Saccadic eye movements and face recognition performance in patients with central glaucomatous visual field defects

Contrast Discrimination and Global Form Perception in Primary Open-Angle Glaucoma and Primary Angle-Closure Glaucoma

Purpose

This study explored early (contrast discrimination) and intermediate (global form perception) visual processing in primary subtypes of glaucoma: primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). We aimed to understand early and intermediate visual processing in POAG and PACG, matched for similar visual field defect severity.

Methods

Early visual processing was measured using a contrast discrimination task described by Porkorny and Smith (1997), and intermediate processing using a global form perception task using glass pattern coherence thresholds. Thresholds were determined centrally and at a single midperipheral location (12.5°) in a quadrant without visual field defects. Controls were tested in corresponding quadrants to individuals with glaucoma.

Results

Sixty participants (20 POAG, 20 PACG, and 20 age-matched controls), aged 50 to 77 years, were included. Visual field defects were matched between POAG and PACG, with mean deviation values of -6.53 ± 4.46 (range: -1.5 to -16.85) dB and -6.2 ± 4.24 (range: -1.37 to -16.42) dB, respectively. Two-Way ANOVA revealed significant differences in thresholds between the glaucoma groups and the control group for both contrast discrimination and global form perception tasks, with higher thresholds in the glaucoma groups. Post hoc analyses showed no significant contrast discrimination difference between POAG and PACG, but POAG had significantly higher thresholds than PACG for form perception.

Conclusions

In form perception, POAG showed slightly worse performance than PACG, suggesting that individuals with POAG may experience more severe functional damage than PACG of similar visual field severity.

Does the sampling frequency of an eye tracker affect the detection of glaucomatous visual field loss?

PURPOSE

Evidence suggests that eye movements have potential as a tool for detecting glaucomatous visual field defects. This study evaluated the influence of sampling frequency on eye movement parameters in detecting glaucomatous visual field defects during a free-viewing task.

METHODS

We investigated eye movements in two sets of experiments: (a) young adults with and without simulated visual field defects and (b) glaucoma patients and age-matched controls. In Experiment 1, we recruited 30 healthy volunteers. Among these, 10 performed the task with a gaze-contingent superior arcuate (SARC) scotoma, 10 performed the task with a gaze-contingent biarcuate (BARC) scotoma and 10 performed the task without a simulated scotoma (NoSim). The experimental task involved participants freely exploring 100 images, each for 4 s. Eye movements were recorded using the LiveTrack Lightning eye-tracker (500 Hz). In Experiment 2, we recruited 20 glaucoma patients and 16 age-matched controls. All participants underwent similar experimental tasks as in Experiment 1, except only 37 images were shown for exploration. To analyse the effect of sampling frequency, data were downsampled to 250, 120 and 60 Hz. Eye movement parameters, such as the number of fixations, fixation duration, saccadic amplitude and bivariate contour ellipse area (BCEA), were computed across various sampling frequencies.

RESULTS

Two-way ANOVA revealed no significant effects of sampling frequency on fixation duration (simulation, p = 0.37; glaucoma patients, p = 0.95) and BCEA (simulation, p = 0.84; glaucoma patients: p = 0.91). BCEA showed good distinguishability in differentiating groups across different sampling frequencies, whereas fixation duration failed to distinguish between glaucoma patients and controls. Number of fixations and saccade amplitude showed variations with sampling frequency in both simulations and glaucoma patients.

CONCLUSION

In both simulations and glaucoma patients, BCEA consistently differentiated them from controls across various sampling frequencies.

Spatial attention and central crowding in primary open angle glaucoma

CLINICAL RELEVANCE

Measuring the impact of spatial attention on signal detection in damaged parts of the visual field can be a useful tool for eye care practitioners.

BACKGROUND

Studies on letter perception have shown that glaucoma exacerbates difficulties to detect a target within flankers (crowding) in parafoveal vision. A target can be missed because it is not seen or because attention was not focused at that location. This prospective study evaluates the contribution of spatial pre-cueing on target detection.

METHOD

Fifteen patients and 15 age-matched controls were presented with letters displayed for 200 ms. Participants were asked to identify the orientation of the target letter T in two conditions: an isolated letter (uncrowded condition) and a letter with two flankers (crowded condition). The spacing between target and flankers was manipulated. The stimuli were randomly displayed at the fovea and at the parafovea at 5° left or right of fixation. A spatial cue preceded the stimuli in 50% of the trials. When present, the cue always signalled the correct location of the target.

RESULTS

Pre-cueing the spatial location of the target significantly improved performance for both foveal and parafoveal presentations in patients but not in controls who were at ceiling level. Unlike controls, patients exhibited an effect of crowding at the fovea with a higher accuracy for the isolated target than for the target flanked by two letters with no spacing between the elements.

CONCLUSION

Higher susceptibility to central crowding supports data showing abnormal foveal vision in glaucoma. Exogenous orienting of attention facilitates perception in parts of the visual field with reduced sensitivity.

Effect of low luminance on face recognition in adults with central and peripheral vision loss

PURPOSE

To investigate the effect of low luminance on face recognition, specifically facial identity discrimination (FID) and facial expression recognition (FER), in adults with central vision loss (CVL) and peripheral vision loss (PVL) and to explore the association between clinical vision measures and low luminance FID and FER.

METHODS

Participants included 33 adults with CVL, 17 with PVL and 20 controls. FID and FER were assessed under photopic and low luminance conditions. For the FID task, 12 sets of three faces with neutral expressions were presented and participants asked to indicate the odd-face-out. For FER, 12 single faces were presented and participants asked to name the expression (neutral, happy or angry). Photopic and low luminance visual acuity (VA) and contrast sensitivity (CS) were recorded for all participants and for the PVL group, Humphrey Field Analyzer (HFA) 24-2 mean deviation (MD).

RESULTS

FID accuracy in CVL, and to a lesser extent PVL, was reduced under low compared with photopic luminance (mean reduction 20% and 8% respectively; p < 0.001). FER accuracy was reduced only in CVL (mean reduction 25%; p < 0.001). For both CVL and PVL, low luminance and photopic VA and CS were moderately to strongly correlated with low luminance FID (ρ = 0.61-0.77, p < 0.05). For PVL, better eye HFA 24-2 MD was moderately correlated with low luminance FID (ρ = 0.54, p = 0.02). Results were similar for low luminance FER. Together, photopic VA and CS explained 75% of the variance in low luminance FID, and photopic VA explained 61% of the variance in low luminance FER. Low luminance vision measures explained little additional variance.

CONCLUSION

Low luminance significantly reduced face recognition, particularly for adults with CVL. Worse VA and CS were associated with reduced face recognition. Clinically, photopic VA is a good predictor of face recognition under low luminance conditions.

Data on eye movements of glaucoma patients with asymmetrical visual field loss during free viewing

This paper describes data from Asfaw at al. [1], which examined the eye movements of glaucoma patients (n=15) with pronounced asymmetrical vision loss (visual field loss worse in one eye). This allows for within-subject comparisons between the better and worse eye, thereby controlling for the effects of individual differences between patients. All patients had a clinical diagnosis of open angle glaucoma (OAG). Participants were asked to look at images of nature monocularly (free viewing; fellow eye patched) while gaze was recorded at 1000 Hz using a remote eye tracker (EyeLink 1000). Raw and processed eye tracking data are provided. In addition, clinical (visual acuity, contrast sensitivity and visual field) and demographic information (age, sex) are provided.

Impact of glaucoma on the spatial frequency processing of scenes in central vision

Glaucoma is an eye disease characterized by a progressive vision loss usually starting in peripheral vision. However, a deficit for scene categorization is observed even in the preserved central vision of patients with glaucoma. We assessed the processing and integration of spatial frequencies in the central vision of patients with glaucoma during scene categorization, considering the severity of the disease, in comparison to age-matched controls. In the first session, participants had to categorize scenes filtered in low-spatial frequencies (LSFs) and high-spatial frequencies (HSFs) as a natural or an artificial scene. Results showed that the processing of spatial frequencies was impaired only for patients with severe glaucoma, in particular for HFS scenes. In the light of proactive models of visual perception, we investigated how LSF could guide the processing of HSF in a second session. We presented hybrid scenes (combining LSF and HSF from two scenes belonging to the same or different semantic category). Participants had to categorize the scene filtered in HSF while ignoring the scene filtered in LSF. Surprisingly, results showed that the semantic influence of LSF on HSF was greater for patients with early glaucoma than controls, and then disappeared for the severe cases. This study shows that a progressive destruction of retinal ganglion cells affects the spatial frequency processing in central vision. This deficit may, however, be compensated by increased reliance on predictive mechanisms at early stages of the disease which would however decline in more severe cases.

