Grading the severity of intermittent distance exotropia: the revised Newcastle Control Score

Evaluation of Structural and Functional Retinal Changes in Children With Intermittent Exotropia Versus Healthy Children

PURPOSE

To detect structural and functional changes in children with intermittent exotropia using optical coherence tomography, pattern electroretinography (ERG), and multifocal ERG.

METHODS

The study included 26 patients with intermittent exotropia and 26 healthy individuals matched for age and sex with a mean age of 9.23 and 11.20 years in the intermittent exotropia and control groups, respectively (P = .310). All patients underwent full ophthalmic examination including measurement of the angle of strabismus at near and far, and assessment of the macula and optic nerve using optical coherence tomography, pattern ERG, and multifocal ERG.

RESULTS

All patients had 6/6 best corrected visual acuity with no fixation preference. A significantly prolonged P and N wave latency was found in all measured rings of multifocal ERG of patients with intermittent exotropia, P wave amplitude was lower in rings 1 and 5, and N wave amplitude was lower in rings 1 and 2. Regarding pattern ERG, the amplitude of P50 wave was lower and N95 latency was prolonged in the intermittent exotropia group. The upper and lower ganglion cell complex and the superior retinal nerve fiber layer were significantly thinner in the intermittent exotropia group compared to controls.

CONCLUSIONS

Children with intermittent exotropia without any associated amblyopia or refractive error showed a subnormal pattern and multifocal ERG response in addition to a thinner ganglion cell layer and retinal nerve fiber layer compared to normal controls. This signifies that subtle structural and functional retinal changes are found in patients with intermittent exotropia. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XXX-XXX.].

Office-based vergence and anti-suppression therapy for the treatment of small-to-moderate angle intermittent exotropia: A randomised clinical trial

PURPOSE

To evaluate the short-term (1 week after completion of treatment) effect of office-based vergence and anti-suppression therapy (OBVAT) on the Office Control Score when compared to observation alone in children with small-to-moderate angle intermittent exotropia (IXT).

METHODS

In this single-masked (examiner masked), two-arm, single-centre randomised clinical trial, 40 participants, 6 to <18 years of age with untreated IXT, were randomly assigned to OBVAT or observation alone. Participants assigned to therapy received 60 min of OBVAT with home reinforcement once per week for 16 weeks. Therapy included vergence, accommodation and anti-suppression techniques. The primary outcome measure was the comparison of the distance Office Control Score between the two groups at the primary outcome visit (i.e., 17-week follow-up visit).

RESULTS

At the primary outcome visit, the OBVAT group (n = 20) had a significantly better distance Office Control Score (adjusted mean difference: -0.9; 95% CI: -0.2 to -1.5; p = 0.008; partial eta squared: 0.19) than the observation group (n = 16). Participants from the OBVAT group were more likely than those from the observation group to have ≥1 point of improvement at the 17-week visit (OBVAT group: 75%; Observation group: 25%; p = 0.006).

CONCLUSIONS

In this randomised clinical trial of participants aged 6 to <18 years with IXT, we found that the OBVAT group had a significantly better distance Office Control Score than the observation group at the 17-week visit. This study provides the first data from a randomised clinical trial demonstrating the effectiveness of OBVAT for improving the control of IXT. Eye care practitioners should consider OBVAT as a viable, non-surgical treatment option for IXT. A full-scale randomised clinical trial investigating the long-term effectiveness of OBVAT in treating IXT is warranted.

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.

Divergence excess and basic exotropia types of intermittent exotropia: a major review. Part 1: prevalence, classification, risk factors, natural history and clinical characteristics

INTRODUCTION

Intermittent exotropia (IXT) is a common form of strabismus. It is an outward deviation of one eye typically when viewing at distance. Symptoms include, but are not limited to double vision, eyes feeling tired, excessive blinking, and reduced quality of life. Its clinical characteristics are distinctive from other types of strabismus. This paper provides a comprehensive review of prevalence, classification, risk factors, natural history and clinical characteristics of the divergence excess and basic exotropia types of IXT.

METHODS

Search strategies involving combination of keywords including intermittent exotropia, exotropia, divergences excess, basic exotropia, prevalence, incidence, classification, terminology, risk factor, natural history, observation, angle of deviation, control, control score, symptom, quality of life, suppression, anomalous retinal correspondence, AC/A, accommodative convergence/accommodation, accommodative convergence, convergence, accommodation, vergence, incomitance and vertical were used in Medline. All English articles from 1900/01/01 to 2020/09/01 were reviewed. The reference list of the identified article was also checked for additional relevant article. Studies focused on animal model or strabismus associated with neurologic disorder or injury were excluded.

RESULTS

The estimated prevalence of IXT in children ranges from 0.1% to 3.7%. Hypoxia at birth and being female are potential risk factors of IXT. Using validated measures of control, multicenter prospective studies showed that the rate of conversion from IXT to constant exotropia is low. The angle of deviation is the most reported outcome measure in studies of IXT. It is often used to represent the severity of the condition and has been suggested as one of the four core outcomes for studies of the surgical management of IXT. Control of exodeviation is one of the four suggested core outcomes for study of surgery of IXT and is considered the main parameter of disease severity. Several validated tools for quality of life score are available to evaluate the subjective severity of IXT.

DISCUSSION

We reviewed the prevalence, classification, risk factors, natural history and clinical characteristics of the divergence excess and basic exotropia types of IXT. Further research into these areas, especially its clinical characteristics (e.g. suppression, dual retinal correspondence), will increase our understanding of this condition and potentially lead to better management of this common form of strabismus.

Ambulatory Monitoring With Eye Tracking Glasses to Assess the Severity of Intermittent Exotropia

PURPOSE

To explore the utility of eye tracking glasses in patients with intermittent exotropia as a means for quantifying the occurrence of exotropia, defined as the percentage of time that the eyes are misaligned.

