How Free-Viewing Eye Movements Can Be Used to Detect the Presence of Visual Field Defects in Glaucoma Patients

Abstract

Purpose: There is a need for more intuitive perimetric screening methods, which can also be performed by elderly people and children currently unable to perform standard automated perimetry (SAP). Ideally, these methods should also be easier to administer, such that they may be used outside of a regular clinical environment. We evaluated the suitability of various methodological and analytical approaches for detecting and localizing VFD in glaucoma patients, based on eye movement recordings.Methods: The present study consisted of two experiments. In experiment 1, we collected data from 20 glaucoma patients and 20 age-matched controls, who monocularly viewed 28 1-min video clips while their eyes were being tracked. In experiment 2, we re-analyzed a published dataset, that contained data of 44 glaucoma patients and 32 age-matched controls who had binocularly viewed three longer-duration (3, 5, and 7 min) video clips. For both experiments, we first examined if the two groups differed in the basic properties of their fixations and saccades. In addition, we computed the viewing priority (VP) of each participant. Following a previously reported approach, for each participant, we mapped their fixation locations and used kernel Principal Component Analysis (kPCA) to distinguish patients from controls. Finally, we attempted to reconstruct the location of a patient's VFD by mapping the relative fixation frequency and the VP across their visual field.Results: We found direction dependent saccade amplitudes in glaucoma patients that often differed from those of the controls. Moreover, the kPCA indicated that the fixation maps of the two groups separated into two clusters based on the first two principal components. On average, glaucoma patients had a significantly lower VP than the controls, with this decrease depending on the specific video viewed.Conclusions: It is possible to detect the presence of VFD in glaucoma patients based on their gaze behavior made during video viewing. While this corroborates earlier conclusions, we show that it requires participants to view the videos monocularly. Nevertheless, we could not reconstruct the VFD with any of the evaluated methods, possibly due to compensatory eye movements made by the glaucoma patients.

Eye Tracking to Assess the Functional Consequences of Vision Impairment: A Systematic Review

“…However, there was no difference in the fixation duration or rate when watching video clips in either monocular or binocular viewing, nor in the saccadic amplitudes or saccadic velocity. 19 In contrast, Asfaw et al 50 showed that saccades were smaller in amplitude when viewing with the worse glaucomatous eye. The spread of fixations was smaller compared with both control participants and in the better eye.…”

“…The authors commented that, if the goal is to use eye tracking in clinical practice, this preparation time should be reduced significantly. 19 The use of trial lenses in frames to correct vision can pose an additional problem when comparing groups because the trial frame positioned in front of the eyes can restrict the visual field. Therefore, in the study by Smith et al, 48 all participants wore a trial frame, regardless of whether a correction was needed or not, to make sure that each participant had the same limitation.…”

“…Optom Vis Sci 2023; Vol 100 (12) Video clips with a duration of 1 to 7 minutes were used, typically displaying everyday footage of traffic, motion pictures, nature documentaries, or animated films. 19,52 The dependent variables that were extracted from the data were typically the number of saccades and fixations, fixation durations, saccadic amplitudes, saccadic velocity, and the scan path-the path followed by the participant's eye when observing a scene.…”

“…These repeated calibration procedures are time consuming; it was reported that it could take up to 25 minutes to be ready for data collection. 19 If the goal is to apply eye tracking in clinical practice, this preparation time needs to be minimized. One solution could be the use of a calibration-free eye tracker, such as the Pupil Labs Invisible from Pupil Labs GmbH.…”

“…Despite the potential complications when tracking the eyes of individuals with vision impairment, it seems, based on recent publications, [19][20][21] that eye tracking is increasingly being used to evaluate functional vision in the presence of vision impairment. Recent studies have, for instance, reported delayed saccadic latencies in individuals with glaucoma, 13 diminished fixation stability in amblyopic individuals, 20 and reduced performance in pursuing a moving stimulus in those with macular degeneration, 21 when compared with healthy control participants.…”