What to expect from primary inferior oblique overaction after esotropia surgery : Primary inferior oblique overaction in esotropia.

BACKGROUND: Overelevation 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. METHODS: The 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. RESULTS: One 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). CONCLUSION: Graded 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.

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

AIM: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Morphometry and anatomical variations of the inferior oblique muscle as relevant to the strabismus surgeries.

Effective outcome of inferior oblique (IO) corrective surgeries demands a detailed knowledge of morphometry and variations of IO. Our aim was to study and morphometrically define the surgical anatomy of the IO muscle and its variations. Also to provide easily identifiable surgical coordinates to locate, the IO origin and the oculomotor nerve entry point into the IO. Dissection was performed on 16 cadaveric orbits. IO anatomy, variations, morphometry and relevant surgical distances were measured using digital caliper. IO with multiple bellies was found in five specimens. The IO mean length was 33.1 ± 3.3 mm, width at origin was 3.1 ± 0.6 mm, and width at insertion was 8.8 ± 1.5 mm. For easy localization of origin, its distance from the palpable landmarks, Zygomatico-maxillary suture and fronto-maxillary suture was measured. The mean distance between IO and the optic nerve was 10 mm. Distance of the nerve to inferior oblique entry point to the origin and insertion of the inferior oblique was measured. The nerve to IO was 28 mm long. The mean distance of the nerve entry point to IO origin was 15.5 ± 2.3 mm and distance to IO insertion was 15.2 ± 2.8 mm. A muscular bridge between the Inferior rectus (IR) & IO was found in one case, affecting ~» of the IO length; the distal end of the bridge was 5 mm from the IO insertion. Origin of the IO can be localized on the orbital surface of maxilla, 1-2 cm from the point where zygomatico-maxillary suture cuts the inferior orbital margin and 1-2 cm from the fronto-maxillary suture. In 19% of the orbits, the IO length was less than 30 mm, which may cause traction injury in muscle transposition procedures. The width at insertion is useful as most corrective surgeries are performed at the insertion site. The nerve to IO consistently entered at the center of medial border. The nerve entry point is important surgically as myectomy is performed between it and the insertion point. The safe distance available from the optic nerve was 7 mm. Detailed morphometry of IO may aid surgeons in better surgical planning and execution.

Disinsertion-distal myectomy and tucking of inferior oblique combined with superior oblique full tendon advancement in superior oblique palsy.

PURPOSE: To assess the preliminary outcomes of inferior oblique (IO) disinsertion-distal myectomy and tucking combined with superior oblique (SO) full tendon advancement in patients with Knapp II or III superior oblique palsy. METHODS: This single-centered retrospective study included 16 eyes from 13 patients with Knapp Class II or III SO palsy. All patients underwent IO disinsertion-distal myectomy and tucking combined with SO full tendon advancement while under general anesthesia. Pre- and post-operative levels of vertical deviation in the primary position, abnormal head position, IO hyperfunction and SO hypofunction, torsion, as well as the presence of diplopia, were all measured, and the differences were statistically compared. RESULTS: Pre-operatively, 12 patients had abnormal head positions, and two had diplopia. The pre-and post-operative levels of IO hyperfunction and SO hypofunction, as well as a vertical deviation in the primary position and torsion, all differed statistically significantly (p < 0.01). CONCLUSIONS: Inferior oblique disinsertion distal myectomy and tucking combined with SO full tendon advancement surgery appears to be an effective procedure in patients with congenital and acquired Knapp Class II or III SO palsy.

Clinical Results According to Inferior Oblique Manipulation in Patients with Inferomedial Blowout Fracture Involving the Orbital Strut.

Background: Detachment of the inferior oblique muscle may be necessary under certain circumstances to repair a large inferomedial orbital fracture involving the orbital strut. This study aimed to evaluate the outcomes of patients who underwent surgeries with and without inferior oblique muscle reattachment after its detachment to repair the orbital wall fractures. Methods: Forty patients who underwent repair of combined floor and medial orbital wall fracture involving the orbital strut at a single tertiary institution between January 2014 and December 2020 were reviewed. Groups 1 and 2 comprised 20 patients each, who underwent surgery with inferior oblique muscle detachment without and with reattachment, respectively, and were followed up for at least 6 months postoperatively. Enophthalmos, Goldmann diplopia test, alignment test, ocular motility test, and orbital inferomedial angle ratio were the outcome measures. Results: Statistically significant improvement was observed in ocular motility, diplopia, and enophthalmos postoperatively at the 1- and 6-month follow-up (p < 0.01). The mean postoperative inferomedial angle ratio (102.28 ± 10.62%) was improved significantly compared with the preoperative inferomedial angle ratio (115.61 ± 4.38%) (p = 0.004) in all patients. After surgery, inferior oblique muscle underaction was observed in seven and six patients in groups 1 and 2, respectively, which was associated with preoperative extraocular movement limitation and strabismus. Two patients showed diplopia in both groups at the last follow-up; they had inferior oblique muscle underaction but no enophthalmos. Conclusion: Orbital fracture repair with or without inferior oblique muscle reattachment was clinically effective and safe; however, patients with preoperative strabismus and extraocular motility limitation should be informed of the increased risk of postoperative complications.

