Vision deficits in adults with Down syndrome

The role of Down syndrome cell adhesion molecule in Down syndrome

Down syndrome (DS) is caused by the presence of an extra copy of the entire or a portion of human chromosome 21 (HSA21). This genomic alteration leads to elevated expression of numerous HSA21 genes, resulting in a variety of health issues in individuals with DS. Among the genes located in the DS "critical region" of HSA21, Down syndrome cell adhesion molecule (DSCAM) plays an important role in neuronal development. There is a growing body of evidence underscoring DSCAM's involvement in various DS-related disorders. This review aims to provide a concise overview of the established functions of DSCAM, with a particular focus on its implications in DS. We delve into the roles that DSCAM plays in DS-associated diseases. In the concluding section of this review, we explore prospective avenues for future research to further unravel DSCAM's role in DS and opportunities for therapeutic treatments.

Vision Impairments in Young Adults with Down Syndrome

People with Down syndrome have more visual problems than the general population. They experience premature ageing, and they are expected to also have an acceleration in worsening visual function. A prospective observational study which includes visual acuity, refractive error, accommodation, binocular and colour vision was performed on young adults with (n = 69) and without (n = 65) Down syndrome and on a senior group (n = 55) without Down syndrome. Results showed significant differences in visual acuity between groups (p < 0.001), and it can be improved with a new prescription in 40% of the participants with Down syndrome. Regarding the accommodative state, no significant differences were found between groups of young people. Concerning binocular vision, 64.7% of strabismus was observed in the group with Down syndrome (p < 0.001). Visual abnormalities are significant in young adults with Down syndrome and are different from those of older people without Down syndrome, some of which can be improved by providing the optimal prescription as well as regular eye examinations.

A biophysiological framework exploring factors affecting speech and swallowing in clinical populations: focus on individuals with Down syndrome

Speech and swallowing are complex sensorimotor behaviors accomplished using shared vocal tract anatomy. Efficient swallowing and accurate speech require a coordinated interplay between multiple streams of sensory feedback and skilled motor behaviors. Due to the shared anatomy, speech and swallowing are often both impacted in individuals with various neurogenic and developmental diseases, disorders, or injuries. In this review paper, we present an integrated biophysiological framework for modeling how sensory and motor changes alter functional oropharyngeal behaviors of speech and swallowing, as well as the potential downstream effects to the related areas of language and literacy. We discuss this framework with specific reference to individuals with Down syndrome (DS). Individuals with DS experience known craniofacial anomalies that impact their oropharyngeal somatosensation and skilled motor output for functional oral-pharyngeal activities such as speech and swallowing. Given the increased risk of dysphagia and "silent" aspiration in individuals with DS, it is likely somatosensory deficits are present as well. The purpose of this paper is to review the functional impact of structural and sensory alterations on skilled orofacial behaviors in DS as well as related skills in language and literacy development. We briefly discuss how the basis of this framework can be used to direct future research studies in swallowing, speech, and language and be applied to other clinical populations.

Single-cell RNA sequencing of neural stem cells derived from human trisomic iPSCs reveals the abnormalities during neural differentiation of Down syndrome

Introduction

Down syndrome (DS) is the most common genetic condition that causes intellectual disability in humans. The molecular mechanisms behind the DS phenotype remain unclear. Therefore, in this study, we present new findings on its molecular mechanisms through single-cell RNA sequencing.

Methods

Induced pluripotent stem cells (iPSCs) from the patients with DS and the normal control (NC) patients were differentiated into iPSCs-derived neural stem cells (NSCs). Single-cell RNA sequencing was performed to achieve a comprehensive single-cell level differentiation roadmap for DS-iPSCs. Biological experiments were also performed to validate the findings.

Results and Discussion

The results demonstrated that iPSCs can differentiate into NSCs in both DS and NC samples. Furthermore, 19,422 cells were obtained from iPSC samples (8,500 cells for DS and 10,922 cells for the NC) and 16,506 cells from NSC samples (7,182 cells for DS and 9,324 cells for the NC), which had differentiated from the iPSCs. A cluster of DS-iPSCs, named DS-iPSCs-not differentiated (DSi-PSCs-ND), which had abnormal expression patterns compared with NC-iPSCs, were demonstrated to be unable to differentiate into DS-NSCs. Further analysis of the differentially expressed genes revealed that inhibitor of differentiation family (ID family) members, which exhibited abnormal expression patterns throughout the differentiation process from DS-iPSCs to DS-NSCs, may potentially have contributed to the neural differentiation of DS-iPSCs. Moreover, abnormal differentiation fate was observed in DS-NSCs, which resulted in the increased differentiation of glial cells, such as astrocytes, but decreased differentiation into neuronal cells. Furthermore, functional analysis demonstrated that DS-NSCs and DS-NPCs had disorders in axon and visual system development. The present study provided a new insight into the pathogenesis of DS.

