Optometry and Vision Sciences - Research Publications
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ItemWriting an Introduction to a scientific paper(WILEY, 2023-01)
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ItemNo Preview AvailableThe relationship between central and mid-peripheral motion perception and the hazard perception test in younger and older adults(WILEY, 2023-09)INTRODUCTION: Vision standards for driving are typically based on visual acuity, despite evidence that it is a poor predictor of driving safety and performance. However, visual motion perception is potentially relevant for driving, as the vehicle and surroundings are in motion. This study explored whether tests of central and mid-peripheral motion perception better predict performance on a hazard perception test (HPT), which is related to driving performance and crash risk, than visual acuity. Additionally, we explored whether age influences these associations, as healthy ageing impairs performance on some motion sensitivity tests. METHODS: Sixty-five visually healthy drivers (35 younger, mean age: 25.5; SD 4.3 years; 30 older adults, mean age: 71.0; SD 5.4 years) underwent a computer-based HPT, plus four different motion sensitivity tests both centrally and at 15° eccentricity. Motion tests included minimum displacement to identify motion direction (Dmin ), contrast detection threshold for a drifting Gabor (motion contrast), coherence threshold for a translational global motion stimulus and direction discrimination for a biological motion stimulus in the presence of noise. RESULTS: Overall, HPT reaction times were not significantly different between age groups (p = 0.40) nor were maximum HPT reaction times (p = 0.34). HPT response time was associated with motion contrast and Dmin centrally (r = 0.30, p = 0.02 and r = 0.28, p = 0.02, respectively) and with Dmin peripherally (r = 0.34, p = 0.005); these associations were not affected by age group. There was no significant association between binocular visual acuity and HPT response times (r = 0.02, p = 0.29). CONCLUSIONS: Some measures of motion sensitivity in central and mid-peripheral vision were associated with HPT response times, whereas binocular visual acuity was not. Peripheral testing did not show an advantage over central testing for visually healthy older drivers. Our findings add to the growing body of evidence that the ability to detect small motion changes may have potential to identify unsafe road users.
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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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ItemIs critical flicker-fusion frequency a valid measure of visual fatigue? A post-hoc analysis of a double-masked randomised controlled trial(WILEY, 2023-03)PURPOSE: Critical flicker-fusion frequency (CFF) has been used in clinical studies as a measure of visual fatigue. We examine the correlation between CFF and subjective reports of visual fatigue in a group of symptomatic computer users, to consider whether CFF may be used as a surrogate measure of visual fatigue symptoms. METHODS: We analysed data from a previous randomised controlled trial. One hundred and twenty adults, diagnosed with computer vision syndrome, had CFF and visual fatigue symptoms quantified before and after a visually demanding 2-h computer task. Symptoms were assessed using a questionnaire with nine subcomponents that summed to a total score of 900. CFF was measured using a two-interval forced-choice method, with the flicker rate altered by a computer-controlled staircase procedure. For our primary analysis, we determined Spearman correlation coefficients between post-task symptom scores and CFF, and between change from baseline symptom scores and CFF. We also used a bootstrap procedure to consider whether symptom score subcomponents were significantly (Bonferroni-corrected) different from overall scores with regard to their correlations with CFF. RESULTS: Although visual fatigue symptom scores altered significantly post-task (mean change: 92 units; 95% confidence interval [CI]: 11 to 122), CFF did not (mean change -0.7 Hz; 95% CI: -1.7 to 0.3). There was no significant correlation between overall symptom scores and CFF, either for the post-task (r = -0.13; 95% CI: -0.31 to 0.05) or the change from baseline (r = -0.18; 95% CI: -0.35 to 0.01) analysis. Subcomponents of the symptom questionnaire did not show a significant correlation with CFF, either for the post-task or the change from baseline analysis. CONCLUSIONS: We find that CFF is not a useful surrogate for symptoms of visual fatigue, given its low correlation with scores on a visual fatigue symptom questionnaire.
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ItemAssociation between systemic omega-3 polyunsaturated fatty acid levels, and corneal nerve structure and function(SPRINGERNATURE, 2023-06)BACKGROUND: Omega-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have anti-inflammatory and neuroprotective properties. This study sought to determine the relationship between corneal parameters and systemic omega-3 fatty acid levels. METHODS: Forty-seven participants with no/mild peripheral neuropathy (26 with diabetes and 21 without) underwent comprehensive ocular surface and systemic PUFA assessments. Corneal anatomical parameters were assessed using in vivo confocal microscopy. Corneal sensitivity was measured using non-contact esthesiometry. Relationships between systemic PUFA levels and corneal parameters were evaluated with multiple linear regression, adjusted for age, sex, neuropathy symptom score, and presence of diabetes and dry eye disease. The relationship between corneal nerve fibre length (CNFL) and corneal sensitivity threshold was evaluated. RESULTS: The median Omega-3 Index, a measure of erythrocyte EPA and DHA, was 5.21% (interquartile range: 4.44-5.94%) in the study population. Mean ( ± SD) CNFL was 13.53 ± 3.37 mm/mm2. Multiple linear regression showed that Omega-3 Index (β = 0.33; p = 0.02), age (β = -0.46; p = 0.001) and diabetes (β = -0.30; p = 0.03) were independently associated with CNFL (R2 = 0.39, p = 0.002). In a separate model, DHA (β = 0.32; p = 0.027) and age (β = -0.41; p = 0.003) were associated with CNFL (R2 = 0.37, p = 0.003). Neither systemic EPA nor omega-6 fatty acid levels correlated with CNFL. There was no association between PUFA levels and corneal sensitivity or corneal immune cell density. A negative correlation was found between CNFL and corneal sensation thresholds to a cooled stimulus in diabetes participants, in the central (ρ = -0.50; p = 0.009) and peripheral (ρ = -0.50; p = 0.01) cornea. CONCLUSIONS: A positive relationship between the systemic Omega-3 Index and corneal nerve parameters suggests omega-3 PUFA intake may influence corneal nerve architecture.
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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.