Facial asymmetry in superior oblique muscle palsy and pulley heterotopy.

INTRODUCTION: Some observers have considered facial asymmetry as characteristic of congenital superior oblique muscle (SO) palsy. However, recent orbital imaging studies have determined that incomitant vertical strabismus resembling SO palsy can be caused by heterotopic rectus muscle pulleys. This finding suggests that facial asymmetry may predict the presence of abnormal orbital anatomy rather than be secondary to ocular torticollis. METHODS: Subjects who underwent orbital computed tomography or magnetic resonance imaging were divided into 5 groups based on clinical evaluation and previously established imaging criteria: (1) congenital SO palsy; (2) acquired SO palsy; (3) strabismus with pulley heterotopy; (4) strabismus without SO palsy or pulley heterotopy; and (5) orthotropic subjects. Frontal photographs were digitized and the following 3 facial morphometric features recorded: (1) angle of inclination of each orbit; (2) relative facial size; and (3) facial angle. RESULTS: The 79 subjects who underwent imaging were divided into the 5 groups as follows: 6 with congenital SO palsy; 7 with acquired SO palsy; 20 with pulley heterotopy; 26 with strabismus without SO palsy or pulley heterotopy; and 20 control subjects. All subjects with either congenital or acquired SO palsy had torticollis. Multivariate analysis demonstrated no significant differences in any of the 3 facial morphometric features among any of the groups. CONCLUSION: Facial asymmetry as assessed by these 3 morphometric features is not useful in distinguishing between congenital SO palsy or pulley heterotopy and other acquired forms of strabismus. This finding casts doubt on the relationship between ocular torticollis and facial asymmetry.     

A 12-year, prospective study of extraocular muscle imaging in complex strabismus

INTRODUCTION: Diagnostic imaging by magnetic resonance imaging (MRI) or computed x-ray tomography (CT) has become the standard of care in many medical fields. Clinical imaging of the extraocular muscles (EOMs) can now provide insight into some causes of strabismus, in some cases challenging traditional concepts of etiology and suggesting alternative treatments. METHODS: Between 1990 and 2001, 62 orthotropic volunteers and 261 strabismic patients underwent orbital imaging under a prospective protocol. Surface coil MRI was performed with fixation control with slice thickness of 1.5 to 3 mm; CT was performed with 1-mm slice thickness. Images were correlated with ophthalmological examinations. RESULTS: MRI was performed in 267 and CT in 56 subjects. Comparison with normal orbits commonly demonstrated abnormalities of EOM size or location in strabismic patients. These included absence (5 patients) or atrophy (33 patients) of the superior oblique (SO) muscle in SO palsy; abnormalities of the trochlea or SO tendon in Brown's syndrome (8 patients); heterotopy of the rectus pulleys associated with incomitant strabismus (46 patients), including instability of pulleys (9 patients); trauma to rectus EOMs (16 patients); atrophy of the lateral rectus (10 patients), inferior rectus (4 patients), medial rectus (4 patients), superior rectus (4 patients), and inferior oblique (1 patient) muscles; and EOMs disinserted by scleral buckles (3 patients). EOM abnormalities correlated closely with clinically abnormal patterns of ocular motility. CONCLUSIONS: With the appropriate technique, EOM imaging is a valuable adjunct in clinical evaluation of complex strabismus. Because imaging can provide unique information unavailable from the clinical examination alone, it should be performed when indicated to evaluate patients with strabismus more complex than concomitant esotropia and exotropia.     

Comparison of Muscle Volume Between Congenital and Acquired Superior Oblique Palsies by Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) studies of superior oblique (SO) muscles have revealed a high incidence of SO muscle atrophy/hypoplasia in congenital SO palsy patients. It has also been reported that long-standing acquired SO palsy patients show atrophic SO muscles in the affected eye. The purpose of this study was to compare the incidence of SO muscle atrophy/hypoplasia in congenital and acquired SO palsy by utilizing MRI. Coronal MRI image planes were taken from 29 cases of unilateral congenital SO palsy and 9 cases of acquired unilateral SO palsy patients. The SO muscle bellies were traced and their sizes were measured from each image plane. The total volume of the affected superior oblique muscle was compared with that of the normal fellow eye. The mean volume of the affected superior oblique muscle to that of the normal muscle was 45.3% (SD = 30.1) in the congenital group and 65.8% (SD = 22.7) in the acquired group. The volume reduction of the SO muscle in congenital SO palsy patients appears to be mainly a congenital abnormality rather than a secondary change, as seen in acquired SO palsy patients.     

