Study 3: Anterior segment optical coherence tomography-guided surgical approach in slipped medial rectus muscle

Purpose: To discuss the novel swept?source anterior segment optical coherence tomography (SS?ASOCT)?guided surgical approach in slipped medial rectus muscles. Methods: Prospectively (between February 2020 and July 2022), six patients with a clinical suspicion of slipped medial rectus muscle were recruited. After complete ophthalmic and orthoptic evaluation, the missing medial rectus muscle is screened using Anterior Segment Optical Coherence Tomography (ASOCT). In presence of a traceable muscle, its morphology, depth, and distance from a fixed anatomical landmarks were noted; in its absence, the status of other recti was noted. Intraoperatively, the features were confirmed and the intended intervention was performed. Results: The mean age of six patients was 25.66 ± 9.72 years, two with surgical trauma and four with penetrating trauma (66.66%). In five patients, the ASOCT traced the slipped medial rectus muscle successfully (83.33%); intraoperatively, the same was confirmed (within 1–2 millimeters) with favorable outcomes. ASOCT made a significant contribution in all subjects by reducing the number of interventions and muscle surgeries. Conclusions: In eyes with slipped medial rectus muscle, especially those which are within a finite distance from the angle can be traced using ASOCT. This approach impacts the outcomes in many ways

Rectus muscle pseudo-adherence syndrome

Purpose: To describe a clinical entity called “rectus muscle pseudo?adherence syndrome” following buckling surgery. Methods: A retrospective data review was undertaken to analyze the clinical profile of strabismus patients who had developed it following buckling surgery. Between 2017 and 2021, a total of 14 patients were identified. The demography, surgical details, and intraoperative challenges were reviewed. Results: The average age of the 14 patients was 21.71 ± 5.23 years. The mean pre?op deviation was 42.35 ± 14.35 prism diopters (PD) of exotropia, and the mean post?op deviation was 8.25 ± 4.88 PD of residual exotropia at 26.16 ± 19.53 months follow?up. Intraoperatively, in the absence of a buckle, the thinned?out rectus adhered to the underlying sclera with much denser adhesions along its margins. When there was a buckle, the rectus muscle adhered to the outer surface of the buckle again, but less densely, with marginal union into the surrounding tenons. In both scenarios, due to the absence of protective muscle coverings, the rectus muscles were naturally adsorbed onto the immediately available surface in the presence of active healing by the tenons. Conclusion: While correcting ocular deviations following buckling surgery, a false sense of an absent, slipped, or thinned?out rectus muscle is very much possible. This is due to active healing of the muscle with the surrounding sclera or the buckle in a single layer of tenons. This is the rectus muscle pseudo?adherence syndrome, where the culprit is the healing process and not the muscle

Changes in the Effects of Bilateral Lateral Rectus Muscle Recession According to Preoperative Angle Deviation

PURPOSE: To investigate how the effect of bilateral rectus muscle recession changed by analyzing the effect/dose ratio of surgery according to the preoperative angle deviation.METHODS: We retrospectively studied the medical records of patients from January 2007 to March 2014 who underwent bilateral lateral rectus muscle recession and who visited our hospital for at least 2 years after surgery. We classified the patients into two groups: the preoperative large angle deviation group (35 prism diopters [PD] or more) and the small angle deviation group (20 PD or less). We observed exodrift patterns by measuring distant and near angle deviation according to the preoperative and postoperative times. The effect/dose ratio of recession was calculated at each visit. Surgical success was defined as an alignment between 10 PD of exodeviation and 5 PD of esodeviation, both at distance and at near.RESULTS: Among 165 patients, 84 patients were in the large angle deviation group and 81 patients were in the small angle deviation group. Preoperative angle deviation of the large angle deviation group was 39.34 ± 5.13 PD (range: 35–55 PD) and the small angle deviation group was 19.49 ± 1.62 PD (range: 18-20 PD) (p < 0.001). At postoperative 1 day, the alignments of eyes of the two groups were −8.32 ± 9.31 PD and −13.11 ± 6.94 PD; p < 0.001, respectively. At the date of the final follow-up, the alignments of eyes of the two groups were 4.63 ± 8.94 PD and 1.22 ± 8.01 PD; p = 0.011, respectively, and the effect/dose ratios were 2.25 ± 0.62 PD/mm and 1.94 ± 0.78 PD/mm, respectively, which meant that the effect of correction for the large angle deviation group was larger than that of the small angle deviation group (p = 0.005). Both groups showed postoperative exodrift patterns and similar success rates (75.0% and 80.2%, respectively), which showed no significant difference (p = 0.268).CONCLUSIONS: The small angle deviation group showed a larger effect of correction and high exodrift pattern at the postoperative initial time and the large angle deviation group showed a smaller effect of correction and low exodrift pattern at the postoperative initial time. The preoperative angles of deviation and the operative success rates were not related.

