Horizontal Rectus Muscles Research Articles

Vertical Transposition of the Horizontal Rectus Muscles Combined With the Modified Kestenbaum Procedure for Correcting Abnormal Head Posture Due to Infantile Nystagmus Syndrome

Vertical Transposition of the Horizontal Rectus Muscles Combined With the Modified Kestenbaum Procedure for Correcting Abnormal Head Posture Due to Infantile Nystagmus Syndrome

Corneal Curvature Change After Strabismus Surgery: An Experience from a Single-academic Center

Objective: This study aimed to explore corneal curvature changes following strabismus surgery using a quadric surface fitting model to address ocular misalignment. Material and Methods: In this prospective cross-sectional study, 54 completed cases (84 eyes) of patients aged 6–60 years old (mean 10 years old) undergoing horizontal rectus muscle surgery were examined using placido-based keratometry with the Oculus Keratograph 5M system. Data on corneal curvature were collected one week pre-operation, and again one week, one month, and three months post-operation. Asphericity in the vertical meridian (Qy) and horizontal meridian (Qx), and surgical-induced astigmatism (SIA) were calculated. Results: The 84 eyes included were categorized into three groups: horizontal muscle surgeries, oblique muscle surgery, and combined horizontal and oblique muscle surgeries. Significant corneal prolation (steep central, flat peripheral) was revealed in the vertical meridian (Qy) at 3 months postoperatively for lateral rectus (LR) recession in the first group (p < 0.001), and the mean SIA was 0.45 D (95% CI: 0.35–0.56 D). A similar effect was seen in the vertical meridian of the third group (p < 0.01), with a mean SIA at 3 months of 0.27 D (95% CI: 0.23–0.32 D). Conclusion: Lateral rectus muscle recession induces corneal vertical prolation for up to 3 months post-operation. Surgeons are thus advised to re-evaluate refraction and defer contact lens refitting, refractive surgery, and intraocular lens calculations for at least 3 months after the procedure.

Agreement between intraoperative and anterior segment optical coherence tomography measurements of the extraocular muscle insertion distance in patients with previous strabismus surgery

PurposeTo evaluate the agreement between anterior segment optical coherence tomography (AS-OCT) measurement of preoperative distance from the limbus to the horizontal rectus muscles insertion and intraoperative measurement in patients who have previously undergone strabismus surgery and required reoperation. MethodsSubjects from two ophthalmological centers were included. Preoperative AS-OCT was used to measure the muscle insertion from the limbus, and intraoperative measurements were obtained using calipers. Interclass correlation coefficient and Bland-Altman agreement analysis were used. ResultsA total of 53 horizontal rectus muscles from 24 patients with previous strabismus surgery were analyzed: 27 medial rectus (MR) and 26 lateral rectus (LR) muscles, including both previously operated and previously unoperated muscles. Average AS-OCT measurements of MR was 8.54 ± 2.42 mm and intraoperatively was 9.4 ± 3.09 mm. Average AS-OCT for LR was 8.32 ± 2.25 mm and intraoperatively was 9.34 ± 3.73 mm. 63% of MR muscles and 77% of LR muscles were within 1 mm between AS-OCT and intraoperative measurement. Spearman’s correlation coefficient showed positive correlation between measures for both MR and LR muscles. The interclass correlation coefficient was 0.79 (95% CI, 0.56-0.90) for MR muscles and 0.70 (95% CI, 0.44-0.85) for LR muscles, with a good agreement. Agreement was better for muscles ≤10 mm from the limbus (which included both previously operated and unoperated muscles) than for muscles found >10 mm from the limbus. ConclusionsGood agreement was observed between the measurement of limbus-insertion distance obtained by AS-OCT and by intraoperative measurement, especially when the muscle insertion was ≤10 mm from the limbus.

Investigation of the effects of single and two-muscle horizontal rectus surgeries on macular microvasculature.

