Strabismus and binocular function in children with Down syndrome. A population-based, longitudinal study

Sources of reduced visual acuity and spectacle treatment options for individuals with Down syndrome: Review of current literature

Individuals with Down syndrome are known to have a greater prevalence of ocular conditions such as strabismus, nystagmus, elevated refractive error, poor accommodative function, elevated higher-order optical aberrations and corneal abnormalities. Related to these conditions, individuals with Down syndrome commonly have reduced best-corrected visual acuity at both far and near viewing distances across their lifespan. This review summarises the various optical sources of visual acuity reduction in this population and describes clinical trials that have evaluated alternative spectacle prescribing strategies to minimise these optical deficits. Although refractive corrections may still have limitations in their ability to normalise visual acuity for individuals with Down syndrome, the current literature provides evidence for eye care practitioners to consider in their prescribing practices for this population to maximise visual acuity. These considerations include accounting for the presence of elevated higher-order aberrations when determining refractive corrections and considering bifocal lens prescriptions, even for young children with Down syndrome.

Ciliary muscle and anterior segment characteristics in pre-presbyopic adults with Down syndrome

PURPOSE

Previous research has shown that accommodation deficits are common in individuals with Down syndrome (DS), but the origin and mechanisms behind these deficits are still unknown. The aim of this study was to investigate the characteristics of different ocular structures involved in accommodation, in particular the ciliary muscle (CM), in a population of individuals with DS to further understand this deficit and its mechanisms.

METHODS

Thirty-two volunteer participants of pre-presbyopic age with (n = 16) and without DS (n = 16) were recruited. Temporal and nasal images of the CM were acquired using anterior segment optical coherence tomography (AS-OCT) while participants fixated an eccentrically located target. Analysis of CM parameters was undertaken using validated semi-automated software. Axial length, anterior chamber depth, lens thickness and corneal curvature were obtained with the Topcon Aladdin Optical Biometer and Corneal Topographer. Non-cycloplegic refractive error and accommodative ability were obtained with an open-field autorefractor and dynamic retinoscopy, respectively. Independent t-tests were conducted to determine differences in CM and other anterior segment parameters between participants with and without DS.

RESULTS

No significant differences were found in the CM parameters studied between participants with and without DS (p > 0.05). In contrast, significant differences were found in visual acuity (p < 0.001), accommodative response (p < 0.001) and corneal curvature (K1 p = 0.003 and K2 p < 0.001) between participants with and without DS.

CONCLUSIONS

Despite having poorer accommodation, pre-presbyopic adults with DS do not have a different CM morphology to that found in typically developing adults. These findings suggest that the accommodative deficit found in this population is not due to a mechanical deficit of the CM.

Visual Acuity Prediction Based on Different Refraction Types For Patients With Down Syndrome

Purpose

The purpose of this study was to determine if control observers can be used as surrogates to predict visual acuity (VA) of patients with Down syndrome (DS).

Methods

Thirty adults with DS were enrolled in a clinical trial testing three refraction types: clinical refraction and two using wavefront aberration measures to optimize the metrics pupil fraction tessellated (PFSt) and visual Strehl ratio (VSX). Monocular VA was obtained through habitual refractions and each experimental refraction type. Five controls without DS viewed acuity charts simulating the retinal image produced when the corrections for each DS eye are worn, performing VA and scoring image quality of each chart. Group median VA (DS versus controls) were compared for each refraction type, and control image quality scores were compared to corresponding VA across refraction types.

Results

Median VA for participants with DS ranged from 0.46 logMAR (interquartile range [IQR] = 0.32 to 0.54) with habitual correction to 0.36 logMAR (IQR = 0.28 to 0.54) with VSX, whereas controls ranged from 0.37 logMAR (IQR = 0.29 to 0.42) with habitual correction to 0.01 logMAR (IQR = -0.02 to 0.05) with VSX. Overall image quality scores were best for PFSt and VSX and showed a strong linear relationship with control VA (r = -0.91, P < 0.001), and a lesser correlation with DS VA (r = -0.33, P < 0.001).

Conclusions

Using surrogate observers to judge image quality simulations of eyes with DS did not predict actual VA, suggesting additional, non-optical factors may be limiting VA in individuals with DS.

Translational Relevance

Findings may guide clinical refraction practices for patients with DS.

Is the prolongation latency of visual evoked potentials a pathological sign in children with Down’s syndrome without ocular abnormalities? Case–control study of children with Down’s syndrome

Objective

To evaluate retino-cortical function in children with Down’s syndrome (DS) and no evident ocular abnormalities beyond mild refractive error, by recording visual evoked potentials (VEP) in response to pattern-reversal stimuli and comparing to those of age-matched healthy controls.

Methods and analysis

All the children with DS registered at Split-Dalmatia County who met inclusion criteria of no ocular abnormalities and with refraction error between −0.5 and +2.0 D, and their age-matched healthy controls were included in the study (n=36 children, N=72 eyes, for both groups, respectively, with the same age of 9±2 years). Transient VEP was recorded and the waves with a positive peak as a response to a pattern-reversal stimulus, were analysed. The peak P100 latency, defined as the time from the stimulus onset to the main positive peak, and peak to peak amplitudes were measured.

Results

While P100 wave amplitudes were comparable between two groups (p=0.804), P100 latencies were from 4.3 to 28.5 ms longer in children with DS (p<0.001). Interocular latency difference between a VEP dominant and an inferior eye was pronounced in healthy (1.2 ms (0.2–4.0), but was almost diminished in children with DS (0.3 ms (0.1–0.5), p<0.001).

Conclusion

Our study has demonstrated that VEP response is divergent in children with DS compared with their age-matched healthy controls, indicating possible structural or functional abnormalities of the visual cortex. As VEP results are helpful in the diagnosis and treatment planning of vision-related disorders, we should reconsider the use of common VEP diagnostic criteria in subpopulation of children with DS.

The Ophthalmic Manifestations of Down Syndrome

Down Syndrome is one of the most common chromosomal conditions in the world, affecting an estimated 1:400-1:500 births. It is a multisystem genetic disorder but has a wide range of ophthalmic findings. These include strabismus, amblyopia, accommodation defects, refractive error, eyelid abnormalities, nasolacrimal duct obstruction, nystagmus, keratoconus, cataracts, retinal abnormalities, optic nerve abnormalities, and glaucoma. These ophthalmic conditions are more prevalent in children with Down Syndrome than the general pediatric population, and without exception, early identification with thoughtful screening in this patient population can drastically improve prognosis and/or quality of life.

Conventional surgery versus botulinum toxin injection for the management of esotropia in children with Down syndrome

PURPOSE

To compare the success rates of strabismus surgery and botulinum toxin injection (BTX) in treating esotropia in patients with Down syndrome (DS).

METHODS

This multicenter retrospective cohort study included all consecutive patients having DS with esotropia between 2014 and 2021 at King Abdullah Specialist Children Hospital, King Abdullah International Medical Research Center, and King Khaled Eye Specialist Hospital, Saudi Arabia. We divided the patients into two groups according to interventions. Success was defined as angle of deviation of <10^Δ at final visit.

