Eye Movement Abnormalities in Glaucoma Patients: A Review

Characterization of Gaze Metrics and Visual Search Pattern Among Glaucoma Patients While Viewing Real-World Images

PRCIS

We quantified and compared the gaze metrics during target-oriented visual search tasks between glaucoma and healthy controls. On the basis of a mathematical concept we showed that due to glaucoma, focal search becomes prominent over global search.

PURPOSE

Visual search (VS) which is essential for target identification and navigation is significantly impacted by glaucoma. VS metrics can be influenced by differences in cultural exposure or coping strategies, leading to varying VS patterns. This study aimed to explore and label the pattern of VS based on gaze metrics quantified using eye-tracking technology.

METHODS

Twenty-seven glaucoma subjects and 30 healthy controls [median age 51 (14) and 54 (19) y, respectively] underwent a VS experiment during which they had to identify specific targets from real-world images. Eye movements were recorded using a remote eye-tracker and gaze metrics-fixation count (FC), fixation duration (FD), saccade amplitude (SA), and VS time (VST) were computed and compared between the study groups. A Z -score-based coefficient " K " was derived to label the search patterns as global ( K ≤ - 0.1: short FD with long SA), focal ( K ≥+0.1: long FD with short SA), or a combination ( K between ±0.1).

RESULTS

Similar to other ethnicities, Indian glaucoma subjects also exhibited statistically significantly increased FC, FD, and VST ( P =0.01). Healthy controls presented a comparable proportion of focal (47%) and global (42%) search patterns while glaucoma subjects exhibited predominantly focal (56%) than global search patterns (26%, P =0.008).

CONCLUSIONS

This study suggests that glaucoma subjects perform more focal searches during active gaze scanning. This change in viewing behavior reflects underlying compensatory strategies adapted for coping with their visual impairments. These search patterns can be influenced by factors such as saliency which requires further investigation.

Inhibitory control and working memory using saccadic eye movements in primary glaucoma

Glaucoma is a progressive optic neuropathic disorder that significantly impacts the activities of daily life (ADLs) of individuals. Emerging studies indicate degenerative changes in cortical and subcortical regions in individuals with glaucoma, which are associated with cognitive processes and oculomotor control. Cognitive processes involving top-down processes such as attention, planning, task management and execution, are crucial for meeting the demands of everyday tasks, and are affected in glaucoma. This study investigated the executive functions, specifically inhibitory control (IC) and working memory (WM), in individuals with glaucoma compared to age-matched controls, using eye movements. This was achieved through four tasks sensitive to executive functions, including antisaccade, memory-guided prosaccade and antisaccade, and the Go-NoGo tasks. Saccadic eye-movement parameters were also assessed in a prosaccade task, considered as a control condition with minimal IC and WM load. The results indicated that glaucoma is associated with changes in both IC and WM. Increased anticipatory saccadic errors might be linked to inhibitory deficiencies during the preparatory stage of the saccadic suppression mechanism. The increased omission errors in the antisaccade task might be due to the lack of regulation of the WM component. Taken together, these findings provide evidence for the involvement of cognitive deficits in individuals with glaucoma.

Gaze behavior in open-angle glaucoma patients during visuo-cognitive-motor tasks: a cross-sectional study

This study investigated gaze behavior during visuo-cognitive-motor tasks with a change of movement direction in glaucoma patients and healthy controls. Nineteen glaucoma patients (10 females, 9 males) and 30 healthy sighted controls (17 females, 13 males) participated in this cross-sectional study. Participants performed two visuo-cognitive-motor tasks with a change of movement direction: (i) the "Speed-Court-Test" that involved stepping on different sensors in response to a visual sign displayed on either a large or small screen (165″ and 55″, respectively); (ii) the "Trail-Walking-Test" that required walking to 15 cones labeled with numbers (1-8) or letters (A-G) in an alternately ascending order. During these tasks, the time needed for completing each task was determined and the gaze behavior (e.g., saccade duration, fixation duration) was recorded via eye tracking. Data were analyzed with repeated measures analyses of covariance (ANCOVA; GROUP × SCREEN) and one-way ANCOVA. No differences between groups were found for the time needed to complete the tasks. However, during the "Trail-Walking-Test", the fixation duration was longer for glaucoma patients than for controls (p = 0.016, η p 2  = 0.131). Furthermore, during the "Speed-Court-Test", there was a screen size effect. Irrespective of group, saccade amplitudes were lower (p < 0.001, η p 2  = 0.242) and fixation durations were higher (p = 0.021, η p 2  = 0.125) for the small screen. Fixation durations were longer in glaucoma patients during the cognitively demanding "Trail-Walking-Test", which might indicate a strategy to compensate for their visual impairment.