Improving real-world skills in people with intellectual disabilities: an immersive virtual reality intervention

Virtual reality (VR) is a promising tool for training life skills in people with intellectual disabilities. However, there is a lack of evidence surrounding the implementation, suitability, and effectiveness of VR training in this population. The present study investigated the effectiveness of VR training for people with intellectual disabilities by assessing (1) their ability to complete basic tasks in VR, (2) real-world transfer and skill generalisation, and (3) the individual characteristics of participants able to benefit from VR training. Thirty-two participants with an intellectual disability of varying severity completed a waste management training intervention in VR that involved sorting 18 items into three bins. Real-world performance was measured at pre-test, post-test, and delayed time points. The number of VR training sessions varied as training ceased when participants met the learning target (≈ 90% correct). A survival analysis assessed training success probability as a function of the number of training sessions with participants split by their level of adaptive functioning (as measured on the Adaptive Behaviour Assessment System Third Edition). The learning target was met by 19 participants (59.4%) within ten sessions (Mdn = 8.5, IQR 4-10). Real-world performance significantly improved from pre- to post-test and pre- to delayed test. There was no significant difference from post- to delayed test. Further, there was a significant positive relationship between adaptive functioning and change in the real-world assessment from the pre-test to the post- and delayed tests. VR facilitated the learning of most participants, which led to demonstrations of real-world transfer and skill generalisation. The present study identified a relationship between adaptive functioning and success in VR training. The survival curve may assist in planning future studies and training programs.

The effect of a telehealth exercise intervention on balance in adults with Down syndrome

BACKGROUND

People with Down syndrome often present with balance deficits, which compromise safety during daily activity. While evidence shows that exercise can improve balance in the Down syndrome population, it is unclear if a telehealth method will elicit similar benefits. We aimed to examine the effects of a virtual exercise program on balance in adults with Down syndrome.

METHODS

Eighteen low-active participants with Down syndrome completed a 12-week telehealth exercise program based on the Mann Method. Balance testing took place before and after the intervention, which included: TUG, MCTSIB, FICSIT-4, and FRT. This study was registered as a clinical trial on ClinicalTrials.gov, identifier: NCT04647851.

RESULTS

Significant improvement was seen in the TUG (p = .043), FICSIT-4 (p = .019) and FRT (p = .019). All participants achieved maximum scores on the MCTSIB in pre- and post-testing.

CONCLUSIONS

Balance in low-active adults with Down syndrome significantly improved following the telehealth exercise program, which we attribute to the tailored exercises that address visual/vestibular deficits and hip muscle weakness.

Development of a Physical Therapy-Based Exercise Program for Adults with Down Syndrome

In adults with Down syndrome, the combination of low physical activity and fitness levels and the high prevalence of musculoskeletal co-morbidities stresses the need for specialized exercise programs. The goal of this research study was to develop a specialized exercise program for individuals with Down syndrome using the physical therapy approach of a systems review as the foundation. We first conducted an overview of the literature on co-morbidities in adults with Down syndrome using the systems review method to categorize these findings. We extracted recommendations for content and delivery of an exercise program based on the literature review, and finally composed a specialized exercise program for individuals with Down syndrome adhering to these recommendations.

Cell type characterization of spatiotemporal gene co-expression modules in Down syndrome brain

Down syndrome (DS) is the most common genetic cause of intellectual disability and increases the risk of other brain-related dysfunctions, like seizures, early-onset Alzheimer's disease, and autism. To reveal the molecular profiles of DS-associated brain phenotypes, we performed a meta-data analysis of the developmental DS brain transcriptome at cell type and co-expression module levels. In the DS brain, astrocyte-, microglia-, and endothelial cell-associated genes show upregulated patterns, whereas neuron- and oligodendrocyte-associated genes show downregulated patterns. Weighted gene co-expression network analysis identified cell type-enriched co-expressed gene modules. We present eight representative cell-type modules for neurons, astrocytes, oligodendrocytes, and microglia. We classified the neuron modules into glutamatergic and GABAergic neurons and associated them with detailed subtypes. Cell type modules were interpreted by analyzing spatiotemporal expression patterns, functional annotations, and co-expression networks of the modules. This study provides insight into the mechanisms underlying brain abnormalities in DS and related disorders.

Clinimetric properties of visuo-perceptual and visuo-cognitive assessment tools used for children with cerebral visual impairment and cerebral palsy or developmental delay: a systematic review

PURPOSE

The aim of this systematic review is to evaluate the psychometrics and clinical utility of visuo-perceptual and visuo-cognitive assessment tools in children with cerebral visual impairment (CVI) and cerebral palsy (CP) or neurodevelopmental delay (DD).

MATERIALS AND METHODS

Five databases (PubMed, EMBASE, SCOPUS, CINAHL, and Cochrane Database) were comprehensively searched from 1970 till June 2021. The PRISMA checklist was utilised to report on the process of selecting eligible papers. The methodological quality of included studies was evaluated using COnsenus-based Standards for the selection of health Measurement INstrument (COSMIN) checklist.

RESULTS

Of the 26 assessment tools identified, only seven tools had psychometric evidence supporting their use. Based on COSMIN guidelines, 60% of included studies were rated as inadequate or doubtful for their methodological quality of measurement properties, with equal number being rated as indeterminate on the overall rating.

