ORCID Profile
0000-0002-3548-9104
Current Organisations
The University of Auckland
,
University College London
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Sensory Processes, Perception and Performance | Psychology
Publisher: Cold Spring Harbor Laboratory
Date: 02-12-2020
DOI: 10.1101/2020.11.30.20234476
Abstract: Retinitis pigmentosa is an hereditary disease causing photoreceptor degeneration and permanent vision loss. Retinal implantation of a stimulating electrode array is a new treatment for retinitis pigmentosa, but quantification of its efficacy is the subject of ongoing work. This review evaluates vision-related outcomes resulting from retinal implantation in participants with retinitis pigmentosa. We searched MEDLINE and Embase for journal articles published since 1 January 2015. We selected articles describing studies of implanted participants that reported post-implantation measurement of vision. We extracted study information including design, participants’ residual vision, comparators, and assessed outcomes. To assess risk of bias, we used signalling questions and a target trial. Our search returned 425 abstracts. We reviewed the full text of 34 articles. We judged all studies to be at high risk of bias due to study design or experimental conduct. Regarding design, studies lacked the measures that typical clinical trials take to protect against bias (e.g., control groups and masking). Regarding experimental conduct, outcome measures were rarely comparable before and after implantation, and psychophysical methods were prone to bias (subjective, not forced-choice, methods). The most common comparison found was between post-implantation visual function with the device powered off versus on. This comparison is at high risk of bias. There is a need for high-quality evidence of efficacy of retinal implantation to treat retinitis pigmentosa. For patients and clinicians to make informed choices about retinitis pigmentosa treatment, visual function restored by retinal implantation must be properly quantified and reported.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-2009
DOI: 10.1167/9.12.1
Publisher: SAGE Publications
Date: 22-02-2016
Publisher: Elsevier BV
Date: 10-2014
Publisher: Cold Spring Harbor Laboratory
Date: 23-09-2021
DOI: 10.1101/2021.09.20.461009
Abstract: In the human visual system, cerebral cortex combines left- and right-eye retinal inputs, enabling single, comfortable binocular vision. In visual cortex, the signals from each eye inhibit one another (interocular suppression). While this mechanism may be disrupted by e.g. traumatic brain injury, clinical assessments of interocular suppression are subjective, qualitative, and lack reliability. EEG is a potentially useful clinical tool for objective, quantitative assessment of binocular vision. In a cohort of normal participants, we measured occipital, visual evoked potentials (VEPs) in response to dichoptically-presented vertical and/or horizontal sine-wave gratings. Response litudes to orthogonal gratings were greater than that of parallel gratings, which were in turn greater than that of monocular gratings. Our results indicate that interocular suppression is (normally) balanced, orientation-tuned, and that suppression per se is reduced for orthogonal gratings. This objective measure of suppression may have application in clinical settings.
Publisher: Elsevier BV
Date: 04-2012
DOI: 10.1016/J.VISRES.2012.02.010
Abstract: Previous studies of peripheral vision have shown that detection acuity is superior to resolution acuity for gratings over a range of contrasts, which is attributed to different limiting mechanisms (contrast insufficiency and neural unders ling) for the two tasks. To extend the analysis to letters in a way that avoided luminance cues, we used "vanishing optotype" characters, conveying second-order information, and constructed from tripole strokes having the same mean luminance as the surround. We measured the minimum letter size for detection and identification tasks for two different pairs of vanishing optotype characters (O vs. + and orthogonally oriented Landolt-C's) as a function of contrast in central and peripheral vision. Foveally there was no significant difference between detection acuity and resolution acuity for either pair of letters over a range of stimulus contrasts from 20% to 100%, indicating performance is contrast-limited for both tasks. The same result was obtained at 30° eccentricity in the peripheral field for the O vs. + letters, again indicating performance is contrast-limited for both tasks. However, resolution acuity for the Landolt-C letters was significantly worse than detection acuity in the periphery over the same range of contrasts, which suggests performance is limited by neural unders ling for these letters. All of our experimental results are explained by a model of neural s ling in which detection acuity is determined by the size of neural receptive fields relative to the dimensions of the tripole responsible for spatial contrast, whereas resolution acuity is determined by the spacing of receptive fields relative to the spacing between strokes responsible for letter form.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-2009
DOI: 10.1167/9.10.1
Publisher: Informa UK Limited
