Variability of preoperative measurements in intermittent exotropia and its effect on surgical outcome

Refractive surgery as a treatment tool for strabismus: systematic review

The impact refractive surgery has on preoperative horizontal strabismus is rapidly evolving, and this knowledge can provide valuable clinical context when considering refractive surgery as a treatment for strabismus. 515 studies were identified, of which 26 met the inclusion criteria. Analysis indicated that refractive surgery resulted in an overall decrease in the mean uncorrected postoperative angle of deviation caused partially or fully due to refractive error and highlighted the varied outcome of refractive surgery on nonaccommodative horizontal strabismus with limited evidence to suggest refractive surgery for this type of strabismus. Efficacy of refractive surgery in reducing concomitant horizontal strabismus depends on several factors: type of horizontal ocular deviation, patient age, and extent of refractive error. Refractive surgery can be an effective treatment for refractive accommodative horizontal strabismus in patients with stable, mild to moderate myopia or hyperopia and should be considered with careful patient selection for optimum outcome.

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.

The subjective controllability of exotropia and its effect on surgical outcomes in patients with intermittent exotropia

BACKGROUND/AIMS

We evaluate the clinical characteristics of intermittent exotropia with controllability and compare surgical outcomes between patients with and without controllability.

METHODS

We reviewed the medical records of patients aged 6-18 years with intermittent exotropia who underwent surgery between September 2015 and September 2021. Controllability was defined as the patient's subjective awareness of exotropia or diplopia associated with the presence of exotropia and ability to instinctively correct the ocular exodeviation. Surgical outcomes were compared between patients with and without controllability, with a favorable surgical outcome defined as an ocular deviation between ≤ 10 PD of exotropia and ≤ 4 PD of esotropia at distance and near.

RESULTS

Among 521 patients, 130 (25%, 130/521) had controllability. The mean age of onset (7.7 years) and surgery (9.9 years) were higher in patients with controllability than in those without controllability (p < 0.001). The mean control scores of patients with controllability (distance: 1.9, near: 1.5) were lower compared with patients without controllability (distance: 3.0, near: 2.2), reflecting a better level of control. Patients with controllability had a better surgical outcome than those without controllability, as analyzed by log-rank test (p < 0.001). Larger preoperative ocular exodeviation at distance (hazard ratio [HR] = 1.083, confidence interval [CI] = 1.018-1.151, p = 0.012) and near (HR = 1.102, CI = 1.037-1.172, p = 0.002) were significantly related to recurrence in patients with controllability.

CONCLUSIONS

Patients with controllability showed better surgical outcomes, later exotropia onset, and better level of control than patients without controllability. Preoperative ocular exodeviation was a significant factor influencing favorable outcomes in patients with controllable exotropia.

How to Better Treat Patients with Intermittent Exotropia: A Review of Surgical Treatment of Intermittent Exotropia

Intermittent exotropia (X(T)) is the most common form of strabismus, especially in Asians. Treatment of X(T) includes occlusion, overminus lens, and surgery, of which, surgery is the mainstay of treatment. Commonly performed surgical procedures for X(T) are bilateral lateral rectus muscle recession or unilateral lateral rectus recession with medial rectus resection; however, it is unclear which of the two surgeries is more effective. The purpose of this review is to provide an insight on the surgical treatment of X(T). Randomized controlled trials, comparative observational studies, and case series with a large number of patients as well as a long follow-up period of over a year were included.

The Association between Level of Control and Exodeviation after the Monocular Occlusion Test in Pediatric Patients with Intermittent Exotrop

Purpose

We investigated the association between the level of control and exodeviation after the monocular occlusion test (MO) in pediatric patients with intermittent exotropia.

Methods

We retrospectively reviewed the records of pediatric patients with intermittent exotropia who visited Yeungnam University Hospital between September 2015 and December 2020. The largest exodeviation obtained before and after 1 hour of MO were compared. The LACTOSE (Look And Cover, then Ten seconds of Observation Scale for Exotropia) control scoring system was used to measure the level of control. Controllability was defined when the patient had the subjective awareness of exotropia and the instinctive ability to correct ocular deviation.

Results

Five hundred and three consecutive patients (260 male and 243 female patients; mean age, 7.8 years) were included. In all control scores, exodeviation significantly increased after the MO (p < 0.001). However, the patients with an increase in exodeviation ≥5 prism diopters (PD) after the test did not show any significant association with the control scores. The presence of controllability was significantly associated with an increase of ≥5 PD at near (p = 0.034).

Conclusions

Exodeviation showed significant increase after the MO, regardless of the level of control, in pediatric patients with intermittent exotropia. There was no significant association between the control scores and an increase of ≥5 PD after the MO. Patients with controllability were more likely to show increase in exodeviation after the MO.

