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

Evaluation of reinforced plication as an alternative to resection in exotropia

Purpose: To evaluate the surgical efficacy of reinforced plication of the medial rectus muscle to resection as an effective muscle strengthening procedure in exotropia. Methods: This is a prospective randomized trial in patients with exotropia who underwent complete orthoptic evaluation followed by random assignment into two groups by using a computer?drawn random number table. Group 1 patients underwent standard resection with recession procedure, and group 2 patients underwent reinforced plication with recession procedure. Follow?up was performed at day 1, 1 week, 1 month, 3 months, and 6 months to assess the surgical efficacy. Results: A total of 80 patients were included in the study of which 39 were in group 1 and 41 in group 2. The mean age in group 1 was 23.48 ± 11.94 years and 23.29 ± 10.02 years in group 2. The mean preoperative deviation in group 1 for distance was 50.13 ± 11.95 PD and 50.12 ± 9.79 PD in group 2 (P = 0.499). In group 1 with a mean surgical dose of 5.27 mm medial rectus resection and 8.04 mm lateral rectus recession, a 7.11 ± 3.95 PD deviation was noted at the end of 6 months. Similarly, in group 2 with a mean surgical dose of 5.16 mm medial rectus plication and 8.16 mm lateral rectus recession, a 6.00 ± 2.46 PD deviation was noted at the end of 6 months. Between groups, ocular surface changes, inter?surgeon comparison, and exotropia subtypes did not reveal any significant differences. Conclusion: In our observation, the reinforced medial rectus muscle plication showed clinically comparable results as compared to the standard resection procedure at the end of 6 months. Therefore, this innovative modification can be considered as an alternative to standard resection

Meta-analysis of unilateral resection-recession versus plication-recession for exotropia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To compare the effectiveness of unilateral lateral rectus recession-medial rectus resection(RR))and lateral rectus recession-medial rectus plication(RP)in the treatment of exotropia. METHODS: Evidence-based medicine research. A systematic database search was conducted Medline, Embase, Web of Science, the Cochrane Register of Controlled Trials and so on from August 2011 to August 2021. Related studies meeting the inclusion criteria were included in our study. The main outcome measures were as follows: success rate and postoperative deviation. Mean difference(MD)and odds ratio(OR)with 95% confidence interval(CI)were statistical analyzed as measurement data and continuous variables statistics. RESULTS: A total of two randomized controlled studies and five retrospective studies were included. The Meta-analysis results showed that the success rate of surgery was similar for RP group compared with RR group(OR=0.65, 95%CI:0.39-1.07, P=0.09). There was no difference in the incidence of poor postoperative prognosis of the two groups(the undercorrection and overcorrection rates)(OR=1.59; 95%CI: 0.92-2.74, P=0.10; OR=4.43; 95%CI: 0.69-28.18, P=0.12). There were no significant differences in postoperative deviation and the amount of external oblique drift(MD=0.75, 95%CI: -0.27-1.76, P=0.15; MD=-0.34, 95%CI: -1.30-0.63, P=0.50). CONCLUSION: The success rate of RP and RR surgery is close to the incidence of poor postoperative prognosis, moreover, there was no significant difference between the deviation and the amount of external oblique drift after the two surgeries, RP is an effective surgical procedure for the treatment of exotropia.

Effect analysis of partial transposition of vertical rectus combined with medial rectus recession under microscope on treatment of complete abducens nerve palsy esotropia / 上海交通大学学报（医学版）

Objective: To investigate the clinical effect of partial transposition of the vertical rectus combined with medial rectus recession on the treatment of abducens nerve palsy esotropia under the microscope. Methods: Nine patients with abducens nerve palsy esotropia were treated in Suzhou Kowloon Hospital, Shanghai Jiao Tong University School of Medicine from March 2015 to June 2017. The strabismus surgery was performed under the microscope, with partial transposition of the vertical rectus combined with medial rectus recession. Postoperative follow-up was performed to observe the effect. Results: After 1 week, 7 patients’ primary position were orthotopic(within ±10Δ), and 2 patients were undercorrection (+15Δ and +20Δ). Abduction function of all the patients improved significantly. The eyes could cross the midline. After 1 month, 6 patients’ primary position were orthotopic (within ±10Δ), 3 patients were undercorrection(respectively +15Δ, +15Δ and + 30Δ). After 1 year, 5 patients’ primary position were almost orthotropia (within ±10Δ), and 4 patients were undercorrection (respectively +15Δ, +15Δ, +30Δ and +40Δ). Conclusion: Partial transposition of the vertical rectus combined with medial rectus recession under the microscope is a safe and effective surgical method in treatment of complete abducens nerve palsy esotropia. It can not only improve the ocular position, but also effectively improve the abduction function of the paralytic eye. However, it is easy to be undercorrection in the long-term.