DESIGN

Prospective observational study.

METHODS

Eye tracking glasses were used to obtain 68 recordings in 44 ambulatory patients with a history of intermittent exotropia. Vergence angle was monitored for up to 12 hours to document the occurrence of exotropia.

RESULTS

Intermittent exotropia was present in 31 of 44 patients. They had a mean exotropia of 19.3 ± 5.3° and a mean occurrence of 40% (range 3-99%). There was a moderate correlation between the magnitude of exotropia and its occurrence (r = 0.59). In 13 patients the occurrence of exotropia was <1%; they were deemed to have an exophoria only. In 35 of 44 cases, families reported an occurrence of intermittent exotropia greater than that measured by the eye tracking glasses.

CONCLUSIONS

Eye tracking glasses may be a useful tool for quantifying the severity of intermittent exotropia and for defining more precisely its clinical features.

Automated Detection of Horizontal Strabismus and Home Control Evaluation Using a Mobile Phone App

Purpose: To evaluate the reliability, validity, and usability of a mobile phone app that captures facial images to identify strabismus.Methods: We enrolled patients who visited our pediatric strabismus clinic and provided consent for participation in the study. The facial photographs of the patients were automatically captured by the app. The app used the photographs to identify ocular misalignment based on the comparison of the positions of the corneal reflex and limbus of both eyes. The results from the app were compared to the physician’s diagnosis. Intraclass correlation coefficients were used to assess the test-retest and interrater reliability of the app. Additionally, the guardians captured photographs of the patients through this app for 1 month at home to evaluate the frequency of manifest exotropia at home. And the results were compared to those of other strabismus control scales.Results: A total of 103 patients were enrolled and 10 patients were enrolled for the home control test. Based on the physician’s diagnosis, the sensitivity, specificity, positive predictive value, and negative predictive value of the app were 74.6%, 87.5%, 90.4%, and 68.6%, respectively. The interclass correlation coefficients for inter-rater and test-retest reliability were 0.801 (<i>p</i> = 0.011) and 0.828 (<i>p</i> < 0.001), respectively. The frequency of intermittent exotropia recorded by the app at home showed a strong positive correlation with other control scales (rho > 0.770, <i>p</i> = 0.009).Conclusions: This mobile phone app is easily accessible and useful for the rapid determination and recording of strabismus, particularly in uncooperative patients. Also, this app may be used as a reliable indicator of the frequency of manifest strabismus at home.

Cortical Deficits are Correlated with Impaired Stereopsis in Patients with Strabismus

In this study, we explored the neural mechanism underlying impaired stereopsis and possible functional plasticity after strabismus surgery. We enrolled 18 stereo-deficient patients with intermittent exotropia before and after surgery, along with 18 healthy controls. Functional magnetic resonance imaging data were collected when participants viewed three-dimensional stimuli. Compared with controls, preoperative patients showed hypoactivation in higher-level dorsal (visual and parietal) areas and ventral visual areas. Pre- and postoperative activation did not significantly differ in patients overall; patients with improved stereopsis showed stronger postoperative activation than preoperative activation in the right V3A and left intraparietal sulcus. Worse stereopsis and fusional control were correlated with preoperative hypoactivation, suggesting that cortical deficits along the two streams might reflect impaired stereopsis in intermittent exotropia. The correlation between improved stereopsis and activation in the right V3A after surgery indicates that functional plasticity may underlie the improvement of stereopsis. Thus, additional postoperative strategies are needed to promote functional plasticity and enhance the recovery of stereopsis.

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.

Cataract surgery is not associated with post-operative binocular vision anomalies in age-related cataract patients

PURPOSE

To compare the binocular vision status of patients pre- and post-cataract surgery, and to investigate the risk factors for patients who develop binocular vision anomalies post-surgery.

METHODS

A prospective study of patients (≥50 years) who elected to undergo bilateral cataract surgery was implemented. A comprehensive binocular vision test battery including stereopsis, ocular alignment, fusional vergence, vergence facility, near point of convergence and the Convergence Insufficiency Symptom Survey (CISS) was administered before the first surgery and at the third visit after surgery on the second eye. A detailed diagnostic classification protocol was applied to identify the presence of binocular vision anomalies pre- and post-surgery.

RESULTS

Seventy-three participants were included at baseline, 24 (33%) of whom were diagnosed with non-strabismic binocular vision anomalies (NSBVA), mainly convergence insufficiency (18/73, 25%). Fifty-one participants completed the post-operative evaluation, 17 (33%) of whom had NSBVA pre-surgery and 13 (26%) post-surgery (p = 0.48). There were a number of conversions from NSBVA to normal binocular vision and vice versa. Logistic regression showed that the adjusted odds ratio of pre-existing NSBVA diagnosis for predicting the risk of post-operative NSBVA was 6.37 (p < 0.01). There were no significant changes in most binocular vision measures post-surgery, except for a significant improvement in the CISS score (p < 0.01, Cohen's d = 0.83).

CONCLUSIONS

Binocular vision anomalies, especially convergence insufficiency, are prevalent in the age-related cataract population. Cataract surgery does not appear to be a significant risk factor for the development of new binocular vision anomalies. A pre-existing binocular vision anomaly is the main risk factor for predicting a post-operative binocular vision anomaly in this population.

Functional changes in the visual cortex in preoperative and postoperative patients with intermittent exotropia: study protocol for a non-randomised case-control clinical trial

INTRODUCTION

Intermittent exotropia (IXT) is the most common type of divergent squint. IXT is primarily a cortical neurologic dysfunction disorder, occurring as a result of the insufficient maintenance of sensory and motor fusion. Recent reports have demonstrated the relationship between IXT and visual cortical impairment. We planned to assess blood oxygen level-dependent (BOLD)-functional magnetic resonance imaging (fMRI) in patients with IXT during the preoperative and postoperative follow-ups to evaluate the functional changes in the visual cortex.

