Visual development

Visual Acuity Among Portuguese School-Aged Population

Background/Objectives: Visual acuity (VA) screening is highly valid in school-aged children for detecting visual impairments. This study aims to provide a comprehensive profile of VA among school-aged children (6-17 years old) from Lisbon, Portugal. Specifically, it focuses on estimating the prevalence of abnormal VA (VA < 0.8 in the worst eye) and establishing age-specific normative reference values (percentiles) for monocular and binocular VA within this urban sample. Methods: We performed an observational, descriptive, and cross-sectional study that included healthy children aged 6 to 17 years. Convenience sampling was used in three educational centers in Lisbon. Retinoscopy and monocular VA (right eye, left eye, and the eye with the lowest) and binocular VA were assessed using the Herman Snellen optotype. Descriptive statistics, prevalence of abnormal VA (worst-eye VA < 0.8), and monocular and binocular VA percentiles were calculated for the whole cohort and by age. Results: The sample consisted of 2215 children (49.6% of males; and 9.4 ± 2.6 years old). Binocular VA, right-eye VA, left-eye VA, and VA worst eye in the study cohort showed ranges of 0.92-1.00, 0.90-0.95, 0.89-0.97, and 0.85-0.94, respectively, for ages 6-17 years. In total, 86.8% of the study population had a normal VA (≥0.8). VA deficit was mild (0.8 < AV ≥ 0.3), moderate (0.3 < AV ≥ 0.125), and severe (VA < 0.125) in 10.5%, 1.1%, and 1.6% of children, respectively. Conclusions: Our study provides both age-specific normative reference values for visual acuity in Portuguese children and prevalence estimates for visual acuity deficits. These findings offer critical data to support early detection strategies and the development of age-adjusted vision-screening protocols in school-aged populations.

Three-year changes in ocular biometric components in children with amblyopia

BACKGROUND

Amblyopia is associated with structural differences in ocular biometrics, but existing studies often lack long-term follow-ups. This study compares three-year changes in ocular biometric components in amblyopic and non-amblyopic eyes.

METHODS

In this prospective cohort, study data were collected in 2015 and 2018 in Shahroud, northeast Iran. The sample comprised 4968 primary students (9935 eyes), including 4931 non-amblyopic students (9893 eyes) and 37 students with amblyopia (42 eyes). Axial length, keratometry, central corneal thickness, lens thickness, pupil diameter, anterior chamber depth, lens power and vitreous chamber depth were measured using Lenstar LS900. Multilevel mixed-effects regression models were used to determine any association between variables.

RESULTS

The mean age of children without and with amblyopia at baseline were 9.7 ± 1.7 and 9.9 ± 1.5 years, respectively. The mean axial elongation in amblyopic and non-amblyopic groups over three years was 0.37 (95% CI: 0.34-0.40) and 0.33 mm (95% CI: 0.31-0.34), respectively (p < 0.001). Amblyopic eyes showed greater axial elongation than non-amblyopic eyes (p < 0.001). Anterior chamber depth was constant in amblyopic eyes while it decreased in non-amblyopic eyes by 0.13 mm. Vitreous chamber depth increased significantly in both groups, with a greater increase observed in the amblyopic eyes (0.36 vs. 0.28 mm) (p < 0.001). Flat and steep keratometry increased significantly in amblyopic eyes (p < 0.001), while it was constant in non-amblyopic eyes. Lens power decreased significantly in both groups (p < 0.001). The increase in the axial length and vitreous chamber depth in the amblyopic eye was greater than in the non-amblyopic eyes (p < 0.001). The spherical equivalent change in both groups was - 0.31 D.

CONCLUSIONS

Amblyopia was associated with significant changes in key biometric parameters, offering valuable insight into the structural alterations underlying the condition.

Relation between binocular vision alteration and prehension movements in children: a scoping review

PURPOSE

To investigate, map, and synthesize evidence regarding the correlation between changes in binocular vision and fine motor skills among children.

METHODS

We conducted a scoping review of existing evidence, following the guidelines and checklist outlined in "Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Scoping Reviews" (PRISMAScR).

