Clinical characteristics and surgical outcomes in patients with superior oblique muscle palsy: a retrospective study on 1057 patients.

BACKGROUND: To evaluate the clinical findings of patients with SOP who underwent surgery. METHODS: This historical cohort study was performed on 1057 SOP patients managed with surgery in Farabi Hospital, Iran, from 2011 to 2022. RESULTS: There were 990 (93.7%) patients with unilateral SOP with the mean age of 21.8 ± 14.8 years. Of these, 715 patients (72.2%) were diagnosed with congenital SOP, and 275 patients (27.8%) had acquired SOP (P < 0.001). In contrast, 67 (6.3%) patients were diagnosed with bilateral SOP, with the mean age of 19.4 ± 15.6 years. Among these, 18 cases exhibited the masked type. The mean angle of vertical deviation in primary position at far in unilateral and bilateral cases was 15.6 ± 8.3 and 13.3 ± 9.1 △, respectively (P < 0.001). In unilateral cases, abnormal head posture (AHP) was detected in 847 (85.5%) patients and 12 (1.2%) had paradoxical AHP. Amblyopia was found in 89 (9.9%) unilateral and 7 (10.3%) bilateral cases. Solitary inferior oblique myectomy, was the most common surgery in both unilateral (n = 756, 77.1%) and bilateral (n = 35, 52.2%) patients. The second surgery was performed for 84 (8.6%) unilateral and 33 (49.3%) bilateral cases (P < 0.001). The prevalence of amblyopia and the mean angle of horizontal deviation were significantly higher in patients who needed more than one surgery (all P < 0.05). CONCLUSION: Congenital SOP was more than twice as frequent as acquired SOP and about 90% of unilateral and 50% of bilateral cases were managed with one surgery. Amblyopia and significant horizontal deviation were the most important factors for reoperation. TRIAL REGISTRATION: The Institutional Review Board approval was obtained from the Tehran University of Medical Sciences (IR.TUMS.FNM.REC.1400.012) and this study adhered to the tenets of the Declaration of Helsinki and HIPAA.

Trochleaectomy: An Effective Treatment of Trochlear Pain in Monocular Patients.

BACKGROUND: Conventional treatment options for trochlear pain arising from trochleitis or primary trochlear headache include oral anti-inflammatory medications and/or local injection of corticosteroids and local anesthetic. Trochleaectomy is an additional option to consider for monocular patients with intractable trochlear pain. METHODS: We report 3 patients undergoing trochleaectomy for refractory trochlear pain syndromes. RESULTS: Trochleaectomy resulted in resolution of their periocular discomfort. CONCLUSIONS: Trochleaectomy is an effective procedure to treat trochlear pain syndrome in functionally monocular patients.

Unusual manifestation of heat stroke: Isolated trochlear nerve palsy.

Heat stroke is a life-threatening disease characterized by hyperthermia and neurological dysfunction. The central nervous system is highly sensitive to hyperthermia, which causes neurological complications due to the involvement of the cerebellum, basal ganglia, anterior horn cells, and peripheral nerves. Several studies reported about clinical symptoms and brain image findings of heat stroke. Isolated cranial nerve dysfunction caused by lacunar infarction is an extremely rare condition in patient with heat stroke. We experienced a rare case of trochlear nerve palsy due to midbrain infarction caused by heat stroke.

Superior oblique myokymia, a review.

PURPOSE OR REVIEW: Superior oblique myokymia is a rare, monocular condition that typically presents in healthy adults. In this article, we review the proposed pathophysiology, describe the typical clinical presentation, and discuss the recommended work up and various treatment options. RECENT FINDINGS: Treatment for this condition ranges from observation and reassurance to various topical and systemic medications. Both strabismus surgery and neurosurgery are reserved for patients who fail medical therapy or are intolerant to medication secondary to side effects. SUMMARY: Due to its episodic nature, SOM is often under-diagnosed. We highlight key features in a patient's clinical history and the examination findings that suggest and support the diagnosis, with review of available treatment options.

Clinical characteristics according to the laterality of ocular torsion in unilateral superior oblique palsy.

