Amblyopia and visual acuity in children with Down's syndrome

Ophthalmic manifestations in children with Down Syndrome in Bogotá, Colombia

BACKGROUND

To describe the ocular features of a cohort of children with Down Syndrome (DS) in Bogotá, Colombia.

METHODS

We performed a cross-sectional study, evaluating 67 children with DS. A pediatric ophthalmologist performed a complete optometric and ophthalmological evaluation of each child, including visual acuity, ocular alignment, external eye examination, biomicroscopy, auto-refractometry, retinoscope in cycloplegia, and fundus examination. Results were reported as frequency distribution tables with percentages for categorical variables and means and standard deviation or median and interquartile ranges for continuous variables, according to their distribution. We used the Chi-square test or Fisher's exact test for categorical variables and ANOVA or Kruskal-Wallis for continuous variables when indicated.

RESULTS

A total of 134 eyes from 67 children were evaluated. Males represented 50.7%. The children's age ranged from 8-16 years, with a mean of 12.3 (SD 2.30). The most frequent refractive diagnosis per eye was hyperopia (47%), followed by myopia (32.1%) and mixed astigmatism (18.7%). The most frequent ocular manifestations were oblique fissure (89.6%), followed by amblyopia (54.5%) and lens opacity (39.4%). Female sex was associated with strabismus (P = 0.009) and amblyopia (P = 0.048).

CONCLUSION

Our cohort had a high prevalence of disregarded ophthalmological manifestations. Some of these manifestations, such as amblyopia, can be irreversible and severely affect the neurodevelopment of DS children. Therefore, ophthalmologists and optometrists should be aware of the visual and ocular affection of children with DS to assess and provide appropriate management. This awareness could improve rehabilitation outcomes for these children.

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.

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.

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.

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.

Prevalence of Ocular Pathology on Initial Screening and Incidence of New Findings on Follow-up Examinations in Children With Trisomy 21

PURPOSE

Various ophthalmologic findings have been associated with trisomy 21. However, prior studies on this topic are limited by their sample size and the lack of follow-up regarding the incidence of new pathology after an initially normal examination. We determined whether children who have a normal first examination need to have formal reevaluation by an ophthalmologist.

DESIGN

Retrospective cohort study.

METHODS

Records were reviewed for 689 patients with trisomy 21 evaluated at Vanderbilt Eye Institute between 2012 and 2017. Ocular and refractive abnormalities present on initial screening were recorded and follow-up data were reviewed to determine if new abnormalities developed at subsequent visits.

RESULTS

Of the 689 patients, 410 (59.5%) had a significant finding on their first examination. The most common abnormalities seen on initial screening examination were strabismus, significant refractive error, and eyelid abnormalities (including ectropion and accessory puncta). Of the 279 initially normal patients, 179 had at least 1 follow-up visit at a mean follow-up interval of 21.6 months (average age 3.7 years). At the first follow-up visit, 129 remained normal, while 50 had a new abnormality, most commonly significant refractive error and strabismus. On second follow-up visit, at a mean follow-up interval of 12 months (average age 4.8 years), 63% remained normal.

CONCLUSIONS

Ocular pathology occurs in trisomy 21 at a much higher prevalence than the general population; thus these children initially should have a comprehensive eye examination. Although the development of new ocular pathology in a child with trisomy 21 and a previously normal examination is not unusual, most of these new abnormalities are detectable with automated vision screening techniques or direct visual inspection of the eyes and ocular adnexa; thus once a child has a normal examination, a formal vision screening could replace a formal ophthalmologic examination.

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.

Visual characteristics of children with Down syndrome

PURPOSE

To analyze long-term visual development in children with Down syndrome who received early ophthalmological intervention.

METHODS

A total of 125 children with Down syndrome who were examined before 6 years of age and followed up for more than 5 years were selected. Visual development, refraction, visual acuity testing, and the prescription of spectacles were examined retrospectively.

