Importance of visual inputs quality for postural stability in strabismic children

Strabismus and postural control: a systematic review

The primary aim of this systematic review is to evaluate how postural balance and visual system are related in cross-eyed patients. The secondary goal is to assess the benefits of eye realignment on motor skills and body balance. Analyzing two different approaches: surgical or conservative, a systematic literature search was conducted using PubMed-Medline, Google Scholar and Cochrane Central in order to identify randomized controlled trials, case series and case-control studies which contained clinical evaluation of balance in strabismic patients as well as re-evaluation after surgery or conservative treatments via posturography to evaluate surface, length and mean speed of the center of pressure (CoP). A total of 11 studies were included in this review. The MINORS score is used to assess the methodological quality of the included studies, and its mean value was 12.8 for non-comparative studies and 17.5 for comparative studies. The postural balance was lower in strabismic patients compared with the control group, with statically higher value (p < 0.05) of surface, length and mean speed of the CoP in the study group. All patients show improvement in stability after surgery, as surface, length and mean speed of the CoP decreased after surgery in all the studies with statistical significance (p < 0.05).

Sufficiency of the BOT-2 short form to screen motor competency in preschool children with strabismus

Background

Strabismus is one of the most common visual disorders in children, with a reported prevalence of 2.48% in preschoolers. Additionally, up to 89.9% of preschool children with strabismus do not have normal stereopsis. Whether this lack of normal stereopsis affects the motor competency of preschool children with strabismus is unknown. The Bruininks-Oseretsky Test of Motor Proficiency Second Edition short form (BOT-2 SF) can be a useful tool for screening; however, its sufficiency as a diagnostic tool for children with various disorders is controversial.

Objective

The aims of this study were thus to examine motor competency in preschool children with strabismus by using the BOT-2 and to evaluate the usefulness of the BOT-2 SF to identify those at risk for motor competency issues.

Methods

Forty preschool children (aged 5–7 years) with strabismus were recruited, all of whom had abnormal stereopsis. The BOT-2 complete form (CF) was administered to all children. The BOT-2 CF was administered to all children. The scores of the BOT-2 SF were extracted from the relevant items of the BOT-2 CF for further analysis.

Results

The prevalence of children with strabismus who had below average performance in the composites of “Fine Manual Control”, “Manual Coordination”,”Body Coordination”, and “Strength and Agility” were 15%, 70%, 32.5%, and 5%, respectively, on the BOT-2 CF. Compared with these results, the sensitivity of the BOT-2 SF was 33.33% (95% CI = 7.49%–70.07%) and the specificity was 100% (95% CI = 88.78%–100%).

Conclusion

Preschool children with strabismus had a high prevalence of impaired motor competency, especially in fine motor competency. The BOT-2 SF was not as sensitive in identifying motor difficulties in preschool children with strabismus. Therefore, the BOT-2 CF is recommended for evaluating motor proficiency in preschool children with strabismus.

Sensory organization for postural control in children with strabismus-A systematic review and meta-analysis

BACKGROUND

Postural control requires the interaction of somatosensory, vestibular and visual systems to prevent disequilibrium. Children with strabismus have an impaired visual input which can lead to postural control deficits.

RESEARCH QUESTION

Does strabismus affect sensory organization for postural control in children?

METHODS

A systematic comprehensive search of multiple electronic databases for relevant articles was performed using a predetermined search strategy. Peer-reviewed journal publications that assessed sensory organization and postural performance in children with strabismus were included in this review. Methodological quality of the articles was evaluated using the modified Downs and Black quality assessment tool. A total of 10 articles were included in this review.

RESULTS

Eight of the 10 articles reviewed were included in the meta-analysis. Meta-analysis for Centre of Pressure CoP velocity (n = 3) (eyes open, stable support), was statistically significant (P = 0.01) in favor of controls over children with strabismus (MD, 3.08; 95 % CI -0.66, 5.51). Meta-analysis for CoP surface area (n = 5) (eyes open, stable support) was also statistically significant (P < 0.001) in favor of the control group (MD, 130.14; 95 % CI 70.01, 190.260). Meta-analysis with standardized mean difference (n = 6) for eyes open vs closed, stable support was statistically significant (P = 0.02) in favor of eyes open (MD, -0.94; 95 % CI, -1.74, -0.15). Overall, there was a high level of heterogeneity throughout the studies.

