Inferior Oblique Muscle Overaction Research Articles

Outcomes of inferior oblique muscle myectomy with tucking into Tenon’s capsule, cohort prospective study

ABSTRACT Background: Inferior oblique muscle overaction (IOOA) is a prevalent ocular muscle motility disorder. This study aimed to investigate the outcomes and impact of IO muscle myectomy with and without tucking the proximal end of the muscle into Tenon’s capsule in two surgical groups as a treatment for IOOA. Methods: Randomized cohort study that involves two surgical groups. A total of 33 patients (55 eyes). Patients were randomly divided into two groups: first group underwent myectomy without tucking the proximal end of the muscle, whereas the second group underwent myectomy with tucking of the proximal end of the muscle. Each patient had four visits. During each visit, each patient had a comprehensive ophthalmic examination. Surgical success was defined as IOOA grade range of 0 to + 1 and correction of hypertropia in primary gaze. Results: The median age was 6 years. Sixteen (48.5%) patients underwent IO muscle myectomy with tucking, while 17 (51.5%) had an IO myectomy without tucking. Both the tucking and without tucking groups showed reductions in the angles of deviations, but there was no significant difference between the groups at baseline or postoperatively at 6 months. The success rate was 92.85% for the tucking group and 92.59% for the without tucking group. Conclusion: The study suggests that both surgical techniques are effective in correcting IOOA and associated HT, without any clear benefits of the addition of tucking. Ultimately, the two surgical techniques are equally effective, and the choice of surgical technique remains a personal preference of the surgeon.

Clinical effect of superior oblique re-tucking for recurrent or residual compensatory head position

Objective: To evaluate the effects of re-tucking the superior oblique muscle on recurrent or residual compensatory head position. Methods: A retrospective case series study was conducted. 12 recurrent or residual compensatory head position patients (12 eyes) with congenital superior oblique palsy who underwent superior oblique re-tucking in Tianjin Eye Hospital from March 2015 to February 2021 were included. All patients had a history of superior oblique tucking procedure and showed signs of superior oblique muscle palsy without inferior oblique muscle overaction. During surgery, the Guyton forced duction test is used to evaluate the relaxation of the superior oblique muscle tendon, which affects the re-tucking length of the muscle.Their head position, vertical deviation, eye movement, fovea-disa angle, and Bielschowsky head tilt test were assessed pre-and post-surgery. Statistical analysis was performed using ttest and paired samples Wilcoxon signed rank test. Results: Out of the 12 patients, 8 were male and 4 were female, aged between 2 and 9 years. The initial surgery was done at age 6, with a superior oblique recession length of (7.17±1.03) mm. Recurrent head tilt occurred in 11 patients after (3.82±0.98) months postoperatively, and 1 patient had residual head tilt, with a followup period of six months or more. Ocular motility examination revealed underaction of the superior oblique muscle, positive Bielschowsky's head tilt test, and Guyton forced duction tese indicating relaxation of the paralyzed superior oblique muscle tendon. Scar adhesion was observed at the stop of the superior oblique muscle, as well as the previous sutures. The scar and the sutures around the stop of the superior oblique muscle were released, the mean re-tucking amount was(7.83±1.59)mm. Follow-up at 12 to 18 months postoperatively showed disappearance of compensatory head position, significant improvement in superior oblique muscle lag, normal ocular motility, and no occurrence of Brown syndrome. The results of Bielschowsky head tilt were negative in 9 cases and still positive in 3 cases after superior oblique re-tucking. The primary vertical deviation was 2.5 (2.0, 5.3) prism diopter pre-operatively and 1 (0, 1) prism diopter post-operatively, respectively. The difference was statistically significant (U=6.00, P<0.001). The total amount of FDA in both eyes was (-22.04±5.47)° and (-15.27±6.08)° pre-and post-operatively, respectively. The difference was statistically significant (t=2.87, P=0.009). All 12 patients have normal eye movement after superior oblique re-tucking procedure. All patients had no compensatory head position at last follow-up. Conclusions: Superior oblique re-tucking is suitable for patients with relaxation of the superior oblique muscle tendon and extrocular rotation as the main sign. It can effectively and safely correct the recurrent or residual compensatory head position after re-tucking the superior oblique muscle.

