Comparison of Alternate Part-time Patching and Pencil Push-up Training for Patients with Intermittent Exotropia

Background To compare the effect of alternate part-time patching and pencil push-up training on control ability in patients with intermittent exotropia. Methods Patients (3-7 years of age) with previously untreated intermittent exotropia were randomly assigned to receive alternate part-time patching, pencil push-up training or observation. Control ability was assessed using the Office Control Score. Stereoacuity at 40cm was evaluated with Titmus. Results were compared after 12-weeks follow-up. Results Ninety-two patients (28 in patching, 30 in pencil push-up and 34 in observation group) completed baseline and 12-week follow-up assessments. On the basis of 6-point scale, the mean deviation control was significantly better in patching and pencil push-up group after 12 weeks at distance (P=0.002 and 0.026, respectively). Furthermore, there was greater control changes in patching and pencil push-up groups in comparison with observation group from baseline to 12 weeks (P༜0.001;P=0.003, respectively). After 12 weeks of treatment, stereoacuity and stereoacuity changes were not significantly different between either of the intervention group and control group (P=0.140 and 0.393, respectively). Conclusions Based on the common office control scales, alternate part-time patching and pencil push-up training were effective treatment strategies for intermittent exotropia.

Inter-eye Differences in Ocular Biometric Parameters of Concomitant Exotropia

Purpose: To evaluate the ocular biometric parameters in patients with constant and intermittent exotropia by the measurement of swept-source optical coherence tomography (SS-OCT) optical biometer OA-2000 and comparing it with the normal control subjects.Design: Cross-sectional case-control study.Participants: Fifty-five constant and 24 intermittent patients with exotropia with central fixation and 77 orthotropic normal control participants aged 4–18 years old.Methods: Non-contact and high-resolution optical biometric OA-2000 measurements were conducted under uniform ambient light conditions. The statistical analysis included intraclass correlation coefficient (ICC), Bland-Altman plot, and independent t-tests.Main Outcome Measures: Spherical equivalent (SE), ocular biological parameters such as pupil diameter (PD), anterior chamber depth (ACD), lens thickness (LT), and axial lengths (AL). The absolute values of inter-eye differences for SE, PD, ACD, LT, and AL were recorded as AnisoSE, AnisoPD, AnisoACD, AnisoLT, and AnisoAL, respectively.Results: AnisoSE (0.878 vs. 0.577, P = 0.019), AnisoAL (0.395 vs. 0.208, P = 0.001), AnisoACD (0.060 vs. 0.032, P < 0.001), AnisoLT (0.060 vs. 0.031, P = 0.002), and AnisoPD (0.557 vs. 0.340, P = 0.002) were significantly larger in concomitant patients with exotropia. The SE, AL, ACD, LT, and PD showed excellent binocular correlation with ICC values that ranged from 0.943 to 0.987 in control participants and from 0.767 to 0.955 in concomitant exotropia patients. Bland-Altman plots showed the wider range of agreement in patients with concomitant exotropia than the control participants (SE: 5.0288 vs. 3.3258; AL: 2.2146 vs. 1.3172; ACD:0.3243 vs. 0.1682; PD: 2.4691 vs. 1.9241; and LT:0.3723 vs 0.1858).Conclusion: Patients with concomitant exotropia showed larger inter-eye differences in SE, ACD, LT, PD, and AL. Advice should be given to suspicious children to avoid or delay the development of concomitant exotropia.