METHODS AND ANALYSIS

A total of 90 Chinese subjects will be recruited, and their ages will be between 18 and 40 years old. The subjects will include the surgical treatment (ST) group (45 subjects with IXT who will undergo surgery) and the HC group (45 age-matched, sex-matched and education-matched healthy volunteers). The assessments will include the following aspects: fMRI and general ophthalmic examinations, optometry measurements and strabismus-related tests, such as the ocular deviation, binocular vision test and Newcastle Control Score (NCS). Each subject will complete the resting-state BOLD-fMRI, and the sequences will include echo planar imaging (EPI) pulse and 3-dimensional brain volume (3D-BRAVO) to acquire high-resolution images. The follow-up schedule will be 6 and 12 months after the surgery. The primary outcome will be determined by cortex changes in BOLD-fMRI in the ST group before and after surgery. We will also compare the HC group with the preoperative subjects in the ST group. The secondary outcomes will be changes in strabismus-related examinations, such as binocular visual function and NCS.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Medical Ethics Committee of Beijing Tongren Hospital. We plan to publish the results of this study in a peer-reviewed journal article.

TRIAL REGISTRATION NUMBER

ChiCTR2100048852.

Clinical Usefulness of a Computerized Vision Chart for Distance Stereoacuity Assessment in Children with Intermittent Exotropia

INTRODUCTION

The aim of this study is to evaluate distance stereoacuity in children with intermittent exotropia (IXT) using a computerized vision chart (CVC), to compare the results to the normal subjects, and to determine if any correlation between stereoacuity and IXT severity exits.

METHODS

A prospective case-control study was conducted including 24 children with IXT and 25 age-matched normal subjects. The mean age was 8.9 ± 4.5 in IXT group and 9.4 ± 4.2 in control group. The majority of patients (n = 17) had basic type IXT. Full ophthalmic examinations, deviations and stereoacuity tests were evaluated. Stereoacuity was measured with the CVC for distance stereoacuity and Randot stereotest book for near stereoacuity. Level of fusional control in patients with IXT was assessed using Newcastle Control Score (NCS). Seven of the patients with IXT were also reevaluated postoperatively.

RESULTS

Near stereoacuity was good in both IXT and control groups, and there was no significant difference between groups. There was a poor correlation between near stereoacuity and NCS (r_s = 0.15, p = .48). Distance stereoacuity in the IXT group was significantly reduced compared to controls (p = .004). There was a positive correlation between distance stereoacuity values and NCS in patients with IXT (r_s = 0.73, p < .001).

CONCLUSION

Diminished distance stereoacuity in children with IXT can be detected with the CVC and this test may be useful for deciding the timing of surgical intervention and postoperative evaluation.

Bilateral Occlusion Reduces the Ocular Deviation in Intermittent Exotropia

Purpose

The most common form of strabismus, intermittent exotropia, is thought to become manifest when the drive to fuse is overcome by excessive divergent muscle tone. This principle is tested by examining the alignment of the eyes in the absence of vision. We compare the ocular deviation in patients with intermittent exotropia under conditions of monocular versus binocular occlusion.

Methods

This prospective study of a patient cohort referred to our laboratory enrolled 18 patients with typical findings of well-controlled intermittent exotropia. Eye positions were recorded with video eye trackers while patients looked at a fixation spot at a distance of 57 cm. One eye was occluded, and the resulting ocular deviation was measured. Both eyes were then occluded, and the ocular deviation was re-measured.

Results

The majority of patients (11/18) had a smaller deviation when both eyes were covered. Occlusion of one eye resulted in a mean exotropia of 13.5° ± 4.7°. Occlusion of both eyes reduced the mean exotropia to 6.0° ± 6.5° (paired t-test, P < 0.001), corresponding to a 56% reduction in the ocular deviation. This reduction persisted during prolonged bilateral occlusion but reversed as soon as vision was restored.

Conclusions

Bilateral occlusion reveals a fixation-free state of alignment that is different from orthotropia and usually less than the exotropia that occurs spontaneously during binocular viewing. This finding demonstrates that the deviation angle in patients with intermittent exotropia is actively mediated by visual feedback, which the fixating eye is capable of providing alone.

Disrupted neural signals in patients with concomitant exotropia

PURPOSE

Decreased binocular and oculomotor function in strabismics has recently been considered as cortical in origin. This study aimed to investigate functional abnormalities using a frequency-specific neuroimaging method in patients with concomitant exotropia (XT), and to demonstrate the clinical implications.

METHODS

Resting-state functional magnetic resonance imaging data were collected in 26 XT patients and 26 matched controls. To evaluate the local spontaneous neural activity, the amplitude of low frequency fluctuations (ALFF) was calculated in the typical frequency band (0.01-0.08 Hz) as well as five narrowly-defined frequency bands (slow-6: 0-0.01 Hz, slow-5: 0.01-0.027 Hz, slow-4: 0.027-0.073 Hz, slow-3: 0.073-0.167 Hz, and slow-2: 0.167-0.25 Hz), respectively.

RESULTS

Patients with XT showed decreased ALFF in the bilateral parieto-occipital sulcus (POS), and increased ALFF in the bilateral thalamus within the typical frequency band. Frequency-dependent ALFF alterations were found in the higher visual areas such as the right lateral occipital complex (LOC). Furthermore, ALFF in the right LOC in the slow-5 band was positively correlated with fusion control score (r = 0.70, p < 0.0001) and binocular function score (r = 0.67, p = 0.0002). Regression analyses showed that early age of onset remained the only significant explanatory factor for ALFF reduction in the right POS in the typically-measured frequency band (also referred to as the typical frequency band) (Odds ratio, 0.038; 95% confidence interval, 0.001 to 0.075).

