The origins and development of aesthetics.

All people (and some other animals) have aesthetic responses to sensory stimulation, responses of emotional pleasure or displeasure. These emotions vary from one person and culture to another, yet they share a common mechanism. To survive, an adaptive animal (as opposed to a tropic animal) needs to become comfortable with normality and to have slight abnormalities draw attention to themselves. Walking through a jungle you need to notice a tiger from a single stripe: if you must wait to see the whole animal, you are unlikely to survive. In Homo sapiens, the brain's adaptive neurochemistry does this naturally, partly because the brain's neuronal networks are structured to react efficiently to fractal structures, structures that shape much of nature. In addition, previous associations may turn a slight variation from normal into feelings of either pleasure or danger. The details of these responses-what is normal and what variations feel like-will depend upon an individual's experience, but the mechanism is the same, no matter whether a person is tasting a wine, seeing a face or landscape, or hearing a song. This article is part of the theme issue 'Sensing and feeling: an integrative approach to sensory processing and emotional experience'.

Continued care and provision of glasses are necessary to improve visual and academic outcomes in children: Experience from a cluster-randomized controlled trial of school-based vision screening.

OBJECTIVE: To assess the effectiveness of a kindergarten vision screening program by randomly assigning schools to receive or not receive vision screening, then following up 1.5 years later. METHODS: Fifty high-needs elementary schools were randomly assigned to participate or not in a vision screening program for children in senior kindergarten (SK; age 5‒6 years). When the children were in Grade 2 (age 6‒7 years), vision screening was conducted at all 50 schools. RESULTS: Contrary to expectations, screened and non-screened schools did not differ in the prevalence of suspected amblyopia in Grade 2 (8.6% vs. 7.5%, p = 0.10), nor prevalence of other visual problems such as astigmatism (45.1% vs. 47.1%, p = 0.51). There was also no difference between screened and non-screened schools in academic outcomes such as the proportion of children below grade level in reading (33% vs. 29%) or math (44% vs. 38%) (p = 0.86). However, more children were wearing glasses in screened than in non-screened schools (10.2% vs. 7.8%, p = 0.05), and more children reported their glasses as missing or broken (8.3% vs. 4.7%, p = 0.01), suggesting that SK screening had identified successfully those in need of glasses. Examination of individual results revealed that 72% of children diagnosed and treated for amblyopia in SK no longer had amblyopia in Grade 2. CONCLUSION: The prevalence of amblyopia and other visual problems was not reduced in Grade 2 by our SK vision screening program, perhaps because of poor treatment compliance and high attrition. The results suggest that a single screening intervention is insufficient to reduce visual problems among young children. However, the data from individuals with amblyopia suggest that continuing vision care and access to glasses benefits children, especially children from lower socioeconomic class.

RéSUMé: OBJECTIF: Évaluer l'efficacité d'un programme de dépistage visuel à l'école maternelle (EM) en assignant aléatoirement des écoles à participer ou non à un tel programme, puis en faisant un suivi un an et demi après. MéTHODES: Cinquante écoles primaires pour étudiants et étudiantes ayant des besoins importants ont été assignées aléatoirement à participer ou non à un programme de dépistage visuel auprès des enfants fréquentant la maternelle (EM; 5‒6 ans). Lorsque ces enfants étaient en 2e année (6‒7 ans), un dépistage visuel a été effectué dans les 50 écoles. RéSULTATS: Contre toute attente, il n'y a pas eu de différence entre les écoles ayant participé ou non au dépistage dans la prévalence de l'amblyopie présumée en 2e année (8,6 % contre 7,5 %, p = 0,10), ni dans la prévalence d'autres problèmes de vision comme l'astigmatisme (45,1 % contre 47,1 %, p = 0,51). Il n'y a pas eu non plus de différence dans les résultats scolaires des deux groupes d'écoles, comme la proportion d'enfants dont le niveau en lecture (33 % contre 29 %) ou en mathématiques (44 % contre 38 %), p = 0,86, ne correspondait pas à leur année d'étude. Cependant, le nombre d'enfants portant des lunettes était plus élevé dans les écoles ayant participé au dépistage que dans les autres écoles (10,2 % contre 7,8 %, p = 0,05), ainsi que le nombre d'enfants disant avoir perdu ou brisé leurs lunettes (8,3 % contre 4,7 %, p = 0,01), ce qui indique que le dépistage en maternelle a identifié avec succès les enfants ayant besoin de lunettes. L'examen des résultats individuels a révélé que 72 % des enfants diagnostiqués et traités pour l'amblyopie en maternelle ne présentaient plus d'amblyopie en 2e année. CONCLUSION: Notre programme de dépistage visuel à l'école maternelle n'a pas réduit la prévalence de l'amblyopie et d'autres problèmes de vision en 2e année, peut-être en raison du manque d'assiduité au traitement et d'une attrition importante. Les résultats indiquent qu'une seule intervention de dépistage ne suffit pas à réduire les problèmes de vision chez les jeunes enfants. Cependant, les données individuelles des sujets présentant une amblyopie indiquent qu'il est avantageux pour les enfants, et surtout ceux de la classe socioéconomique inférieure, de continuer de recevoir des soins de la vue et d'avoir accès à des lunettes.

