Non-Arteritic Ischemic Optic Neuropathy Following COVID-19 Vaccination in Korea: A Case Series

Background@#To report the clinical manifestations of non-arteritic anterior ischemic optic neuropathy (NAION) cases after coronavirus disease 2019 (COVID-19) vaccination in Korea. @*Methods@#This multicenter retrospective study included patients diagnosed with NAION within 42 days of COVID-19 vaccination. We collected data on vaccinations, demographic features, presence of vascular risk factors, ocular findings, and visual outcomes of patients with NAION. @*Results@#The study included 16 eyes of 14 patients (6 men, 8 women) with a mean age of 63.5 ± 9.1 (range, 43–77) years. The most common underlying disease was hypertension, accounting for 28.6% of patients with NAION. Seven patients (50.0%) had no vascular risk factors for NAION. The mean time from vaccination to onset was 13.8 ± 14.2 (range, 1–41) days. All 16 eyes had disc swelling at initial presentation, and 3 of them (18.8%) had peripapillary intraretinal and/or subretinal fluid with severe disc swelling. Peripapillary hemorrhage was found in 50% of the patients, and one (6.3%) patient had peripapillary cotton-wool spots. In eight fellow eyes for which we were able to review the fundus photographs, the horizontal cup/ disc ratio was less than 0.25 in four eyes (50.0%). The mean visual acuity was logMAR 0.6 ± 0.7 at the initial presentation and logMAR 0.7 ± 0.8 at the final visit. @*Conclusion@#Only 64% of patients with NAION after COVID-19 vaccination have known vascular and ocular risk factors relevant to ischemic optic neuropathy. This suggests that COVID-19 vaccination may increase the risk of NAION. However, overall clinical features and visual outcomes of the NAION patients after COVID-19 vaccination were similar to those of typical NAION.

Palatopharyngeal Muscle Suspension Suture Technique for Obstructive Sleep Apnea / 대한이비인후과학회지

Various treatment modalities for obstructive sleep apnea (OSA) patients were introduced including continuous positive airway pressure (CPAP), lifestyle modification, and surgery. Numerous factors such as compliance, treatment failure, and preference should be considered when deciding the treatment. In general, patients for whom CPAP or other conservative treatment modalities failed become candidates for surgical treatments. Uvulopalatopharyngoplasty is one of the most generally performed surgeries, of which success rate is relatively low. Recently, numerous techniques that can correct lateral pharyngeal obstruction for OSA patients were introduced. However, some of them are technically difficult and aggressive. In this article, we introduce a novel surgical method for OSA called palatopharyngeal muscle suspension suture technique.

An Overview of the Korean Intermittent Exotropia Multicenter Study by the Korean Association for Pediatric Ophthalmology and Strabismus

The Korean Intermittent Exotropia Multicenter Study (KIEMS), which was initiated by the Korean Association of Pediatric Ophthalmology and Strabismus, is a collaborative multicenter study on intermittent exotropia in Korea. The KIEMS was designed to provide comprehensive information, including subjective and objective findings of intermittent exotropia in a large study population. A total of 65 strabismus specialists in 53 institutions contributed to this study, which, to date, is one of the largest clinical studies on intermittent exotropia. In this article, we provide a detailed methodology of the KIEMS to help future investigations that may use the KIEMS data.

A Case of Laryngeal Lymphoepithelial Carcinoma

Laryngeal lymphoepithelial carcinoma (LEC) is a rare tumor with only 34 cases in the published literature. Epidemiologically, laryngeal LEC is extremely rare in Asian. Originally, LEC is a common type of carcinoma in nasopharynx. Laryngeal LEC resembles nasopharyngeal LEC, except that most cases of laryngeal LEC are not associated with Epstein-Barr virus. We present a case of laryngeal LEC which developed at the left false cord extending to true vocal cord, para-glottic space and pre-epiglottic space. Total laryngectomy with bilateral neck dissection was performed. LEC was reported as biopsy confirmation result. The patient underwent postoperative radiotherapy and showed no evidence of recurrence during follow-up period of 42 months. In consideration that LEC in larynx have not been reported in South Korea yet, we introduce the clinical features and treatment outcomes of laryngeal LEC with literature review.