Acute isolated medial rectus palsy due to infarction as a result of hypercoagulable state: A case report and literature review

Isolated medial rectus palsy in an otherwise healthy individual is a very rare entity. However, this may point towards underlying systemic pathology. This is a case report of an otherwise healthy young adult male who presented with sudden onset non-progressive blurring of vision in right eye. A series of investigations were performed and the patient was diagnosed to have a rheumatological disorder. Isolated muscle palsies in young patient may be masking a systemic disorder and needs to be evaluated thoroughly.

Surgical Outcomes of Modified Medial Rectus Resections in Recurrent Intermittent Exotropia

PURPOSE: To evaluate the outcomes of modified medial rectus (MR) resection using a lowered amount of MR resection for recurrent exotropia after bilateral lateral rectus (LR) recessions. METHODS: Fifty-six patients, who underwent MR resection from 2003 to 2017 for recurrent exotropia after bilateral LR recessions, were included. MR resection was performed using modified MR resection with a smaller amount of resection than the standard of 4 mm resection at 20 prism diopters (PD) of exotropia. Postoperative surgical results at 1 month, 6 months, 1 year and 2 years were classified as a success (5 PD esotropia [ET]-10 PD exotropia [XT]), overcorrection (>5 PD ET), and undercorrection (>10 PD XT). The clinical factors affecting surgical results at postoperative 6 month and 2 years were also evaluated. RESULTS: The success rate was 78.2% at postoperative 1 month and 87.5% at postoperative 6 months. The overcorrection rate was 21.8% and the undercorrection rate was 0% at postoperative 1 month. At postoperative 6 months, the overcorrection rate decreased to 0% and the undercorrection rate was 12.5%. The success rate was 85.7% at postoperative 1 year and 66.6% at postoperative 2 years. There was no clinical factor affecting the surgical outcomes except the ocular alignment at postoperative 1 month. The deviation at postoperative 1 month was more esotropic in patients with success at postoperative 6 months and 2 years than that in patients with undercorrection (p < 0.05). CONCLUSIONS: The modified MR resection showed favorable results of 87.5% at postoperative 6 months and 85.7% at 1 year. The angle of deviation at postoperative 1 month was an indicator of subsequent surgical outcomes.

Bilateral medial rectus palsy due to midbrain infarction following concussion head injury

Here, we report a rare case of bilateral medial rectus palsy following closed head injury. An adult male had an accidental fall which rendered him unconscious. This was followed by diplopia and restricted ocular motility. He received supportive medical therapy. He was examined for systemic medical and ophthalmic findings. Routine laboratory tests and imaging techniques were employed as per the symptoms. Diffusion-weighted imaging on magnetic resonance imaging proved it to be a rare presentation of small bilateral midbrain infarct. He recovered fully after 8 months.

The Effect of Bilateral Medial Rectus Resection for Recurrent Intermittent Exotropia

PURPOSE: The purpose of this study was to investigate the effect of bilateral medial rectus muscle resection on the treatment of recurrent intermittent exotropia. METHODS: A retrospective chart analysis was conducted for 25 patients who underwent bilateral medial rectus resection for recurrent exotropia over 20 prism diopters (PD) between January 2009 and August 2015. The medial rectus was resected from 4.0 to 6.5 mm by 0.5 mm according to the deviation angle. The postoperative angle of deviation was checked at 1 day, 1 week, 3 months, 6 months, and 1 year postoperatively to investigate the amount of corrected deviation per resected muscle. RESULTS: The average preoperative deviation angle was 27.20 ± 5.02 PD exodeviation and the mean resection was 5.10 ± 0.79 mm of the medial rectus. The postoperative angle deviation was 10.68 ± 5.50 PD esodeviation at 1 day. The incidence of esodeviation tended to decrease over time. At 1 year, the postoperative angle deviation was 1.16 ± 7.54 PD esodeviation. The overcorrection rate was 84% at 1 day postoperatively but decreased to 24% at 1 year with a success rate of 68%. The corrected deviation angle per millimeter was 7.53 ± 1.22, 7.75 ± 2.16, 6.27 ± 1.74, 5.50 ± 1.54, and 5.56 ± 1.58 PD/mm at 1 day, 1 week, 3 months, 6 months, and 1 year after surgery, respectively. The dose effect per millimeter decreased over time. The corrected deviated angle per millimeter remained constant regardless of the amount of medial rectus muscle resection at 1 year postoperatively(p=0.939). CONCLUSIONS: Bilateral medial rectus resection for recurrent exotropia over 20 PD tended to overcorrect at first; however, after 1 year, the mean angle of deviation was 1.16 ± 7.54 PD esodeviation. Bilateral medial rectus resection is an effective surgical method for the treatment of recurrent exotropia over 20 PD.