Developmental changes in audiotactile event perception.

The fission and fusion illusions provide measures of multisensory integration. The sound-induced tap fission illusion occurs when a tap is paired with two distractor sounds, resulting in the perception of two taps; the sound-induced tap fusion illusion occurs when two taps are paired with a single sound, resulting in the perception of a single tap. Using these illusions, we measured integration in three groups of children (9-, 11-, and 13-year-olds) and compared them with a group of adults. Based on accuracy, we derived a measure of magnitude of illusion and used a signal detection analysis to estimate perceptual discriminability and decisional criterion. All age groups showed a significant fission illusion, whereas only the three groups of children showed a significant fusion illusion. When compared with adults, the 9-year-olds showed larger fission and fusion illusions (i.e., reduced discriminability and greater bias), whereas the 11-year-olds were adult-like for fission but showed some differences for fusion: significantly worse discriminability and marginally greater magnitude and criterion. The 13-year-olds were adult-like on all measures. Based on the pattern of data, we speculate that the developmental trajectories for fission and fusion differ. We discuss these developmental results in the context of three non-mutually exclusive theoretical frameworks: sensory dominance, maximum likelihood estimation, and causal inference.

Cost-effectiveness of Universal School- and Community-Based Vision Testing Strategies to Detect Amblyopia in Children in Ontario, Canada.

Importance: Screening for amblyopia in primary care visits is recommended for young children, yet screening rates are poor. Although the prevalence of amblyopia is low (3%-5%) among young children, universal screening in schools and mandatory optometric examinations may improve vision care, but the cost-effectiveness of these vision testing strategies compared with the standard in primary care is unknown. Objective: To evaluate the relative cost-effectiveness of universal school screening and mandated optometric examinations compared with standard care vision screening in primary care visits in Toronto, Canada, with the aim of detecting and facilitating treatment of amblyopia and amblyopia risk factors from the Ontario government's perspective. Design, Setting, and Participants: An economic evaluation was conducted from July 2019 to May 2021 using a Markov model to compare 15-year costs and quality-adjusted life-years (QALYs) between school screening and optometric examination compared with primary care screening in Toronto, Canada. Parameters were derived from published literature, the Ontario Schedule of Benefits and Fees, and the Kindergarten Vision Testing Program. A hypothetical cohort of 25 000 children aged 3 to 5 years was simulated. It was assumed that children in the cohort had irreversible vision impairment if not diagnosed by an optometrist. In addition, incremental costs and outcomes of 0 were adjusted to favor the reference strategy. Vision testing programs were designed to detect amblyopia and amblyopia risk factors. Main Outcomes and Measures: For each strategy, the mean costs per child included the costs of screening, optometric examinations, and treatment. The mean health benefits (QALYs) gained were informed by the presence of vision impairment and the benefits of treatment. Incremental cost-effectiveness ratios were calculated for each alternative strategy relative to the standard primary care screening strategy as the additional cost required to achieve an additional QALY at a willingness-to-pay threshold of $50 000 Canadian dollars (CAD) ($37 690) per QALY gained. Results: School screening relative to primary care screening yielded cost savings of CAD $84.09 (95% CI, CAD $82.22-$85.95) (US $63.38 [95% CI, US $61.97-$64.78]) per child and an incremental gain of 0.0004 (95% CI, -0.0047 to 0.0055) QALYs per child. Optometric examinations relative to primary care screening yielded cost savings of CAD $74.47 (95% CI, CAD $72.90-$76.03) (US $56.13 [95% CI, $54.95-$57.30]) per child and an incremental gain of 0.0508 (95% CI, 0.0455-0.0561) QALYs per child. At a willingness-to-pay threshold of CAD $50 000 (US $37 690) per QALY gained, school screening and optometric examinations were cost-effective relative to primary care screening in only 20% and 29% of iterations, respectively. Conclusions and Relevance: In this study, because amblyopia prevalence is low among young children and most children in the hypothetical cohort had healthy vision, universal school screening and optometric examinations were not cost-effective relative to primary care screening for detecting amblyopia in young children in Toronto, Canada. The mean added health benefits of school screening and optometric examinations compared with primary care screening did not warrant the resources used.

