Trans-obliquus inferior capitis course of the greater occipital nerve: A potential cause of occipital neuralgia?

Occipital neuralgia can be due to multiple etiologies. One of these is potential compression of the greater occipital nerve (GON). In this regard, one relationship of the GON, its course through the obliquus inferior capitis muscle (OIC), has yet to be well studied. Therefore, the current anatomical study was performed to elucidate this relationship better. In the prone position, the suboccipital triangle was exposed, and the relationship between the GON and OIC was documented in 72 adult cadavers (144 sides). The GON was found to pierce the OIC on four sides (2.8%), unilaterally in two cadavers and bilaterally in one cadaver. Two cadavers were male, and one was female. Histological samples were taken from GONs with a normal course around the OIC, and nerves were found to pierce the OIC. The GON of all four sides identified histological changes consistent with nerve potential compression (e.g., epineurial and perineurial thickening). This is also the first histological analysis of the trans-OIC course of the GON, demonstrating signs of chronic nerve potential compression. Although uncommon, entrapment of the GON by the OIC may be an underrecognized etiology of occipital neuralgia.

Surgical treatment of unilateral acquired superior oblique muscle palsy in adults by inferior oblique belly transposition: a retrospective analysis.

PURPOSE: Evaluate and analyze the efficacy of inferior oblique belly transposition (IOBT) in treating adult patients with diplopia and small-angle hypertropia caused by mild to moderate inferior oblique overaction (IOOA) secondary to acquired superior oblique palsy (SOP). METHODS: Nine adult patients with diplopia and small-angle hypertropia associated with mild to moderate IOOA secondary to unilateral acquired SOP were included in the current retrospective study. All patients received the IOBT procedure between February 2019 and May 2023 at The Second People's Hospital of Jinan and were followed up for more than 6 months after the surgery. During the procedure, the belly of the inferior oblique muscle was fixed to the sclera at 5 mm posterior to the temporal insertion of the inferior rectus muscle. The following indicators were reviewed pre- and post-surgery: the vertical deviation (VD) in the primary position and in the Bielschowsky test, the fovea disc angle (FDA) of the affected eye, changes in IOOA, and diplopia. RESULTS: After IOBT, the VD in the primary position decreased from 7.22△ ± 1.72△ (range 4△-10△) to 1.22△ ± 1.30△ (range 0△-3△). The VD in the Bielschowsky test decreased from 13.00△ ± 1.80△ to 3.22△ ± 1.09△. The FDA decreased from 10.02° ± 3.34° to 6.26° ± 1.91°. The grade of IOOA was reduced from 2.00 (1.00, 2.00) to 0.00 (0.00, 1.00). All changes were statistically significant (P < 0.001 or P = 0.006). Diplopia was resolved completely for all patients. CONCLUSIONS: IOBT can effectively treat adults with diplopia and small-angle hypertropia caused by mild to moderate IOOA secondary to acquired SOP.

Evaluation of graded recession of inferior oblique muscle for correction of different grades of V-pattern strabismus.

BACKGROUND: V pattern identification is essential for proper strabismus management. Graded recession is a tailored approach to treat inferior oblique overaction (IOOA). The aim is to evaluate the efficacy of graded recession of inferior oblique muscle for correction of different grades of V pattern. METHODS: Forty patients from 3 to 18 years old with V pattern strabismus and primary IOOA were evaluated by prism cover test to assess the grade of IOOA and amplitude of V-pattern. Graded recession of IO muscle depends on the amplitude of the V-pattern and degree of IOOA. Eight mm recession for amplitude 15 PD to 20 PD and mild IOOA (10 PD-15 PD or + 1) ,10 mm recession for amplitude 20-30 PD and moderate IOOA (15-25 PD or + 2) and maximum recession for amplitude more than 30 PD and marked IOOA (≥ 25 PD or + 3). Simultaneous correction of the horizontal deviation was performed. Follow up after I week,1 month ,3 month and 6-month. Trial Registration Number (TRN) (NCT05786053) on 23/3/2023. RESULTS: The mean age of the study patients was 9 ± 4.261. Twenty patients (50%) had V-pattern esotropia, 12 (30%) exotropia, 4 (10%) orthotropic and four (10%) had Dissociated vertical deviation (DVD). Four cases 10% were of grade 1, 20 cases (50%) grade 2 and 16 cases (40%) were of grade 3. Of eighty eyes, 66 eyes (82.5%) were fully corrected with no residual IOOA, and 14 eyes (17.5%) were under corrected. V-pattern was corrected in 28 cases 70% and only 12cases (30%) had residual V-pattern grade 1. CONCLUSIONS: Graded recession is an effective procedure for correction of V pattern strabismus with various grades of primary inferior oblique overaction. It can be tailored according to the the degree of IO overaction which is significantly related to the grade of V pattern. The 8 mm recession for IO was significantly related to recurrence or inadequate break of the V pattern in our studied cases. The grade of IOOA correlates with the amplitude of V-pattern. The amount of recession was planned according to preoperative IOOA and grade of V-pattern with frequent undercorrections obtained by the standard 8 mm recession. A + 2 overaction merits a 10-mm recession of the inferior oblique. A + 3 or + 4 overaction merits a 14-mm maximal recession.