Clinical Characteristics and Outcomes of Smartphone Overusers with Acute Acquired Comitant Esotropia

PURPOSE: To evaluate the clinical features and treatment outcomes of smartphone overusers with acute acquired comitant esotropia. METHODS: We retrospectively reviewed the medical records of patients ≥ 15 years of age who used a smartphone for > 4 hours a day for > 1 year, and who were diagnosed with acute acquired comitant esotropia from May 2011 to January 2016. We analyzed sex, age at the time of manifestation and duration of esotropia, refractive error, deviated angle at the first and final visits, and the results of refraining from smartphone use, use of the Fresnel prism, and surgery for esotropia. RESULTS: A total of 13 patients were studied, including 8 males and 5 females. The mean age at development of esotropia was 22.7 ± 9.7 years. The mean duration of esotropia before the first visit was 28.0 ± 33.0 months, and the mean follow-up period was 16.4 ± 16.4 months. The mean angle of esotropia was 21.8 ± 7.0 prism diopters (PD) at distance and 22.2 ± 7.9 PD at near. There were eight myopic patients; the other patients were emmetropia. The esotropia of all patients did not improve after refraining from smartphone use. There was no improvement in five patients who were wearing the Fresnel prism for ≥ 4 months. A total of six patients were treated with bilateral medial rectus recession; only one patient remained orthotropic at postoperative 6 months, three patients were undercorrected, and two had a recurrence. CONCLUSIONS: Esotropia persisted after refraining from smartphone use or wearing a Fresnel prism in acute acquired comitant esotropia patients who were smartphone overusers, and the surgical prognosis of these patients was relatively poor.

Efficacy of unilateral medial rectus resection in children with residual and recurrent exotropia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To investigate the efficacy of unilateral medial rectus resection in children with residual and recurrent exotropia and analyze the influence of difference types of strabismus and methods of primary surgery on the surgical outcome.METHODS:This investigation was a retrospective case series study that examined data from 48 pediatric patients (48 eyes) who underwent unilateral medial rectus resection between January 2009 and February 2013 for residual and recurrent exotropia.We surveyed the outcome of eye alignment,lateral incomitance,fusion function,stereoacuity in children at 1d,6wk and at last follow-up of 6-32 (mean 11.99± 7.06) mo after the surgery.RESULTS:At 1d after the surgery,the rate of surgical success was 83％ (40/48),and the rate of undercorrection and overcorrection was 4％ (2/48) and 13％(6/48),respectively.At 6wk after the surgery,the rate of surgical success was 81％ (39/48),and the rate of undercorrection and overcorrection was 13％ (6/48) and 6％ (3/48),respectively.At the final follow-up of 6-32 (mean 11.99±7.06) mo,the surgical success rate was 75％ (36/48),and the rate of undercorrection was 25％ (12/48).No patient exhibited overcorrection.There were no significant differences in the surgical success rate either among pediatric patients who had previously undergone different types of surgery or among patients who had been diagnosed with different types of exotropia (P=0.168 and P=0.50,respectively).No patients presented with lateral incomitance or limited ocular motility.CONCLUSION:Unilateral medial rectus resection is a safe and effective surgical approach for treating in children with residual and recurrent exotropia.In addition,it may achieve the same surgical effectiveness regardless of the patients' previous surgical procedures or types of exotropia.