The development of audio-visual temporal precision precedes its rapid recalibration.

Through development, multisensory systems reach a balance between stability and flexibility: the systems integrate optimally cross-modal signals from the same events, while remaining adaptive to environmental changes. Is continuous intersensory recalibration required to shape optimal integration mechanisms, or does multisensory integration develop prior to recalibration? Here, we examined the development of multisensory integration and rapid recalibration in the temporal domain by re-analyzing published datasets for audio-visual, audio-tactile, and visual-tactile combinations. Results showed that children reach an adult level of precision in audio-visual simultaneity perception and show the first sign of rapid recalibration at 9 years of age. In contrast, there was very weak rapid recalibration for other cross-modal combinations at all ages, even when adult levels of temporal precision had developed. Thus, the development of audio-visual rapid recalibration appears to require the maturation of temporal precision. It may serve to accommodate distance-dependent travel time differences between light and sound.

Critical Periods in Vision Revisited.

For four decades, investigations of the biological basis of critical periods in the developing mammalian visual cortex were dominated by study of the consequences of altered early visual experience in cats and nonhuman primates. The neural deficits thus revealed also provided insight into the origin and neural basis of human amblyopia that in turn motivated additional studies of humans with abnormal early visual input. Recent human studies point to deficits arising from alterations in all visual cortical areas and even in nonvisual cortical regions. As the new human data accumulated in parallel with a near-complete shift toward the use of rodent animal models for the study of neural mechanisms, it is now essential to review the human data and the earlier animal data obtained from cats and monkeys to infer general conclusions and to optimize future choice of the most appropriate animal model.

Socioeconomic Status and Vision Care Services in Ontario, Canada: A Population-Based Cohort Study.

OBJECTIVE: To test the association of material deprivation and the utilization of vision care services for young children. STUDY DESIGN: We conducted a population-based, repeated measures cohort study using linked health and administrative datasets. All children born in Ontario in 2010 eligible for provincial health insurance were followed from birth until their seventh birthday. The main exposure was neighborhood-level material deprivation quintile, a proxy for socioeconomic status. The primary outcome was receipt of a comprehensive eye examination (not to include a vision screening) by age 7 years from an eye care professional, or family physician. RESULTS: Of 128 091 children included, female children represented 48.7% of the cohort, 74.4% lived in major urban areas, and 16.2% lived in families receiving income assistance. Only 65% (n = 82 833) had at least 1 comprehensive eye examination, with the lowest uptake (56.9%; n = 31 911) in the most deprived and the highest uptake (70.5%; n =19 860) in the least deprived quintiles. After adjusting for clinical and demographic variables, children living in the least materially deprived quintile had a higher odds of receiving a comprehensive eye examination (aOR 1.43; 95% CI 1.36, 1.51) compared with children in the most materially deprived areas. CONCLUSIONS: Uptake of comprehensive eye examinations is poor, especially for children living in the most materially deprived neighborhoods. Strategies to improve uptake and reduce inequities are warranted.

Economic evaluations of vision screening to detect amblyopia and refractive errors in children: a systematic review.