Changes in Corneal Topography and Clinical Refraction Following Horizontal Rectus Muscle Surgery

Objectives@#Refractive changes have been studied after muscle surgery in literature but most results are inconsistent. It has been postulated that changes in corneal tension after muscle surgery may cause a change in corneal curvature resulting in the change in refraction postoperatively. This study investigated changes in corneal topography and clinical refraction after horizontal rectus muscle surgery.@*Methods@#Twenty-one eyes of 13 patients underwent horizontal rectus muscle surgery via limbal approach. Manifest refraction, cycloplegic refraction, and corneal topography were measured preoperatively, and postoperatively at day 1 and weeks 1, 2, 4 and 8. The proportion of subjects with at least 0.5 D change from preoperative measurements and the proportion of subjects that needed new prescription postoperative were also computed. Analysis of the results were done using the Friedman test to identify significant differences among measurements at different time periods with post-hoc analysis utilized to identify specific time periods with significant changes from preoperative measurements.@*Results@#Mean corneal keratometry, horizontal, vertical, and oblique astigmatism, obtained topographically showed no significant difference from preoperative measurements. The statistically significant difference in corneal astigmatism in the recession group at day 1, week 4 and week 8 postoperatively was not confirmed when converted to power vectors in both vertical/horizontal (J0) and oblique (J45) astigmatism. Clinical refraction showed a transient myopic shift in spherical equivalent, statistically significant only on postoperative day 1 in the recession group. There was no statistically significant difference in clinical astigmatism. There was ≥ 0.5 D change in spherical equivalent in 60% in both study groups by the end of follow-up. The shift in J0 was more than 10% in the recession group. More than fifty percent (52.4%) needed new prescription for glasses.@*Conclusion@#No statistically significant change in corneal topography and clinical refraction following horizontal rectus muscle surgery were found. Patients should still be refracted at least 2 weeks postoperatively to check if there is a need for change in prescription glasses to improve alignment and/or improve vision.

Clinical observation of external rectus muscle amputation in the treatment of divergence insufficiency / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To observe the clinical effect of external rectus muscle amputation in the treatment of divergence insufficiency. <p>METHODS: A retrospective analysis of 37 cases of insufficiency in our hospital from February 2011 to October 2017. The clinical manifestations were hyperopic esotropia with ipsilateral diplopia, myopia implicit esotropia without diplopia, and the monocular and binocular movements were normal. Preoperative refractive, strabismus, near stereopsis, negative fusion force examination, and then single or double external rectus muscle surgery.<p>RESULTS: Double vision disappeared after all cases, and there was no recurrence in diplopia after one year of follow-up. The preoperative long-term internal strabismus was +15△-+28△, with an average of 18.4△±5.7△, the near-internal strabismus was +5△-+16△, the average was 10.3△±3.6△, The difference value of long distance and short distance strabismus was 8.1△±2.3△; one week after surgery, the distance strabismus was -5.4△±1.5△, the near-distance squint was -7.2△±1.6△, the difference value was 1.8△±0.6△; the one year postoperative strabismus was -1.9△±1.2△, the close squint was -3.4△±1.4△, the difference value was 1.5△±0.8△. The long-distance strabismus one week after operation and one year after operation was significantly lower than that before operation(<i>P</i><0.05). The difference of distance and strabismus between one week and one year after operation was statistically significant. Preoperative the difference between near and far squint one week and one year after operation was statistically significant(<i>P</i><0.05). The difference was statistically significant between the preoperative and postoperative one week. The difference was statistically significant 1 week after surgery and 1 year after surgery. The long-distance negative fusion force before surgery was 3△-9△, with an average of 5.1△±1.8△, and the near-negative fusion force was 15△-24△, with an average of 19.4△±3.2△. The long-near negative fusion force was 10.1△±3.3△, 19.7△±4.1△ at 1wk after operation, and the long-distance negative fusion force was 11.2△±3.6△, 20.2△±4.8△ for one year after operation. There was a statistically significant difference between the patients with preoperative and one week postoperative negative fusion(<i>q</i>=4.551, <i>P</i>=0.013). There was no significant difference between the one week and one year after surgery(<i>q</i>=0.713, <i>P</i>=0.115).There was no significant difference in the patients' brachytherapy before and after one week and one year after operation(<i>P</i>>0.05).<p>CONCLUSION: Divergence insufficiency of external rectus muscle surgery can effectively reduce the difference of long-distance strabismus after surgery, eliminate the symptoms of diplopia in patients, and improve the near stereoscopic sharpness and long-distance negative fusion force.

