Optometry and Vision Sciences - Research Publications
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ItemThe effect of mental load on psychophysical and visual evoked potential visual acuity(WILEY, 2022-05)PURPOSE: Under real-world conditions, tasks dependent on visual acuity may need to be performed in the presence of a mental load arising from concurrent, non-visual tasks. Therefore, measuring visual acuity concurrently with mentally demanding tasks may reflect a patient's vision more accurately. This study was designed to evaluate the impact of task-induced mental load on high contrast visual acuity, as measured using a letter chart and estimated via sweep visual evoked potentials (sweep VEP). METHODS: Visual acuity was determined using the Freiburg Vision Test, and also using sweep VEP tested stepwise, from coarse to fine, over 13 spatial frequencies, in 31 healthy participants (aged 22.4 ± 3.6 years). Recordings were repeated while participants concurrently performed an auditory 2-back task. Mental load of the n-back task was confirmed through subjective ratings. RESULTS: Visual acuity determined with the Freiburg Vision Test worsened from -0.02 ± 0.12 to 0.04 ± 0.15 logMAR under mental load (p = 0.03). Visual acuities estimated by sweep VEPs worsened from 0.38 ± 0.1 to 0.47 ± 0.1 logMAR (p < 0.001). While the slope of the VEP amplitude versus spatial frequency function steepened significantly with mental load (p = 0.01), VEP noise levels were not significantly affected (p = 0.07). CONCLUSION: Visual acuity reduces significantly with a concurrent task that produces mental load. At least part of this reduction appears to be related to alterations in responses within the visual cortex, rather than being purely attributable to higher-level distraction effects.
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ItemThe Effects of Glare on the Perception of Visual Motion as a Function of Age(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2022-09)PURPOSE: The purpose of this study was to determine the impact of glare, that simulated the effects of oncoming vehicle headlights, and age on different aspects of motion perception in central and peripheral vision. METHODS: Twenty younger (mean age = 25 years, range = 20-32 years) and 20 older (mean age = 70 years, range = 60-79 years) visually healthy adults completed four visual motion tasks. Stimuli were presented centrally and at 15 degrees horizontal eccentricity for 2 viewing conditions: glare (continuous, off-axis) versus no glare. Motion tasks included minimum Gabor contrast required to discriminate direction of motion, translational global motion coherence, minimum duration of a Gabor to determine direction of motion (2 different size Gabors to determine spatial surround suppression), and biological motion detection in noise. Intraocular straylight was also measured (C-Quant). RESULTS: Older adults had increased intraocular straylight compared with younger adults (P < 0.001). There was no significant effect of glare on motion thresholds in either group for motion contrast (P = 0.47), translational global motion (P = 0.13), biological motion (P = 0.18), or spatial surround suppression of motion (P = 0.29). Older adults had elevated thresholds for motion contrast (P < 0.001), biological motion (P < 0.001), and differences in surround suppression of motion (P = 0.04), relative to the younger group, for both the glare and no-glare conditions. CONCLUSIONS: Although older adults had elevated thresholds for some motion perception tasks, glare from a continuous off-axis light source did not further elevate these thresholds either in central or peripheral vision. TRANSLATIONAL RELEVANCE: A glare source that simulated the effect of oncoming headlights, did not impact motion perception measures relevant to driving.
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ItemInterventions for the Management of Computer Vision Syndrome A Systematic Review and Meta-analysis(ELSEVIER SCIENCE INC, 2022-10)TOPIC: To evaluate the efficacy and safety of interventions for treating eye strain related to computer use relative to placebo or no treatment. CLINICAL RELEVANCE: Computer use is pervasive and often associated with eye strain, referred to as computer vision syndrome (CVS). Currently, no clinical guidelines exist to help practitioners provide evidence-based advice about CVS treatments, many of which are marketed directly to patients. This systematic review and meta-analysis was designed to help inform best practice for eye care providers. METHODS: Eligible randomized controlled trials (RCTs) were identified in Ovid MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, and trial registries, searched from inception through November 23, 2021. Eligible studies were appraised for risk of bias and were synthesized. The certainty of the body of evidence was judged using the Grading of Recommendations, Assessment, Development, and Evaluation system. Standardized mean differences (SMDs) were used when differently scaled measures were combined. RESULTS: Forty-five RCTs, involving 4497 participants, were included. Multifocal lenses did not improve visual fatigue scores compared with single-vision lenses (3 RCTs; SMD, 0.11; 95% confidence interval [CI], -0.14 to 0.37; P = 0.38). Visual fatigue symptoms were not reduced by blue-blocking spectacles (3 RCTs), with evidence judged of low certainty. Relative to placebo, oral berry extract supplementation did not improve visual fatigue (7 RCTs; SMD, -0.27; 95% CI, -0.70 to 0.16; P = 0.22) or dry eye symptoms (4 RCTs; SMD, -0.10; 95% CI, -0.54 to 0.33; P = 0.65). Likewise, berry extract supplementation had no significant effects on critical flicker-fusion frequency (CFF) or accommodative amplitude. Oral omega-3 supplementation for 45 days to 3 months improved dry eye symptoms (2 RCTs; mean difference [MD], -3.36; 95% CI, -3.63 to -3.10 on an 18 unit scale; P < 0.00001) relative to placebo. Oral carotenoid supplementation improved CFF (2 RCTs; MD, 1.55 Hz; 95% CI, 0.42 to 2.67 Hz; P = 0.007) relative to placebo, although the clinical significance of this finding is unclear. DISCUSSION: We did not identify high-certainty evidence supporting the use of any of the therapies analyzed. Low-certainty evidence suggested that oral omega-3 supplementation reduces dry eye symptoms in symptomatic computer users.