BACKGROUND: To compare clinical characteristics according to the laterality of objective ocular torsion in patients with unilateral superior oblique palsy (SOP). METHODS: This retrospective study included all patients with a diagnosis of unilateral SOP. They were classified into subgroups according to correspondence between the paretic eye and the extorted eye using fundus photography. Ocular alignment and muscle action were tested by the prism and alternate cover tests and 4-scale movement measure. Various clinical factors, including the amount of preoperative ocular torsion and change in ocular torsion postoperative, were compared between the accordance and disaccordance groups. RESULTS: A total of 70 Asian patients (140 eyes) were included and underwent fundus photography preoperatively. Excyclotorsion in the paretic eye was defined as accordance (45 patients), excyclotorsion in the nonparetic eye was defined as disaccordance (25 patients). The presence of horizontal strabismus was detected in 28 (62%) patients in the accordance group and only 8 (32%) patients in the disaccordance group (p = 0.024). All horizontal strabismus observed in the accordance group involved exodeviation. The proportion of horizontal strabismus surgery was also significantly larger in the accordance group than the disaccordance group (p = 0.039). Among those patients, there were 26 who underwent fundus photography postoperatively. There was significant reduction in ocular excyclotorsion postoperatively in the accordance group (p = 0.001), but no significant reduction postoperatively in the disaccordance group (p = 0.270). There was no significant correlation between the amount of torsional reduction and the amount of vertical deviation reduction (p = 0.979). CONCLUSIONS: In cases of preoperative excyclotorsion in paretic eyes, careful consideration of combined horizontal misalignment which may require surgical correction is helpful to manage unilateral SOP.

Inter-Rater Reliability of Cyclotorsion Measurements Using Fundus Photography.

BACKGROUND: The foveo-papillary angle (FPA) on fundus photographs is the accepted standard for the measurement of ocular cyclotorsion. We assessed the inter-rater reliability of this method in healthy subjects and in patients with trochlear nerve palsies. PATIENTS AND METHODS: In this methodological study, fundus photographs of healthy subjects and of patients with trochlear nerve palsies were made with a fundus camera (Zeiss Fundus Camera FF 450 plus, Jena, Germany). Three independent observers measured the FPA on the fundus photographs of all subjects in synedra View (synedra View 16, Version 16.0.0.11, Innsbruck, Austria). RESULTS: One hundred and four eyes of 52 subjects (26 healthy controls and 26 patients) were assessed. The mean FPA of the healthy controls was 5.80 degrees (°) [± 0.44 standard error of the mean (SEM)] compared to 11.55° (± 0.80 SEM) for patients with trochlear nerve palsies. The inter-rater reliability of all measured FPAs showed an intraclass correlation coefficient (ICC) of 0.98 (95% CI 0.97 - 0.98). CONCLUSIONS: The inter-rater reliability of objective cyclotorsion measurements using fundus photographs was very high.

Effect of modified graded recession and anteriorization on unilateral superior oblique palsy: a retrospective study.

BACKGROUND: Several inferior oblique (IO) weakening methods exist for correction of superior oblique palsy (SOP). A previously reported method involved recession and anteriorization according to IO overaction (IOOA) grade, which might be subjective and cause upgaze limitation and opposite vertical strabismus. Therefore, this study attempted to examine the efficacy of modified graded recession and anteriorization of the IO muscle in correction of unilateral SOP without resulting in upgaze limitation or opposite vertical strabismus. METHODS: A total of 26 patients (male, 16; female, 10; age: 3-40 years) with SOP and head tilt or diplopia underwent modified graded recession and anteriorization. Patients were grouped by the position at which the IO muscle was attached inferior/temporal to the lateral border of the inferior rectus (IR) as follows: (1) 7.0/2.0 mm (4 patients), (2) 6.0/2.0 mm (3 patients), (3) 5.0/2.0 mm (3 patients), (4) 4.0/2.0 mm (11 patients), (5) 3.0/0.0 mm (2 patients), and (6) 2.0/0.0 mm (3 patients). Recession and anteriorization were matched to vertical deviation in the primary position at far distance. Remaining diplopia, head tilt, vertical deviation (≤3 prism diopter (PD), excellent; 4-7 PD, good; and ≥ 8 PD, poor), upgaze limitation, and opposite vertical strabismus were evaluated. RESULTS: The average pre and postoperative 1-year vertical deviation angles in the primary position at far distance were 15.0 ± 5.6 PD and 1.2 ± 2.0 PD, respectively. At 1 year post-surgery, the vertical deviation angles were reduced by 6.8-21.0 PD from those at baseline. Few patients exhibited remaining head tilt, diplopia, upgaze limitation, or opposite vertical strabismus. Correction of hypertropia was excellent in 22 and good in 4 patients. CONCLUSIONS: Modified graded recession and anteriorization of the IO muscle is an effective surgical method for treating unilateral SOP. It exhibits good results and reduces the incidence of opposite vertical strabismus.