The study of skeletal muscle relaxant property of pheniramine maleate in acetylcholine induced contractions on isolated frog rectus muscle

Background: A muscle relaxant is a drug which affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasm, pain and hyperreflexia. Skeletal muscle relaxants are heterogeneous group of medications that refer to 2 major therapeutic groups: neuromuscular blockers and spasmolytics. This study is carried out to evaluate the skeletal muscle property of Pheniramine maleate in Acetylcholine Induced Contractions on Isolated Frog Rectus Muscle.Methods: There are various screening techniques available to assess the muscle relaxant property of a drug. For initial screening, frog rectus muscle is used. Here frogs are divided into 4 different groups. Each group contains 6 isolated frog rectus muscles. The experiment is carried out by adding 100?g, 200?g, 400?g and 800?g of pheniramine maleate with 80?g of acetylcholine to the organ bath and response is recorded by kymograph.Results: Pheniramine maleate in various doses like 100?g, 200?g, 400?g and 800?g with 80?g of acetylcholine 100?g showed the maximum contractions of frog rectus muscle in kymograph. At all the doses of Pheniramine maleate, it showed a significant effect of skeletal muscle relaxant property.Conclusions: In conclusion with work done by using pheniramine maleate in different doses along with 80?g of acetylcholine. Pheniramine maleate showed the maximum skeletal muscle relaxant property on frog rectus muscle at 800?g dose.

Mitral Valve Repair after Sternal Turnover with a Rectus Muscular Pedicle / 日本心臓血管外科学会雑誌

<p>A 58-year old man without Marfan syndrome was referred to our hospital for congestive heart failure due to severe mitral regurgitation. He had undergone sternal turnover with a rectus muscular pedicle for pectus excavatum 36 years previously. We were able to perform mitral valve repair via median sternotomy using a usual sternal retractor. There was no adhesion in the pericardium and the exposure of the mitral valve was excellent. We closed the chest in ordinary fashion without any problems in the fixation of the sternum or costal cartilage. There were no complications such as flail chest or respiratory failure.</p>

Comparison of Exodrift between Natural Group and Postoperative Group in Intermittent Exotropia Patients

PURPOSE: To compare the exodrift between unilateral lateral rectus (ULR) recession and observation groups in moderate angle intermittent exotropia (IXT). METHODS: A retrospective study was performed in 769 patients who were diagnosed with IXT from 2005 to 2015. Seventy-six patients were enrolled in this study that presented with IXT of 20 to 25 prism diopters (PD) on their first visit and were observed for more than 6 months without or after operation. The observation group (group 1) was composed of 29 patients who had regular examination without operation. The surgery group (group 2) was composed of 47 patients with ULR recession that were observed for deviation changes since surgery. RESULTS: The mean age was 71.8 ± 22.0 months at first visit in group 1 and 91.1 ± 18.9 months before surgery in group 2 (p < 0.01). The distant exodeviation was 22.9 ± 2.5 PD at first visit in group 1 and 22.9 ± 2.4 PD before surgery in group 2 (p = 0.89). During follow-up, mean exodrift was 0.6 ± 9.0 PD in group 1 and 10.0 ± 7.4 PD in group 2 (p < 0.01). Exodrift up to postoperative 6 months in group 2 was 3.2 ± 4.0 PD and exodrift from postoperative 6 months to 2 years in group 2 was 7.1 ± 6.9 PD. More exodrift was noticed after post-operative 6 months (p = 0.04). CONCLUSIONS: Comparing the exodrift between the groups in moderate angle IXT, patients in the observation group showed less exodrift. Patients who had a ULR recession presented more exodrift after postoperative 6 months. Even though they were orthotropic at postoperative 6 months when the operation was thought to be stabilized, an increase in exodrift after postoperative 6 months could not be excluded.

