Pediatric ophthalmology and childhood reading difficulties: Amblyopia and slow reading

Comparison of binocular reading speed in patients with strabismus without amblyopia versus controls

OBJECTIVE

Amblyopia has been shown to slow reading speed. Limited literature exists on reading speed in strabismus without amblyopia. Our study compares binocular reading speed in patients with strabismus without amblyopia versus normal controls.

METHODS

We conducted a prospective study with 48 participants: 12 childhood-onset (onset <8 years of age) strabismus without amblyopia and 36 age- and education level-matched controls. Inclusion criteria were age 14-50 years, education >9 years, primary language English, best-corrected visual acuity >20/30 distance, and >N8 near either eye. Exclusion criteria were presence of other eye pathology or neurologic/cognitive conditions that may affect reading and previous treatment for strabismus/amblyopia. International Reading Speed Texts were used for binocular reading speed assessment. Each participant read 2 passages (passage 1 and 8), following all International Reading Speed Texts instructions. Reading time was measured using a stopwatch. Reading speed was calculated in words per minute (WPM).

RESULTS

Mean age for the strabismus group was 28.3 ± 11.1 and for the control group was 28.2 ± 11.0 years (P = 0.96). Mean education level for strabismus group was 14.2 ± 2.4 and control group was 13.8 ± 2.5 years (P = 0.62). Mean binocular reading speed for passage 1 for strabismus group was 192.0 and for control group was 220.0 WPM (P = 0.01). Mean binocular reading speed for passage 8 for strabismus group was 201.3 and for control group was 226.2 WPM (P = 0.04).

CONCLUSIONS

Patients with strabismus (without amblyopia) had slower binocular reading speed compared with controls. Further studies with eye tracking may provide more information. Strabismus, even without amblyopia, may affect reading performance and consequently vision-related quality of life.

Fine visuomotor skills in amblyopia: a systematic review and meta-analysis

BACKGROUND

Amblyopia is characterised by reduced visual acuity, poor binocular sensory fusion, and impaired or absent stereoacuity. Understanding the extent to which amblyopia affects everyday task performance is important to quantifying the disease burden of amblyopia and can assist clinicians to understand patients' likely functional capability.

METHODS

A systematic literature search identified published studies comparing fine visuomotor performance in either children or adults with amblyopia and those with normal binocular vision. The included studies (22 studies involving 835 amblyopes and 561 controls) reported results of self-perception patient reported outcome measures, tests of motor proficiency and video recorded reaching and grasping. The outcomes of 17 studies were grouped into four meta-analyses, with pooled results reported as standardised mean difference (SMD) with corresponding 95% CI.

RESULTS

Regardless of the cause of amblyopia (anisometropia, strabismus, mixed, deprivation), significant reduction in self-perception of physical competence and athletic competence (SMD=-0.74, 95% CI -1.23 to -0.25, p=0.003); fine motor skills scores (SMD=-0.86, 95% CI -1.27 to -0.45, p<0.0001); speed of visually guided reaching and grasping movements (SMD=0.86, 95% CI 0.65 to 1.08, p<0.00001); and precision of temporal eye-hand coordination (SMD=0.75, 95% CI 0.26 to 1.25, p=0.003) occurred in amblyopes compared with those with normal visual development.

CONCLUSION

Reports of the impact of amblyopia on fine motor skills performance find poorer outcomes in participants with amblyopia compared with those with normal vision development. Consistency in the outcome measure used to assess the functional impact of amblyopia would be valuable for future studies.

Trends in Geographic Distribution of Visual Disability - United States, 2010-2019

PURPOSE

We aimed to describe changes in the geographic distribution of self-reported visual impairment (VI) over the last decade (2010-2019) in the U.S.

METHODS

Our study was an analysis of publicly available data collected between 2010 and 2019 from the Census Bureau American Community Survey.

RESULTS

The mean overall prevalence of self-reported VI from 2010 to 2019 was 2.31% in the United States, and there was a significant increase in VI over the past decade from 2.25% in 2010-2014 to 2.37% in 2015-2019 (p < .001). VI was significantly higher in rural counties (3.58%), compared to urban (3.10%) or metropolitan counties (2.18%) (p < .001). In terms of geographic region, the South of the United States had the highest rate of VI (2.63%) (p < .001). For age groups > 17-years-old in the 2010-2019 data, women had higher rates of VI compared to men.