Rectus Pulley Displacements without Abnormal Oblique Contractility Explain Strabismus in Superior Oblique Palsy.

PURPOSE: Using high-resolution magnetic resonance imaging (MRI), we investigated whether rectus pulleys are significantly displaced in superior oblique (SO) palsy and whether displacements account for strabismus patterns. DESIGN: Prospective case-control study. PARTICIPANTS: Twenty-four patients diagnosed with SO palsy based on atrophy of the SO muscle on MRI and 19 age-matched orthotropic control subjects. METHODS: High-resolution, surface coil MRI scans were obtained in multiple, contiguous, quasicoronal planes during monocular central gaze fixation. Pulley locations in oculocentric coordinates in the following subgroups of patients with SO palsy were compared with normal results in subgroups of patients with SO palsy: unilateral versus bilateral, congenital versus acquired, and isotropic (round) versus anisotropic (elongated) SO atrophy. Expected effects of pulley displacements were modeled using Orbit 1.8 (Eidactics, San Francisco, CA) computational simulation. MAIN OUTCOME MEASURES: Rectus pulley positions and ocular torsion. RESULTS: Rectus pulleys typically were displaced in SO palsy. In unilateral SO palsy, on average the medial rectus (MR) pulley was displaced 1.1 mm superiorly, the superior rectus (SR) pulley was displaced 0.8 mm temporally, and the inferior rectus (IR) pulley was displaced 0.6 mm superiorly and 0.9 mm nasally from normal. Displacements were similar in bilateral SO palsy, with the SR pulley additionally displaced 0.9 mm superiorly. However, the lateral rectus pulley was not displaced in either unilateral or bilateral SO palsy. The SR and MR pulleys were displaced in congenital SO palsy, whereas the IR and MR pulleys were displaced in acquired palsy. Pulley positions did not differ between isotropic and anisotropic palsy or between patients with cyclotropia of less than 7° versus cyclotropia of 7° or more. Simulations predicted that the observed pulley displacements alone could cause patterns of incomitant strabismus typical of SO palsy, without requiring any abnormality of SO or inferior oblique strength. CONCLUSIONS: Rectus pulley displacements alone, without abnormal oblique muscle contractility, can create the clinical patterns of incomitant strabismus in SO palsy. This finding supports accumulating evidence that clinical binocular misalignment patterns are not reliable indicators of contractile function of the SO muscle. Ocular torsion does not correlate with and thus cannot account for pulley displacements in SO palsy.

Central Trochlear Palsy: Report of Two Patients With Ipsilesional Palsy and Review of the Literature.

BACKGROUND: The trochlear (fourth) nerve is the only cranial nerve that decussates before emerging from the posterior aspect of the brainstem. Lesions involving the trochlear nucleus or fascicles mostly give rise to contralesional superior oblique palsy (SOP). METHODS: We report 2 patients with SOP on the side of intraaxial lesions with a literature review on central trochlear palsy. RESULTS: The lesions are more commonly located posterior to the cerebral aqueduct in patients with ipsilesional SOP than in those with contralesional SOP. CONCLUSIONS: Intraaxial lesions may cause ipsilesional or contralesional SOP depending on the lesion location along the course of trochlear fascicle in the brainstem.

Treatment and diagnosis of congenital fourth nerve palsies: an update.

PURPOSE OF REVIEW: This review discusses recent advances in our understanding of the pathology, diagnosis, and treatment of congenital fourth nerve palsies. RECENT FINDINGS: High-definition MRI, which can now more accurately image the trochlear nerve, has increased our understanding of the pathology of fourth nerve palsies. A more sensitive two-step test is proposed to replace the three-step Parks-Bielschowsky test. Procedures strengthening the superior oblique tendon can be performed with a low incidence of secondary Brown syndrome. SUMMARY: Recent MRI studies have shown two pathological mechanisms associated with congenital superior oblique palsies. Superior oblique tuck combined with inferior oblique recession is a very effective way of eliminating head tilt secondary to congenital fourth nerve palsies.

Botulinum Toxin Injection for the Treatment of Third, Fourth, and Sixth Nerve Palsy: A Meta-Analysis.