Eye Movement Abnormalities in Glaucoma Patients: A Review

Glaucoma is a common condition that relies on careful clinical assessment to diagnose and determine disease progression. There is growing evidence that glaucoma is associated not only with loss of retinal ganglion cells but also with degeneration of cortical and subcortical brain structures associated with vision and eye movements. The effect of glaucoma pathophysiology on eye movements is not well understood. In this review, we examine the evidence surrounding altered eye movements in glaucoma patients compared to healthy controls, with a focus on quantitative eye tracking studies measuring saccades, fixation, and optokinetic nystagmus in a range of visual tasks. The evidence suggests that glaucoma patients have alterations in several eye movement domains. Patients exhibit longer saccade latencies, which worsen with increasing glaucoma severity. Other saccadic abnormalities include lower saccade amplitude and velocity, and difficulty inhibiting reflexive saccades. Fixation is pathologically altered in glaucoma with reduced stability. Optokinetic nystagmus measures have also been shown to be abnormal. Complex visual tasks (eg reading, driving, and navigating obstacles), integrate these eye movements and result in behavioral adaptations. The review concludes with a summary of the evidence and recommendations for future research in this emerging field.

The impact of simulated hemianopia on visual search for faces, words, and cars

Tests of visual search can index the effects of perceptual load and compare the processing efficiency for different object types, particularly when one examines the set-size effect, the increase in search time for each additional stimulus in an array. Previous studies have shown that the set-size effect is increased by manoeuvres that impede object processing, and in patients with object processing impairments. In this study, we examine how the low-level visual impairment of hemianopia affects visual search for complex objects, using a virtual paradigm. Forty-two healthy subjects performed visual search for faces, words, or cars with full-viewing as well as gaze-contingent simulations of complete left or right hemianopia. Simulated hemianopia lowered accuracy and discriminative power and increased response times and set-size effects, similarly for faces, words and cars. A comparison of set-size effects between target absent and target present trials did not show a difference between full-view and simulated hemianopic conditions, and a model of decision-making suggested that simulated hemianopia reduced the rate of accumulation of perceptual data, but did not change decision thresholds. We conclude that simulated hemianopia reduces the efficiency of visual search for complex objects, and that such impairment should be considered when interpreting results from high-level object processing deficits.

Vision impairment: To register or not to register? That is the question

For patients to enjoy the benefits of vision impairment registration, they need to be certified by an ophthalmologist. There have been concerns about barriers and a lack of awareness of benefits and certification criteria among ophthalmologists leading to under-registration. The purpose of this study was to gain insight into the certification process in terms of potential barriers, clinical decision-making, and understanding of current guidelines and registration benefits.

Ophthalmologists completed a survey on understanding registration benefits and barriers for certification ( n = 22) and a survey on clinical decision-making in certification ( n = 21). Furthermore, visual function and registration data were collected at a hospital Low Vision Clinic in Edinburgh from all new referrals ( n = 89) over a 4-month period from August to November 2020. Our study showed that the main barriers for vision impairment certification were insufficient awareness of registration benefits, uncertainty of when to certify, and a lack of time in clinic. Ophthalmologists were more confident about certification of ocular versus neurological visual impairment. In terms of clinical decision-making, the ophthalmologists’ survey placed most importance on visual-field assessments, followed by visual acuity. Very little importance was placed on contrast sensitivity. Our findings suggest that ophthalmologists would benefit from more education into the benefits of registration and more guidance when registering patients with neurological conditions affecting functional vision in particular. It may be beneficial to highlight the role of contrast sensitivity during the certification process to ophthalmologists.

Binocularly Asymmetric Crowding in Glaucoma and a Lack of Binocular Summation in Crowding

Purpose

Glaucoma is associated with progressive loss of retinal ganglion cells. Here we investigated the impact of glaucomatous damage on monocular and binocular crowding in parafoveal vision. We also examined the binocular summation of crowding to see if crowding is alleviated under binocular viewing.

Methods

The study design included 40 individuals with glaucoma and 24 age-similar normal cohorts. For each subject, the magnitude of crowding was determined by the extent of crowding zone. Crowding zone measurements were made binocularly in parafoveal vision (i.e., at 2° and 4° retinal eccentricities) visual field. For a subgroup of glaucoma subjects (n = 17), crowding zone was also measured monocularly for each eye.

Results

Our results showed that, compared with normal cohorts, individuals with glaucoma exhibited significantly larger crowding—enlargement of crowding zone (an increase by 21%; P < 0.01). Moreover, we also observed a lack of binocular summation (i.e., a binocular ratio of 1): binocular crowding was determined by the better eye. Hence, our results did not provide evidence supporting binocular summation of crowding in glaucomatous vision.

Conclusions

Our findings show that crowding is exacerbated in parafoveal vision in glaucoma and binocularly asymmetric glaucoma seems to induce binocularly asymmetric crowding. Furthermore, the lack of binocular summation for crowding observed in glaucomatous vision combined with the lack of binocular summation reported in a previous study on normal healthy vision support the view that crowding may start in the early stages of visual processing, at least before the process of binocular integration takes place.

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

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.

Sensitivity to Central Crowding for Faces in Patients With Glaucoma

PRECIS

Some patients with glaucoma report difficulties to recognize faces when they are far away. We show that this deficit could result from a higher sensitivity to crowding in central vision.

PURPOSE

The aim of the study is to investigate whether face recognition difficulties reported by some patients with glaucoma result from a greater sensitivity to inner crowding in central vision.

METHODS

Seventeen patients with glaucoma and 17 age-matched normally sighted controls participated in the study. An isolated mouth (uncrowded condition) or a mouth within a face (crowded condition) was randomly displayed centrally for 200 ms. For each condition, participants were asked to decide whether the mouth was closed or open. The stimuli were presented at 3 angular sizes (0.6×0.4, 1×0.72, and 1.5×1.08 degrees). Accuracy was measured.

RESULTS

Crowding affected performance differentially for patients and controls. Consistent with previous studies controls exhibited a "face superiority effect," with a better accuracy when the mouth was located within the face than when it was isolated. Sensitivity to crowding, reflected in a better accuracy with the isolated mouth, was observed in 10 of 17 patients only for small images. Crowding disappeared for larger faces, as the facial features were spaced out. Five patients were not sensitive to crowding. Importantly, no difference was found between the 2 subgroups of patients (sensitive vs. nonsensitive) in terms of mean deviation, contrast sensitivity, acuity, thickness of the retinal nerve fiber layer, or macular ganglion cell-inner plexiform layer.

CONCLUSIONS

An excessive sensitivity to central crowding might explain the difficulties in face perception and reading reported by some patients with glaucoma. The sensory or cognitive processes underlying this excessive sensitivity must be elucidated to improve central perception in glaucoma.

Eye-Movement-Based Assessment of the Perceptual Consequences of Glaucomatous and Neuro-Ophthalmological Visual Field Defects

Purpose

Assessing the presence of visual field defects (VFD) through procedures such as perimetry is an essential aspect of the management and diagnosis of ocular disorders. However, even the latest perimetric methods have shortcomings-a high cognitive demand and requiring prolonged stable fixation and feedback through a button response. Consequently, an approach using eye movements (EM)-as a natural response-has been proposed as an alternate way to evaluate the presence of VFD. This approach has given good results for computer-simulated VFD. However, its use in patients is not well documented yet. Here we use this new approach to quantify the spatiotemporal properties (STP) of EM of various patients suffering from glaucoma and neuro-ophthalmological VFD and controls.

Methods

In total, 15 glaucoma patients, 37 patients with a neuro-ophthalmological disorder, and 21 controls performed a visual tracking task while their EM were being recorded. Subsequently, the STP of EM were quantified using a cross-correlogram analysis. Decision trees were used to identify the relevant STP and classify the populations.

Results

We achieved a classification accuracy of 94.5% (TPR/sensitivity = 96%, TNR/specificity = 90%) between patients and controls. Individually, the algorithm achieved an accuracy of 86.3% (TPR for neuro-ophthalmology [97%], glaucoma [60%], and controls [86%]). The STP of EM were highly similar across two different control cohorts.

Conclusions

In an ocular tracking task, patients with VFD due to different underlying pathology make EM with distinctive STP. These properties are interpretable based on different clinical characteristics of patients and can be used for patient classification.

Translational Relevance

Our EM-based screening tool may complement existing perimetric techniques in clinical practice.

Higher contrast thresholds for vanishing optotype recognition in macular visual fields among glaucoma patients: a structure-function analysis

BACKGROUND/AIMS

We aimed to explore the impact of glaucomatous macular damage, specifically retinal ganglion cell (RGC) loss, on macular pattern vision measured by the vanishing optotype (VO) recognition contrast threshold.