Binocular Summation Is Intact in Intermittent Exotropia After Surgery

Purpose: To determine binocular summation of surgically treated intermittent exotropia (IXT) patients by measuring the contrast threshold.Methods: We recruited 38 surgically treated IXT patients aged 8–24 years and 20 age-matched healthy controls. All participants had normal or corrected-to-normal visual acuity (Snellen ≥ 20/20) in both eyes. The IXT patients had undergone the surgery at least a year prior to the study. Twenty-one of them obtained good alignment and 17 experienced a recurrence of exotropia. We measured the observers' monocular and binocular contrast sensitivities (CS) at six spatial frequencies (1.5, 3, 6, 12, 18, 24 cycles/degree) as an index of visual information processing at the threshold level. Binocular summation was evaluated against a baseline model of simple probability summation based on the CS at each spatial frequency and the area under the log contrast sensitivity function (AULCSF).Results: The exo-deviation of IXTs with good alignment was −6.38 ± 3.61 prism diopters (pd) at 33 cm and −5.14 ± 4.07 pd at 5 m. For the patients with recurrence, it was −23.47 ± 5.53 pd and −21.12 ± 4.28 pd, respectively. There was no significant difference in the binocular summation ratio (BSR) between the surgically treated IXT patients, including those with good alignment and recurrence, and normal controls at each spatial frequency [F(2,55) = 0.416, P = 0.662] and AULCSF [F(2,55) = 0.469, P = 0.628]. In addition, the BSR was not associated with stereopsis (r = −0.151, P = 0.365).Conclusion: Our findings of normal contrast sensitivity binocular summation ratio in IXT after surgical treatment suggest that the ability of the visual cortex in processing binocular information is intact at the contrast threshold level.

Outcomes of Early Surgery in Children under Four Years Old with Large Angle Intermittent Exotropia

Purpose: To find out the significance of early surgery in children of 4 years old and under with large angle intermittent exotropia of 35 prism diopters (PD) and more by examining the results of bilateral lateral rectus recession surgery and factors influencing the surgical outcome.Methods: It was a retrospective study of patients who underwent bilateral lateral rectus muscle recession surgery between 2006 to 2016 with intermittent exotropia greater than or equal to 35 PD and who were able to follow-up for at least 2 years after surgery were divided into two groups based on age of 4 years old. The surgical motor success was defined as exodeviation less than 10 PD, esodeviation less than 8 PD. The angle of deviation, binocular function, best corrected visual acuity, and amount of corrected PD per lateral recession (PD/mm) were compared at each observation point after surgery.Results: The motor success of bilateral rectus muscle recession surgery was 85% in children of age 4 years and under, 65.5% in age over 4 years. Success rate of early surgery was 1.3 times higher in younger age group, but there was no statistical meaning. The complication of surgery after 2 years of follow up was less in younger group-the rate of recurrent exotropia was 15% in younger group, 31.3% in older group and the rate of consecutive esotropia was 0% and 3.1%, respectively. Stereoacuity after 2 years of surgery was not fall behind in younger group compared to older group.Conclusions: It is possible to obtain good surgical results by performing early surgery rather than hesitating to operate due to the younger age in patients younger than 4 years old with large angle exotropia of 35 PD and more for long-term follow up and efficient patient management.

Changes in Hypertropia in Patients with Asymmetric Inferior Oblique Overaction after Symmetric Inferior Oblique Myectomy

Purpose: This study assessed the effects of bilateral inferior oblique myectomy for hypertropia on the preoperative vertical deviation angle in patients with asymmetric primary inferior oblique overaction (IOOA).Methods: This study included patients who underwent bilateral inferior oblique myectomy and lateral rectus recession due to asymmetric primary IOOA and intermittent exotropia, and were followed up for at least 6 months postoperatively. Pre- and post-operative vertical deviation angles were compared. The correlation between the extent of correction of vertical deviation after surgery and residual hypertropia, according to the preoperative degree of vertical deviation and difference between bilateral IOOA, was evaluated.Results: This study included 178 eyes from 89 patients. The angle of hypertropia in the primary position was reduced from 3.2 ± 2.2 prism diopters (PD) preoperatively to 0.5 ± 2.5 PD postoperatively (Wilcoxon signed-rank test, p < 0.001). No significant correlation was observed between the preoperative interocular difference in IOOA and postoperative extent of correction of the vertical deviation (r = 0.044, p = 0.684), or between the preoperative difference in bilateral IOOA and residual hypertropia (Spearman's rank-order correlation, r = -0.084, p = 0.432). Increased preoperative hypertropia correlated with a greater extent of surgical correction of the vertical deviation (r = 0.733, p < 0.001). Preoperative hypertropia had no significant correlation with residual hypertropia (Spearman's rank-order correlation, r = 0.182, p = 0.087).Conclusions: In symmetric bilateral inferior oblique myectomy with bilateral lateral rectus recession for asymmetric bilateral primary IOOA with V-type intermittent exotropia, a positive correlation between the degree of preoperative vertical deviation and extent of correction of the vertical deviation was observed. Additionally, IOOA and hypertropia were significantly improved postoperatively.