Altered Spontaneous Brain Activity Patterns and Functional Connectivity in Adults With Intermittent Exotropia: A Resting-State fMRI Study

The purpose of this study is to investigate brain functional changes in patients with intermittent exotropia (IXT) by analyzing the amplitude of low-frequency fluctuation (ALFF) of brain activity and functional connectivity (FC) using resting-state functional magnetic resonance imaging (rs-fMRI). There were 26 IXT patients and 22 age-, sex-, education-, and handedness-matched healthy controls (HCs) enrolled who underwent rs-fMRI. The ALFF, fractional ALFF (fALFF) values in the slow 4 and slow 5 bands, and FC values were calculated and compared. The correlations between ALFF/fALFF values in discrepant brain regions and clinical features were evaluated. Compared with HCs, ALFF/fALFF values were significantly increased in the right angular gyrus (ANG), supramarginal gyrus (SMG), inferior parietal lobule (IPL), precentral gyrus (PreCG), and the bilateral inferior frontal gyri (IFG), and decreased in the right precuneus gyrus (PCUN), left middle occipital gyrus (MOG), and postcentral gyrus (PoCG) in IXT patients. The Newcastle Control Test score was negatively correlated with ALFF values in the right IFG (r = −0.738, p < 0.001). The duration of IXT was negatively correlated with ALFF values in the right ANG (r = −0.457, p = 0.049). Widespread increases in FC were observed between brain regions, mainly including the right cuneus (CUN), left superior parietal lobule (SPL), right rolandic operculum (ROL), left middle temporal gyrus (MTG), left IFG, left median cingulate gyrus (DCG), left PoCG, right PreCG, and left paracentral gyrus (PCL) in patients with IXT. No decreased FC was observed. Patients with IXT exhibited aberrant intrinsic brain activities and FC in vision- and eye movement-related brain regions, which extend current understanding of the neuropathological mechanisms underlying visual and oculomotor impairments in IXT patients.

Changes in Exodeviation after the Monocular Occlusion Test in Adult Patients with Intermittent Exotropia and Its Association with the Level of Control

Purpose

We investigated the changes in ocular deviation after the monocular occlusion test in adults with intermittent exotropia and evaluated its association with the level of control.

Methods

We retrospectively enrolled adults (aged ≥18 years) with intermittent exotropia who visited our clinic between September 2015 and May 2019. Patients with basic intermittent exotropia with a distant deviation within 10 prism diopters (PD) of the near deviation were included. The largest ocular deviations obtained before and after 1 hour of monocular occlusion were compared. The level of control was measured using the LACTOSE (Look and Cover, then Ten seconds of Observation Scale for Exotropia) control scoring system.

Results

Forty-six consecutive adult patients (28 males, 18 females; mean age, 34.3 years) were enrolled. The mean ocular deviation was 36.3 PD (range, 18 to 5 PD) at distant fixation and 38.5 PD (range, 18 to 80 PD) at near fixation, which increased significantly to 38.5 PD (p = 0.043) and 41.1 PD (p = 0.011), respectively, after monocular occlusion. The mean ocular deviation increased ≥5 PD in 14 (30.4%) and 15 (32.6%) patients at distant and near fixation, respectively. The level of control was measured in 30 patients. A higher degree of near control was significantly associated with an increase of ≥5 PD in near fixation after the test (p = 0.009 for a near control score ≤2).

Conclusions

The monocular occlusion test may help to determine the largest ocular deviation in adults with intermittent exotropia. Approximately one-third of patients exhibited an increase in ocular deviation ≥5 PD. Patients exhibiting good control were more likely to manifest an increase in the ocular deviation.

Dramatic Decrease in Ocular Deviation 1 Day before Surgery in Patients with Intermittent Exotropia

Purpose

To evaluate the clinical characteristics of patients with intermittent exotropia who exhibited a dramatic decrease in ocular deviation 1 day before surgery.

Methods

This study retrospectively enrolled patients with intermittent exotropia who underwent surgery between December 2013 and December 2019. Those who exhibited a decrease in ocular alignment ≥10 prism diopters (PD) at the last examination (1 day before surgery) compared with the largest previous angle of deviation were included. A monocular occlusion test was performed to re-confirm the largest angle of ocular deviation.

Results

Among 547 patients with intermittent exotropia, 10 (six females; mean age, 8.6 years) exhibited a dramatic decrease in ocular deviation before impending surgery. The mean largest angle of deviation was 31.0 PD (range, 20 to 50 PD) at distance and 34.5 PD (range, 20 to 55 PD) at near. The mean control scores using the LACTOSE (Look and Cover then Ten Seconds of Observation Scale for Exotropia) scoring system were 2.5 at distance, 1.8 at near, and 4.3 when combined. Mean ocular deviation prior to the impending surgery decreased to 7.4 PD (range, 0 to 10 PD) at distance and 6.2 PD (range, -10 to 10 PD) at near. The largest angle of ocular deviation was re-confirmed using the monocular occlusion test in all patients. All patients underwent surgery as planned, and none exhibited postoperative overcorrection.