Surgical outcome of extra-large recession of unilateral medial rectus for small angle esotropia in adults / 国际眼科杂志(Guoji Yanke Zazhi)

·AIM: To evaluate the surgical outcomes of adults who underwent extra - large recession of unilateral medial rectus ( UMR) for the treatment of concomitant esotropia less than +30 prism diopter ( PD) .·METHODS: The medical records of 20 patients ( 30 eyes) who underwent surgical correction of concomitant esotropia less than +30 PD were retrospectively reviewed. Patients with esotropia who were previously treated with one or two surgical procedures of adjustable suture ( 10 eyes as observation group with extra-large recession of UMR as 8-9mm, 10 eyes as control group with bilateral MR recession as 4-5mm) were included in the study. The binocular alignment and adduction function were evaluated at postoperative 3d and 3mo.·RESULTS: The male-female rate of the patients was 13:7. The mean age at surgery was 28. 2 ± 19. 9 years old (range:18-42 years old). At 3d after operation, the eye position of the observation group was - 3△ to + 10△(+5. 02△±2. 39△). That of the control group was -2△ to+10△(+4. 86△± 2. 28△). The difference between the two groups was significant (t=4. 36,P<0. 05). At 3mo after operation, the eye position of the observation group was+4△ to +11△(+4. 31△± 1. 65△). That of the control group was +3△to +10△(+3. 91△±2. 68△). The difference between the two groups was not significant (t= 2. 01,P>0. 05). There was no statistic difference in the postoperative AC/A between two groups (3. 09±0. 15 vs 3. 16±0. 09; t=2. 18,P> 0. 05 ) in postoperative 3mo. Three eyes of the observation group had adduction limitation in postoperative 3d, while none of patients in control group had this. None in the two groups showed the limitation in postoperative 3mo.· CONCLUSION: The surgical correction with UMR recession less than 9mm is safe in small angle esotropia adults, without adduction limitation.

Fractura aislada de pared medial de órbita / Isolated orbital medial wall fracture

Abstract Background: Orbital floor fractures are a common finding in facial trauma and may be accompanied by medial orbital wall fracture in 7 to 53% of the cases. Isolated medial wall fractures are rare and usually asymptomatic, being detected as incidental findings. case report: We report a 75 years old female consultingin the emergency room due to a left orbital trauma. An orbital CAT scan identified a fracture of the medial orbit wall that did not require treatment.

Resumen Introducción: Las fracturas del suelo de la órbita son habituales en los traumatismos faciales y entre un 7 y un 53% de los casos se asocian con fracturas de la pared medial. Pero las fracturas aisladas de la pared medial son infrecuentes y la mayoría asintomáticas, siendo un hallazgo habitualmente incidental. Sin embargo, ciertos signos de alarma (limitación de la movilidad del recto medial, siendo habitual que aparezca de forma retardada por isquemia del músculo debido al atrapamiento) pueden plantear una cirugía urgente. Descripción del caso: Presentamos un caso de una paciente de 75 años que acude al Servicio de Urgencias de nuestro hospital remitida por médico de atención continuada por traumatismo sobre órbita izquierda. A la exploración presenta importante hematoma periorbitario y malar, sin alteraciones visuales. En TC orbitaria se identifica fractura de la pared medial de la órbita que, en ausencia de clínica acompañante, no requiere tratamiento alguno.

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.

Surgical Outcomes Dependent on the Amount of Hyperopia in Infantile Esotropia

PURPOSE: In the present study, short-term and long-term surgical outcomes dependent on the amount of hyperopia in patients with infantile esotropia were analyzed. METHODS: In this study, 80 patients with infantile esotropia who underwent both medial rectus recession from 2007 to 2011 and followed up for at least 36 months were retrospectively examined. The patients were divided into two groups according to the degree of hyperopia: ≥ +3.0 D (high hyperopia [HH], n = 59 patients) and < +3.0 D (non-high hyperopia [NH], n = 21 patients). Clinical characteristics analyzed included surgical success rate and dose-response relationship at the 3-month and 3-year postoperative follow-ups. RESULTS: Initial preoperative alignment (NH: 44.8 ± 10.2 PD, HH: 42.7 ± 11.6 PD, p = 0.450), surgical success rates (NH: 69.5% (41/59), HH: 71.4% (15/21), p = 0.837), under-correction rates (NH: 23.7% (14/59), HH: 9.5% (2/21), p = 0.191) and over-correction rates (NH: 6.8% (4/59), HH: 19.1% (4/21), p = 0.138) were not statistically significantly different between the NH and HH groups. A tendency towards a larger dose-response relationship was observed with HH (NH: 3.9 PD/mm, HH: 4.3 PD/mm) at the 3-month postoperative follow-up, but was not significant (p = 0.105). At the 3-year postoperative follow-up, exodrift was in progress and the dose-response relationship was significantly higher in the HH group than NH group (NH: 3.9 PD/mm, HH: 4.9 PD/mm, p = 0.010). A difference between the groups with amblyopia was observed (NH: 8.5% (5/59), HH: 23.8% (5/21), p = 0.146), although without statistical significance. CONCLUSIONS: The surgical success rate of infantile esotropia was not statistically associated with the amount of hyperopia. There was no statistical association between the dose-response relationship and amount of hyperopia at the postoperative 3-month follow-up, but a statistical association was found in the high dose-response relationship in the HH group at the postoperative 3-year follow-up. Therefore, the conventional amount of recession or muscle resection should be modified in high hyperopic (≥ +3.0 D) infantile esotropia, and long-term postoperative follow-up is necessary.