CONCLUSIONS

Prevalence of self-reported visual impairment has risen and disproportionately affects certain communities. This includes individuals living in the South, in rural counties, and women.

Kinematic Assessment of Fine Motor Skills in Children: Comparison of a Kinematic Approach and a Standardized Test

Deficits in fine motor skills have been reported in some children with neurodevelopmental disorders such as amblyopia or strabismus. Therefore, monitoring the development of motor skills and any potential improvement due to therapy is an important clinical goal. The aim of this study was to test the feasibility of performing a kinematic assessment within an optometric setting using inexpensive, portable, off-the-shelf equipment. The study also assessed whether kinematic data could enhance the information provided by a routine motor function screening test (the Movement Assessment Battery for Children, MABC). Using the MABC-2, upper limb dexterity was measured in a cohort of 47 typically developing children (7-15 years old), and the Leap motion capture system was used to record hand kinematics while children performed a bead-threading task. Two children with a history of amblyopia were also tested to explore the utility of a kinematic assessment in a clinical population. For the typically developing children, visual acuity and stereoacuity were within the normal range; however, the average standardized MABC-2 scores were lower than published norms. Comparing MABC-2 and kinematic measures in the two children with amblyopia revealed that both assessments provide convergent results and revealed deficits in fine motor control. In conclusion, kinematic assessment can augment standardized tests of fine motor skills in an optometric setting and may be useful for measuring visuomotor function and monitoring treatment outcomes in children with binocular vision anomalies.

Extended perceptive field revealed in humans with binocular fusion disorders

Binocular vision disorders or dysfunctions have considerable impact on daily visual activities such as reading. Heterophoria (phoria) is a latent eye misalignment (with a prevalence of up to 35%) that appears in conditions that disrupt binocular vision and it may affect the quality of binocular fusion. Our recent study, which used lateral masking (LM), suggests that subjects with binocular fusion disorders (horizontal phoria) exhibit an asymmetry and an abnormal pattern of both binocular and monocular lateral interactions, but only for the horizontal meridian (HM). The perceptive field (PF) is the fundamental processing unit of human vision and both masking and crowding depend on its size. An increased PF size is found in amblyopic populations or in young children. We hypothesized that the PF's size would be asymmetric only for the phoric group (larger along the HM). We estimated the PF's size using two different methods (LM with equal-phase and opposite-phase flankers). Phoric subjects exhibited a larger binocular PF size, only for the HM, confirming our hypothesis of an asymmetric PF size. However, the monocular PF size of phoric and control subjects was similar. Phoria affects the PF's size similarly to meridional amblyopia but without being attributed to abnormal refraction. We suggest that these findings could help explain the inter-observer variability found in the masking literature and the reading difficulties often encountered in subjects with high heterophoria. Since perceptual learning can reduce the PF's size, further investigation of training may provide a novel therapy to reduce some symptoms related to heterophoria.

Dichoptic and Monocular Visual Acuity in Amblyopia

PURPOSE

Standard-of-care assessment for children with amblyopia includes measuring amblyopic eye best-corrected visual acuity (AE BCVA) with the fellow eye occluded. By definition, this abolishes the interocular suppression fundamental to amblyopia. Thus, measured AE BCVA may not accurately represent that eye's contribution to natural binocular viewing. We compared dichoptic and monocular AE BCVA and examined whether any differences were associated with eye-hand coordination or reading speed.

DESIGN

Cross-sectional study.

METHODS

Dichoptic and monocular AE BCVA of children aged 6-12 years (42 with amblyopia, 24 with recovered normal AE BCVA, 30 control) were measured. Stereoacuity, suppression, eye-hand coordination, and reading speed were also assessed.