To investigate the changes in posterior segment hemodynamics caused by horizontal rectus muscle surgeries using the optic coherence tomography angiography (OCTA). Patients who underwent at least one horizontal rectus recession, resection, or combination surgery were included. The patients were evaluated with an OCTA preoperatively and 30days postoperatively. Postoperative changes in superficial capillary plexus (SCP)-vessel density (VD), deep capillary plexus (DCP)-VD, foveal avascular zone (FAZ) area and choriocapillaris (CC)-flow area parameters were examined. The mean differences (Δ) for the parameters in which significant changes were detected in the whole operated eyes group were compared between the single- and two-muscle surgery groups. Twenty-five eyes of 24 patients with an average age of 16.40 ± 6.75years (5-29) were included. Of the eyes, 10 underwent single muscle recession surgery. Two-muscle surgeries were performed in 15 eyes. SCP-VD in the superior parafoveal region increased significantly postoperatively (53.23 ± 4.11% vs. 54.54 ± 3.67%, p = 0.032). For DCP-VD, there was a statistically significant increase in all zones, except the superior hemisphere and fovea regions (p < 0.05 for all). FAZ area did not change significantly (p = 0.207). There was a significant increase in the CC-flow area (2.171 ± 0.146 mm2 vs. 2.232 ± 0.115 mm2, p = 0.013). There was a significant difference between the two groups only for the Δ SCP-VD/parafovea superior value (-0.62 ± 0.98 vs. 1.57 ± 3.07, p = 0.019). Conventional horizontal rectus muscle surgeries may cause alterations in posterior segment hemodynamics. The number of muscles incised does not seem to greatly affect the magnitude of changes that occur. What is known • After conventional horizontal rectus muscle surgeries, the anterior ciliary arteries are not recanalized, instead, anterior segment blood flow is maintained by increasing the flow in the long posterior ciliary arteries. • Previous studies using Doppler ultrasonography have shown increased flow in the ophthalmic artery, central retinal artery and long posterior ciliary arteries. What is new • In this study, significant increases were observed in superficial and deep capillary plexus-vessel density and choriocapillaris-flow area parameters in the first postoperative month with optic coherence tomography angiography device. • Hemodynamic increases in both retinal and choroidal vasculature were detected in the early period after conventional horizontal rectus muscle surgeries. • The number of muscles incised does not seem to greatly affect the magnitude of changes that occur.

Differences in the corrective effects of vertical transposition accompanied by recession-resection of the horizontal rectus muscles for complicated vertical deviation.

To investigate whether the corrective effect differs between upward and downward transpositions or between exotropia and esotropia in vertical transposition accompanied by horizontal rectus muscle recession-resection. This prospective study investigated 41 patients with concomitant exotropia or esotropia with small-angle vertical deviation who underwent unilateral vertical transposition accompanied by horizontal rectus muscle recession-resection and were followed up for 1 year postoperatively. We analysed the vertical deviation corrective effect, defined as the corrective amount per displacement distance (°/tendon width [TW]). We compared the corrective effects between upward and downward transpositions and between exotropia and esotropia. Additionally, we investigated the correlation between the corrective effect and the studied parameters. The 1-year vertical corrective effect was 5.2 ± 4.6° (9.0 ± 8.1 prism dioptres [Δ])/TW. The 1-year vertical corrective effect of upward transposition (7.9 ± 4.0° [13.8 ± 7.0Δ]/TW) was higher than that of the downward transposition (3.9 ± 4.4° [6.8 ± 7.7Δ]/TW, P = 0.009). In contrast, upward and downward transposition did not differ between exotropia and esotropia (P = 0.62). Multivariate analyses revealed that the 1-year vertical corrective effect correlated with the vertical transposition direction (upward or downward) and preoperative vertical deviation but did not correlate with the disease type (exotropia or esotropia). The 1-year motor success (vertical deviation ≤ 5Δ) rate was 89%. The vertical corrective effect of vertical transposition accompanied by horizontal rectus muscle recession-resection is greater in upward transposition than in downward transposition; however, it does not differ between exotropia and esotropia.

The Outcome of Inferior Oblique Myectomy for Apparent Inferior Oblique Overaction Associated with Craniosynostosis.