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.

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.

Effect of bilateral inferior oblique partial myectomy on V pattern exotropia with inferior oblique overaction.

PURPOSE: To compare the effect of bilateral inferior oblique partial myectomy on V-pattern exotropia patients with bilateral symmetric inferior oblique overaction (IOOA) and asymmetric IOOA. METHODS: This was a retrospective study including 53 V-pattern exotropia patients with bilateral IOOA of all grades who underwent bilateral inferior oblique partial myectomy. Success was defined as the elimination of the IOOA and the collapse of the V pattern at the final follow-up. The fovea-disc angle (FDA) and V-pattern exotropia were compared before and after surgery. RESULTS: This study included 53 V-pattern exotropia patients, containing 29 patients with symmetric IOOA (Group I) and 24 patients with asymmetric IOOA (Group II). The last follow-up ranged from 3 to 16 months (mean of 5 months). After myectomy, 3 eyes in Group I and 2 eyes in Group II were observed with residual grade 1 IOOA. The surgical success rates of IOOA correction in Group I and Group II were 96% and 95%, respectively. The difference was not statistically significant (P = 0.808). V-pattern exotropia collapsed with residual 2 (min. 0, max. 6) PD for Group I and 2 (min. 0, max. 10) PD for Group II, and there was a statistically significant difference between pre- and postoperative V-pattern exotropia in the two groups (P = 0.000). No inferior oblique (IO) underaction or antielevation syndrome (AES) was found in either group. The average preoperative FDA of the right eye and the left eye was (8.93 ± 4.34)° and (10.86 ± 4.27)° in Group I and (9.08 ± 4.92)° and (11.00 ± 5.69)° in Group II. There was a significant difference in preoperative FDA between the right eye and the left eye in the two groups (Group I p = 0.029; Group II p = 0.038). CONCLUSIONS: Bilateral inferior oblique partial myectomy can bring "symmetric" effectiveness in the correction of IOOA and FDA. It can potentially be used as a safe and successful treatment for V-pattern exotropia with bilateral IOOA. In addition, the FDA may be a promising index for evaluating fundus extorsion.

Normative measurements of the superior oblique and inferior oblique muscles by magnetic resonance imaging.

PURPOSE: Normative oblique muscle data may help to diagnose pathological enlargement of the oblique muscles. We aim to describe the normative values of the superior and inferior oblique muscles in an Australian cohort on T1-weighted MRI and fat suppressed contrast enhanced T1-weighted MRI. METHODS: A retrospective review of patients who underwent 3 T orbital MRI. The healthy orbits were used to conduct measurements in patients with a unilateral orbital lesion. The maximum diameters of the superior and inferior oblique muscles were measured on coronal planes. The diameter was measured perpendicular to the long axis of the muscles. RESULTS: The normal measurements (mean ± SD) on fat suppressed contrast enhanced T1-weighted MRI: superior oblique, 3.0 ± 0.5 mm and inferior oblique, 2.7 ± 0.5 mm. On T1-weighted MRI: superior oblique, 2.8 ± 0.5 mm and inferior oblique, 2.5 ± 0.4 mm. In patients who had both sequences performed, the superior and inferior oblique diameters were significantly higher on the fat suppressed contrast-enhanced T1-weighted MRI than the T1-weighted MRI sequence (p < 0.01). CONCLUSION: Oblique muscle enlargement may be seen in a range of orbital diseases. These data may help in diagnosing oblique muscle enlargement. In addition, variations in the measured muscle diameters can be seen according to the scan sequence that is used.

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.

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.

The oblique extraocular muscles in cetaceans: Overall architecture and accessory insertions.

