Effect of ageing on attended visual stimuli in the presence of cognitive mental load.

PURPOSE: This study was designed to compare the effects of mental load, caused by concurrent auditory tasks, on attended and non-attended visual stimuli in older and younger adults. METHODS: Participants performed a visual orientation discrimination task involving two spatially separated Gabor patches of 4 cycles/degree and 55% contrast. Participants received either a valid-cue, invalid-cue or a neutral-cue for the patch whose orientation they were required to determine. An auditory n-back task was performed simultaneously to impose mental load. Repeated-measures ANOVA was used for investigation of main effects and interactions of ageing, mental load and attention condition on orientation discrimination. RESULTS: A total of 27 younger (mean age ± SD, 22.6 ± 1.3 years) and 23 older adults (54.7 ± 4.3 years) participated in the study. There was a significant effect of age (p = 0.01) and mental load (p < 0.001) on the proportion of correct orientation discrimination responses. Attentional condition significantly affected the proportion of correct responses (p = 0.02), but there was no significant interaction between attention, mental load and age group (p = 0.85). There was no overall difference in the proportion of no responses (the proportion of trials in which the participants failed to respond) between the two age groups (p = 0.53) nor on the overall effect of attention on the proportion of no responses (p = 0.25). There was, however, a significant effect of mental load on the proportion of no responses (p = 0.002). CONCLUSION: Although mental load reduced performance equally for both age groups and for all attentional conditions, older adults had poorer overall performance. Therefore, a given mental load is more likely to drive older observers to unacceptable levels of task performance.

Effect of Cognitive Mental Load on Attended and Nonattended Visual Stimuli.

SIGNIFICANCE: In the real word, visual tasks may be concurrent with other activity that imposes mental load. Although the brain's capacity to process information is limited, attention can improve visual performance by selectively allocating processing resources. Therefore, measuring visual performance under such circumstances can reflect patients' vision more accurately. PURPOSE: The aim of this study was to evaluate the effect of nonvisual task-induced mental load on visual performance at both attended and unattended locations in stimulus-driven captured attention. METHODS: Visual function was measured with an orientation discrimination task for Gabor patches with contrasts of 10, 15, 30, 50, and 80%. Three attentional conditions (valid-cue, invalid-cue, and neutral-cue) were randomly interleaved within runs. To modulate mental load, the visual task was performed either with or without a simultaneous auditory n-back task (two-back for maximum mental load and zero-back to control for the effect of having to perform a simultaneous task). RESULTS: Our result showed that the effect of mental load on correct responses was significant ( P = .02). Correct responses decreased significantly during the two-back task when compared with the baseline condition ( P = .03), but there was no significant difference between baseline and zero-back conditions ( P = .06). The effect of attention and spatial frequencies on the percentage of correct responses was significant ( P < .001). There was no significant interaction between mental load and spatial frequency, contrast level, or attention ( P > .05). CONCLUSIONS: Mental load had a similar decreasing effect on attended and unattended visual stimuli. This may be due to a generalized effect on processing resources upstream to where spatial attention is allocated.

Is critical flicker-fusion frequency a valid measure of visual fatigue? A post-hoc analysis of a double-masked randomised controlled trial.

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.

The relationship between central and mid-peripheral motion perception and the hazard perception test in younger and older adults.

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.

Does vision therapy for visual information processing improve academic performance? A randomised clinical trial.

PURPOSE: To determine whether a typical vision therapy (VT) programme designed to improve visual information processing (VIP) skills is effective in improving these skills and/or academic performance. METHODS: We used a double-blind, randomised clinical trial to compare VIP VT to placebo training. Participating schools referred a sample of 579 early primary school children identified as being within the lower third of their class for literacy. From the referred sample, we identified 247 children eligible to participate (passed visions and auditory processing screening, and VIP performance <34th percentile), 94 of whom participated. Matching IQ, school grade and sex was achieved by sorting hierarchically on these values and then alternately allocating to VT or placebo groups. Both programmes ran for 10 weeks and consisted of 33 h working at home and 4 h working in office. The VT programme was indicative of that employed in Australian paediatric optometry practices, with the placebo programme containing similar activities, except targeting skills within a child's competencies and with specific VIP development activities removed. The main outcome measures were score change on three standardised educational tests (reading comprehension, spelling and mathematics) and six VIP tests, both immediately post-intervention (PI) and 6 months later. RESULTS: Sixty-nine children completed the programmes. The VT programme produced no significant improvement in the three educational tests or in five of the six VIP tests compared to the control. The VT programme improved visual sequential memory (VSM) by a moderate amount compared to the control (Cohen's d = 0.57 and 0.52, immediately PI and at 6 months, respectively: p < 0.03 and p < 0.02). CONCLUSIONS: The VIP and academic performance benefits from a VT programme were largely identical to those from a control programme, both immediately and 6-month PI. Placebo effects and general effects such as improvements in executive function and/or regression-to-the-mean could be mistaken for specific programme effectiveness.

More than words: Neurophysiological correlates of semantic dissimilarity depend on comprehension of the speech narrative.