RESULTS

Overall, 81% of amblyopic children had worse dichoptic than monocular AE BCVA (mean difference=0.15±0.11 logMAR; P < .0001), and 71% of children with recovered normal AE BCVA had worse dichoptic than monocular AE BCVA (mean difference = 0.20±0.17 logMAR, P < .0001). Controls had no significant difference. The difference between dichoptic and monocular AE BCVA was correlated with performance in standardized aiming/catching (r = -0.48, 95% CI -0.72, -0.14) and manual dexterity tasks (r = -0.37, 95% CI -0.62, -0.06), and with reading speed (r = -0.38, 95% CI -0.65, -0.03).

CONCLUSIONS

Dichoptic AE BCVA deficits were worse than monocular AE BCVA deficits and were associated with reduced stereoacuity and suppression, consistent with the hypothesis that binocular dysfunction plays a role. Further, impaired eye-hand coordination and slow reading were associated with dichoptic, but not monocular, AE BCVA. Some children with amblyopia may benefit from extra time for school tasks requiring eye-hand coordination or reading.

Using a Computerised Staircase and Incremental Optotype Sizes to Improve Visual Acuity Assessment Accuracy

Background:

Given the impact of visual acuity results on diagnosis and management, it is essential that the test is accurate, determined by factors such as test-retest variability. Standardisation improves accuracy, which can be performed via a computerised staircase methodology. Standard clinical tests with scoring of 0.02 per optotype implies an incremental score per optotype despite optotype size remaining constant on each line. The aim of this study is to establish if near continuous incremental optotype display and scoring improves test-retest variability compared to current testing methods.

Methods:

A computerised three up, one down adaptive staircase was used to display Kay Picture optotypes on an LCD monitor. Three methods of visual acuity assessment were undertaken: ETDRS, Kay Pictures and computerised Kay Pictures. Tests were performed twice under standard clinical conditions.

Results:

One hundred nineteen adults were tested. Test-retest variability for computerised Kay pictures was 0.01 logMAR (±0.04, p = 0.001). Good levels of agreement were observed for computerised Kay pictures in terms of test-retest variability, where the test had the smallest mean bias (0.01 logMAR compared to 0.03 and 0.08 logMAR for Kay Pictures and ETDRS respectively) and narrowest limits of agreement. Participants performed better in computerised Kay pictures than Kay Pictures by 0.03 logMAR, and better in ETDRS than computerised Kay pictures by 0.1 logMAR.

Conclusion:

Computerised Kay pictures exhibited a low test-retest variability, demonstrating it is reliable and repeatable. This repeatability measure is lower than the test-retest variability of the ETDRS and Kay Pictures tests.

Interocular Suppression as Revealed by Dichoptic Masking Is Orientation-Dependent and Imbalanced in Amblyopia

Purpose

We investigate the orientation tuning of interocular suppression using a dichoptic masking paradigm in adult controls and amblyopes.

Methods

Fourteen adults with anisometropic or mixed amblyopia and 10 control adults participated in our study. Contrast sensitivity was measured by presenting a target Gabor in the tested eye and mean luminance in the untested eye (monocular) and by presenting a target in the tested eye and a bandpass oriented filtered noise in the other eye (masked). Interocular suppression was defined as the thresholds difference between the monocular and masked conditions for each eye. Interocular suppression was measured under parallel and orthogonal suppression configurations. The peak spatial frequency of the target and mask was 0.25 c/d in experiment 1 (low), 1.31 c/d in experiment 2 (mid), and 6.87 c/d in experiment 3 (high).

Results

The masking suppression induced by the amblyopic eye was less strong than that induced by the fellow eye. The suppression from the fellow eye was similar to that observed in the controls. Interocular suppression under parallel configuration was less strong than under orthogonal configuration in amblyopes at low and mid spatial frequency, but not at high spatial frequency.

Conclusions

We demonstrate that the abnormal interocular masking in amblyopia displays the expected characteristic of orientation selectivity expected of normal controls at low and mid spatial frequency, but not at high spatial frequency. The dichoptic masking imbalance between the eyes of amblyopes results in a net suppression of the amblyopic eye during binocular viewing, modeling clinical suppression.

Understanding the Impact of Residual Amblyopia on Functional Vision and Eye-related Quality of Life Using the PedEyeQ

PURPOSE

To evaluate the effect of residual amblyopia on functional vision and eye-related quality of life (ER-QOL) in children and their families using the Pediatric Eye Questionnaire (PedEyeQ).