RESULTS

Mean visual acuity by age was as follows: 2 years, 1.13 ± 0.23 logarithm of the minimum angle of resolution (logMAR); 5 years, 0.55 ± 0.25 logMAR; 8 years, 0.27 ± 0.19 logMAR; 11 years, 0.17 ± 0.16 logMAR; and 14 years, 0.10 ± 0.15 logMAR. In 32 children (25.6%), visual acuity reached 0.0 logMAR or better. Hyperopia of +2D or more was observed in 132 eyes (52.8%), and astigmatism of 2D or more was observed in 153 eyes (61.2%). Subjective testing was difficult in many children prior to 4.5 years of age, and grating acuity testing was necessary. Spectacles were prescribed at a mean age of 3.5 ± 1.6 years in 120 children (96.0%). The average duration until the spectacles were worn constantly was 9.0 ± 9.3 months.

CONCLUSION

Early ophthalmological intervention and longitudinal care is important for children with Down syndrome.

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.

Ophthalmic manifestations in children and young adults with Down syndrome and congenital heart defects

PURPOSE

To investigate whether different types of ocular manifestations are associated with congenital heart disease (CHD) in a large Caucasian population of children and young adults with Down syndrome (DS).

METHODS

Population-based, case-control study which included 185 subjects with DS (mean age 13.2 ± 7.9 years), who reported presence or absence of CHD; DS with CHD group (51 subjects, mean age 10.6 ± 5.6 years) and DS without CHD (134 subjects, mean age 14.2 ± 8.4 years).

RESULTS

In our sample with DS and CHD, strabismus was found in 15 subjects (29.4%), nystagmus in 1 (2.0%), epiblepharon in 21 (41.2%) and Brushfield spots in 15 (31.3%). In the DS without CHD group, strabismus was found in 38 participants (28.4%), nystagmus in 13 (9.7%), epiblepharon in 31 (23.5%) and Brushfield spots in 21 (16.0%). Only the variables epiblepharon and presence of Brushfield spots differed significantly between the two groups (p = 0.02 and p = 0.03, respectively). Hyperopia was present in 26 participants (53.1%) in the DS with CHD group, and in 65 (57.0%) in the DS without CHD group. Oblique astigmatism was present in 25 (52.1%) in the DS with CHD group and in 61 (53.5%) in the DS without CHD group.

CONCLUSIONS

Frequencies of DS participants presenting with strabismus, nystagmus, hyperopia and oblique astigmatism were not statistically different between those with CHD and those without CHD in this sample. Further studies are needed to confirm if there are associations between the presence of Brushfield spots or epiblepharon and CHD in patients with DS.

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.

Infantile nystagmus and visual deprivation: foveal instability and refractive development in a low vision register series

PURPOSE

To evaluate whether effects of early foveal motor instability due to infantile nystagmus might compare to those of experimental visual deprivation on refraction in a childhood series.

METHODS

This was a retrospective analysis of data from the Danish Register for Blind and Weaksighted Children with infantile nystagmus recorded as prime diagnosis. We perused 90 records of children now aged 10-17 years, some of whom eventually exceeded the register borderline of 0.3 as best-corrected visual acuity. Spherical equivalent refraction was the primary outcome parameter, but visual acuity, astigmatism, and age were further considered. The series comprised 48 children with nystagmus as single diagnosis, whereas 42 had clinical colabels (Down syndrome [13], dysmaturity [9], and mental retardation, encephalopathy [20]).

RESULTS

Median binocular visual acuity was 0.3 in the full series, and median refraction was emmetropia in all subgroups. Compared with Danish control data, myopia was over-represented, and generally of juvenile onset. The Down syndrome subgroup was separated from the remainder by an even higher myopia prevalence. Astigmatism above 1 D cylinder value was recorded in 52% of all cases.

CONCLUSIONS

The prevalence of myopia and astigmatism was higher among children with nystagmus than in controls. Myopia was mainly juvenile, and not related to the period of infancy when the motor foveal smear is considered most disturbing and possibly influencing visual development.

Esotropia surgery in children with Down syndrome

PURPOSE

To evaluate postoperative alignment in children with and without Down syndrome after surgical correction of esotropia.

METHODS

The medical records of consecutive patients with Down syndrome who underwent corrective surgery for esotropia between August 1992 and July 2012 were retrospectively reviewed. Age range for eligibility was between 8 months and 17 years at surgery. The control group comprised randomly selected, age-matched patients without Down syndrome who underwent the same surgical procedure. Postoperative alignment within 10(Δ) of orthotropia at 6 months' follow-up and at the final postoperative visit was considered a successful outcome.