OBJECTIVE: To synthesize and appraise economic evaluations of vision screening to detect vision impairment in children. METHODS: Literature searches were conducted on seven electronic databases, grey literature, and websites of agencies conducting health technology assessments. Studies were included if they (1) were full, comparative economic evaluations that used cost-utility, cost-benefit, cost-effectiveness, cost-consequence, or cost-analysis methods; (2) described screening services designed to detect amblyopia, strabismus, or uncorrected refractive errors in children under 6 years of age; and (3) published after 1994. High-quality studies were synthesized descriptively. Currencies were reported in 2019 Canadian dollars. Quality was assessed with the Pediatric Quality Appraisal Questionnaire (PQAQ). RESULTS: Vision screening services were conducted by paid staff, volunteers, or health care professionals in schools or clinics. Thirteen studies were published from five countries: China (n = 1), United States (n = 4), United Kingdom (n = 1), Canada (n = 1), and Germany (n = 6). Analytical techniques included cost-utility/cost-effectiveness combination (n = 2), cost-effectiveness analysis (n = 7), cost-utility analysis (n = 1), cost-benefit analysis (n = 1), cost-consequence analysis (n = 1), and cost analysis (n = 1). Incremental cost-effectiveness ratios ranged from C$1,056 to C$151,274 per additional case detected/prevented and from C$9,429 to C$30,254,703 per additional QALY gained, depending on the type of screening service and comparator. Six studies were determined to be of high quality. CONCLUSION: Vision screening to detect amblyopia for young children may be cost-effective compared with no screening if amblyopia reduced quality of life. Studies varied significantly in the type of screening services and comparators used. Methodological limitations were common. Future studies would be aided immensely by prospective studies on the impact of amblyopia on the health-related quality of life of young children and guidelines on the effective conduct of vision screening.

RéSUMé: OBJECTIF: Synthétiser et évaluer des évaluations économiques de dépistages visuels visant à détecter la déficience visuelle chez les enfants. MéTHODE: Nous avons interrogé sept bases de données électroniques, la littérature grise et les sites Web d'organismes effectuant des évaluations des technologies de la santé. Nous avons inclus les études correspondant aux critères suivants : (1) évaluations économiques comparatives exhaustives utilisant l'analyse coûts-utilité, coûts-bénéfices, coûts-efficacité ou coûts-conséquences ou l'analyse des coûts; (2) décrivant des services de dépistage visant à détecter l'amblyopie, le strabisme ou les anomalies de la réfraction non corrigées chez les enfants de moins de six ans; et (3) publiées après 1994. Nous avons fait la synthèse descriptive des études de haute qualité. Les devises ont été converties en dollars canadiens de 2019. Nous avons évalué la qualité des études à l'aide de l'outil PQAQ (Pediatric Quality Appraisal Questionnaire). RéSULTATS: Les services de dépistage visuel étaient offerts par du personnel rémunéré, des bénévoles ou des professionnels de santé dans des écoles ou des cliniques. Treize études ont été publiées dans cinq pays : Chine (n = 1), États-Unis (n = 4), Royaume-Uni (n = 1), Canada (n = 1) et Allemagne (n = 6). Les techniques d'analyse employées étaient la combinaison analyse coûts-utilité/analyse coûts-efficacité (n = 2), l'analyse coûts-efficacité (n = 7), l'analyse coûts-utilité (n = 1), l'analyse coûts-avantages (n = 1), l'analyse coûts-conséquences (n = 1) et l'analyse des coûts (n = 1). Les rapports coût-efficacité différentiels s'échelonnaient entre 1 056 $ CA et 151 274 $ CA par cas supplémentaire détecté/prévenu et entre 9 429 $ CA et 30 254 703 $ CA par année de vie pondérée par la qualité (AVPQ) supplémentaire gagnée, selon le type de service de dépistage et le comparateur. Six études ont été jugées être de haute qualité. CONCLUSION: Comparativement à l'absence de dépistage, les dépistages visuels pour détecter l'amblyopie chez les jeunes enfants peuvent être efficaces par rapport à leur coût lorsque l'amblyopie réduit la qualité de vie. Le type de services de dépistage et les comparateurs utilisés variaient considérablement d'une étude à l'autre. Les contraintes méthodologiques étaient courantes. Les études futures seraient grandement favorisées par des études prospectives des incidences de l'amblyopie sur la qualité de vie liée à la santé chez les jeunes enfants et par des lignes directrices sur l'exécution efficace des dépistages visuels.