METHODS

Seventy-two patients (mean age, 33.51±7.05 years) with primary open-angle glaucoma and 36 healthy controls (mean age, 30.25±6.70 years) were enrolled. VO recognition contrast thresholds of each participant were measured at the 16 preset test locations covering the central 5° visual field (VF). Macular sensitivity (MS) was tested by macular threshold test of Humphrey Field Analyzer. Macular RGC plus inner plexiform layer (GCIPL) thickness was also measured by spectral domain optical coherence tomography.

RESULTS

The VO contrast threshold demonstrated weak-to-moderate correlations (rho=-0.275 to -0.653) with MS (p<0.001). There was a significantly higher VO contrast threshold in glaucoma group (p<0.0001). At similar levels of MS, patients with glaucoma with GCIPL damage showed remarkably higher VO contrast thresholds than those with preserved GCIPL (p=0.0079). The structure-function relationships between VO contrast threshold and GCIPL thickness (rho=-0.725 to -0.802) were remarkably stronger than those between MS and GCIPL thickness (rho=0.210 to 0.448). VO contrast threshold showed stronger correlation with average GCIPL thickness (rho=-0.362 to -0.778) than MS (rho=0.238 to 0.398) at multiple test locations in glaucoma group.

CONCLUSIONS

Glaucomatous eyes have higher contrast thresholds for VO recognition in fovea-around VF. Stronger structure-function relationships indicate that VO contrast threshold is more vulnerable to RGC damage.

A Saccadic Choice Task for Target Face Detection at Large Visual Eccentricities in Patients with Glaucoma

SIGNIFICANCE

Little is known about the perception of glaucomatous patients at large visual eccentricities. We show that the patients' performance drops beyond 40° eccentricity even for large images of scenes, suggesting that clinical tests should assess the patients' vision at larger eccentricities than 24 or 30°.

PURPOSE

Daily activities such as visual search, spatial navigation, and hazard detection require rapid scene recognition on a wide field of view. We examined whether participants with visual field loss at standard automated perimetry 30-2 were able to detect target faces at large visual eccentricities.

METHODS

Twelve patients with glaucoma and 14 control subjects were asked to detect a face in a two-alternative saccadic forced choice task. Pairs of scenes, one containing a face, were randomly displayed at 10, 20, 40, 60, or 80° eccentricity on a panoramic screen covering 180° horizontally. Participants were asked to detect and to saccade toward the scene containing a face.

RESULTS

Saccade latencies were significantly slower in patients (264 milliseconds; confidence interval [CI], 222 to 306 milliseconds) than in control subjects (207 milliseconds; CI, 190 to 226 milliseconds), and accuracy was significantly lower in patients (70% CI, 65 to 85%) than in control subjects (75.7% CI, 71.5 to 79.5%). Although still significantly above chance at 60°, the patients' performance dropped beyond 40° eccentricity. The control subjects' performance was still above chance at 80° eccentricity.

CONCLUSIONS

In patients with various degrees of peripheral visual field defect, performance dropped beyond 40° eccentricity for large images at a high contrast. This result could reflect reduced spread of exploration in glaucoma.

Revisiting the Drasdo Model: Implications for Structure-Function Analysis of the Macular Region

Purpose

To provide a consistent implementation of a retinal ganglion cell (RGC) displacement model proposed by Drasdo et al. for macular structure-function analysis, customizable by axial length (AL).

Methods

The effect of axial length on the shape of the inner retina was measured on 235 optical coherence tomography (OCT) scans from healthy eyes, to provide evidence for geometric scaling of structures with eye size. Following this assumption, we applied the Drasdo model to map perimetric stimuli on the radially displaced RGCs using two different methods: Method 1 only displaced the center of the stimuli; Method 2 applied the displacement to every point on the edge of the stimuli. We compared the accuracy of the two methods by calculating, for each stimulus, the number of expected RGC receptive fields and the number RGCs calculated from the histology map, expected to be equivalent. The same calculation was repeated on RGC density maps derived from 28 OCT scans from 28 young healthy subjects (age < 40 years) to confirm our results on clinically available measurements.

Results

The size of the retinal structures significantly increased with AL (P < 0.001) and was well predicted by geometric scaling. Method 1 systematically underestimated the RGC counts by as much as 60%. No bias was observed with Method 2.

Conclusions

The Drasdo model can effectively account for AL assuming geometric scaling. Method 2 should be used for structure-function analyses.

Translational Relevance

We developed a free web App in Shiny R to make our results available for researchers.

Increased Equivalent Input Noise in Glaucomatous Central Vision: Is it Due to Undersampling of Retinal Ganglion Cells?

Purpose

Recent evidence shows that macular damage is common even in early stages of glaucoma. Here we investigated whether contrast sensitivity loss in the central vision of glaucoma patients is due to an increase in equivalent input noise (Neq), a decrease in calculation efficiency, or both. We also examined how retinal undersampling resulting from loss of retinal ganglion cells (RGCs) may affect Neq and calculation efficiency.

Methods

This study included 21 glaucoma patients and 23 age-matched normally sighted individuals. Threshold contrast for orientation discrimination was measured with a sinewave grating embedded in varying levels of external noise. Data were fitted to the linear amplifier model (LAM) to factor contrast sensitivity into Neq and calculation efficiency. We also correlated macular RGC counts estimated from structural (spectral-domain optical coherence tomography) and functional (standard automated perimetry Swedish interactive thresholding algorithm 10-2) data with either Neq or efficiency. Furthermore, using analytical and computer simulation approach, the relative effect of retinal undersampling on Neq and efficiency was evaluated by adding the RGC sampling module into the LAM.

Results

Compared with normal controls, glaucoma patients exhibited a significantly larger Neq without significant difference in efficiency. Neq was significantly correlated with Pelli-Robson contrast sensitivity and macular RGC counts. The results from analytical derivation and model simulation further demonstrated that Neq can be expressed as a function of internal noise and retinal sampling.

Conclusions

Our results showed that equivalent input noise is significantly elevated in glaucomatous vision, thereby impairing foveal contrast sensitivity. Our findings further elucidated how undersampling at the retinal level may increase equivalent input noise.

Speed and accuracy of saccades in patients with glaucoma evaluated using an eye tracking perimeter

Background

To examine the speed and accuracy of saccadic eye movements during a novel eye tracking threshold visual field assessment and determine whether eye movement parameters may improve ability to detect glaucoma.

Methods

A prospective study including both eyes of 31 patients with glaucoma and 23 controls. Standard automated perimetry (SAP) and eye tracking perimetry (saccadic vector optokinetic perimetry, SVOP) was performed. SVOP provided data on threshold sensitivity, saccade latency, and two measures of accuracy of saccades (direction bias and amplitude bias). The relationship between eye movement parameters and severity of glaucoma was examined and Receiver Operating Characteristic curves were used to assess ability to detect glaucoma.

Results

Patients with glaucoma had significantly slower saccades (602.9 ± 50.0 ms versus 578.3 ± 44.6 ms for controls, P = 0.009) and reduced saccade accuracy (direction bias = 7.4 ± 1.8 versus 6.5 ± 1.5 degrees, P = 0.006). There was a significant slowing of saccades and saccades became less accurate with worsening SAP sensitivity. Slower saccades were associated with increased odds of glaucoma; however, the AUC for saccade latency was only 0.635 compared to 0.914 for SVOP sensitivity.

Conclusion

Patients with glaucoma had significant differences in eye movements compared to healthy subjects, with a relationship between slower and less accurate eye movements and worse glaucoma severity. However, in a multivariable model, eye movement parameters were not of additional benefit in differentiating eyes with glaucoma from healthy controls.

Evaluation of eye movements and visual performance in patients with cataract

Eye movement is an essential component of visual perception. Eye movement disorders have been observed in many eye disease, and are thought to affect various visual performance in daily life. However, eye movement behaviors of the elderly with cataract are poorly understood, and the impact of cataract surgery on eye movements has not been investigated. In this study, we observed the eye movement behaviors in thirty patients with bilateral age-related cataract while performing three performance-based tasks (visual search, face recognition and reading). Eye movements were automatically recorded by an eye tracker during task performance. We found an overall improved visual performance postoperatively, presented as elevated percentage of correctly identified objects and faces, reduced search time and increased reading speed. Eye movement parameters were found significantly altered after cataract surgery. Fixation count, total fixation duration and total visit duration were markedly increased in the visual search task and face recognition task. The proportion of regressive saccades was obviously decreased in the reading task. These eye movement parameters were found to be correlated with the measures of visual performance. Our findings suggested a potential association between the eye movement disturbance and impaired visual performance, and provided a new insight on the potential usefulness of eye movement as an objective and valid tool to understand visual impairments caused by cataract, as well as evaluate practical outcomes of cataract surgery.

Eye Movements of Drivers with Glaucoma on a Visual Recognition Slide Test

SIGNIFICANCE

Glaucoma has been shown to impair hazard detection ability and increase crash risk compared to controls. Differences in visual search behavior of the driving scene may explain these differences; however, there has been limited investigation of this issue with inconsistent findings.