The efficacy of botulinum toxin injection for the treatment of third, fourth, and sixth nerve palsy was evaluated. PubMed, Scopus, EMBASE, Web of Science, and Google Scholar databases were searched. Data about the duration of palsy (acute vs chronic), cause of the palsy, type of toxin used, mean dose, and other background characteristics were collected. Outcome variables were success rate (defined by alleviation of diplopia or reduction in eye deviation) and standardized mean difference of prism diopter and abduction deficit before and after injection. The Joanna Briggs Institute checklist was implemented for the risk of bias assessment. The analysis included 38 articles, comprising 643 patients. The overall treatment success rate in acute and chronic nerve palsy was 79% and 33%, respectively. The success rate was not significantly different between different subgroups of age, type of botulinum toxin, pre-injection prism diopter, etiology of the palsy, duration of follow-up, and mean dose of botulinum toxin injection. However, in both acute and chronic palsy, diabetes etiology was accompanied by the highest success rate. Overall symptomatic response to botulinum injection was 84% (95% CI: 67% to 96%), whereas functional response was observed in 64% (95% CI: 47% to 79%) of the patients. The odds ratio for the success rate of treatment of palsies with botulinum toxin versus expectant management was 2.67 (95% CI: 1.12 to 6.36) for acute palsy and 0.87 (95% CI: 0.17 to 4.42) for chronic palsy. Botulinum toxin can be used for the treatment of acute third, fourth, and sixth nerve palsy, especially in patients with acute palsy and more severe tropia. [J Pediatr Ophthalmol Strabismus. 2024;61(3):160-171.].

Effects of vertical muscle surgery on differences in the orientation of Listing's plane in patients with superior oblique palsy.

BACKGROUND: Although scleral search coils are widely and accurately used for the measurement of Listing's plane in both eyes, they require specialized equipment and are invasive. In this study, we describe a convenient and less invasive method that uses a synoptometer to analyze the differences in orientation of Listing's plane (difLP), and the effects of vertical muscle surgery on the difLP tilt in patients with superior oblique palsy (SOP). METHODS: Seventeen patients with unilateral congenital SOP (CSOP) and four patients with unilateral acquired SOP (ASOP) who had not undergone any strabismus surgeries were examined. Cyclodeviations of 13 vertical and horizontal gaze points within 30° were measured with a synoptometer, and the difLP tilts in the yaw and pitch planes were analyzed before and after vertical muscle surgery. RESULTS: The difLP tilt in the CSOP patients was significantly tilted nasally (p = 0.02) and forward on the lower side (p = 0.001), whereas that in ASOP patients tended to tilt temporally (p = 0.15). Ipsilateral inferior oblique recession (IOR) performed in seven CSOP patients tended to improve the difLP tilt in both the yaw (p = 0.07) and pitch (p = 0.09) planes, whereas contralateral inferior rectus recession (IRR) performed in three CSOP patients significantly improved the difLP tilt in the pitch plane (p = 0.015). The mean excyclodeviations in the 13 gaze points were significantly improved with both procedures (p < 0.0001 for both). CONCLUSIONS: The difLP tilt in the SOP patients could be analyzed with a convenient and less invasive method using a synoptometer, and dissimilar difLP tilts were confirmed in the ASOP and CSOP patients. The results of this study suggest that both IOR and IRR are reasonable treatments for improving the difLP tilt in CSOP patients. IOR should be selected for patients with a steep preoperative difLP tilt to the nasal side, whereas IRR should be selected for patients with a gentle preoperative difLP tilt.

Success of prisms in the management of diplopia due to fourth nerve palsy.

BACKGROUND: To analyze the success of prism use in alleviating diplopia in patients with fourth nerve palsy and to provide recommendations for prism prescription. METHODS: In this retrospective cohort study, the medical records of 83 patients who were prescribed prisms for symptomatic diplopia due to fourth nerve palsy were analyzed. Data on the nature and duration of diplopia, motility and alignment findings, and amount and type of prism prescribed were recorded. The success of prescribed prismatic correction was assessed by the patient's self-reporting of satisfaction with prism use and follow-up records. The main outcome measure was the satisfaction rate associated with the use of prisms (satisfaction score 1 or 2) in patients with fourth nerve palsy. RESULTS: There were 69 patients with congenital fourth nerve palsy and 14 patients with acquired fourth nerve palsy who received prisms. The mean primary position (± SD) deviation in this group was 7.8 (± 4.6) prism diopters (PD). The mean prism prescription was 6 (± 2.9) PD. Overall, 92% of patients were satisfied with the use of prisms. During the length of follow-up, which ranged from 2 months to more than 6 years (median: 18 months), 86% of the cohort continued using prisms while 14% of patients underwent strabismus surgery. Among 15 patients who had primary position deviation greater than 15 PD, 80% of the patients reported satisfaction with prisms, and in the 11 patients who received 10 PD or more of prismatic correction, 82% were satisfied. CONCLUSION: Prisms are an effective modality for the management of patients with symptomatic diplopia due to fourth nerve palsy. Even in patients with larger deviations including those who were prescribed greater than 10 PD of correction, the success rate of prisms in alleviating diplopia was high. Prisms should be considered as initial therapy in symptomatic patients with fourth nerve palsy.