CONCLUSIONS

Cerebral visual impairment due to its varied clinical presentation is often missed in children with CP and DD. There is a paucity of studies reporting on the validity and reliability of functional vision tools. Further studies are needed to conduct high-quality psychometric reporting using the updated COSMIN guidelines to identify appropriate functional vision tools for children with CP or DD.Implications for rehabilitationThere are paucity of studies evaluating the validity and reliability of existing perceptual and cognitive assessment tools in children with cerebral visual impairment (CVI) and cerebral palsy (CP).Development of age-appropriate assessment tools evaluating all aspects of functional vision will assist in providing more holistic child-centric rehabilitation programs.A combination of detailed perinatal history, direct observation, and clinical assessments of functional vision are important to recognise CVI in children with CP.

Considerations for measuring individual outcomes across contexts in Down syndrome: Implications for research and clinical trials

Individuals with Down syndrome (DS) are increasingly involved in clinical trials that target developmental outcomes, like cognition and behavior. The increased focus on treatment in DS has led to ongoing discussions regarding the selection of outcome measures using syndrome-informed criteria. This discourse is warranted as clinical trials can fail if the outcome measures selected are inappropriate for individuals with DS or do not take into account the behavioral phenotype commonly associated with DS. This review focuses on the challenges present in the measurement of outcomes in DS, with a specific focus on considerations made in evaluating cognitive, language, and behavioral/psychopathology outcomes. This review also provides a summary of recommendations for assessment of outcomes in these domains as well as recommendations for future research. The impact of physical health and assessment psychometrics on the measurement of outcomes is also reviewed.

Cognitive outcome measures for tracking Alzheimer's disease in Down syndrome

Down syndrome (DS) is now viewed as a genetic type of Alzheimer's disease (AD), given the near-universal presence of AD pathology in middle adulthood and the elevated risk for developing clinical AD in DS. As the field of DS prepares for AD clinical intervention trials, there is a strong need to identify cognitive measures that are specific and sensitive to the transition from being cognitively stable to the prodromal (e.g., Mild Cognitive Impairment-Down syndrome) and clinical AD (e.g., Dementia) stages of the disease in DS. It is also important to determine cognitive measures that map onto biomarkers of early AD pathology during the transition from the preclinical to the prodromal stage of the disease, as this transition period is likely to be targeted and tracked in AD clinical trials. The present chapter discusses the current state of research on cognitive measures that could be used to screen/select study participants and as potential outcome measures in future AD clinical trials with adults with DS. In this chapter, we also identify key challenges that need to be overcome and questions that need to be addressed by the DS field as it prepares for AD clinical trials in the coming years.

Associations among co-occurring medical conditions and cognition, language, and behavior in Down syndrome

BACKGROUND

Specific medical conditions are more prevalent in Down syndrome (DS) compared to the general population. Medical heterogeneity has also been hypothesized to contribute to variability in outcomes in DS.

AIMS

This project aimed to examine the association between medical conditions (i.e., gastrointestinal issues, hearing loss, vision problems, and congenital heart defects) and cognition, language, and behavior in children and adolescents with DS.

METHODS AND PROCEDURES

Participants were 73 children and adolescents with DS, ages 6-17 years (M = 12.67, SD = 3.16). Caregivers reported on participants' medical conditions, social behaviors, maladaptive behaviors, and executive function. Child cognitive abilities were also assessed.

OUTCOMES AND RESULTS

Of the 73 participants, 34.2% had gastrointestinal issues, 12.3% had uncorrected hearing loss, 26.0% had uncorrected vision problems, and 31.5% had congenital heart defects. Participants with gastrointestinal issues had significantly more challenges with social behaviors, maladaptive behaviors, and executive function compared to those without gastrointestinal issues.

CONCLUSIONS AND IMPLICATIONS

The associations identified between gastrointestinal issues and caregiver-reported behavioral characteristics in youth with DS contributes to our understanding of the interrelation between co-occurring medical conditions and child outcomes and has implications for approaches to care for individuals with DS.

Using virtual reality to improve classroom behaviour in people with Down syndrome: An experimental study (Preprint)

Background

People with Down syndrome face various learning challenges. Introducing new and enjoyable experiences in learning settings may improve learning outcomes. Immersive and interactive technologies such as virtual reality can be used to deliver rich visual experiences in classrooms.

Objective

The aim of this study was to investigate the feasibility and benefits of virtual reality exposure for people with Down syndrome in learning settings.

Methods

To address this aim, we used a within-subjects design to assess the effect of a brief virtual reality drawing experience and conventional drawing experience on subsequent behavior in 16 participants.

Results

Large positive effects were found for virtual reality drawing (t₁₅=5.020, P<.001) and conventional drawing (t₁₅=3.720, P=.002) in improving subsequent behavior in a learning setting. Irrespective of the intervention, the participant’s mood, attention, and overall behavior significantly improved. No significant differences were found between the interventions (t₁₅=–0.648; P=.53).

Conclusions

This study’s results are encouraging for researchers and educators interested in using virtual reality for people with Down syndrome, as virtual reality was found to be highly feasible. Recommendations are made for researchers and educators interested in providing virtual reality experiences for people with Down syndrome.