RESULTS

A total of 53 patients were included: 23 in the surgery group and 30 in the BTX group. There were no significant differences between groups with regard to age, sex, diagnosis, spherical equivalent, and preoperative deviation angle. Before the intervention, the median angle of deviation was 30.0^Δ (IQR, 30^Δ-45^Δ) in the surgery group and 37.5^Δ (IQR, 28.8^Δ-50.0^Δ) in the BTX group (P = 0.802). Postoperatively, the median (IQR) deviation angle was 0.0^Δ (0.0^Δ-16.0^Δ) in the surgery group and 22.5^Δ (6.75^Δ-30.0^Δ) in the BTX group (P = 0.006). The success rate in the surgery and BTX groups was 65% and 30%, respectively (P = 0.011). Two patients developed dissociated vertical deviation in the surgery group. One patient presented consecutive exotropia and one inferior oblique overaction in the BTX group.

CONCLUSIONS

In this study, conventional surgery showed a higher success rate than BTX in the management of esotropia.

Systemic and Ophthalmic Manifestations in Different Types of Refractive Errors in Patients with Down Syndrome

Background and Objective: This study aims to investigate the prevalence of systemic and ophthalmic manifestations in different refractive groups in children and young adults with Down syndrome (DS). Materials and Methods: The study was a population-based, cross-sectional study that included 141 Caucasian children and young adults with DS. They were classified into the following three groups: myopia DS group (37 subjects, mean age 15.8 years), emmetropia DS group (41 subjects, mean age 11.7 years) and hyperopia DS group (63 subjects, mean age 10.9 years). The participants underwent inspection, slit-lamp examination, cycloplegic refraction, ocular alignment and ocular motility examination. Ten systemic manifestations were analyzed. Results: There was no difference in the prevalence of any systemic manifestations between the groups. Considering the ophthalmic manifestations, there was statistical difference in the distribution of proportions among the three groups for nystagmus (p = 0.011), iris-stromal atrophy (p = 0.048) and strabismus (p = 0.031). The prevalence of strabismus in our DS myopia group was 35.1%, and in DS hyperopia group 38.1%. Conclusions: The results of our study suggest that DS children and young adults with any refractive error do not have a higher chance of additional systemic manifestations. Myopia in DS was associated with a higher prevalence of nystagmus and iris stromal atrophy, whereas astigmatism was found to be more frequent in hyperopia.

Down syndrome: a review of ocular manifestations

Down syndrome is the most common genetically mediated intellectual disability. Although many physiologic and pathologic features of Down syndrome are discussed at length in the literature, the ocular manifestations of Down syndrome have seldom been discussed in a comprehensive fashion. Given that Down syndrome has ocular manifestations from the front to the back of the eye, it is important for physicians to become familiar with these manifestations, especially given the prevalence of Down syndrome. This review aims to discuss the varied ophthalmologic manifestations of Down syndrome – including strabismus, amblyopia, nystagmus, accommodation deficits, nasolacrimal duct obstruction, keratoconus, optic nerve pathology, neoplastic disease, and retinal pathology – to facilitate better care and visual outcomes in this important patient population.

Neuro-Ophthalmological Manifestations in Children with Down Syndrome: Current Perspectives

Down syndrome, caused by an extra copy of all or part of chromosome 21, is the most prevalent intellectual disability of genetic origin. Among numerous comorbidities which are part of the phenotype of individuals with Down syndrome, ocular problems appear to be highly prevalent. Neuro-ophthalmological manifestations, such as ocular alignment and motility disturbances, amblyopia, hypoaccommodation or optic nerve abnormalities, and other organic ocular anomalies frequently reported in Down syndrome, may lead to an overall decrease in visual acuity. Although numerous studies have reported ocular anomalies related to Down syndrome, it remains challenging to determine the impact of each anomaly upon the decreased visual acuity, as most such individuals have more than one ocular problem. Even in children with Down syndrome and no apparent ocular defect, visual acuity has been found to be reduced compared with typically developing children. Pediatric ophthalmological examination is a critical component of a multidisciplinary approach to prevent and treat ocular complications and improve the visual outcome in children with Down syndrome. This narrative review aims to provide a better understanding of the neuro-ophthalmological manifestations and discuss the current ophthalmological management in children with Down syndrome.

Visual and binocular status of Down syndrome children in Malaysia

BACKGROUND

Down syndrome is a common chromosomal anomaly. Few reported studies make reference to the ocular status in Asian children with Down syndrome. The purpose of this study was to determine the visual and binocular status of a sample of Down syndrome children in Malaysia.

METHODS

A total of 73 Malaysian children with Down syndrome (38 boys and 35 girls) in the Kuala Lumpur area aged one to 12 years were examined. Cycloplegic refraction was performed on each eye and binocular visual acuity was assessed using the Cardiff acuity card or the LogMAR chart. Binocular functions were assessed using the cover test and Lang's stereo acuity test.

RESULTS

The mean age of the subjects was 6.01 +/- 3.41 years. Refraction of the right eye showed that 10 per cent of the subjects were myopic, 20 per cent were hyperopic and 70 per cent had no significant refractive error. The mean spherical equivalent was +0.92 +/- 2.32 DS for the right eye and +0.99 +/- 2.21 DS for the left. The mean of binocular LogMAR VA was 0.36 +/- 0.22 (6/12). Cover test revealed that 21 subjects had strabismus (of those, 33 per cent had unilateral esotropia, 52 per cent had alternating esotropia, nine per cent had unilateral exotropia and five per cent had alternating exotropia). Only 22 subjects gave clear positive response to the stereotest. Other ocular findings included ptosis (one per cent), abnormal head posture (seven per cent) and nystagmus (six per cent).

CONCLUSION

Malaysian children with Down syndrome have a high incidence of refractive error and strabismus. Regular visual examination is important so that corrective lenses can be prescribed to improve vision and to enhance the quality of life of these children in Malaysia.

Recurrent Rare Copy Number Variants Increase Risk for Esotropia

Purpose

To determine whether rare copy number variants (CNVs) increase risk for comitant esotropia.

Methods

CNVs were identified in 1614 Caucasian individuals with comitant esotropia and 3922 Caucasian controls from Illumina SNP genotyping using two Hidden Markov model (HMM) algorithms, PennCNV and QuantiSNP, which call CNVs based on logR ratio and B allele frequency. Deletions and duplications greater than 10 kb were included. Common CNVs were excluded. Association testing was performed with 1 million permutations in PLINK. Significant CNVs were confirmed with digital droplet polymerase chain reaction (ddPCR). Whole genome sequencing was performed to determine insertion location and breakpoints.

Results

Esotropia patients have similar rates and proportions of CNVs compared with controls but greater total length and average size of both deletions and duplications. Three recurrent rare duplications significantly (P = 1 × 10⁻⁶) increase the risk of esotropia: chromosome 2p11.2 (hg19, 2:87428677-87965359), spanning one long noncoding RNA (lncRNA) and two microRNAs (OR 14.16; 95% confidence interval [CI] 5.4–38.1); chromosome 4p15.2 (hg19, 4:25554332-25577184), spanning one lncRNA (OR 11.1; 95% CI 4.6–25.2); chromosome 10q11.22 (hg19, 10:47049547-47703870) spanning seven protein-coding genes, one lncRNA, and four pseudogenes (OR 8.96; 95% CI 5.4–14.9). Overall, 114 cases (7%) and only 28 controls (0.7%) had one of the three rare duplications. No case nor control had more than one of these three duplications.