CONCLUSIONS

Our findings provide spatial information regarding the functionally disrupted regions in XT. Moreover, the frequency-dependent ALLF alteration in the right LOC might reflect a potential plastic capacity in binocular function, which could be a potential objective index for evaluating disease severity.

LACTOSE control scoring helps predict surgical outcomes for childhood intermittent exotropia

OBJECTIVE

To determine whether preoperative Look And Cover, then Ten seconds of Observation Scale for Exotropia (LACTOSE) control scores can predict surgical outcomes in children with intermittent exotropia.

DESIGN

Retrospective interventional case series from a university-based tertiary eye care centre.

PARTICIPANTS

A total of 350 patients with basic-type intermittent exotropia who underwent bilateral lateral rectus recession between 3 and 10 years of age from January 2014 to December 2017.

METHODS

All patients were preoperatively assessed for their degree of control at both distance and near according to LACTOSE scoring system. Demographic, clinical, and oculomotor data before and after surgery were collected and analyzed with regard to the degree of control. Surgical success was defined as an alignment between 10 prism diopters (PD) of exodeviation and 5 PD of esodeviation at both distance and near.

RESULTS

Younger age, lower visual acuity, worse stereoacuity, and larger angle of deviation were associated with higher (i.e., worse) LACTOSE control scores. Of the 350 patients having surgery, 169 (48.3%) were followed for more than 12 months postoperatively. Surgical success was achieved in 132 (78.1%) patients at 12 months after surgery. The only significant predictor of surgical success was preoperative LACTOSE score. There was a significant inverse relationship between LACTOSE scores and surgical success rates for both distance and near scores (p = 0.004 and 0.023, respectively).

CONCLUSIONS

Higher distance and near LACTOSE scores representing worse control of deviation were associated with higher rates of surgical failure in children with intermittent exotropia. This finding indicates that surgical outcome of intermittent exotropia can be predicted by preoperative LACTOSE scores.

Health-related quality of life correlated with the clinical severity of intermittent exotropia in children

OBJECT

To evaluate whether the results of the health-related quality of life (HRQOL) is associated with the various clinical aspects of intermittent exotropia in children.

METHODS

The HRQOL of children and their parents was evaluated prospectively using the Intermittent Exotropia Questionnaire (IXTQ). The deviation angle, stereo function, sensory fusion, and strabismus control were measured.

RESULTS

Two hundred and sixty six children with intermittent exotropia (aged 5-17 years) were included in the study. Child HRQOL was significantly correlated with clinical severity; lower IXTQ scores were associated with a larger deviation (p < 0.001 both for distance and near) and poorer Newcastle control scores (p < 0.001). Proxy child HRQOL was significantly correlated with the deviation (p < 0.001), Newcastle control scores (p < 0.001) and stereo function (p < 0.05). Parent HRQOL was associated with their child's deviation (p < 0.01) and stereo function (p < 0.005). Multiple linear regression analysis suggested that the deviation angle at distance and the Newcastle control score at home were associated with the child's HRQOL.

CONCLUSION

Both the child and their parents' HRQOL showed a trend toward correlating with clinical severity. Large deviation, poor control, and poor stereo function were significantly associated with lower IXTQ scores. The deviation angle at distance and exotropia control at home were associated with the child's HRQOL.

[Intermittent exotropia]

Intermittent exotropia (IXT) is the most common type of divergent strabismus. It is the consequence of passive mechanisms due to the anatomy of the globes and orbits or due to active innervational mechanisms, resulting in divergence of the visual axes, which is compensated by fusional convergence. Intermittent insufficiency in this compensation gives this form of exotropia its intermittent nature. The most common symptoms of IXT are closure of one eye, asthenopia and diplopia, but they are often absent. The clinical classification of IXT (according to Burian) is based on the difference between the distant and the near angles of deviation. It defines 4 types: true divergence excess (at distance), pseudo-divergence excess, the basic form (distance and near angles are equal) and convergence insufficiency (near angle greater than distance angle). One of the main difficulties in examination of IXT is neutralizing the fusional convergence in order to classify the strabismus. For this purpose, the monocular occlusion test, a near addition, or a prism adaptation test can be used. IXT is also characterised by the quality of control of the deviation by the patient, which is taken in account for therapeutic decision. Tools for measurement of this control have recently been developed and are not commonly used. The natural history of IXT is not well understood. Treatment relies mainly on optical correction, binocular visual training therapy and surgery, but their indications are not well defined, nor are outcomes analysis criteria. In the case of surgery, it aims to treat the maximum measured distance angle; the medium- and long-term angular results of surgery are often disappointing, although it probably improves control of the strabismus in most cases.

Three-Year Observation of Children 3 to 10 Years of Age with Untreated Intermittent Exotropia

PURPOSE

To describe the course of intermittent exotropia (IXT) in children followed up without treatment for 3 years.

DESIGN

Observation arm from randomized trial of short-term occlusion versus observation.

PARTICIPANTS

One hundred eighty-three children 3 to 10 years of age with previously untreated IXT and 400 seconds of arc (arcsec) or better near stereoacuity.

METHODS

Participants were to receive no treatment unless deterioration criteria were met at a follow-up visit occurring at 3 months, 6 months, or 6-month intervals thereafter for 3 years.

MAIN OUTCOME MEASURES

The primary outcome was deterioration by 3 years, defined as meeting motor criterion (constant exotropia ≥10 prism diopters [Δ] at distance and near) or near stereoacuity criterion (≥2-octave decrease from best previous measure). For the primary analysis, participants also were considered to have deteriorated if treatment was prescribed without meeting either deterioration criterion.