RESULTS

Sixteen papers were systematically included in our scoping review. A predominant focus was placed on assessing the impact of strabismus on motor skills. Most of the studies used motor test batteries for comprehensive analysis, while the remaining employed methodologies, such as questionnaires or laboratory-based tests.

CONCLUSION

Vision stands as a pivotal perceptual modality essential for the optimal development of children. Alterations in visual acuity can significantly affect fine motor skills. Pediatric ophthalmology and orthoptics frequently encounter binocular vision disorders, such as amblyopia and strabismus. Our finding showed that impaired binocular vision affects fine motor skills.

Deficiency of Acetyltransferase nat10 in Zebrafish Causes Developmental Defects in the Visual Function

Purpose

N4-acetylcytidine (ac4C) is a post-transcriptional RNA modification catalyzed by N-acetyltransferase 10 (NAT10), a critical factor known to influence mRNA stability. However, the role of ac4C in visual development remains unexplored.

Methods

Analysis of public datasets and immunohistochemical staining were conducted to assess the expression pattern of nat10 in zebrafish. We used CRISPR/Cas9 and RNAi technologies to knockout (KO) and knockdown (KD) nat10, the zebrafish ortholog of human NAT10, and evaluated its effects on early development. To assess the impact of nat10 knockdown on visual function, we performed comprehensive histological evaluations and behavioral analyses. Transcriptome profiling and real-time (RT)-PCR were utilized to detect alterations in gene expression resulting from the nat10 knockdown. Dot-blot and RNA immunoprecipitation (RIP)-PCR analyses were conducted to verify changes in ac4C levels in both total RNA and opsin mRNA specifically. Additionally, we used the actinomycin D assay to examine the stability of opsin mRNA following the nat10 KD.

Results

Our study found that the zebrafish NAT10 protein shares similar structural properties with its human counterpart. We observed that the nat10 gene was prominently expressed in the visual system during early zebrafish development. A deficiency of nat10 in zebrafish embryos resulted in increased mortality and developmental abnormalities. Behavioral and histological assessments indicated significant vision impairment in nat10 KD zebrafish. Transcriptomic analysis and RT-PCR identified substantial downregulation of retinal transcripts related to phototransduction, light response, photoreceptors, and visual perception in the nat10 KD group. Dot-blot and RIP-PCR analyses confirmed a pronounced reduction in ac4C levels in both total RNA and specifically in opsin messenger RNA (mRNA). Additionally, by evaluating mRNA decay in zebrafish treated with actinomycin D, we observed a significant decrease in the stability of opsin mRNA in the nat10 KD group.

Conclusions

The ac4C-mediated mRNA modification plays an essential role in maintaining visual development and retinal function. The loss of NAT10-mediated ac4C modification results in significant disruptions to these processes, underlining the importance of this RNA modification in ocular development.

Motion and Form Perception in Childhood-Onset Schizophrenia

(1) Background: Childhood-onset schizophrenia (COS) is a rare type of psychotic disorder characterized by delusions, hallucinations, grossly disorganized behavior, and poor psychosocial functioning. The etiology of COS is unknown, but neurodevelopmental factors are likely to play a critical role. A potential neurodevelopmental anomaly marker is the dorsal visual system dysfunction, which is implicated in motion perception, spatial functions, and attention. (2) Methods: To elucidate the role of the dorsal visual system in COS, we investigated 21 patients with COS and 21 control participants matched for age, sex, education, IQ, and parental socioeconomic status. Participants completed a motion and form coherence task, during which one assesses an individual's ability to detect the direction of motion within a field of moving elements or dots and to recognize a meaningful form or object from a set of fragmented or disconnected visual elements, respectively. (3) Results: The patients with COS were impaired in both visual tasks compared to the control participants, but the evidence for the deficit was more substantial for motion perception than for form perception (form: BF10 = 27.22; motion: BF10 = 6.97 × 106). (4) Conclusions: These results highlight the importance of dorsal visual stream vulnerability in COS, a potential marker of neurodevelopmental anomalies.