Conclusions

Rare CNVs are a source of genetic variation that contribute to the genetic risk for comitant esotropia, which is likely polygenic. Future research into the functional consequences of these recurrent duplications may shed light on the pathophysiology of esotropia.

In-vivo anterior segment OCT imaging provides unique insight into cerulean blue-dot opacities and cataracts in Down syndrome

Down syndrome (DS) is frequently associated with cataract, but there remains scant information about DS cataract morphology. Supra-nuclear cataracts in DS have been proposed as indicative of beta-amyloid (Aβ) aggregation and thus potential biomarkers for Alzheimer’s (AD). This study employed anterior segment OCT (AS-OCT) and slit-lamp (SL) photography to image the crystalline lens in DS, compared with adult controls. Lens images were obtained post-dilation. Using MATLAB, AS-OCT images were analysed and lens opacities calculated as pixel intensity and area ratios. SL images were classified using LOCS III. Subjects were n = 28 DS (mean ± SD 24.1 ± 14.3years), and n = 36 controls (54.0 ± 3.4years). For the DS group, AS-OCT imaging revealed the frequent presence of small dot opacities (27 eyes, 50%) in the cortex and nucleus of the lens, covering an area ranging from 0.2–14%. There was no relation with age or visual acuity and these dot opacities (p > 0.5) and they were not present in any control lenses. However, their location and morphology does not coincide with previous reports linking these opacities with Aβ accumulation and AD. Four participants (14%) in the DS group had clinically significant age-related cataracts, but there was no evidence of early onset of age-related cataracts in DS.

Strabismus Surgery for Esotropia, Down Syndrome and Developmental Delay; Is an Altered Surgical Dose Required? A Literature Review

Background and Purpose:

There is a high rate of strabismus, in particular esotropia, in children with Down syndrome or developmental delay, which frequently requires surgical correction. A paper in 1994 advocated that the surgical dose be adjusted due to an altered response in these children. The aim of this literature review is to evaluate the available evidence to establish whether an altered surgical approach is required in either population.

Methods:

A literature review was conducted using PubMed and Web of Knowledge. Only English language papers were eligible for inclusion. The papers were collated in chronological order for analysis, and their references searched for further relevant papers. Forward citation searches were also undertaken.

Results:

A 2 × 2 comparison is made between publications on Down syndrome (in isolation) and developmental delay populations (including Down syndrome) with adjusted versus non-adjusted surgery. Published surgical success rates on esotropia from unaltered surgical doses range from 62.0%–85.7% (four papers) in the Down syndrome cohort, with none of the adjusted surgeries having a successful outcome. Surgical success rates from adjusted surgical doses in developmental delay cohort range from 37.5%–86.0% (seven papers), with one unadjusted surgical success rate of 76.0%. The results across the studies are summarised in a table and discussed.

Conclusions:

An exaggerated surgical effect in individuals with developmental delay has been reported, and this population may benefit from a reduced surgical dose. Published research does not support giving a reduced surgical dose in individuals with Down syndrome, but more research needs to be done to make a definitive conclusion.

Bifocals reduce strabismus in children with Down syndrome: Evidence from a randomized controlled trial

PURPOSE

Children with Down syndrome (DS) more often have strabismus, refractive errors, accommodative lags and reduced visual acuity (VA) than typically developing children. In this study, we compare the effects of bifocal glasses with those of unifocal glasses in children with DS. Changes in angle of strabismus, accommodation and refractive error were analysed in this paper.

METHODS

In a multicentre randomized controlled trial, 119 children with DS, aged 2-16, were randomly allocated for bifocal or unifocal glasses (with full correction of refractive error in cycloplegia). The 15 centres, all in the Netherlands, followed the participants for 1 year. Changes in refractive error, accommodative accuracy, strabismus, binocularity and stereopsis were compared across 4 subsequent visits.

RESULTS

Refractive errors and accommodative errors showed no significant change throughout the course of our study in either intervention group. The manifest angle of strabismus, however, reduced significantly in the bifocal group. This improvement was observed shortly after the children received their new correction (~6 weeks) (linear regression: t = 3.652, p < 0.001) and remained present in the final measurements after 1 year (linear regression: t = 3.604, p < 0.001). The percentage of children with positive binocularity and stereo tests showed no significant differences between the groups.

CONCLUSION

Bifocals with full correction of refractive error reduce the manifest angle of strabismus within a few weeks. No effects on accommodation, refractive error, stereopsis and binocularity occurred over the course of 1 year.

Ultrastructural changes of extraocular muscles in strabismus patients

Strabismus is an ocular disorder characterized by partial or complete inability to keep eye alignment. It represents a very common ocular problem at ophthalmology clinics worldwide. The current study aimed to show the most encountered ultrastructural changes in extraocular muscles (EOMs) collected from patients with different forms of strabismus. Nine specimens of EOMs were collected from five patients during strabismus correction surgery and processed for light and electron microscopy examinations. Histologically, skeletal muscle fibers in normal EOMs appeared tight and normally arranged with clear striations. In strabismic muscles, the fibers appeared disarranged, and atrophied, swollen and disintegrated in some situations. By transmission electron microscopy, normal EOMs were formed of skeletal muscle fibers with intact basal membrane and sarcolemma, tightly aligned myofibrils with well-arranged sarcomeres, Z line and H zone, and normally distributed mitochondria. On the other hand, strabismic EOMs revealed vacuolation and degeneration of myofibrils, accumulation of lipid droplets, subsarcolemmal inclusions and clustering of mitochondria. EOMs obtained from a Down syndrome patient with V-pattern infantile esotropia showed extensive vacuolation and disintegration of myofibrils, and extra- and intracellular deposition of collagen fibers. Interestingly, some skeletal muscle cells exhibited features of autophagic cell death with a trial of engulfing process by neighboring cells. In conclusion, our study traces some characteristic ultrastructural changes in strabismic EOMs, most notably, extensive vacuolation, clustering of mitochondria, degeneration of myofibrils and autophagic changes. These changes might be emphasized as possibly secondary to strabismus.

Effects of bifocals on visual acuity in children with Down syndrome: a randomized controlled trial

Purpose

Children with Down syndrome (DS) typically have reduced visual acuity (VA) and accommodation lag, but it is unclear whether prescribed glasses should correct both distance VA (DVA) and near VA (NVA) due to the lack of RCTs. We therefore conducted a multicentre RCT to compare the effects of bifocals designed to correct both DVA and NVA with distance‐correcting unifocal glasses in children with DS.

Methods

A total of 119 children with DS, aged 2–16, were randomly allocated for bifocal or unifocal glasses (with full correction of refraction error in cycloplegia) in 14 Dutch hospitals and followed during 1 year. VA data were analysed in relation to baseline VA with ancova.

Results

Treatment groups showed no differences at baseline. Shortly after receiving new corrections (~6 weeks), uncrowded NVA (bifocals 0.18 ± 0.33 LogMar; unifocals 0.09 ± 0.19 LogMar) and crowded NVA with bifocals (bifocals 0.13 ± 0.36 LogMar; unifocals 0.08 ± 0.33 LogMar) were significantly better than at baseline, but these short‐term improvements in NVA were not significantly different between the two treatments (p > 0.151). The 1‐year treatment differences were as follows: significantly larger improvement for bifocals compared to unifocals in both uncrowded NVA (bifocals 0.23 ± 0.29 LogMar, unifocals 0.12 ± 0.30 LogMar, p = 0.045) and crowded NVA (bifocals 0.31 ± 0.28 LogMar; unifocals 0.16 ± 0.30 LogMar, p = 0.017). Improvements in DVA were comparable (bifocals 0.07 ± 0.21 LogMar, unifocals 0.08 ± 0.22 LogMar, p = 0.565). Children with poor baseline VA improved more. Accommodation lag stayed unchanged.