A Case of Immediate Surgical Repair in Traumatic Isolated Inferior Rectus Muscle Rupture

PURPOSE: We report a case of infraduction limitation improvement and orthotropia at primary position in a patient with traumatic isolated inferior rectus muscle rupture after immediate repair surgery of the ruptured muscle. CASE SUMMARY: A 47-year-old man came to our emergency department complaining of right eyelid contusion and conjunctival laceration after trauma due to the metal part of a high pressure hose. Right hypertropia of 20 prism diopters was observed at primary gaze and right hypertropia of 30 prism diopters was observed at down gaze. The right eye showed a -4 infraduction limitation. We sutured the distal part of the ruptured inferior rectus muscle with surrounding tissue, including the Tenon's capsule and the part of the muscle stump, to its original insertion. Orthotropia at primary position and 8-prism-diopters of right hypertropia on down gaze was observed one day after surgery. At 40 days after surgery, the patient had orthotropia at primary position and 4-prism-diopter right hypertropia on down gaze. Infraduction limitation of the right eye improved to -1. CONCLUSIONS: Immediate repair of complete traumatic isolated inferior rectus muscle rupture can correct the limitation of extraocular movement and achieve orthotropia at primary position.

The Clinical Observation of Hydroxyapatite Prosthesis Implantation through Lateral Rhinotomy Approach on the Orbit / 昆明医科大学学报

Objective To observe exposure rates of hydroxyapatite artificial eye by comparing hydroxyapatite prosthesis implantation through lateral rhinotomy approach on the orbit and traditional sclera shell hydroxyapatite prosthesis implantation.Methods After eye content was enucleated at postoperative stage I,75 patients received hydroxyapatite prosthesis implantation,among which 26 received direct sclera shell prosthesis implantation (group A) and 49 received implantation through lateral rhinotomy approach on the orbit (group B).During postoperative follow-up from 6 months to 5 years,exposure rates of hydroxyapatite artificial eye under two operation ways were observed and analyzed by x 2 test.Results According to observation,8 cases were exposed in the group A,and 2 cases were repaired by fascia and conjunctival repair.Six cases were healed by prosthesis and sclera replacement.In group B,only 1 case was exposed slightly and recovered after simple conjunctival repair.The incidence of the eye exposure rate using two kinds of operation methods in group A is significantly higher than that in group B (P ＜ 0.05) The difference was statistically significant.Conclusion The exposure of hydroxyapatite artificial eye can be effectively avoided and postoperative complications can be reduced by hydroxyapatite prosthesis implantation through lateral rhinotomy approach on the orbit among patients with severe eyeball ruptures,painful eyeballs of no light perception and atrophy eyes.

A rare cause of acute abdomen-Spontaneous rectus sheath hematoma

Spontaneous rectus sheath hematoma (SRSH) is a rare entity that mimics acute abdomen. Rectus sheath hematoma is the accumulation of blood in rectus sheath due to muscle or epigastric vessel injury. However, SRSH without a trauma or anticoagulation is rare. It frequently mimics acute abdomen and it may lead to misdiagnosis and unnecessary laparotomy. In this article, we described two cases of SRSH with their diagnostic and therapeutic strategy. Both of our patients in report were neither consumed antiplatelet nor coagulopathy. They both had abdominal muscle straining before their symptoms pre-sentation. We hypothesized that the SRSH may be induced by rectus muscle injury secondary to inappropriate straining or posture. To diagnose SRSH, clinical findings are important but radiologic imaging such as computed tomography, can be diagnostic. In expanding SRSH, percutaneous arterial embolization of epigastric artery is useful to secure the bleeding. If embolization is not feasible, surgical exploration hemostasis is curative. In non-expanding SRSH, it can be managed nonoperatively. SRSH is an important initial differential for acute abdomen. Radiologic imaging helps in diagnosis. Stable SRSH can be managed conservatively with good outcome.

