Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance.

We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific beta-tubulin isotype III, result in a spectrum of human nervous system disorders that we now call the TUBB3 syndromes. Each mutation causes the ocular motility disorder CFEOM3, whereas some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy. Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts. A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities. We show that the disease-associated mutations can impair tubulin heterodimer formation in vitro, although folded mutant heterodimers can still polymerize into microtubules. Modeling each mutation in yeast tubulin demonstrates that all alter dynamic instability whereas a subset disrupts the interaction of microtubules with kinesin motors. These findings demonstrate that normal TUBB3 is required for axon guidance and maintenance in mammals.

James Sharpe's Contributions to Neurology and Neuro-ophthalmology: A Posthumous Tribute 10 Years On.

Dr. Sharpe was a leading eye movement researcher who had also been the editor of this journal. We wish to mark the 10th anniversary of his death by providing a sense of what he had achieved through some examples of his research.

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.

Audiovisual perception in amblyopia: A review and synthesis.

Amblyopia is a common developmental sensory disorder that has been extensively and systematically investigated as a unisensory visual impairment. However, its effects are increasingly recognized to extend beyond vision to the multisensory domain. Indeed, amblyopia is associated with altered cross-modal interactions in audiovisual temporal perception, audiovisual spatial perception, and audiovisual speech perception. Furthermore, although the visual impairment in amblyopia is typically unilateral, the multisensory abnormalities tend to persist even when viewing with both eyes. Knowledge of the extent and mechanisms of the audiovisual impairments in amblyopia, however, remains in its infancy. This work aims to review our current understanding of audiovisual processing and integration deficits in amblyopia, and considers the possible mechanisms underlying these abnormalities.

Visuomotor Behaviour in Amblyopia: Deficits and Compensatory Adaptations.

Amblyopia is a neurodevelopmental visual disorder arising from decorrelated binocular experience during the critical periods of development. The hallmark of amblyopia is reduced visual acuity and impairment in binocular vision. The consequences of amblyopia on various sensory and perceptual functions have been studied extensively over the past 50 years. Historically, relatively fewer studies examined the impact of amblyopia on visuomotor behaviours; however, research in this area has flourished over the past 10 years. Therefore, the aim of this review paper is to provide a comprehensive review of current knowledge about the effects of amblyopia on eye movements, upper limb reaching and grasping movements, as well as balance and gait. Accumulating evidence indicates that amblyopia is associated with considerable deficits in visuomotor behaviour during amblyopic eye viewing, as well as adaptations in behaviour during binocular and fellow eye viewing in adults and children. Importantly, due to amblyopia heterogeneity, visuomotor development in children and motor skill performance in adults may be significantly influenced by the etiology and clinical features, such as visual acuity and stereoacuity. Studies with larger cohorts of children and adults are needed to disentangle the unique contribution of these clinical characteristics to the development and performance of visuomotor behaviours.

Visual search deficits in amblyopia.

Amblyopia is a neurodevelopmental disorder defined as a reduction in visual acuity that cannot be corrected by optical means. It has been associated with low-level deficits. However, research has demonstrated a link between amblyopia and visual attention deficits in counting, tracking, and identifying objects. Visual search is a useful tool for assessing visual attention but has not been well studied in amblyopia. Here, we assessed the extent of visual search deficits in amblyopia using feature and conjunction search tasks. We compared the performance of participants with amblyopia (n = 10) to those of controls (n = 12) on both feature and conjunction search tasks using Gabor patch stimuli, varying spatial bandwidth and orientation. To account for the low-level deficits inherent in amblyopia, we measured individual contrast and crowding thresholds and monitored eye movements. The display elements were then presented at suprathreshold levels to ensure that visibility was equalized across groups. There was no performance difference between groups on feature search, indicating that our experimental design controlled successfully for low-level amblyopia deficits. In contrast, during conjunction search, median reaction times and reaction time slopes were significantly larger in participants with amblyopia compared with controls. Amblyopia differentially affects performance on conjunction visual search, a more difficult task that requires feature binding and possibly the involvement of higher-level attention processes. Deficits in visual search may affect day-to-day functioning in people with amblyopia.

Using the Time-Driven Activity-Based Costing Model in the Eye Clinic at The Hospital for Sick Children: A Case Study and Lessons Learned.

