Impact of age‐related macular degeneration on object searches in realistic panoramic scenes

Saccades during visual search in macular degeneration

Macular degeneration (MD) compromises both high-acuity vision and eye movements when the foveal regions of both eyes are affected. Individuals with MD adapt to central field loss by adopting a preferred retinal locus (PRL) for fixation. Here, we investigate how individuals with bilateral MD use eye movements to search for targets in a visual scene under realistic binocular viewing conditions. Five individuals with binocular scotomata, 3 individuals with monocular scotomata and 6 age-matched controls participated in our study. We first extensively mapped the binocular scotoma with an eyetracker, while fixation was carefully monitored (Vullings & Verghese, 2020). Participants then completed a visual search task where 0, 1, or 2 Gaussian blobs were distributed randomly across a natural scene. Participants were given 10 s to actively search the display and report the number of blobs. An analysis of saccade characteristics showed that individuals with binocular scotomata made more saccades in the direction of their scotoma than controls for the same directions. Saccades in the direction of the scotoma were typically of small amplitude, and did not fully uncover the region previously hidden by the scotoma. Rather than make more saccades to explore this hidden region, participants frequently made saccades back toward newly uncovered regions. Backward saccades likely serve a similar purpose to regressive saccades exhibited during reading in MD, by inspecting previously covered regions near the direction of gaze. Our analysis suggests that the higher prevalence of backward saccades in individuals with binocular scotomata might be related to the PRL being adjacent to the scotoma.

Simulated central vision loss does not impair implicit location probability learning when participants search through simple displays

Central vision loss disrupts voluntary shifts of spatial attention during visual search. Recently, we reported that a simulated scotoma impaired learned spatial attention towards regions likely to contain search targets. In that task, search items were overlaid on natural scenes. Because natural scenes can induce explicit awareness of learned biases leading to voluntary shifts of attention, here we used a search display with a blank background less likely to induce awareness of target location probabilities. Participants searched both with and without a simulated central scotoma: a training phase contained targets more often in one screen quadrant and a testing phase contained targets equally often in all quadrants. In Experiment 1, training used no scotoma, while testing alternated between blocks of scotoma and no-scotoma search. Experiment 2 training included the scotoma and testing again alternated between scotoma and no-scotoma search. Response times and saccadic behaviors in both experiments showed attentional biases towards the high-probability target quadrant during scotoma and no-scotoma search. Whereas simulated central vision loss impairs learned spatial attention in the context of natural scenes, our results show that this may not arise from impairments to the basic mechanisms of attentional learning indexed by visual search tasks without scenes.

The importance of peripheral vision when searching 3D real-world scenes: A gaze-contingent study in virtual reality

Visual search in natural scenes is a complex task relying on peripheral vision to detect potential targets and central vision to verify them. The segregation of the visual fields has been particularly established by on-screen experiments. We conducted a gaze-contingent experiment in virtual reality in order to test how the perceived roles of central and peripheral visions translated to more natural settings. The use of everyday scenes in virtual reality allowed us to study visual attention by implementing a fairly ecological protocol that cannot be implemented in the real world. Central or peripheral vision was masked during visual search, with target objects selected according to scene semantic rules. Analyzing the resulting search behavior, we found that target objects that were not spatially constrained to a probable location within the scene impacted search measures negatively. Our results diverge from on-screen studies in that search performances were only slightly affected by central vision loss. In particular, a central mask did not impact verification times when the target was grammatically constrained to an anchor object. Our findings demonstrates that the role of central vision (up to 6 degrees of eccentricities) in identifying objects in natural scenes seems to be minor, while the role of peripheral preprocessing of targets in immersive real-world searches may have been underestimated by on-screen experiments.

Parkinson's disease-related changes in the behavioural synergy between eye movements and postural movements

Patients with Parkinson's disease (PD patients) have been shown to exhibit abnormally low levels of synergy in their posture control. The goal of this study was to determine how synergic interactions between vision and posture are affected in PD patients. These synergic interactions were expected to be impaired because PD affects the basal ganglia, which are involved in the modulation of both types of movement. Twenty patients (mean age: 60) on levodopa and 20 age-matched-controls (mean age: 61) performed a precise visual task (searching for targets in an image) and an unprecise control task (randomly looking at an image) in which images were projected onto a large panoramic display. Lower back, upper back, head and eye movements were recorded simultaneously. To test behavioural synergies, Pearson correlations between eye and postural movements were analysed. The relationships between eye movements and upper and lower back movements were impaired in the patients. The age-matched controls did not show any significant correlations between eye and postural movements. Overall, our results showed that the PD patients failed to adjust and control their postural stability for success in the visual task. The impaired synergy between eye and postural movements was not related to clinical variables-probably because our patients had early-stage PD. Our results showed that impairments in synergy can occur very early in PD. Hence, the analysis of this synergy might provide a better understanding of postural instability, visual task performance in the upright stance, and perhaps the risk of falls in PD patients.