PURPOSE

Through eye movement tracking of older drivers with glaucoma, we explored their visual search behavior in comparison with controls while performing the DriveSafe, a slide recognition test purported to predict fitness to drive.

METHODS

Thirty-one drivers with glaucoma (mean age, 71.7 ± 6.3 years; average better-eye mean defect,-3 dB; average worse-eye mean defect,-12 dB) and 25 age-matched controls underwent measurements of their visual acuity, contrast sensitivity, visual fields, and useful field of view (visual processing speeds). Participants' eye movements were recorded while they completed the DriveSafe test, which consists of brief presentations of static, real-world driving scenes containing various road users (pedestrians, bicycles, vehicles). Participants reported the types, positions, and direction of travel of road users in each image; the score was the total number of correctly reported items (maximum, 128).

RESULTS

Drivers with glaucoma had significantly worse DriveSafe scores (P = .03), fixated on road users for shorter durations (P < .001), and exhibited smaller saccades (P = .02) compared with controls. For all participants, longer fixation times on road users (P < .001) was the eye movement measure most strongly associated with better DriveSafe scores; this relationship was not significantly different between groups. Useful field-of-view divided attention was the strongest visual predictor of DriveSafe scores.

CONCLUSIONS

Eye movement changes in the glaucoma group may reflect increased difficulty in identifying relevant objects in the visual scene, which may be related to their lower DriveSafe scores. Given the DriveSafe's potential utility in assessing drivers with visual impairment before on-road testing, further investigations on how DriveSafe performance and eye movement patterns compare to those during on-road driving are warranted.

Refinement and preliminary evaluation of two tablet-based tests of real-world visual function

Purpose

To describe, refine, evaluate, and provide normative control data for two freely available tablet‐based tests of real‐world visual function, using a cohort of young, normally‐sighted adults.

Methods

Fifty young (18–40 years), normally‐sighted adults completed tablet‐based assessments of (1) face discrimination and (2) visual search. Each test was performed twice, to assess test‐retest repeatability. Post‐hoc analyses were performed to determine the number of trials required to obtain stable estimates of performance. Distributions were fitted to the normative data to determine the 99% population‐boundary for normally sighted observers. Participants were also asked to rate their comprehension of each test.

Results

Both tests provided stable estimates in around 20 trials (~1–4 min), with only a further reduction of 14%–17% in the 95% Coefficient of Repeatability (CoR₉₅) when an additional 40 trials were included. When using only ~20 trials: median durations for the first run of each test were 191 s (Faces) and 51 s (Search); test‐retest CoR₉₅ were 0.27 d (Faces) and 0.84 s (Search); and normative 99% population‐limits were 3.50 d (Faces) and 3.1 s (Search). No participants exhibited any difficulties completing either test (100% completion rate), and ratings of task‐understanding were high (Faces: 9.6 out of 10; Search: 9.7 out of 10).

Conclusions

This preliminary assessment indicated that both tablet‐based tests are able to provide simple, quick, and easy‐to‐administer measures of real‐world visual function in normally‐sighted young adults. Further work is required to assess their accuracy and utility in older people and individuals with visual impairment. Potential applications are discussed, including their use in clinic waiting rooms, and as an objective complement to Patient Reported Outcome Measures (PROMs).

Measuring Disability in Glaucoma

BACKGROUND

Glaucomatous visual field loss can have far-reaching and debilitating consequences on an individual, affecting one's ability to perform many important tasks. Although assessment of glaucoma-related disability constitutes an important part of clinical care, there remains a lack of organized, detailed information on the most suitable methods to capture disability in glaucoma.

PURPOSE

This review details the available methods to measure glaucoma-related disability and highlights important findings from studies utilizing these various methods.

METHODS

The literature was reviewed to identify papers evaluating disability in glaucoma and findings were summarized by research methodology used and area of impairment.

RESULTS

Identified methods for capturing glaucoma-related disability included qualitative descriptions, glaucoma-specific quality of life questionnaires, vision-specific questionnaires, general health questionnaires, functional domain-specific questionnaires, evaluation of task performance, event assessment (ie, falls and motor vehicle accidents), and real-world behavior (ie, daily physical activity). Findings using these methods show a strong relationship between glaucoma and/or glaucoma severity and difficulties with reading, driving, mobility, and other tasks such as prehension and facial recognition. In addition, glaucoma has financial and psychological implications on the patient, and can affect caregivers in some cases as well.

CONCLUSIONS

A wide variety of research tools have been used to characterize the disability resulting from glaucoma. Together, these tools show that glaucoma affects many abilities which are important for independent living. Strengths and limitations of the various research techniques are discussed so that future studies may use the method(s) most suitable for answering the research question posed.

Scanning Behavior and Daytime Driving Performance of Older Adults With Glaucoma

PURPOSE

The purpose of this study was to assess the link between visual scanning behavior and closed-road driving performance in older drivers with glaucomatous visual impairment.

MATERIALS AND METHODS

Participants included 13 older drivers with glaucoma [mean age=71.6±7.1 y; average better-eye mean deviation (MD)=-2.9±2.1 dB, average worse-eye MD=-12.5±7.1 dB] and 10 visually normal controls (mean age=70.6±7.4 y). Visual acuity, contrast sensitivity, visual fields, useful field of view, and motion sensitivity were assessed. Participants drove around a closed-road circuit while their eye movements were recorded with an ASL Mobile Eye-XG, and head movements recorded using the gyroscope sensors of a smart phone. Measures of driving performance included hazards hit, sign recognition, and lane-crossing time; an overall driving score was derived from these component measures.

RESULTS

Participants with glaucoma had significantly poorer overall driving scores (P=0.026) and hit more hazards (P=0.043) than controls. The glaucoma group also exhibited larger saccades (P<0.001) and horizontal (P<0.001) and vertical search variances (P=0.002) than controls. Larger saccades were associated with better driving scores in the glaucoma group (P=0.001), but not the controls (P=0.75). Head movements did not differ between groups. For all participants, better-eye MD was the strongest visual predictor of overall driving score (P<0.001), followed by the other measures of visual fields, motion sensitivity, contrast sensitivity, and useful field of view (P<0.05).

CONCLUSIONS

Older drivers with glaucoma had poorer driving performance than controls and demonstrated differences in eye movement patterns. The association between larger saccades and better driving scores in those with glaucoma suggests that altering scanning behavior may benefit driving performance and safety in this group.

Does Glaucoma Alter Eye Movements When Viewing Images of Natural Scenes? A Between-Eye Study

Purpose

To investigate whether glaucoma produces measurable changes in eye movements.

Methods

Fifteen glaucoma patients with asymmetric vision loss (difference in mean deviation [MD] > 6 dB between eyes) were asked to monocularly view 120 images of natural scenes, presented sequentially on a computer monitor. Each image was viewed twice-once each with the better and worse eye. Patients' eye movements were recorded with an Eyelink 1000 eye-tracker. Eye-movement parameters were computed and compared within participants (better eye versus worse eye). These parameters included a novel measure: saccadic reversal rate (SRR), as well as more traditional metrics such as saccade amplitude, fixation counts, fixation duration, and spread of fixation locations (bivariate contour ellipse area [BCEA]). In addition, the associations of these parameters with clinical measures of vision were investigated.