Investigating the impact of asymmetric macular sensitivity on visual acuity chart reading in choroideremia

INTRODUCTION

Degeneration in choroideremia, unlike typical centripetal photoreceptor degenerations, is centred temporal to the fovea. Once the fovea is affected, the nasal visual field (temporal retina) is relatively spared, and the preferred retinal locus shifts temporally. Therefore, when reading left to right, only the right eye reads into a scotoma. We investigate how this unique property affects the ability to read an eye chart.

METHODS

Standard- and low-luminance visual acuity (VA) for right and left eyes were measured with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. Letters in each line were labelled by column position. The numbers of letter errors for each position across the whole chart were summed to produce total column error scores for each participant. Macular sensitivity was assessed using microperimetry. Central sensitivity asymmetry was determined by the temporal-versus-nasal central macular difference and subsequently correlated to a weighted ETDRS column error score. Healthy volunteers and participants with X-linked retinitis pigmentosa GTPase regulator associated retinitis pigmentosa (RPGR-RP) were used as controls.

RESULTS

Thirty-nine choroideremia participants (median age 44.9 years [IQR 35.7-53.5]), 23 RPGR-RP participants (median age 30.8 years [IQR 26.5-40.5]) and 35 healthy controls (median age 23.8 years [IQR 20.3-29.0]) were examined. In choroideremia, standard VA in the right eye showed significantly greater ETDRS column errors on the temporal side compared with the nasal side (p = 0.002). This significantly correlated with greater asymmetry in temporal-versus-nasal central macular sensitivity (p = 0.04). No significant patterns in ETDRS column errors or central macular sensitivity were seen in the choroideremia left eyes, nor in RPGR-RP and control eyes.

CONCLUSION

Difficulty in tracking across lines during ETDRS VA testing may cause excess errors independent of true VA. VA assessment with single-letter optotype systems may be more suitable, particularly for patients with choroideremia, and potentially other retinal diseases with asymmetric central macular sensitivity or large central scotomas including geographic atrophy.

Oculometric biomarkers of visuomotor deficits in clinically asymptomatic patients with systemic lupus erythematosus undergoing long-term hydroxychloroquine treatment

Introduction

This study examines a set of oculomotor measurements, or "oculometric" biomarkers, as potential early indicators of visual and visuomotor deficits due to retinal toxicity in asymptomatic Systemic Lupus Erythematosus (SLE) patients on long-term hydroxychloroquine (HCQ) treatment. The aim is to identify subclinical functional impairments that are otherwise undetectable by standard clinical tests and to link them to structural retinal changes.

Methods

We measured oculomotor responses in a cohort of SLE patients on chronic HCQ therapy using a previously established behavioral task and analysis technique. We also examined the relationship between oculometrics, OCT measures of retinal thickness, and standard clinical perimetry measures of visual function in our patient group using Bivariate Pearson Correlation and a Linear Mixed-Effects Model (LMM).

Results

Significant visual and visuomotor deficits were found in 12 asymptomatic SLE patients on long-term HCQ therapy compared to a cohort of 17 age-matched healthy controls. Notably, six oculometrics were significantly different. The median initial pursuit acceleration was 22%, steady-state pursuit gain 16%, proportion smooth 7%, and target speed responsiveness 31% lower, while catch-up saccade amplitude was 46% and fixation error 46% larger. Excluding the two patients with diagnosed mild toxicity, four oculometrics, all but fixation error and proportion smooth, remained significantly impaired compared to controls. Across our population of 12 patients (24 retinae), we found that pursuit latency, initial acceleration, steady-state gain, and fixation error were linearly related to retinal thickness even when age was accounted for, while standard measures of clinical function (Mean Deviation and Pattern Standard Deviation) were not.

Discussion

Our data show that specific oculometrics are sensitive early biomarkers of functional deficits in SLE patients on HCQ that could be harnessed to assist in the early detection of HCQ-induced retinal toxicity and other visual pathologies, potentially providing early diagnostic value beyond standard visual field and OCT evaluations.