DESIGN

Prospective cross-sectional study.

METHODS

Seventeen children with residual amblyopia (no current treatment except glasses), 48 visually normal controls without glasses, and 19 controls wearing glasses (aged 8-11 years) completed the Child 5-11 year PedEyeQ. One parent for each child completed the Proxy 5-11 PedEyeQ, Parent PedEyeQ. Rasch-calibrated domain scores were calculated for each questionnaire domain and compared between amblyopic children and controls.

RESULTS

PedEyeQ scores were significantly lower (worse) for children with residual amblyopia than for controls without glasses across all domains: Child PedEyeQ greatest mean difference 18 points worse on Functional vision domain (95% confidence interval [CI] -29 to -7; P < .001); Proxy PedEyeQ greatest mean difference 31 points worse on Functional vision domain (95% CI -39 to -24; P < .001); Parent PedEyeQ greatest mean difference 34 points worse on the Worry about child's eye condition domain (95% CI -46 to -22; P < .001). Compared with controls wearing glasses, PedEyeQ scores were lower for residual amblyopia on the Child Frustration/worry domain (P = .03), on 4 of 5 Proxy domains (P ≤ .05), and on 3 of 4 Parent domains (P ≤ .05).

CONCLUSIONS

Residual amblyopia affects functional vision and ER-QOL in children. Parents of amblyopic children also experience lower quality of life. These data help broaden our understanding of the everyday-life impact of childhood residual amblyopia.

Eye Tracking Abnormalities in School-Aged Children With Strabismus and With and Without Amblyopia

PURPOSE

To detect eye tracking abnormalities in children with strabismus in the absence or presence of amblyopia.

METHODS

A total of 100 patients aged 7 to 17 years were enrolled prospectively for 2 years from the pediatric ophthalmology clinic of the American University of Beirut Medical Center: 50 children with strabismus (including 24 with amblyopia) and 50 age- and gender-matched controls. Eye tracking with different paradigms was performed.

RESULTS

Mean age was 10.66 ± 2.90 years in the strabismus group and 10.02 ± 2.75 years in the control group. Demographic characteristics were similar with respect to vision, gender, and refraction. Four paradigms were tested using the eye tracker: (1) distance/near paradigm: patients with strabismus showed a lower fixation count and longer fixation at both distances and a tendency for decreased latency and percentage of fixation in distant elements; (2) reading paradigm: the strabismus group had a higher fixation count and duration, especially those without amblyopia; (3) location identification paradigm: strabismus group without amblyopia fixated less and with shorter duration on the most flagrant element; and (4) video paradigm: no differences in eye movements were noted.

CONCLUSIONS

Significant eye movement deficits were demonstrated in patients with strabismus compared to controls while reading text and identifying prominent elements in a crowded photograph. This was significant in the non-amblyopic subgroup. [J Pediatr Ophthalmol Strabismus. 2019;56(5):297-304.].

Fellow Eye Deficits in Amblyopia

Amblyopia is a neurodevelopmental disorder of the visual system, as a result of discordant visual experience during infancy or early childhood. Because amblyopia is typically defined as monocularly reduced visual acuity accompanied by one or more known amblyogenic factors, it is often assumed that the fellow eye is normal and sufficient for tasks like reading and eye-hand coordination. Recent scientific evidence of ocular motor, visual, and visuomotor deficits that are present with fellow eye monocular viewing and with binocular viewing calls this assumption into question. This clinical update reviews the research that has revealed fellow ocular motor and visual deficits and the effect that these deficits have on an amblyopic child's visuomotor and visuocognitive skills. We need to understand how to prevent and rehabilitate the effects of amblyopia not only on the nonpreferred eye but also on the fellow eye.