Results

In the worse eye, saccade amplitude\(\def\upalpha{\unicode[Times]{x3B1}}\)\(\def\upbeta{\unicode[Times]{x3B2}}\)\(\def\upgamma{\unicode[Times]{x3B3}}\)\(\def\updelta{\unicode[Times]{x3B4}}\)\(\def\upvarepsilon{\unicode[Times]{x3B5}}\)\(\def\upzeta{\unicode[Times]{x3B6}}\)\(\def\upeta{\unicode[Times]{x3B7}}\)\(\def\uptheta{\unicode[Times]{x3B8}}\)\(\def\upiota{\unicode[Times]{x3B9}}\)\(\def\upkappa{\unicode[Times]{x3BA}}\)\(\def\uplambda{\unicode[Times]{x3BB}}\)\(\def\upmu{\unicode[Times]{x3BC}}\)\(\def\upnu{\unicode[Times]{x3BD}}\)\(\def\upxi{\unicode[Times]{x3BE}}\)\(\def\upomicron{\unicode[Times]{x3BF}}\)\(\def\uppi{\unicode[Times]{x3C0}}\)\(\def\uprho{\unicode[Times]{x3C1}}\)\(\def\upsigma{\unicode[Times]{x3C3}}\)\(\def\uptau{\unicode[Times]{x3C4}}\)\(\def\upupsilon{\unicode[Times]{x3C5}}\)\(\def\upphi{\unicode[Times]{x3C6}}\)\(\def\upchi{\unicode[Times]{x3C7}}\)\(\def\uppsy{\unicode[Times]{x3C8}}\)\(\def\upomega{\unicode[Times]{x3C9}}\)\(\def\bialpha{\boldsymbol{\alpha}}\)\(\def\bibeta{\boldsymbol{\beta}}\)\(\def\bigamma{\boldsymbol{\gamma}}\)\(\def\bidelta{\boldsymbol{\delta}}\)\(\def\bivarepsilon{\boldsymbol{\varepsilon}}\)\(\def\bizeta{\boldsymbol{\zeta}}\)\(\def\bieta{\boldsymbol{\eta}}\)\(\def\bitheta{\boldsymbol{\theta}}\)\(\def\biiota{\boldsymbol{\iota}}\)\(\def\bikappa{\boldsymbol{\kappa}}\)\(\def\bilambda{\boldsymbol{\lambda}}\)\(\def\bimu{\boldsymbol{\mu}}\)\(\def\binu{\boldsymbol{\nu}}\)\(\def\bixi{\boldsymbol{\xi}}\)\(\def\biomicron{\boldsymbol{\micron}}\)\(\def\bipi{\boldsymbol{\pi}}\)\(\def\birho{\boldsymbol{\rho}}\)\(\def\bisigma{\boldsymbol{\sigma}}\)\(\def\bitau{\boldsymbol{\tau}}\)\(\def\biupsilon{\boldsymbol{\upsilon}}\)\(\def\biphi{\boldsymbol{\phi}}\)\(\def\bichi{\boldsymbol{\chi}}\)\(\def\bipsy{\boldsymbol{\psy}}\)\(\def\biomega{\boldsymbol{\omega}}\)\(\def\bupalpha{\unicode[Times]{x1D6C2}}\)\(\def\bupbeta{\unicode[Times]{x1D6C3}}\)\(\def\bupgamma{\unicode[Times]{x1D6C4}}\)\(\def\bupdelta{\unicode[Times]{x1D6C5}}\)\(\def\bupepsilon{\unicode[Times]{x1D6C6}}\)\(\def\bupvarepsilon{\unicode[Times]{x1D6DC}}\)\(\def\bupzeta{\unicode[Times]{x1D6C7}}\)\(\def\bupeta{\unicode[Times]{x1D6C8}}\)\(\def\buptheta{\unicode[Times]{x1D6C9}}\)\(\def\bupiota{\unicode[Times]{x1D6CA}}\)\(\def\bupkappa{\unicode[Times]{x1D6CB}}\)\(\def\buplambda{\unicode[Times]{x1D6CC}}\)\(\def\bupmu{\unicode[Times]{x1D6CD}}\)\(\def\bupnu{\unicode[Times]{x1D6CE}}\)\(\def\bupxi{\unicode[Times]{x1D6CF}}\)\(\def\bupomicron{\unicode[Times]{x1D6D0}}\)\(\def\buppi{\unicode[Times]{x1D6D1}}\)\(\def\buprho{\unicode[Times]{x1D6D2}}\)\(\def\bupsigma{\unicode[Times]{x1D6D4}}\)\(\def\buptau{\unicode[Times]{x1D6D5}}\)\(\def\bupupsilon{\unicode[Times]{x1D6D6}}\)\(\def\bupphi{\unicode[Times]{x1D6D7}}\)\(\def\bupchi{\unicode[Times]{x1D6D8}}\)\(\def\buppsy{\unicode[Times]{x1D6D9}}\)\(\def\bupomega{\unicode[Times]{x1D6DA}}\)\(\def\bupvartheta{\unicode[Times]{x1D6DD}}\)\(\def\bGamma{\bf{\Gamma}}\)\(\def\bDelta{\bf{\Delta}}\)\(\def\bTheta{\bf{\Theta}}\)\(\def\bLambda{\bf{\Lambda}}\)\(\def\bXi{\bf{\Xi}}\)\(\def\bPi{\bf{\Pi}}\)\(\def\bSigma{\bf{\Sigma}}\)\(\def\bUpsilon{\bf{\Upsilon}}\)\(\def\bPhi{\bf{\Phi}}\)\(\def\bPsi{\bf{\Psi}}\)\(\def\bOmega{\bf{\Omega}}\)\(\def\iGamma{\unicode[Times]{x1D6E4}}\)\(\def\iDelta{\unicode[Times]{x1D6E5}}\)\(\def\iTheta{\unicode[Times]{x1D6E9}}\)\(\def\iLambda{\unicode[Times]{x1D6EC}}\)\(\def\iXi{\unicode[Times]{x1D6EF}}\)\(\def\iPi{\unicode[Times]{x1D6F1}}\)\(\def\iSigma{\unicode[Times]{x1D6F4}}\)\(\def\iUpsilon{\unicode[Times]{x1D6F6}}\)\(\def\iPhi{\unicode[Times]{x1D6F7}}\)\(\def\iPsi{\unicode[Times]{x1D6F9}}\)\(\def\iOmega{\unicode[Times]{x1D6FA}}\)\(\def\biGamma{\unicode[Times]{x1D71E}}\)\(\def\biDelta{\unicode[Times]{x1D71F}}\)\(\def\biTheta{\unicode[Times]{x1D723}}\)\(\def\biLambda{\unicode[Times]{x1D726}}\)\(\def\biXi{\unicode[Times]{x1D729}}\)\(\def\biPi{\unicode[Times]{x1D72B}}\)\(\def\biSigma{\unicode[Times]{x1D72E}}\)\(\def\biUpsilon{\unicode[Times]{x1D730}}\)\(\def\biPhi{\unicode[Times]{x1D731}}\)\(\def\biPsi{\unicode[Times]{x1D733}}\)\(\def\biOmega{\unicode[Times]{x1D734}}\)\((P = 0.012; - 13\% \)) and BCEA \((P = 0.005; - 16\% )\) were smaller, while SRR was greater (\(P = 0.018; + 16\% \)). There was a significant correlation between the intereye difference in BCEA, and differences in MD values (\({\rm{Spearman^{\prime} s}}\ r = 0.65;P = 0.01\)), while differences in SRR were associated with differences in visual acuity (\({\rm{Spearman^{\prime} s}}\ r = 0.64;P = 0.01\)). Furthermore, between-eye differences in BCEA were a significant predictor of between-eye differences in MD: for every 1-dB difference in MD, BCEA reduced by 6.2% (95% confidence interval, 1.6%-10.3%).

Conclusions

Eye movements are altered by visual field loss, and these changes are related to changes in clinical measures. Eye movements recorded while passively viewing images could potentially be used as biomarkers for visual field damage.

Spatial correlation between localized decreases in exploratory visual search performance and areas of glaucomatous visual field loss

BACKGROUND

Visual search is a critical skill for several daily tasks and may be compromised in patients with impaired vision. The objective of this study was to study the relationships between exploratory visual search performance (EVSP) visual field (VF) sensitivity in patients with glaucoma.

METHODS

Primary open-angle glaucoma patients (POAG; n = 29) and healthy (Control; n = 28) individuals with best corrected visual acuity better than 0.2 logMAR underwent a comprehensive ophthalmological examination, including Humphrey VF tests (24-2 SITA-Standard), and a monocular exploratory visual search digit-based task performed using a software that quantifies the time spent to find a targert on a random array of digits distributed on nine sequential screens. The screens were divided into five areas to topographically match with five VF sectors.

RESULTS

As expected, POAG eyes had worse VF mean deviation (MD) sensitivity and EVSP than Controls (MD - 8.02 ± 7.88 dB vs - 1.43 ± 1.50 dB, p < 0.0001; and total EVSP time 106.42 ± 59.64 s vs 52.75 ± 19.07 s, p < 0.0001). MD sensitivity of both groups significantly correlated with total EVSP time (POAG r = - 0.45, p = 0.01; and Control r = 0.37, p = 0.049). A significant relationship was observed between EVSP (individual time) and both visual acuity (p = 0.006) and glaucoma diagnosis (p = 0.005). The mean sensitivity of the peripheral VF areas of the POAG group showed significant correlation with the individual search time in the corresponding spatial areas, except in the peripheral superior temporal area (r = - 0.35, p = 0.06).

CONCLUSION

These data indicate that POAG patients' EVSP is impaired in topographically-correspondent VF areas with sensitivity loss. Visual search may be considered as a measure of impairment of daily activities in glaucoma patients, if further similar tests using binocular conditions corroborate our findings.

