Evaluating Silent Reading Performance with an Eye Tracking System in Patients with Glaucoma

Abstract

Objective: To investigate the relationship between silent reading performance and visual field defects in patients with glaucoma using an eye tracking system.

Methods: Fifty glaucoma patients (Group G; mean age, 52.2 years, standard deviation: 11.4 years) and 20 normal controls (Group N; mean age, 46.9 years; standard deviation: 17.2 years) were included in the study. All participants in Group G had early to advanced glaucomatous visual field defects but better than 20/20 visual acuity in both eyes. Participants silently read Japanese articles written horizontally while the eye tracking system monitored and calculated reading duration per 100 characters, number of fixations per 100 characters, and mean fixation duration, which were compared with mean deviation and visual field index values from Humphrey visual field testing (24-2 and 10-2 Swedish interactive threshold algorithm standard) of the right versus left eye and the better versus worse eye.

Results: There was a statistically significant difference between Groups G and N in mean fixation duration (G, 233.4 msec; N, 215.7 msec; P = 0.010). Within Group G, significant correlations were observed between reading duration and 24-2 right mean deviation (rs = -0.280, P = 0.049), 24-2 right visual field index (rs = -0.306, P = 0.030), 24-2 worse visual field index (rs = -0.304, P = 0.032), and 10-2 worse mean deviation (rs = -0.326, P = 0.025). Significant correlations were observed between mean fixation duration and 10-2 left mean deviation (rs = -0.294, P = 0.045) and 10-2 worse mean deviation (rs = -0.306, P = 0.037), respectively.

Conclusions: The severity of visual field defects may influence some aspects of reading performance. At least concerning silent reading, the visual field of the worse eye is an essential element of smoothness of reading.

Fig 1. Tobii Tx300 setup during the reading experiment.

Participants were evaluated during silent reading without a forehead and a chin rest in order to reproduce reading conditions in daily life. Participants were instructed not to lean forward in order to maintain the test distance. It is important to note that our reading experiment included the process of measuring either the point of gaze or the motion of an eye relative to the head. Therefore, we excluded data during saccades from the analysis of reading performance.

Fig 2. A participant’s gaze pattern during the reading experiment.

The articles contain both Japanese syllabary (Hiragana) and Chinese characters (Kanji). A participant reads sentences in a horizontal direction from left to right. The size of the circle corresponds to the fixation duration. The number in the circle is the rank of fixation. The lines represent saccades.