A Case of Laryngeal Lymphoepithelial Carcinoma

Laryngeal lymphoepithelial carcinoma (LEC) is a rare tumor with only 34 cases in the published literature. Epidemiologically, laryngeal LEC is extremely rare in Asian. Originally, LEC is a common type of carcinoma in nasopharynx. Laryngeal LEC resembles nasopharyngeal LEC, except that most cases of laryngeal LEC are not associated with Epstein-Barr virus. We present a case of laryngeal LEC which developed at the left false cord extending to true vocal cord, para-glottic space and pre-epiglottic space. Total laryngectomy with bilateral neck dissection was performed. LEC was reported as biopsy confirmation result. The patient underwent postoperative radiotherapy and showed no evidence of recurrence during follow-up period of 42 months. In consideration that LEC in larynx have not been reported in South Korea yet, we introduce the clinical features and treatment outcomes of laryngeal LEC with literature review.

An Overview of the Korean Intermittent Exotropia Multicenter Study by the Korean Association for Pediatric Ophthalmology and Strabismus

The Korean Intermittent Exotropia Multicenter Study (KIEMS), which was initiated by the Korean Association of Pediatric Ophthalmology and Strabismus, is a collaborative multicenter study on intermittent exotropia in Korea. The KIEMS was designed to provide comprehensive information, including subjective and objective findings of intermittent exotropia in a large study population. A total of 65 strabismus specialists in 53 institutions contributed to this study, which, to date, is one of the largest clinical studies on intermittent exotropia. In this article, we provide a detailed methodology of the KIEMS to help future investigations that may use the KIEMS data.

Comparison of Clinical Features among Children of Multicultural Families, Ethnic Koreans and Native Koreans

PURPOSE: To explore whether genetic and environmental factors influenced ophthalmic disease among children of multicultural families, ethnic Koreans, and native Koreans. METHODS: In this retrospective study, 120 patients who visited the pediatric ophthalmology clinic of a university hospital were included. They were equally divided into three groups: a multicultural group, an ethnic Korean group, and a native Korean group. Parental nationalities, age, gender, chief complaint, visual acuity, refractive error, diagnosis at the initial visit and the extent of compliance with treatment were analyzed. RESULTS: Of the multicultural group, 14 (35%) of 40 patients were Chinese immigrants, and constituted the most common subgroup. None of the age at initial visit, gender, the prevalence of refractive error, or amblyopia status differed significantly among the three groups. In the multicultural and native Korean groups, the proportions of abnormal eye positioning as the chief complaint were higher than that of the ethnic Korean group (p = 0.005). The most common diagnosis in the two former groups was strabismus. Myopia was the most common diagnosis in the ethnic Korean group. The prevalence of strabismus in the multicultural group (55%) was significantly higher than that in the native Korean group (30%) and the ethnic Korean group (20%) (p = 0.003). The prevalence of strabismus in the multicultural group was significantly higher than in the other groups (p = 0.003). However, we found no significant difference in strabismus subtype among the three groups. In the general family group, the extent of loss to follow-up was significantly higher than in the other groups (p = 0.002). CONCLUSIONS: The chief complaint, the prevalence of ophthalmic disease, and the compliance rate differed significantly among the three groups. Both genetic and environmental factors may have played a role.

Changes of the Meibomian Gland According to Age in the Normal Korean Population

PURPOSE: To examine the changes in meibomian glands associated with aging in a normal Korean population and to estimate the differences between the upper and lower eyelid in each age group. METHODS: We performed meibography on adult subjects using an infrared charge-coupled device (CCD) camera. Each eyelid was scored based on the loss of meibomian glands, and the meiboscores of the upper and lower eyelids were summed to obtain a score for each eye. Meiboscores were evaluated according to age, sex, and upper and lower eyelid meiboscores in each age group. RESULTS: One hundred seventeen eyes of 117 people were enrolled in this study. The study subjects had an average age of 50.4 +/- 19.1 years (range, 20-92; male, 56; female, 61). There was a significant positive correlation between age and total meiboscore, upper and lower eyelid meiboscore (r = 0.578, p < 0.001; r = 0.550, p < 0.001; r = 0.524, p < 0.001). There were no significant differences in the meiboscores of the upper and lower eyelids in any age group, though meiboscores were significantly higher since 40 year-old group than 20 year-old group (p < 0.001, p < 0.001, p < 0.001, p < 0.001). CONCLUSIONS: Based on noncontact meibography in normal adult eyes, the authors concluded that prevalence of changes in the meibomian glands was about 60% and changes in meibomian glands increase with age.