RESULTS

A total of 17 children with Down syndrome and 27 control subjects were included. The control group and Down syndrome group did not differ significantly in either postoperative follow-up (5.2 ± 3.2 versus 5.6 ± 5.2 years, respectively) or magnitude of deviation before surgery (40 ± 18.2(Δ) versus 39 ± 12.8(Δ), respectively). Surgical success was achieved in 76% of patients with Down syndrome and in 85% of control patients at 6 months' follow-up.

CONCLUSIONS

In this patient cohort, good surgical outcomes were achieved in children with esotropia and Down syndrome compared with those with esotropia but without Down syndrome using the same surgical technique.

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.

Environmental enrichment decreases GABAergic inhibition and improves cognitive abilities, synaptic plasticity, and visual functions in a mouse model of Down syndrome

Down syndrome (DS) is the most common genetic disorder associated with mental retardation. It has been repeatedly shown that Ts65Dn mice, the prime animal model for DS, have severe cognitive and neural plasticity defects due to excessive inhibition. We report that increasing sensory-motor stimulation in adulthood through environmental enrichment (EE) reduces brain inhibition levels and promotes recovery of spatial memory abilities, hippocampal synaptic plasticity, and visual functions in adult Ts65Dn mice.

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.

An assessment of optokinetic nystagmus (OKN) in persons with Down syndrome

Down syndrome (DS), the most common genetically defined cause of intellectual disability, is the phenotypic consequence of a supernumerary chromosome 21. Persons with DS commonly display deficits in visuomotor integration, motor coordination, and balance. Despite the key roles of the optokinetic and vestibular systems in these submodalities of motor function, a systematic investigation of the optokinetic nystagmus (OKN) and vestibulo-ocular reflex (VOR) in persons with DS had lacked in the literature. Accordingly, this study generated quantitative data on oculomotor function in persons with DS under optokinetic and sinusoidal smooth pursuit stimulation. Thirty-two participants with DS (14-36 years old, equally divided by gender) and 32 chronological age- and gender-matched typically developing controls were recruited from the community. Eye movements were recorded by binocular video oculography and an LCD projector produced visual stimulation. Assessments of the gain and frequency of slow phase of OKN beats and number and mean amplitude of intruding saccades during smooth pursuit were performed. Individuals with DS displayed angular velocity-dependent reduction in OKN gain and number of produced nystagmus beats compared to controls. The gain of the smooth pursuit was not significantly different between participants with DS and control participants. However, the number and mean amplitude of intruding saccades during smooth pursuit were increased in participants with DS compared to control participants. These findings may have implications to the understanding of the neurological basis of the motor dysfunction that affects performance in many practical tasks persons with DS encounter in their everyday lives.

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.

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.

Ophthalmic abnormalities in children with Down syndrome

A comprehensive review of the available literature was performed to determine the common ophthalmic disorders in children aged 0 to 16 years with Down syndrome. The UK National Library for Health interface was used to search seven electronic databases, including MEDLINE and EMBASE. Terms related to Down syndrome, ophthalmology, and pediatrics were combined in the search strategy, which yielded 230 articles. Application of exclusion criteria left 23 articles to include in the review. Literature synthesis demonstrated that children with Down syndrome are at risk for several ocular disorders. Refractive error was a common finding, particularly hyperopia. Strabismus was also reported regularly, particularly esodeviation. Other frequent findings included poor visual acuity, nystagmus, and blepharitis, whereas cataract and glaucoma were less common but had potentially serious implications for future vision. Only one study compared routine pediatric examination to that of a pediatric ophthalmologist. The findings of this review confirm the need for an ophthalmic screening program for children with Down syndrome. Additional work should investigate how such a program could be best implemented and ascertain how to involve different professionals in such a service.