Changes in ocular extorsion after horizontal muscle surgery in patients with intermittent exotropia coexisting with hypertropia and mild inferior oblique overaction.

To investigate changes in vertical strabismus and extorsion in patients with intermittent exotropia and mild unilateral inferior oblique muscle overaction (IOOA) who underwent horizontal muscle surgery without vertical or oblique muscle surgery. The medical records of 41 patients were retrospectively analyzed. The patients were followed up for at least 6 months after surgery. Fundus photography was performed before and after surgery, and the sum of the angles of torsion in both eyes was used to measure changes in extorsion using ImageJ software. The enrolled patients were divided into two groups according to the degree of IOOA: patients with grade 1 IOOA were placed in +1 IOOA group and those with grade 2 IOOA in +2 IOOA group. The pre- and postoperative angles of horizontal and vertical strabismus and extorsion were compared between the two groups. The +1 IOOA and +2 IOOA groups included 24 and 17 patients, respectively. The angle of preoperative exotropia did not differ significantly: 25.54 ± 5.68 prism diopters (PD) and 25.65 ± 8.11 PD in the +1 IOOA and +2 IOOA groups, respectively. In the +1 IOOA and +2 IOOA groups, hypertropia was 2.67 ± 1.52 PD and 2.82 ± 1.13 PD, respectively, and extorsion angles were 7.14 ± 2.77° and 7.94 ± 2.87°, respectively. As the IOOA degree increased, the extent of hypertropia and extorsion also increased. However, there were no significant differences between the two groups. Postoperative angles of hypertropia and extorsion significantly decreased in both groups (p < 0.001) after surgery. The degree of change in hypertropia and extorsion was not significantly different between the two groups (p = 0.563 and p = 0.354, respectively). Hypertropia and extorsion improved significantly after horizontal muscle surgery in patients with mild unilateral IOOA and intermittent exotropia. There was no significant difference in the improvement in hypertropia or extorsion between IOOA grades I and II.

What to expect from primary inferior oblique overaction after esotropia surgery

BackgroundOverelevation in adduction is common in patients with primary esotropia. This study evaluates the variation in ocular motility pattern in patients with primary inferior oblique (IO) muscle overaction after esotropia surgery.MethodsThe medical records of consecutive patients who underwent surgery for infantile, partially accommodative, and basic esotropia over eleven years and had at least one year of follow-up were reviewed. Patients with primary inferior oblique muscle overaction (IOOA) presented at baseline or during follow-up were selected and divided according to the first surgery performed concurrently with horizontal rectus surgery: without IO recession (NO-recess), with unilateral IO recession (UNIL-recess), and with bilateral IO recession (BIL-recess). The success (version normalisation or at least 2 points upgrade in severity scale [0–4] in the operated eye), recurrence rates, and the evolution of the non-operated IO muscles were evaluated.ResultsOne hundred and ten patients were included – 53 NO-recess, 26 UNIL-recess, and 31 BIL-recess. Medial rectus muscle posterior fixation sutures surgery (PFS) was performed in 88.2% of patients for esotropia. A recession with graded anterior transposition was the weakening IO procedure. In the NO-recess group, 28 (52.8%) patients normalised their mild IOOA after PFS surgery alone. In the UNI-recess group, the success rate was 88.5%, with 16 (61.5%) patients showing worsened IO muscle of the fellow eye, which prompted additional surgery in 10 patients. In the BIL-recess group, all 31 patients improved the adduction pattern of the operated eye for an 80.6% success rate (6 improved marginally).ConclusionGraded anterior transposition of the inferior oblique muscle effectively normalises versions. However, it’s frequent for a contralateral overaction to become manifest after unilateral IO surgery.