Strabismus in patients with craniosynostosis is common, but surgical correction of strabismus in these patients remains challenging. We report our findings in six patients (four of whom were Korean) with craniosynostosis who underwent strabismus surgery to specifically address V-pattern horizontal strabismus with moderate-to-severe inferior oblique (IO) overaction, using IO myectomy at a single tertiary hospital between 2005 and 2016. We recorded preoperative characteristics including sex, age, type of strabismus, versions grading, refractive error, and visual acuity. The grading of cyclorotation of horizontal rectus muscles by V-pattern categorized using coronal computed tomography imaging. Of the six patients, exodeviation was found in four patients and vertical deviation in two patients in primary position. One patient had both horizontal and vertical strabismus. Available computed tomography imaging showed that V-patterns were category 1 (mild) in two patients, category 2 (moderate) in one patient, and category 3 (severe) in two patients. Complete success was defined as absence of IO overaction any more. Overall complete success rate of IO myectomy was 83.3%. IO myectomy appeared to have some benefits in V-pattern horizontal strabismus with moderate-to-severe IO overaction in patients with craniosynostosis.

Outcomes and Factors Associated with Successful Strabismus Surgery for Abducens Nerve Palsies: A Retrospective Study and Literature Review.

Several studies reported surgical outcomes for abducens nerve palsy, but information on factors that affect treatment success remains lacking. These factors are crucial for developing a treatment plan and providing disease counseling. This study aimed to investigate the outcomes of strabismus surgery for abducens nerve palsy and determine the factors that influence its success, including a review of relevant literature. This retrospective analysis included abducens nerve palsy cases, focusing on surgical interventions and relevant patient data, at the outpatient clinics of Phramongkutklao Hospital from April 1, 2012, to April 30, 2022. A relevant literature review included the surgical success rate and factors that influence surgical outcomes. This study enrolled 32 patients, including 19 with partial and 13 with complete abducens nerve palsy. The overall success rate of strabismus surgery was 78.1%. Trauma was the leading cause of abducens nerve palsy in this population (28.13%). Fisher's exact and Mann-Whitney U-tests revealed that shorter abducens nerve palsy onset and smaller preoperative angle were significantly associated with successful surgical outcomes of strabismus surgery among the groups. In contrast, subgroup analysis revealed that only preoperative smaller angles were significantly associated with good surgical outcomes in horizontal strabismus surgery. However, the vertical rectus muscle transposition group demonstrated no significant factors. The literature review revealed that the success rate of surgery in abducens nerve palsy was 25%-82.6% for horizontal rectus muscle surgery and 46.2%-91% for rectus muscle transposition. The surgical success rate for abducens nerve palsy reached 78.1%, including 78.95% for partial and 76.92% for complete abducens nerve palsy. Notably, a shorter onset preceding surgery and a smaller preoperative angle significantly correlated with successful surgical outcomes one year postoperatively.

Novel superior oblique anterior fiber plication with or without adjustable sliding knot for extorsion

PurposeTo report a novel surgical technique to correct excyclotropia, consisting of a superior oblique anterior fibers plication (SOAFP) with or without a hemihangback anterior knot, allowing access for postoperative adjustment. MethodsA retrospective interventional case series was conducted. Fourteen patients, 21-92 years of age, underwent SOAFP (18 eyes, 14 eyes on adjustable), at the Mayo Clinic in Rochester, Minnesota. SOAFP was the only procedure performed in 12 eyes; in 6 it was performed in conjunction with up to four horizontal rectus muscle recession, resection, and/or plication. Ocular alignment was assessed with prism and alternate cover and double Maddox rod tests; preoperatively, at initial and final (closest to 6-8 weeks) postoperative visits. ResultsPreoperative torsion ranged from 2° to 30° of extorsion (mean, 10.14 ± 7.01). A SOAFP of 2–30 mm (mean, 8.93 ± 5.63) was performed. At the initial postoperative examination, mean intorsional shift was 11.18 ± 7.37, accounting for 1.86° ± 1.04° of correction per millimeter of plication. Three eyes were adjusted after the initial visit to obtain a stronger plication effect targeting of 5° intorsion. At the final visit, 61 ± 23 days postoperatively, mean extorsion was 1.21° ± 2.29°, ranging from 5° of extorsion to 3 of intorsion. Mean final intorsional shift was 9.14 ± 7.53°, accounting for a 1.16 ± 0.50° of correction per millimeter of plication. Of our 14 patients, 13 had improvement in diplopia. ConclusionsIn our study cohort, SOAFP allowed for targeted and easily adjustable correction of extorsion.

Short-Term Morpho-Functional Changes before and after Strabismus Surgery in Children Using Structural Optical Coherence Tomography: A Pilot Study.