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

Purpose: To describe novel Y splitting procedure of inferior oblique muscle to mitigate the anti-elevation syndrome. Methods: A 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. Results: The 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. Conclusion: While 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.

Isolated idiopathic myositis of the inferior oblique muscle biopsied through lateral orbitotomy.

Background: Isolated orbital myositis of the inferior oblique muscle (IObM) is rare, with few reported cases. Case Description: A 65-year-old woman was aware of double vision and left dacryorrhea for 2 months. At presentation, the patient showed mild restriction on the downward gaze. In addition, a subcutaneous mass was palpated on the left eyelid. The blood examination showed normal findings. Cranial computed tomography revealed an isodense mass in the left orbit, located in the inferior, inferolateral, and posterior aspects of the bulb. On magnetic resonance imaging, the mass was well-demarcated, appeared isointense on both T1- and T2-weighted imaging, and was intensely enhanced after intravenous infusion of gadolinium. The patient underwent biopsy through lateral orbitotomy. Microscopically, the resected specimen showed sheet-like proliferation of small round nonneoplastic cells. These cells were positively immunostained for both B- and T-lymphocyte markers. Therefore, we diagnosed the patient with isolated idiopathic myositis of the IObM. The patient was managed with steroids, which resulted in a remarkable resolution of her orbital symptoms. Conclusion: Biopsy findings should be considered when the presentation of orbital myositis is atypical. Lateral orbitotomy may provide a useful surgical window when approaching the posterior belly of the IObM.

Isolated inferior oblique pareses.

PURPOSE: To describe etiology, clinical characteristics, radiological features and management of isolated inferior oblique pareses. METHODS: A diagnosis of inferior oblique paresis was made after a thorough strabismus examination and neuroimaging. The patients were managed surgically with adjustable strabismus surgery, or conservatively. Surgical success was defined as average horizontal deviation within ≤ 10 prism diopters [PD] post-operatively and for vertical deviation, it was ≤ 5 PD, at last follow-up. RESULTS: Seven cases were congenital, 6 cases were bilateral, with esotropia in 6 cases; 'A' pattern in 7 cases and hypotropia in 3 cases. The mean preoperative horizontal deviation was 52.5 PD, and the mean postoperative horizontal deviation was 2.37 PD (p = 0.028). The pre-operative vertical deviation was 18 PD and post-operative vertical deviation was 5 PD. MRI showed reduced IO muscle size; average area being 11.27 mm2 in the affected eyes, with normal sized inferior recti (average: 24.63 mm2) and medial recti muscles (average: 30.08 mm2). Surgical success was seen in all six cases. Average follow-up was 265 days. The Parks' three step test was not valid, except for one acquired unilateral case. CONCLUSION: Isolated pareses of inferior oblique muscle exhibit defective elevation in adduction of the affected eye, 'A' pattern and fundus intorsion, and is confirmed by neuroimaging. These can be successfully managed surgically to correct the deviation.

Inferior oblique muscle of the eye: its foetal development with special reference to understanding of the frequent variants in adults.

