The development of myopia among children with intermittent exotropia

Effects of basic type of intermittent exotropia on myopic shift in children: a 12-month observational study

Background

To investigate the effect of basic intermittent exotropia (IXT) on myopic shift in children during 12-month follow-up.

Methods

165 children aged 4-15 years were recruited prospectively in this study and divided into 3 groups: Group A, consisted of 64 patients with basic IXT without surgery; Group B, consisted of 51 patients 1-month after IXT-corrected surgery; and Group C, consisted of 50 patients without any form of strabismus. All patients underwent assessments of spherical equivalent (SE), axial length (AL), exodeviation, and binocular function relating to accommodation and convergence. Examinations were conducted at baseline and 12-month. SE and AL changes were compared among groups. Univariate and multivariate linear analyses were employed to investigate the association between myopic shift and IXT, as well as other clinical parameters.

Results

Three groups showed comparable ages, genders and SEs at baseline (all P > .05). During 12-month follow-up, the rate of myopic shift varied among groups. Significant differences in SE progression (P = .006) and AL elongation (P = .014) between Group A and Group C were observed. Although SE progression and AL elongation in Group B were less than Group A, no significant differences were found (P = .125; P = .038). In the multivariate analysis, increases in exodeviation angle were significantly associated with both SE progression (β = 0.010, P = .041) and AL elongation (β = -0.005, P = .026). Each one prism diopter increase in the exodeviation angle was correlated with a 0.01D SE progression and a 0.005 mm AL elongation.

Conclusions

Children with basic IXT exhibited faster myopia shift compared to those without strabismus. Although surgical correction of strabismus appeared to slow this process, the effect was not statistically significant. Furthermore, greater increase in exodeviation angle was associated with higher rate of SE progression and AL elongation.

Trial registration

The study was approved by the Ethics Committee of Beijing TongRen Hospital (approved number: TRECKY2020-142, approved date: 2020.10.30).

Clinical features in patients with acquired intermittent and constant exotropia who underwent surgery

BACKGROUND

acquired exotropia mostly manifests as an intermittent form, and very few cases show constant exotrpia. However, the differences in the clinical features of the constant and intermittent exotropia patients has not been clear yet.

METHODS

We retrospectively evaluated 6159 patients with exotropia from 2012 to 2022 in Farabi Eye Hospital, Tehran, Iran. The preoperative data collected were best corrected distance visual acuity (BCVA), spherical equivalent refractive error, amount and laterality of exotropia, presence of amblyopia and anisometropia.

RESULTS

The mean age at the time of surgery was 21.9 ± 13.8 (range, 2-77) years and 3104 (50.4%) cases were male. Constant and intermittent exotropia were observed in 4244 (68.9%) and 1915 (31.1%) cases, respectively. BCVA was significantly worse in the constant than in the intermittent group (P < .05). In cases with dominancy, the non-dominant eye in intermittent exotropia patients showed significantly more minus spherical equivalent (-1.28 ± 3.03 diopter) compared to the constant group (-0.63 ± 4.41 diopter) (P < .001). Moreover, the mean angle of horizontal and vertical deviation at distance and near in patients with constant exotropia was significantly higher than in the intermittent cases, either when there was a dominance in one eye or in cases with no dominance (P < .001). Amblyopia was found in 38.3% of cases with constant and 13.1% with intermittent exotropia (P < .001). Anisometropia was observed in 821 (19.34%) with constant and 88 (4.6%) with intermittent exotropia (P < .001).

CONCLUSION

Constant exotropic patients had worse BCVA, larger angle of deviation, and higher prevalence of amblyopia and anisometropia compared to the intermittent cases.

Exploring the Link: A Systematic Review and Meta-Analysis on the Prevalence and Association Between Refractive Errors and Intermittent Exotropia

Background and Aims

Refractive errors and intermittent exotropia are prevalent conditions in pediatric populations, impacting visual development and quality of life. Despite the co-occurrence of conditions such as myopia, hypermetropia, and astigmatism with strabismus, comprehensive analyses of their coexistence are limited. This study aims to investigate the prevalence and characteristics of refractive error among children with intermittent exotropia and find the correlation between the angle of deviation for far and near with factors like mean spherical equivalent and age.

Methods

A systematic review and meta-analysis were conducted in accordance with PRISMA guidelines. PubMed and Scopus databases were searched up to February 13, 2024. Inclusion criteria encompassed studies detailing clinical presentation, management strategies, and outcomes, while exclusion criteria eliminated review articles, conference abstracts, animal research, and studies with inadequate clinical information. Data extraction and quality assessment were independently performed by multiple reviewers, with discrepancies resolved through consensus. Forest plot was used to show the mean spherical equivalent and the angle of deviation, while publication bias was demonstrated using funnel plot with Egger test.

Results

The search yielded 932 articles, with 23 meeting the inclusion criteria. Studies represented four geographical regions, with a combined sample size of 5407 participants aged 3-10 years. The mean refractive errors varied widely, with an overall pooled mean of -1.787 (95% CI: -5.392 to 1.818). Overminus lens therapy and surgical interventions were common management strategies, with surgery prevalent in cases with higher distant angle deviation. The myopia was more prevalent than hypermetropia (26.82%/16.10%). Meta-regression showed that the mean spherical equivalent had a significant effect on the angle of deviation far and near.

Conclusion

There was a significant correlation between myopia and intermittent exotropia in Middle Eastern and Asian pediatric populations. Myopia is notably more prevalent with significant effect of mean spherical equivalent on near-angle deviation.

0.01% Atropine Eye Drops in Children With Myopia and Intermittent Exotropia: The AMIXT Randomized Clinical Trial

Importance

Exotropia and myopia are commonly coexistent. However, evidence is limited regarding atropine interventions for myopia control in children with myopia and intermittent exotropia (IXT).

Objective

To evaluate the efficacy and safety of 0.01% atropine eye drops on myopia progression, exotropia conditions, and binocular vision in individuals with myopia and IXT.

Design, Setting, and Participants

This placebo-controlled, double-masked, randomized clinical trial was conducted from December 2020 to September 2023. Children aged 6 to 12 years with basic-type IXT and myopia of -0.50 to -6.00 diopters (D) after cycloplegic refraction in both eyes were enrolled.

Intervention

Participants were randomly assigned in a 2:1 ratio to 0.01% atropine or placebo eye drops administered in both eyes once at night for 12 months.

Main Outcomes and Measures

The primary outcome was change in cycloplegic spherical equivalent from baseline at 1 year. Secondary outcomes included change in axial length (AL), accommodative amplitude (AA), exotropia conditions, and binocular vision at 1 year.

Results

Among 323 screened participants, 300 children (mean [SD] age, 9.1 [1.6] years; 152 male [50.7%]) were included in this study. A total of 200 children (66.7%) were in the atropine group, and 100 (33.3%) were in the placebo group. At 1 year, the 0.01% atropine group had slower spherical equivalent progression (-0.51 D vs -0.75 D; difference = 0.24 D; 95% CI, 0.11-0.37 D; P < .001) and AL elongation (0.31 mm vs 0.42 mm; difference = -0.11 mm; 95% CI, -0.17 to -0.06 mm; P < .001) than the placebo group. The mean AA change was -3.06 D vs 0.12 D (difference = -3.18 D; 95% CI, -3.92 to -2.44 D; P < .001) in the atropine and placebo groups, respectively. The 0.01% atropine group had a decrease in near magnitude of exodeviation whereas the placebo group had an increase (-1.25 prism diopters [PD] vs 0.74 PD; difference = -1.99 PD; 95% CI, -3.79 to -0.19 PD; P = .03). In the atropine vs placebo group, respectively, the incidence of study drug-related photophobia was 6.0% (12 of 200 participants) vs 8.0% (8 of 100 participants; difference = -2.0%; 95% CI, -9.4% to 3.7%; P = .51) and for blurred near vision was 6.0% (12 of 200 participants) vs 7.0% (7 of 100 participants) (difference = -1.0%; 95% CI, -8.2% to 4.5%; P = .74).

Conclusions and Relevance

The findings of this randomized clinical trial support use of 0.01% atropine eye drops, although compromising AA to some extent, for slowing myopia progression without interfering with exotropia conditions or binocular vision in children with myopia and IXT.