The Clinical and Neuropathological Features of Sporadic (Late-Onset) and Genetic Forms of Alzheimer's Disease

The purpose of this review is to compare and highlight the clinical and pathological aspects of genetic versus acquired Alzheimer's disease: Down syndrome-associated Alzheimer's disease in (DSAD) and Autosomal Dominant Alzheimer's disease (ADAD) are compared with the late-onset form of the disease (LOAD). DSAD and ADAD present in a younger population and are more likely to manifest with non-amnestic (such as dysexecutive function features) in the prodromal phase or neurological features (such as seizures and paralysis) especially in ADAD. The very large variety of mutations associated with ADAD explains the wider range of phenotypes. In the LOAD, age-associated comorbidities explain many of the phenotypic differences.

Comprehensive phenotypic analysis of the Dp1Tyb mouse strain reveals a broad range of Down syndrome-related phenotypes

Down syndrome (DS), trisomy 21, results in many complex phenotypes including cognitive deficits, heart defects and craniofacial alterations. Phenotypes arise from an extra copy of human chromosome 21 (Hsa21) genes. However, these dosage-sensitive causative genes remain unknown. Animal models enable identification of genes and pathological mechanisms. The Dp1Tyb mouse model of DS has an extra copy of 63% of Hsa21-orthologous mouse genes. In order to establish whether this model recapitulates DS phenotypes, we comprehensively phenotyped Dp1Tyb mice using 28 tests of different physiological systems and found that 468 out of 1800 parameters were significantly altered. We show that Dp1Tyb mice have wide-ranging DS-like phenotypes, including aberrant erythropoiesis and megakaryopoiesis, reduced bone density, craniofacial changes, altered cardiac function, a pre-diabetic state, and deficits in memory, locomotion, hearing and sleep. Thus, Dp1Tyb mice are an excellent model for investigating complex DS phenotype-genotype relationships for this common disorder.

Impact of two different pulmonary rehabilitation methods in children with down syndrome

PURPOSE

To investigate and compare the effect of proprioceptive neuromuscular facilitation of respiratory muscles with that of inspiratory muscle training as a preventive measure on respiratory muscle strength, chest expansion, spirometry, and functional capacity in children with Down syndrome.

METHODS

Forty-five Down syndrome participants with an age ranged from 10 to 13 years were enrolled. There were distributed into three groups. The study group A (n = 15) underwent proprioceptive neuromuscular facilitation of respiratory muscles while study group B (n = 15) underwent inspiratory muscle training. Third group C (n = 15) was a control group. The three groups received aerobic exercises using the bicycle ergometer for 20 min, 5 times/week for 12 successive weeks. The treatment program for both study groups was conducted for 20-30 min, 5 times/week for 12 successive weeks. Measurements of respiratory muscle strength (MIP, MEP), chest expansion, spirometry test (VC, FEV1, PEFR, MVV) and 6 min walk test were measured pre and post treatment.

RESULTS

The post treatment mean values of all investigated variables were significantly increased in both study groups with higher effect to group underwent proprioceptive neuromuscular facilitation of respiratory muscles.

CONCLUSION

Both proprioceptive neuromuscular facilitation of respiratory muscles and inspiratory muscle training are effective in children with Down syndrome on improving respiratory muscle strength, chest expansion, spirometry and functional capacity with superior effect of proprioceptive neuromuscular facilitation.

Ocular Phenotype Associated with DYRK1A Variants

Dual-specificity tyrosine phosphorylation-regulated kinase 1A or DYRK1A, contributes to central nervous system development in a dose-sensitive manner. Triallelic DYRK1A is implicated in the neuropathology of Down syndrome, whereas haploinsufficiency causes the rare DYRK1A-related intellectual disability syndrome (also known as mental retardation 7). It is characterised by intellectual disability, autism spectrum disorder and microcephaly with a typical facial gestalt. Preclinical studies elucidate a role for DYRK1A in eye development and case studies have reported associated ocular pathology. In this study families of the DYRK1A Syndrome International Association were asked to self-report any co-existing ocular abnormalities. Twenty-six patients responded but only 14 had molecular confirmation of a DYRK1A pathogenic variant. A further nineteen patients from the UK Genomics England 100,000 Genomes Project were identified and combined with 112 patients reported in the literature for further analysis. Ninety out of 145 patients (62.1%) with heterozygous DYRK1A variants revealed ocular features, these ranged from optic nerve hypoplasia (13%, 12/90), refractive error (35.6%, 32/90) and strabismus (21.1%, 19/90). Patients with DYRK1A variants should be referred to ophthalmology as part of their management care pathway to prevent amblyopia in children and reduce visual comorbidity, which may further impact on learning, behaviour, and quality of life.

Vestibular function in adults with intellectual disabilities: feasibility and outcome of a vestibular screening protocol in Special Olympics athletes

OBJECTIVE

This study aimed to evaluate the feasibility of a well-adapted vestibular screening battery to objectively examine the (peripheral) vestibular function, and to explore the characteristics of potential vestibular deficits in the adult ID population.

DESIGN

Cross-sectional study design.

STUDY SAMPLE

Compared to an age- and gender-weighted control group, a heterogeneous group of forty-five adults with ID participated in the vestibular screening at the National Games of Special Olympics Belgium (2019), which consisted of a bone conduction cervical Vestibular Evoked Myogenic Potential (cVEMP) measurement and video Head Impulse Test (vHIT).