Surveillance of vision and ocular disorders in children with Down syndrome

Children with Down syndrome have a high prevalence of ocular disorders. The UK Down's Syndrome Medical Interest Group (DSMIG) guidelines for ophthalmic screening were locally implemented into a protocol that included neonatal eye examination by an ophthalmologist and a comprehensive ophthalmological examination (cycloplegic refraction, ophthalmoscopy, and orthoptic assessment) by at least the age of 3 years, followed by preschool follow-up as indicated. We audited retrospectively surveillance for ocular disorders before and after the DSMIG-based guidelines were locally adopted in 1995. Results were compared for children born before and after the implementation of screening guidelines. A total of 81 children (43 females, 38 males) with Down syndrome were identified. After the DSMIG protocol, 34/36 children received a full ophthalmological examination in the neonatal period, compared with 9/27 children before 1995 (p<0.001). Neonatal screening resulted in the detection of cataracts in three infants. Mean age of first comprehensive ophthalmic screening outside the neonatal period was similar in the two groups (1y 6mo before guidelines vs 1y 9mo after), as were the proportion of children receiving preschool eye checks (27/30 before; 17/18 after). Overall, 65.7% children were screened in accordance with the guidelines, improving to 100% in recent years. At school age, 43% of the study population had significant refractive errors, with 27% having hypermetropia and astigmatism. Earlier prescription of glasses for refractive errors was seen (mean age 5y 6mo before guidelines; 3y 6mo after; p<0.001). Prevalence of other ocular disorders included strabismus (34/72, 47%), nasolacrimal duct obstruction (26/73, 35.6%), cataracts (5/64, 7.8%), and nystagmus (12/72, 16%). Establishment of the DSMIG-based local protocol has streamlined ocular surveillance. It is anticipated that this will improve developmental and functional outcomes in Down syndrome.

Use of health care guidelines in patients with Down syndrome by family physicians across Canada

OBJECTIVE

To describe the occurrence of common medical and psychological conditions in individuals with Down syndrome during their life span, and to measure the use of the Down Syndrome Medical Interest Group's health care guidelines by family physicians across Canada, as reported by parents or caregivers.

METHODS

The Down Syndrome Research Foundation sent a questionnaire to 314 families across Canada who were part of the Canadian Voluntary Registry on Down Syndrome. This questionnaire was designed to collect information from parents about physical examinations, laboratory tests, referrals and discussions with family physicians that are listed in the health care guidelines.

RESULTS

Two hundred twenty-three families responded to the survey. The highest response rates were in families with children in the five- to 12-year-old age range (41.7%) and the 13- to 18-year-old age range (19.7%). The most common medical conditions reported were visual, hearing and cardiac related. A high percentage of sleep-, gastrointestinal- and thyroid-related conditions were also reported. In the adult group (ie, 30 years of age and older), there was a high proportion of depression and/or anxiety disorders reported. The percentage of those reporting physical examinations and medical referrals by family physicians were highest in the five- to 12-year-old age range and dropped below 50% in those aged 19 years and older. In the one- to four-year-old and five- to 12-year-old age groups, the percentages of those with Down syndrome referred for hearing tests and celiac screens were reported to be below 30%. The percentages of those reporting discussions on behavioural issues were below 50% in all age groups.

CONCLUSIONS

Physical examinations, as per the recommended guidelines, were followed only in the five- to 12-year-old age group. Many of the recommendations regarding discussion of behavioural problems, transition planning, diet, exercise and issues around puberty or sexual health were followed infrequently in all age groups. Further physician education about the guidelines is necessary.

Visual dysfunctions and ocular disorders in children with developmental delay. I. prevalence, diagnoses and aetiology of visual impairment

PURPOSE

To describe the prevalence, diagnoses and aetiologies of visual impairment in children with developmental delay (DD) in a Danish county with a population of 618 000 citizens.

METHODS

We carried out a cross-sectional study in Copenhagen County of children aged 4-15 years with profound to borderline DD (IQ <or= 80). Children were located through school psychologists or paediatric clinics. The number of children with DD was estimated using the capture-recapture method.

RESULTS

A total of 1126 children fulfilled the inclusion criteria, corresponding to 97.7% of the estimated number of children with DD in the county. Ophthalmological examinations were performed in 923 children. The prevalence of visual impairment was 10.5% in the study group and 22.4% in those with an IQ <or= 50. The diagnoses were predominantly cerebral visual impairment, optic atrophy, retinal dystrophies and congenital nystagmus. The aetiology of visual impairment was prenatal in 54 children, perinatal in 29 children and postnatal in seven children.