A rare cause of acute abdomen – Spontaneous rectus sheath hematoma

Spontaneous rectus sheath hematoma (SRSH) is a rare entity that mimics acute abdomen. Rectus sheath hematoma is the accumulation of blood in rectus sheath due to muscle or epigastric vessel injury. However, SRSH without a trauma or anticoagulation is rare. It frequently mimics acute abdomen and it may lead to misdiagnosis and unnecessary laparotomy. In this article, we described two cases of SRSH with their diagnostic and therapeutic strategy. Both of our patients in report were neither consumed antiplatelet nor coagulopathy. They both had abdominal muscle straining before their symptoms presentation. We hypothesized that the SRSH may be induced by rectus muscle injury secondary to inappropriate straining or posture. To diagnose SRSH, clinical findings are important but radiologic imaging such as computed tomography, can be diagnostic. In expanding SRSH, percutaneous arterial embolization of epigastric artery is useful to secure the bleeding. If embolization is not feasible, surgical exploration hemostasis is curative. In non-expanding SRSH, it can be managed nonoperatively. SRSH is an important initial differential for acute abdomen. Radiologic imaging helps in diagnosis. Stable SRSH can be managed conservatively with good outcome.

Unilateral Lateral Rectus Muscle Advancement Surgery Based on One-fourth of the Angle of Consecutive Esotropia

PURPOSE: To evaluate the efficacy of unilateral lateral rectus muscle advancement surgery based on one-fourth of the angle of consecutive esotropia within 25 prism diopters (PD) which occurred after bilateral lateral rectus muscle recession for intermittent exotropia. METHODS: Medical records of 11 patients who underwent unilateral lateral rectus muscle advancement for consecutive esotropia from 2011 to 2014 and who were observed for at least 6 months after surgery were retrospectively reviewed. The change in the angle of deviation before and after consecutive esotropia surgery, success rate, and surgical effect were evaluated. RESULTS: Preoperative esodeviation was -19.6 ± 4.7 PD at distance and -16.5 ± 7.4 PD at near. Unilateral lateral rectus muscle advancement surgeries were performed based on one-fourth of the angle of consecutive esotropia and the mean surgical amount was 4.8 ± 1.1 mm. Of the total 11 patients, 10 patients (91%) recovered to orthotropia or exodeviation within 8 PD. One patient had a recurrence of esotropia at postoperative 3 months, but the patient recovered to orthotropia at postoperative 12 months with alternative patch treatment and a prism glass prescription. The surgical effect of unilateral lateral rectus muscle advancement was 3.3 ± 0.7 PD/mm at postoperative 1 day, 3.7 ± 0.6 PD/mm at postoperative 1 week, and 3.8 ± 0.7 PD/mm at postoperative 6 months. CONCLUSIONS: Unilateral lateral rectus muscle advancement surgery based on one-fourth of the angle of consecutive esotropia within 25 PD was successful in all 11 cases. The surgical effect was significantly greater in unilateral lateral rectus muscle advancement than in primary lateral rectus muscle recession. Thus, reduction in the amount of surgery should be considered carefully in unilateral lateral rectus muscle advancement for consecutive esotropia.

Eyeball Displacement into Ethmoid Sinus with Good Visual Restoration

PURPOSE: To report a case of eyeball displacement into the ethmoid sinus followed by early surgical intervention and good visual recovery. CASE SUMMARY: A 46-year-old female visited our hospital after she injured the right side of her face. Her visual acuity could not be measured and computed tomography revealed displacement of the right eyeball into the ethmoid sinus, as well as right medial orbital wall fracture and rupture of the right medial rectus muscle. She underwent surgical reduction of the herniated eyeball and surgical correction of the medial orbital wall fracture within 20 hours after the accident. Eighteen months after the surgery, visual acuity of the right eye improved from light perception to 20/28, and her color vision and visual field of the right eye improved to normal range. CONCLUSIONS: Displacement of the eyeball in the orbital wall fracture is very rare, and eyeball displacement into the ethmoid sinus is even rarer. We achieved good visual outcome through early surgical intervention. The early anatomical reduction of the displacement and wall fracture may promote improved final visual outcome in other similar cases.