A Dichoptic Optokinetic Nystagmus Paradigm for Interocular Suppression Quantification in Intermittent Exotropia

Purposes: To investigate the effectiveness of a dichoptic optokinetic nystagmus (dOKN) test to objectively quantify interocular suppression in intermittent exotropia (IXT) patients during the states of orthotropia and exodeviation.Methods: The OKN motion in subjects (15 controls and 59 IXT subjects) who viewed dichoptic oppositely moving gratings with different contrast ratios was monitored and recorded by an eye tracker. Interocular suppression in control subjects was induced using neutral density (ND) filters. The OKN direction ratios were fitted to examine the changes of interocular suppression in subjects under different viewing states. Two established interocular suppression tests (phase and motion) were conducted for a comparative study.Results: The dOKN test, which requires a minimal response from subjects, could accurately quantify the interocular suppression in both IXT and control subjects, which is in line with the established interocular suppression tests. Overall, although comparative, the strength of interocular suppression detected by the dOKN test (0.171 ± 0.088) was stronger than those of the phase (0.293 ± 0.081) and the motion tests (0.212 ± 0.068) in the control subjects with 1.5 ND filters. In IXT patients, when their eyes kept aligned, the dOKN test (0.58 ± 0.09) measured deeper visual suppression compared with the phase (0.73 ± 0.17) or the motion test (0.65 ± 0.14). Interestingly, strong interocular suppression (dOKN: 0.15 ± 0.12) was observed in IXT subjects during the periods of exodeviation, irrespective of their binocular visual function as measured by synoptophore.Conclusion: The dOKN test provides efficient and objective quantification of interocular suppression in IXT, and demonstrates how it fluctuates under different eye positions.

Effects of Orthoptic Therapy in Children with Intermittent Exotropia After Surgery: Study Protocol for a Randomized Controlled Trial

Background Intermittent exotropia (IXT) is the most common type of exotropia in China. Surgery is usually required to align the eye deviation to maintain or obtain better binocular visual function. However, there is a high rate of exodrift or recurrence in surgically treated patients. Orthoptic therapy is sometimes recommended for IXT patients after surgery. However, there is a lack of high-quality randomized controlled trials to prove that orthoptic therapy could be an effective supplement to surgical treatment for IXT patients. This study was designed to confirm such an application. This report describes the design and methodology of the Intermittent Exotropia Post-operative Treatment Clinical Trial, which is the first large-sample, blank-controlled, randomized clinical trial. Methods A total of 136 IXT patients (aged 7 to 17 years) will be enrolled and assigned to the orthoptic therapy group or blank control group according to a simple randomization scheme. Patients in the orthoptic therapy group will receive at least 2 months of orthoptic therapy, such as anti-suppression, vergence, and accommodation training. Patients in the blank control group will receive only refractive correction. All enrolled patients will need regular follow-up observation until 2 years after surgery. The primary outcome will be the proportion of participants meeting suboptimal surgical outcomes in this 2-year follow-up, which is defined as (1) exodeviation of 10 prism diopters (PD) at distance or near using the simultaneous prism and cover test (SPCT) or (2) loss of 2 or more octaves of stereoacuity from baseline, at any masked follow-up visit examination. The secondary outcomes will be the exodeviation at distance and near using the simultaneous prism and alternate cover test (PACT), magnitude of fusional convergence, stereoacuity, and accommodation. Measurements will be taken at baseline and at the 6-, 12-, 18-, and 24-month follow-ups. Discussion To the best of our knowledge, this will be the first prospective, randomized controlled study of binocular training in IXT patients after surgery. The aim of this work is to confirm the efficacy of orthoptic therapy in reducing the proportion of recurrence among IXT patients after surgery and improving binocular vision function. Trial registration: Chinese Clinical Trial Registry ChiCTR1900026891. Registered on 25 October 2019.