RESULTS

The cumulative probability of protocol-specified deterioration by 3 years was 15% (95% confidence interval, 10%-22%), but that was likely an overestimate, partly because of misclassification. Among 25 deteriorations, 2 met motor deterioration, 11 met stereoacuity deterioration, and 12 started treatment without meeting either criteria (7 for social concern, 1 for diplopia, 4 for other reasons). Among the 132 participants who completed the 3-year visit and had not been treated during the study, only 1 (<1%) met motor or stereoacuity deterioration criteria at 3 years. Of the 4 participants completing the 3-year visit who met deterioration criteria previously and had not started treatment, none still met deterioration criteria. Between the baseline and 3-year examination for these 132 patients, improvement occurred in distance and near stereoacuity (mean improvement, 0.14 and 0.14 logarithm of arcsec; P ≤ 0.001 and P ≤ 0.001, respectively), distance exotropia control (mean improvement, 0.6 points; P ≤ 0.001), and distance exodeviation magnitude (mean improvement, 2.2 Δ; P = 0.002).

CONCLUSIONS

Among children 3 to 10 years of age with IXT for whom surgery was not considered to be the immediately necessary treatment, stereoacuity deterioration or progression to constant exotropia over 3 years was uncommon, and exotropia control, stereoacuity, and magnitude of deviation remained stable or improved slightly.

Far distance control scores for assessing intermittent exotropia

PURPOSE

To assess the level of control in intermittent exotropia by applying the office-based 6-point control scale to far-distance testing.

METHODS

Fifty-two children with intermittent exotropia were enrolled in this prospective, noninterventional case series. Control of exodeviation was assessed at indoor distance (ID) of 3 m and near distance of 33 cm using the office-based 6-point control scale, which was additionally applied to indoor far distance (IFD) fixation of 30 m and outdoor far distance (OFD) fixation of 50 m.

RESULTS

In all 52 patients, the level of control at OFD fixation was either worse than (31%) or the same as (70%) the level of control at IFD fixation and the level of control at IFD fixation was worse than (64%) or the same as (35%) the level of control at ID fixation. The level of control at OFD fixation was worse than (69%) or the same as (31%) the level of control at ID fixation for all 52 patients. The differences between mean control scores of OFD and IFD fixation (P = 0.002), IFD and ID fixation (P < 0.001), OFD and ID fixation (P < 0.001) were statistically significant.

CONCLUSIONS

The outdoor and indoor far distance control scores can increase the sensitivity of the office-based 6-point control scale. The office control scale for assessing control in patients with intermittent exotropia could have application for the management of intermittent exotropia.

Patient Characteristics and Surgical Approach Impacting Simultaneous to Alternate Prism Cover Test Disparity After Exotropia Surgery: A Quantitative Look at the Difference in Motor Outcomes

PURPOSE

To investigate the relationship between simultaneous prism and cover test (SPCT) and alternate prism and cover test (APCT) outcomes after exotropia surgery, and to identify characteristics associated with significant disparity between them.

METHODS

Review of sensorimotor outcomes 2 to 6 months after exotropia surgery identified patients with alignment documented by both SPCT and APCT at the same examination. Two hundred seventy-four and 319 patients had both measurements recorded at distance and near, respectively. Correlation between the SPCT and APCT and range of APCT when the SPCT measurement was zero were determined. Patient characteristics studied for association with a difference between the SPCT and APCT exceeding known APCT test-retest variability included age, visual acuity, fusion, intermittency, pattern, preoperative and postoperative angle, and treatment with or without medial rectus resection.

RESULTS

SPCT and APCT outcomes were strongly correlated (P < .001), significantly different (P < .001), and linearly related. The percentage of patients who were orthotropic (SPCT = 0) was 76% at distance and 80% at near. Misalignment of 10 prism diopters (PD) or less by the APCT was present in 92% of orthotropic patients at distance and 84% at near. Surgery without medial rectus resection (P = .015), larger preoperative angle (P = .003), intermittent exotropia (P = .028), and postoperative exotropia rather than esotropia (P < .001) were associated with a significant SPCT-APCT difference.

CONCLUSIONS

Although a greater postoperative SPCT-APCT disparity was confirmed for patients with intermittent exotropia, it also independently associated with a larger preoperative deviation and surgery without medial rectus resection. Performing medial rectus resection, a surgeon's prerogative, provides more apparently consistent postoperative alignment characterized by less SPCT-APCT disparity. [J Pediatr Ophthalmol Strabismus. 2017;54(4):222-230.].

The Effect of Preoperative Occlusion Therapy on Long-term Outcome after Surgery for Early-onset Exotropia

PURPOSE

To investigate the effect of preoperative part-time occlusion therapy on long-term surgical success in early-onset exotropia.

METHODS

The medical records of patients who underwent surgery for exotropia with onset before the first year of age and who were followed for ≥3 years were reviewed. Patients were divided into two groups according to the degree of compliance with part-time occlusion therapy: the good compliance group (>50% adherence rate) and the poor compliance group (≤50% adherence rate). Surgical success was defined as orthophoria to exodeviation less than 10 prism diopters both at distance and near. The level of postoperative stereopsis was compared between the two study groups among total enrolled patients and among those with constant exotropia.

RESULTS

Of the 51 patients, 26 were assigned to the good compliance group and the remaining 25 patients to the poor compliance group. The surgical success rate was significantly higher in the good compliance group than in the poor compliance group (80.8% vs. 52.0%, p = 0.040). Among 24 constant exotropia patients (12 patients for each group), the success rate was insignificantly higher in the good compliance group than in the poor compliance group (75.0% vs. 58.3%, p = 0.448). The good compliance group had a better level of stereopsis than the poor compliance group (p = 0.045 for all 44 patients, p = 0.020 for 19 patients with constant exotropia).

CONCLUSIONS

Preoperative part-time occlusion therapy was useful for improving the surgical outcome of early-onset exotropia and postoperative stereopsis.