BACKGROUND AND MATERIALS AND METHODS: To provide better understanding of frequent variations of the inferior oblique (IO) of adult extraocular muscles, we observed sagittal and horizontal histological sections of the eye and orbits from 32 foetuses (7-34 weeks of gestational age; 24-295 mm of crown-rump length). RESULTS: In early foetuses (7-8 weeks), the IO was restricted at an antero-infero-medial angle of the future orbit. In contrast to extraocular recti, the IO appeared to extend along the mediolateral axis and had no definite tendon. At midterm, the IO tendon became evident. Sometimes, the IO muscle belly attached to the inferior rectus or, the IO tendon divided into two laminae to enclose the lateral rectus. At late-term, a multilayered sheath was evident around the sclera and, via one or some of the fascial layers, the IO was communicated with a fascia enclosing the inferior rectus. At midterm and late-term, the IO originated not only from the maxilla near the orbicularis oculi origin but also from a vein-rich fibrous tissue around the lacrimal sac. Both origins were muscular without intermittent tendon or ligament. Therefore, the fascial connection as well as a direct contact between the IO and the inferior or lateral rectus seemed to provide variant muscular bridges as reported in adults. Moreover, the two attachment sites at the origin seemed to provide double muscle bellies of the adult IO. CONCLUSIONS: Consequently, the present specimens contained seeds of any types of adult variations. The muscle fibres from the lacrimal sac might play a role for the lacrimal drainage.

Entrapment of the inferior oblique and inferior rectus muscles in orbital trapdoor fracture.

A 10-year-old male presented to our institution 6 days after sustaining trauma to his right eye from a fall. A thorough physical examination could not be done due to severe eye pain and inability to open the eyelids; however, computed tomographic imaging done at this time showed a trapdoor fracture with incarceration of the inferior oblique and inferior rectus muscles. The fracture was reduced through a transconjunctival incision and secured with a polytetrafluoroethylene implant. Three months after the surgery, extraocular motility is almost full and equal.

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

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.

The Effects of Modified Graded Recession, Anteriorization and Myectomy of Inferior Oblique Muscles on Superior Oblique Muscle Palsy.

BACKGROUND: The aim was to investigate the effect of inferior oblique (IO) operation (IO myectomy or graded recession and anteriorization) for unilateral and bilateral superior oblique muscle palsy (SOP); Methods: A total of 167 eyes undergoing IO surgery by a single surgeon between 2008 and 2015 were retrospectively reviewed. The method for treating symmetric bilateral SOP was bilateral IO myectomy (n = 102) and the method for treating unilateral SOP or non-symmetric bilateral SOP was IO-graded recession and anteriorization (n = 65). Associated clinical results and other factors were analyzed; Results: Head tilt, vertical deviation, IO overaction, SO underaction degree and ocular torsion angle were all clearly changed, but there was no statistically significance between these two procedures. Mean preoperative torsional angle was 15.3 ± 6.4 degree, which decreased to 5.3 ± 2.7 degree after surgery. Preoperative torsional angle, IOOA and SOUA degree were all significantly affected in postoperative torsional angle (p = 0.025, 0.003 and 0.038). Horizontal rectus muscle and IO muscle operation did not interfere with each other's results (p = 0.98); Conclusions: Symmetric bilateral SOP could be treated with bilateral IO myectomy and IO-graded recession and anteriorization should be reserved for unilateral SOP or non-symmetric bilateral SOP.

Anatomical implication of less occurrence of inferior oblique muscle entrapment in orbital floor trapdoor fracture.

PURPOSE: To examine the anatomy of the inferior oblique (IO) muscle and its surrounding structures to clarify why IO muscle entrapment develops less in orbital floor trapdoor fractures. METHODS: Computed tomographic (CT) images on the unaffected sides were obtained from 64 patients with unilateral orbital fractures. On coronal planes, presence or absence of an infraorbital groove below the IO muscle was confirmed. At the level of the medial margin of the infraorbital groove/canal, the distance from the orbital floor to the IO muscle (IO-floor distance), the thickness of the orbital floor, and the shortest distance from the inferior rectus (IR) muscle to the orbital floor (shortest IR-floor distance) were measured. On quasi-sagittal planes, the distances from the inferior orbital rim to the inferior margin of the IO muscle (IO-rim distance) and the most anterior point of the infraorbital groove (groove-rim distance) were measured. RESULTS: The infraorbital groove was found below the IO muscle in eight patients (12.5%), and the IO-rim and IO-floor distances were significantly longer than the groove-rim and shortest IR-floor distances, respectively (p < 0.001). The orbital floor below the IO muscle was significantly thicker than that below the IR muscle (p < 0.001). CONCLUSION: Although the medial margin of the infraorbital groove is the most common fracture site, the IO muscle was not located above the groove in most cases. A longer IO-floor distance and thicker orbital floor below the IO muscle may also contribute to less occurrence of IO muscle entrapment in orbital floor trapdoor fractures.

Inferior oblique muscle belly transposition and myopexy for diplopia.