The oblique extraocular muscles (EOMs) were dissected in 19 cetacean species and 10 non-cetacean mammalian species. Both superior oblique (SO) and inferior oblique (IO) muscles in cetaceans are well developed in comparison to out-groups and have unique anatomical features likely related to cetacean orbital configurations, swimming mechanics, and visual behaviors. Cetacean oblique muscles originate at skeletal locations typical for mammals: SO, from a common tendinous cone surrounding the optic nerve and from the medially adjacent bone surface at the orbital apex; IO, from the maxilla adjacent to lacrimal and frontal bones. However, because of the unusual orbital geometry in cetaceans, the paths and relations of SO and IO running toward their insertions onto the temporal ocular sclera are more elaborate than in humans and most other mammals. The proximal part of the SO extends from its origin at the apex along the dorsomedial aspect of the orbital contents to a strong fascial connection proximal to the preorbital process of the frontal bone, likely the cetacean homolog of the typical mammalian trochlea. However, the SO does not turn at this connection but continues onward, still a fleshy cylinder, until turning sharply as it passes through the external circular muscle (ECM) and parts of the palpebral belly of the superior rectus muscle. Upon departing this "functional trochlea" the SO forms a primary scleral insertion and multiple accessory insertions (AIs) onto adjacent EOM tendons and fascial structures. The primary SO scleral insertions are broad and muscular in most cetacean species examined, while in the mysticete minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus) the muscular SO bellies transition into broad fibrous tendons of insertion. The IO in cetaceans originates from an elongated fleshy attachment oriented laterally on the maxilla and continues laterally as a tubular belly before turning caudally at a sharp bend where it is constrained by the ECM and parts of the inferior rectus which form a functional trochlea as with the SO. The IO continues to a fleshy primary insertion on the temporal sclera but, as with SO, also has multiple AIs onto adjacent rectus tendons and connective tissue. The multiple IO insertions were particularly well developed in pygmy sperm whale (Kogia breviceps), minke whale and fin whale. AIs of both SO and IO muscles onto multiple structures as seen in cetaceans have been described in humans and domesticated mammals. The AIs of oblique EOMs seen in all these groups, as well as the unique "functional trochleae" of cetacean SO and IO seem likely to function in constraining the lines of action at the primary scleral insertions of the oblique muscles. The gimble-like sling formed by SO and IO in cetaceans suggest that the "primary" actions of the cetacean oblique EOMs are not only to produce ocular counter-rotations during up-down pitch movements of the head during swimming but also to rotate the plane containing the functional origins of the rectus muscles during other gaze changes.

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.

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.

Retro-equatorial inferior oblique myopexy for treatment of inferior oblique overaction.

AIM: To compare the effectiveness of inferior oblique retroequatorial myopexy and inferior oblique myectomy in correction of inferior oblique overaction (IOOA). PATIENTS AND METHODS: This was a pilot study study including forty patients with primary IOOA of all grades, with or without primary position horizontal deviations. Patients were randomized to have either IO retroequatorial myopexy, group A, or IO myectomy, group B. Success was defined as elimination of the IOOA at 6 months postoperatively. Secondary outcome measures included residual or recurrent elevation in adduction, development of postoperative hypotropia in adduction, postoperative contralateral IOOA, major intraoperative complications, and reversibility of the procedure. RESULTS: At 6 months postoperative, the success rate was higher in the myectomy group (76%) than in the myopexy group (58%); however, this difference was not statistically significant (P = 0.1). The incidence of residual IOOA in myopexy group was significantly higher in patients with higher preoperative grades of IOOA (P Ë‚ 0.001). While this difference was not statistically significant among patients in myectomy group (P = 0.09). Collapse of V-pattern was acheived in nine (69%) patients in myopexy group compared with 8 (57%) in myectomy group with a statistically significant difference (P ≤ 0.001). No patients in myopexy group developed postoperative hypotropia in adduction or postoperative contralateral IOOA, compared with eight (22%) patients of myectomy group (P = 0.002) who developed postoperative hypotropia and two (66.6%) patients with unilateral IOOA who developed contralateral IOOA in myectomy group (P Ë‚ 0.001). No intraoperative complications were encountered in either group. postoperative. CONCLUSIONS: Retroequatorial myopexy of the inferior oblique is as effective as inferior oblique myectomy in eliminating lower and moderate grades of primary IOOA; however, it is more effective in collapsing V-pattern associated with IOOA, and is not associated with postoperative hypotropia or contralateral IOOA after unilateral surgery. It can be used as a safe, reversible alternative to myectomy; however, it is not suitable for high grades of IOOA.