Binocular Summation and Control of Intermittent Exotropia

BACKGROUND

Binocular summation (BiS), or improvement in binocular vision exceeding the better eye alone, is affected by strabismus. Being easily measured, BiS may be a useful indicator for subjective outcomes like stereopsis in strabismus. This study aims to investigate the relationship between BiS and measures of control of intermittent exotropia (IXT).

METHODS

Patients with IXT were recruited before undergoing strabismus surgery and underwent tests of binocular and monocular high- and low-contrast visual acuity, stereopsis at distance and near, and Newcastle Control Score (NCS), a score developed by incorporating home control and clinic control criteria into a control rating scale. BiS was calculated using high-contrast Early Treatment of Diabetic Retinopathy Study (ETDRS) and Sloan low-contrast acuity charts (LCA) at 2.5% and 1.25% contrast as the difference between the binocular score and that of the better eye. The relationship between BiS and measures of IXT control (NCS and distance near stereoacuity disparity) was evaluated using a correlation analysis by Spearman correlation coefficients and the Kruskal-Wallis test.

RESULTS

Thirty-four patients were included (mean [± standard deviation (SD)] age 19±16 years) having a mean (±SD) of 26±16Δ IXT at distance and 20±16Δ at near. Mean (±SD) BiS for ETDRS and Sloan LCA at 2.5% and 1.25% was 0.8±3.6, 1.9±6.0, and -2.3±7.2, respectively. The Spearman correlation coefficient of BiS and NCS was -0.53 (95% CI -0.85 to -0.25) for 2.5% LCA and -0.43 (95% CI -0.77 to -0.13) for 1.25% LCA. BiS at 2.5% LCA (P=0.006) and at 1.25% LCA (P=0.029) significantly differed between the groups based on NCS score groupings (1-3, 4-6, and 7-9), with patients who had better control scores having higher levels of BiS. BiS did not differ significantly between patients grouped according to the difference between stereoacuity measured at near versus distance.

CONCLUSION

Significantly lower low-contrast BiS in patients with higher NCS may suggest that decreased BiS is associated with less control in IXT. This finding suggests that BiS may reflect control in IXT across a population of patients with IXT.

Proposing a new scoring system in intermittent exotropia: towards a better assessment of control

OBJECTIVE

There is a clinical need for a valid and reliable assessment system to quantify the severity and measure the progression of intermittent exotropia. We have developed a new scoring system (Look And Cover, then Ten seconds of Observation Scale for Exotropia [LACTOSE]) based on the examinee's potential to regain the phoria for both distance and near fixation. The test takes only 1 minute to complete. The aim of this study was to evaluate the reliability and validity of LACTOSE.

METHODS

The LACTOSE was created by incorporating both distance and near score (0-4 each) into a total score ranging from 0 to 8. A total of 235 consecutive patients with intermittent exotropia were prospectively evaluated using this new scoring system. Inter-rater and test-retest reliability was assessed from a cohort of 10 patients who were video recorded while undergoing the scoring testing and then scored by 10 trained ophthalmologists independently. Construct validity was studied by comparison with clinical variables indicating disease severity.

RESULTS

Inter-rater reliability was good for both distance and near (intraclass correlation coefficient [ICC] = 0.729 and 0.818). Test-retest reliability was excellent for both distance and near (ICC = 0.849 and 0.727). Median scores for distance, near, and total were 3, 1, and 4, respectively. A broad representation of the total scores was significantly linked to the age of onset and the amount of exotropia (r² = 0.194, p = 0.003 and r² = 0.159, p < 0.001).

CONCLUSIONS

We found that our newly developed scoring system is a reliable and valid tool for assessing the severity of intermittent exotropia. This new measure can be implemented easily and efficiently across diverse clinical settings.

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.

Distance stereotesting using vision test charts for intermittent exotropia

Purpose

To assess the role of distance stereoacuity using the System Chart SC-1600 Pola (SC) to evaluate intermittent exotropia (IXT).

Methods

Stereoacuity testing was performed in 28 children with IXT and 25 age-matched control subjects using the SC test, the distance Randot stereotest for distance, and the Titmus stereotest for near stereoacuity. Ocular alignment control was defined using the revised Newcastle Control Score (NCS). The correlations between the stereotests and NCS were evaluated using Spearman’s correlation test.

Results

Distance stereoacuity was better in both groups when using the SC test than when using the distance Randot stereotest (median: patients with IXT, 90 arcsec and 400 arcsec; control, 60 arcsec and 100 arcsec; P<0.001 for both comparisons). The two test scores were not correlated in either group (IXT: r_s=−0.003, P=0.99; control: r_s=0.37, P=0.07). A positive correlation was found between the distance NCS and SC test scores (r_s=0.49, P=0.004) and the total NCS and SC test scores (r_s=0.49, P=0.004). However, no correlation was observed between any NCS and the distance Randot stereotest or Titmus stereotest scores.

Conclusion

Stereoacuity, as measured by the SC test, may be an objective measure of IXT control.

Goal-determined metrics to assess outcomes of exotropia surgery

PURPOSE

To present a goal-determined methodology for monitoring outcomes after surgery for exotropia.

METHODS

The goal-determined metric required surgeons to rank four possible goals preoperatively: (1) binocular potential, (2) restoration of eye contact, (3) diplopia control; and (4) torticollis management. Potential preoperative risk factors were noted. Goal-specific outcomes criteria were applied to the latest sensory-motor examination, 2-6 months after surgery. The medical records of patients who underwent surgery from 2007 to 2012 were retrospectively reviewed with respect to the goal-directed metric.