RESULTS

The screening battery appeared to be feasible in the majority of the participants (cVEMP: 92%; vHIT: 72%). Overall, the occurrence of abnormal cVEMP and vHIT responses was significantly higher in the ID group, with significantly lower corrected peak-to-peak cVEMP amplitudes (p < 0.001), lower vHIT gains (p < 0.001), and higher cVEMP and vHIT asymmetry ratios in the ID group (p = 0.008 and p < 0.001 resp.).

CONCLUSIONS

Vestibular assessment using the cVEMP and vHIT technique shows a promising feasibility in adults with ID. In addition, this study suggests that people with ID exhibit an increased prevalence of (peripheral) vestibular deficits relative to the general population.

Cell Development Deficiency and Gene Expression Dysregulation of Trisomy 21 Retina Revealed by Single-Nucleus RNA Sequencing

Retina is a crucial tissue for capturing and processing light stimulus. It is critical to describe the characteristics of retina at the single-cell level for understanding its biological functions. A variety of abnormalities in terms of morphology and function are present in the trisomy 21 (T21) retina. To evaluate the consequences of chromosome aneuploidy on retina development, we identified the single-cell transcriptional profiles of a T21 fetus and performed comprehensive bioinformatic analyses. Our data revealed the diversity and heterogeneity of cellular compositions in T21 retina, as well as the abnormal constitution of T21 retina compared to disomic retina. In total, we identified seven major cell types and several subtypes within each cell type, followed by the detection of corresponding molecular markers, including previously reported ones and a series of novel markers. Through the analysis of the retinal differentiation process, subtypes of retinal progenitor cells (RPCs) exhibiting the potential of different retinal cell-type commitments and certain Müller glial cells (MGs) with differentiating potency were identified. Moreover, the extensive communication networks between cellular types were confirmed, among which a few ligand–receptor interactions were related to the formation and function of retina and immunoregulatory interactions. Taken together, our data provides the first ever single-cell transcriptome profiles for human T21 retina, which facilitates the understanding on the dosage effects of chromosome 21 on the development of retina.

The burden of chronic disease, multimorbidity, and polypharmacy in adults with Down syndrome

Data on clinical characteristics of adults with Down syndrome (DS) are limited and the clinical phenotype of these persons is poorly described. This study aimed to describe the occurrence of chronic diseases and pattern of medication use in a population of adults with DS. Participants were 421 community dwelling adults with DS, aged 18 years or older. Individuals were assessed through a standardized clinical protocol. Multimorbidity was defined as the occurrence of two or more chronic conditions and polypharmacy as the concomitant use of five or more medications. The mean age of study participants was 38.3 ± 12.8 years and 214 (51%) were women. Three hundred and seventy-four participants (88.8%) presented with multimorbidity. The most prevalent condition was visual impairment (72.9%), followed by thyroid disease (50.1%) and hearing impairment (26.8%). Chronic diseases were more prevalent among participants aged >40 years. The mean number of medications used was 2.09 and polypharmacy was observed in 10.5% of the study sample. Psychotropic medications were used by a mean of 0.7 individuals of the total sample. The high prevalence of multimorbidity and the common use of multiple medications contributes to a high level of clinical complexity, which appears to be similar to the degree of complexity of the older non-trisomic population. A comprehensive and holistic approach, commonly adopted in geriatric medicine, may provide the most appropriate care to persons with DS as they grow into adulthood.

Anterior chamber dimensions, angles and pupil diameter in patients with Down syndrome: A comparative population-based study

Purpose

To study the anterior chamber (AC) dimensions, angles and pupil diameter (PD) in patients with Down syndrome compared to normal controls.

Methods

Prospective study is comparing the AC parameters in patients with Down syndrome aged 10-30 years and age-matched controls. Extracted indices included average anterior chamber depth on the 2-mm ring (ACD-2 mm), 4-mm ring (ACD-4 mm), at the corneal apex from the endothelium (endo-ACD), at the corneal apex from the epithelium (epi-ACD), anterior chamber volume (ACV), mean anterior chamber angle (ACA), and PD measured by Pentacam.

Results

Data from 202 patients with Down syndrome (age 17.2 ± 4.8 years) were compared with 190 normal controls (age 17.2 ± 4.5 years). In Down and normal groups, mean ± SD were 2.51 ± 0.31 and 2.83 ± 0.34 mm for ACD-2 mm, 1.65 ± 0.30 and 1.93 ± 0.31 mm for ACD-4 mm, and 3.03 ± 0.29 and 3.24 ± 0.26 mm for endo-ACD, 3.54 ± 0.29 and 3.80 ± 0.26 mm for epi-ACD, mean 169.31 ± 30.38 and 200.17 ± 33.20 mm³ for ACV, 40.69 ± 4.50 and 39.97 ± 4.12° for ACA, and 2.79 ± 0.62 and 3.59 ± 0.80 mm for PD, respectively (all P < 0.001). None of the studied indices significantly correlated with age, except for ACA (P = 0.011). All parameters, except for PD, were significantly higher in males compared to females (all P < 0.001). Temporal ACA was significantly wider in male subjects (44.61 ± 6.52 vs. 42.24 ± 6.52°; P < 0.001).