Trial Registration

Chinese Clinical Trial Registry Identifier: ChiCTR2000039827.

Refractive Profile of Surgical Patients with Intermittent Exotropia: A Large-Sample Cross-Sectional Study in Southern China

PURPOSE

To describe the refractive profile of surgical patients with intermittent exotropia (IXT) residing in southern China.

METHODS

Medical records of patients who received strabismus surgery between June 2014 and August 2020 were retrospectively reviewed. Clinical data, including age, sex, refractive errors, preoperative angle of deviation, types of exotropia, accommodative convergence to accommodation ratio (AC/A ratio) and stereopsis, were investigated.

RESULTS

A total of 2250 patients were included, and 93.6% of patients were younger than 30 years of age. The mean angle of exodeviation was 37.0 ± 14.7 prism degree (PD) and 37.5 ± 15.8 PD at distance and near, respectively. Mean spherical equivalent refraction (SER) values were -0.7 ± 2.4 D and -0.8 ± 2.5 D in the dominant eye and nondominant eye, respectively. Significant differences in SER were observed between the dominant eye and nondominant eye among children at 6 years old or younger. The percentage of myopia increased from 11.0% in children (≤6 years old) to 77.9% in teenagers (13-18 years of age). Significant positive associations between the magnitude of exodeviation and the magnitude of myopia were observed (p < 0.0001). Patients with convergence insufficiency type IXT (p < 0.0001) or AC/A < 2 (p < 0.05) showed a greater magnitude of myopia. The mild hyperopia group included a larger proportion of subjects showing a certain degree of stereopsis (p < 0.05).

CONCLUSIONS

Myopia was present in more than half of our patients (51.2%), which is much higher than the percentage in the general population of southern China. Patients with convergence insufficiency, an AC/A ratio < 2, or a larger angle of deviation tended to have a greater magnitude of myopia.

Predicting the child who will become myopic - can we prevent onset?

Myopia has become a global epidemic with significant public health impacts. Identifying the child at risk of developing myopia, i.e. the pre-myopic child and implementing strategies to prevent the onset of myopia, could significantly reduce the burden of myopia on an individual and society. This paper is a review of publications that have identified ocular characteristics of children at risk of future myopia development including a lower than age normal amount of hyperopia and accelerated axial length elongation. Risk factors associated with increased risk of myopia development such as education exposure and reduced outdoor time, and strategies that could be implemented to prevent myopia onset in children are also explored. The strong causal role of education and outdoor time on myopia development suggests that lifestyle modifications could be implemented as preventative measures to at-risk children and may significantly impact the myopia epidemic by preventing or delaying myopia onset and its associated ocular health consequences.

Refractive change in pediatric patients with intermittent exotropia

PURPOSE

To determine the relationship between intermittent exotropia (IXT) and refractive change and the effects of the methods applied in IXT follow-up on refractive change.

METHOD

The medical records of 228 patients with IXT (group 1) and 110 patients without strabismus (group 2) who were followed between 2008 and 2022 were analyzed retrospectively. Group 1 was divided into three subgroups: overminus correction (group 1A), patients who underwent surgery (group 1B), and patients who were observed (group 1C).

RESULTS

Annual myopic progression was -0.21 ± 0.32 D (range, -1.26 to +1.92) in group 1 and -0.07 ± 0.30 D (range, -1.13 to +1.00) in group 2 (P < 0.001). Annual myopic progression was -0.26 ± 0.29 D (range, -1.26 D to +0.12 D) in group 1A, -0.25 ± 0.35 D (range, -1.15 D to +0.25 D) in group 1B, and -0.19 ± 0.33 D (range, -1.12 D to +1.92 D) in group 1C. There was no difference in annual myopic progression between the subgroups (P = 0.670). The annual change in myopic refraction between each of the group 1 subgroups and group 2 was statistically significantly different (P < 0.001, P = 0.023, P < 0.001, resp.).

CONCLUSIONS

Myopia progression was significantly greater in children with IXT than in the normal population. Myopia progression did not vary with exotropia treatment.

Comparison of biometric and refractive changes in intermittent exotropia with and without overminus lens therapy

BACKGROUND

Overminus lens is an effective non-surgical treatment of intermittent exotropia (IXT). Whether this treatment causes development of myopia is recently debated. This study evaluated ocular biometric changes in IXT children treated with and without overminus lens.

METHODS

Children with IXT were randomly assigned to control and overminus groups. Cycloplegic refraction, axial length and other parameters (keratometry, anterior chamber depth and lens thickness) were evaluated for up to 30 months and compared between the groups. Axial length to corneal curvature (AL/CR) ratio was examined as an indicator of myopia progression. Changes prior to and after overminus were also assessed in a subgroup.

RESULTS

Mean age of the total 84 subjects (58% women) was 7.2 years (range 4-15 years). Baseline refractive and biometric parameters of 39 control and 45 overminus subjects were not significantly different. Mean±SD change in refraction was -0.34±0.45D in controls and -0.41±0.66D in overminus group (p=0.527). AL increased by 0.29±0.20 millimetre (mm) in controls and 0.28±0.23 mm in overminus group (p=0.766). In the subgroup, the changes before and after overminus therapy was not significantly different (p>0.05). AL/CR ratio was maintained from baseline to follow-up visit (p=0.298) in both groups.

CONCLUSION

No significant differences in biometry or refraction were found between the two groups and before and after the therapy. We conclude that the overminus therapy in children, not accounting for other myopia risk factors, does not affect normal refractive growths.

Myopic progression in school-aged children with moderate intermittent exotropia

Objective

It is still controversial whether intermittent exotropia (IXT) affects myopic progression during the critical period of visual development. This study retrospectively analyzed the long-term myopic changes and the impact of IXT surgery on myopic progression in school-aged children with moderate IXT.

Methods

The medical records of 65 children from 5 to 13 years old with or without IXT between 2015 and 2021 were retrospectively reviewed. Patients whose spherical equivalent refraction (SER) were less than -3.00 diopter (D) were included and divided into three groups: IXT surgery group (Group A), which comprised 22 IXT patients who received IXT surgery, IXT observation group (Group B), which comprises 19 IXT patients who only received long-term observational follow-up; and normal control group (Group C), which comprised 24 normal controls without IXT. The main outcome measurement was the rate of myopic progression, which was defined as the mean myopic shift in SER per year.

Results

The 3- and 5-years long-term follow-up rates of myopic progression were -0.47 ± 0.28 D per year and -0.48 ± 0.23 D per year respectively in Group B, and those were significantly slower than that in Group C (-0.73 ± 0.32 D per year and -0.76 ± 0.19 D per year respectively). However, there was no significant difference in the rate of myopic progression between Group A and B or between Group A and C.

Conclusion

Moderate IXT may have lower rate of myopic progression in school-aged children. Whether IXT surgery influence the rate of myopic progression still needs further study.

Comparison of Myopia Progression among Myopic Children with Intermittent Exotropia and No Strabismus

SIGNIFICANCE

Myopia is a highly prevalent condition in the pediatric population that is commonly comorbid with intermittent exotropia. Our study found a trend toward significance in the reduction of myopia progression with strabismus correction surgery. Further investigations characterizing the interaction between myopia and strabismus may help inform future management guidelines.

PURPOSE

This study describes and compares myopic progression in the pediatric population with and without intermittent exotropia and its interaction with corrective strabismus surgery.

METHODS

This study analyzed a retrospective cohort of 1239 pediatric myopic patients who were evaluated by pediatric ophthalmologists and optometrists at a tertiary care center from 2012 to 2020. The main outcome measures were the trends in refractive error over time in those with and without intermittent exotropia as well as trends in those who did and did not undergo strabismus surgery.

RESULTS

A total of 275 patients (22%) were identified to have intermittent exotropia, and 12 (4.4%) from this group underwent surgical correction in the study period. No statistically significant difference was identified in myopic progression between those with intermittent exotropia and those without strabismus, and no difference was found in mean annual spherical equivalent change between intermittent exotropia patients who did not undergo surgery compared with those who did.