Conclusions

A relatively small number of patients with intermittent exotropia exhibited a dramatic decrease in ocular alignment 1 day before surgery but demonstrated a relatively better level of control. The monocular occlusion test was helpful in re-confirming the largest angle of ocular deviation.

Comparison Between Parental Observations and Clinical Evaluation Findings in Korean Pediatric Patients With Intermittent Exotropia

PURPOSE

To compare parental observations with the clinical evaluation findings in pediatric patients with intermittent exotropia and evaluate the clinical factors associated with the parental observations.

METHODS

This prospective study included either one or both parents of pediatric patients with intermittent exotropia who visited the clinic between January and May 2019. The parental observations were assessed through a questionnaire that included questions on the age of onset, usually deviated eye, degree of awareness, and frequency of exotropia. These findings were compared with those of the clinical evaluations, including the amount of ocular deviation and level of control.

RESULTS

A total of 100 parents (mean age: 39.7 years; 78 women) of 95 pediatric patients (mean age: 8.2 years; 47 girls) with intermittent exotropia participated in the study. The parental observation and clinical evaluation findings on the usually deviated eye showed good concordance (74%). The degree of parental awareness did not show any association with the amount of deviation. However, it showed a statistically significant increase associated with the worsening level of distance control (P = .04). The parental observations of the frequency of exotropia significantly increased with the worsening of the level of near (P = .037) and overall (P = .019) control.

CONCLUSIONS

Parental observations are more likely to correlate with the level of control than with the amount of ocular deviation in pediatric patients with intermittent exotropia. [J Pediatr Ophthalmol Strabismus. 2020;57(3):199-203.].

Surgical management of intermittent exotropia: do we have an answer for all?

Intermittent exotropia (X(T)) is one of the most common form of strabismus with surgery being the mainstay of treatment. The main goal of surgery is to preserve binocular vision and stereopsis and to prevent its further loss. The decision to operate is mainly based on four aspects: increasing angle of exodeviation, deteriorating control of X(T), decrease in stereopsis for near or distance and quality of life. Bilateral lateral rectus muscle recession and unilateral lateral rectus recession with medial rectus resection, are the two most common surgical procedures performed and have been studied extensively in basic, divergence excess and convergence insufficiency types of X(T). However, there is no consensus over the relative efficacy of the two procedures in terms of postoperative alignment, residual or recurrent exotropia and consecutive esotropia with widely variable results, which can be attributed to poor understanding of the natural course of the disease. Multiple demographic, clinical and anatomic features that may influence the surgical outcomes have been studied to explain this variability. Moreover, most of the evidence regarding surgical outcomes of X(T) is from retrospective studies and the ongoing randomised prospective trials can shed light on long-term efficacy of these procedures. The goal of this review is to give a comprehensive overview of the outcomes of various surgical techniques in the management of different types of X(T), the preoperative and postoperative factors that may affect the surgical outcomes and to discuss the dilemmas faced by the treating surgeons including the effective management of overcorrection and undercorrection.

Relation between early postoperative deviation and long-term outcome after unilateral lateral rectus recession and medial rectus resection for adult exotropia

AIM

To evaluate the relationship between early postoperative deviation and long-term outcome after unilateral recession and resection surgery for adult exotropia, and to evaluate exotropic shift after surgery.

METHODS

This was a retroprospective study involving adult patients with exotropia who underwent unilateral recession and resection surgery and were followed up for at least 2y. The results were evaluated at 2y and the final visit. Factors influencing a successful outcome were analyzed. Early postoperative deviation at 1wk was used to evaluate relationship with long-term outcome. The long-term outcome was classified into 3 groups: successful, acceptable, and poor. Successful outcome was defined as a distance deviation between esodeviation 8 prism diopters (PD) and exodeviation 10 PD.

RESULTS

Forty-two patients were enrolled. The mean age at surgery was 26y (range, 15-49y). The median follow-up period was 30mo (range, 24-108mo). Successful outcome was found in 81% of patients at 2y and in 71% at the final visit. Overcorrection at 1wk postoperatively was associated with a successful outcome at 2y. Initial postoperative alignment between orthotropia and esodeviation of 8 PD had the highest chance of a successful outcome (RR=2.2). The mean postoperative exotropic drift was 4.7 PD at the first month and 9.3 PD at 2y.

CONCLUSION

Initial postoperative deviation can predict long-term outcome after unilateral recession and resection surgery for adult exotropia. The most desirable outcome at 1wk post-operatively was orthotropia to small esodeviation. Most patients have exotropic drift at a subsequent follow-up, especially in the first month after surgery.