RESULTS

A total of 852 patients were evaluated in the study period: 411 for restoration of eye contact; 347 for binocular potential; 78 for diplopia resolution; and16 for torticollis management. Excellent (62%) or good (16%) outcomes were achieved in 78%. Procedures to resolve diplopia (OR, 6.56; 95% CI, 3.39-12.68) and to restore eye contact (OR, 3.74; 95% CI, 2.65-5.29) were more likely to result in excellent outcomes than procedures to improve binocular potential. Simultaneous surgery for dissociated vertical deviation (OR, 0.38; 95% CI, 0.16-0.92) and preoperative near deviation ≥50(Δ) (OR, 0.27; 95% CI, 0.17-0.42) limited likelihood of an excellent outcome. Outcomes monitored by simultaneous rather than alternate prism and cover test were more likely graded excellent (OR, 5.16; 95% CI, 3.50-7.62). Applying motor criteria from the binocular potential goal to the entire cohort diminished putative outcomes (P < 0.001).

CONCLUSIONS

Goal-determined metric monitoring outcomes of exotropia surgery provides outcomes germane to the reason for intervention, enables analysis of risk factors affecting outcomes, and facilitates reporting on heterogeneous populations.

Fusional vergence detected by prism bar and synoptophore in chinese childhood intermittent exotropia

Purpose. To measure the changes in fusional vergence in Chinese children with intermittent exotropia (IXT) and the association with the control of IXT. Methods. Ninety-two patients with IXT (8–15 years old) were compared with 86 controls. Exodeviation control was evaluated using the Revised Newcastle Control Score. Angle of deviation was measured using prism and alternate cover testing at distance and near. Fusional vergence was measured using prism bar and synoptophore. This study was registered with ChiCTR-RCC-13003920. Results. Using prism bar, convergence break points were lower whereas divergence break points were higher in children with IXT at distance (P < 0.001) and near (P < 0.001) compared with controls. There was no significant difference in mean divergence amplitudes between the two groups when testing using a synoptophore (P = 0.53). In children with IXT, the distance between recovery point and break point in both convergence (distance: P = 0.02; near: P = 0.02) and divergence (distance: P < 0.001; near: P < 0.001) was larger than controls when detected by prism bar and synoptophore (convergence: P = 0.005; divergence: P = 0.006). Conclusions. Children with IXT have reduced convergence amplitudes as detected by both prism bar and synoptophore.

Surrendering control, or nothing to lose: Parents' preferences about participation in a randomised trial of childhood strabismus surgery

BACKGROUND

Intermittent exotropia is the most common form of divergent strabismus (squint) in children. Evidence regarding its optimum management is limited. A pilot randomised controlled trial has recently been completed (Surgery versus Active Monitoring in Intermittent Exotropia trial) to determine the feasibility of a full randomised controlled trial.

PURPOSE

To identify drivers for and barriers against parents' participation in Surgery versus Active Monitoring in Intermittent Exotropia and to seek their views on information received, the need for randomisation, and enhancing acceptability.

METHODS

Multiple method qualitative study using semi-structured telephone interviews to explore parents' motivations and trial screening logs to provide an indication of common barriers. Exploratory thematic analysis identified key themes.

RESULTS

A total of 48 interviews were conducted (14 participants; 34 non-participants). Barriers included no desire for surgery/preference to 'wait and see', wanting surgery immediately, feeling uncomfortable about 'surrendering control' over decision-making/being managed 'at random', lack of confidence in the effectiveness of surgery, believing the risks outweighed the benefits, and lack of trust. Drivers included desiring surgery, 'nothing to lose', benefits offsetting the risks, and being in a trial would result in better care. Some also mentioned 'doing their bit' for research. Suggestions for enhancing acceptability included allowing choice of treatment group, giving more time for decision-making, expanding on information given, and improving communication. Many felt the necessity of randomisation was adequately explained, but there was some indication that it was misunderstood. Information extracted from the screening logs of 80/89 eligible non-participants indicated the most prevalent barrier was not wanting surgery/preferring to observe (56%), followed by desiring surgery straightaway (15%). Opposition to randomisation/wanting to retain control was recorded in 9% of cases as was the belief that the child's squint was not severe enough to warrant surgery.

LIMITATIONS

Interviews were not audio-recorded. Not all who consented to interview could be contacted, although the response/contact rate was good (48/62). A few parents did not provide reasons for refusing the trial.

CONCLUSION

Opposition to surgery and concerns about surrendering control were common obstacles to participation, whereas parents keen for their child to undergo the operation but happy to defer tended to embrace a 'nothing to lose' attitude. Many non-participants would have consented if allowed to choose group, although most of these would have chosen observation. While most parents felt happy with information given and that randomisation was adequately explained, it is of concern that there may be some misunderstanding, which should be addressed in any trial. These findings will inform future trials in childhood exotropia, for example, consideration of preference arms and improving communication. Lessons learnt from the Surgery versus Active Monitoring in Intermittent Exotropia trial could prove valuable to paediatric and surgical trials generally.

Standardising reported outcomes of surgery for intermittent exotropia--a systematic literature review

BACKGROUND

Intermittent exotropia (IXT) is one of the most common strabismus entities worldwide, but it remains poorly understood. Investigators differ regarding which parameters should be used to characterize IXT and to evaluate interventions. Surgery is an established treatment option but problems can arise when comparing surgical effectiveness if there is a wide range of different outcome measures that can be used. This study aimed to assess the extent of standardization of reported outcomes in studies of surgery for IXT.

METHODS

With institutional R&D committee approval, we conducted, according to a predefined protocol, a systematic literature review of outcomes of surgery for IXT published in the last 10 years. The databases used were Medline and EMBASE. Two analysts independently performed the searches. The separate lists were then compared and collated to maximize our return rate for included papers and allow evaluation of our strategies.

RESULTS

Fifty-six studies met our inclusion criteria. Thirty-two were retrospective and twenty-four prospective. Outcome measures varied widely between studies and variously included ocular alignment, stereopsis, visual acuity, re-operation rate, and postoperative drift. Even for ocular alignment, there was no agreed definition of postoperative success. Time frames for assessing outcomes ranged from two months to two years after surgery.