Conclusion

The AC in patients with Down syndrome is smaller than normal individuals. AC in females with Down syndrome is smaller than males, and the narrower ACA is attributable to the difference in the temporal angle and not the ACA in other meridians.

Down syndrome

Trisomy 21, the presence of a supernumerary chromosome 21, results in a collection of clinical features commonly known as Down syndrome (DS). DS is among the most genetically complex of the conditions that are compatible with human survival post-term, and the most frequent survivable autosomal aneuploidy. Mouse models of DS, involving trisomy of all or part of human chromosome 21 or orthologous mouse genomic regions, are providing valuable insights into the contribution of triplicated genes or groups of genes to the many clinical manifestations in DS. This endeavour is challenging, as there are >200 protein-coding genes on chromosome 21 and they can have direct and indirect effects on homeostasis in cells, tissues, organs and systems. Although this complexity poses formidable challenges to understanding the underlying molecular basis for each of the many clinical features of DS, it also provides opportunities for improving understanding of genetic mechanisms underlying the development and function of many cell types, tissues, organs and systems. Since the first description of trisomy 21, we have learned much about intellectual disability and genetic risk factors for congenital heart disease. The lower occurrence of solid tumours in individuals with DS supports the identification of chromosome 21 genes that protect against cancer when overexpressed. The universal occurrence of the histopathology of Alzheimer disease and the high prevalence of dementia in DS are providing insights into the pathology and treatment of Alzheimer disease. Clinical trials to ameliorate intellectual disability in DS signal a new era in which therapeutic interventions based on knowledge of the molecular pathophysiology of DS can now be explored; these efforts provide reasonable hope for the future.

Impact of Pupil Diameter on Objective Refraction Determination and Predicted Visual Acuity

Purpose

Objective refraction based on wavefront aberration measures is a potential tool for patients unable to participate in a subjective refraction, but the selection of a single pupil diameter for determination of the objective refraction may pose challenges. The purpose of this study was to investigate the impact of pupil diameter on determination of objective refractions for adults with and without Down syndrome (DS) and predicted change in acuity with increasing pupil diameter.

Methods

Wavefront error was obtained from 27 adults with DS and 24 controls, and metric-optimized refractions were identified for 4- and 6-mm pupil diameters. Total dioptric difference between refractions for the two pupil sizes was calculated, and repeated measures analysis of variance was used to evaluate differences in refractions. Next, five control observers read acuity charts produced to simulate image quality of each subject if the same refraction was applied for both a 4- and 6-mm pupil diameter. A comparison of acuity with performance on a clear chart was used to calculate letters lost for each chart. Repeated measures analysis of variance was used to test for differences in letters lost from 4- and 6-mm diameters.

Results

The dioptric difference between refractions for 4- and 6-mm pupils was significantly greater in subjects with DS (0.51 diopters vs. 0.19 diopters, P = 0.0012). Letters lost for predicted acuity was less for the 4-mm diameter than 6 mm for charts representing DS eyes (6.5 letters vs. 11 letters, P < 0.0001), as well as for typical eyes (4.5 letters vs. 8 letters, P < 0.0001).

Conclusions

Differences between refractions by pupil diameter were similar to the repeatability of subjective refraction. Visual acuity differences were clinically small, suggesting similar performance for objective refractions with increasing pupil diameter.

Translational Relevance

This work quantifies the potential impact of pupil diameter change on the performance of wavefront optimized refractions in clinical patients.

Image Quality Metric Derived Refractions Predicted to Improve Visual Acuity Beyond Habitual Refraction for Patients With Down Syndrome

Purpose

To determine which optimized image quality metric (IQM) refractions provide the best predicted visual acuity (VA).

Methods

Autorefraction (AR), habitual refraction (spectacles, n = 23; unaided, n = 7), and dilated wavefront error (WFE) were obtained from 30 subjects with Down syndrome (DS; mean age, 30 years; range, 18–50). For each eye, the resultant metric value for 16 IQMs was calculated after >25000 sphero-cylindrical combinations of refraction were added to the measured WFE to generate residual WFE. The single refraction corresponding to each of the 16 optimized IQMs per eye was selected and used to generate acuity charts. Charts also were created for AR, habitual refraction, and a theoretical zeroing of all lower-order aberrations, and grouped into 10 sets with a clear chart in each set. Dilated controls (five observers per set) read each chart until five letters were missed on a high contrast monitor through a unit magnification telescope with a 3 mm pupil aperture. Average letters lost for the five observers for each chart was used to rank the IQMs for each DS eye.

Results

Average acuity for the best performing refraction for all DS eyes was within five letters (0.11 ± 0.05 logMAR) of the clear chart acuity. Optimized IQM refractions had ∼3.5 lines mean improvement from the habitual refraction (0.37 ± 0.22 logMAR, P < 0.001). Three metrics (Visual Strehl Ratio [VSX], VSX computed in frequency domain [VSMTF], and standard deviation of intensity values [STD]) identified refractions that were ranked first, or within 0.09 logMAR of first, in >98% of the eyes.

Conclusions

Optimized IQM refraction is predicted to improve VA in DS eyes based on control observers reading simulated charts.