To evaluate the immediate alterations in the thickness of the macular ganglion cell-inner plexiform layer (mGCIPL), peripapillary retinal nerve fiber layer (RNFL), inner retinal layer (IRL), and outer retinal layer (ORL) using spectral domain optical coherence tomography (SD-OCT) subsequent to strabismus surgery in pediatric patients diagnosed with horizontal esotropia. Twenty-eight eyes from twenty-one child patients who had undergone uncomplicated horizontal rectus muscle surgery due to strabismus were included. Measurements of RNFL, mGCL-IPL, IRL, and ORL using structural OCT were conducted both before the surgery and one month after the surgical procedure. Importantly, a control group comprising 14 healthy eyes, matched for age and significant refractive error (<3.00 diopters), was included in the current analysis. Our analysis indicated no significant disparity before and after surgery in terms of best-corrected visual acuity (BCVA), RNFL, IRL, and ORL. Conversely, concerning the macular ganglion cell layer-inner plexiform layer analysis, a substantial increase in mGCL-IPL was observed following the surgical intervention. The mean mGCL-IPL measured 60.8 ± 9.2 μm at baseline and 66.1 ± 13.2 μm one month after the surgery (p = 0.026). Notably, comparison between the strabismus group at baseline and the healthy group revealed a significant reduction in mGCL-IPL in the strabismus group (60.8 ± 9.2) compared to the healthy control group (68.3 ± 7.2; p = 0.014). Following strabismus surgery, our observations pointed towards a thickening of the mGCL-IPL layer, which is likely attributable to transient local inflammation. Additionally, we identified a significant differentiation in the mGCL-IPL complex between the pediatric patient group with strabismus and the control group.

Investigation of alterations in retrobulbar hemodynamics and their correlation with choroidal thickness after strabismus surgery.

To evaluate the changes in retrobulbar circulation after strabismus surgery and to assess the relationship of these changes with choroidal thickness (CT). This prospective study included 26 eyes of 26 patients who underwent strabismus surgery and 15 eyes of 15 healthy individuals as control group. The patients who had single horizontal muscle surgery were included in Group 1 (n = 14); and those who had surgery on both horizontal muscles were included in Group 2 (n = 12). Peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI) and pulsatility index (PI) of ophthalmic artery (OA), posterior ciliary artery (PCA), and central retinal artery (CRA) were measured using Color Doppler Ultrasonography. Subfoveal CT was measured via Optical Coherence Tomography. All measurements were obtained preoperatively, at 1st week and 1st month after surgery. There were no differences regarding preoperative blood flow velocity parameters among the groups. OA RI increased significantly at 1st week and 1st month after surgery in Group 1 and 2 (P = 0.029 and P = 0.045, respectively). There was a significant increase in PCA PSV at 1st week in Group 1 (P = 0.002). There was no difference between the mean preoperative and postoperative CT among the 3 groups. A negative correlation between the percentage changes of CT and CRA EDV was found in Group 2 (P = 0.011). Single and double horizontal rectus muscle surgery have a measurable effect on retrobulbar hemodynamics but these changes do not correlate with CT.

Uncover the Hidden Veils: Ophthalmoplegia in Breast Cancer

Abstract&#x0D; Introduction : Breast cancer can metastasize to many sites, but the orbit is an infrequent location. Orbital metastases represent 1%–13% of all orbital tumors, and the prognosis is rather poor. We reported a case of orbital metastases of breast cancer that led to findings of other sites involvement.&#x0D; Case Illustration : A 50-year-old female presented with an inward squint and double vision for 9 months before admission. Esotropia, abduction, and elevation deficits in both eyes were observed. The visual acuity of both eyes was 6/6. Orbital MRI revealed an intraconal irregular lesion near the medial rectus muscle, which was hyperintense with contrast and thickened medial rectus muscles of both eyes. She underwent lumpectomy of breast mass two years before admission and no follow-up after surgery. Histopathology showed invasive lobular carcinoma (ILC). We referred her to hematologist- oncologist to have workup on metastases and treatment. Lung and extensive bone metastases were discovered. She was diagnosed with metastatic breast cancer (stage IV) and treated with hormonal therapy and bisphosphonates. On 3-month follow-up, diplopia and gaze limitations persist.&#x0D; Discussion : Diplopia and motility disturbances are the most common symptoms and signs of orbital metastases, including extraocular muscle involvement. The horizontal rectus muscles are more commonly involved. ILC is more frequent histological subtype involving orbital as the orbits are rich in fat and may attract disseminated ILC cells.&#x0D; Conclusion : Ocular symptoms in patients with a history of breast cancer should always be investigated for metastatic disease. A multidisciplinary approach is mandatory to achieve the best therapeutic management and long-term surveillance.