Visuomotor Behaviour in Amblyopia: Deficits and Compensatory Adaptations

Amblyopia is a neurodevelopmental visual disorder arising from decorrelated binocular experience during the critical periods of development. The hallmark of amblyopia is reduced visual acuity and impairment in binocular vision. The consequences of amblyopia on various sensory and perceptual functions have been studied extensively over the past 50 years. Historically, relatively fewer studies examined the impact of amblyopia on visuomotor behaviours; however, research in this area has flourished over the past 10 years. Therefore, the aim of this review paper is to provide a comprehensive review of current knowledge about the effects of amblyopia on eye movements, upper limb reaching and grasping movements, as well as balance and gait. Accumulating evidence indicates that amblyopia is associated with considerable deficits in visuomotor behaviour during amblyopic eye viewing, as well as adaptations in behaviour during binocular and fellow eye viewing in adults and children. Importantly, due to amblyopia heterogeneity, visuomotor development in children and motor skill performance in adults may be significantly influenced by the etiology and clinical features, such as visual acuity and stereoacuity. Studies with larger cohorts of children and adults are needed to disentangle the unique contribution of these clinical characteristics to the development and performance of visuomotor behaviours.

Reading ability of children treated for amblyopia

Previous studies have reported compromised reading ability in children with amblyopia. Standardized psychoeducational test norms have not been used; therefore, the practical consequences of poor reading ability, such as eligibility for reading supports at school, have not been assessed. Furthermore, several studies have used atypical reading conditions such as monocular or distant viewing. It is also not clear how amblyopia treatment impacts reading ability. Thus, the goal of this study was to use standardized tests to compare binocular reading performance in children treated for amblyopia to that of a large normative sample, as well as to the types of control groups used in previous studies. Children treated for strabismic or anisometropic amblyopia (N = 14) were compared to children treated for strabismus without amblyopia (N = 12) and to children with healthy vision (N = 39). Visual acuity, stereoacuity, interocular suppression, intellectual functioning, oral single-word reading (TOWRE-2), and oral paragraph reading (GORT-5) were assessed. The control group showed significantly higher single-word reading accuracy than the amblyopia and strabismus groups. However, mean performance for all groups was within the average range of the normative sample. While mean scores were in the average range, six children (four amblyopia, two strabismus) performed below average on the single-word reading task; four of these children also showed below average paragraph reading. Reading scores were not correlated with visual acuity in the patient groups. The results raise the possibility that both strabismus and amblyopia can disrupt reading ability, even following successful treatment, to an extent that might benefit from reading supports at school.

Multiple-Choice Answer Form Completion Time in Children With Amblyopia and Strabismus

Importance

Abnormal binocular experience during infancy or childhood from strabismus and/or anisometropia results in visual acuity deficits (eg, amblyopia) and impaired stereoacuity. These pediatric eye conditions have also been linked to slow reading and fine motor impairment.

Objective

To assess an academic-related fine motor outcome-multiple-choice answer form completion time-in children with amblyopia and strabismus.

Design, Setting, and Participants

In this cross-sectional study completed between May 2014 and November 2017 at a nonprofit eye research institute, 47 children with amblyopia treated for strabismus, anisometropia, or both, 18 children with nonamblyopic strabismus, and 20 normal controls were enrolled.

Exposures

Children were asked to transfer the correct answers from a standardized reading achievement test booklet to a multiple-choice answer form as quickly as possible without making mistakes or reading the text.

Main Outcomes and Measures

The time to complete the task was recorded and analyzed between groups.

Results

Of the 85 included children, 40 (47%) were female, the mean (SD) age was 10.09 (0.91) years, and the last mean (SD) grade completed was 3.42 (0.92). Compared with children in the control group (mean [SD] time to completion, 230 [63] seconds), children with amblyopia (mean [SD] time to completion, 297 [97] seconds; difference, 63 seconds; 95% CI, 24-102; P = .001) and children with nonamblyopic strabismus (mean [SD] time to completion, 293 [53] seconds; difference, 68 seconds; 95% CI, 21-115; P = .002) required approximately 28% (95% CI, 20-37) more time to fill out a multiple-choice answer form. Completion time was not associated with etiology, visual acuity, or stereoacuity.

Conclusions and Relevance

Multiple-choice answer forms typically accompany standardized testing in schools in the United States. Longer completion time in children with amblyopia or strabismus may affect a child's performance on tests using multiple-choice answer forms and may hinder academic success.