Dataset Information

Fixational eye movements predict visual sensitivity.

ABSTRACT: During steady fixation, observers make small fixational saccades at a rate of around 1-2 per second. Presentation of a visual stimulus triggers a biphasic modulation in fixational saccade rate-an initial inhibition followed by a period of elevated rate and a subsequent return to baseline. Here we show that, during passive viewing, this rate signature is highly sensitive to small changes in stimulus contrast. By training a linear support vector machine to classify trials in which a stimulus is either present or absent, we directly compared the contrast sensitivity of fixational eye movements with individuals' psychophysical judgements. Classification accuracy closely matched psychophysical performance, and predicted individuals' threshold estimates with less bias and overall error than those obtained using specific features of the signature. Performance of the classifier was robust to changes in the training set (novel subjects and/or contrasts) and good prediction accuracy was obtained with a practicable number of trials. Our results indicate a tight coupling between the sensitivity of visual perceptual judgements and fixational eye control mechanisms. This raises the possibility that fixational saccades could provide a novel and objective means of estimating visual contrast sensitivity without the need for observers to make any explicit judgement.

SUBMITTER: Scholes C

PROVIDER: S-EPMC4633872 | biostudies-other | 2015 Oct

REPOSITORIES: biostudies-other

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Fixational eye movements predict visual sensitivity.

Scholes Chris C McGraw Paul V PV Nyström Marcus M Roach Neil W NW

Proceedings. Biological sciences 20151001 1817

During steady fixation, observers make small fixational saccades at a rate of around 1-2 per second. Presentation of a visual stimulus triggers a biphasic modulation in fixational saccade rate-an initial inhibition followed by a period of elevated rate and a subsequent return to baseline. Here we show that, during passive viewing, this rate signature is highly sensitive to small changes in stimulus contrast. By training a linear support vector machine to classify trials in which a stimulus is ei ...[more]

PMID: 26468244

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Project description: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.

Dataset Information

Fixational eye movements predict visual sensitivity.

Publications

Fixational eye movements predict visual sensitivity.

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