Briefly Flashed Scenes Can Be Stored in Long-Term Memory

The capacity of human memory is impressive. Previous reports have shown that when asked to memorize images, participants can recognize several thousands of visual objects in great details even with a single viewing of a few seconds per image. In this experiment, we tested recognition performance for natural scenes that participants saw for 20 ms only once (untrained group) or 22 times over many days (trained group) in an unrelated task. 400 images (200 previously viewed and 200 novel images) were flashed one at a time and participants were asked to lift their finger from a pad whenever they thought they had already seen the image (go/no-go paradigm). Compared to previous reports of excellent recognition performance with only single presentations of a few seconds, untrained participants were able to recognize only 64% of the 200 images they had seen few minutes before. On the other hand, trained participants, who had processed the flashed images (20 ms) several times, could correctly recognize 89% of them. EEG recordings confirmed these behavioral results. As early as 230 ms after stimulus onset, a significant event-related-potential (ERP) difference between familiar and new images was observed for the trained but not for the untrained group. These results show that briefly flashed unmasked scenes can be incidentally stored in long-term memory when repeated.

Evidence for alterations in fixational eye movements in glaucoma

Background

Fixation changes in glaucoma are generally overlooked, as they are not strikingly evident as in macular diseases. Fundus perimetry might give additional insights into this aspect, along with traditional perimetric measures. In this work we propose a novel method to quantify glaucomatous changes in fixation features as detected by fundus perimetry and relate them to the extent of glaucomatous damage.

Methods

We retrospectively analysed fixation data from 320 people (200 normal subjects and 120 with glaucoma) from the Preferred Retinal Locus (PRL) detection of a Compass perimeter. Fixation stability was measured as Bivariate Contour Ellipse Area (BCEA), and using two novel metrics: (1) Mean Euclidean Distance (MED) from the Preferred Retinal Locus, and (2) Sequential Euclidean Distance (SED) of sequential fixation locations. These measures were designed to capture the spread of fixation points, and the frequency of position changes during fixation, respectively.

Results

In the age corrected analysis, SED was significantly greater in glaucomatous subjects than controls (P = 0.002), but there was no difference in BCEA (P = 0.15) or MED (P = 0.054). Similarly, SED showed a significant association with Mean Deviation (P <  0.001), but neither BCEA nor MED were significantly correlated (P > 0.14 for both).

Conclusion

Changes in the scanning pattern detected by SED are better than traditional measures of fixation spread (BCEA) for describing the changes in fixation stability observed in glaucoma.

Data on eye movements in people with glaucoma and peers with normal vision

Eye movements of glaucoma patients have been shown to differ from age-similar control groups when performing everyday tasks, such as reading (Burton et al., 2012; Smith et al., 2014) [1], [2], visual search (Smith et al., 2012) [3], face recognition (Glen et al., 2013) [4], driving, and viewing static images (Smith et al., 2012) [5]. Described here is the dataset from a recent publication in which we compared the eye-movements of 44 glaucoma patients and 32 age-similar controls, while they watched a series of short video clips taken from television programs (Crabb et al., 2018) [6]. Gaze was recorded at 1000 Hz using a remote eye-tracker. We also provide demographic information and results from a clinical examination of vision for each participant.

The effect of non-neovascular age-related macular degeneration on face recognition performance

Purpose

There is a well-established research base surrounding face recognition in patients with age-related macular degeneration (AMD). However, much of this existing research does not differentiate between results obtained for ‘wet’ AMD and ‘dry’ AMD. Here, we test the hypothesis that face recognition performance is worse in patients with dry AMD compared with visually healthy peers.

Methods

Patients (>60 years of age, logMAR binocular visual acuity 0.7 or better) with dry AMD of varying severity and visually healthy age-related peers (controls) completed a modified version of the Cambridge Face Memory Test (CFMT). Percentage of correctly identified faces was used as an outcome measure for performance for each participant. A 90% normative reference limit was generated from the distribution of CFMT scores recorded in the visually healthy controls. Scores for AMD participants were then specifically compared to this limit, and comparisons between average scores in the AMD severity groups were investigated.

Results

Thirty patients (median [interquartile range] age of 76 [70, 79] years) and 34 controls (median age of 70 [64, 75] years) were examined. Four, seventeen and nine patients were classified as having early, intermediate and late AMD (geographic atrophy) respectively. Five (17%) patients recorded a face recognition performance worse than the 90% limit (Fisher’s exact test, p = 0.46) set by controls; four of these had geographic atrophy. Patients with geographic atrophy identified fewer faces on average (±SD) (61% ± 22%) than those with early and intermediate AMD (75 ± 11%) and controls (74% ± 11%).

Conclusions

People with dry AMD may not suffer from problems with face recognition until the disease is in its later stages; those with late AMD (geographic atrophy) are likely to have difficulty recognising faces. The results from this study should influence the management and expectations of patients with dry AMD in both community practice and hospital clinics.

Scene and human face recognition in the central vision of patients with glaucoma

Primary open-angle glaucoma (POAG) firstly mainly affects peripheral vision. Current behavioral studies support the idea that visual defects of patients with POAG extend into parts of the central visual field classified as normal by static automated perimetry analysis. This is particularly true for visual tasks involving processes of a higher level than mere detection. The purpose of this study was to assess visual abilities of POAG patients in central vision. Patients were assigned to two groups following a visual field examination (Humphrey 24–2 SITA-Standard test). Patients with both peripheral and central defects and patients with peripheral but no central defect, as well as age-matched controls, participated in the experiment. All participants had to perform two visual tasks where low-contrast stimuli were presented in the central 6° of the visual field. A categorization task of scene images and human face images assessed high-level visual recognition abilities. In contrast, a detection task using the same stimuli assessed low-level visual function. The difference in performance between detection and categorization revealed the cost of high-level visual processing. Compared to controls, patients with a central visual defect showed a deficit in both detection and categorization of all low-contrast images. This is consistent with the abnormal retinal sensitivity as assessed by perimetry. However, the deficit was greater for categorization than detection. Patients without a central defect showed similar performances to the controls concerning the detection and categorization of faces. However, while the detection of scene images was well-maintained, these patients showed a deficit in their categorization. This suggests that the simple loss of peripheral vision could be detrimental to scene recognition, even when the information is displayed in central vision. This study revealed subtle defects in the central visual field of POAG patients that cannot be predicted by static automated perimetry assessment using Humphrey 24–2 SITA-Standard test.

Higher Contrast Requirement for Letter Recognition and Macular RGC+ Layer Thinning in Glaucoma Patients and Older Adults

Purpose

Growing evidence suggests the involvement of the macula even in early stages of glaucoma. However, little is known about the impact of glaucomatous macular damage on central pattern vision. Here we examine the contrast requirement for letter recognition and its relationship with retinal thickness in the macular region.

Methods

A total of 40 participants were recruited: 13 patients with glaucoma (mean age = 65.6 ± 6.6 years), 14 age-similar normally sighted adults (59.1 ± 9.1 years), and 13 young normally sighted adults (21.0 ± 2.0 years). For each participant, letter-recognition contrast thresholds were obtained using a letter recognition task in which participants identified English letters presented at varying retinal locations across the central 12° visual field, including the fovea. The macular retinal ganglion cell plus inner plexiform (RGC+) layer thickness was also evaluated using spectral-domain optical coherence tomography (SD-OCT).

Results

Compared to age-similar normal controls, glaucoma patients exhibited a significant increase in letter-recognition contrast thresholds (by 236%, P < 0.001) and a significant decrease in RGC+ layer thickness (by 17%, P < 0.001) even after controlling for age, pupil diameter, and visual acuity. Compared to normal young adults, older adults showed a significant increase in letter-recognition contrast thresholds and a significant decrease in RGC+ layer thickness. Across all subjects, the thickness of macular RGC+ layer was significantly correlated with letter-recognition contrast thresholds, even after correcting for pupil diameter and visual acuity (r = −0.65, P < 0.001).

Conclusions

Our results show that both glaucoma and normal aging likely bring about a thinning of the macular RGC+ layer; the macular RGC+ layer thickness appears to be associated with the contrast requirements for letter recognition in central vision.

Impact of Glaucoma and Dry Eye on Text-Based Searching

PURPOSE

We determine if visual field loss from glaucoma and/or measures of dry eye severity are associated with difficulty searching, as judged by slower search times on a text-based search task.

METHODS

Glaucoma patients with bilateral visual field (VF) loss, patients with clinically significant dry eye, and normally-sighted controls were enrolled from the Wilmer Eye Institute clinics. Subjects searched three Yellow Pages excerpts for a specific phone number, and search time was recorded.

RESULTS

A total of 50 glaucoma subjects, 40 dry eye subjects, and 45 controls completed study procedures. On average, glaucoma patients exhibited 57% longer search times compared to controls (95% confidence interval [CI], 26%-96%, P < 0.001), and longer search times were noted among subjects with greater VF loss (P < 0.001), worse contrast sensitivity (P < 0.001), and worse visual acuity (P = 0.026). Dry eye subjects demonstrated similar search times compared to controls, though worse Ocular Surface Disease Index (OSDI) vision-related subscores were associated with longer search times (P < 0.01). Search times showed no association with OSDI symptom subscores (P = 0.20) or objective measures of dry eye (P > 0.08 for Schirmer's testing without anesthesia, corneal fluorescein staining, and tear film breakup time).