Comparison of Postoperative Exodrift after First Unilateral and Second Contralateral Lateral Rectus Recession in Recurrent Exotropia

PURPOSE: To compare postoperative exodrift of the first unilateral lateral rectus (ULR) muscle recession with the exodrift of the second contralateral ULR muscle recession in patients with recurrent small-angle exotropia (XT). METHODS: We evaluated the results of a second ULR muscle recession in 19 patients with recurrent XT with deviation angles under 25 prism diopter (PD), following a first procedure of ULR muscle recession for small-angle XT. Recession of the lateral rectus muscle ranged from 8 to 9 mm. The postoperative motor alignment and degree of exodrift were investigated after the first ULR muscle recession and the second ULR muscle recession in the same patients. RESULTS: Observed differences in postoperative ocular alignment between the first ULR muscle recession and the second ULR muscle recession were statistically significant at follow-up periods of six months (7.84 +/- 4.43 vs. 3.89 +/- 3.47 PD), one year (9.58 +/- 4.97 vs. 5.21 +/- 4.94 PD), and at a final follow-up (21.11 +/- 2.98 vs. 7.52 +/- 4.06 PD) after surgery (p = 0.006, 0.013, and 0.000). Postoperative exodrift was statistically different between the first and second ULR muscle recessions at three to six months (2.89 +/-3.75 vs. 0.63 +/- 3.45 PD) and one year to final follow-up (11.52 +/- 5.50 vs. 2.32 +/- 3.53 PD) (p = 0.034 and 0.000). All of the first ULR muscle recession patients showed XT with deviation angles of more than 15 PD at the final follow-up. Regardless, the surgical success rate (<8 PD) after the second ULR recession was 63.16% (12 patients) among the total amount of patients with recurrent XT. CONCLUSIONS: This study shows that changes in exodrift after a second ULR muscle recession are less than changes after the first URL muscle recession among patients with recurrent XT. A second ULR muscle recession may be a useful surgery for small-angle XT patients with deviation angles of 25 PD or less after a first ULR muscle recession.

A Case of Pediatric Medial-Orbital Wall Fracture with Extraocular Muscle Entrapment

PURPOSE: To report a case of pediatric medial wall blowout fracture with entrapment of medial rectus muscle which can be easily misdiagnosed as a cerebral lesion. CASE SUMMARY: A 16-year-old male visited our clinic with headache, severe restriction of his right eye movement, and diplopia after a head injury due to falling occurring 1 day before evaluation. The patient was inebriated at the time of the accident and could not recall the event but occipital hematoma was palpable. Periorbital ecchymosis or edema was not observed with minimal soft tissue injury except mild conjunctival injection on slit-lamp examination. The patient had an 18 prism diopter exodeviation at primary position and severe medial and mild lateral gaze limitation in his right eye. Brain magnetic resonance imaging (MRI) showed no specific cerebral findings although trapdoor orbital medial wall fracture with incarceration of soft tissue and medial rectus muscle at the medial wall fracture site of his right eye was observed. Within 48 hours from the first evaluation, the blowout fracture was repaired and 50 days postoperatively, right eye gaze limitation and diplopia were nearly recovered. CONCLUSIONS: A case of pediatric blowout fracture with uncertain injury location, periocular ecchymosis, or edema absent could be misdiagnosed as a cerebral lesion. If a pediatric patient is experiencing gaze limitation, diplopia, nausea, or vomiting after trauma, neurological examination as well as evaluation for blowout fracture should be performed.

Rectus sheath hematoma – An uncommon complication following caesarean delivery.

Rectus sheath hematoma is a well documented clinical entity, though uncommon and often clinically misdiagnosed cause of acute abdomen. The non-specific nature of presentation combined with a lower incidence of the disorder leads to difficulty in diagnosing. Our patient presented with rectus sheath hematoma, following caesarean section on 9th post-operative day. She presented with wound discharge and lower abdominal pain. The case report is presented to increase the awareness in considering this entity in the differential diagnosis and management of acute lower abdominal pain. Rectus sheath hematoma’s early diagnosis and appropriate treatment may help to prevent complications.