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.

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.

Surgical Outcome of Sensory Exotropia with Distant-Near Disparity

PURPOSE: To assess clinical features of sensory exotropia with distant-near disparity, surgical outcome, and compare according to amount of medical rectus resection. METHODS: Authors retrospectively reviewed medical records of patients of sensory exotropia with follow-up over 6 months. We defined patients with over 10 prism diopter (PD) disparity as distant-near disparity sensory exotropia (DND-XT) and without disparity as basic sensory exotropia (B-XT). First, we analyzed and compared data of visual acuity, cause and age of visual loss, amount of deviation. Second, Surgical failure was analyzed with dividing DND-XT into conventional surgery group as Parks' formula and reduced medial rectus resection group in accordance with disparity. Surgical success was defined as less than 10 PD deviation in distant, near fixation. RESULTS: B-XT consisted of 58 patients (40 males) and DND-XT of 33 patient (13 males). There was no significant difference between 2 groups in onset and cause of visual loss, deviation at distant fixation. But, log MAR visual acuity of worse eye was better in DND-XT than B-XT (1.74 +/- 0.78, vs. 2.10 +/- 0.74, p = 0.039). Average deviation in distant fixation in DND-XT was 46.55 +/- 16.59 PD in distant and 14.93 +/- 8.91 PD in near fixation. All patients underwent surgery of medial rectus resection and lateral rectus recession and average deviation was 6.83 +/- 7.71 PD at distant fixation, 3.02 +/- 0.69 PD at near fixation at last follow-up. Among 33 patients, 16 patients underwent conventional amount of surgery and 17 patients with reduced medial rectus resection. In patient with conventional surgery, 9 patients were surgical failure (8 patients of over-, 1 patient of under-correction) but in patient with reduced amount of resection, only 1 patient was under-correction. CONCLUSIONS: As a result of medial rectus resection and lateral rectus recession in DND-XT, more surgical failures due to over-correction were observed with conventional resection and higher surgical success was attained in consideration of disparity.

Dose-Effect Relationship of Unilateral Medial Rectus Resection for Recurrent Exotropia

PURPOSE: To investigate the dose-effect relationship of unilateral medial rectus resection for recurrent exotropia after bilateral lateral rectus recession. METHODS: This study comprised 39 patients who underwent unilateral medial rectus resection for recurrent exotropia under 25 PD and bilateral rectus recession for prior surgery of exotropia. The medial rectus was resected from 5.0 to 7.0 mm according to angle deviation at a distance. The postoperative deviated angle was checked at one week, 3 months and 6 months postoperatively to investigate the amount of corrected deviation per resected muscle. RESULTS: The average preoperative deviation was 21.33 +/- 2.96 PD. We resected mean 6.26 +/- 0.57 mm of the medial rectus muscle. The postoperative deviated angle was 0.82 +/- 3.47, 1.87 +/- 3.10 and 5.40 +/- 4.79 PD at 1 week, 3 months and 6 months after surgery, respectively. The corrected deviated angle per millimeter (mm) was 3.29 +/- 0.68, 3.17 +/- 0.58 and 2.75 +/- 0.89 PD at 1 week, 3 months and 6 months after surgery. There were no significant differences among the changes of postoperative deviation per millimeter according to the amount of medial rectus (MR) resection (p-value = 0.423, 0.382) The success rate was 89.75%, 92.31% and 87.18% at 1 week, 3 months and 6 months after surgery, respectively. The expected corrected angle according to the amount of resection remained constant and was 3.04-3.22 PD/mm at 3 months after surgery and 2.79-2.82 PD/mm at 6 months after surgery. CONCLUSIONS: The dose-effect per millimeter was decreased as time passed. There was no statistical difference among the corrected deviation angles per millimeter according to the amount of MR resection. We expect that the calculated dose-effect relationship may be a useful guideline for unilateral medial rectus resection for recurrent exotropia.

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.