CONCLUSIONS

Text-based visual search is slower for glaucoma patients with greater levels of VF loss and dry eye patients with greater self-reported visual difficulty, and these difficulties may contribute to decreased quality of life in these groups.

TRANSLATIONAL RELEVANCE

Visual search is impaired in glaucoma and dry eye groups compared to controls, highlighting the need for compensatory strategies and tools to assist individuals in overcoming their deficiencies.

Effect of glaucoma on eye movement patterns and laboratory-based hazard detection ability

Purpose

The mechanisms underlying the elevated crash rates of older drivers with glaucoma are poorly understood. A key driving skill is timely detection of hazards; however, the hazard detection ability of drivers with glaucoma has been largely unexplored. This study assessed the eye movement patterns and visual predictors of performance on a laboratory-based hazard detection task in older drivers with glaucoma.

Methods

Participants included 30 older drivers with glaucoma (71±7 years; average better-eye mean deviation (MD) = −3.1±3.2 dB; average worse-eye MD = −11.9±6.2 dB) and 25 age-matched controls (72±7 years). Visual acuity, contrast sensitivity, visual fields, useful field of view (UFoV; processing speeds), and motion sensitivity were assessed. Participants completed a computerised Hazard Perception Test (HPT) while their eye movements were recorded using a desk-mounted Tobii TX300 eye-tracking system. The HPT comprises a series of real-world traffic videos recorded from the driver’s perspective; participants responded to road hazards appearing in the videos, and hazard response times were determined.

Results

Participants with glaucoma exhibited an average of 0.42 seconds delay in hazard response time (p = 0.001), smaller saccades (p = 0.010), and delayed first fixation on hazards (p<0.001) compared to controls. Importantly, larger saccades were associated with faster hazard responses in the glaucoma group (p = 0.004), but not in the control group (p = 0.19). Across both groups, significant visual predictors of hazard response times included motion sensitivity, UFoV, and worse-eye MD (p<0.05).

Conclusions

Older drivers with glaucoma had delayed hazard response times compared to controls, with associated changes in eye movement patterns. The association between larger saccades and faster hazard response time in the glaucoma group may represent a compensatory behaviour to facilitate improved performance.

Searching for unity: Real-world versus item-based visual search in age-related eye disease

When studying visual search, item-based approaches using synthetic targets and distractors limit the real-world applicability of results. Everyday visual search can be impaired in patients with common eye diseases like glaucoma and age-related macular degeneration. We highlight some results in the literature that suggest assessment of real-word search tasks in these patients could be clinically useful.

Gradually Then Suddenly? Decline in Vision-Related Quality of Life as Glaucoma Worsens

Purpose. To evaluate the relationship between self-reported vision-related quality of life (VRQL) and visual field (VF) loss in people from glaucoma clinics. Methods. A postal survey using the National Eye Institute Visual Function Questionnaire (NEI VFQ-25) was administered to people with a range of VF loss identified from a UK hospital-based glaucoma service database. Trends were assessed in a composite score from NEI VFQ-25 against better-eye mean deviation (BEMD) using linear regression and a spline-fitting method that can highlight where a monotonic relationship may have different stages. Results. A total of 636 patients (median [interquartile range] BEMD -2.1 [-5.2, -0.4] dB, median age 70 [60, 77] years) were analysed. Analysis of trends in the data revealed an average patient loses approximately 2 units (out of 100) on NEI VFQ-25 for every loss of 1 dB (BEMD) as VF defects first become bilateral, up to BEMD -5 dB. NEI VFQ-25 deterioration then appears to slow before a more rapid phase of change (4-5 units per 1 dB loss) after BEMD worsens beyond -15 dB. Conclusions. Relationship between decline in VRQL and VF worsening in glaucoma is unlikely to be linear; it more likely has different phases, and these should be further explored in longitudinal studies.

Eye-Tracking as a Tool to Evaluate Functional Ability in Everyday Tasks in Glaucoma

To date, few studies have investigated the eye movement patterns of individuals with glaucoma while they undertake everyday tasks in real-world settings. While some of these studies have reported possible compensatory gaze patterns in those with glaucoma who demonstrated good task performance despite their visual field loss, little is known about the complex interaction between field loss and visual scanning strategies and the impact on task performance and, consequently, on quality of life. We review existing approaches that have quantified the effect of glaucomatous visual field defects on the ability to undertake everyday activities through the use of eye movement analysis. Furthermore, we discuss current developments in eye-tracking technology and the potential for combining eye-tracking with virtual reality and advanced analytical approaches. Recent technological developments suggest that systems based on eye-tracking have the potential to assist individuals with glaucomatous loss to maintain or even improve their performance on everyday tasks and hence enhance their long-term quality of life. We discuss novel approaches for studying the visual search behavior of individuals with glaucoma that have the potential to assist individuals with glaucoma, through the use of personalized programs that take into consideration the individual characteristics of their remaining visual field and visual search behavior.

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

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 (r_s = -0.280, P = 0.049), 24–2 right visual field index (r_s = -0.306, P = 0.030), 24–2 worse visual field index (r_s = -0.304, P = 0.032), and 10–2 worse mean deviation (r_s = -0.326, P = 0.025). Significant correlations were observed between mean fixation duration and 10–2 left mean deviation (r_s = -0.294, P = 0.045) and 10–2 worse mean deviation (r_s = -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.

'I didn't see that coming': simulated visual fields and driving hazard perception test performance

BACKGROUND

Evidence is limited regarding specific types of visual field loss associated with unsafe driving. We use novel gaze-contingent software to examine the effect of simulated visual field loss on computer-based driving hazard detection with the specific aim of testing the impact of scotomata located to the right and left of fixation.

METHODS

The 'hazard perception test' is a component of the UK driving licence examination, which measures speed of detecting 15 different hazards in a series of real-life driving films. We have developed a novel eye-tracking and computer set up capable of generating a realistic gaze-contingent scotoma simulation (GazeSS) overlaid on film content. Thirty drivers with healthy vision completed three versions of the hazard perception test in a repeated measures experiment. In two versions, GazeSS simulated a scotoma in the binocular field of view to the left or right of fixation. A third version was unmodified to establish baseline performance.

RESULTS

Participants' mean baseline hazard perception test score was 51 ± 7 (out of 75). This reduced to 46 ± 9 and 46 ± 11 when completing the task with a binocular visual field defect located to the left and right of fixation, respectively. While the main effect of simulated visual field loss on performance was statistically significant (p = 0.007), there were no average differences in the experimental conditions where a scotoma was located in the binocular visual field to the right or left of fixation.

CONCLUSION

Simulated visual field loss impairs driving hazard detection on a computer-based test. There was no statistically significant difference in average performance when the simulated scotoma was located to the right or left of fixation of the binocular visual field, but certain types of hazard caused more difficulties than others.

The Caledonian face test: A new test of face discrimination

This study aimed to develop a clinical test of face perception which is applicable to a wide range of patients and can capture normal variability. The Caledonian face test utilises synthetic faces which combine simplicity with sufficient realism to permit individual identification. Face discrimination thresholds (i.e. minimum difference between faces required for accurate discrimination) were determined in an "odd-one-out" task. The difference between faces was controlled by an adaptive QUEST procedure. A broad range of face discrimination sensitivity was determined from a group (N=52) of young adults (mean 5.75%; SD 1.18; range 3.33-8.84%). The test is fast (3-4 min), repeatable (test-re-test r(2)=0.795) and demonstrates a significant inversion effect. The potential to identify impairments of face discrimination was evaluated by testing LM who reported a lifelong difficulty with face perception. While LM's impairment for two established face tests was close to the criterion for significance (Z-scores of -2.20 and -2.27) for the Caledonian face test, her Z-score was -7.26, implying a more than threefold higher sensitivity. The new face test provides a quantifiable and repeatable assessment of face discrimination ability. The enhanced sensitivity suggests that the Caledonian face test may be capable of detecting more subtle impairments of face perception than available tests.

A view on glaucoma--are we seeing it clearly?

Successful clinical management of glaucoma should not simply be about control of intraocular pressure, but must equate to correct decisions about intensifying treatment when patients are at risk of developing 'visual disability'. Yet little is known about what visual field defects, at different stages of glaucoma, specifically affect patients' abilities to perform everyday visual tasks. One way to do this is to measure patient performance in tasks in a lab setting. Another way is to ask patients themselves. The latter can be revealing and demystify views about how patients perceive the world. This short commentary highlights some of the current research in this area.