Translational Relevance

Refractions identified through optimization of IQM may bypass some of the challenges of current refraction techniques for patients with DS. The optimized refractions are predicted to provide better VA compared to their habitual correction.

Dual sensory impairment among a cohort of older adults living in Ireland: A nested case-control study of the Irish Longitudinal Study on Ageing cohort

Background: Little information is available on the implications of hearing loss, visual impairment and dual sensory impairment among older adults with an intellectual disability (ID) living in Ireland and this paper aims to address the health concerns associated with sensory impairment among this population.  Methods: A representative sample of 753 persons aged 40 years and older at all levels of ID and full range of residential circumstances from the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing (IDS-TILDA) participants were matched with general older population TILDA participants on age, sex and geographic location within Ireland. Demographic data on samples included age, sex, visual impairment (yes/no), hearing impairment (yes/no) and dual sensory impairment (yes/no). For those with intellectual disability (ID) data was also gathered on level of intellectual disability, residence, needing assistance with activities of daily living (ADL) and instrumental activities of daily living, self-rated health, loneliness, doctor’s diagnosis of endocrine disease and of dementia and doctor’s report of two or more chronic health conditions. Bivariate analysis of associations between visual, hearing and dual sensory impairment with the measures of physical and mental health was completed and logistic regression analysis to generate adjusted odds ratios for associations between sensory impairment and physical and mental health conditions. Results: As compared to the matched general population participants, in participants with ID dual sensory impairment was more often associated with poor self-rated health, limitations with two or more ADLs, loneliness and multimorbidity. People with ID were 4.4 times more likely to be multimorbid if they were visually impaired compared with an odds ratio of 2.4 in TILDA participants. Conclusion: Previous studies found significant associations between hearing and visual impairment among older populations. Analysis here also suggests the burden of sensory impairment increases both with ID and then with level of ID

Genome-Wide Association Study Identifies a Susceptibility Locus for Comitant Esotropia and Suggests a Parent-of-Origin Effect

Purpose

To identify genetic variants conferring susceptibility to esotropia. Esotropia is the most common form of comitant strabismus, has its highest incidence in European ancestry populations, and is believed to be inherited as a complex trait.

Methods

White European American discovery cohorts with nonaccommodative (826 cases and 2991 controls) or accommodative (224 cases and 749 controls) esotropia were investigated. White European Australian and United Kingdom cohorts with nonaccommodative (689 cases and 1448 controls) or accommodative (66 cases and 264 controls) esotropia were tested for replication. We performed a genome-wide case-control association study using a mixed linear additive model. Meta-analyses of discovery and replication cohorts were then conducted.

Results

A significant association with nonaccommodative esotropia was discovered (odds ratio [OR] = 1.41, P = 2.84 × 10-09) and replicated (OR = 1.23, P = 0.01) at rs2244352 [T] located within intron 1 of the WRB (tryptophan rich basic protein) gene on chromosome 21 (meta-analysis OR = 1.33, P = 9.58 × 10-11). This single nucleotide polymorphism (SNP) is differentially methylated, and there is a statistically significant skew toward paternal inheritance in the discovery cohort. Meta-analysis of the accommodative discovery and replication cohorts identified an association with rs912759 [T] (OR = 0.59, P = 1.89 × 10-08), an intergenic SNP on chromosome 1p31.1.

Conclusions

This is the first genome-wide association study (GWAS) to identify significant associations in esotropia and suggests a parent-of-origin effect. Additional cohorts will permit replication and extension of these findings. Future studies of rs2244352 and WRB should provide insight into pathophysiological mechanisms underlying comitant strabismus.

Adaptive behaviour, executive function and employment in adults with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) demonstrate difficulties with aspects of executive function (EF) and adaptive behaviour across the lifespan. There is a current lack of information regarding how these difficulties relate to employment outcomes in adulthood. This study evaluated the adaptive behaviour and EF profiles of individuals with DS during early adulthood and the association between these areas of functioning and employment status.

METHODS

Parents or caregivers of primarily young adults with DS (n = 31; mean chronological age = 25.9 years; SD = 5.92) completed the Vineland Adaptive Behavior Scales - Second Edition the Behavior Rating Inventory of Executive Function - Adult version and a demographic questionnaire that requested information regarding adult employment status.

RESULTS

Findings indicated a distinct pattern of relative strengths and challenges in adaptive behaviour and EF. In addition, the EF sub-domain of working memory was a significant predictor of employment status.

CONCLUSIONS

Specific aspects of the DS cognitive profile may have an important influence on employment status in primarily young adults with DS. Implications for interventions are discussed.

Variability in Objective Refraction for Persons with Down Syndrome

PURPOSE

Down syndrome (DS) is associated with ocular and cognitive sequelae, which both have the potential to influence clinical measures of refractive error. This study compares variability of autorefraction among subjects with and without DS.