SURGICAL OUTCOME OF THREE MUSCLES SURGERY IN ONE SINGLE PROCEDURE OF LARGE-ANGLE EXOTROPIA: A CASE REPORT

Introduction : The management of large-angle horizontal strabismus poses special difficulties. Literature has outlined large-angle strabismus in a variety of ways. A threshold of 40 to 60 PD has been employed to determine large-angle strabismus.&#x0D; Case Illustration : A 19-year-old male with complaint of right eye that had been crossed outward since he was 12 years old. There was 90 prism diopter exotropia in near, distance, upgaze, and downgaze. The patient underwent bilateral lateral rectus recession of 10 mm and unilateral medial rectus resection of 6.5 mm in the right eye. Post-operative outcome revealed orthophoria without any misalignment of prism diopter examination in 1 day, one week, and two weeks follow-up.&#x0D; Discussion : When the deviation exceeds 50 prism diopter, there is no established consensus regarding the number and quantity of extraocular rectus muscles for surgery. The lack of uniform criteria and suggested surgical dosage is the greatest obstacle in using three muscles surgery. In this case, we used surgical dose according to Kenneth Wright exotropia binocular surgery table. We performed bilateral rectus lateral recession of 10 mm and a right rectus medial resection of 6.5 mm. This surgical dose gives good outcome. Moreover, this option can leave one horizontal rectus muscle unharmed.&#x0D; Conclusion : Determination of the surgical dose is essential in the management of large-angle exotropia. Appropriate surgical dose results in excellent outcomes with low risk of residual deviation.

Acquired comitant esotropias – comparison of surgical outcomes of accommodative vs non-accommodative types

ABSTRACT Purpose: To compare the motor and sensory outcomes of strabismus surgery and the factors affecting surgical success in acquired acute non-accomodative esotropia (ANAET) and partially accommodative refractive esotropia (pARET). Methods: A retrospective chart review of patients with ANAET and pARET who underwent unilateral or bilateral horizontal rectus muscle surgery between January 2020 and December 2021 was conducted. Patients with postoperative follow-up of at least six weeks were included. Patients with pattern deviation, lateral incomitance, and near-distance disparity were excluded. Motor success was defined as a postoperative deviation within eight prism diopters of orthophoria. Sensory success was defined as presence of binocular single vision (BSV) for both distance and near (Worth four dot test). The effect of factors like age at onset, age at surgery, amblyopia before surgery, duration of squint before treatment, presence or absence and magnitude of vertical deviation, preoperative angle of deviation, and spherical equivalent on the motor and sensory success in each group were analyzed and compared. Results: 38 patients with ANAET and 33 patients with pARET were included. The mean age of onset of esotropia was 8.55 ± 4.65 years and 4.39 ± 2.27 years (p < .001) and the mean age at surgery was 10.62 ± 4.99 years and 7.89 ± 2.84 years (p = .006) in the ANAET and the pARET group respectively. The mean duration of the final follow-up was 38.51 weeks in the ANAET and 48.68 weeks in the pARET group (p = .089). Patients were successfully aligned for both distance and near in 81.5% of patients in the ANAET and 78.9% of patients in the pARET group at the final follow-up (p. 0.775). A BSV for both distance and near at the final follow-up was seen in 81.2% vs 66.6% of patients in the ANAET and the pARET group respectively (p = .25). A good near stereoacuity (<120 arcsecs) was seen in 60.6% and 41.9% of the ANAET and the pARET groups respectively (p = .175). The percentage of patients in the ANAET group who had orthophoria, any esodeviation, and any exodeviation for distance at the final follow-up was 63.1%, 34.2% and, 2.6%. The percentage of patients in the pARET group in similar categories was 36.3%, 42.4% and, 21.2%. None of the demographic and preoperative factors were found to affect the surgical outcomes in the two groups. Conclusions: The motor and sensory outcomes were similar in the two groups. A higher proportion of ANAET patients remained orthophoric during the follow-up. The patients in the pARET group showed a tendency toward exodrift.