CONCLUSIONS

The lack of harmony in outcome reporting for studies of surgery for IXT is counterproductive. We suggest 4 core outcomes for all future studies, which have already been incorporated into two current randomized trials: alignment, near stereoacuity, control score, and quality of life score.

A prospective study of fusional convergence parameters in Chinese patients with intermittent exotropia

PURPOSE

To evaluate the correlation between different fusional convergence parameters and the Newcastle Control Score (NCS) in children with intermittent exotropia.

METHODS

In this consecutive prospective observational series, 101 Chinese children with intermittent exotropia were examined by a single observer, who assessed the level of control using the revised NCS and measured the angle of deviation and fusional convergence. Levels of control were defined according to the NCS as good (0-3), moderate (4-6), or poor (7-9). The correlation between the different fusional convergence parameters and the NCS was evaluated.

RESULTS

The total convergence amplitude was similar among the different control groups (P = 0.288 and P = 0.628 at near and at distance, respectively). The convergence reserve was higher in the good control group compared with the moderate and poor control groups, both at near (P = 0.001) and at distance (P = 0.001). Among all fusional convergence parameters, we determined that the fusional reserve ratio had strongest correlation with control (near ratio: r = -0.66, P = 0.001; distant ratio: r = -0.59, P = 0.001). Among patients with a fusional reserve ratio ≥ 2 at distance, 100% (5 of 5 patients) of these patients demonstrated good control (NCS ≤ 3).

CONCLUSIONS

In children with intermittent exotropia, the total convergence amplitude was similar among different levels of control. The convergence reserve was lower in the poor control group. Fusional reserve ratio ≥ 2 was an indicator of good control in patients.

Surgery versus Active Monitoring in Intermittent Exotropia (SamExo): study protocol for a pilot randomised controlled trial

BACKGROUND

Childhood intermittent exotropia [X(T)] is a type of strabismus (squint) in which one eye deviates outward at times, usually when the child is tired. It may progress to a permanent squint, loss of stereovision and/or amblyopia (reduced vision). Treatment options for X(T) include eye patches, glasses, surgery and active monitoring. There is no consensus regarding how this condition should be managed, and even when surgery is the preferred option clinicians disagree as to the optimal timing. Reports on the natural history of X(T) are limited, and there is no randomised controlled trial (RCT) evidence on the effectiveness or efficiency of surgery compared with active monitoring. The SamExo (Surgery versus Active Monitoring in Intermittent Exotropia) pilot study has been designed to test the feasibility of such a trial in the UK.

METHODS

DESIGN

an external pilot patient randomised controlled trial.

SETTING

four UK secondary ophthalmology care facilities at Newcastle NHS Hospitals Foundation Trust, Sunderland Eye Infirmary, Moorfields Eye Hospital and York NHS Trust.

PARTICIPANTS

children aged between 6 months and 16 years referred with suspected and subsequently diagnosed X(T). Recruitment target is a total of 144 children over a 9-month period, with 120 retained by 9-month outcome visit.Randomisation: permuted blocks stratified by collaborating centre, age and severity of X(T).

INTERVENTIONS

initial clinical assessment; randomisation (eye muscle surgery or active monitoring); 3-, 6- and 9-month (primary outcome) clinical assessments; participant/proxy completed questionnaire covering time and travel costs, health services use and quality of life (Intermittent Exotropia Questionnaire); qualitative interviews with parents to establish reasons for agreeing or declining participation in the pilot trial.

OUTCOMES

recruitment and retention rates; nature and extent of participation bias; nature and extent of biases arising from crossover or loss to follow-up; reasons for agreeing/declining participation; variability of cure rates (to inform power calculations for a definitive RCT); completion rates of outcome measures.

DISCUSSION

The SamExo pilot trial will provide important pointers regarding the feasibility of a full RCT of immediate surgery versus deferred surgery/active monitoring. The results of this pilot, including differences in cure rates, will inform the design of a definitive RCT.

TRIAL REGISTRATION

ISRCTN44114892.

The improving outcomes in intermittent exotropia study: outcomes at 2 years after diagnosis in an observational cohort

Background

The purpose of this study was to investigate current patterns of management and outcomes of intermittent distance exotropia [X(T)] in the UK.

Methods

This was an observational cohort study which recruited 460 children aged < 12 years with previously untreated X(T). Eligible subjects were enrolled from 26 UK hospital ophthalmology clinics between May 2005 and December 2006. Over a 2-year period of follow-up, clinical data were prospectively recorded at standard intervals from enrolment. Data collected included angle, near stereoacuity, visual acuity, control of X(T) measured with the Newcastle Control Score (NCS), and treatment. The main outcome measures were change in clinical outcomes (angle, stereoacuity, visual acuity and NCS) in treated and untreated X(T), 2 years from enrolment (or, where applicable, 6 months after surgery). Change over time was tested using the chi-square test for categorical, Wilcoxon test for non-parametric and paired-samples t-test for parametric data.

Results

At follow-up, data were available for 371 children (81% of the original cohort). Of these: 53% (195) had no treatment; 17% (63) had treatment for reduced visual acuity only (pure refractive error and amblyopia); 13% (50) had non surgical treatment for control (spectacle lenses, occlusion, prisms, exercises) and 17% (63) had surgery. Only 0.5% (2/371) children developed constant exotropia. The surgically treated group was the only group with clinically significant improvements in angle or NCS. However, 8% (5) of those treated surgically required second procedures for overcorrection within 6 months of the initial procedure and at 6-month follow-up 21% (13) were overcorrected.

Conclusions

Many children in the UK with X(T) receive active monitoring only. Deterioration to constant exotropia, with or without treatment, is rare. Surgery appears effective in improving angle of X(T) and NCS, but rates of overcorrection are high.