Speech comprehension relies on the ability to understand words within a coherent context. Recent studies have attempted to obtain electrophysiological indices of this process by modelling how brain activity is affected by a word's semantic dissimilarity to preceding words. Although the resulting indices appear robust and are strongly modulated by attention, it remains possible that, rather than capturing the contextual understanding of words, they may actually reflect word-to-word changes in semantic content without the need for a narrative-level understanding on the part of the listener. To test this, we recorded electroencephalography from subjects who listened to speech presented in either its original, narrative form, or after scrambling the word order by varying amounts. This manipulation affected the ability of subjects to comprehend the speech narrative but not the ability to recognise individual words. Neural indices of semantic understanding and low-level acoustic processing were derived for each scrambling condition using the temporal response function. Signatures of semantic processing were observed when speech was unscrambled or minimally scrambled and subjects understood the speech. The same markers were absent for higher scrambling levels as speech comprehension dropped. In contrast, word recognition remained high and neural measures related to envelope tracking did not vary significantly across scrambling conditions. This supports the previous claim that electrophysiological indices based on the semantic dissimilarity of words to their context reflect a listener's understanding of those words relative to that context. It also highlights the relative insensitivity of neural measures of low-level speech processing to speech comprehension.

Interventions for the Management of Computer Vision Syndrome: A Systematic Review and Meta-analysis.

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.

The effect of mental load on psychophysical and visual evoked potential visual acuity.

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.

Investigating the discrepancy between MAIA and MP-1 microperimetry results.

PURPOSE: Previous work has suggested that sensitivities measured on the iCare MAIA and Nidek MP-1 microperimeters differ systematically, although it is unclear whether one or both devices are inaccurate. Here, we assess the discrepancy between these two instruments as well as with a rigorous reference standard. METHODS: Fifteen healthy participants underwent visual field testing on the MAIA and MP-1 microperimeters. Results were compared to a reference measure of increment thresholds on a laboratory-based, calibrated computer monitor system using the same background luminance and target size. Discrepancies were assessed as a function of eccentricity along the vertical meridian. Differences in decibels (dB) due to differences in the maximum stimulus luminance between devices were accounted for mathematically. RESULTS: The mean sensitivity measured with the MAIA was <1 dB lower than laboratory-based measures, which was statistically significant but of limited clinical importance. In contrast, the mean sensitivity measured with the MP-1 was >8 dB lower than the laboratory measures. The difference was greater for an eccentric superior retinal location, in contrast to what would be predicted if the discrepancy was due to a ceiling effect caused by the MP-1's limited dynamic range. CONCLUSIONS: While MAIA measurements showed low bias compared with our rigorously determined reference standard, the MP-1 showed large discrepancies that could not be explained purely by the limited dynamic range of the instrument. MAIA and MP-1 sensitivity values cannot be compared directly, and caution is advised when assessing absolute sensitivities or eccentricity effects in the extensive MP-1 literature.

Motion perception at mesopic light levels: effects of physiological ageing and eccentricity.

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.

Semantic Context Enhances the Early Auditory Encoding of Natural Speech.

Speech perception involves the integration of sensory input with expectations based on the context of that speech. Much debate surrounds the issue of whether or not prior knowledge feeds back to affect early auditory encoding in the lower levels of the speech processing hierarchy, or whether perception can be best explained as a purely feedforward process. Although there has been compelling evidence on both sides of this debate, experiments involving naturalistic speech stimuli to address these questions have been lacking. Here, we use a recently introduced method for quantifying the semantic context of speech and relate it to a commonly used method for indexing low-level auditory encoding of speech. The relationship between these measures is taken to be an indication of how semantic context leading up to a word influences how its low-level acoustic and phonetic features are processed. We record EEG from human participants (both male and female) listening to continuous natural speech and find that the early cortical tracking of a word's speech envelope is enhanced by its semantic similarity to its sentential context. Using a forward modeling approach, we find that prediction accuracy of the EEG signal also shows the same effect. Furthermore, this effect shows distinct temporal patterns of correlation depending on the type of speech input representation (acoustic or phonological) used for the model, implicating a top-down propagation of information through the processing hierarchy. These results suggest a mechanism that links top-down prior information with the early cortical entrainment of words in natural, continuous speech.SIGNIFICANCE STATEMENT During natural speech comprehension, we use semantic context when processing information about new incoming words. However, precisely how the neural processing of bottom-up sensory information is affected by top-down context-based predictions remains controversial. We address this discussion using a novel approach that indexes a word's similarity to context and how well a word's acoustic and phonetic features are processed by the brain at the time of its utterance. We relate these two measures and show that lower-level auditory tracking of speech improves for words that are more related to their preceding context. These results suggest a mechanism that links top-down prior information with bottom-up sensory processing in the context of natural, narrative speech listening.

Differential aging effects in motion perception tasks for central and peripheral vision.

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.

Insights into Australian optometrists' knowledge and attitude towards prescribing blue light-blocking ophthalmic devices.

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.

The influence of retinal image motion on the perceptual grouping of temporally asynchronous stimuli.