Assessment of retinal and choroidal microcirculation after unilateral recession–resection surgery for horizontal strabismus by swept-source optical coherence tomography angiography

This study explored the possible hemodynamic changes of the retina and choroid after horizontal strabismus surgery using swept-source optical coherence tomography angiography (SS-OCTA). 32 eyes of 32 patients who underwent unilateral horizontal rectus muscle recession–resection surgery were included. SS-OCTA examinations were performed preoperatively and one week postoperatively. Several OCTA measurements were used, including vessel density (VD) of the superficial vascular complex (SVC), VD of the deep vascular complex (DVC), VD of the choriocapillaris (CC), choroidal vascular index (CVI) and choroidal thickness (CT). No significant change in VD of SVC, DVC, and CC was observed whereas CT increased significantly with CVI unchanged. Recession–resection surgery for horizontal strabismus seemed not to significantly influence the microcirculation of the retina and CC in the early postoperative period. However, choroidal thickening happened with a constant CVI probably due to the postoperative inflammation. Further studies are needed to investigate the long-term effects of unilateral recession–resection surgery for horizontal strabismus on the microcirculation of the retina and choroid.

Decrease of over-elevation in adduction after surgery of medial rectus muscles in partially refractive accommodative esotropia.

The course of over-elevation in adduction after strabismus surgery has been evaluated in a small number of research in the literature, we believe our study is the first to report the results in a specific group of esotropia (ET) patients. To report the course of postoperative over-elevation in adduction in patients who underwent surgery for horizontal deviation on the medial recti in partially accommodative ET. The medical charts of patients who had partially accommodative ET with over-elevation in adduction were reviewed retrospectively. A scale from -4 to +4 was used to grade the oblique muscle function. Among these, 17 patients who were operated solely on the horizontal rectus muscles were identified. The primary outcome measure was the degree of improvement in over-elevation in adduction after medial rectus surgery. Nine (52.9%) of the 17 patients (mean age: 5.18 ± 2.24 months) were males and 8 (47.1%) were females. The mean follow-up period was 17.06 ± 15.32 months. Overall, 15 patients (88.2%) achieved surgical success. The mean inferior oblique overaction was found 1.44 ± 0.56 preoperatively and the final postoperative mean inferior oblique overaction was 0.53 ± 0.51 (P = 0.001). Postoperative over-elevation in adduction after 3 months was significantly decreased compared to the preoperative value (P = 0.003, P = 0.001, P = 0.001 at 3rd and 6th months and final visits respectively). Over-elevation in adduction accompanying partially refractive accommodative ET seems to regress after medial rectus weakening surgery. This finding should be considered in the presurgical evaluation of these patients.

The long-term outcomes of the Anderson-Kestenbaum procedure.

Nystagmus is an involuntary, conjugated, rhythmic movement of the eye that can be idiopathic or secondary to ocular or neurologic pathologies. Patients with nystagmus often have a position of gaze in which their symptoms are dampened or absent, referred to as the "null zone." The Anderson-Kestenbaum procedure is a bilateral recess-resect procedure of the four horizontal rectus muscles which aims to bring the null position into the primary gaze. This study aims to further elucidate long-term outcomes and factors associated with optimal postoperative outcomes. Patients with a diagnosis of nystagmus and a surgical code for strabismus between June 1990 and August 2017 were considered for inclusion in the study. Patients were included if they had undergone the Anderson-Kestenbaum procedure and had follow-up lasting at least 24 months post-operatively. Data collected included demographic information, characteristics of the nystagmus, underlying etiology of nystagmus, and pre-and post-operative measurements. 25 patients were included. At their last recorded follow-up, 44% of patients achieved an optimal surgical outcome -an abnormal head position of 10 degrees or less. 88% of patients showed an overall improvement in their head posture at the last follow-up. The absence of an abnormal head position at the visit closest to 24 months post-operatively was found to be significantly associated with the lack of a significant head position at the last follow-up visit. Optimal surgical outcomes were not significantly associated with the underlying diagnosis, the direction of the abnormal head position, or the type of nystagmus. The relatively long follow-up of this cohort allows this study to further elucidate the long-term outcomes of the Anderson-Kestenbaum procedure. Overall, our results suggest that although improvement in head position post-operatively is likely, it is still expected that many patients will have a residual abnormal head position after the procedure. The results of this study are helpful in counseling patients, especially knowing that if they do not have a significant head position at 24 months follow-up, they are unlikely to develop one. However, due to the small sample size, larger cohorts and more standardized follow-up may provide further insight into the procedure's outcomes.