The reliability of the angle of deviation measurement from the Photo-Hirschberg tests and Krimsky tests

Objective To compare the angle of deviation measured from Photo-Hirschberg testing and Krimsky testing, with that from an alternate prism cover test (APCT) in strabismus patients. Methods A cross-sectional study was conducted in Songklanagarind Hospital, Thailand. Thirty-three strabismus patients were photographed for analysis by Photo-Hirschberg testing using computer software. The corneal light reflex displacement, converted into prism diopter (PD), was compared to the angle of deviation measured with APCT. Twenty-eight strabismus patients were tested with the Krimsky test. Data were analyzed using Pearson correlation and paired t-tests. The study excluded 4 intermittent exotropia cases, 1 intermittent esotropia case and 2 which cases missing data for krimsky test. Results The mean±SD of the deviation angle, measured by APCT with a fixation target at 30 cm and 6 m; were 48.09±16.34PD and 47.82±15.73 PD, respectively. At 1 m, the difference in the angle of deviation measured from APCT and the Photo-Hirschberg test within 10 PD were 58.8% and 63.6%, for ET and XT, respectively. The difference in the angle of deviation measured from APCT and Krimsky tests within 10 PD in ET and XT were 86.7% and 80.0%, respectively. At 4 m, the difference in angle of deviation measured from APCT and Photo-Hirschberg tests within 10 PD in ET and XT were 58.8% and 54.5%, respectively; whereas, the difference in the angle of deviation measured from APCT and Krimsky tests within 10 PD in ET and XT were 80.0% and 70.0%, respectively. Conclusion The reliability of Krimsky test was better than Photo-Hirschberg test for measuring an angle of deviation.

Functional changes of visual cortex in pre- and post- operative intermittent exotropia patients: study protocol for a non-randomized 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 insufficient maintaining of sensory and motor fusion. Recent reports have demonstrated the relationship between IXT and visual cortical impairment. We plan to assess blood oxygen level-dependent (BOLD)- functional magnetic resonance imaging (fMRI) in IXT patients during the pre-and post- operation follow-ups to evaluate the functional changes of the visual cortex. Methods and analysis: A total of 90 Chinese subjects will be recruited, and the age is between 18 and 60 years old. The subjects include the Surgical treatment (ST) group (45 IXT subjects who will perform surgery) and the Healthy control (HC) group (45 age - and sex - and education matched healthy volunteers). The assessments include the following aspects: general ophthalmic, optometry, binocular vision test, Newcastle Control Score (NCS), and fMRI. Each subject completes the rest-state BOLD-fMRI, and the sequences include echo planar imaging (EPI) pulse and 3-dimensional brain volume (3D-BRAVO) to acquire high-resolution images. The follow-up schedule is 6 and 12months after the surgery. The primary outcome will be determined by cortex changes in BOLD-fMRI in ST group before and after the surgery. We also compare the HC group with the pre-operation subjects in the ST group. The secondary outcomes are changes of strabismus examinations, binocular visual function examinations, and NCS. Ethics and dissemination: Ethical approval has been obtained from the Medical Ethics Committee of the Beijing Tongren Hospital. We plan to publish the results of this study in a peer-reviewed journal article. Trial registration number: ChiCTR2100048852 Keywords: Intermittent exotropia, Functional magnetic resonance imaging, Fusion function, Strabismus, Visual cortex