Structural networking of the developing brain: from maturation to neurosurgical implications

Modern neuroscience agrees that neurological processing emerges from the multimodal interaction among multiple cortical and subcortical neuronal hubs, connected at short and long distance by white matter, to form a largely integrated and dynamic network, called the brain "connectome." The final architecture of these circuits results from a complex, continuous, and highly protracted development process of several axonal pathways that constitute the anatomical substrate of neuronal interactions. Awareness of the network organization of the central nervous system is crucial not only to understand the basis of children's neurological development, but also it may be of special interest to improve the quality of neurosurgical treatments of many pediatric diseases. Although there are a flourishing number of neuroimaging studies of the connectome, a comprehensive vision linking this research to neurosurgical practice is still lacking in the current pediatric literature. The goal of this review is to contribute to bridging this gap. In the first part, we summarize the main current knowledge concerning brain network maturation and its involvement in different aspects of normal neurocognitive development as well as in the pathophysiology of specific diseases. The final section is devoted to identifying possible implications of this knowledge in the neurosurgical field, especially in epilepsy and tumor surgery, and to discuss promising perspectives for future investigations.

Visual Function and Neuropsychological Profiling of Idiopathic Infantile Nystagmus

Though considered a benign condition, idiopathic infantile nystagmus (IIN) may be associated with decreased visual acuity and oculo-motor abnormalities, resulting in developmental delays and poor academic performance. Nevertheless, the specific visual function profile of IIN and its possible impact on neuropsychological development have been poorly investigated. To fill this gap, we retrospectively collected the clinical data of 60 children presenting with IIN over a 10-year period (43 male; mean age of 7 years, range of 2 months-17 years, 9 months). The majority of the subjects in our cohort presented with reduced visual acuity for far distances and normal visual acuity for near distances, associated with oculo-motor abnormalities. The overall scores of cognitive and visual-cognitive tests were in the normal range, but revealed peculiar cognitive and visual-cognitive profiles, defined by specific frailties in processing speed and visual-motor integration. The same neuropsychological profiles characterize many neurodevelopmental disorders and may express a transnosographic vulnerability of the dorsal stream. As the first study to explore the neuropsychologic competencies in children with IIN, our study unveils the presence of subclinical frailties that need to be addressed to sustain academic and social inclusion.

Visual tracking at 4 months in preterm infants predicts 6.5-year cognition and attention

BACKGROUND

Visual tracking of moving objects requires sustained attention and prediction of the object's trajectory. We tested the hypothesis that measures of eye-head tracking of moving objects are associated to long-term neurodevelopment in very preterm infants.

METHODS

Visual tracking performance was assessed at 4 month's corrected age in 57 infants with gestational age <32 weeks. An object moved in front of the infant with sinusoidal or triangular (i.e. abrupt) turns of the direction. Gaze gain, smooth pursuit gain, and timing of gaze to object motion were analyzed. At 6.5 years the Wechsler Intelligence Scale for Children (WISC-IV), the Brown Attention Deficit Disorder (Brown ADD), and visual examination were performed.

RESULTS

Gaze gain and smooth pursuit gain at 4 months were strongly related to all WISC-IV parameters at 6.5 years. Gaze gain for the triangular and sinusoidal motion patterns related similarly to the cognitive scores. For the sinusoidal motion pattern, timing related to most Brown ADD parameters. There were no statistically significant differences in associations dependent on motion pattern. Visual function did not influence the results.

CONCLUSION

The ability to attend to and smoothly track a moving object in infancy is an early marker of cognition and attention at 6.5 years.

IMPACT

Potential long-term implications of infant visual tracking of moving objects for school-age neurodevelopment has not been previously studied in very preterm infants. Early coordination of eye and head movements in gaze gain, smooth pursuit, and timing of gaze to object motion are closely associated with cognition and attention at 6.5 years. As related functions at 6.5 years include perceptual and verbal skills, working memory, processing speed and attention, predictive elements in gaze tracking of moving objects might be a suitable target for future intervention studies.