Vision, attention, and driving

Safe driving demands the coordination of multiple sensory and cognitive functions, such as vision and attention. Patients with neurologic or ophthalmic disease are exposed to selective pathophysiologic insults to driving-critical systems, placing them at a higher risk for unsafe driving and restricted driving privileges. Here, we evaluate how vision and attention contribute to unsafe driving across different patient populations. In ophthalmic disease, we focus on macular degeneration, glaucoma, diabetic retinopathy, and cataract; in neurologic disease, we focus on Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Unsafe driving is generally associated with impaired vision and attention in ophthalmic and neurologic patients, respectively. Furthermore, patients with ophthalmic disease experience some degree of impairment in attention. Similarly, patients with neurologic disease experience some degree of impairment in vision. While numerous studies have demonstrated a relationship between impaired vision and unsafe driving in neurologic disease, there remains a dearth of knowledge regarding the relationship between impaired attention and unsafe driving in ophthalmic disease. In summary, this chapter confirms-and offers opportunities for future research into-the contribution of vision and attention to safe driving.

Novel computer-based assessments of everyday visual function in people with age-related macular degeneration

PURPOSE

To test the hypothesis that the performance in novel computer-based tasks of everyday visual function worsens with disease severity in people with non-neovascular age-related macular degeneration.

METHODS

Participants with and without non-neovascular age-related macular degeneration (≥60 years, minimum logMAR binocular visual acuity 0.7) performed a series of standard visual function tests and two novel computer-based tasks. In a visual search task, participants had to locate an image of a single real-world object within an array of 49 distractor images. Next, in a series of simulated dynamic driving scenes, participants were asked to identify one or two approaching real-world road signs and then select these road signs from four options. Outcome measures were median response times and total correct responses.

RESULTS

Forty-nine participants had no macular disease (n = 11), early/intermediate age-related macular degeneration (n = 16) or geographic atrophy (n = 22). Groups were age-similar with median (interquartile range) logMAR visual acuity of 0.00 (-0.08,0.12), 0.13 (-0.08,0.70) and 0.32 (0.12,0.70) respectively. Median (interquartile range) visual search response times were 1.9 (1.0,2.4), 1.8 (1.1,3.7) and 2.4 (1.2,6.0) seconds respectively. Median (interquartile range) road sign response times (single road signs) were 1.2 (0.4,1.7), 1.5 (0.9,2.8) and 1.8 (1.0,5.5) seconds respectively. Median (interquartile range) road sign response times (double road signs) were 1.7 (0.7,2.4), 2.3 (1.2,3.1) and 2.5 (1.7,6) seconds respectively. Participants with geographic atrophy recorded slower response times in all tasks and over 50% performed outside the normative limit for task performance. There were no significant differences between groups in total correct responses across all tasks.

CONCLUSIONS

In a novel computer-based assessment, people with increasing severity of age-related macular degeneration take longer to perform visual search of everyday objects and take longer to identify road signs than those with no age-related macular degeneration. These novel assessments could be useful as patient-relevant, secondary outcomes for clinical trials.

Object search in neovascular age-related macular degeneration: the crowding effect

BACKGROUND

Visual search, an activity that relies on central vision, is frequent in daily life. This study investigates the effect of spacing between items in an object search task in participants with central vision loss.

METHODS

Patients with neovascular age-related macular degeneration (AMD), age-matched controls, and young controls were included. The stimuli were displays of four, six and nine objects randomly presented in a 'crowded' (spacing 1.5°) or 'uncrowded' (spacing 6°) condition. For each of 96 trials, participants were asked to search for a predefined target that remained on the screen until the response was recorded. Accuracy, search time, and eye movements (number of fixations and scan path ratio) were recorded.

RESULTS

Compared to older controls, accuracy decreased by 31 per cent and search time increased by 61 per cent in AMD participants. Ageing also affected performance with a lower accuracy by 13.5 per cent and longer search times by 46 per cent in older compared to younger controls. Increasing the spacing between elements increased accuracy by 21 per cent in AMD participants but it had no effect in older and younger controls. Performance was not related to visual acuity or to duration of neovascular AMD, but search time was correlated to the lesion size in the 'crowded' condition.

CONCLUSIONS

Object search is ubiquitous in daily life activities. When visual acuity is irrevocably reduced, increasing the spacing between elements can reliably improve object search performance in patients.