Conclusion

After one year, bifocals with full correction of ametropia led to significantly larger improvement of both uncrowded NVA and crowded NVA in children with DS with accommodation lag compared to unifocals.

Near vision in individuals with Down syndrome: a vision screening study

OBJECTIVES

Children with Down syndrome are known to have reduced focusing ability for near vision (hypoaccommodation). Through a vision screening study we investigated the correlation between hypoaccommodation and near visual acuity in individuals with Down syndrome.

METHODS

A cross-sectional vision screening study was conducted on individuals with Down Syndrome. The screening was done in 4 city schools and 1 screening was conducted as a part of the Special Olympics Bharat program. In addition to the conventional vision screening tests, Nott dynamic retinoscopy was also performed. Both adults and children (age < 18 years) were included.

RESULTS

A total of 55 participants (33 children: age 6 to 17 years, 22 adults: age 18 to 41 years) with Down syndrome were screened. Twenty-two participants had visual impairment. Accommodative accuracy was assessed in 29 children and 13 adults. Accommodative lag ( ≥1.00D) was present in 12 children (41.37%) and 7 adults (53.84%). No correlation was found between the lag of accommodation and near visual acuity (ρ_Spearman = 0.15, p = 0.54). LogMAR near visual acuity was inversely correlated (ρ_Spearman = -0.841, p < 0.001) to the near viewing distance.

CONCLUSION

Near visual acuity by itself is not a sensitive indicator of accommodative dysfunction. In addition, a closer viewing distance may not indicate adequate amplitude of accommodation. These findings strongly suggest the need for including dynamic retinoscopy in the clinical practice while examining individuals with Down syndrome.

Ocular findings in Japanese children with Down syndrome: the course of visual acuity and refraction, and systemic and ocular anomalies

PURPOSE

To investigate the age-related development of refractive errors and changes of visual acuity (VA), and the systemic and ocular anomalies in Japanese children and young adults with Down syndrome (DS).

DESIGN

Retrospective cohort study.

SUBJECTS AND METHODS

This study involved 222 Japanese children and young adults with DS (age range: 3 months to 19 years) seen at the Department of Ophthalmology, Shiga Medical Center for Children, Shiga, Japan. The subjects were divided into the following six age groups: 1) infant (age 0 to <4 years), 2) preschool (age 4 to <7 years), 3) lower primary-school grades (age 7 to <10 years), 4) upper primary-school grades (age 10 to <13 years), 5) junior high school (age 13 to <16 years), and 6) late teen/young adults (age 16 to <20 years). Through examination of the subjects' medical charts, we investigated the development and changes of refractive errors and VA, best-corrected VA (BCVA), and systemic and ocular anomalies.

RESULTS

For vision testing, Teller Acuity Cards™ (Bernell Corporation) were used for the infants, and the Landolt ring was used for the school-age children. VA was found to develop with age. Mean BCVA was 0.19±0.17 logarithm of the minimum angle of resolution (mean age: 11.3±3.2 years). Mean of refractive errors was hyperopia in the infant (2.2±2.4 diopters [D] OD, 2.4±2.5D OS), yet became myopia to the junior high school (-0.3±4.4D OD, -0.2±4.4D OS).

CONCLUSION

Our findings revealed that in children and in late-teen and young-adult subjects with DS, VA slowly develops and that refractive errors requiring correction exist and are difficult to examine.

Vision in children with autism spectrum disorder: a critical review

Autism spectrum disorder (ASD) is a common neurodevelopmental condition with approximately 1-2 per cent prevalence in the population. The condition has lifelong effects for the individual and family, and early intervention and management helps maximise quality of life and outcomes. Many studies of vision in ASD have attempted to link the behavioural and sensory deficits in ASD with underlying visual processing. From this work, it is clear that individuals with ASD 'see' and process the world differently, but there remain gaps in our understanding. This review will summarise our current knowledge of key aspects of visual functions and the optometric profile of ASD. This includes findings regarding visual acuity and contrast sensitivity, refractive error, eye movements, binocular vision, near visual functions and retinal structure in ASD. From this, a pattern of knowledge emerges for children with ASD: we should expect normal visual acuity; there will likely be atypical eye movements and susceptibility for subtle visuo-motor deficits, there is an increased prevalence of strabismus; an increased likelihood of astigmatism and possibly other refractive errors; attention, crowding and task complexity will likely be problematic; and retinal structure and function may be compromised. Bringing this together, these findings highlight that further work is necessary, not only to understand how higher-level functions link to behaviours, but also to ensure there is a sound understanding of the building-blocks of vision to fully grasp the profile of visual processing as a whole in ASD. This review will give a translational viewpoint for clinicians, and underline the benefits of comprehensive vision care in ASD.

Determining the relative contribution of retinal disparity and blur cues to ocular accommodation in Down syndrome

Individuals with Down syndrome (DS) often exhibit hypoaccommodation alongside accurate vergence. This study investigates the sensitivity of the two systems to retinal disparity and blur cues, establishing the relationship between the two in terms of accommodative-convergence to accommodation (AC/A) and convergence-accommodation to convergence (CA/C) ratios. An objective photorefraction system measured accommodation and vergence under binocular conditions and when retinal disparity and blur cues were removed. Participants were aged 6–16 years (DS n = 41, controls n = 76). Measures were obtained from 65.9% of participants with DS and 100% of controls. Accommodative and vergence responses were reduced with the removal of one or both cues in controls (p < 0.007). For participants with DS, removal of blur was less detrimental to accommodative responses than removal of disparity; accommodative responses being significantly better when all cues were available or when blur was removed in comparison to when proximity was the only available cue. AC/A ratios were larger and CA/C ratios smaller in participants with DS (p < 0.00001). This study demonstrates that retinal disparity is the main driver to both systems in DS and illustrates the diminished influence of retinal blur. High AC/A and low CA/C ratios in combination with disparity-driven responses suggest prioritisation of vergence over accurate accommodation.

Down syndrome: An overview

Optometrists as primary eye care providers examine patients from diverse populations, including those with special needs such as Down syndrome. Down syndrome is a chromosomal abnormality associated with several health conditions including vision anomalies such as refractive, accommodative and vergence anomalies, as well as ocular pathology. In this article, a narrative review of Down syndrome including the background, historical perspective, aetiology and genetic mechanisms, types, epidemiology, as well as the physical and medical profile of Down syndrome is presented.Keywords: Down syndrome review; Trisomy 21; historical perspective; etiology; types and epidemiology; features; Optometrist

Trying to see, failing to focus: near visual impairment in Down syndrome

The majority of individuals with Down syndrome (DS) do not exhibit accurate accommodation, with the aetiology of this deficit unknown. This study examines the mechanism underlying hypoaccommodation in DS by simultaneously investigating the ‘near triad’ – accommodation, vergence and pupillary response. An objective photorefraction system measured accommodation, pupil size and gaze position (vergence) under binocular conditions while participants viewed an animated movie at 50, 33, 25 and 20 cm. Participants were aged 6–16 years (DS = 41, controls = 76). Measures were obtained from 59% of participants with DS and 99% of controls. Accommodative response was significantly less in DS (p < 0.001) and greater accommodative deficits were associated with worsening visual acuity (p = 0.02). Vergence responses were as accurate in DS as in controls (p = 0.90). Habitual pupil diameter did not differ between groups (p = 0.24) but reduced significantly with increasing accommodative demand in both participants with and without DS (p < 0.0001). This study is the first to report simultaneous binocular measurement of the near triad in DS demonstrating that hypoaccommodation is linked to poor visual acuity. Vergence responses were accurate indicating that hypoaccommodation cannot be dismissed as a failure to visually engage with near targets, but rather is a consequence of underlying neurological or physiological deficits.