Surgical outcomes of three different weakening procedures of inferior oblique muscle in the treatment of unilateral superior oblique palsy.

BACKGROUND: To compare surgical outcomes and complications of three inferior oblique weakening procedures; Inferior Oblique Myectomy (IOM), Inferior Oblique combined Resection-Anterior Transposition (IORAT) and Inferior Oblique Anterior Transposition (IOAT) in the management of unilateral Superior Oblique (SO) palsy. METHODS: Retrospective review of medical records of all patients with unilateral SO palsy who underwent one of the aforementioned IO weakening procedures at Benha University hospital was performed. Patients were excluded if surgery was bilateral or combined with other vertical muscle surgery. Primary outcome parameters were improvement of Hypertropia (HT) in primary gaze, side gazes, on alternate head turn, Inferior Oblique Overaction (IOOA), Superior Oblique Underaction (SOUA), correction of head tilt and postoperative complications. RESULTS: The review reveals a total of 65 patients with unilateral SO palsy; 54 congenital and 11 acquired, who met the study criteria and were classified into 3 groups; IOM group (24cases), IORAT group (19cases) and IOAT group (22cases). Compared with IOM, both IORAT and IOAT induced significant correction of HT in primary position, ipsilateral gaze, contralateral head tilt and IOOA. IORAT was significantly more effective than IOAT in correction of HT in ipsilateral gaze and contralateral head tilt while there was no statistical difference between the three groups in correction of HT in ipsilateral gaze, contralateral head tilt and SOUA. Postoperative Anti-elevation was significantly recorded following IORAT (6 cases, 31%) than IOAT (3 cases, 13%) and IOM (one cases, 4%). CONCLUSIONS: The IORAT and IOAT were more superior to IOM in correction of IOOA and HT in the primary position and some other gaze positions. However, superiority of IORAT over the other two procedures should be weighed against its significant association with postoperative underaction of IO muscle and anti-elevation syndrome.

[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.

Pseudo inferior oblique overaction, clinical findings, mechanism, and surgical outcomes.

PURPOSE: To investigate clinical findings of the pseudo inferior oblique overaction (IOOA) syndrome and the outcomes of strabismus surgery and to discuss the mechanisms proposed for this disease. METHODS: This syndrome is defined by Y pattern strabismus with exotropia in upgaze. There is marked abduction and hypertropia of the adducting eye when elevation is carried out in side gaze, but there is no hypertropia of the adducting eye in horizontal side gaze. Sixteen patients were included and surgery was performed in 14 patients. Success of the surgical intervention was defined as correction of the Y pattern, orthotropia in primary position, upgaze, and downgaze. RESULTS: Thirteen of the sixteen patients were female. The mean age was 9.6 ± 6.1 years. The mean follow-up time was 14.7 ± 16.9 months. Pre-operatively, 12 patients were orthophoric, and four patients were exophoric (4 to 8 PD) in primary position. In downgaze, all patients were orthophoric. Mean exotropic deviation in upgaze was 25.06 ± 5.9 (18 to 40 PD). Fourteen patients underwent surgery with 2-mm bilateral lateral rectus recession and full tendon supraplacement in seven cases, and 2/3 tendon supraplacement in the other seven patients. The success rate of surgery was 92.8% after the first operation, which reached 100% after a second surgical procedure was performed on one of the patients. CONCLUSIONS: Strabismus surgery is effective in correcting the Y pattern in patients with pseudo IOOA. A 2/3 tendon supraplacement combined with 2-mm recession of the lateral rectus muscles is the preferred treatment.

Unilateral inferior oblique anterior transposition for markedly asymmetric dissociated vertical deviation with unilateral inferior oblique over-action.

BACKGROUND: To evaluate the results of unilateral inferior oblique anterior transposition (IOAT) for markedly asymmetric dissociated vertical deviation (DVD) combined with inferior oblique over-action (IOOA). METHODS: Retrospective chart review of the records of all patients with asymmetric DVD combined with unilateral IOOA in the non-dominant eye who received unilateral IOAT on the non-dominant eye. No other muscles were operated on simultaneously. The amount of DVD and IOOA were measured before and after the operation and statistically analysed. RESULTS: Seventeen patients were included. The mean age at surgery was 23.5 ± 8.4 (range 12-38) years old. The mean postoperative follow-up period was 15.7 ± 7.2 (range 6-32) months. The primary position DVD was 19.6 ± 5.4 (range 14-36) PD preoperatively and decreased significantly to 2.9 ± 2.0 (range 0-8) PD postoperatively (P < 0.01). Preoperatively, there were 2, 7, and 8 patients with + 1, + 2, and + 3 IOOA, respectively, and these were reduced from 2.4 ± 0.7 to 0.3 ± 0.4 postoperatively (P < 0.01). None of the patients were complicated obvious hypotropia, anti-elevation syndrome or IOOA in the contralateral eye. CONCLUSIONS: Unilateral IOAT was recommended in patients with asymmetric DVD coexists with unilateral IOOA.