Date: 05-2020
DOI: 10.1111/CXO.12958
Publisher: Wiley
Date: 11-2018
DOI: 10.1111/OPO.12590
Abstract: Sloan letters displayed by the Electronic Visual Acuity ( EVA ) system are the gold standard for recognition acuity measurement in research settings. However, letters are not always appropriate for children. The Auckland Optotypes ( TAO ) are a new, open‐access set of 10 pictograms available in regular and vanishing formats. We sought to assess feasibility of using both formats of TAO for measuring visual acuity ( VA ) in children using a Bayesian adaptive staircase, in a community setting. We tested 121 children (5–12 years old) with both formats of TAO , a handheld flipchart vision screener (Parr vision test), as well as the gold standard EVA . We measured feasibility of the three comparison tests in three ways. First, using limits of agreement (LoA) with EVA , second, calculating area under the receiver operating characteristic curve ( AUC ), and finally, investigating trial‐by‐trial responses. Agreement between tests was within test‐retest reliability of EVA measures (Lo A TAO regular = ±0.14, Lo A TAO vanishing = ±0.15, Lo A P arr = ±0.16 log MAR ). TAO tests were highly effective at identifying children with vision impairment ( AUC TAO regular = 0.96, AUC TAO vanishing = 0.95), whereas Parr was less effective ( AUC P arr = 0.82). In 5–6 year old children there was an enhanced advantage of TAO ( AUC TAO regular = 0.97, AUC TAO vanishing = 0.98) over Parr ( AUC P arr = 0.75). Although each child completed 16 trials, approximately 10 trials were sufficient to achieve excellent LoA, and six trials sufficient for accurate screening. Threshold VA assessment and vision screening are feasible using both vanishing and regular formats of TAO.
Publisher: Society for Neuroscience
Date: 06-05-2015
DOI: 10.1523/JNEUROSCI.4645-14.2015
Abstract: To judge the overall direction of a shoal of fish or a crowd of people, observers must integrate motion signals across space and time. The limits on our ability to pool motion have largely been established using the motion coherence paradigm, in which observers report the direction of coherently moving dots amid randomly moving noise dots. Poor performance by autistic in iduals on this task has widely been interpreted as evidence of disrupted integrative processes. Critically, however, motion coherence thresholds are not necessarily limited only by pooling. They could also be limited by imprecision in estimating the direction of in idual elements or by difficulties segregating signal from noise. Here, 33 children with autism 6–13 years of age and 33 age- and ability-matched typical children performed a more robust task reporting mean dot direction both in the presence and the absence of directional variability alongside a standard motion coherence task. Children with autism were just as sensitive to directional differences as typical children when all elements moved in the same direction (no variability). However, remarkably, children with autism were more sensitive to the average direction in the presence of directional variability, providing the first evidence of enhanced motion integration in autism. Despite this improved averaging ability, children with autism performed comparably to typical children in the motion coherence task, suggesting that their motion coherence thresholds may be limited by reduced segregation of signal from noise. Although potentially advantageous under some conditions, increased integration may lead to feelings of “sensory overload” in children with autism.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-09-2010
DOI: 10.1167/10.11.5
Abstract: Although visual systems are optimized to deal with the natural visual environment, our understanding of human motion perception is in large part based on the use of artificial stimuli. Here, we assessed observers' ability to estimate the direction of translating natural images and fractals by having them adjust the orientation of a subsequently viewed line. A system of interleaved staircases, driven by observers' direction estimates, ensured that stimuli were presented near one of 16 reference directions. The resulting error distributions (i.e., the differences between reported and true directions) reveal several anisotropies in global motion processing. First, observers' estimates are biased away from cardinal directions (reference repulsion). Second, the standard deviations of estimates show an "oblique effect" being ∼45% lower around cardinal directions. Third, errors around cardinal directions are more likely (∼22%) to approach zero than would be consistent with Gaussian-distributed errors, suggesting that motion processing minimizes the number as well as magnitude of errors. Fourth, errors are similar for natural scenes and fractals, indicating that observers do not use top-down information to improve performance. Finally, adaptation to unidirectional motion modifies observers' bias by lifying existing repulsion (e.g., around cardinal directions). This bias change can improve direction discrimination but is not due to a reduction in variability.
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 05-2022
End Date: 04-2025
Amount: $285,504.00
Funder: Australian Research Council
View Funded Activity