze stability and focus and lower smooth pursuit function and eye saccade speeds. The study also presents an efficient method using the eye tracker to evaluate oculomotor function for occupations where excellent visual abilities are critical.