CONCLUSIONS

Pediatric myopic patients generally experience progression in the condition for several years independent of concurrent intermittent exotropia. Corrective strabismus surgery was not found to alter the natural history of myopia in children, although a reduction in myopic progression in surgically treated patients trended toward significance. Increases in the prevalence of different treatment strategies will necessitate further studies to determine best practices for this population.

Comparing myopic error in patients with basic and convergence insufficiency intermittent exotropia in China

PURPOSE

To compare the degree of myopia between the dominant and non-dominant eyes in teenagers with intermittent exotropia (IXT) in China.

METHODS

A total of 199 IXT patients with myopia were included in this retrospective study and were divided into two groups according to the difference between near and distance exodeviation: basic IXT and convergence insufficiency (CI) IXT. Refractive errors were analyzed by spherical equivalent (SE) values. Patients were further stratified into anisometropia group and non-anisometropia group based on binocular SE values difference greater than 1.0D or not.

RESULTS

There were 127 patients in the CI IXT group, with a near deviation of 46.94 ± 20.53 prism diopters (PD) and a distance deviation of 28.36 ± 14.34 PD, and there were 72 (36.2%) patients in the basic IXT group, with a near deviation of 37.68 ± 22.21 PD and a distance deviation angle of 33.21 ± 23.96 PD. The near exodeviation was significantly larger in the CI group than in the basic IXT group(P < 0.001). In the CI IXT group, the mean SE was - 2.09 ± 1.45 diopters (D) in the dominant eye and - 2.53 ± 1.44D in the non-dominant eye, while in the basic IXT group, the mean SE was - 2.46 ± 1.56D in the dominant eye and - 2.89 ± 1.37D in the non-dominant eye. The anisometropia group included 43 patients, while non-anisometropia group included 156 patients. The near and distance exodeviation in the anisometropia group were 45.26 ± 24.41 PD and 33.53 ± 23.31 PD, respectively, and those in the non-anisometropia group were 43.42 ± 20.69 PD and 29.07 ± 16.84 PD, respectively. There were no significant differences in near and distance deviation (P = 0.78 and P = 0.73 respectively) between the two groups. The SE of the dominant eye was less myopic than of the non-dominant eyes in both the CI and anisometropia groups (P = 0.002 and P < 0.001, respectively).

CONCLUSIONS

Our study revealed that convergence insufficiency IXT is more common than the basic type in pediatric myopic population and is characterized by higher inter-eye differences of myopia. The dominant eye was found to be less myopic in IXT patients, particularly in those with convergence insufficiency and anisometropia.

Correlation between bilateral lateral rectus muscle recession and myopic progression in children with intermittent exotropia

Although several studies have reported about the relationship between the surgical correction of intermittent exotropia and myopic progression, it remains unclear, unlike the relationship between esotropia and hyperopia. Thus, this retrospective case control study evaluated the impact of bilateral lateral rectus recession in intermittent exotropia on myopic progression. This study included 388 patients with intermittent exotropia. The refractive errors and degree of exodeviation at each follow up period were analyzed. The rate of myopic progression was -0.46 ± 0.62 diopter (D)/year in patients who underwent surgery and -0.58 ± 0.78 D/year in patients who did not, with no significant difference between them (p = 0.254). Patients who had recurrences of more than 10 prism diopters were compared with patients who did not have. The rate of myopic progression was -0.57 ± 0.72 D/year in the recurrent group and -0.44 ± 0.61 D/year in the non-recurrent group, with no significant difference between them (p = 0.237). Patients with fast myopic progression had more recurrence than patients with slow progression (p = 0.042). Moreover, recurrence had a positive correlation with fast myopic progression (OR = 2.537, p = 0.021). Conclusively, the surgical correction of intermittent exotropia did not influence myopic progression.

Patients with Intermittent Exotropia and Exophoria Exhibit Non-aggravated Lens Decentration After Orthokeratology Application: The Nanjing Strabismus Cohort

INTRODUCTION

There is a high prevalence of intermittent exotropia and exophoria in myopic populations, and orthokeratology is one of the effective interventions to control myopia progression in children. However, it is still obscure whether intermittent exotropia and exophoria children could wear orthokeratology without experiencing aggravated lens decentration.

METHODS

This was a multi-center, prospective cohort study. A total of 123 myopic participants aged 8-14 years were recruited, where conditions of deviation included intermittent exotropia, exophoria, and orthophoria. Uncorrected visual acuity and corneal topography data were obtained at baseline and after 1 month of wearing orthokeratology lens. Lens decentration was analyzed in a MATLAB program. Magnitude of deviation and refractive errors were evaluated prior to orthokeratology treatment. Fisher's exact test, ANOVA test, and univariate and multivariate linear regression models were established to evaluate the role of magnitude of deviation in lens decentration.

RESULTS

There was no significant difference in magnitude and direction of lens decentration among three groups (magnitude: F = 1.25, P = 0.289; direction: Fisher = 9.91, P = 0.078). According to scale division of decentration, 1 (2.6%) intermittent exotropia subject, 2 (3.8%) exophoria subjects, and 1 (3.0%) orthophoria subject experienced severe decentration (Fisher = 1.10, P = 0.947). Inferotemporal decentration was most common among all subjects (intermittent exotropia 50.0%, exophoria 76.9%, orthophoria 72.7%). Univariate and multivariate linear regression analyses revealed that magnitude of deviation was not an independent risk factor for lens decentration [β = -0.00, 95% confidence interval (CI) -0.01-0.00, P = 0.180], while surface asymmetry index (SAI) (β = 0.21, 95% CI 0.02-0.40, P = 0.028) and surface regularity index (SRI) (β = -0.39, 95% CI -0.66 to -0.13, P = 0.004) had significant correlation with polar decentration.

CONCLUSION

Patients with intermittent exotropia and exophoria exhibit non-aggravated lens decentration after orthokeratology application. Thus, lens decentration is not the concern for orthokeratology prescription.

Effect of Spectacle Lenses with Highly Aspherical Lenslets on Binocular Vision and Accommodation in Myopic Children with and without Intermittent Exotropia

Purpose

To evaluate the influence of spectacle lenses with highly aspherical lenslets (HAL) on binocular vision and accommodation in myopic children with intermittent exotropia (IXT) and compare the changes after wearing HAL in binocular vision and accommodation in myopic children with or without IXT.

Method

Forty myopic subjects aged 8–12 years were recruited: 20 with IXT and 20 visually normal children. Stereoacuity, phoria, accommodative facility, fusional vergence, vergence facility, near point of convergence, amplitude of accommodation, and accommodative response (AR) were measured by wearing HAL or single vision spectacle lenses (SVL) in a random order after adapting for 20 minutes. Accommodative microfluctuation (AMF) was defined as the standard deviation of AR. Changes in binocular vision and accommodation after wearing HAL were compared between the two groups.

Results

No significant differences were found in binocular vision after wearing HAL versus SVL in either group (all P > 0.05). A greater AMF was found after wearing HAL than after wearing SVL in both groups (0.04 D, 95% confidence interval (CI), 0.03 to 0.05 D, P < 0.001 for the IXT group; 0.05 D, 95% CI, 0.03 to 0.07 D, P < 0.001 for the visually normal group); however, the other accommodation parameters did not change significantly (all P > 0.05). There were no differences in the changes after wearing HAL in any parameter between the two groups (all P > 0.05).

Conclusion

HAL did not significantly change the binocular vision and accommodation for myopic children with or without IXT except for AMF in the short term.

Accommodative responses under various viewing conditions in surgical patients with intermittent exotropia: an institutional, retrospective study

Purpose

To investigate the difference of spherical equivalent (SE) and pupil diameter in adult patients with intermittent exotropia (IXT) under various viewing conditions before and after surgery.

Methods

We retrospectively analyzed the medical records of 23 adult patients who underwent a surgery for IXT. The angle of deviation was measured by the prism and alternative cover test. Refractive error and pupil diameter were measured using the Grand Seiko WAM-5500 open-field autorefractor under binocular and monocular viewing conditions when patients stared at distance (6 m) and near (33 cm). Regression analyses were performed between accommodative load and the angle of deviation.