Brief Postnatal Visual Deprivation Triggers Long-Lasting Interactive Structural and Functional Reorganization of the Human Cortex.

Patients treated for bilateral congenital cataracts provide a unique model to test the role of early visual input in shaping the development of the human cortex. Previous studies showed that brief early visual deprivation triggers long-lasting changes in the human visual cortex. However, it remains unknown if such changes interact with the development of other parts of the cortex. With high-resolution structural and resting-state fMRI images, we found changes in cortical thickness within, but not limited to, the visual cortex in adult patients, who experienced transient visual deprivation early in life as a result of congenital cataracts. Importantly, the covariation of cortical thickness across regions was also altered in the patients. The areas with altered cortical thickness in patients also showed differences in functional connectivity between patients and normally sighted controls. Together, the current findings suggest an impact of early visual deprivation on the interactive development of the human cortex.

Feasibility of a school-based vision screening program to detect undiagnosed visual problems in kindergarten children in Ontario.

BACKGROUND: Visual problems can negatively affect visual development and learning but often go undetected. We assessed the feasibility of scaling up a school-based screening program to identify and treat kindergarten children with visual problems. METHODS: We conducted a prospective cohort study offering vision screening to junior (JK) and senior kindergarten (SK) children attending 43 schools in 15 Ontario communities. Screening comprised photoscreeners and tests of visual acuity, stereoacuity and eye alignment. Children who failed any test were referred for a comprehensive eye examination, with treatment as needed (e.g., glasses). RESULTS: Using a passive consent model, 89% of children were screened compared with 62% using an active consent model (p < 0.001). Referral rates to an optometrist varied across schools (mean referral rate for children in JK 53%, range 25%-83%; mean referral rate for children in SK 34%, range 12%-61%). Among 4811 children who were screened, a visual problem was detected in 516 (10.7%), including 164 (3.4%) with amblyopia and 324 (6.7%) with clinically significant refractive errors. For 347 (67.2%) of the children with a visual problem, this was their first eye examination. Rescreening in Year 2 did not lead to detection of additional problems among children who passed screening in Year 1. Regardless of location (child's school or optometrist's office), 1563 (68.9%) of children attended the follow-up optometry examination. Most of the children who were surveyed (291 of 322, 90.4%) indicated that they enjoyed vision screening. INTERPRETATION: Many children in Ontario with a visual problem were not being identified by the status quo in 2015-2017. We found that in-school vision screening with follow-up eye examinations is an effective strategy for identifying at-risk children and placing them in eye care before grade 1.

Reduced perceptual narrowing in synesthesia.

Synesthesia is a neurologic trait in which specific inducers, such as sounds, automatically elicit additional idiosyncratic percepts, such as color (thus "colored hearing"). One explanation for this trait-and the one tested here-is that synesthesia results from unusually weak pruning of cortical synaptic hyperconnectivity during early perceptual development. We tested the prediction from this hypothesis that synesthetes would be superior at making discriminations from nonnative categories that are normally weakened by experience-dependent pruning during a critical period early in development-namely, discrimination among nonnative phonemes (Hindi retroflex /d̪a/ and dental /ɖa/), among chimpanzee faces, and among inverted human faces. Like the superiority of 6-mo-old infants over older infants, the synesthetic groups were significantly better than control groups at making all the nonnative discriminations across five samples and three testing sites. The consistent superiority of the synesthetic groups in making discriminations that are normally eliminated during infancy suggests that residual cortical connectivity in synesthesia supports changes in perception that extend beyond the specific synesthetic percepts, consistent with the incomplete pruning hypothesis.

Visual configural processing in adults born at extremely low birth weight.