Anterior transposition of the inferior oblique muscle in the treatment of unilateral superior oblique palsy.

PURPOSE: To determine whether unilateral inferior oblique anterior transposition alone could be an effective procedure for treating superior oblique palsy with inferior oblique overaction. METHODS: The records of 38 patients who underwent unilateral inferior oblique anterior transposition for unilateral superior oblique palsy with inferior oblique overaction were evaluated. A comprehensive ocular examination including best-corrected visual acuity measurements, ductions, versions, and deviations at near and distance, head tilt test, abnormal head position, dilated fundus examination, and Titmus test was performed prior to and after surgery. RESULTS: The mean patient age was 29 years, the mean follow-up was 32 months, the mean preoperative hypertropia in primary position was 14.29 ± 7.7 prism diopters (PD), and the mean inferior oblique overaction was 3.63 ± 0.67. Anterior transposition of the inferior oblique muscle was effective across a wide range of preoperative primary position hypertropia (4 to 35 PD) with a mean reduction in postoperative hypertropia of 12 PD. Inferior oblique overaction was reduced in all patients. No patient demonstrated postoperative primary position hypotropia. Surgery improved stereoacuity nearly two units using the Titmus stereoacuity scale. CONCLUSION: Anterior transposition of the inferior oblique muscle is effective in correcting inferior oblique overaction and primary position hypertropia in the treatment of unilateral superior oblique palsy.

Surgical management of Helveston syndrome (triad of A- pattern exotropia, superior oblique overaction and dissociated vertical deviation) using 'Four Oblique' procedure.

Purpose: To report the surgical outcomes in six patients of Helveston syndrome using a "four oblique" procedure. The popular methods for surgical management include superior rectus recessions alone or combined with superior oblique tenectomy. However, large angle exotropia correction would entail a higher risk of anterior segment ischemia when the superior rectus needs to be operated along with the horizontal recti. Hence, we evaluated the long-term results of this uncommon procedure. Methods: This was a retrospective review of six patients diagnosed to have manifest dissociated vertical deviation (DVD) with A pattern exotropia with bilateral superior oblique over action. All patients underwent horizontal muscle recessions/resections for exotropia along with bilateral posterior tenectomy of the superior oblique with inferior oblique anterior transpositioning. Results: The median age was 10 years (Range 5-26 years). The mean postoperative follow-up was 26 ± 14.02 months (Range 12-48 months). The mean reduction in exotropia was from 36.5 ± 21.06 PD (Range 15-65 PD) to 6.1 ± 3.06 PD (Range 3-10 PD). The procedure corrected the A pattern from a mean 23 ± 7 PD (Range 15-35 PD) to 7.6 ± 3.2 PD (Range 3-10 PD). The average DVD in the right eye reduced from 14 ± 4.3 PD (Range 8-20 PD) to 5.3 ± 1.2 PD and in the left eye from 14.33 ± 3.6 PD (Range 10-18 PD) to 4.1 ± 1.1 PD. The DVD asymmetry reduced from 6.33 ± 3.4 PD to 1.5 ± 1.3 PD. Conclusion: "Four oblique" procedure with horizontal muscle surgery seems to be an effective method for significantly correcting the A pattern as well as reducing the DVD with good long-term outcome in our case series.

Effect of diagnostic occlusion in acquired trochlear nerve palsy.