Damage to the inferior oblique muscle branch of the oculomotor nerve: a complication during orbital fat decompression.

PURPOSE: To present patients who suffered damage to the inferior oblique muscle branch of the oculomotor nerve during orbital fat decompression. METHODS: This study was a retrospective chart review of all patients who underwent orbital decompression surgery between April 2009 and June 2016 by the authors. RESULTS: Among 414 sides from 226 consecutive patients who underwent orbital decompression, the inferior oblique muscle branch was injured in two sides (0.5%) of two patients. Both patients showed hypotropia and incyclotropia immediately after surgery. Within 6 months of injury, ocular deviation on primary gaze had mostly resolved after conservative treatment. None of the patients underwent strabismus surgery. Postoperative computed tomographic images demonstrated that the affected branch was indistinct 3-4 mm posterior to the inferior oblique muscle. CONCLUSIONS: This report indicates that injury to the inferior oblique muscle nerve branch can occur at a point posterior to the inferior oblique muscle during orbital fat decompression; however, the resulting ocular deviation improves considerably within 6 months of injury.

Normative measurements of inferior oblique muscle thickness in Japanese by magnetic resonance imaging using a new technique.

PURPOSE: To measure the thickness of the inferior oblique muscle (IOM) among Japanese by magnetic resonance imaging (MRI) using a new technique. METHODS: This retrospective observational study included 78 patients (36 males and 42 females) who underwent MRI for detection of a unilateral orbital lesion or examining causes of unilateral retrobulbar pain. The thickness of the IOM was measured on the side without the orbital lesion or symptom. On the quasi-sagittal plane through the optic nerve, the major and minor axes of the cross-section of the IOM were measured. On the coronal plane, the maximum thickness perpendicular to the course of the IOM was measured. All measurements were performed using the digital caliper tool of the viewing software. RESULTS: The major and minor axes on the quasi-sagittal plane and the maximum IOM thickness on the coronal plane were 8.00 ± 1.83 mm, 2.98 ± 0.55 mm, 3.04 ± 0.55 mm respectively. There were no significant differences in IOM thickness measurements between sexes and sides (P > 0.050, Student's t-test). No significant correlation with the major axis (r = 0.064, P = 0.576), minor axis (r = -0.065, P = 0.573) or the maximum thickness on the coronal plane (r = -0.099, P = 0.387) was found in relation to age (Pearson's correlation coefficient). CONCLUSIONS: The normative IOM thickness in Japanese was presented on MRI, which were similar among all ages irrespective of sex and side. The new technique we used is easily applicable, and the results may serve as a guide to detect IOM involvement in inflammatory and neoplastic conditions of the orbit.

Expression of MyoD, insulin like growth factor binding protein, thioredoxin and p27 in secondarily overacting inferior oblique muscles with superior oblique palsy.

BACKGOUND: To identify and compare specific protein levels between overacting inferior oblique (IO) muscles in superior oblique (SO) palsy patients and normal IO muscles. METHODS: We obtained 20 IO muscle samples from SO palsy patients with IO overaction ≥ + 3 who underwent IO myectomies (IOOA group), and 20 IO samples from brain death donors whose IO had functioned normally, according to their ophthalmological chart review (control group). We used MyoD for identifying satellite cell activation, insulin-like growth factor binding protein 5 (IGFBP5) for IGF effects, thioredoxin for oxidative stress, and p27 for satellite cell activation or oxidative stress in both groups. Using immunohistochemistry and Western blot, we compared expression levels of the four proteins (MyoD, IGFBP5, thioredoxin, and p27). RESULTS: Levels of thioredoxin and p27 were decreased significantly in the IOOA group. MyoD and IGFBP5 levels showed no significant difference between the groups. CONCLUSIONS: Based on these findings, the overacting IOs of patients with SO palsy had been under oxidative stress status versus normal IOs. Pathologically overacting extraocular muscles may have an increased risk of oxidative stress compared with normal extraocular muscles.