Clinical Characteristics of Children Diagnosed with Migraine

PURPOSE: To analyze the clinical characteristics of visual symptoms, aspects of headache, and ophthalmologic features in children diagnosed with migraine. METHODS: The medical records of 31 Korean children who had been diagnosed with migraine by pediatric neurologists were retrospectively reviewed and visual symptoms and ophthalmologic examinations were evaluated. RESULTS: The mean age of the 31 patients was 10.8 years (range, 5-17 years). The mean age of onset of headache was 9 years (range, 4-15 years). Nineteen patients (61.3%) had the associated visual aura. Visual symptoms of the 19 patients included blurred vision, unilateral vision loss, flickering lights, scotoma, and visual hallucination in descending order. However, there was no specific abnormality observed on thorough ophthalmologic examinations. CONCLUSIONS: Most of the children diagnosed with migraine did not show any ophthalmologic problems. Careful ophthalmologic examination with an understanding of migraine should be performed and reassurance to patients may be beneficial.

Corneal Thickness Measured by Dual Scheimpflug, Anterior Segment Optical Coherence Tomography, and Ultrasound Pachymetry

PURPOSE: To compare central corneal thickness (CCT) as measured by dual rotating Scheimpflug camera (Galilei), anterior segment optical coherence tomography (AS-OCT), and ultrasound pachymetry (USP). METHODS: The measurements of CCT using a dual rotating Scheimpflug camera, AS-OCT, and USP in 40 eyes of 20 healthy subjects were compared. RESULTS: The average measurements of CCT by dual rotating Scheimpflug camera, AS-OCT, and USP were 538.10 +/- 31.36 microm, 536.20 +/- 31.21 microm, and 541.93 +/- 34.93 microm, respectively. The CCT measurement by USP was statistically significantly thicker than by the dual rotating Scheimpflug camera and AS-OCT (p = 0.017, p = 0.001, respectively). There was no significant difference between the dual rotating Scheimpflug camera and AS-OCT (p = 0.054). A significant linear correlation was observed between the dual rotating Scheimpflug camera, the AS-OCT, and the USP (r > 0.900, p < 0.001). CONCLUSIONS: The results of the 3 methods have significant correlation with each other, but the measurement by USP was significantly thicker than the dual rotating Scheimpflug camera and AS-OCT. Therefore, CCT should be interpreted in the context of the instrument used.

The Change of Rectus Muscle Length Caused by Traction with Muscle Hooks in Strabismus Surgery: The Second Report

PURPOSE: To investigate the influence of the change in medial rectus resection amount caused by traction with muscle hooks on surgical results in exotropia. METHODS: In this prospective study 38 exotropia patients underwent unilateral lateral rectus recession-medial rectus resection (R & R). After isolation of the medial rectus muscle, the length of the muscle was measured with a muscle hook, and the portion to be resected was marked using gentian violet stain with calipers. After the medial rectus was retracted with two muscle hooks in either direction, its length was measured again with the calipers. Group 1 includes the patients with the planned resection amount changed to a more 0.5-1.0 mm when the rectus muscle was retracted, while group 2 did not change with the second muscle hook. The surgical results were compared between the 2 groups at postoperative 6 months. RESULTS: Mean resection amount was changed from 5.07 +/- 0.76 mm to 5.36 +/- 0.73 mm after pulling the second muscle hook. Sixteen patients (42.1%) were included in group 1 and 22 patients (57.9%) in group 2. There was no significant statistical difference in mean preoperative and postoperative deviated angle between the two groups. Success rates defined as the ocular alignment within +/- 10 PD in the primary position at postoperative 6 months were 75.0% in group 1 and 86.3% in group 2, which is not stastistically different (p > 0.05). CONCLUSIONS: Medial rectus resection amounts can be changed with the muscle traction with two muscle hooks, which induced the planned amount of resection less than first measured resection amount. However, there was little influence on surgical outcomes from the change occurred to a maximum 1 mm in resection measurement due to traction with two muscle hooks.