Results

Twenty-three patients (10 males, 13 females) with a mean age of 31.17±8.95 years, of whom 13 (56.5%) had the right eye as the dominant eye. The mean angle of deviation at near and at distance was 69.57±26.37 and 65.43±28.92 prism diopters respectively. There were no significant differences in accommodative response and pupil diameter between the dominant and non-dominant eyes. SE decreased when patients changed from monocular to binocular viewing, and from distant to near viewing (all P< 0.05), so as the pupil diameter (all P< 0.001). During binocular, not monocular viewing, SE was significantly greater after operation than it was before operation (P< 0.001). Accommodative load and pupillary constriction narrowed (p< 0.001) after the operation. Linear regression analysis showed a correlation between the angle of deviation at distance and accommodative load at distance (r²=0.278, p=0.010) and at near (r²=0.332, p=0.005).

Conclusion

In order to maintain ocular alignment, patients with IXT suffer a large accommodative load, which is related to the angle of deviation. Surgery helps eliminating extra accommodation.

Optimised minus lens overcorrection for paediatric intermittent exotropia: A randomised clinical trial

BACKGROUND

Aim of this study was to evaluate the efficacy of a novel algorithm to customise overminus lens therapy in intermittent exotropia (IXT) based on clinical factors associated with control of the deviation.

METHODS

Clinical parameters in IXT vary among individuals. Based on individual's physiological factors, an algorithm was developed. Children aged between 4 and 15 years with IXT were randomised into OML and observation groups. Participants in the observation group were corrected for any significant refractive error. IXT control score, angle of deviation, refraction, axial length and stereopsis were examined at baseline and follow up ranging between 6 and 15 months and compared. Compliance and tolerance to OML was determined by a symptom survey.

RESULTS

The OML power ranged between -1.00D and - 6.25D. Of the total 141 participants (mean age 6.8 ± 2.5 year), 77 were in the OML and 66 were in observation group. IXT control score improved (mean difference - 2.5 ± 1.1; p < 0.001) and angle of deviation reduced (6.9 ± 7.2pd; p < 0.001) significantly in the OML group only. Compliance rate to OML wear was 80%; 90% never or rarely experienced asthenopia symptoms. Slightly greater myopic shift (-0.36 ± 0.53D vs. -0.18 ± 0.55D) and change in axial length (0.17 vs. 0.14 mm) were observed in the OML group, but these differences were not statistically significant.

CONCLUSIONS

A customised OML, calculated using this novel algorithm was effective in improving distance control, angle of deviation and stereopsis. Glasses wear was highly tolerable.

Association between refractive errors and horizontal strabismus: the Korea National Health and Nutrition Examination Survey

PURPOSE

To investigate the association between refractive error and horizontal strabismus based on a Korean population-based survey.

METHODS

The study included 22,887 participants >5 years of age who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) from 2008 to 2011. Refractive error was classified into myopia, hyperopia, astigmatism, and anisometropia. The association between refractive error and exodeviation or esodeviation was assessed using multivariate logistic regression analysis.

RESULTS

After adjusting for potential confounders, the analyses revealed an increased odds ratio (OR) for exodeviation with an increasing trend according to the severity of myopia (mild myopia, OR = 1.36 [95% CI, 1.11-1.66]; moderate myopia, OR = 1.75 [95% CI, 1.36-2.26]; severe myopia, OR = 2.01 [95% CI, 1.50-2.69]; P_trend < 0.001). Hyperopia was not associated with exodeviation (P = 0.273). There were also significant associations for exodeviation with astigmatism (OR = 1.36 [95% CI, 1.16-1.59; P < 0.001]) and anisometropia (OR = 1.78 [95% CI, 1.38-2.30; P < 0.001]) In comparison, esodeviation was significantly associated with hyperopia (OR, 10.24 [95% CI, 4.43-23.70; P < 0.001]) and anisometropia (OR, 5.16 [95% CI, 2.27-11.76; P < 0.001]), while no significant association was found with myopic degree (P = 0.170) or astigmatism (P = 0.816).

CONCLUSIONS

Refractive error was closely associated with exodeviation and esodeviation. These risk associations should be considered when managing refractive errors.

Schielen oder nicht Schielen? – Strabismus divergens intermittens, eine besondere Schielform

Hintergrund

Schielen tritt bei ca. 5–7 % der gesunden Kinder auf. Außenschielen ist mit 1,24 % weltweit seltener als Innenschielen. Der Strabismus divergens intermittens stellt mit 40–90 % die häufigste divergente Schielform dar. Das klinische Bild wurde von vielen AutorInnen beschrieben. Dennoch stellt es durch die Variabilität der Befunde eine therapeutische Herausforderung dar.

Material und Methode

Es wurden im Rahmen einer Literaturrecherche die Ergebnisse von Studien zum Strabismus divergens intermittens mit Fokus auf klinisches Bild, Untersuchungskriterien und Therapieansätze gesammelt und die Ergebnisse dargestellt.

Resultate

Der Strabismus divergens intermittens zeichnet sich durch eine besondere Binokularsituation und bisher ursächlich nicht vollends geklärte Symptome (Photophobie, Kneifen) aus. Konservative Therapien dienen der Entlastung des visuellen Systems, in vielen Fällen ist aber eine Schieloperation nötig. In der präoperativen Beurteilung ist der Stabilität des Schielwinkels besonderes Augenmerk zu schenken, als Entscheidungshilfe hinsichtlich Schieloperation hat sich der New Castle Control Score bewährt.

Schlussfolgerung

Die klinischen Charakteristika des Strabismus divergens intermittens sind klar beschrieben. Hinsichtlich therapeutischer Ansätze zeigen sich im internationalen Vergleich Unterschiede. Die Bedeutung der Einbeziehung der Eltern („shared decision making“) bei der Beurteilung der Schielhäufigkeit und bei der Operationsentscheidung ist zu betonen.

Prevalence of Heterophoria in Tibetan Grade-One Students: The Lhasa Childhood Eye Study

INTRODUCTION

The study aims to explore the prevalence of heterophoria and associate factors in Tibetan grade-one students.

METHODS

The Lhasa Childhood Eye Study (LCES) is a school-based cohort study. 1942 grade-one students from 7 elementary schools were randomly sampled by stratified cluster sampling. Ocular examinations were performed in participants, including ocular motility, distance and near visual acuity, cycloplegic autorefraction, and stereoacuity. The near (33 cm) and distance (6 m) fixation cover test was used to differentiate orthophoria, heterophoria, and heterotropia, and the magnitude of the phoria was measured by the Maddox rod and prisma.

RESULTS

Of 1856 grade-one students completing all the ocular examinations, 1852 participants finished the ocular alignment test. The mean age was 6.82 ± 0.46 years (range 6∼10 years); 981 (52.97%) were males, and 871 (47.03%) were females. The prevalence of phoria was 22.89% (n = 424). At distance fixation, the prevalence of heterophoria, exophoria, and esophoria was 4.64%, 4.21%, and 0.43% separately, while at near fixation, the prevalence was 22.73%, 22.35%, and 0.38%. No vertical phoria was detected. The mean magnitude of heterophoria at near and distance fixation was -7.63 ± 5.15 PD (exo: -7.83 ± 4.91 PD, eso: +5.67 ± 3.61 PD) and -4.84 ± 5.94 PD (exo: -6.26 ± 4.20 PD, eso: +8.13 ± 3.04 PD). The prevalence of esophoria was associated with hyperopia (OR = 6.38, 95% CI: 1.15-35.28, P = 0.03; OR = 5.42, 95% CI: 1.04-28.24, P = 0.04) and amblyopia (OR = 16.02, 95% CI: 1.81∼141.96, P = 0.01; OR = 11.37, 95% CI: 1.34∼96.52, P = 0.03) at near and distance fixation. The prevalence of exophoria was associated with myopia at near fixation (OR = 2.43, 95% CI: 1.47-4.00, P<0.01). In the near heterophoria group, the proportion of children with abnormal stereoacuity was 23.26% (n = 97), significantly higher (χ 2 = 5.70, P = 0.017) than that in orthophoria (17.99%, n = 244).

CONCLUSIONS

In Lhasa, grade-one pupils have a lower prevalence of heterophoria. Near exophoria was associated with myopia, while esophoria was related to hyperopia and amblyopia both near and distance. Heterophoria may be one of the affected factors for reducing stereoacuity.