Атипичное косоглазие – синдром Брауна. Диагностика и хирургическое лечение

Purpose. Clarification of indications for surgical treatment of Brown syndrome, choice of the optimal type of surgery and tactics of treatment of secondary overaction of the ipsilateral inferior oblique muscle (IO). Material and methods. Authors evaluate the effectiveness of various types of the superior oblique muscle (SO) weakening procedures based on the analysis of the results of surgical treatment of 65 patients (69 eyes) with Brown syndrome. In 53 cases, tenectomy was performed, and in 16 cases, recession/prolongation of SO. Results. Tenectomy of SO is more effective in surgical treatment of Brown syndrome. In 60 out of 65 (92%) operated patients it was possible to significantly improve the mobility of the operated eye upwards. Secondary overaction of the inferior oblique muscle was eliminated in next step of surgery. Conclusions. Surgical treatment of Brown's syndrome is staged. Indications for surgical treatment are: significant head abnormal position, hypotropia in the primary gaze and in adduction, binocular vision disturbance. The SO tenectomy has provided good functional results in treatment of patients with Brown's syndrome. Key words: Brown's syndrome, incomitant strabismus, superior oblique muscle, surgical treatment, tenectomy, recession, anterior transposition

Systematic ophthalmologic evaluation in cardio-facio-cutaneous syndrome: A genotype-endophenotype correlation.

Cardio-facio-cutaneous syndrome (CFCS) is a rare genetic disorder belonging to the RASopathies, a group of developmental syndromes caused by upregulated RAS/MAPK signaling. Pathogenic variants affecting four genes, KRAS, BRAF, MAP2K1 and MAP2K2, encoding core signal transducers of the pathway, underlie the condition. Major clinical features include a distinctive facies, ectodermal and cardiac anomalies, reduced postnatal growth, intellectual disability, and musculoskeletal abnormalities. Similar to other RASopathies, reports of visual impairment, high refractive error, optic nerve pallor, and other ocular abnormalities have been anecdotally reported in the literature. The aim of our study is to report the prevalence of ophthalmologic abnormalities in a large monocentric cohort of individuals affected by CFCS and explore the occurrence of genotype-endophenotype correlations in this series of patients. We observed that BRAF mutations are associated to a higher prevalence of anisometropia >3D (11.8% vs. 0%) and high astigmatism (29.4% vs. 0%; both p < 0.001) while patients with mutations in other genes had a significantly higher prevalence of myopia >6 D (60% vs. 5.9%; p = 0.012). Pale optic disc was associated with higher prevalence of inferior oblique muscle (IO) overaction (33.3% vs. 0%) and lower prevalence of ptosis (0% vs. 11.8%; both p < 0.001). Combined exotropia, IO overaction and nystagmus were frequent in patients with pale optic nerve. Our findings might suggest the need for earlier ophthalmologic referral for CFCS patients due to high risk of amblyopia, especially those expressing BRAF mutations.

Does Inferior Oblique Muscle Overaction Affect Ocular Vestibular Evoked Myogenic Potentials?

Objectives: Inferior oblique muscle overaction (IOOA) is a common ocular motility disorder. Ocular Vestibular Evoked Myogenic Potentials (oVEMP) are tests that evaluate the reflex pathway between the utricular macula and the inferior oblique muscle to detect vestibular diseases. Our study is of great importance as it is the first study in the literature to evaluate the effect of inferior oblique muscle overaction on oVEMP parameters. Methods: Thirty-five patients with unilateral inferior oblique muscle overaction (IOOA group) and 18 healthy volunteers without any neurological or vestibulocochlear disease were included in this study. All patients and healthy volunteers were evaluated with oVEMP. Results: No statistically significant difference was found between the n1 latency, p1 latency, n1-p1 latency measurement values of the participants included in the study (p&gt;0,05). A statistically significant difference was found between the n1-p1 amplitude measurement values of the participants in patient groups (non-squint eyes, squint eyes) and control groups (p-value was 0.038). Conclusion: In IOOA patients, vestibulo-ocular reflex pathway may be affected, vestibular symptoms may develop thus o-VEMP responses may be affected. A careful anamnesis should be taken in IOOA patients, and it should be kept in mind that n1-p1 amplitudes and asymmetries may be significantly higher when o-VEMP is performed Keywords: o-VEMP, Strabismus, Inferior oblique muscle overaction, Balance, Vertigo