Analysis of Effect of Inferior Oblique Myectomy in Patients With Inferior Oblique Overaction

PURPOSE: To investigate the effect of inferior oblique (IO) myectomy by analyzing the correlation of the amount of inferior oblique overaction (IOOA), hypertropia and excyclotorsion before, between, and after IO myectomy in patients with various degrees of IOOA. METHODS: A total of 86 eyes from 59 patients with IOOA who underwent IO myectomy were enrolled in the present study. The correlation analysis was performed for the amount of IOOA, hypertropia and excyclotorsion before and after surgery, according to the preoperative amount of IOOA, hypertropia, and excyclotorsion. RESULTS: The IOOA decreased from +2.5 +/- 0.6 before surgery to -0.01 +/- 0.25 (p < 0.05) after surgery. The vertical deviation was 5.7 +/- 6.3 prism diopter (PD) and 2.3 +/- 5.2 PD (p < 0.05) postoperatively. The amount of cyclodeviation was 15.3 +/- 7.6degrees before surgery and 6.6 +/- 5.7degrees (p < 0.05) after surgery. The amount of surgical correction for IOOA and the hypertropia was significantly correlated with preoperative deviation (p < 0.05, p < 0.05). The amount of excyclotorsion before and after surgery was also positively correlated but was not statistically significant (p = 0.05). CONCLUSIONS: IO myectomy can correct any degree of IOOA, hypertropia, and related excyclotorsion.

Refractive Errors, Amblyopia and Strabismus in 3-year-old Premature Children

PURPOSE: To evaluate the refractive status, anisometropia, amblyopia and strabismus in 3-year-old premature children. METHODS: A total of 161 eyes from 82 premature infants were retrospectively reviewed and divided into three groups according to the presence of retinopathy of prematurity (ROP) and treatment; Group 1 (68 eyes): without ROP, Group 2-1 (32 eyes): spontaneously regressed ROP, and Group 2-2 (61 eyes): regressed ROP with treatment. The incidences and clinical features of refractive errors, anisometropia, amblyopia and strabismus at the age of three years were compared among the three groups. RESULTS: The incidences of myopia, astigmatism, anisometropia and the severity of myopia increased according to the presence of ROP and treatment (p = 0.03, 0.02, 0.001, and 0.04, respectively). There were no significant differences in the incidences of hyperopia among the three groups; however, the severity of hyperopia in Group 2-2 was higher than those in the other two groups (p = 0.01). Patients in Group 1 had better best corrected visual acuity (BCVA) compared with those of the other two groups (p < 0.001). However, no significant differences in the incidences of strabismus or amblyopia among the three groups (p = 0.80 and 0.85, respectively) were found, and the ratio of esotropia : exotropia was 1:1.3. CONCLUSIONS: Regular ocular examination should be required in children who were born prematurely in order to detect and treat ophthalmologic problems such as refractive errors, amblyopia and strabismus.

The Change of Rectus Muscle Length Caused by Traction With Muscle Hooks in Strabismus Surgery-the First Report

PURPOSE: To evaluate changes in muscle length when retracting the extraocular rectus muscle with muscle hooks during strabismus surgery. METHODS: Forty-four rectus muscles of 42 patients consecutively resected in two hospitals (A, B) were included in this study. After isolation of the rectus muscle, the length of the muscle was recorded and the portion to be resected was marked using gentian violet stain on the tip of calipers. After the rectus muscle was retracted with two muscle hooks in either direction, its length was measured again with the calipers. RESULTS: The length of the rectus muscle was not changed by retraction in 25 of 44 muscles (56.8%). The length of the muscle was changed by 0.5 mm in 13 muscles (29.5%) and by 1mm in six muscles (13.6%). Changes of rectus muscle length over 0.5 mm were observed in 15 of 27 muscles of patients treated at hospital A (55.5%) and four of 17 muscles of patients treated at hospital B (23.5%). The results for the two hospitals were significantly different (p=0.037). CONCLUSIONS: Small errors in measurement can occur when muscle resections are performed during strabismus surgery. Institutional or clinician related factors may explain variations in error rates between hospitals.