Non-surgical Management Options of Intermittent Exotropia: A Literature Review

Purpose

To review current non-surgical management methods of intermittent exotropia (IXT) which is one of the most common types of childhood-onset exotropia.

Methods

A search strategy was developed using a combination of the words IXT, divergence excess, non-surgical management, observation, overcorrecting minus lens therapy, patch/occlusion therapy, orthoptics/binocular vision therapy, and prism therapy to identify all articles in four electronic databases (PubMed, Web of Science, Google Scholar, and Scopus). To find more articles and to ensure that the databases were thoroughly searched, the reference lists of the selected articles were also reviewed from inception to June 2018 with no restrictions and filters.

Results

IXT is treated when binocular vision is impaired, or the patient is symptomatic. There are different surgical and non-surgical management strategies. Non-surgical treatment of IXT includes patch therapy, prism therapy, orthoptic sessions, and overcorrecting minus lens therapy. The objective of these treatments is to reduce the symptoms and the frequency of manifest deviation by decreasing the angle of deviation or enhancing the ability to control it.

Conclusions

Evidence of the efficacy of non-surgical management options for IXT is not compelling. More comprehensive randomized controlled trial studies are required to evaluate the effectiveness of these procedures and detect the most effective strategy.

Difference in myopia progression between dominant and non-dominant eye in patients with intermittent exotropia

OBJECTIVE

To investigate the difference in the rate of myopia progression between the dominant and non-dominant eye in patients with intermittent exotropia (IXT).

METHODS

We retrospectively reviewed the medical records of 33 patients who underwent surgery and later reoperation for IXT. We included only patients whose spherical equivalent refractive errors (SER) were ≤ - 0.50 diopter (D) in at least one eye at the time of reoperation. The main outcome measurement was the rate of myopia progression, which was defined as the mean annual change in SER between the first and second surgery. We classified patients into two groups: group A, which comprised 25 patients whose non-dominant eyes showed a faster myopia progression than their dominant eyes, and group B, which comprised the remaining 8 patients showing the opposite.

RESULTS

Mean age of the patients at the time of the initial surgery was 5.64 years. Mean interval between the initial and second surgery was 4.45 years. Mean rate of myopia progression over the interval was - 0.37 D/year in the dominant eyes and - 0.50 D/year in the non-dominant eyes (P < 0.001). Group A had a significantly greater amount of distance deviation (31.0 vs. 25.6 PD, P = 0.020) and near deviation (30.8 vs 26.0 PD, P = 0.039) before the initial surgery and a significantly worse score of distance control (3.05 vs. 2.00, P = 0.023) before the second surgery than group B.

CONCLUSIONS

The non-dominant eyes experienced a faster myopia progression than the dominant eyes in patients with IXT. This faster myopia progression demonstrated in the non-dominant eyes was associated with clinically severe exotropia in terms of the amount of deviation and the degree of control.

Interocular difference associated with myopic progression following unilateral lateral rectus recession in early school-aged children

PURPOSE

To compare refractive changes in operated eyes and fellow unoperated eyes following unilateral lateral rectus recession in early school-aged children.

STUDY DESIGN

A retrospective case control study.

METHODS

The medical records of children under ten years of age with intermittent exotropia who underwent unilateral lateral recession surgery were reviewed. The operated eyes were reviewed and the fellow unoperated eyes were used as control. The rate of myopic progression was calculated by spherical equivalent (SE) changes per year, and by the rate of refractive growth (RRG) equation.

RESULTS

SE showed a myopic shift one week after surgery and in the following months, from -1.43 ± 1.84 diopters (D) at 1 week post operation to -1.57 ± 2.22 D at one year and, finally -2.95 ± 2.97 D at the average 4.62 years following surgery. However, the SE shift was not significantly different from the unoperated eye. The low myopia group (under -3.0 D) showed a significantly higher myopic change in the operated eye until one year post operation (p = 0.022). The average myopic shift ratio was -0.53 ± 0.46 D yearly in the operated eye.

CONCLUSIONS

This study presents data of a large series of refractive changes secondary to lateral rectus recession, and of long-term myopia progression in Korean population.

Global and regional prevalence of strabismus: a comprehensive systematic review and meta-analysis

Purpose: Despite the importance of information on the prevalence of strabismus, which can be effective in planning preventive and curative services, no study has addressed its prevalence comprehensively. In this study, a systematic search was done to estimate the regional and global prevalence of strabismus in different age and sex groups and factors affecting prevalence heterogeneity. Methods: A comprehensive and systematic search was done in different international databases, including Web of Science, Scopus, PubMed, Embase, etc. to find published articles on the total prevalence of strabismus and the prevalence of exotropia and esotropia. A binomial distribution was used to calculate the prevalence and 95% confidence interval (CI). The Cochran's Q-test and I² were applied to evaluate heterogeneity and a random-effects model was used to assess the pooled prevalence. The Begg's test was administered to investigate publication bias and finally, a meta-regression method was applied to determine the factors affecting the heterogeneity among studies. Results: Of 7980 articles, 56 articles with a total sample size of 229,396 were analyzed. Many of these articles (n = 14) were from the Regional Office for the Americas. The estimated of pooled prevalence (95% CI) of any strabismus, exotropia, and esotropia was 1.93% (1.64-2.21), 1.23% (1.00-1.46), and 0.77% (0.59-0.95), respectively. The heterogeneity in prevalence of strabismus and its subtypes according to I² was above 95% (p value <.001 for all). Age had a direct effect on heterogeneity in the prevalence of exotropia (b: 3.491; p: 0.002). Moreover, WHO region had a significant direct effect on heterogeneity in the prevalence of strabismus (b: 0.482; p < .001) and esotropia (b: 0.168; p: 0.027), and publication year had a significant direct effect on heterogeneity in the prevalence of exotropia (b: 0.059; p: 0.045). Sample size and publication year did not have any association with strabismus nor with other variables. There was no publication bias according to the Begg's test. Conclusion: The prevalence of strabismus varies widely in the world. As for factors affecting heterogeneity in the prevalence of strabismus, the results showed that age affected heterogeneity in the prevalence of exotropia, WHO region affected heterogeneity in the prevalence of strabismus and esotropia, and publication year affected heterogeneity in the prevalence of exotropia. Information about the global prevalence of strabismus can help health care planners design interventions and prioritize resource allocation.

Convergence, Accommodation, Fusion, and Stereopsis: What Keeps the Eyes Aligned in Intermittent Exotropia?

PURPOSE

To investigate the relationships between angle of deviation, fusional convergence and divergence amplitude, AC/A ratio, near point of convergence (NPC), and myopia-phoria in intermittent exotropia (IXT).

METHODS

93 patients with IXT, divided into two groups, were recruited in the study. In Group A (73 patients), fusional convergence and divergence amplitudes, NPC, and AC/A ratio were studied and compared with a control group. In Group B (in 20 patients), myopia-phoria while switching from monocular to binocular view was studied with an infrared video retinoscopy and compared with a control group.

RESULTS

In Group A, positive fusional amplitudes, NPC, and AC/A ratio of IXT patients did not differ from those of normals. Negative fusional amplitudes were significantly higher in the patient group than in the control group. In Group B, myopic shift was statistically significantly higher in the patient group and there was a statistically significant positive correlation between myopic shift and angle of strabismus.

CONCLUSIONS

Apart from the role of fusional convergence which accounts for myopia-phoria, that of the other binocular functions in the control at near of IXT and conversely their specific role in the pathogenesis of IXT remain unclear and the cause of divergent infantile strabismus is still unknown.

Clinical study of the effect of refractive status on stereopsis in children with intermittent exotropia

Background

Many studies have shown that patients with intermittent exotropia have different degrees of damage to their stereopsis function. The purpose of this study is to explore the effect of different refractive status on stereopsis in children with intermittent exotropia(IXT).

Methods

We assessed 90 children of ages 4~ 16 years with intermittent exotropia at the Second Affiliated Hospital of Dalian Medical University during the years 2016–2017. According to their refractive status, the patients were divided into hyperopia group(spherical equivalent > or = − 1.00 diopters), myopia group(spherical equivalent < or = − 1.00 diopters), emmetropia group (spherical equivalent diopter: within ±1.00DS) and anisometropia group(binocular equivalent spherical difference > or = 1.50 diopter). The distant stereopsis of the patient was checked by the synoptophore, and the near stereopsis of the patients was checked by the Titmus stereogram. Then, we compared the difference between distant stereopsis and near stereopsis in the four groups.