Briefly presented stimuli can reveal the lower limit of retinal-based perceptual stabilization mechanisms. This is demonstrated in perceptual grouping of temporally asynchronous stimuli, in which alternate row or column elements of a regular grid are presented over two successive display frames with an imperceptible temporal offset. The grouping phenomenon results from a subtle shift between alternate grid elements due to incomplete compensation of small, fixational eye movements occurring between the two presentation frames. This suggests that larger retinal shifts should amplify the introduced shifts between alternate grid elements and improve grouping performance. However, large shifts are necessarily absent in small eye movements. Furthermore, shifts follow a random walk, making the relationship between shift magnitude and performance difficult to explore systematically. Here, we established a systematic relationship between retinal image motion and perceptual grouping by presenting alternate grid elements (untracked) during smooth pursuit of known velocities. Our results show grouping performance to improve in direct proportion to pursuit velocity. Any potential compensation by extraretinal signals (e.g., efference copy) does not seem to occur.

Detecting glaucomatous progression with infrequent visual field testing.

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.

Optic nerve tissue displacement during mild intraocular pressure elevation: its relationship to central corneal thickness and corneal hysteresis.

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.

Can Home Monitoring Allow Earlier Detection of Rapid Visual Field Progression in Glaucoma?

PURPOSE: Recent developments in electronic technology are making it possible to home monitor the sensitivity of the central visual field using portable devices. We used simulations to investigate whether the higher test frequency afforded by home monitoring improves the early detection of rapid visual field loss in glaucoma and how any benefits might be affected by imperfect compliance or increased variability in the home-monitoring test. DESIGN: Computer simulation, with parameter selection confirmed with a cohort study. PARTICIPANTS: A total of 43 patients with treated glaucoma (both open-angle and closed-angle), ocular hypertension or glaucoma suspects (mean age, 71 years; range, 37-89 years), were followed in the cohort study. METHODS: We simulated series (n = 100 000) of visual fields for patients with stable glaucoma and patients with progressing glaucoma for 2 in-clinic (yearly and 6-monthly) and 3 home-monitoring (monthly, fortnightly, and weekly) schedules, each running over a 5-year period. Various percentages of home-monitored fields were omitted at random to simulate reduced compliance, and the variability of the home monitored fields also was manipulated. We used previously published variability characteristics for perimetry and confirmed their appropriateness for a home-monitoring device by measuring the device's retest variability at 2 months in a cohort of 43 patients. The criterion for flagging progression in our simulation was a significant slope of the ordinary least squares regression of a simulated patient's mean deviation (MD) data. MAIN OUTCOME MEASURES: The sensitivity for identifying rapid visual field loss (-2 decibels [dB]/year loss of MD). RESULTS: Although a sensitivity of 0.8 for rapid field loss was achieved after 2.5 years of 6-monthly testing in the clinic, weekly home monitoring achieved this by 0.9 years despite moderate test compliance of 63%. The improved performance of weekly home monitoring over 6-monthly clinical testing was retained even when home monitoring was assumed to produce more variable test results or be associated with low patient compliance. CONCLUSIONS: Detecting rapid visual field progression may be improved using a home-monitoring strategy, even when compliance is imperfect. The cost-benefit of such an approach is yet to be demonstrated, however.

Semantic Structural Alignment of Neural Representational Spaces Enables Translation between English and Chinese Words.

Two sets of items can share the same underlying conceptual structure, while appearing unrelated at a surface level. Humans excel at recognizing and using alignments between such underlying structures in many domains of cognition, most notably in analogical reasoning. Here we show that structural alignment reveals how different people's neural representations of word meaning are preserved across different languages, such that patterns of brain activation can be used to translate words from one language to another. Groups of Chinese and English speakers underwent fMRI scanning while reading words in their respective native languages. Simply by aligning structures representing the two groups' neural semantic spaces, we successfully infer all seven Chinese-English word translations. Beyond language translation, conceptual structural alignment underlies many aspects of high-level cognition, and this work opens the door to deriving many such alignments directly from neural representational content.

The retest distribution of the visual field summary index mean deviation is close to normal.

PURPOSE: When modelling optimum strategies for how best to determine visual field progression in glaucoma, it is commonly assumed that the summary index mean deviation (MD) is normally distributed on repeated testing. Here we tested whether this assumption is correct. METHODS: We obtained 42 reliable 24-2 Humphrey Field Analyzer SITA standard visual fields from one eye of each of five healthy young observers, with the first two fields excluded from analysis. Previous work has shown that although MD variability is higher in glaucoma, the shape of the MD distribution is similar to that found in normal visual fields. A Shapiro-Wilks test determined any deviation from normality. Kurtosis values for the distributions were also calculated. RESULTS: Data from each observer passed the Shapiro-Wilks normality test. Bootstrapped 95% confidence intervals for kurtosis encompassed the value for a normal distribution in four of five observers. When examined with quantile-quantile plots, distributions were close to normal and showed no consistent deviations across observers. CONCLUSIONS: The retest distribution of MD is not significantly different from normal in healthy observers, and so is likely also normally distributed - or nearly so - in those with glaucoma. Our results increase our confidence in the results of influential modelling studies where a normal distribution for MD was assumed.