The Effect of Subconjunctival Injection of Bevacizumab After Resection of Muscle in Rabbit Models

PURPOSE: To study the effects of subconjunctival injection on the conjunctiva and muscles after muscle resection in a rabbit model. METHODS: Resection surgery of 5 mm was performed on both the superior rectus muscle (SR) and the inferior rectus muscle (IR) in five white rabbits. As such, 2.5 mg bevacizumab was subconjunctivally injected around the right SR and IR in the experimental group. The left eyes were not injected and were instead used as the control group. The degrees of injection and edema of conjunctiva were classified on a scale from 0 to 4 via gross examination by five examiners at two and four weeks after surgery. The strength of the muscle attachment was assessed, and the degrees of conjunctival inflammation and inflammation and fibrosis of the muscle were classified on a scale from 0 to 4 at four weeks after surgery via histologic examination. RESULTS: The results of gross examination at two and four weeks after surgery showed positive correlation among the five examiners (k=0.52, k=0.4), although there was no statistically significant difference between the experimental and control groups (p=0.285, p=0.364). There was also no significant difference between the two groups with regard to tensile strength of the attachment (p=0.414), inflammation of the conjunctiva and muscle, or fibrosis of the muscle in histologic examination (p=0.698, p=0.702, p=0.232, respectively). CONCLUSIONS: There were no significant effects on the inflammation and fibrosis of the conjunctiva or muscles due to subconjunctival injection of 2.5 mg of bevacizumab after muscle resection in a rabbit model.

Clinical Features and Surgical Outcomes of Infantile Esotropia According to the Age at Surgery

PURPOSE: To evaluate the clinical features, surgical outcome and factors influencing the surgical outcome of infantile esotropia according to the age at surgery. METHODS: Seventy patients with infantile esotropia followed for at least 6 months after surgery, were enrolled in a retrospective study. Patients were divided into 2 groups. Group 1 included 25 patients who underwent surgery before the age of 24 months and group 2 included 45 patients who underwent surgery after 24 months of age. The clinical characteristics including age at the initial visit, refractive error, angle of deviation, associated strabismus, success rate and reoperation rate were analyzed according to the age at surgery. RESULTS: The mean angle of esodeviation before surgery was 41.71PD and refractive error was +1.26D. Patients underwent bimedial rectus recessions at the mean age of 67.33 months. The age at the initial visit was significantly older in group 2. Surgical success is defined as the ocular alignment within +/-10PD in primary position at the last visit. Fourteen patients (56%) from group 1 and 29 (64.4%) from group 2 obtained surgical success. Reoperation was performed in 8 patients (32%) from group 1 and 8 (17.8%) from group 2, which was not statistically significantly different. Stereopsis better than 3,000 seconds of arc was obtained in 3 patients (50%) from group 1 and 16 (76.2%) from group 2. CONCLUSIONS: In group 2, the late-surgery group, the success rate was 64.4% and stereopsis was obtained in 76.2%. Surgical results were not different between the two groups.

Clinical Features and Surgical Outcomes of Infantile Esotropia According to the Age at Surgery

PURPOSE: To evaluate the clinical features, surgical outcome and factors influencing the surgical outcome of infantile esotropia according to the age at surgery. METHODS: Seventy patients with infantile esotropia followed for at least 6 months after surgery, were enrolled in a retrospective study. Patients were divided into 2 groups. Group 1 included 25 patients who underwent surgery before the age of 24 months and group 2 included 45 patients who underwent surgery after 24 months of age. The clinical characteristics including age at the initial visit, refractive error, angle of deviation, associated strabismus, success rate and reoperation rate were analyzed according to the age at surgery. RESULTS: The mean angle of esodeviation before surgery was 41.71PD and refractive error was +1.26D. Patients underwent bimedial rectus recessions at the mean age of 67.33 months. The age at the initial visit was significantly older in group 2. Surgical success is defined as the ocular alignment within +/-10PD in primary position at the last visit. Fourteen patients (56%) from group 1 and 29 (64.4%) from group 2 obtained surgical success. Reoperation was performed in 8 patients (32%) from group 1 and 8 (17.8%) from group 2, which was not statistically significantly different. Stereopsis better than 3,000 seconds of arc was obtained in 3 patients (50%) from group 1 and 16 (76.2%) from group 2. CONCLUSIONS: In group 2, the late-surgery group, the success rate was 64.4% and stereopsis was obtained in 76.2%. Surgical results were not different between the two groups.