Effectiveness of modified inferior oblique muscle belly transposition for V-pattern exotropia combined with mild to moderate inferior oblique muscle overaction.

To investigate the effectiveness of a modified inferior oblique muscle belly transposition for treatment of V-pattern exotropia combined with mild to moderate inferior oblique muscle overaction. Thirteen cases (23 affected eyes) of V-pattern exotropia with inferior oblique muscle overaction (+ or ++) who underwent the modified inferior oblique muscle belly transposition procedure were retrospectively reviewed. The amount of V-pattern, grade of inferior oblique overaction, degree of vertical strabismus, abnormal head posture, and the fovea-disc angle were evaluated before and after surgery. The V-pattern was corrected in all cases, and the amount of V-pattern reduced by 17.85±5.13 prism diopter (PD) on average (t=16.07, P<0.001). The surgical cure rate for mild to moderate inferior oblique muscle overaction was 87.0% (20/23). The degree of the fovea-disc angle has a mean reduction of 5.45°±2.87° (t=3.95, P=0.003) after surgery. The mean vertical deviation in 5 cases with a small-angle hypertropia (5.23±3.06 PD) in the primary position reduced by 3.15±1.86 PD (t=6.10, P<0.001). No serious complications were observed. The modified inferior oblique muscle belly transposition procedure can effectively treat mild to moderate inferior oblique overaction and relieve the V-pattern, which is safe and easy to perform.

Differences in Inferior Oblique Muscle Satellite Cell Populations between Primary and Secondary Inferior Oblique Muscle Overaction

Introduction: The aim of the study was to compare the number of paired box 7 (PAX7)-positive, myogenic differentiation 1 (MyoD1)-positive, and neural cell adhesion molecule-1 (NCAM)-positive satellite cells in human primary versus secondary inferior oblique muscle overaction (IOOA). Methods: This prospective observational study enrolled patients who underwent inferior oblique muscle myectomy at the Department of Pediatric Ophthalmology and Strabismus in Tianjin Eye Hospital between January 2020 and November 2020. The muscle specimens were processed. Immunohistochemistry and immunofluorescence were used to quantify inferior oblique muscle fiber diameter and PAX7-positive, NCAM-positive, and MyoD1-positive satellite cells. Results: Thirty-eight patients with inferior oblique overaction were enrolled: 18 with primary IOOA and 20 with secondary IOOA. The participants were significantly younger in the secondary IOOA group than in the primary IOOA group (2.8 ± 1.2 vs. 9.0 ± 3.2 years, p < 0.001). The muscle fiber diameter between the two groups was not significantly different (13.5 ± 1.4 vs. 13.8 ± 0.7 µm, p = 0.530), but PAX7+ (3.3 ± 2.8 vs. 1.8 ± 0.6, p < 0.001), NCAM+ (3.6 ± 1.5 vs. 1.7 ± 0.2, p < 0.001), and MyoD1+ (4.8 ± 1.9 vs. 2.7 ± 0.5, p < 0.001) cell counts were higher in primary IOOA than in secondary IOOA. Conclusions: PAX7pos, MyoD-1pos, and NCAMpos cell counts per laminar nucleus were almost 2-fold higher in the primary IOOA group than in the secondary IOOA group.

Novel Inferior Oblique Muscle Y Splitting Procedure to Minimize the Anti-Elevation Syndrome: A Pilot Study.

