Abstract
BackgroundGlaucoma has been shown to lead to disability in many daily tasks including visual search. This study aims to determine whether the saccadic eye movements of people with glaucoma differ from those of people with normal vision, and to investigate the association between eye movements and impaired visual search.MethodsForty patients (mean age: 67 [SD: 9] years) with a range of glaucomatous visual field (VF) defects in both eyes (mean best eye mean deviation [MD]: –5.9 (SD: 5.4) dB) and 40 age-related people with normal vision (mean age: 66 [SD: 10] years) were timed as they searched for a series of target objects in computer displayed photographs of real world scenes. Eye movements were simultaneously recorded using an eye tracker. Average number of saccades per second, average saccade amplitude and average search duration across trials were recorded. These response variables were compared with measurements of VF and contrast sensitivity.ResultsThe average rate of saccades made by the patient group was significantly smaller than the number made by controls during the visual search task (P = 0.02; mean reduction of 5.6% (95% CI: 0.1 to 10.4%). There was no difference in average saccade amplitude between the patients and the controls (P = 0.09). Average number of saccades was weakly correlated with aspects of visual function, with patients with worse contrast sensitivity (PR logCS; Spearman’s rho: 0.42; P = 0.006) and more severe VF defects (best eye MD; Spearman’s rho: 0.34; P = 0.037) tending to make less eye movements during the task. Average detection time in the search task was associated with the average rate of saccades in the patient group (Spearman’s rho = −0.65; P < 0.001) but this was not apparent in the controls.ConclusionsThe average rate of saccades made during visual search by this group of patients was fewer than those made by people with normal vision of a similar average age. There was wide variability in saccade rate in the patients but there was an association between an increase in this measure and better performance in the search task. Assessment of eye movements in individuals with glaucoma might provide insight into the functional deficits of the disease.
Highlights
Glaucoma has been shown to lead to disability in many daily tasks including visual search
Abnormal eye movement behaviour has previously been observed in patients with functional difficulties as a result of retinopathies other than glaucoma; for instance, evidence suggests a link between eye movements and impaired reading speed in age-related macular degeneration (AMD) [19,20]
Eye movement strategies have been investigated during difficulties observed with mobility in retinitis pigmentosa (RP), with patients with increasing visual field (VF) loss tending to fixate on alternative locations away from their intended goal when walking compared with controls with normal vision [21]
Summary
Glaucoma has been shown to lead to disability in many daily tasks including visual search. Some attempts have been made to objectively characterise these difficulties in laboratory based experiments of ‘everyday’ vision-based tasks; for example, studies have reported that some patients with glaucoma display impairment in tasks such as reading [10], walking and balance tests [11,12,13], driving [14,15], reaching and grasping for household objects [16], face recognition [17] and visual search [18] For the latter some patients with glaucomatous visual field (VF) defects in both eyes were shown to be significantly slower to locate target objects in computer displayed images of everyday scenes when compared to people with healthy vision of a similar age. Training patients to alter the number of fixations they make has been shown to lead to improvements in their task performance [22,23] suggesting studies of eye movements in relation to ocular disease could potentially be useful for rehabilitation
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