Effects of Induced Anisometropia by Refractive Surgery on Binocular Vision

PURPOSE: To evaluate the effects of induced anisometropia by refractive surgery on binocular vision and to determine the usefulness of screening tools. CASE SUMMARY: Anisometropia was induced in 7 patients by photorefractive keratectomy (PRK). Binocular vision was determined with the Titmus stereo test, Worth 4-dot test, 4 prism diopter base-out test and Bagolini striated lens test. Each test was performed before surgery, after PRK of one eye and after PRK of both eyes. After PRK of one eye, mean stereopsis by the Titmus stereo test was 1877.14 seconds of arc and after surgery of both eyes, 40 seconds of arc. After surgery of one eye, 6 patients (86.7%) showed suppression with the Worth 4 dot test at distance fixation and one patient (14.3%) at near fixation. After surgery of both eyes, all patients showed fusion with the Worth 4 dot test. After surgery of one eye, 3 patients (42.9%) showed suppression with the 4 prism diopter base-out test and after surgery of both eyes, 2 of the patients showed fusion. All patients showed fusion with the Bagolini striated lens test after surgery of one or both eyes. CONCLUSIONS: Most cases showed decreased binocular vision by the Titmus stereo test at near fixation and the Worth 4 dot test at distance fixation. The changes of binocular vision determined by each tool were variable. Therefore, improved results in evaluating binocular vision will be obtained with a combination of various tools including the Bagolini striated lens test and 4 prism base-out test.

Effects of Induced Anisometropia by Refractive Surgery on Binocular Vision

PURPOSE: To evaluate the effects of induced anisometropia by refractive surgery on binocular vision and to determine the usefulness of screening tools. CASE SUMMARY: Anisometropia was induced in 7 patients by photorefractive keratectomy (PRK). Binocular vision was determined with the Titmus stereo test, Worth 4-dot test, 4 prism diopter base-out test and Bagolini striated lens test. Each test was performed before surgery, after PRK of one eye and after PRK of both eyes. After PRK of one eye, mean stereopsis by the Titmus stereo test was 1877.14 seconds of arc and after surgery of both eyes, 40 seconds of arc. After surgery of one eye, 6 patients (86.7%) showed suppression with the Worth 4 dot test at distance fixation and one patient (14.3%) at near fixation. After surgery of both eyes, all patients showed fusion with the Worth 4 dot test. After surgery of one eye, 3 patients (42.9%) showed suppression with the 4 prism diopter base-out test and after surgery of both eyes, 2 of the patients showed fusion. All patients showed fusion with the Bagolini striated lens test after surgery of one or both eyes. CONCLUSIONS: Most cases showed decreased binocular vision by the Titmus stereo test at near fixation and the Worth 4 dot test at distance fixation. The changes of binocular vision determined by each tool were variable. Therefore, improved results in evaluating binocular vision will be obtained with a combination of various tools including the Bagolini striated lens test and 4 prism base-out test.

The Clinical Analysis after Reoperation for Recurrent Intermittent Exotropia

PURPOSE: To analyze the clinical course and relationships between the factors and surgical outcomes after reoperation for recurrent intermittent exotropia. METHODS: Surgical results were retrospectively investigated in 38 patients who had undergone reoperation at least 3 months after surgical correction. Recurrence was defined as an exodeviation of more than 10 prism diopters at the primary position. We investigated the recurrence rate according to the follow-up duration with survival analysis, and analyzed the relationships between the factors and surgical outcome. RESULTS: The mean survival period was 22.7+/-20.2 months (range, 3 to 72 months). As the follow-up duration increased, the recurrence rate progressively increased. The hazard ratio for recurrence of a unilateral medial rectus resection as a reoperation was significantly higher than that for a unilateral lateral rectus recession and medial rectus resection (recession and resection)(p=0.021). After using unilateral recession and resection as the primary surgery, the hazard ratio for recurrence of unilateral recession and resection as a reoperation was not significantly different from that for unilateral lateral rectus recession (p=0.480). After a bilateral lateral rectus recession, the hazard ratio for recurrence of unilateral medial rectus resection was not significantly different from that for bilateral medial rectus resection (p=0.076). CONCLUSIONS: The surgical options for recurrent intermittent exotropia are contralateral recession and resection or contralateral lateral rectus recession. The procedure chosen depends on the operator's preference after performing unilateral recession and resection as the primary surgery. After a bilateral lateral rectus recession, the hazard ratio for recurrence of unilateral medial rectus resection was not significantly higher than that for a bilateral medial rectus resection, but even so, a bilateral medial rectus resection may be more effective than unilateral medial rectus resection for recurrent intermittent exotropia.