One of the key challenges to healthcare organizations is the development of relevant and accurate cost information. In this paper, we used time-driven activity-based costing (TDABC) method to calculate the costs of treating individual patients with specific medical conditions over their full cycle of care. We discussed how TDABC provides a critical, systematic and data-driven approach to estimate costs accurately and dynamically, as well as its potential to enable structural and rational cost reduction to bring about a sustainable healthcare system.

Lean Transformation of the Eye Clinic at The Hospital for Sick Children: Challenging an Implicit Mental Model and Lessons Learned.

Long patient dwell time (i.e., the time between patients arriving and leaving the clinic) has been a long-standing issue in the eye clinic at The Hospital for Sick Children. By applying the Lean principles of eliminating waste and enhancing flow, we achieved a 26% reduction in the mean patient dwell time over an eight-month period. Importantly, the average time a patient spent with healthcare providers (value-added time) increased from 21% to 31%. In this paper, we summarized our experience by illustrating how an implicit mental model (conscious or unconscious conceptual framework from which we understand the world) pervades in the healthcare system based on deeply held but unexamined assumptions that arise from heuristics (general rules of thumb) and biases; how these assumptions can be tested by objective data; and how we can build a new mental model based on objective findings to improve the healthcare system.

Acquired myelinated retinal nerve fiber layer in a child with neurofibromatosis 1-related optic pathway glioma.

Myelinated retinal nerve fiber layer (RNFL) is a rare structural anomaly that occurs from abnormal myelination extending anterior to the lamina cribrosa. Clinically, myelinated RNFL is characterized as a gray-white lesion with feathered, well-demarcated borders obscuring the retinal vasculature. Myelinated RNFL is typically congenital, benign, and asymptomatic. It is most commonly noted as an incidental finding on ophthalmic examination. However, cases of acquired myelinated RNFL have been reported. We report the case of a patient with neurofibromatosis type 1 and optic pathway glioma with unilateral acquired myelinated RNFL.

Diagnostic utility of point-of-care ultrasound and optical coherence tomography for papilloedema in children: a prospective pilot study.

BACKGROUND/AIMS: Papilloedema is an important sign of serious neurological disease, but it can be difficult to detect on funduscopy. The purpose of this study was to determine the diagnostic accuracy of point-of-care ultrasound (POCUS) and optical coherence tomography (OCT) for detecting papilloedema in children. METHODS: This was a prospective observational study at a tertiary care paediatric hospital. Patients were eligible for the study if they underwent a lumbar puncture with opening pressure and had high-quality POCUS and OCT imaging. RESULTS: A total of 63 eyes from 32 patients were included in the study, 41 (65%) with papilloedema and 22 (35%) without. There were statistically significant differences between the groups in the optic disc elevation (ODE) (p<0.001) and optic nerve sheath diameter (ONSD) (p<0.001) on POCUS, and in the average retinal nerve fibre layer (rNFL) thickness on OCT (p<0.001). Average rNFL thickness had the highest diagnostic accuracy with an area under the curve (AUC) of 0.999 and a 100% sensitivity and 95% specificity for papilloedema (threshold value of ≥108 µm). ODE had an AUC of 0.866 and a 93% sensitivity and 55% specificity (threshold value of ≥0.5 mm). ONSD had an AUC of 0.786 and a 93% sensitivity and 45% specificity (threshold value of ≥5.5 mm). CONCLUSION: Both OCT and POCUS are potentially useful tools to help diagnose papilloedema in children. Larger studies are needed to further define the role and accuracy of POCUS and OCT in assessing papilloedema in children.

Clinical translation of recommendations from randomized clinical trials on patching regimen for amblyopia.