SIGNIFICANCE

This is the first systematic review of its kind to collate and synthesize evidence on the effect of strabismus on postural control in children. This review suggests that postural control performance in children with strabismus is inferior to that of age-matched control children. Further investigation is needed to understand the influence of the three sensory systems.

Comparison of postural control between strabismic and non-strabismic children

OBJECTIVE

To compare the postural control of children with strabismus versus non-strabismus children.

MATERIAL AND METHODS

Cross-sectional cohort study with a total of 171 children, including 73 children with esotropia, 24 with exotropia, and 74 controls. Postural control was determined using a dynamometric platform in a standing position in various conditions: eyes open and eyes closed, near and gaze fixation, and with and without foam pad. The studied variables were the area, the mean speed, and the lengths in the X and Y axis of the centre of pressure displacement.

RESULTS

Children with esotropia and exotropia had significantly higher mean values (speed, lengths of X and Y) compared to controls. In the open-eye, far distance fixation, and on foam pad, as well as under exam conditions; with eyes open, without foam pad, and far distance fixation, the exotropia values were higher than those of endotropia and controls. With eyes closed, there were no differences between the 3 groups under the described examination conditions, but their values were worse compared to their respective ones with eyes open.

CONCLUSIONS

The children with strabismus had a worse postural control than the non-strabismus ones. All of the them appeared to be more unstable with eyes closed than with eyes open, which demonstrates that vision plays an important relevant role in postural stability in both strabismus and non-strabismus children.

Postural Instability in Subjects With Usher Syndrome

This study investigated postural performances and vestibular impairment in Usher patients. The three groups studied were: 11 patients with Usher type I (with visual and vestibular impairment), 14 patients with Usher type II (with only visual impairment), and 14 healthy control subjects. Postural stability was measured with a Framiral Multitest Equilibre platform with three visual conditions: eyes open (EO), eyes closed (EC), and vision disturbed by optokinetic stimulation (OPT), and two different postural conditions: stable or unstable platform. The surface and mean velocity of the center of pressure displacement (CoP) were measured and a postural instability index (PII) was calculated. Usher type I and II patients were more unstable than control subjects, but only for the unstable platform. Patients with Usher type I (with severe vestibular impairment) were also significantly more unstable than patients with Usher type II (with normal vestibular function) on the unstable platform. The severity of the vestibular impairment was correlated with the surface of the CoP displacement. We suggest that poor postural control of Usher patients is due to the abnormalities in their visual and, when defective, vestibular inputs. Measurements of postural stability on an unstable platform can distinguish type I from type II Usher patients. We emphasize the importance of multisensory evaluation in these patients to guide development of personalized visuo-vestibular rehabilitation techniques to improve their postural stability and improve their quality of life.

Peripheral sensory information and postural control in children with strabismus

BACKGROUND

Sensory feedback from the visual system along with the vestibular and somatosensory systems is essential for the regulation of normal postural control. Children with strabismus and, therefore, with abnormal binocular vision, may have an altered perception of space and use different sets of cues to determine depth perception when compared with children without strabismus.

OBJECTIVE

To explore the postural control of children with and without strabismus, when the three sensory systems are challenged.

METHOD

Forty-six children (21 with strabismus and 25 age-matched controls) aged between 5 and 10 years completed ophthalmic screening and then underwent assessment for postural control, which included Paediatric Balance Scale (PBS) and six conditions of the Sensory Organization Test (SOT). Four primary outcome measures were: PBS summary score, Equilibrium Score (ES), Strategy Score (SS) and Sensory Analysis Score of the SOT.

RESULTS

A significant difference (P < 0.05) was observed between the strabismus and non-strabismus group in the PBS and, ES and SS of SOT condition 1. The Sensory Analysis scores were significantly different (P = 0.03) between the groups for 'Somatosensory'. Simple linear regression analysis suggested that the strabismus condition was significantly (P ≤ 0.02) associated with the PBS and, the ES and SS of condition 1, with a variance of 14.6%, 16.1% and 12.8%, respectively. Subgroup analysis suggested that age was a significant (P ≤ 0.001) correlate for balance scores in non-strabismus group (R² ranged from 32% to 58.4%), but not for the strabismus group.