Living with glaucoma: a qualitative study of functional implications and patients' coping behaviours

BACKGROUND

Sight loss from glaucoma can have a significant impact on functioning and performing everyday activities, but this varies between patients. The purpose of this study was to explore whether patients with glaucoma use different coping strategies in response to their vision loss.

METHODS

Audio-recorded semi-structured interviews were conducted with 16 patients (median age: 71 [interquartile range [IQR]: 68 to 77 years]; 50 % female) about their experiences of living with glaucoma. Patients had their glaucoma diagnosis for at least 5 years (range: 6 to 29 years) and had a range of disease severities (median best eye Mean Deviation was -9.1 dB [IQR: -12.9 to -4.1 dB]). A framework approach to analysis was taken whereby data was indexed using manual and computer-assisted methods, with codes applied to depict areas of functioning perceived to be impacted by glaucoma and coping behaviours used in response to these difficulties.

RESULTS

In order to maintain independence, some patients increased confidence by making practical changes such as adjusting lighting, using handrails and magnifying glasses, or actively changed aspects of their behaviour such as moving their head and eyes towards known areas of vision loss. Support from friends and family was often used, although some people worried about becoming a burden. Others imposed self-restrictions or gave up activities, thus compromising well-being and independence. Certain coping strategies were linked to time since diagnosis and location of vision loss. The type and quality of information received during clinical appointments, and the potential benefits of communication with other patients, emerged as other important themes.

CONCLUSIONS

Results from this qualitative study suggest that the adoption of certain coping behaviours and techniques may help some glaucomatous patients to adapt to their condition. An awareness of coping and adaptive strategies, in addition to the usual clinical tests, may provide a better insight into the impact of disease and help inform future educational and management strategies for glaucoma.

Impact of superior and inferior visual field loss on hazard detection in a computer-based driving test

PURPOSE

Binocular visual field (VF) loss is linked to driving impairment, guiding authorities to implement fitness to drive requirements for VFs. Yet, evidence is limited regarding the specific types of VF defect that impede driving. This study used a novel gaze-contingent display to test the hypothesis that superior VF loss impacts detection of driving hazards more than inferior loss.

METHODS

The Hazard Perception Test (HPT) is a computer-based component of the UK examination for learner drivers. It measures the response rate for detecting hazards in a series of real-life driving films, yielding a score out of 75, calculated based on the efficiency of detecting 15 hazards. Thirty UK drivers with healthy vision completed three versions of the HPT in a random order. In two versions, a computer set-up incorporating an eye-tracker modified a simulated VF defect in the superior and inferior VFs, respectively, according to the users' real-time gaze as they completed the HPT. The other version was unmodified to measure the baseline performance.

RESULTS

Participants' mean score at baseline was 49/75 (SD=9). Mean (SD) performance fell by 18% (40(11)) when viewing films with a superior defect and 12% with an inferior defect (43(10)). These average differences were statistically significant (p<0.001; 95% CI for mean difference=1-7) CONCLUSIONS: In this study, simulated VF defects impaired the ability to detect driving hazards relative to participants' normal performances, with superior defects having more impact than inferior defects. These results could help inform the design of fairer tests of the VF component for fitness to drive.

What's on TV? Detecting age-related neurodegenerative eye disease using eye movement scanpaths

PURPOSE

We test the hypothesis that age-related neurodegenerative eye disease can be detected by examining patterns of eye movement recorded whilst a person naturally watches a movie.

METHODS

Thirty-two elderly people with healthy vision (median age: 70, interquartile range [IQR] 64-75 years) and 44 patients with a clinical diagnosis of glaucoma (median age: 69, IQR 63-77 years) had standard vision examinations including automated perimetry. Disease severity was measured using a standard clinical measure (visual field mean deviation; MD). All study participants viewed three unmodified TV and film clips on a computer set up incorporating the Eyelink 1000 eyetracker (SR Research, Ontario, Canada). Eye movement scanpaths were plotted using novel methods that first filtered the data and then generated saccade density maps. Maps were then subjected to a feature extraction analysis using kernel principal component analysis (KPCA). Features from the KPCA were then classified using a standard machine based classifier trained and tested by a 10-fold cross validation which was repeated 100 times to estimate the confidence interval (CI) of classification sensitivity and specificity.

RESULTS

Patients had a range of disease severity from early to advanced (median [IQR] right eye and left eye MD was -7 [-13 to -5] dB and -9 [-15 to -4] dB, respectively). Average sensitivity for correctly identifying a glaucoma patient at a fixed specificity of 90% was 79% (95% CI: 58-86%). The area under the Receiver Operating Characteristic curve was 0.84 (95% CI: 0.82-0.87).

CONCLUSIONS

Huge data from scanpaths of eye movements recorded whilst people freely watch TV type films can be processed into maps that contain a signature of vision loss. In this proof of principle study we have demonstrated that a group of patients with age-related neurodegenerative eye disease can be reasonably well separated from a group of healthy peers by considering these eye movement signatures alone.

Eye movements and reading in glaucoma: observations on patients with advanced visual field loss

PURPOSE

To investigate the relationship between reading speed and eye movements in patients with advanced glaucomatous visual field (VF) defects and age-similar visually healthy people.

METHODS

Eighteen patients with advanced bilateral VF defects (mean age: 71, standard deviation [SD]: 7 years) and 39 controls (mean age: 67, SD: 8 years) had reading speed measured using short passages of text on a computer set-up incorporating eye tracking. Scanpaths were plotted and analysed from these experiments to derive measures of 'perceptual span' (total number of letters read per number of saccades) and 'text saturation' (the distance between the first and last fixation on lines of text). Another eye movement measure, termed 'saccadic frequency' (total number of saccades made to read a single word), was derived from a separate lexical decision task, where words were presented in isolation.

RESULTS

Significant linear association was demonstrated between perceptual span and reading speed in patients (R (2) = 0.42) and controls (R (2) = 0.56). Linear association between saccadic frequency during the LDT and reading speed was also found in patients (R (2) = 0.42), but not in controls (R (2) = 0.02). Patients also exhibited greater average text saturation than controls (P = 0.004).

CONCLUSION

Some, but not all, patients with advanced VF defects read slower than controls using short text passages. Differences in eye movement behaviour may partly account for this variability in patients. These patients were shown to saturate lines of text more during reading, which may explain previously-reported difficulties with sustained reading.

Using eye tracking to assess reading performance in patients with glaucoma: a within-person study

Reading is often cited as a demanding task for patients with glaucomatous visual field (VF) loss, yet reading speed varies widely between patients and does not appear to be predicted by standard visual function measures. This within-person study aimed to investigate reading duration and eye movements when reading short passages of text in a patient's worse eye (most VF damage) when compared to their better eye (least VF damage). Reading duration and saccade rate were significantly different on average in the worse eye when compared to the better eye (P < 0.001) in 14 patients with glaucoma that had median (interquartile range) between-eye difference in mean deviation (MD; a standard clinical measure for VF loss) of 9.8 (8.3 to 14.8) dB; differences were not related to the size of the difference in MD between eyes. Patients with a more pronounced effect of longer reading duration on their worse eye made a larger proportion of "regressions" (backward saccades) and "unknown" EMs (not adhering to expected reading patterns) when reading with the worse eye when compared to the better eye. A between-eye study in patients with asymmetric disease, coupled with eye tracking, provides a useful experimental design for exploring reading performance in glaucoma.

Characterization of field loss based on microperimetry is predictive of face recognition difficulties

PURPOSE

To determine how visual field loss as assessed by microperimetry is correlated with deficits in face recognition.

METHODS

Twelve patients (age range, 26-70 years) with impaired visual sensitivity in the central visual field caused by a variety of pathologies and 12 normally sighted controls (control subject [CS] group; age range, 20-68 years) performed a face recognition task for blurred and unblurred faces. For patients, we assessed central visual field loss using microperimetry, fixation stability, Pelli-Robson contrast sensitivity, and letter acuity.

RESULTS

Patients were divided into two groups by microperimetry: a low vision (LV) group (n = 8) had impaired sensitivity at the anatomical fovea and/or poor fixation stability, whereas a low vision that excluded the fovea (LV:F) group (n = 4) was characterized by at least some residual foveal sensitivity but insensitivity in other retinal regions. The LV group performed worse than the other groups at all blur levels, whereas the performance of the LV:F group was not credibly different from that of the CS group. The performance of the CS and LV:F groups deteriorated as blur increased, whereas the LV group showed consistently poor performance regardless of blur. Visual acuity and fixation stability were correlated with face recognition performance.

CONCLUSIONS

Persons diagnosed as having disease affecting the central visual field can recognize faces as well as persons with no visual disease provided that they have residual sensitivity in the anatomical fovea and show stable fixation patterns. Performance in this task is limited by the upper resolution of nonfoveal vision or image blur, whichever is worse.