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ItemMotion perception at mesopic light levels: effects of physiological ageing and eccentricity(WILEY, 2021-03)PURPOSE: To explore the differential effects of age and eccentricity on the perception of motion at photopic and mesopic light levels. METHODS: Thirty-six visually normal participants (18 younger; mean age 25 years, range: 20-31) and (18 older; mean age 70 years, range: 60-79) underwent two testing sessions, one at photopic and one at mesopic light levels. In each session, motion perception was tested binocularly at two eccentricities (centrally, and peripherally at 15° rightwards and 5° superior to the horizontal) for four motion tasks: minimum contrast of a drifting Gabor to identify motion direction (motion contrast); translational global motion coherence; biological motion embedded in noise and the minimum duration of a high-contrast Gabor to determine the direction of motion, using two Gabor sizes to measure spatial surround suppression of motion. RESULTS: There was a significant main effect of light condition (higher thresholds in mesopic) for motion contrast (p < 0.001), translational global motion (p = 0.001) and biological motion (p < 0.001); a significant main effect of age (higher thresholds in older adults) for motion contrast (p < 0.001) and biological motion (p = 0.04) and a significant main effect of eccentricity (higher thresholds peripherally) for motion contrast (p < 0.001) and biological motion (p < 0.001). Additionally, we found a significant three-way interaction between light levels, age and eccentricity for translational global motion (similar increase in mesopic thresholds centrally for both groups, but a much larger deterioration in older adult's peripheral mesopic thresholds, p = 0.02). Finally, we found a two-way interaction between light condition and eccentricity for translational global motion (higher values in central mesopic relative to peripheral photopic, p = 0.001) and for biological motion (higher values in peripheral mesopic relative to central photopic, p < 0.001). CONCLUSIONS: For the majority of tasks assessed, motion perception was reduced in mesopic relative to photopic conditions, to a similar extent in both age groups. However, because some older adults exhibited elevated thresholds even under photopic conditions, particularly in the periphery, the ability to detect mesopic moving stimuli even at high contrast was markedly impaired in some individuals. Our results imply age-related differences in the detection of peripheral moving stimuli at night that might impact hazard avoidance and night driving ability.
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ItemInsights into Australian optometrists' knowledge and attitude towards prescribing blue light-blocking ophthalmic devices(WILEY, 2019-05)PURPOSE: The aim of this cross-sectional study was to survey Australian optometrists regarding their attitudes towards, and knowledge of, blue light-blocking lenses designed to attenuate blue light transmission to the eye. METHODS: A 29-item survey was distributed at a major national optometry education conference and through professional networks. Respondents provided information regarding their demographics and practice modalities, knowledge about the potential effects of blue light, and attitudes towards prescribing blue light-blocking ophthalmic devices. Ordinal logistic regression analysis was performed to assess the factors that predicted optometrists' prescribing of blue light-blocking lenses. RESULTS: Of 372 respondents, 75.3% indicated prescribing blue light-blocking spectacle lenses in their clinical practice. Forty-four per cent of optometrists considered daily environmental exposure to blue light as a potential cause of retinal damage, and approximately half of respondents thought blue light emitted from computer screens was an important factor in causing computer vision syndrome. About half of optometrists considered placebo effects to potentially play a role, at least sometimes, in patients' experiences with blue light-blocking lenses. Most optometrists estimated that they first prescribed a blue light-blocking lens in 2016. The most common reason optometrists prescribed these devices was for patients who were computer or electronic device users (87.9%). The two main sources of information used to guide practitioners' management approaches were conference presentations and manufacturer product information. Practitioners were significantly more likely to prescribe blue light-blocking lenses if they considered blue light to cause either retinal damage (odds ratio, OR 2.28, 95%CI 1.34-3.88, p = 0.002) or computer vision syndrome (OR 2.52, 95%CI 1.41-4.50, p = 0.002) compared with practitioners who did not consider such factors to be relevant. CONCLUSION: Prescribing trends by Australian optometrists in relation to blue light-blocking lenses reflect the inconclusive nature of several aspects of the evidence in this field. Blue light-blocking lens prescribing has increased since 2010, despite practitioners acknowledging the lack of high-quality evidence to support their use and also commonly believing that placebo effects may have a role in patient responses to these lenses. Information from this study will help inform the development of resources to guide evidence-based prescribing of blue light-blocking lens products.