Pulley tissues maintain the mechanical advantage of extraocular muscles under eye adduction: A simulation study / 医用生物力学

Objective To study the biomechanical effect from pulley tissues of extraocular muscles on super adduction of the eye. Methods By the coordinate parameters of extraocular muscles reported in the literature and based on the mechanical equilibrium of eye movement, two mechanical models, active pulley model and non pulley model (as control), were established to simulate eye adduction in the range of 30°-45°. Results For the contribution of medial rectus muscle, the non pulley model produced more force than the active pulley model to control eye adduction, and its corresponding force value increasingly exceeded the physiologically safe threshold (0.5 N). At the maximum simulative adduction of 45°, the force of medial rectus obtained by active pulley model and non pulley model was 0.508 N and 0.782 N, respectively, and the latter was 56% greater than the safe threshold. For controlling eye adduction, the active pulley model consumed much less energy than the non pulley model. Conclusions Due to the existence of pulley tissues, extraocular muscles could control eye adduction by consuming less biological energy and reinforce the ocular derivation. In addition, with the active pulley, the medial rectus muscle could maintain its mechanical advantage under super adduction of the eye.

Result Comparison after Reoperation in Recurrent Exotropia According to the Type of First Operation

PURPOSE: To investigate and compare the clinical courses and surgical success rates of secondary operations in recurrent exotropia according to the type of first operation for correction of exotropia. METHODS: A retrospective chart review was performed for all patients with recurrent exotropia of the basic or pseudodivergence excess types. In group A (36 patients), bilateral lateral rectus (LR) recession was performed as the first operation and uni- or bilateral medial rectus (MR) resection was performed as the second operation. In group B (19 patients), unilateral LR recession-MR resection (R&R) was performed as the first operation and LR recession or R&R in contralateral eye as the second operation. RESULTS: There were no significant differences between the 2 groups when considering age at each operation, frequency of the amblyopia, prescription of prism, time interval for recurrence and reoperation and the final and cumulative success rates. No postoperative complications were observed in either group. The mean number of used muscles for the first and second operation was 3.9 +/- 0.4 in group A, and 3.4 +/- 0.5 in group B (p = 0.001). Mean time interval for occurrence of postoperative orthophoria was 3.7 +/- 6.2 months in group A and 6.5 +/- 16.2 in group B (p = 0.047). In group B, the incidence of esodeviation tended to increase after postoperative 1 month. CONCLUSIONS: The final success rates of reoperation between the 2 types of the first operation in recurrent exotropia were similar. Mean time between postoperative overcorrection of orthophoria was shorter in the group with bilateral LR recession followed by secondary MR resection than in the other group. Unilateral R&R followed by LR recession or R&R in contralateral eye may be more helpful to decrease the number of used muscles than in the bilateral LR recession followed by secondary MR resection.

Result Comparison after Reoperation in Recurrent Exotropia According to the Type of First Operation

PURPOSE: To investigate and compare the clinical courses and surgical success rates of secondary operations in recurrent exotropia according to the type of first operation for correction of exotropia. METHODS: A retrospective chart review was performed for all patients with recurrent exotropia of the basic or pseudodivergence excess types. In group A (36 patients), bilateral lateral rectus (LR) recession was performed as the first operation and uni- or bilateral medial rectus (MR) resection was performed as the second operation. In group B (19 patients), unilateral LR recession-MR resection (R&R) was performed as the first operation and LR recession or R&R in contralateral eye as the second operation. RESULTS: There were no significant differences between the 2 groups when considering age at each operation, frequency of the amblyopia, prescription of prism, time interval for recurrence and reoperation and the final and cumulative success rates. No postoperative complications were observed in either group. The mean number of used muscles for the first and second operation was 3.9 +/- 0.4 in group A, and 3.4 +/- 0.5 in group B (p = 0.001). Mean time interval for occurrence of postoperative orthophoria was 3.7 +/- 6.2 months in group A and 6.5 +/- 16.2 in group B (p = 0.047). In group B, the incidence of esodeviation tended to increase after postoperative 1 month. CONCLUSIONS: The final success rates of reoperation between the 2 types of the first operation in recurrent exotropia were similar. Mean time between postoperative overcorrection of orthophoria was shorter in the group with bilateral LR recession followed by secondary MR resection than in the other group. Unilateral R&R followed by LR recession or R&R in contralateral eye may be more helpful to decrease the number of used muscles than in the bilateral LR recession followed by secondary MR resection.