PurposeTo describe novel Y splitting procedure of inferior oblique muscle to mitigate the anti-elevation syndrome.MethodsA pilot, prospective interventional study was undertaken to assess the effect of inferior oblique muscle Y-splitting in patients with unilateral 3+ or more overaction. To correct primary gaze hypertropia and the excyclotorsion, a Y-splitting procedure was performed (along with routine horizontal muscle surgery as per the deviation) in 14 subjects. The effect of surgery was assessed at baseline and at 6 months post-intervention.ResultsThe mean age of 14 subjects was 25.14±7.70 years. The mean pre-operative hypertropia, excyclotorsion and inferior oblique muscle over-action was 18.42±3.50 PD, 14.14±2.65 degrees, and +3.21±0.42 respectively. Following surgery, this was reduced to 1.57±1.74 PD of residual hypertropia (a net correction of 16.85±2.31 PD, p = 0.005), 3.85±1.46 degrees of residual excyclotorsion (a net correction of 10.28±1.72 degrees, p < 0.05), and +0.28±0.46 of residual inferior oblique over-action (a net correction ~+3) at the end of 6 months. Amongst fourteen patients, three patients still experienced residual/variable anti-elevation effect, and during the study period none of them experienced any adverse event and none of them required any additional surgeries.ConclusionWhile anteriorizing the inferior oblique muscle to correct primary gaze hypertropia and the excyclotorsion, a novel “Y splitting” procedure can be followed to achieve the desired results with mitigated anti-elevation effect.

Transposition of the inferior oblique muscle belly without disinsertion for overshoot in adduction treatment

PurposeTo evaluate the efficacy and safety of inferior oblique muscle transposition and myopexy in patients with mild/moderate inferior oblique muscle overaction, with or without diplopia. MethodWe retrospectively analysed data for the 12 patients who underwent the technique. Data were collected from October 2018 to September 2021. Surgery was performed by suturing the inferior oblique belly to the sclera at 5 mm posterior to the temporal end of the inferior rectus. All 12 patients had mild hypertropia (≤6 prism diopters [pd]) in primary position and mild/moderate inferior oblique overaction. Mean preoperative hypertropia was 4.42 pd ± 1.62. Diplopia was recorded in 10 cases. The diagnoses were fourth nerve paresis (9), unilateral primary inferior oblique overaction (2) and dissociated vertical deviation (1). Torticollis was observed in 7 cases, 2 had subjective torsion and 2 objective torsion. ResultsMean age was 46.86 ± 25.1 years (50%: men). Diplopia resolved in 9 of the 10 cases. The mean final vertical deviation was 1.5 ± 2.93 (p = 0.001) pd in straight gaze. Of 7 mild overshoot in adduction, it disappeared in 3 and 4 remained the same. Of 5 moderate overshoot in adduction, 2 improved to mild and 3 disappeared. Torticollis was eliminated in 5 patients and improved in another 2. Mean time from surgery was 14.08 ± 8.05 months. There were no overcorrections. ConclusionsInferior oblique muscle transposition with myopexy is a safe and effective procedure in patients with mild-to-moderate inferior oblique muscle overaction and small-angle hypertropia, with or without diplopia.

Оптимизация страбизмологического обследования пациентов при планировании хирургического лечения первичной гиперфункции нижних косых мышц