Comparison of Whole Eye versus First-Surface Astigmatism in Down Syndrome

PURPOSE

Subjects with Down syndrome have structural differences in the cornea and lens, as compared with the general population. This study investigates objectively measured refractive and corneal astigmatism, as well as calculated internal astigmatism in subjects with and without Down syndrome.

METHODS

Refractive (Grand Seiko autorefraction) and anterior corneal astigmatism (difference between steep and flat keratometry obtained with Zeiss Atlas corneal topography) were measured in 128 subjects with Down syndrome (mean [±SD] age, 24.8 [±8.7] years) and 137 control subjects without Down syndrome (mean [±SD] age, 24.9 [±9.9] years), with one eye randomly selected for analysis per subject. Refractive astigmatism and corneal astigmatism were converted to vector notation (J0, J45) to calculate internal astigmatism (Refractive - Corneal) and then converted back to minus cylinder form.

RESULTS

Mean [±SD] refractive astigmatism was significantly greater in subjects with Down syndrome than in control subjects (-1.94 [±1.30] DC vs. -0.66 [±0.60] DC, t = -10.16, p < 0.001), as were mean corneal astigmatism (1.70 [±1.04] DC vs. 1.02 [±0.63] DC, t = 6.38, p < 0.001) and mean internal astigmatism (-1.07 [±0.68] DC vs. -0.77 [±0.41] DC, t = -4.21, p < 0.001). A positive linear correlation between corneal and refractive astigmatism was observed for both study populations for both the J0 and J45 vectors (p < 0.001 for all comparisons; R(2) range, 0.31 to 0.74). The distributions of astigmatism orientation differed significantly between the two study populations for comparisons of corneal and calculated internal astigmatism (χ(2), p < 0.007), but not refractive astigmatism (p = 0.46).

CONCLUSIONS

This study demonstrates that corneal astigmatism is predictive of overall refractive astigmatism in subjects with Down syndrome, as it is in the general population. The greater magnitudes of astigmatism and wider variation of astigmatism orientation in subjects with Down syndrome for refractive, corneal, and calculated internal astigmatism are likely attributable to previously reported differences in the structure of the cornea and internal optical components of the eye from that of the general population.

Effect of gestational age and birth weight on the risk of strabismus among premature infants

IMPORTANCE

Strabismus causes irreversible vision loss if not detected and treated early. It is unclear whether birth weight (BW) and gestational age (GA) are risk factors for strabismus.

OBJECTIVE

To estimate the effect of BW and GA on the likelihood of premature infants developing strabismus.

DESIGN, SETTING, AND PARTICIPANTS

In this longitudinal cohort analysis, we monitored a group of premature children from birth to determine the proportion that developed strabismus and the timing of the first strabismus diagnosis. Multivariable Cox regression analyses assessed the relationships of BW and GA with the development of strabismus. Regression models were adjusted for other risk factors for strabismus, sociodemographic factors, and ocular comorbidities. The analysis included 38,055 otherwise healthy children born prematurely who were enrolled for more than 6 months in a nationwide US managed care network between 2001 and 2011 in communities throughout the United States.

EXPOSURES

Birth weight less than 2000 g or GA of 32 weeks or less.

MAIN OUTCOMES AND MEASURES

Hazard ratios (HRs) for strabismus with 95% CIs.

RESULTS

Of 38,055 otherwise healthy children who were born prematurely, 583 received a diagnosis of strabismus later in life. The cumulative incidence of strabismus was 3.0% at 5 years. Controlling for GA and other covariates, infants born with BW less than 2000 g had a 61% increased hazard (HR, 1.61; 95% CI, 1.22-2.13) of developing strabismus. Controlling for BW and other covariates, there was no significant association between strabismus and GA (HR, 0.98; 95% CI, 0.69-1.38). Among premature infants with BW of less than 2000 g, a GA of 32 weeks or less conveyed no additional increased risk for developing strabismus relative to infants born after 32 weeks (HR, 1.27; 95% CI, 0.86-1.88). In contrast, among infants with a GA of 32 weeks or less, BW of less than 2000 g conveyed a 14-fold increase in the risk of strabismus relative to BW of 2000 g or more (HR, 14.39; 95% CI, 1.99-104.14).

CONCLUSIONS AND RELEVANCE

Independent of GA, very low BW conferred a large increase in strabismus risk among premature infants. In contrast, independent of BW, GA did not significantly affect the risk of strabismus. Updates to existing guidelines in the pediatric and ophthalmic literature should be considered, highlighting the importance of BW rather than GA and alerting clinicians about the need for careful monitoring of premature infants with low BW for strabismus.

Strabismus surgery for children with developmental delay

PURPOSE OF REVIEW

To describe recent evidence regarding the surgical approach of strabismus in children with various forms of developmental delay.

RECENT FINDINGS

There remains variability in surgical outcomes with or without dose adjustment in strabismus surgery for children with developmental delay. However, this should not deter one from performing surgery - even early surgery, as fusional potential remains possible, which can especially impact the quality of vision and quality of life in developmentally delayed children.Future prospective, comparative, long-term studies with larger sample sizes for strabismus surgery in children with developmental delay are still needed.

SUMMARY

Strabismus is one of the most common ophthalmologic findings in children with developmental delay. Surgical correction of strabismus in children with developmental delay is well tolerated and effective, although it remains slightly less predictable, which can depend on the specific type of delay or underlying neurological deficit. Careful consideration of types and severity of developmental delay and attempts to measure binocular potential can help guide the timing, dosage, and type of treatment.Reoperations tend to be more frequently encountered in this population, and this higher degree of variability should be addressed in the consent process.Considering adjusting the surgical dosage in this population, taking careful preoperative measurements, and checking for fusional potential should be taken into account when managing children with developmental delay.

Eyelash line resection for cilial entropion in patients with Down's syndrome

AIM

To describe a surgical procedure for excising the eyelash line to treat cilial entropion in patients with Down's syndrome.

METHODS

24 Down's patients with cilial entropion and medial epiblepharon underwent eyelash line resection bilaterally. The area and density of fluorescein staining of the superficial punctate keratopathy (SPK; 0=none to 3=wide or severe) and the frequency of spectacle wear (0=no wear to 2=all day wear) were evaluated prospectively.

RESULTS

The postoperative area and density of the SPK improved significantly in both eyes (p<0.001, p<0.001). The score of spectacle wear was 1.3 ± 0.8 preoperatively which improved significantly to 1.7 ± 0.5 after surgery (p=0.018). Five patients had a partial recurrence of misdirected eyelashes adjacent to the site of the excision. Two patients had extended excisions of the misdirected eyelashes 3 years after the initial surgery, and they did not have any further recurrences. Three other patients were followed without additional treatment because lacrimation and eye discharge were mild even with some eyelashes misdirected toward cornea.