To evaluate the outcomes of and review the indications for Inferior oblique muscle belly transposition in adults with diplopia and small-angle hypertropia associated with mild or moderate upshoot in adduction. We retrospectively analyzed data for the six patients who underwent the technique. Surgery was performed by suturing the inferior oblique belly to the sclera at 5 mm posterior to the temporal pole of the inferior rectus. Data were collected from October 2018 to April 2020. All six patients had diplopia and mild hypertropia (≤6 prism diopters [pd]) in primary position. Mean preoperative hypertropia was 4.17 pd (range, 2-6 pd). Mean age was 51 ± 28.71 years. The diagnoses were fourth nerve paresis (5) and dissociated vertical deviation (1). All patients had mild/moderate upshoot in adduction. Torticollis was observed in four cases. Diplopia resolved in 5 of the 6 cases. The mean final vertical deviation was 2 pd in straight gaze. Torticollis was eliminated in 2 patients and improved in another 2. The upshoot in adduction was totally eliminated in the six patients. Transitory mild limitation of elevation in adduction was observed in two patients during the first week after surgery. No ocular torsion was diagnosed after surgery. Mean time from surgery was 11.5 months. No overcorrections were recorded. Inferior oblique muscle belly transposition with myopexy is a good alternative procedure in patients with diplopia associated with mild-to-moderate upshoot in adduction and small-angle hypertropia.

Effect of inferior oblique muscle belly transposition on versions and vertical alignment in primary position.

PURPOSE: To evaluate the effect of inferior oblique muscle belly transposition (IOBT) on vertical deviation (VD) in primary position and inferior oblique overaction (IOOA). METHODS: Twenty-eight patients who underwent unilateral IOBT for mild hypertropia (≤ 10△) due to unilateral IOOA were included. Surgical results regarding the correction of hypertropia, IOOA, and fovea disc angle (FDA) were analyzed and compared between groups A (VD ≤ 5△) and B (5△ < VD ≤ 10△). RESULTS: IOBT showed an overall reduction of 5.86△ (± 2.24△) of primary position VD, a mean correction of 1.00 (± 0.27) of IOOA, and an average change of 1.83° (± 3.02°) of FDA. The surgical success rate of IOBT for VD correction and IOOA elimination in all patients was 68% and 71%, respectively. The correction of VD was correlated with preoperative VD significantly (r = 0.86, p < 0.001). Consistently, IOBT demonstrated comparable efficacy in reduction of VD between group A and group B (p = 0.507). Furthermore, the two groups were comparable in the success rates for correcting VD and IOOA (both p > 0.05). None of the patients developed consecutive hypotropia, postoperative contralateral IOOA, or anti-elevation syndrome postoperatively. CONCLUSIONS: IOBT achieved satisfactory outcomes in patients with mild primary position VD (≤ 10△) that is associated with unilateral IOOA, without any risk of overcorrection of VD and contralateral IOOA for a follow-up period of up to 12 months. This procedure is considered effective and safe alternative for weakening the IO in patients with appropriate surgical indications.

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. RESULTS: Thirty-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. CONCLUSION: Both surgical techniques seem to be effective for treatment of inferior oblique muscle overaction.

Two cases of acquired bilateral trochlea nerve palsy treated by simultaneous inferior rectus muscle nasal transposition and inferior oblique muscle myectomy.

PURPOSE: To report two cases of acquired bilateral trochlea nerve palsy with large torsional deviation successfully treated by simultaneous bilateral inferior rectus muscle (IR) nasal transposition and inferior oblique muscle (IO) myectomy. OBSERVATIONS: Case 1 was of a 54-year-old man with torsional diplopia after a traffic accident. He showed 32° and 38° excyclotorsion in the primary and downward gazes, respectively. Case 2 was of a 56-year-old woman with torsional diplopia after a brain tumor operation. She showed 25° and 33° excyclotorsion in the primary and downward gazes, respectively. We simultaneously performed bilateral IR nasal transposition and IO myectomy in these two cases. Postoperatively, case 1 presented with improved excyclotorsion, with 2° and 7° excyclotorsion in the primary and downward gazes, respectively; case 2 similarly presented with improved excyclotorsion, with 4° and 12° excyclotorsion in the primary and downward gazes, respectively. CONCLUSIONS AND IMPORTANCE: Simultaneous bilateral IR nasal transposition and IO myectomy are effective for treating large-angle torsional deviations, especially in downward gaze, requiring only one operation. A new surgical approach is suggested for the successful treatment of large torsional deviations, requiring only one operation.