PURPOSE: To investigate whether the evidence-based recommendations by the Pediatric Eye Disease Investigator Group (PEDIG) as initial treatment of amblyopia have been implemented into clinical practice and to discuss the necessary steps in translating evidence-based knowledge to inform clinical decision making. DESIGN: Retrospective cohort study. PARTICIPANTS: Children with amblyopia seen from 2007 through 2009 by academic and community ophthalmologists in a large urban center in North America that serves a population of more than 8 million. Using PEDIG criteria, moderate amblyopia was defined as visual acuity between 20/40 and 20/80 and severe amblyopia was defined as visual acuity between 20/100 and 20/400. INTERVENTION: Patching of the sound eye. MAIN OUTCOME MEASURES: The number of prescribed patching hours daily and the amblyopic eye visual acuity expressed as logarithm of the minimum angle of resolution (logMAR). RESULTS: For moderate amblyopia, the cohort (n = 71) was prescribed a mean of 3.2 hours of daily patching (95% confidence interval [CI]: 2.8-3.6 hours), which is significantly greater than the recommended 2 hours of daily patching for initial treatment. Only 24% (95% CI, 16%-35%) of them were prescribed the recommended initial patching hours. The amblyopic eye acuity on the 3- to 6-month visit in the cohort (0.23 logMAR) was similar to that of the 4-month visit in the PEDIG cohort (0.24 logMAR; P = 0.74). For severe amblyopia, the cohort (n = 52) was prescribed a mean of 3.9 hours of daily patching (95% CI, 3.5-4.3 hours), which is significantly lower than the recommended 6 hours of daily patching for initial treatment. Only 12% (95% CI, 5%-23%) of them were prescribed the recommended initial patching hours. The amblyopic eye acuity at the 7- to 12-month visit in the cohort (0.44 logMAR) was comparable with that of the 4-month visit in the PEDIG cohort (0.40 logMAR; P = 0.35). CONCLUSIONS: The evidence-based recommendations for amblyopia management have not been translated widely into changes in clinical practice in a large urban center in North America, although there is a general move from full-time to part-time patching since the PEDIG results were published. Using a well-established framework for knowledge translation, the Knowledge-to-Action Cycle, the necessary steps required to implement new knowledge into actual clinical practice are discussed.

Vision Beyond Vision: Lessons Learned from Amblyopia.

Amblyopia is characterized by spatiotemporal uncertainty in the visual system. In addition to its effects on vision, amblyopia also exerts a widespread impact on other systems. Many of these changes are observed not only during amblyopic eye viewing but also during fellow eye and binocular viewing. They generally correlate with the severity of visual acuity and stereo acuity loss. The affected systems include: (1) oculomotor control manifested as abnormal fixation, saccades, smooth pursuit, and saccadic adaptation; (2) motor control with altered programming, execution, and temporal dynamics of eye-hand coordination, and decreased ability of the sensorimotor system to adapt to changes in the visual environment; (3) balance control with decreased postural stability; (4) multisensory integration characterized by reduced McGurk effect and altered cross-modal interactions in audiovisual perception; and (5) auditory localization manifested as impaired spatial hearing as a result of abnormal developmental calibration of the auditory map. To detect amblyopia early, a targeted approach is required to identify children from low-income families through in-school visual screening, supplemented by follow-up care and free eyeglasses in high-needs schools.

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.

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.

Beyond burnout: looking deeply into physician distress.

Physician wellness is an important issue and a growing concern within the medical profession. Although "burnout" is a commonly used term to describe physician distress, it fails to capture the many aspects of medicine that negatively impact physician wellness and what physicians experience. In this article, I will explore the personal (unhealthy perfectionism, pathologic altruism, self-recrimination, and the pitfalls of success), interpersonal (empathic distress, moral suffering, bullying, and marginalization), and systemic (medical culture, workplace environment and burnout, and health care system) factors that act interdependently and synergistically to give rise to physician distress. This article is a call for an earnest discussion and for implementing changes by addressing and reconsidering the place of physician wellness in medical practice, education, and research on the one hand, and its impact on patients, families, and society on the other.

Investigation of light-induced lacrimation and pupillary responses in episodic migraine.

The purpose of this pilot study was to investigate the light-induced pupillary and lacrimation responses mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) in migraine. Ten participants with episodic migraine and normal tear production, as well as eleven visually normal controls participated in this study. Following an initial baseline trial (no light flash), participants received seven incremental and alternating red and blue light flashes. Pupillometry recording of the left eye and a 1-min anesthetized Schirmer's test of the right eye (using 0.5% proparacaine) were performed simultaneously. Intrinsic and extrinsic ipRGC photoactivities did not differ between migraine participants and controls across all intensities and wavelengths. Migraine participants, however, had significantly lower lacrimation than controls following the highest blue intensity. A positive correlation was found between melanopsin-driven post-illumination pupillary responses and lacrimation following blue stimulation in both groups. Our results show that participants with self-reported photophobia have normal ipRGC-driven responses, suggesting that photophobia and pupillary function may be mediated by distinct ipRGC circuits. The positive correlation between melanopsin-driven pupillary responses and light-induced lacrimation suggests the afferent arm of the light-induced lacrimation reflex is melanopsin-mediated and functions normally in migraine. Lastly, the reduced melanopsin-mediated lacrimation at the highest stimulus suggests the efferent arm of the lacrimation reflex is attenuated under certain conditions, which may be a harbinger of dry eye in migraine.