Assessing REALTER simulator: analysis of ocular movements in simulated low-vision conditions with extended reality technology

Immersive technology, such as extended reality, holds promise as a tool for educating ophthalmologists about the effects of low vision and for enhancing visual rehabilitation protocols. However, immersive simulators have not been evaluated for their ability to induce changes in the oculomotor system, which is crucial for understanding the visual experiences of visually impaired individuals. This study aimed to assess the REALTER (Wearable Egocentric Altered Reality Simulator) system's capacity to induce specific alterations in healthy individuals' oculomotor systems under simulated low-vision conditions. We examined task performance, eye movements, and head movements in healthy participants across various simulated scenarios. Our findings suggest that REALTER can effectively elicit behaviors in healthy individuals resembling those observed in individuals with low vision. Participants with simulated binocular maculopathy demonstrated unstable fixations and a high frequency of wide saccades. Individuals with simulated homonymous hemianopsia showed a tendency to maintain a fixed head position while executing wide saccades to survey their surroundings. Simulation of tubular vision resulted in a significant reduction in saccade amplitudes. REALTER holds promise as both a training tool for ophthalmologists and a research instrument for studying low vision conditions. The simulator has the potential to enhance ophthalmologists' comprehension of the limitations imposed by visual disabilities, thereby facilitating the development of new rehabilitation protocols.

Altered stability of dynamic brain functional architecture in primary open-angle glaucoma: a surface-based resting-state fMRI study

Delineating the neuropathological characteristics of primary open-angle glaucoma (POAG) is critical for understanding its pathophysiology. While temporal stability represents a crucial aspect of the brain's functional architecture, the specific patterns underlying its contribution to POAG remain unclear. This study aims to analyze the brain functional abnormalities in POAG using functional stability, a dynamic functional connectivity (DFC) approach based on resting-state functional magnetic resonance imaging (rs-fMRI). Seventy patients with POAG and forty-five healthy controls underwent rs-fMRI and ophthalmological examinations. The stability of DFC was calculated as the concordance of DFC over time using a sliding-window approach, and the differences in stability between the two groups were compared. Subsequently, Spearman's correlation analyses were conducted to examine the relationship between functional stability and clinical indicators. Compared with healthy controls, patients with POAG exhibited significantly decreased functional stability in the visual network, including the early visual center, ventral and dorsal stream visual cortex in both hemispheres. Conversely, stability values increased in the bilateral inferior parietal gyrus and right inferior frontal cortex. In POAG patients, the dynamic stability of the left early visual cortex and ventral stream visual cortex correlated with the mean deviation of visual field defects (r = 0.251, p = 0.037). The evidence from this study suggests that functional stability may provide a new understanding of brain alterations in the progression of POAG.

Eye tracking technology in medical practice: a perspective on its diverse applications

Eye tracking technology has emerged as a valuable tool in the field of medicine, offering a wide range of applications across various disciplines. This perspective article aims to provide a comprehensive overview of the diverse applications of eye tracking technology in medical practice. By summarizing the latest research findings, this article explores the potential of eye tracking technology in enhancing diagnostic accuracy, assessing and improving medical performance, as well as improving rehabilitation outcomes. Additionally, it highlights the role of eye tracking in neurology, cardiology, pathology, surgery, as well as rehabilitation, offering objective measures for various medical conditions. Furthermore, the article discusses the utility of eye tracking in autism spectrum disorders, attention-deficit/hyperactivity disorder (ADHD), and human-computer interaction in medical simulations and training. Ultimately, this perspective article underscores the transformative impact of eye tracking technology on medical practice and suggests future directions for its continued development and integration.

The impact of horizontal eye movements versus intraocular pressure on optic nerve head biomechanics: A tridimensional finite element analysis study

It has been proposed that eye movements could be related to glaucoma development. This research aimed to compare the impact of intraocular pressure (IOP) versus horizontal duction on optic nerve head (ONH) strains. Thus, a tridimensional finite element model of the eye including the three tunics of the eye, all of the meninges, and the subarachnoid space (SAS) was developed using a series of medical tests and anatomical data. The ONH was divided into 22 subregions, and the model was subjected to 21 different eye pressures, as well as 24 different degrees of adduction and abduction ranging from 0.5° to 12°. Mean deformations were documented along anatomical axes and in principal directions. Additionally, the impact of tissue stiffness was assessed. The results show no statistically significant differences between the lamina cribrosa (LC) strains due to eye rotation and IOP variation. However, when assessing LC regions some experienced a reduction in principal strains following a 12° duction, while after the IOP reached 12 mmHg, all LC subzones showed an increase in strains. From an anatomical perspective, the effect on the ONH following 12° duction was opposite to that observed after a rise in IOP. Moreover, high strain dispersion inside the ONH subregions was obtained with lateral eye movements, which was not observed with increased IOP and variation. Finally, SAS and orbital fat stiffness strongly influenced ONH strains during eye movements, while SAS stiffness was also influential under ocular hypertension. Even if horizontal eye movements cause large ONH deformations, their biomechanical effect would be markedly distinct from that induced by IOP. It could be predicted that, at least in physiological conditions, their potential to cause axonal injury would not be so relevant. Thus, a causative role in glaucoma does not appear likely. By contrast, an important role of SAS would be expectable.