[Surgical treatment of vertical strabismus. Part 2. Indications, scheduling, methods]. / Khirurgicheskoe lechenie vertikal'nogo kosoglaziya. Chast' 2. Pokazaniya, sroki provedeniya, metody.

Treatment of vertical strabismus will almost inevitably involve surgery when it is associated with hyperfunction of the inferior oblique muscle due to the weakness of vertical fusion (3.0-4.0 ave dptr), the presence of cyclotropy and torsional diplopia. Many operations aimed at weakening the lower oblique muscle have been described. However, they have a number of negative aspects associated with high invasiveness, difficulty of technical implementation due to the need for manipulations in the inaccessible area of the eye in proximity to the optic nerve, macular area, large vessels, as well as long duration of the operation, inability to dosage the result of the operation, low functional results. They are, to a large extent, absent in the operation of anterior transposition in which the neurofibrovascular bundle serves as the axis of rotation of the lower oblique muscle changing the vector of its action and increasing the effectiveness of treatment. Despite all the advantages of that technique, its use is still limited due to the lack of methods for controlling the amount of anterior transposition for the treatment of hyperfunction of the inferior oblique muscle, especially of small degrees.

The Effect of Inferior Oblique Muscle Z-Myotomy in Patients with Primary Inferior Oblique Overaction.

Objectives: To investigate the surgical results of the inferior oblique muscle Z-myotomy in patients with inferior oblique muscle overaction (IOOA). Materials and Methods: The medical records of patients who had undergone inferior oblique muscle Z-myotomy for primary IOOA in a single center between 2017 and 2018 were retrospectively analyzed. All patients had mild IOOA (+1 and between +1 and +2). Preoperative and postoperative IOOA degrees and ocular motility examinations were evaluated. Inferior oblique muscle Z-myotomy is performed at 6 mm along the physiological muscle line after identifying the lower oblique muscle through an inferotemporal fornix incision. Results: Forty-seven eyes of 44 patients were included in the study. The patients were divided into those with +1 IOOA (n=37, 78.7%) and those with +1-2 IOOA (n=10, 21.3%). The mean age of the +1 group was 14.18±11.8 years and the mean age of the +1-2 group was 13.40±7.45 years. The mean follow-up time was 10.56±8.7 (6-17) months. Bilateral Z-myotomy was performed in 3 (6.8%) and unilateral in 41 (93.2%) of the patients. IOOA correction was observed in 43 (91.4%) of the 47 eyes after Z-myotomy, while 4 (8.6%) eyes still had preoperative levels of IOOA. There was no statistically significant difference in surgical success rate between the groups (p=0.849). When preoperative and postoperative IOOA values were compared, there was a statistically significant decrease in IOOA values in the postoperative period (p=0.001). No intraoperative or postoperative complications were observed. Conclusion: Inferior oblique Z-myotomy is a simple, fast, sutureless surgical procedure in which the original muscle insertion is preserved. Z-myotomy of the inferior oblique muscle can be used as a successful attenuation method in patients with minimal IOOA.

Intramuscular Nerve Distribution of the Inferior Oblique Muscle.

Purpose: The intramuscular nerve distribution in the extraocular muscles is important for understanding their function. This study aimed to determine the intramuscular nerve distribution of the oculomotor nerve within the inferior oblique muscle (IO) using Sihler's staining.Method: Seventy-two IOs from 50 formalin-embalmed cadavers were investigated. The IO including its branch of the oculomotor nerve was finely dissected from its origin to its insertion point into the sclera. The total length of the muscle and its width were measured. The intramuscular nerve course was investigated after performing Sihler's staining, which is a whole-mount nerve-staining technique that stains the nerves while rendering other soft tissues either translucent or transparent.Results: The total length of the muscle and muscle width were 30.0 ± 2.8 mm (mean±standard deviation), 8.8 ± 1.2 mm, respectively. The oculomotor nerve enters the IO around the middle of the muscle and then divides into multiple smaller branches without distinct subdivisions. The intramuscular nerve distribution within the IO has a root-like arborization and supplies the entire width of the muscle. The Sihler's stained intramuscular nerve course (covering a length of 7.6 ± 1.2 mm) finishes around the distal one-third of the IO in gross observations.Conclusion: Sihler's staining is a useful technique for visualizing the gross nerve distribution of the IO. This new information about the nerve distribution and morphological features will improve the understanding of the biomechanics of the IO.