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.

Impaired Spatial Hearing in Amblyopia: Evidence for Calibration of Auditory Maps by Retinocollicular Input in Humans.

Purpose: Evidence from animals and blind humans suggests that early visual experience influences the developmental calibration of auditory localization. Hypothesizing that unilateral amblyopia may involve cross-modal deficits in spatial hearing, we measured the precision and accuracy of sound localization in humans with amblyopia. Methods: All participants passed a standard hearing test. Experiment 1 measured sound localization precision for click stimuli in 10 adults with amblyopia and 10 controls using a minimum audible angle (MAA) task. Experiment 2 measured sound localization error (i.e., accuracy) for click train stimuli in 14 adults with amblyopia and 16 controls using an absolute sound localization task. Results: In Experiment 1, the MAA (mean ± SEM) was significantly greater in the amblyopia group compared with controls (2.75 ± 0.30° vs. 1.69 ± 0.09°, P = 0.006). In Experiment 2, the overall sound localization error was significantly greater in the amblyopia group compared with controls (P = 0.047). The amblyopia group also showed significantly greater sound localization error in the auditory hemispace ipsilateral to the amblyopic eye (P = 0.036). At a location within this auditory hemispace, the magnitude of sound localization error correlated significantly with deficits in stereo acuity (P = 0.036). Conclusions: The precision and accuracy of sound localization are impaired in unilateral amblyopia. The asymmetric pattern of sound localization error suggests that amblyopic vision may interfere with the development of spatial hearing via the retinocollicular pathway.

Early neuroaxonal injury is seen in the acute phase of pediatric optic neuritis.

BACKGROUND: Thinning of the retinal nerve fiber layer (RNFL) and ganglion cell/inner plexiform layer (GCIPL) occur in the chronic phase after optic neuritis (ON) in children and reflect neuroaxonal injury. The objective of this study was to describe changes in RNFL and GCIPL thickness in the acute phase following pediatric ON. METHODS: Data were collected prospectively from consecutive children presenting with ON as part of an incident acquired demyelinating event. Children with a final diagnosis of multiple sclerosis (n = 9, 10 ON-affected eyes) or monophasic demyelination (n = 16, 25 ON-affected eyes) who underwent spectral-domain optical coherence tomography (OCT) testing within 30 days of symptom onset were included. Standardized visual assessment was performed at presentation and 6-18 months follow-up. OCT measures were compared to those of healthy controls (n = 25, 50 eyes). RESULTS: Median (interquartile range [IQR]) global RNFL thickness was increased in ON-affected eyes (155 µm [114-199 µm]) compared to control eyes (104 µm [98.5-107.5 µm]; p < 0.0001). Compared to controls, fellow eyes demonstrated a reduced temporal quadrant RNFL thickness (59 µm [53-72 µm] versus 71.5 µm [65-81 µm]; p = 0.013) and lower GCIPL thickness (80.5 µm [74-88 µm] versus 87 µm [85-89 µm]; p = 0.003). The ON-affected eyes of children with monophasic demyelination demonstrated a greater global RNFL thickness (183.5 µm [146.5-206 µm]) compared to the ON-affected eyes of children with multiple sclerosis (108.5 µm [95-124 µm]; p = 0.01). OCT measures at presentation did not predict low-contrast visual acuity nor color vision at 6-18 months follow-up. CONCLUSION: Children with multiple sclerosis show less RNFL swelling in their ON-affected eyes at onset compared to children with monophasic demyelination. Lower GCIPL and temporal RNFL thickness in the clinically unaffected eyes of those children with unilateral ON suggests the presence of pre-existing neuroaxonal injury in children presenting with a first episode of ON. This finding may be driven by the subset of children with multiple sclerosis.