High Risk for Attention-Deficit Hyperactive Disorder in Children with Strabismus: A Nationwide Cohort Study from the National Health Insurance Research Database

Strabismus is associated with amblyopia and a lower quality of life. Attention-deficit hyperactivity disorder (ADHD) is common among children and adolescents, and influences their academic, vocational, and social life. Previous studies have suggested an association between strabismus and ADHD. Using data from the Taiwan National Health Insurance Research Database between 2000 and 2010, we performed a large-scale cohort study comparing the incidence, risk factors, and severity of ADHD in children with and without strabismus. A total of 2049 patients <18 years old with newly diagnosed strabismus (esotropia: 404; exotropia: 1645) were identified, and 8196 age- and sex-matched controls without strabismus were also included. After an average of 6.5 ± 2.9 years of follow-up, the incidence of ADHD per 1000 person-years was 5.39 in the strabismus group (esotropia: 9.93; exotropia: 4.11) and 3.23 in the control group. The cumulative incidence of ADHD was significantly greater in the esotropia (hazard ratio [HR]: 2.04; 95% confidence interval [CI]:1.36-3.06; p = 0.0007) and exotropia groups (HR: 1.44; 95% CI: 1.03-2.03; p = 0.038) than in the controls. Patients with strabismus had more comorbidities than those without (p < 0.05). In summary, this large-scale study found a higher cumulative incidence of ADHD in patients with strabismus, especially in those with esotropia.

Cortical Visual Impairments and Learning Disabilities

Medical advances in neonatology have improved the survival rate of premature infants, as well as children who are born under difficult neurological conditions. As a result, the prevalence of cerebral dysfunctions, whether minimal or more severe, is increasing in all industrialized countries and in some developing nations. Whereas in the past, ophthalmological diseases were considered principally responsible for severe visual impairment, today, all recent epidemiological studies show that the primary cause of blindness and severe visual impairment in children in industrialized countries is now neurological, with lesions acquired around the time of birth currently comprising the commonest contributor. The resulting cortical or cerebral visual impairments (CVIs) have long been ignored, or have been confused either with other ophthalmological disorders causing low vision, or with a range of learning disabilities. We present here the deleterious consequences that CVI can have upon learning and social interaction, and how these can be given behavioral labels without the underlying visual causes being considered. We discuss the need to train and inform clinicians in the identification and diagnosis of CVI, and how to distinguish the diagnosis of CVI from amongst other visual disorders, including the specific learning disorders. This is important because the range of approaches needed to enhance the development of children with CVI is specific to each child's unique visual needs, making incorrect labeling or diagnosis potentially detrimental to affected children because these needs are not met.

Presence of the Endocannabinoid System in the Inferior Pulvinar of the Vervet Monkey

The expression of the endocannabinoid (eCB) system, including cannabinoid receptor type 1 (CB1R) and the cannabinoid synthesizing (NAPE-PLD) and degrading (FAAH) enzymes, has been well-characterized in the retina of rodents and monkeys. More recently, the presence of CB1R was localized throughout the dorsal lateral geniculate nucleus of the thalamus of vervet monkeys. Given that the retina projects also to the pulvinar either via a direct projection or via the superior colliculus, it was reasonable to assume that this system would be present therein. The visual pulvinar, namely the inferior pulvinar (PI) region, was delineated with calbindin immunohistochemical staining. Using Western blots and immunofluorescence, we demonstrated that CB1R, NAPE-PLD and FAAH are expressed in the PI of the vervet monkey. Throughout the PI, CB1R was mainly colocalized with VGLUT2-positive axon terminals in the vicinity of calbindin and parvalbumin-positive neurons. NAPE-PLD and FAAH rather colocalized with calbindin over the somatodendritic compartment of PI neurons. Our results suggest that visual information coming from the retina and entering the PI is modulated by the eCB system on its way to the dorsal visual stream. These results provide insights for understanding the role of eCBs in the modulation of visual thalamic inputs and, hence, visual perception.