Being born at extremely low birth weight (ELBW; ≤1,000 g) is associated with enduring visual impairments. We tested for long-term, higher order visual processing problems in the oldest known prospectively followed cohort of ELBW survivors. Configural processing (spacing among features of an object) was examined in 62 adults born at ELBW (Mage  = 31.9 years) and 82 adults born at normal birth weight (NBW; ≥2,500 g: Mage  = 32.5 years). Pairs of human faces, monkey faces, or houses were presented in a delayed match-to-sample task, where non-matching stimuli differed only in the spacing of their features. Discrimination accuracy for each stimulus type was compared between birth weight groups, adjusting for neurosensory impairment, visual acuity, binocular fusion ability, IQ, and sex. Both groups were better able to discriminate human faces than monkey faces (p < .001). However, the ELBW group discriminated between human faces (p < .001), between monkey faces (p < .001), and to some degree, between houses (p < .06), more poorly than NBW control participants, suggesting a general deficit in perceptual processing. Human face discrimination was related to performance IQ (PIQ) across groups, but especially among ELBW survivors. Coding (a PIQ subtest) also predicted human face discrimination in ELBW survivors, consistent with previously reported links between visuo-perceptive difficulties and regional slowing of cortical activity in individuals born preterm. Correlations with Coding suggested ELBW survivors may have used a feature-matching approach to processing human faces. Future studies could examine brain-based anatomical and functional evidence for altered face processing, as well as the social and memory consequences of face-processing deficits in ELBW survivors.

Choosing appropriate tools and referral criteria for vision screening of children aged 4-5 years in Canada: a quantitative analysis.

OBJECTIVES: To assess the diagnostic accuracy of five vision screening tools used in a school setting using sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). DESIGN: We compared the results of the five best evidence-based screening tools available in 2014 to the results of a comprehensive eye exam with cycloplegic refraction by a licenced optometrist. Screening included Cambridge Crowded Acuity Cards, Plusoptix S12 and Spot photoscreeners, Preschool Randot Stereoacuity Test and the Pediatric Vision Scanner (PVS). Referral criteria followed AAPOS (2013) guidelines and published norms. SETTING: A large school in Toronto, Canada, with 25 split classrooms of junior kindergarten (JK: 4 year olds) and senior kindergarten (SK: 5 year olds) children. PARTICIPANTS: Over 2 years, 1132 eligible children were enrolled at the school. After obtaining parental consent, 832 children were screened. Subsequently, 709 children had complete screening and optometry exam data. MAIN OUTCOME MEASURES: The presence/absence of a visual problem based on optometrist's assessment: amblyopia, amblyopia risk factors (reduced stereoacuity, strabismus and clinically significant refractive errors) and any other ocular problem (eg, nystagmus). RESULTS: Overall, 26.5% of the screened children had a visual problem, including 5.9% with amblyopia. Using all five tools, screening sensitivity=84% (95% CI 78 to 89), specificity=49% (95% CI 44 to 53), PPV=37% (95% CI 33 to 42), and NPV=90% (95% CI 86 to 93). The odds of having a correct screening result in SK (mean age=68.2 months) was 1.5 times those in JK (mean age=55.6 months; 95% CI 1.1 to 2.1), with sensitivity improved to 89% (95% CI 80 to 96) and specificity improved to 57% (95% CI 50 to 64) among SK children. CONCLUSIONS: A school-based screening programme correctly identified 84% of those kindergarten children who were found to have a visual problem by a cyclopleged optometry exam. Additional analyses revealed how accuracy varies with different combinations of screening tools and referral criteria.

Developmental changes in the perception of audiotactile simultaneity.

We charted the developmental trajectory of the perception of audiotactile simultaneity by testing three groups of children (aged 7, 9, and 11 years) and one group of adults. A white noise burst and a tap to the index finger were presented at 1 of 13 stimulus onset asynchronies (SOAs), and the participants were asked to report whether the two stimuli were simultaneous. Compared with adults, 7-year-olds made significantly more simultaneous responses at 9 of the 13 SOAs, whereas 9-year-olds differed from adults at only 2 SOAs. The precision of simultaneity perception was lower, and response errors were higher, in younger children than in adults. The 11-year-olds were adult-like on all measures, thereby demonstrating that judgments about simultaneity for audiotactile stimuli are mature by 11 years. This developmental pattern is similar to that for simultaneity perception for visuotactile stimuli but later than that for audiovisual stimuli. The longer developmental trajectories of the perception of simultaneity between touch and vision and between touch and audition may arise from the need to coordinate and recalibrate between different reference frames and different neural transmission times in each sensory system during body growth; in addition, the ubiquity of audiovisual experience in everyday life may accelerate the development of that modality pairing.