BACKGROUND: Monocular occlusion eliminates the stimulus for fusional vergence. Diagnostic occlusion may therefore be helpful in isolating the genuine profile of the fundamental ocular motility disorder, which may be an important finding regarding both differential diagnosis of strabismus and dosage of surgery. We investigated the effect of diagnostic occlusion on the motility pattern of acquired trochlear nerve palsy. PATIENTS AND METHODS: Forty-eight patients aged between 6 and 78 years (median 49 years) with unilateral trochlear nerve palsy were first examined without patching, and then after 3 days of diagnostic occlusion. The onset of palsy was 1-35 years before (median 2 years). Squint angles localized with a dark red glass in front of the non-paretic eye were measured at a distance of 2.5 m, using the Harms tangent screen. Vertical and cyclotorsional angles in primary position (PP), 25 degrees abduction of the non-paretic eye (adduction of the paretic eye), and 25 degrees downgaze were measured. RESULTS: The relation between hyperdeviation of the paretic eye and excyclodeviation (medians of the angles in degrees, ranges in brackets) before and after diagnostic occlusion was 5/5 and 4/6 (0;14/-1;10 and 0;19/2;13) in PP. In contralateral gaze, the relation was 8/5 and 8/6 (0;21/0;10 and 1;24/1;15), and in downgaze, 10/7 and 8/8 (0;21/1;14 and 0;23/3;18). The increase in excyclodeviation, though statistically significant (in PP, p = 0.0002) was small, with a median of 1 degree and large variability. The decrease in hyperdeviation was statistically significant in downgaze. The head-tilt phenomenon remained unchanged. CONCLUSIONS: In patients with trochlear nerve palsy, diagnostic occlusion regularly causes an increase in excyclodeviation. In 25% of patients, this increase exceeds 3 degrees. The more variable change in vertical deviation, and the lack in change in the head-tilt phenomenon, can be explained by the fact that central gain-modulation causing an increase in both vertical deviation and the head-tilt phenomenon is not reversible within the relatively short time of 3 days. Diagnostic occlusion can eliminate compensatory innervation and may thereby release the genuine motility pattern, but the occlusion can also induce artificial squint angles.

A new mechanism for Brown's syndrome.

This case report describes a child who developed an acquired bilateral sequential Brown's syndrome, confirmed each time intraoperatively, that is likely the result of a new mechanism not previously described in the literature. Arguments are provided to support the premise of a new mechanism and a new measure of relative trochlear position is suggested to further elucidate the role of "desagittalization" of the superior oblique tendon in the spectrum of superior oblique dysfunction.

Comparison of ocular torsion between congenital and acquired unilateral superior oblique palsy.

BACKGROUND/OBJECTIVES: To compare ocular torsion between congenital and acquired unilateral superior oblique palsy (USOP). SUBJECTS/METHODS: Retrospective review was performed on medical records of 163 USOP patients. Qualitative fundus torsional states in both eyes were determined based on locations of optic disc and fovea. Disc-fovea angles (DFA) were collected in both eyes for quantitative analysis. DFAs and the proportions of qualitative fundus torsional states in paretic and non-paretic eyes were compared between USOP patients and normal controls, and between congenital and acquired USOP patients. RESULTS: This study included 90 patients with congenital USOP, 73 patients with acquired USOP, and 66 normal controls. Most control subjects showed no torsion in both eyes (93.9%), whereas 61.1% of congenital and 46.5% of acquired USOP patients showed extorsion in either eye. More patients with congenital USOP showed fundus extorsion in the non-paretic eye (24.4% versus 12.3%) or both eyes (20.0% versus 6.8%), compared with patients with acquired USOP (P = 0.007). DFAs of paretic and non-paretic eyes were larger in USOP patients than in normal controls (P < 0.001, for both congenital USOP versus control and acquired USOP versus control). DFAs of non-paretic eyes were larger in congenital USOP patients than in acquired USOP patients (10.3° versus 8.5°, P = 0.018). CONCLUSIONS: Congenital USOP showed greater fundus extorsion in the non-paretic eye, compared with acquired USOP. Fundus photographs of both eyes are necessary to understand the ocular torsion in USOP patients and the variations in fundus torsion with varying USOP aetiology.

Isolated Bilateral Superior Rectii Paresis: A Rare Anomaly.

We present a case of bilateral isolated superior rectus paresis in a 13-year girl who presented with alternating exotropia and hypertropia. She demonstrated bilateral paresis of elevation in abduction with an overaction of both the contralateral yoke muscles, i.e. inferior obliques. Neuroimaging did not reveal a lesion along the pathway of the third nerve nor hypoplasia of the superior rectus muscle. We performed a bilateral lateral rectus recession on adjustable sutures with bilateral myectomy of the inferior obliques (weakening of contralateral yoke muscle). At 1 year, the patient is well aligned and happy. Isolated extraocular muscle pareses are rare events, which present occasionally to the strabismus surgeons and need to be looked out for if the patient's strabismus looks peculiar. We believe we are the first to report an isolated paresis of the superior rectus muscle in Pakistan.