CONCLUSIONS

Visual impairment is highly increased in children with DD and is correlated to low IQ.

Strabismus in Down syndrome

PURPOSE

To determine the distribution of refractive errors and clinical characteristics of strabismus in patients with Down syndrome.

PATIENTS AND METHODS

Patients with Down syndrome attending the Izmir Association for Supporting Patients With Down Syndrome in Izmir, Turkey, were screened for strabismus and refractive errors. All patients underwent a complete eye examination including cycloplegic refraction and dilated fundus examination. Ocular alignment was evaluated using the cover test and either the Krimsky or the Hirschberg corneal reflex test depending on the cooperation of the patient. Strabismic and nonstrabismic patients were compared for refractive errors, anisometropia, and amblyopia.

RESULTS

Fifty-seven patients with an average (+/- standard deviation) age of 9.30 years (+/- 6.14 years; range, 1 to 31 years) were screened. Twenty-five (44%) were female and 32 (56%) were male. Eleven patients (19%) had strabismus. Ten (18%) had esotropia and 1 (2%) had exotropia. Infantile esotropia was observed in 3 patients who had no significant refractive errors. Seven patients had acquired esotropia; they had clinically significant refractive errors and anisometropia. A higher frequency of hypermetropia was noted in patients with strabismus (P < .05).

CONCLUSIONS

Esotropia and hypermetropia are common in patients with Down syndrome. Early diagnosis and treatment of strabismus and associated ocular conditions such as refractive errors and amblyopia may improve the quality of life for these patients.

Prevalence and outcomes of childhood visual disorders

PURPOSE

This population-based study examines the prevalence of childhood visual disorders: amblyopia (strabismus, refractive errors) and organic disease. It also assesses treatment outcomes, visual impairment and residual amblyopia.

METHODS

1582 children were retrospectively analysed on treatment completion (age 8-9 years). Significant visual disorders included: esotropia, exotropia, anisometropia (hyperopia > or = 1.50DS, astigmatism > or = 1.00DC, myopia > or = 1.50DS), ametropia (hyperopia > or = 1.50DS, astigmatism > or = 1.0DC, myopia > or = 0.75DS) and organic defects.

RESULTS

198 children (12.5%) had a significant visual disorder: strabismus (3.98%), eso:exo rate 5:1, anisometropia (2.34%), ametropia (5.82%), organic defects (0.38%). Organic disease caused visual handicap (< 6/18 in better eye) in 0.13%. Amblyopic visual impairment (6/18; 6/24-6/60) occurred in 1.13%; 2.02% had residual amblyopia (6/12 or worse).

CONCLUSIONS

Childhood visual disorders are a common problem. Unfavourable visual outcomes in esotropia are related to two sub-groups and particularly with poor concordance to treatment. Suggested strategies to improve outcomes include health promotion, an "Amblyopia Nurse" and a "Patch Club".

Refractive errors in normal children and children with down syndrome or cerebral palsy

BACKGROUND AND PURPOSE

The prevalence of refractive errors in the general population is between 12 to 18%. The objective of the present study was to determine the refractive errors in healthy children and compare these results in patients with Down syndrome and with cerebral palsy.

MATERIAL AND METHOD

The refractive errors in patients between 6 to 12 years without ophthalmologic conditions were studied. The patients were divided into three groups: normal children, children with Down syndrome, and children with cerebral palsy. The results were compared.

RESULTS

258 patient were included: 200 normal children, 29 with Down syndrome, and 29 with cerebral palsy. Ametropia was found in 79.5% in the group of normal children, 93.2% in children with Down syndrome, and in 100% in children with cerebral palsy. Patients requiring optical correction included 30% in normal children, 48.2% in patients with Down syndrome, and 41.1% in the cerebral palsy group. Hyperopia was the most frequent refractive error in all three groups. Most of the refractive errors were mild to moderate.

CONCLUSIONS

Refractive errors are more frequent in patients with Down syndrome and cerebral palsy compared with normal children.