Changes in retinal and choroidal blood flow after one or two horizontal rectus muscle surgeries by optical coherence tomography angiography

Purpose To evaluate the retinal and choroidal microvasculature after one or two horizontal rectus muscle surgeries in strabismus patients using swept-source optical coherence tomography angiography (SS-OCTA). Methods 30 eyes of 26 patients who underwent horizontal rectus muscle surgery were included in this study. Group A, A’ and Group B , B’ respectively consisted preoperative and postoperative measurements of patients who underwent one or two horizontal rectus muscle surgeries. We analyzed the vessel density (VD) of the superficial vascular complex (SVC), the deep vascular complex (DVC), the choriocapillary layer (CC), choroidal vascular index (CVI), choroidal thickness (T-Ch) and retinal nerve fiber layer thickness (T-RNFL) preoperatively, and one week postoperatively. Results Only in the nasal sector of the perifoveal zone, the VD in SVC demonstrated a significant increase in Group A’ (p = 0.027). There was a statistically significant difference in the VD changes of SVC between Group A and Group B (p = 0.043). The VD in DVC did not change significantly in the whole macular compared with the preoperative. Moreover, in both Group A’ and Group B’, the VD in CC showed a reduction in a single sector of the parafoveal area (p < 0.05). Group A’ have increased CVI in the nasal sector of the perifoveal region (p = 0.008). In addition, the T-Ch increase in the perifoveal region was more significant in Group B’ than in Group A’ (p < 0.05). Group A’ showed statistically significant decreases in T-RNFL in the foveal and parafoveal regions (p < 0.05). Conclusion This study revealed that the increase in choroidal thickness was more significant after two rectus muscle surgery. In addition, there were microvascular changes in sectional macular regions after strabismus surgery. OCTA is an excellent way to study the impact of strabismus surgery on the macular structure and blood flow.

Comparison of anterior segment optical coherence tomography and ultrasound biomicroscopy in localizing horizontal rectus muscle insertions.

To evaluate the viability and precision of measuring the distance from the limbus to extraocular muscle insertion using anterior segment optical coherence tomography (AS-OCT) and panoramic ultrasound biomicroscopy (UBM) before and after strabismus surgery. We recruited primary strabismus patients and measured the limbus-insertion distance by AS-OCT and UBM preoperatively, 2 weeks, and 1, 3, and 6 months postoperatively. Values were also measured using callipers intraoperatively before and after the planned procedures. Preoperative AS-OCT and UBM values were compared to intraoperative calliper measurements as the gold standard. Postoperative AS-OCT and UBM values were compared to the new postoperative limbus-insertion distance. The limit of agreement deemed clinically acceptable was defined as 1 mm. A total of 85 horizontal muscles of 40 patients, including 48 lateral rectus muscles and 37 medial rectus muscles, were analysed. Primary muscles could be successfully detected by AS-OCT (95%) and UBM (100%). At 2 weeks and 1, 3, and 6 months postoperatively, the new rectus muscle attachment site detection rate by AS-OCT was 6%, 32%, 80%, and 89%, respectively, and that by UBM was 24%, 60%, 85%, and 93%, respectively. The Bland-Altman plots revealed better consistency in pairs of AS-OCT, UBM, and calliper measurements of primary muscles than postoperative muscles. For primary muscles, 89% of AS-OCT measurements fell within the permissible range of surgical measurements (1 mm), but this dropped to 67% at 6 months postoperatively (P < 0.001). The accuracy of UBM measurements of primary muscles was 81%, and this decreased to 59% at 6 months postoperatively (P = 0.001). AS-OCT and UBM performed well in terms of imaging primary horizontal rectus muscles, but showed decreased accuracy and reproducibility in postoperative muscle measures.

Magnetic Resonance Imaging Findings in Patients With Duane Retraction Syndrome.