Results

(1)The retention rates of distant stereopsis in the hyperopia group, emmetropia group, myopia group and anisometropia group were 33.3, 45.2, 34.6, and 33.3%, respectively. There was no significant difference between the groups with different refractive status. (2)The retention rates of near stereopsis in the hyperopia group, emmetropia group, myopia group and anisometropia group were 66.7, 83.9, 80.8, and 55.6%, respectively. There were statistically significant differences between the emmetropia group and the anisometropia group (P = 0.030). (3)The retention rate of distant stereopsis in children with intermittent exotropia was 37.8%, and the retention rate of near stereopsis was 74.4%. The difference between the two groups was statistically significant (P = 0.019).

Conclusions

The damage to distant stereopsis in children with intermittent exotropia is more serious than that to near stereopsis. The damage to near stereopsis in children with intermittent exotropia and anisometropiais more serious.

Time and Factors Affecting the Direction of Re-drift in Essential Infantile Esotropia

PURPOSE

To investigate the development pattern and related factors of postoperative re-drift in infantile esotropia.

METHODS

A total of 112 patients with infantile esotropia who underwent surgery before 3 years of age were included. Surgical outcomes were divided into (1) consecutive exotropia: more than 8 prism diopters (PD) of exodeviation; (2) recurrent esotropia: more than 8 PD of esodeviation; and (3) monofixation syndrome: maintenance of deviations within 8 PD. The occurrence rate, time of onset, and associated factors of the re-drift were evaluated.

RESULTS

At a mean follow-up of 9.5 years, consecutive exotropia developed in 37 patients (33.0%) and recurrent esotropia in 43 patients (38.4%). Whereas 76.7% of total recurrent esotropia cases were identified within postoperative 1 year, consecutive exotropia occurred constantly over 10 years postoperatively. The mean time to consecutive exotropia development from surgery was 78.6 months, greater than that of recurrent esotropia development (8.9 months) (P < 0.001). In multinomial logistic regression using monofixation syndrome as the reference category, fixation preference before surgery (odds ratio [OR]: 6.64, 95% confidence interval [CI]: 2.07 to 21.32) and the rate of myopic progression (OR: 15.07 per -1.00 D/year, 95% CI: 1.23 to 184.86) were associated with consecutive exotropia, whereas increase in the angle of esodeviation on postoperative day 1 (OR: 1.15, 95% CI: 1.04 to 1.26) was correlated with recurrent esotropia.

CONCLUSIONS

This study demonstrates a difference between the development pattern of exotropic and esotropic drift after infantile esotropia surgery. Detailed preoperative assessment and close postoperative observation of deviations and refractive status will help to determine surgical outcomes of infantile esotropia. [J Pediatr Ophthalmol Strabismus. 2018;55(2):128-134.].

Health-Related Quality of Life (HRQoL) in Young Adults with Strabismus in India

INTRODUCTION

Strabismus has negative psycho-social and functional effects in adults. The impact can be minimised with surgery. However, in a low-income setting, it is important to evaluate the level of impact and prioritise the target population for intervention. The Adult Strabismus (AS-20) questionnaire is a reliable tool for assessment of Health-Related Quality of Life (HRQoL) in strabismic adults.

AIM

To assess the HRQoL in young adults with manifest strabismus through psychosocial and functional scores according to gender and direction of deviation using the AS-20 questionnaire.

MATERIALS AND METHODS

In this cross-sectional cohort study, 132 young adults who manifest horizontal strabismus were recruited and the AS-20 questionnaire was administered. Patient's demographic profile and type of strabismus were noted and compared with the overall mean scores of psycho-social and functional subscales. Data was analyzed using SPSS 21 and p-value less than 0.05 was considered statistically significant.

RESULTS

The participants comprised of 70 (53.03%) males and 62 (46.97%) females with a mean age of 24.5±3.57 years (range 18 to 38 years). The overall mean AS-20 score of young adults with strabismus was 61.62±12.61. The overall mean score for male and female were 65.54±13.53 and 57.68±13.46, respectively. Similarly, the mean scores for esotropes was 57.03±11.66 and 66.19±15.30 for exotropes. The overall mean scores were statistically significantly reduced (decreased QoL) in females as compared to males (CI 95%; p=0.002) and in esotropes as compared to exotropes (CI 95%; p=0.001). However, there was no significant difference between the psychosocial and functional score for all types of strabismus and genders (for all, p>0.05).

CONCLUSION

The Quality of Life (QoL) is affected through psychosocial and functional factors in adults with strabismus. Females and adults with esotropia faced greater difficulties in the QoL. We recommend clinicians to consider the impact on QoL while managing adult with strabismus.

Longitudinal Changes in Refractive Error in a Pediatric Referral Population in Korea

PURPOSE

To investigate changes in the spherical equivalent (SE) refractive error and astigmatism in a pediatric referral population in Korea with longitudinal follow-up and to evaluate the effect of risk factors on changes in refractive error.

METHODS

This was a retrospective case series. In total, 221 patients who presented to a tertiary care hospital when aged 3 to 9 years and who underwent at least 10 years of follow-up were enrolled. The patients were divided into groups in terms of the initial extent of SE refractive error, the initial extent of astigmatism, sex, and ocular alignment. Changes in SE and astigmatism were compared among the groups.

RESULTS

The patients were followed up for a mean of 11.19 ± 1.81 years. An overall negative shift in SE refractive error and increasing tendency in astigmatism during the follow-up period were noted. The negative shift in SE refractive error in the myopia group was significantly greater than those in the emmetropia and hyperopia groups. The change in astigmatism in the myopia group was significantly greater than that in the hyperopia group. The change in astigmatism in the low astigmatism group was significantly greater than those in the moderate and high astigmatism groups. Sex did not influence the changes in SE refractive error or astigmatism.

CONCLUSIONS

A pediatric referral population in Korea showed a negative shift in SE refractive error and increasing tendency in astigmatism during childhood. Changes in refractive error may be influenced by the initial degree of SE refractive error and astigmatism. [J Pediatr Ophthalmol Strabismus. 2017;54(1):43-51.].

Post-operative strabismus control and motor alignment for basic intermittent exotropia

AIM

To assess strabismus control and motor ocular alignment for basic exotropia surgery at 5y follow-up.

METHODS

The medical records of 80 consecutive patients aged less than 17 years of age, who underwent surgery for basic exotropia by a single surgeon between years 2000 to 2009 and completed a minimum of 5y follow-up post-operatively were reviewed. Pre- and post-operative characteristics were documented at 1wk, 6mo, 1, 3 and 5y follow-up. Subjects at 5-year follow-up were assigned to the success group if they had a post-operative angle of deviation within 10 prism diopters of exotropia or within 5 prism diopters of esotropia for distance on prism cover test, and had moderate to good strabismus control. The remaining subjects were assigned to the failure group.

RESULTS

Post-operative surgical success at one week was 75%, which decreased to 41% at 5y follow-up. The success group was noted to have more patching pre-operatively (P=0.003). The duration of patching a day (P=0.020) and total duration of patching pre-operatively (P=0.030) was higher in the success group. Surgical success at 1y (P=0.004) and 3y (P=0.002) were associated with higher surgical success at 5y follow-up.

CONCLUSION

Post-operative motor alignment and strabismus control for basic exotropia surgery at 1y and beyond is associated with higher exotropia surgery success at 5-year follow-up. There is an association between pre-operative patching and 5-year surgical success of basic intermittent exotropia surgery.

Clinical exhibition of increased accommodative loads for binocular fusion in patients with basic intermittent exotropia

BACKGROUND

To investigate the accommodative loads change needed to maintain binocular fusion in patients with intermittent exotropia (IXT).