METHODS

Grand Seiko autorefraction was performed on 139 subjects with DS (age: 8-55, mean: 25 ± 9 yrs) and 138 controls (age: 7-59, mean: 25 ± 10 yrs). Subjects with three refraction measures per eye (DS: 113, control: 136) were included for analysis. Each refraction was converted to power vector notation (M, J0, J45) and a difference in each component (ΔM, ΔJ0, ΔJ45) was calculated for each refraction pairing. From these quantities, average dioptric strength ((Equation is included in full-text article.): square root of the sum of the squares of M, J0, and J45) and average dioptric difference ((Equation is included in full-text article.): square root of the sum of the squares of ΔM, ΔJ0, and ΔJ45) were calculated.

RESULTS

The DS group exhibited a greater median (Equation is included in full-text article.)(1Q: 1.38D M: 2.38D 3Q: 3.41D) than control eyes (1Q: 0.47D M: 0.96D 3Q: 2.75D) (P < .001). Likewise, the DS group exhibited a greater median (Equation is included in full-text article.)in refraction (1Q: 0.27D M: 0.42D 3Q: 0.78D) than control eyes (1Q: 0.11D M: 0.15D 3Q: 0.23D) (P < .001) with 97.1% of control eyes exhibiting (Equation is included in full-text article.)≤0.50D, compared to 59.3% of DS eyes. An effect of (Equation is included in full-text article.)on (Equation is included in full-text article.)was not detected (P = .3009) nor was a significant interaction between (Equation is included in full-text article.)and group detected (P = .49).

CONCLUSIONS

In the current study, comparing three autorefraction readings, median total dioptric difference with autorefraction in DS was 2.8 times the levels observed in controls, indicating greater potential uncertainty in objective measures of refraction for this population. The analysis demonstrates that J45 is highly contributory to the observed variability.

The burden of trisomy 21 disrupts the proteostasis network in Down syndrome

Down syndrome (DS) is a genetic disorder caused by trisomy of chromosome 21. Abnormalities in chromosome number have the potential to lead to disruption of the proteostasis network (PN) and accumulation of misfolded proteins. DS individuals suffer from several comorbidities, and we hypothesized that disruption of proteostasis could contribute to the observed pathology and decreased cell viability in DS. Our results confirm the presence of a disrupted PN in DS, as several of its elements, including the unfolded protein response, chaperone system, and proteasomal degradation exhibited significant alterations compared to euploid controls in both cell and mouse models. Additionally, when cell models were treated with compounds that promote disrupted proteostasis, we observed diminished levels of cell viability in DS compared to controls. Collectively our findings provide a cellular-level characterization of PN dysfunction in DS and an improved understanding of the potential pathogenic mechanisms contributing to disrupted cellular physiology in DS. Lastly, this study highlights the future potential of designing therapeutic strategies that mitigate protein quality control dysfunction.

Chromosome-wise Protein Interaction Patterns and Their Impact on Functional Implications of Large-Scale Genomic Aberrations

Gene copy-number changes influence phenotypes through gene-dosage alteration and subsequent changes of protein complex stoichiometry. Human trisomies where gene copy numbers are increased uniformly over entire chromosomes provide generic cases for studying these relationships. In most trisomies, gene and protein level alterations have fatal consequences. We used genome-wide protein-protein interaction data to identify chromosome-specific patterns of protein interactions. We found that some chromosomes encode proteins that interact infrequently with each other, chromosome 21 in particular. We combined the protein interaction data with transcriptome data from human brain tissue to investigate how this pattern of global interactions may affect cellular function. We identified highly connected proteins that also had coordinated gene expression. These proteins were associated with important neurological functions affecting the characteristic phenotypes for Down syndrome and have previously been validated in mouse knockout experiments. Our approach is general and applicable to other gene-dosage changes, such as arm-level amplifications in cancer.

Cataract surgery outcomes in adult patients with Down's syndrome

PURPOSE

To describe the outcomes of cataract surgery in adult patients with Down's syndrome at a tertiary eye hospital in Hong Kong.

METHODS

Retrospective case-file analysis was performed to identify patients with Downs's syndrome who underwent cataract surgery between January 2002 and December 2012. Morphology of cataract, associated ocular features and surgical and visual outcomes were analysed.

RESULTS

Cataract surgery was performed in 33 eyes of 20 patients (12 males, 8 females, mean age 42.9±10.6 years) over a 10-year period. Nine patients (9/20, 45.0%) had bilateral cataracts at the time of diagnosis. White cataracts were noted in 12 eyes of 10 patients (12/33, 36.3%) at the time of presentation. Associated ocular problems included myopic maculopathy (18 eyes, 54.5%), keratoconus (12 eyes, 36.3%), nystagmus (2 eyes, 6.0%), corneal scar (2 eyes, 6.0%) and glaucoma (2 eyes, 6.0%). Five eyes (15.1%) underwent extracapsular cataract extraction whereas a phacoemulsification was performed in 28 (84.9%) eyes. Intraocular lens implantation was performed in 32/33 eyes. The most common postoperative complication was posterior capsular opacification (8 eyes, 24.2%). The mean best-corrected visual acuity improved from 0.07±0.11 preoperatively to 0.17±0.19 at 3 months postoperatively (p=0.000).

CONCLUSIONS

A high incidence of bilateral cataracts as well as white cataracts was observed in patients with Down's syndrome in our study. Although the surgical outcomes of cataract surgery were good, the visual outcomes were suboptimal in our cases due to associated ocular comorbidities.