Purpose. To perform a comparative assessment of the results of strabismological examination of patients with primary inferior oblique muscle overaction according to the generally accepted and proposed methods. To analyze the change in the surgical procedure protocol depending on the results obtained. Material and methods. The research included 123 patients with a bilateral symmetric primary inferior oblique muscle overaction. The generally accepted method consisted in measuring the heterotropia magnitude when moving the gaze while turning the head left right and in measuring the magnitude of when moving the gaze following the ophthalmoscope beam when it is horizontally displaced upwards by 25° and downwards by 35° from 33 cm (assessment of V-pattern and its severity). The proposed method consisted in measuring the hypertropia magnitude of the adducted eye with the maximum fixing movement of the abducted eye gaze and in measuring the heterotropia magnitude with the maximum gaze movement upwards and downwards. Results. After the strabismological examination was carried out according to the proposed method, the average magnitude of hypertropia in adduction and V-pattern in the study group was statistically significantly (p&lt;0.05) changed in the diagnostic protocols. A more prominent magnitude of hypertropia was revealed in 110 patients (89.43%). A more prominent V-pattern was diagnosed in 117 patients (95.12%). Studying the specifics of the oculomotor system disorders in patients resulted in optimization of the surgical procedure protocol in 83 patients according to the proposed method (67.48%). Conclusion. The average under-diagnosis of hypertropia and V-pattern during the examination according to the generally accepted method is 3.98±2.39° and 3.72±2°, respectively. Clarification of the oculomotor imbalance characteristics after the examination according to the proposed method requires a change in the surgical procedure protocol in more than 67% of cases. Key words: primary inferior oblique muscle overaction, V-pattern, gaze position, Botox, partial marginal myotomy, myectomy

Влияние диагностики первичной гиперфункции косых мышц на выбор метода хирургического лечения

Purpose. To carry out a comparative analysis of the results of strabismological examination of patients with primary inferior oblique muscle overaction using the generally accepted and proposed methods. Methods. The research included 123 patients with bilateral symmetric primary inferior oblique muscle overaction. The proposed method consisted in measuring hypertropia magnitude of the adducted eye with the maximum fixing movement of the abducted eye gaze and in measuring heterotropia magnitude with the maximum gaze movement upwards and downwards. Results. As a result of diagnostics according to the generally accepted and proposed method, a statistically significant increase in hypertropia and V-syndrome (р &lt; 0.05) was revealed. A more pronounced degree of hypertropia was detected in 110 patients (89.43 %), more pronounced manifestations of the V-syndrome in 117 patients (95.12 %). In 83 patients (67.48 %), the tactics of surgical treatment was optimized. Conclusions. The average underdiagnosis of hypertropia and V-pattern during the examination according to the generally accepted method is 3.98±2.39° and 3.72±2°, respectively. Key words: primary inferior oblique muscle overaction; V-pattern; Botox; partial marginal myotomy; myectomy.

Transposición del vientre del oblicuo inferior sin desinserción en el tratamiento de la hipertropia en aducción

PurposeTo evaluate the efficacy and safety of inferior oblique muscle transposition and myopexy in patients with mild/moderate inferior oblique muscle overaction, with or without diplopia. MethodWe retrospectively analysed data for the 12 patients who underwent the technique. Data were collected from October 2018 to September 2021. Surgery was performed by suturing the inferior oblique belly to the sclera at 5mm posterior to the temporal end of the inferior rectus. All 12 patients had mild hypertropia (≤6 prism diopters [pd]) in primary position and mild/moderate inferior oblique overaction. Mean preoperative hypertropia was 4.42pd ±1.62. Diplopia was recorded in 10 cases. The diagnoses were fourth nerve paresis (9), unilateral primary inferior oblique overaction (2) and dissociated vertical deviation (1). Torticollis was observed in 7 cases, 2 had subjective torsion and 2 objective torsion. ResultsMean age was 46.86±25.1 years (50%: men). Diplopia resolved in 9 of the 10 cases. The mean final vertical deviation was 1.5±2.93 (P=.001) pd in straight gaze. Of 7 mild overshoot in adduction, it disappeared in 3 and 4 remained the same. Of 5 moderate overshoot in adduction, 2 improved to mild and 3 disappeared. Torticollis was eliminated in 5 patients and improved in another 2. Mean time from surgery was 14.08±8.05 months. There were no overcorrections. ConclusionsInferior oblique muscle transposition with myopexy is a safe and effective procedure in patients with mild-to-moderate inferior oblique muscle overaction and small-angle hypertropia, with or without diplopia.