CONCLUSIONS

Eyelash line resection is a simple and effective technique for cilial entropion and medial epiblepharon in patients with Down's syndrome. The surgery improves the SPK and frequency of spectacle wear.

TRIAL REGISTRATION NUMBER

NCT01758718.

Visual acuity deficits in children with nystagmus and Down syndrome

PURPOSE

To investigate the association between visual acuity deficits and fixation instability in children with Down syndrome and nystagmus.

DESIGN

Prospective cross-sectional study.

METHODS

setting: Institutional. study population:Sixteen children (aged 10 months-14 years) with Down syndrome and nystagmus, and a control group of 93 age-similar children with unassociated infantile nystagmus. observation procedures: Binocular Teller acuity card testing and eye-movement recordings. Fixation stability was quantified using the nystagmus optimal fixation function (NOFF). An exponential model based on results from the control group with unassociated infantile nystagmus was used to relate fixation stability to age-corrected visual acuity deficits. main outcome measures: Binocular grating visual acuity and NOFF.

RESULTS

Visual acuity was 0.2-0.9 logMAR (20/30-20/174 Snellen equivalent) and corresponded to a 0.4 logMAR (4 lines) mean age-corrected visual acuity deficit. Fixation stability ranged from poor to mildly affected. Although visual acuity deficit was on average 0.17 logMAR larger (P = .005) than predicted by the model, most children had visual acuity deficit within the 95% predictive interval.

CONCLUSIONS

There was a small mean difference between the measured visual acuity deficit and the prediction of the nystagmus model. Although other factors also contribute to visual acuity loss in Down syndrome, nystagmus alone could account for most of the visual acuity deficit in these children.

The orthoptics of Down syndrome

Patients with Down syndrome have many ocular anomalies. Most of them are treatable conditions that can strongly affect their quality of life if not addressed at an early age. It is important for clinicians to be aware of improvements in both the medical field and the educational systems in the assessment of these patients and in their treatment.

Ocular abnormalities and systemic disease in Down syndrome

INTRODUCTION

Ocular problems as refractive errors, strabismus, accommodation, and cataract are well known in children with Down syndrome (DS). However, there is little information on the possible correlation of eye problems with systemic diseases such as heart defect (with or without surgery), hypotony, hypothyroidism, hearing loss, and others.

METHODS

Ophthalmic problems versus certain systemic diseases were studied in 65 children with DS, aged 2 months to 13 years, referred to the University Eye Hospital Ljubljana, Slovenia from 2008 to 2010. Standard ophthalmic examination methods were used, and physical data were taken from pediatric records.

RESULTS

Ocular findings included nystagmus (29.2%), esotropia (26.1%), epiphora (21.5%), Brushfield spots (16.9%), lens opacities (12.3%), abnormalities of the retinal vessels, foveal hypoplasia, or retinal pigment epithelium hyperplasia (32.2%), and optic disc pallor (7.6%). Hyperopia (36.9%) was the most frequent refractive error in the group, followed by astigmatism (29.2%) and myopia (24.6%). No diagnosed systemic abnormalities were found in 18.3% of the children, while 30.7% had congenital heart defect. Hypothyroidism, hypotony, hearing loss, gastrointestinal tract malformations, and leukemia were less common. Nystagmus was related to myopia and esotropia, and to heart disease and heart operations.

CONCLUSIONS

Comorbidities are common in DS and complicate diagnosis, development, and therapy.

Refractive errors and strabismus in Down's syndrome in Korea

Purpose

The aims of this study were to examine the distribution of refractive errors and clinical characteristics of strabismus in Korean patients with Down's syndrome.

Methods

A total of 41 Korean patients with Down's syndrome were screened for strabismus and refractive errors in 2009.

Results

A total of 41 patients with an average age of 11.9 years (range, 2 to 36 years) were screened. Eighteen patients (43.9%) had strabismus. Ten (23.4%) of 18 patients exhibited esotropia and the others had intermittent exotropia. The most frequently detected type of esotropia was acquired non-accommodative esotropia, and that of exotropia was the basic type. Fifteen patients (36.6%) had hypermetropia and 20 (48.8%) had myopia. The patients with esotropia had refractive errors of +4.89 diopters (D, ±3.73) and the patients with exotropia had refractive errors of -0.31 D (±1.78). Six of ten patients with esotropia had an accommodation weakness. Twenty one patients (63.4%) had astigmatism. Eleven (28.6%) of 21 patients had anisometropia and six (14.6%) of those had clinically significant anisometropia.

Conclusions

In Korean patients with Down's syndrome, esotropia was more common than exotropia and hypermetropia more common than myopia. Especially, Down's syndrome patients with esotropia generally exhibit clinically significant hyperopic errors (>+3.00 D) and evidence of under-accommodation. Thus, hypermetropia and accommodation weakness could be possible factors in esotropia when it occurs in Down's syndrome patients. Based on the results of this study, eye examinations of Down's syndrome patients should routinely include a measure of accommodation at near distances, and bifocals should be considered for those with evidence of under-accommodation.

Horizontal strabismus worldwide--what are the risk factors?

Horizontal strabismus has constant risk factors of ethnicity, family history, genetic conditions and potentially modifiable risk factors of maternal smoking, prematurity, low birth weight, refractive errors and neurodisability.

Outcomes of strabismus surgery for esotropia in children with Down syndrome compared with matched controls

PURPOSE

Strabismus surgery dosages used in children with various neurodevelopmental disorders have been the subject of controversy. Few data have been reported regarding surgical results in individuals with Down syndrome (DS).

METHODS

A retrospective, case-control study was performed in which children with DS and previous bilateral medial rectus recession surgery were matched with similar control patients without DS. Surgical results were compared using a random coefficients model for repeated measurements for each group.

RESULTS

Sixteen patients with DS were matched with 16 control patients. Mean preoperative esotropia was 28.4 prism diopters (PD) in the DS group and 27.9 PD in the control group. No significant difference was found in surgical dosages between the two groups (P = .2402). Median surgical dosage was 4.4 mm in the DS group and 4.5 mm in the control group. Preoperative and 4-month and 24-month postoperative mean angles of esotropia were not different between groups (P = .8050). The 4-month postoperative mean angles of esotropia for the DS and control groups were 3.15 and 2.66 PD, respectively. The 24-month mean angles of esotropia for the DS and control groups were 7.09 and 6.60 PD, respectively.

CONCLUSION

Standard bilateral medial rectus recession surgical dosages need not be modified for individuals with DS.

Ophthalmic disorders in adults with down syndrome

A myriad of ophthalmic disorders is associated with the phenotype of Down syndrome including strabismus, cataracts, and refractive errors potentially resulting in significant visual impairment. Ophthalmic sequelae have been extensively studied in children and adolescents with Down syndrome but less often in older adults. In-depth review of medical records of older adults with Down syndrome indicated that ophthalmic disorders were common. Cataracts were the most frequent ophthalmic disorder reported, followed by refractive errors, strabismus, and presbyopia. Severity of intellectual disability was unrelated to the presence of ophthalmic disorders. Also, ophthalmic disorders were associated with lower vision-dependent functional and cognitive abilities, although not to the extent that was expected. The high prevalence of ophthalmic disorders highlights the need for periodic evaluations and individualized treatment plans for adults with Down syndrome, in general, but especially when concerns are identified.