Experimental parameters affecting the Morris water maze performance of a mouse model of Down syndrome

The Ts65Dn mouse is the most studied and genetically the most complete animal model of Down syndrome (DS) available. These mice display many DS-like features, including performance deficits in different behavioral tasks, motor dysfunction, and age-dependent loss of cholinergic markers in the basal forebrain. At present, the only robust data demonstrating a behavioral deficit potentially associated with learning and memory in Ts65Dn mice less than 6 months old have come from studies that used some variation of the Morris water maze task. However, the specific features of the water maze deficits seen in these animals are still poorly defined. This study is an initial attempt to bridge this knowledge gap. We investigated three major factors potentially influencing the performance of Ts65Dn mice in the water maze: (1) order in which the test is executed; (2) age of the animals; and (3) levels of aversiveness associated with the test. Measurements of plasma corticosterone levels and core body temperature after swimming were also carried out in additional subsets of mice. Overall, we found that the behavioral phenotype of Ts65Dn mice was milder than previously described in the literature. Additionally, Ts65Dn mice were significantly more responsive to potential stressors and more prone to swim-induced hypothermia than euploid control animals. More studies are needed to tease out further the potential effects of confounding factors on the performance of Ts65Dn mice.

Referral rates for a functional vision screening among a large cosmopolitan sample of Australian children

The aim of this study was to investigate the incidence of functional vision problems in a large unselected cosmopolitan population of primary school-age children and to investigate whether constant clinical criteria for functional vision problems would be implemented by the practitioners involved in the screening. Refractive errors, near point of convergence, stereopsis, strabismus, heterophoria and accommodative facility were assessed for 2697 children (3-12 years) of varying racial backgrounds living in Australia. The spherical component of the refractive error ranged from -7.75 to +9.50 D (mean +0.54 D, +/-0.79) with a distribution skewed towards hypermetropia; astigmatism ranged from 0 to 4.25 D (mean -0.16 D, +/-0.35). There was a trend towards less hypermetropia and slightly more astigmatism with age. Mean near point of convergence was 5.4+/-2.9 cm, heterophoria at far and near was 0.12+/-1.58delta exophoria and 1.05+/-2.53delta exophoria, respectively, 0.55% of children exhibited vertical phoria at near >0.5delta, accommodative facility ranged from 0 to 24 cycles per minute (cpm) (mean 11.2 cpm, +/-3.7), stereopsis varied from 20 to 800 s (") of arc with 50% of children having 40" or better. The prevalence of strabismus was particularly low (0.3%). Twenty percent of the children were referred for further assessment based on criteria of one or more of: stereopsis >70", accommodative facility <8 cpm, near point of convergence (NPC) >9 cm, near exophoria >10delta or near esophoria >5delta, shift in eso or exophoria > or = 4delta between distance and near, astigmatism > or = 1 D, myopia more than -0.75 D, or hyperopia >+1.50 D. Post-hoc analysis of the record cards seeking the reason for further assessment indicates that referrals appear to have been based upon clinical intuition rather than on a set number of borderline or unsatisfactory results.

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

PURPOSE

We have performed a population-based, longitudinal study on strabismus in children with Down syndrome. The aims of the study were to examine the frequency and type of strabismus, the age at onset, and the binocular potential.

METHODS

An unselected population of 60 children with Down syndrome born 1988-1999 was followed with repeated examinations. Mean follow-up time was 55+/-23 months (range 24--115). The alignment of the eyes was examined using Hirschberg corneal reflex test and cover test for near fixation. To evaluate binocular function, Titmus House Fly Test and Lang's stereo test were used.

RESULTS

Twenty-five patients (42%) had strabismus (21 esotropias, two exodeviations and two vertical deviations). Only one case of infantile esotropia was found, the other esotropias were acquired forms. The mean age at "onset" (e.g. when strabismus was first noticed) was 54+/-35 months. In the acquired esotropia group (n=20), 15 (75%) were associated with hypermetropia (mean spherical equivalent +4.3+/-1.7 D). Seventeen of the strabismic patients had an accommodation weakness. Eleven of the strabismus patients gave a clearly positive response to one or both stereotests.

CONCLUSIONS

The majority of the Down syndrome children with strabismus have an acquired esotropia and hence a potential for binocularity. Hypermetropia and accommodation weakness are probably important factors in esotropia in Down syndrome patients.