Differences in gene expression between the primary and secondary inferior oblique overaction.

BackgroundThis study sought to define different adaptive changes in the molecular levels of the overacting inferior oblique muscle in primary and secondary inferior oblique overaction.MethodsThe inferior oblique muscles of patients with congenital superior oblique palsy (SOP) and those of patients with congenital esotropia were collected during surgery. RNA-seq technology was performed to detect the differentially expressed genes (DEGs) between the two groups. A comprehensive analysis of the gene expression profiles was then conducted, including the identification of DEGs, a Gene Ontology (GO) analysis, and a gene set enrichment analysis (GSEA). Finally, a protein-protein interaction (PPI) network was constructed with Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and Cytoscape software.ResultsWe identified 221 DEGs, of which 104 were significantly upregulated and 117 were downregulated in the SOP group. Additionally, several isoforms of the myosin heavy chain (MyHC) gene were found to be significantly and differentially expressed in the SOP group, including 3 upregulated fast-twitch MyHC isoforms (i.e., MYH1, MYH4, and MYH13) and 1 downregulated slow-twitch MyHC isoform (i.e., MYH3). The GO analysis indicated that the upregulated DEGs were mainly enriched in the muscle system process and muscle contraction. The GSEA analysis revealed that the upregulated pathways of ribosome, proteasome, oxidative phosphorylation, fatty acid metabolism, viral myocarditis, and cardiac muscle contraction were enriched.ConclusionsOur findings provide insights into the different molecular changes of inferior oblique muscle overaction secondary to SOP and suggest the potential pathological mechanisms of inferior oblique overaction (IOOA) in SOP. The results suggest that upregulated fast-twitch MyHC isoforms and downregulated slow-twitch MyHC isoform in SOP may contribute to the increased force of its inferior oblique muscle.

Graded recession technique versus myectomy in management of inferior oblique muscle overaction

Graded recession technique versus myectomy in management of inferior oblique muscle overaction

The Role of Hypertropia in the Surgical Management of Bilateral Inferior Oblique Muscle Overaction

ABSTRACT Purpose Inferior oblique muscle overaction (IOOA) is an ocular motility anomaly consisting of overelevation in adduction, often associated with ipsilateral hypertropia. The weakening procedure of IO muscle is the most widely used procedure in IOOA. Usually, surgical planning is based on the degree of overaction of the IO muscle. Materials and Methods We have retrospectively analyzed patients with bilateral IOOA with and without hypertropia in primary position, who underwent a bilateral IO weakening procedure. Both the amount of IOOA and the presence of a hypertropia in primary position were taken into consideration for the surgical plan. Results Nineteen patients met the entry criteria for this study. In 12 patients, a hypertropia in primary position was present at baseline, and it was significantly lower after the asymmetrical IO weakening: 11 had an asymmetric IOOA at baseline, and one had symmetric IOOA. None of the remaining seven patients had a vertical deviation in primary position before surgery, despite having asymmetric IOOA. None of them developed a hypertropia in primary position after symmetric IO weakening. Conclusions Our findings outline the utility of considering both the presence of a vertical deviation in primary position and the magnitude of IOOA in this set of patients. Asymmetric inferior oblique weakening procedure is effective in treating a hypertropia in the primary position and bilateral IOOA.

Botulinum Toxin Injection of the Inferior Oblique Muscles for V-Pattern Strabismus and Primary Position Hypertropia