Bifocals in Down syndrome study (BiDS): analysis of video recorded sessions of literacy and visual perceptual skills

PURPOSE

In this longitudinal study, a group of school children with Down syndrome (DS) and reduced accommodation were prescribed bifocals and followed to investigate the impact of bifocal spectacles on early literacy and visual perceptual skills. The natural progression of early literacy skills in this population along with the changes with bifocals, described by monthly subtest scores and the time taken to complete literacy and visual perceptual tasks, are reported.

METHODS

Fourteen children with DS, aged eight to 18 years, were followed for five months with single vision lenses; 11 were prescribed bifocals based on their accommodative ability and followed for another five months. A battery of reading and visual perceptual tests was administered before and after prescription of bifocals. Monthly subtests of similar tasks were administered to measure progress. All the visits were videotaped to determine the time taken for the child to complete each task.

RESULTS

There was no significant measurable natural progression of early literacy skills in this group of participants on the Word Identification (WI) subtest (Repeated Measures ANOVA, F [4, 24]=1.377, p = 0.271) and Dolch sight words (RMANOVA F [4, 24]= 0.344, p = 0.846). In contrast, once bifocals were prescribed there was significant improvement in the scores of the monthly subtests (p = 0.050, 0.025 and 0.023 for WI, Dolch sight words and numbers, respectively) and the rate of progress in monthly scores improved for WI (p = 0.008). Repeated measures Analysis of Variance showed a significant decrease in the completion times with bifocals for the WI test in the full battery of tests (p = 0.0015). There was significant correlation between the improvement in focus with bifocals and the decrease in completion time for the WI task (p = 0.004).

CONCLUSIONS

This study demonstrates no significant natural progression over a five-month period in the group of participants with Down syndrome; however, with bifocals, faster and improved performance on some literacy skills was observed. We recommend that bifocals be considered in children with Down syndrome presenting with inadequate accommodation to optimise their educational potential.

Ophthalmic manifestations of mosaic Down syndrome

PURPOSE

The cognitive and physical stigmata of mosaic Down syndrome (DS) are often considered to be less severe than complete trisomy-21 DS. In contrast to complete trisomy-21 DS, the ophthalmic manifestations in mosaic DS have rarely been reported. The aim of the present study is to report clinically significant ophthalmic abnormalities in a cohort of individuals with mosaic DS.

METHODS

A prospective cross-sectional observational case series was designed to evaluate ophthalmic manifestations of mosaic DS. Individuals with mosaic DS were recruited and examined at the biennial meeting of the International Mosaic Down Syndrome Association. A medical, surgical, and ocular history was obtained. Each subject received a complete eye examination on site, including assessment of visual acuity, alignment, motility, sensory function, accommodation, anterior segment, fundus, and cycloplegic refraction.

RESULTS

Seventeen individuals with mosaic DS (mean age, 9 years; range, 6 months to 32 years) underwent eye examinations. Clinically significant refractive errors were present in 41% of the subjects, accommodative insufficiency in 59%, strabismus in 35%, nystagmus in 6%, and cataract in 6%. Ten individuals completed optotype visual acuity testing. Mean LogMAR acuity of the better eye of each subject was 0.2 (20/32 equivalent).

CONCLUSIONS

Clinically significant ophthalmic disorders are common among children and young adults with mosaic DS. Our findings support regular periodic eye examinations for these individuals.

Strabismus, refractive errors and nystagmus in children and young adults with Down syndrome

PURPOSE

The aims of the present population-based, cross-sectional study were to examine the frequency and type of strabismus, refractive errors and nystagmus in children and young adults with Down syndrome (DS) in Macedonia and Croatia.

METHODS

A total of 170 unselected children and young adults with DS aged 1-34 years were examined for ocular findings. The ocular examination included: a visual acuity assessment, cycloplegic refraction, ocular alignment and ocular motility.

RESULTS

Strabismus was found in 45 of 170 children (26.5%), and esodeviation was the most common type. Nine (20%) had exodeviation and 4 (8.9%) vertical deviation. In 27 of 32 esotropic patients, the strabismus was regarded as acquired esodeviations. The frequency of strabismus was lowest in the high-grade hyperopia group (5%). Concerning esodeviations, fewer cases (3%) were in the high-grade hyperopia group. Most of the cases with esodeviations were in correlation with low-grade hyperopia (31%), myopia (28 %) and emetropia (16%). Hyperopia was the most common refractive error and high myopia increased in prevalence in the over 20 age group. Astigmatism was present in 72.4% of patients. Nystagmus was observed in 18 patients. Ten of 18 patients with nystagmus were associated with the presence of strabismus (9 esodeviations, 1 exotropia).

CONCLUSION

In our study, the high prevalence of strabismus can not be attributed to the presence of hyperopia. Our data show no association between refraction and strabismus in children with DS. Oblique astigmatism has been found to be the most common type of astigmatism in our study group.

The Down syndrome critical region regulates retinogeniculate refinement

Down syndrome (DS) is a developmental disorder caused by a third chromosome 21 in humans (Trisomy 21), leading to neurological deficits and cognitive impairment. Studies in mouse models of DS suggest that cognitive deficits in the adult are associated with deficits in synaptic learning and memory mechanisms, but it is unclear whether alterations in the early wiring and refinement of neuronal circuits contribute to these deficits. Here, we show that early developmental refinement of visual circuits is perturbed in mouse models of Down syndrome. Specifically, we find excessive eye-specific segregation of retinal axons in the dorsal lateral geniculate nucleus. Indeed, the degree of refinement scales with defects in the "Down syndrome critical region" (DSCR) in a dose-dependent manner. We further identify Dscam (Down syndrome cell adhesion molecule), a gene within the DSCR, as a regulator of eye-specific segregation of retinogeniculate projections. Although Dscam is not the sole gene in the DSCR contributing to enhanced refinement in trisomy, Dscam dosage clearly regulates cell spacing and dendritic fasciculation in a specific class of retinal ganglion cells. Thus, altered developmental refinement of visual circuits that occurs before sensory experience is likely to contribute to visual impairment in individuals with Down syndrome.

Static and dynamic measurements of accommodation in individuals with down syndrome

PURPOSE

To identify whether static and dynamic aspects of accommodation other than accuracy are deficient in individuals with Down syndrome (DS) and whether poor accommodation is related to sensory or motor pathway deficits.

METHODS

Static aspects of accommodation (maximum accommodative response and lag) were measured with an autorefractor for both proximal and minus lens demands. Dynamic aspects of accommodation (latency, peak velocity, microfluctuations) were recorded at 30 Hz with a custom-built photorefractor as subjects viewed a movie switching between 11 m and 50, 33, 25, or 20 cm. Thirty-six subjects with DS were recruited (age 3 to 39 years), and 24 (67%) had useable responses for at least one study measurement for comparison with 140 controls (3 to 40 years) from a previously published cohort.

RESULTS

DS subjects had lower maximum accommodative responses (mean = 2.52 ± 1.66 D) and higher lags (1.81 ± 1.30 D for 33 cm demand) than controls for both proximal and minus lens stimuli. DS subjects had greater microfluctuations (one-way ANCOVA, P < 0.001), and a small percentage of the total number of latency measurements (17% accommodative and 16% disaccommodative) were longer than controls. Peak velocities of accommodation and disaccommodation were not different between groups (one-way ANCOVA, P = 0.143).