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ItemOptic nerve tissue displacement during mild intraocular pressure elevation: its relationship to central corneal thickness and corneal hysteresis(WILEY, 2018-07)PURPOSE: To determine the extent to which (1) optic nerve tissue is displaced following mild acute elevation of intraocular pressure, and (2) clinically accessible measures at the anterior eye can be used as a surrogate for such displacements. METHODS: We imaged the optic disc of 21 healthy subjects before and after intraocular pressure (IOP) elevation of ~10 mmHg delivered by ophthalmodynamometry. Steady-state tissue displacement during IOP elevation was assessed axially from OCT data, and laterally from SLO data. Recovery from IOP elevation was assessed by tracking a single vertical B-scan through the cup centre. Anatomical structures were demarcated by three masked clinicians to determine lateral shifts for temporal cup edge and central disc vessels, and axial shifts of disc surface and anterior lamina cribrosa. Spatial maps of deformation were constructed within the demarcated cup and disc to assess within-tissue displacement. Measured displacements were correlated with corneal hysteresis, corneal thickness, and IOP. RESULTS: The temporal cup edge moved more temporally with higher baseline IOP (R2 = 0.33, p = 0.006) and with lesser elevation of IOP (R2 = 0.43, p = 0.001); it moved more superiorly for thinner corneas (R2 = 0.35, p = 0.007). Thinner corneas also produced less within-cup deformation, relative to that of the disc (R2 = 0.39, p = 0.004). Axial displacement of the lamina and lateral displacement of vessels were often substantial (lamina 20 ± 15 μm, range 1-60 μm; vessels 37 ± 25 μm, range 2-102 μm) but did not correlate with measured parameters. Recovery from IOP elevation did not take more than 300-400 ms in any subject. CONCLUSIONS: Mild acute elevation of IOP produces large and rapidly reversible shifts in optic nerve tissue in young, healthy eyes. The resulting degree, direction and spatial distribution of cup movement are associated with IOP status and corneal thickness, but not corneal hysteresis.
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ItemDetecting glaucomatous progression with infrequent visual field testing(WILEY, 2018-03)PURPOSE: Previous work has investigated whether a significant regression slope in the first 2 years for the summary index Mean Deviation (MD) is predictive of rapid (≤-2 dB year-1 ) glaucomatous visual field progression. This work assumed six visual fields were obtained as per management guidelines, but in clinical practice commonly only two or three fields are measured. We used simulation methods to investigate how reducing test frequency influences the prediction of rapid visual field progression, along with the influence of including criteria based on regression slope. METHODS: We simulated visual field series (N = 100 000) spaced annually in the first 2 years and then biennially. We calculated positive and negative predictive values (PPV & NPV) for detecting rapid progression, based on a criterion of a significant negative regression slope of any magnitude, or of a magnitude less than a particular limit. We performed a second simulation using test frequency and disease prevalence parameters from a dataset of 255 glaucoma patients from The University of Tokyo Hospital, to check the validity of our method. RESULTS: Prediction values at 2 years were slightly less than those obtained using six visual fields. An addition of an appropriate slope based criterion materially improved PPV, with little detrimental effect on NPV. Simulated prediction values for the Tokyo dataset were similar to those determined empirically. CONCLUSION: Infrequent visual field testing does not dramatically alter predictive values at 2 years, but does substantially delay when significant progression may first be detected.
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ItemNo Preview AvailableCentral and peripheral motion perception under mesopic conditions in older adults(Association for Research in Vision and Ophthalmology (ARVO), 2020-10-20)
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ItemDifferential aging effects in motion perception tasks for central and peripheral vision(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2020-05)The perception of motion is considered critical for performing everyday tasks, such as locomotion and driving, and relies on different levels of visual processing. However, it is unclear whether healthy aging differentially affects motion processing at specific levels of processing, or whether performance at central and peripheral spatial eccentricities is altered to the same extent. The aim of this study was to explore the effects of aging on hierarchically different components of motion processing: the minimum displacement of dots to perceive motion (Dmin), the minimum contrast and speed to determine the direction of motion, spatial surround suppression of motion, global motion coherence (translational and radial), and biological motion. We measured motion perception in both central vision and at 15° eccentricity, comparing performance in 20 older (60-79 years) and 20 younger (19-34 years) adults. Older adults had significantly elevated thresholds, relative to younger adults, for motion contrast, speed, Dmin, and biological motion. The differences between younger and older participants were of similar magnitude in central and peripheral vision, except for surround suppression of motion, which was weaker in central vision for the older group, but stronger in the periphery. Our findings demonstrate that the effects of aging are not uniform across all motion tasks. Whereas the performance of some tasks in the periphery can be predicted from the results in central vision, the effects of age on surround suppression of motion shows markedly different characteristics between central and peripheral vision.