Access to Vision Services by Vulnerable Populations in Canada: A Scoping Review.

Vision impairment has a significant impact on quality of life. Seventy percent of existing vision impairment in Canada is estimated to be correctable with prescription glasses. The sizeable proportion of correctable vision impairment appears related to the barriers to access to vision care in Canada. The objective of this scoping review is to determine gaps in the understanding of barriers to accessing vision care for vulnerable populations in Canada. The Arksey and O'Malley methodological framework was adopted. Studies published in English between 2005 and September 2017 on access to primary vision care by vulnerable populations in Canada were reviewed. Electronic databases used included Ovid MEDLINE, Ovid EMBASE, SCOPUS, ProQuest, and CINAHL. The Behavioural Model of Health Services Use was used to elucidate gaps in the literature. To develop relevant policies around vision care, efforts should be made to assess all dimensions of access for vulnerable populations across Canada.

Classification and diversity of amblyopia.

Amblyopia is a developmental disorder that affects the spatial vision of one or both eyes in the absence of an obvious organic cause; it is associated with a history of abnormal visual experience during childhood. Subtypes have been defined based on the purported etiology, namely, strabismus (misaligned eyes) and/or anisometropia (unequal refractive error). Here we consider the usefulness of these subclassifications.

Developmental changes in the perception of visuotactile simultaneity.

A simultaneity judgment (SJ) task was used to measure the developmental trajectory of visuotactile simultaneity perception in children (aged 7, 9, 11, and 13 years) and adults. Participants were presented with a visual flash in the center of a computer monitor and a tap on their right index finger (located 20° below the flash) with 13 possible stimulus onset asynchronies (SOAs). Participants reported whether the flash and tap were presented at the same time. Compared with the adult group, children aged 7 and 9 years made more simultaneous responses when the tap led by more than 300 ms and when the flash led by more than 200 ms, whereas they made fewer simultaneous responses at the 0 ms SOA. Model fitting demonstrated that the window of visuotactile simultaneity became narrower with development and reached adult-like levels between 9 and 11 years of age. Response errors decreased continuously until 11 years of age. The point of subjective simultaneity (PSS) was located on the tactile-leading side in all participants tested, indicating that 7-year olds (the youngest age tested) are adult-like on this measure. In summary, the perception of visuotactile simultaneity is not fully mature until 11 years of age. The protracted development of visuotactile simultaneity perception may be related to the need for crossmodal recalibration as the body grows and to the developmental improvements in the ability to optimally integrate visual and tactile signals.

The relationship between discrimination and memory for spacing and feature changes in houses.

Adults need to discriminate between stimuli and recognize those previously seen. For faces, feature changes (e.g., different eyes) and spacing changes (e.g., distances between eyes) are important cues. In two experiments, we assessed the influence of these on discrimination and recognition of houses, a commonly used control in face studies. In both experiments, discrimination was better for feature than spacing changes. Memory for spacing changes was generally poor but aided by extra learning and intermixing change types. Conversely, memory for features was good, especially when there were few houses, and change type was blocked. Unexpectedly, memory was best for differences that might signal something about occupants (e.g., changes to garden or bins), perhaps akin to hairstyles for faces. Overall, results are consistent with previous work showing poor discrimination of spacing in non-face objects and extends them to show that, unlike for faces, spacing differences are also not well remembered.

Sensitivity to facial expressions among extremely low birth weight survivors in their 30s.

The current study investigated the impact of birth weight on the ability to recognize facial expressions in adulthood among the longest known prospectively followed cohort of extremely low birth weight survivors (ELBW; <1,000 g). We measured perceptual threshold to detect subtle facial expressions and confusion among different emotion categories in order to disentangle visual perceptual ability from emotional processing. ELBW adults (N = 64, Mage = 31.9 years) were more likely than normal birth weight (NBW) controls (N = 82, Mage = 32.5 years) to see fear in angry faces. This finding was not a result of increased perceptual efficiency in processing fearful expressions in the ELBW adults, since the two groups did not differ on their threshold to detect emotion in low intensity facial expressions. These findings suggest that a processing bias toward fear may reflect long-term developmental effects from being born at ELBW that may portend socioemotional problems that characterize ELBW survivors.