CONCLUSIONS

Peak velocities of accommodation and disaccommodation (primarily motor aspects) did not differ between controls and DS subjects; however, latencies (primarily sensory) and microfluctuations (combined motor and sensory) were poorer in DS subjects. These results suggest that poor accommodative accuracy in individuals with DS may be predominantly related to sensory deficits.

Screening for refractive errors in children: the plusoptiX S08 and the Retinomax K-plus2 performed by a lay screener compared to cycloplegic retinoscopy

PURPOSE

To evaluate the performance of the autorefractor Retinomax K-plus2 and the photoscreener plusoptiX S08 in measuring refractive errors by comparing them with cycloplegic retinoscopy (CR) and to assess limitations associated with their use.

METHODS

Cross-sectional study to compare data from CR, performed by an orthoptist, to data from Retinomax K-plus2 and plusoptiX S08 performed by a lay screener. Sensitivity and specificity for the detection of significant refractive errors were determined according to American Academy of Pediatric Ophthalmology and Strabismus criteria.

RESULTS

Two hundred children were included, with a mean age of 5.2 ± 2.6 years (3 months to 11 years). Compared to CR, the plusoptiX S08 showed a mean difference of -1.13 ± 1.25 D (95% limits of agreement [LOA], -3.59 to +1.32) for spherical equivalent (SE) and -0.23 ± 0.53 D (LOA, -1.28 to +0.81) for the cylinder. Mean difference for the Retinomax K-plus2 before cycloplegia was -0.08 ± 0.58 D (LOA, -1.23 to +1.06) for SE and 0.03 ± 0.38 D (LOA, -0.72 to +0.78) for the cylinder; after cycloplegia -2.11 ± 1.64 D (LOA, -5.33 to +1.10) for SE and -0.06 ± 0.47 D (LOA, -0.98 to +0.86) for the cylinder. Sensitivity for detecting hyperopia >3.5 D with the plusoptiX S08 was 33.3%, the Retinomax before cycloplegia 31.0% and after cycloplegia 84.6% and high for detecting myopia, astigmatism, and anisometropia.

CONCLUSIONS

Retinomax K-plus2 and plusoptiX S08 have high sensitivity for the detection of myopia, astigmatism, and anisometropia compared to cycloplegic retinoscopy; however, when used without cycloplegia, hyperopia is underestimated.

Bifocals in children with Down syndrome (BiDS) - visual acuity, accommodation and early literacy skills

PURPOSE

Reduced accommodation is seen in children and young adults with Down syndrome (DS), yet providing bifocals has not become a routine clinical management. This study investigates the impact of bifocals on visual function, visual perceptual and early literacy skills in a group of school children with DS.

METHODS

  In this longitudinal study, each child was followed for 5months with single-vision (SV) lenses after which bifocals were prescribed if required, based on their accommodative response. Visual acuity (VA), accommodation, perceptual and literacy skills were measured after adaptation to bifocals and 5months later. Educational progress and compliance with spectacle wear were assessed through school and parental reports.

RESULTS

  Fourteen children and young adults with DS participated in the study. Eighty-five percent required bifocals with additions ranging from +1.00D to +3.50D. The mean near logMAR VA improved with bifocals (p=0.007) compared to SV lenses. Repeated measures anova showed that there was more accurate focus (less accommodative lag) through the bifocals (p=0.002), but no change in the accommodation exerted through the distance portion compared to SV lenses (p=0.423). There was a main effect of time on sight words (p=0.013), Word Identification (p=0.047), Visual Closure (p=0.006) and Visual Form Constancy (p=0.001).

CONCLUSION

Bifocals provide clearer near vision in DS children with reduced accommodation. This is shown by improved VA and decreased lag of accommodation. The results indicate that the improvement in VA results in improved scores in early literacy skills. Better compliance with bifocals over SV lenses was seen.

Corneal power and astigmatism in Down syndrome

PURPOSE

Corneal and crystalline lens shape differ in Down syndrome (DS) compared with developmentally normal populations. This study specifically explored the association between corneal curvature and refractive error for the first time in DS.

METHODS

Participants were 29 children with 59 age-matched controls (33 males and 35 females; mean age 12.4 +/- 1.8 years) and DS (9 to 16 years; 19 males and 10 females; mean age 12.8 +/- 1.9 years). Corneal curvature was measured using a hand-held keratometer. Refractive error was assessed by distance static retinoscopy in the control group and Mohindra retinoscopy in the DS group.

RESULTS

The DS group demonstrated a high frequency and magnitude of refractive errors (mean DS + 2.52 +/- 3.00 D; mean controls -0.46 +/- 1.32 D). The majority of controls had little or no significant refractive error. DS cornea were significantly steeper (mean DS 45.62 +/- 2.13 D; mean controls 43.10 +/- 1.37 D). Neither DS nor control data demonstrate significant relations between corneal and total refractive power (M vector). Astigmatic errors in the DS group were more frequently oblique and demonstrated strong right-left specificity. The DS data did not demonstrate a significant association between corneal and total astigmatism along principal meridians (J0), however, a significant relation was found for the control data (linear regression, r = 0.51, p < 0.0001). No significant association between corneal and total oblique astigmatism (J45) was demonstrated by either DS or control data.

CONCLUSIONS

The study is the first to explicitly investigate the association between corneal power and refractive error in children with DS. The majority of the DS group have significant refractive errors including an increased prevalence of oblique astigmatism. Corneal curvature in DS is not related to spherical (M) or astigmatic (J0, J45) refractive error. Further research is required to better understand the association between the ocular structures of the DS eye and their impact on functional vision.

Bifocals and Down's syndrome: correction or treatment?

PURPOSE

Accommodation is reduced in approximately 75% of children with Down's syndrome (DS). Bifocals have been shown to be beneficial and they are currently prescribed regularly. Clinical observations suggest the likelihood of improving accommodative ability after bifocal wear. The aim of the study is to evaluate the potential use of bifocals as a treatment for the reduced accommodation.

METHODS

Clinical records of 40 children from the Cardiff Down's Syndrome Vision Research Unit, who were prescribed bifocals, were reviewed. Accommodation was noted before wearing the bifocals and during either their latest visit or when the children stopped using bifocals. Accommodation was reassessed during a follow up visit for the children who stopped wearing bifocals. Development of accommodation before bifocal commencement, age at bifocal prescription, gender, type of refractive error, visual acuity and the presence of strabismus were examined to evaluate their contribution to accommodation improvement.

RESULTS

The accommodative ability of 65% (n = 26) of the children improved (through the distance part of the lens) after using the bifocals. More than half of those developed accurate accommodation without the use of bifocals (n = 14). Accommodative responses did not show any improvement with age before the children began wearing bifocals. Accurate accommodation was sustained after returning to single vision lenses in all examined children. The age distribution of the children on bifocal commencement was diverse. Presence of strabismus, refractive error type, visual acuity and gender did not have any effect on gaining improvement.

CONCLUSIONS

Bifocals are an effective correction for the reduced accommodation in children with DS and also act to improve accommodation with a success rate of 65%. Bifocal wear can therefore be temporary, i.e. a 'treatment' for the deficit, in at least one third of children.