To evaluate outcomes of botulinum toxin (BTX) injection of the inferior oblique (IO) muscle. Retrospective case series. Setting: Single center, ophthalmology department at Boston Children's Hospital. All patients treated with IO muscle injection of BTX (onabotulinumtoxinA) between 2010 and 2020. Sensorimotor evaluations at short-term (<2 months), medium-term (2-4 months), and long-term (≥4 months) intervals. Primary outcomes included median improvement in V-pattern strabismus and primary position hypertropia. Secondary outcomes included IO muscle overaction. Wilcoxon signed-rank tests were performed to identify differences before and after injection. Record review identified 20 patients with a median age of 4.5 (range, 1-69) years. Median BTX dose injected (31 IO muscles) was 5.0 (range, 3.0-7.0) units. Indications included V-pattern strabismus (N=8), hypertropia (N=7), or both (N=5). Median long-term interval was 6.4 (range, 4.1-26.6) months. Injections were concurrent with treatment of horizontal strabismus in all but 3 cases. Median V-pattern magnitude changed from 10 prism diopters (PD) preoperatively to 0 PD short-term (P=.006) and 3.5 PD long-term (P=.34). Median hypertropia changed from 8.5 PD preoperatively to 1.5 PD short-term (P=.01) and 8 PD long-term (P=.87). Median IO muscle overaction grade improved significantly at short-term (P < .001) and long-term (P=.007) intervals. There were no complications associated with the IO muscle injections. BTX injection of the IO muscles can be a useful adjunct to the management of V-pattern strabismus. Intervention for primary position hypertropia may be helpful for short-term relief with no expectation of long-term benefit.

Electron Microscopic and Histopathological Study of the Overacting Inferior Oblique Muscle of the Human Eye

ABSTRACTBackground: Inferior oblique muscle overaction is a common disorder that has a correlation with the anatomical changes of the muscle itself. The changes differ according to the grade of the overaction.Objective: To correlate between the histopathological alternations of the inferior oblique muscle and the different degrees of clinical overaction.Patients and methods: Ten biopsies from inferior oblique muscles were taken during the surgery of strabismus after determining the clinical degree of the overaction. One muscle biopsy was taken during enucleation surgery and considered as a control. All biopsies were examined by light and transmission electron microscopes.Results: By light microscopy, grade II and grade III inferior oblique overaction showed many histopathological findings as muscle fibers degeneration, variable size of muscle fibers, nerve bundles hypertrophy and fibro-fatty infiltrations. Grade III inferior oblique overaction showed fibrosis of perimysium and endomysium, mononuclear infiltration and fatty infiltration. By transmission electron microscopy the muscle fibers showed increased mitochondrial number and mitochondrial variability in shape and size, also showed increased vacuoles and fat droplets.Conclusion: Histopathological alternations in the inferior oblique muscle correlate to the clinical grades of the muscle overaction.

Comparing Two Inferior Oblique Weakening Procedures: Disinsertion versus Myectomy.

Purpose To compare two methods for treating inferior oblique overaction (IOOA): disinsertion versus myectomy of the muscle.Methods In this prospective interventional case series, patients were randomly assigned to undergo either IO myectomy or disinsertion. The changes in vertical and horizontal deviations following these two surgical procedures were evaluated. The postoperative IO function of grade 0 or +1 and the fundus extorsion of grade 0 or +1 was considered as the successful outcome.ResultsThirty-six patients (50 eyes) with a mean age of 12.67 4.05 years were included. In the myectomy group, the mean preoperative hyperdeviation in adduction was 29.5 9.32 prism diopter (PD), which decreased to 9.15 7.86 PD after surgery (P = 0.001). In the disinsertion group, these measurements were 32.73 12.42 and 12.65 9.34 PD before and after the surgery, respectively (P = 0.001). The success rate of surgery based on the IOOA grading was 87.4% and 92.3% in the myectomy and disinsertion groups, respectively (P = 0.780). The successful correction rate of abnormal fundus torsion was 91.6% in the myectomy and 88.4% in the disinsertion group (P = 0.821). In comparison, 48% of the cases in the myectomy group and 50% in the disinsertion group were within the normal range of torsional position postoperatively (P = 0.786). There was no statistically significant difference in terms of changes in the horizontal or vertical deviations, V-pattern, and dissociated vertical deviation between the two groups.ConclusionBoth surgical techniques seem to be effective for treatment of inferior oblique muscle overaction.