SIGNIFICANCE

Postural control in children with strabismus is not equivalent to that of children without strabismus, when their somatosensory system is challenged. Additionally, the functional balance performance of children with strabismus is lower than their counterparts without strabismus. Collectively, the results suggest that the usual improvement in balance performance with increasing age is observed in children without strabismus but not in children with strabismus.

Beyond Rehabilitation of Acuity, Ocular Alignment, and Binocularity in Infantile Strabismus

Infantile strabismus impairs the perception of all attributes of the visual scene. High spatial frequency components are no longer visible, leading to amblyopia. Binocularity is altered, leading to the loss of stereopsis. Spatial perception is impaired as well as detection of vertical orientation, the fastest movements, directions of movement, the highest contrasts and colors. Infantile strabismus also affects other vision-dependent processes such as control of postural stability. But presently, rehabilitative therapies for infantile strabismus by ophthalmologists, orthoptists and optometrists are restricted to preventing or curing amblyopia of the deviated eye, aligning the eyes and, whenever possible, preserving or restoring binocular vision during the critical period of development, i.e., before ~10 years of age. All the other impairments are thus ignored; whether they may recover after strabismus treatment even remains unknown. We argue here that medical and paramedical professionals may extend their present treatments of the perceptual losses associated with infantile strabismus. This hypothesis is based on findings from fundamental research on visual system organization of higher mammals in particular at the cortical level. In strabismic subjects (as in normal-seeing ones), information about all of the visual attributes converge, interact and are thus inter-dependent at multiple levels of encoding ranging from the single neuron to neuronal assemblies in visual cortex. Thus if the perception of one attribute is restored this may help to rehabilitate the perception of other attributes. Concomitantly, vision-dependent processes may also improve. This could occur spontaneously, but still should be assessed and validated. If not, medical and paramedical staff, in collaboration with neuroscientists, will have to break new ground in the field of therapies to help reorganize brain circuitry and promote more comprehensive functional recovery. Findings from fundamental research studies in both young and adult patients already support our hypothesis and are reviewed here. For example, presenting different contrasts to each eye of a strabismic patient during training sessions facilitates recovery of acuity in the amblyopic eye as well as of 3D perception. Recent data also demonstrate that visual recoveries in strabismic subjects improve postural stability. These findings form the basis for a roadmap for future research and clinical development to extend presently applied rehabilitative therapies for infantile strabismus.

Postural Control and Emotion in Children with Autism Spectrum Disorders

Autism Spectrum Disorders subjects (ASD) are well known to have deficits in social interaction. We recorded simultaneously eye movements and postural sway during exploration of emotional faces in children with ASD and typically developing children (TD). We analyzed several postural and ocular parameters. The results showed that all postural parameters were significantly greater in children with ASD; ASD made significantly fewer saccades and had shorter fixation time than TD, particularly in the eyes, and especially for unpleasant emotions. These results suggest that poor postural control of ASD and their impaired visual strategies could be due to a lack of interest in social cognition, causing a delay in the development of the cortical areas, and thus could have an effect on their postural control.

Balance in subjects with congenital or early onset strabismus: Influence of age

Few studies have investigated the relationship between strabismus and balance, and those that do exist focused on patients within a limited age range, while no studies on possible age-related changes have yet been conducted. Therefore, the aim of our study was to investigate whether the balance strategies adopted by patients with congenital or early onset strabismus change with age. Forty strabismic patients and 36 healthy subjects were enrolled in the study. Both patients and healthy subjects were divided into three subgroups according to age (children, adolescents, and adults) and underwent a stabilometric evaluation. When we compared the whole group of strabismic patients with the group of healthy subjects, we found that the center of pressure area and the trunk oscillations in the former were significantly different from those in the latter; when we considered the three age groups separately, only values in children with strabismus were different from those in the age-matched control group of healthy subjects. Strabismus was found to affect balance in children by inducing a postural strategy characterized by a reduction in physiological trunk oscillations. Gaining a better insight into postural control in strabismic subjects and its evolution with age may be crucial to improving rehabilitation in such patients and planning tailored rehabilitation treatment.