METHODS

Seventeen consecutive patients with basic IXT and 15 normal controls were recruited. The WAM-5500 autorefractor (GrandSeiko, Fukuyama, Japan) was used to measure refractive error (D) under binocular and monocular viewing conditions at 6 m, 50 cm, 33 cm and 20 cm. The difference between binocular and monocular refractive error (D) at each distance defined the change in the accommodative load. The changes in accommodative load were compared between IXT patients and normal controls. We also investigated the change in accommodative loads according to the fixing preference in patients with IXT.

RESULTS

In IXT patients, the mean angles of deviation were 20.2 ± 7.19 and 21.0 ± 8.02 prism diopters at 6 m and 33 cm, respectively. Under binocular viewing, the changes in accommodative loads of each eye in IXT patients were significantly higher at 50, 33 and 20 cm than those of normal controls (p < 0.05, all). The changes in accommodative loads of fixating and deviating eyes at 6 m were not significantly different between IXT patients and normal controls (p = 0.193, 0.155, respectively). The changes in accommodative loads of the fixating eye at each distance were not significantly different from those of the deviating eye in IXT patients (p > 0.05).

CONCLUSION

The changes of accommodative loads at near fixation increased more in IXT patients than they did in normal controls while maintaining binocular fusion.

An external pilot study to test the feasibility of a randomised controlled trial comparing eye muscle surgery against active monitoring for childhood intermittent exotropia [X(T)]

INTRODUCTION

The evidence base for the treatment of strabismus (squint) is poor. Our main aim is to improve this evidence base for the treatment of a common type of childhood squint {intermittent exotropia, [X(T)]}. We conducted an external pilot study in order to inform the design and conduct of a future full randomised controlled trial (RCT).

METHODS

Children of between 6 months and 16 years with a recent diagnosis of X(T) were eligible for recruitment. Participants were recruited from secondary care at the ophthalmology departments at four UK NHS foundation trusts. Participants were randomised to either active monitoring or surgery. This report describes the findings of the Pilot Rehearsal Trial and Qualitative Study, and assesses the success against the objectives proposed.

RECRUITMENT AND RETENTION

The experience gained during the Pilot Rehearsal Trial demonstrates the ability to recruit and retain sites that are willing to randomise children to both trial arms, and for parents to agree to randomisation of their children to such a study. One child declined the group allocation. A total of 231 children were screened (expected 240), of whom 138 (60%) were eligible (expected 228: 95%) and 49 (35% of eligible) children were recruited (expected 144: 63% of eligible). Strategies that improved recruitment over the course of the trial are discussed, together with the reasons why fewer children were eligible for recruitment than initially anticipated. Attrition was low. Outcome data were obtained for 47 of 49 randomised children.

TRIAL PROCESSES AND DATA COLLECTION

The Trial Management processes proved effective. There were high levels of completion on all of the data collection forms. However, the feedback from the treatment orthoptists revealed that some modifications should be made to the length and frequency of the health service assessment and travel assessment questionnaires, thus reducing the burden on participants in the main trial. Modifications to the wording of the questions also need to be made.

MONITORING OF BIAS

Children who recruited to the trial were older and had more severe strabismus than those children eligible but declining participation. Strategies to account for this in a full trial are proposed.

REASONS FOR PARTICIPATION OR DECLINING STUDY

These were identified using qualitative interviews. The principal reasons for declining entry into the study were strong preferences for and against surgical treatment.

HARMS

There were no serious unexpected adverse events. Two children had overcorrection of their X(T) with reduction in binocular vision following surgery, which is in line with previous studies. No children in the active monitoring arm developed a constant strabismus although two showed some reduction in control.

CONCLUSIONS

The SamExo study has demonstrated that it is possible to recruit and retain participants to a randomised trial of surgery compared with active monitoring for X(T). For longer-term full RCTs, in order to maximise the generalisability of future studies, consideration needs to be given to planning more time and clinic appointments to assess eligibility and to allow consideration of participation; the greater use of research nurses for recruitment; and accommodating the strong preferences of some parents both for and against surgical intervention.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN44114892.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 19, No. 39. See the NIHR Journals Library website for further project information.

Management of Strabismus in Myopes

Strabismus in myopes can be related to anisometropia, accommodation/convergence effects, and/or muscle path deviations. This review article highlights management considerations in myopic patients.

Association between childhood strabismus and refractive error in Chinese preschool children

PURPOSE

To investigate the association between concomitant esotropia or concomitant exotropia and refractive error in preschool children.

METHODS

A population-based sample of 5831 children aged 3 to 6 years was selected from all kindergartens in a representative county (Yuhuatai District, Nanjing, Jiangsu Province) of Nanjing, China. Clinical examinations including ocular alignment, ocular motility, visual acuity, optometry, stereopsis screening, slit lamp examination and fundus examination were performed by trained ophthalmologists and optometrists. Odd ratios (OR) and 95% confidence intervals (95% CI) were calculated to evaluate the association of refractive error with concomitant esotropia and concomitant exotropia.

RESULTS

In multivariate logistic regression analysis, concomitant esotropia was associated independently with spherical equivalent anisometropia (OR, 3.15 for 0.50 to <1.00 diopter (D) of anisometropia, and 7.41 for > = 1.00 D of anisometropia) and hyperopia. There was a severity-dependent association of hyperopia with the development of concomitant esotropia, with ORs increasing from 9.3 for 2.00 to <3.00 D of hyperopia, to 180.82 for > = 5.00 D of hyperopia. Concomitant exotropia was associated with astigmatism (OR, 3.56 for 0.50 to 1.00 D of astigmatism, and 1.9 for <0.00 D of astigmatism), myopia (OR, 40.54 for -1.00 to <0.00 D of myopia, and 18.93 for <-1.00 D of myopia), and hyperopia (OR, 67.78 for 1.00 to <2.00 D of hyperopia, 23.13 for 2.00 to <3.00 D of hyperopia, 25.57 for 3.00 to <4.00 D of hyperopia, and 8.36 for 4.00 to <5.00 D of hyperopia).

CONCLUSIONS

This study highlights the close associations between refractive error and the prevalence of concomitant esotropia and concomitant exotropia, which should be considered when managing childhood refractive error.

Changes in refractive errors related to spectacle correction of hyperopia

Background

Hyperopic undercorrection is a common clinical practice. However, less is known of its effect on the change in refractive errors and emmetropization throughout the later years of childhood.

Objectives

To evaluate the effect of spectacle correction on the change in refractive errors in hyperopic children less than 12 years of age with or without strabismus.

Data Extraction

A retrospective cohort study was performed by a computer based search of the hospital database of patients with hyperopia, accommodative esotropia or exotropia. A total of 150 hyperopic children under 12 years of age were included. Patients were classified into four groups: 1) accommodative esotropia with full correction of hyperopia, 2) exotropia with undercorrection of hyperopia, 3) orthotropia with full correction of hyperopia, 4) orthotropia with undercorrection of hyperopia. The 4 groups were matched by initial age on examination and spherical equivalent refractive errors (SER). The main outcome measure was the change in SER (Diopter/year) in both eyes after two years of follow-up.

Results

An overall negative shift in SER was noted during the follow-up period in all groups, except for the group with esotropia and full correction. The mean negative shift of hyperopia was more rapid in groups receiving undercorrection of hyperopia with or without strabismus. The amount of undercorrection of hyperopia was positively correlated to the magnitude of decrease in hyperopia in all patients (r = 0.289, P<0.001) and in the subgroup of patients with orthotropia (r = 0.304, P = 0.011). The amount of undercorrection of hyperopia was the only factor associated with a more negative shift in SER (OR, 2.414; 95% CI, 1.202–4.849; P = 0.013).

Conclusions

The amount of undercorrection is significantly correlated to the change in hyperopic refractive errors. Full correction of hyperopia may inhibit emmetropization during early and late childhood.

Medical and surgical treatment of primary divergent strabismus

PURPOSE

To evaluate the long-term effectiveness of different therapies applied in the past 30 years, both medical and surgical, and results, with the ultimate aim of determining which are the most appropriate criteria to indicate when and how to perform medical and surgical treatment in these patients.

METHOD

A retrospective randomized study was conducted on 198 patients with primary divergent strabismus first seen in our clinic (IOC) in the last 36 years (1976-2012), with a mean follow-up of 8.38 years. Demographic and clinical characteristics, as well as the various treatments performed, and motor and sensory outcome were collected. They were finally divided into 3 groups of 70, 71 and 56 patients, respectively, according to their first visit, in order to compare the therapies applied.