Duane retraction syndrome (DRS) is known to relate to the absence of the abducens nucleus, with abnormal innervation of the lateral rectus (LR) muscle by branchesof the oculomotor nerve (CN III). The purposes of this study were to investigate the morphological characteristics of the oculomotor nerve (CN III), the abducens nerve (CN VI), and the extraocular muscles in patients with clinically diagnosed Duane retraction syndrome (DRS) using MRI. In addition, we assessed the association between ocular motility, horizontal rectus muscle volumes, and CN III/VI in patients with Duane retraction syndrome (DRS). The study comprised 20 orthotropic control subjects (40 eyes) and 42 patients with Duane syndrome (48 eyes), including 20 patients with DRS Type I (24 eyes), 5 patients with DRS Type II (6 eyes), and 17 patients with DRS Type III (18 eyes). Three-dimensional (3D) T1/2 images of the brainstem and orbit were obtained to visualize the cranial nerves, especially the abducens (VI) and oculomotor (III) nerves, as well as extraocular muscles. Based on the clinical classification, among 42 patients, MRI showed that the abducens nerves (CN VI) on the affected side were absent in 24 of 24 eyes (100%; 20 patients) with Type I DRS and in 16 of 18 eyes (88%; 16 patients) with Type III DRS. However, CN VI was observed in 6 of 6 eyes (100%; 5 patients) with Type II DRS and in 2 of 18 eyes (11%) with Type III DRS. CN III was observed in all patients. The oculomotor nerves on the affected side were thicker than those on the nonaffected contralateral side in DRS Type I ( P < 0.05) and Type III ( P < 0.05), but not in DRS Type II. Smaller LR and larger MR volumes were shown in the affected eye than that in the nonaffected eye in DRS Types I and III. Based on the presence or absence of CN VI, there was a tendency for thicker oculomotor nerves in the affected eye than in the nonaffected eye in the absence groups ( P < 0.05). However, no significant difference was found in the present group. In the CN VI absence groups, similar results were found in the affected eyes than in the nonaffected eyes as in DRS Types I and III. In addition, the presence of CN VI was correlated with better abduction ( P = 0.008). The LR and MR volumes have positive correlations with the oculomotor nerve diameter in the affected eye. However, there was no correlation between the range of adduction/abduction and the LR/MR ratio in patients with or without an abducens nerve. Different types of DRS have different characteristic appearances of CN VI and CN III on MRI. Horizontal rectus muscles have morphological changes to adapt to dysinnervation of CN VI and aberrant innervation of CN III. Thus, these neuroimaging findings may provide a new diagnostic criterion for the classification of DRS, improving the comprehension of the physiopathogenics of this disease.

Inferior displacement of the lateral rectus muscle insertion in exotropia with mild V-pattern or vertical deviation.

To describe clinical features and intraoperative findings of the patients with exotropia who presented mild V-pattern or vertical deviation, and to investigate the surgical outcomes of anatomical relocation of inferiorly displaced lateral rectus (LR) muscle insertion. Detailed ophthalmological evaluations were obtained in 42 consecutive patients, and the horizontal rectus muscle insertions were detected intraoperatively. The displaced insertion of LR muscle was corrected accompanied with classic recession-resection procedure. The inferiorly displaced LR muscle insertions were detected in 19 patients (Group A), while the remaining 23 patients (Group B) had normal insertions. The mean distance of displaced insertion from the normal position was 2.92 ± 1.05 mm (range: 1.0-4.0). Mild V-pattern was more common in Group A (78.9%, 15/19) than Group B (47.8%, 11/23), and the magnitude of V-pattern in Group A (6.16 ± 3.91 PD) was also greater than Group B (3.43 ± 3.92 PD). The fundus extorsions of the affected eyes (9.68 ± 4.77 °) were greater than the contralateral eyes (5.91 ± 5.82 °) in Group A. At the 2 months follow-up, mild V-pattern and mild vertical deviation were corrected by upward transposition. The significant correlations were identified between the pre-operative misalignments and the amounts of misalignments correction. Nearly half of the cases with mild V-pattern or vertical deviation resulted from the inferiorly displaced LR muscle insertion, so the intraoperative exploration of the LR muscle insertion is strongly suggested. Upward transposition may effectively correct both the mild V-pattern and vertical deviation.