RESULTS

Half (50%) of our patients debuted before 2 years of age (P50=24 months), and 26.3% had optimal binocular vision at the beginning of the study. Medical treatment was used as exclusive therapy in 29.3% of cases (occlusion therapy, applying negative lenses, botulinum toxin), and 70.7% required surgery (61.2% by double retro-insertion of lateral rectus, and 38.8% monolateral retro-resection). There was a recurrence in 26.7% of patients, and 40 re-interventions were performed (70% due to recurrence of divergent strabismus, 12.5% due to surgical over-correction, and 17.5% for other reasons). In the end, 61.1% of patients had perfect binocular vision (TNO=60"), and the proportion was higher in patients who showed proper control of their strabismus at the beginning (P=.003). However, no differences were found in the other variables studied. When the patients were divided into 3 groups (which are demographically comparable), an increased number of patients in Group 3 were found to be treated using negative lenses and botulinum toxin (P<.001 and P=.003). This group was found to have had a higher proportion of bilateral surgery (P=.032), seeking greater immediate postoperative over-correction, thus reducing the number of re-interventions from 40.5 to 19%, although it did not reach statistical significance (P=.093). It was also found that there was a significantly increased number of injections of botulinum toxin in the middle rectum for treatment of excessive postoperative overcorrection (P=.028). No other differences in final binocular vision was found between the 3 groups (P=.703).

CONCLUSIONS

In cases of clear ocular dominance, occlusion therapy must be applied twice daily on the dominating eye, in order to encourage divergent strabismus control and improve sensoriality. An attempt should be made to wait until patients reach four years of age before indicating surgical treatment, except in cases of a significant worsening of motor or sensory component. Bilateral surgery on both lateral rectus should be attempted, provided that patient characteristics allow this. A slight post-surgical overcorrection should be looked for in the immediate postoperative period, as this, in our experience, reduces the total amount of re-operations. When working on the middle rectus, remember that the elasticity of this muscle is the key factor for obtaining a proper post-surgical outcome, but a reliable measurement of this still cannot be made. In cases of excessive post-surgical over-correction, an injection of botulinum toxin should be applied to these poor elasticity muscles, in order to reduce the number of re-operations.

Impact of laser refractive surgery on ocular alignment in myopic patients

PURPOSE

To evaluate the impact of myopic keratorefractive surgery on ocular alignment.

METHODS

This prospective study included 194 eyes of 97 myopic patients undergoing laser refractive surgery. All patients received a complete ophthalmic examination with particular attention to ocular alignment before and 3 months after surgery.

RESULTS

Patients with a mean age of 26.6 years and a mean refractive error of -4.83 diopters (D) myopia were treated. Asymptomatic ocular misalignment was present preoperatively in 46 (47%) patients: a small-angle heterophoria (1-8 prism diopters, PD) in 36%; and a large-angle heterophoria (>8 PD)/heterotropia in 11%. Postoperatively, the change in angles of 10 PD or greater occurred in 3% for distance and 6% for near fixation: in 7% of the patients with orthophoria, in 3% of those with a small-angle heterophoria, and in 18% of those with a large-angle heterophoria/heterotropia. No patient developed diplopia. The preoperative magnitude of myopia or postoperative refractive status was not related to the change in ocular alignment. The higher anisometropia was associated with a decrease in deviation (P=0.041 for distance and P=0.002 for near fixation), whereas the further near point of convergence tended to be related with an increase in near deviation (P=0.055).

CONCLUSIONS

Myopic refractive surgery may cause a change in ocular alignment, especially in cases with a large-angle heterophoria/heterotropia. There is also a chance of improvement of misalignment in patients with anisometropia.

The impact of intermittent exotropia and surgery for intermittent exotropia on myopic progression among early school-aged children with myopia

AIM

To investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early school-aged children (from 7 years to 12 years of age).

METHODS

Medical records of early school-aged patients with myopia were reviewed. Patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia when 7-12 years old; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Main outcome measurements were the simple rate of myopic progression per year, the preoperative and postoperative rates of refractive growth with regards to the logarithmic age model in Group A, and the rate of high myopia development at the end of the early school period.

RESULTS

The rates of myopic progression were -0.43±0.14 dioptre (D) per year in Group A, -0.49±0.17 D/year in Group B and -0.42±0.24 D/year in Group C. There was no significant difference in the rate of myopic progression among three groups. There was no significant intergroup difference in the preoperative and postoperative rates of refractive growth in Group A. There were no significant intergroup differences in the rates of high myopia development among three groups.

CONCLUSIONS

Whether patients with intermittent exotropia underwent surgical correction for intermittent exotropia did not influence the rate of myopic progression. There was no significant difference in the rate of myopic progression between patients with accompanying intermittent exotropia and myopia and those with myopia alone.

Alcohol use and positive screening results for depression and anxiety are highly prevalent among Chinese children with strabismus

PURPOSE

To study associations between strabismus and alcohol use, anxiety, and depression among 10- to 17-year-old children in Guangdong, southern China.

DESIGN

Cross-sectional, population-based study.

METHODS

Among 7537 children aged 6-17 years from 9 randomly selected primary and middle schools, ocular alignment was assessed with the Hirschberg light reflex, cover-uncover testing, and alternate cover testing at distance (6 m) and near (40 cm). Additionally, 4000 children (53.1%) aged 10+ years received self-administered questionnaires containing screening questions on alcohol use, anxiety, and depression.

RESULTS

Examinations were completed on 7464 of 7537 subjects (99.0%), including 3928 boys (52.6%), with a mean age of 11.1 ± 1.8 years. The prevalence of any strabismus, including exotropia (2.7%), esotropia (0.2%), and intermittent exotropia (3.9%), was 6.8%. Strabismus was more prevalent in urban students (7.3%) and female subjects (7.4%) compared to rural students (6.0%) and male subjects (6.2%) (all P < .05). In multivariate regression models, any strabismus was associated with older age and rural vs urban residence. Among 3903 children (97.6%) answering questionnaires, history of alcohol use (62.3% vs 36.3%) and positive screening responses for depression (26.0% vs 11.6%) and anxiety (10.3% vs 4.9%) were significantly (P < .01 for all) more common among children with strabismus.

CONCLUSION

These Chinese children with strabismus had a significantly higher prevalence of alcohol use and possible markers of emotional problems than children without strabismus. Further research should focus on the appropriateness of classifying surgical treatment for strabismus as "cosmetic" (ineligible for reimbursement) under China's rural health insurance.

Evidence that convergence rather than accommodation controls intermittent distance exotropia

PURPOSE

This study considered whether vergence drives accommodation or accommodation drives vergence during the control of distance exotropia for near fixation. High accommodative convergence to accommodation (AC/A) ratios are often used to explain this control, but the role of convergence to drive accommodation (the CA/C relationship) is rarely considered. Atypical CA/C characteristics could equally, or better, explain common clinical findings.

METHODS

Nineteen distance exotropes, aged 4-11 years, were compared while controlling their deviation with 27 non-exotropic controls aged 5-9 years. Simultaneous vergence and accommodation responses were measured to a range of targets incorporating different combinations of blur, disparity and looming cues at four fixation distances between 2 m and 33 cm. Stimulus and response AC/A and CA/C ratios were calculated.

RESULTS

Accommodation responses for near targets (p = 0.017) and response gains (p = 0.026) were greater in the exotropes than in the controls. Despite higher clinical stimulus AC/A ratios, the distance exotropes showed lower laboratory response AC/A ratios (p = 0.02), but significantly higher CA/C ratios (p = 0.02). All the exotropes, whether the angle changed most with lenses ('controlled by accommodation') or on occlusion ('controlled by fusion'), used binocular disparity not blur as their main cue to target distance.

CONCLUSIONS

Increased vergence demand to control intermittent distance exotropia for near also drives significantly more accommodation. Minus lens therapy is more likely to act by correcting overaccommodation driven by controlling convergence, rather than by inducing blur-driven vergence. The use of convergence as a major drive to accommodation explains many clinical characteristics of distance exotropia, including apparently high near stimulus AC/A ratios.