Orbital imaging demonstrates occult blow out fracture in complex strabismus.

BACKGROUND: While strabismologists are familiar with diagnostic evaluation of suspected blow out fractures, unsuspected blow out fractures may further complicate difficult cases of strabismus not clinically supposed to be related to orbital trauma. METHODS: According to a prospective protocol, we studied five adults presenting with diplopia, and one with convergence-related asthenopia. No patient recalled or had any clinical suspicion of orbital fracture at initial evaluation. Surface coil magnetic resonance imaging of the orbits was performed at 312 microm resolution, slice thickness 2 mm. Quasicoronal images in central gaze were supplemented with eccentric gaze positions, and sagittal and axial images as indicated. RESULTS: Five patients had incomitant hypertropia, and one had abducens paralysis. Magnetic resonance imaging disclosed previously unsuspected blow out fractures in all six patients. Three patients had medial wall fracture, one bilaterally. Two patients had inferior wall fractures, and one inferomedial. Although only one patient had an extraocular muscle displaced into a sinus, all had evidence of orbital connective tissue distortion in the region of the rectus extraocular muscle pulleys influencing muscle paths. These effects altered the presentations of more familiar pathologies such as superior oblique palsy. After learning of the MRI findings, most patients then recalled orbital trauma from as early as childhood. CONCLUSION: Unsuspected blow out fractures occur and may confound the usual findings in complex strabismus. High-resolution orbital imaging can detect blow out fractures and clarify the pathophysiology, enabling appropriate surgical management.     

High-resolution magnetic resonance imaging demonstrates abnormalities of motor nerves and extraocular muscles in patients with neuropathic strabismus.

INTRODUCTION: Although the ocular motility examination has been used traditionally in the diagnosis of strabismus that is a result of cranial nerve (CN) abnormalities, magnetic resonance imaging (MRI) now permits the direct imaging of lesions in CN palsies. METHODS: Prospectively, nerves to extraocular muscles (EOMs) were imaged with T1 weighting in orbits of 83 orthotropic volunteers and 96 strabismic patients in quasicoronal planes using surface coils. Intraorbital resolution was 234-312 microns within 1.5- to 2.0-mm thick planes. CNs were imaged at the brainstem using head coils and T2 weighting, yielding 195 micron resolution in planes 1.0-mm thick in 6 normal volunteers and 22 patients who had oculomotor (CN3), trochlear (CN4), or abducens (CN6) palsies and Duane syndrome. RESULTS: Oculomotor (CN3) and abducens (CN6) but not trochlear (CN4) nerves were demonstrable in the orbit and skull base in all normal subjects. Patients with congenital CN3 palsies had hypoplastic CN3s both in orbit and skull base, with hypoplasia of involved EOMs. Patients with chronic CN6 and CN4 palsies exhibited atrophy of involved EOMs. Patients with Duane syndrome exhibited absence or hypoplasia of CN6 in both orbit and brainstem regions, often with mild hypoplasia and apparent misdirection of CN3 to the lateral rectus muscle. Unlike CN6 palsy, patients with Duane syndrome exhibited no EOM hypoplasia. Patients with congenital fibrosis exhibited severe hypoplasia of CN3, moderate hypoplasia of CN6, and EOM hypoplasia, particularly severe for the superior rectus and levator muscles. CONCLUSION: High-resolution MRI can directly demonstrate pathology of CN3 and CN6 and affected EOM atrophy in strabismus caused by CN palsies. Direct imaging of CNs and EOMs by MRI is feasible and useful in differential diagnosis of complex strabismus.     

Anterior and nasal transposition of the inferior oblique muscles in patients with missing superior oblique tendons.

INTRODUCTION: Patients with missing superior oblique (SO) tendons present with overelevation/underdepression in adduction. Unilateral cases often exhibit abnormal head postures, whereas in bilateral cases, there may be a marked V-pattern with upgaze exotropia. These patients may have craniosynostosis. METHODS: Nine children with unilateral (n = 2) or bilateral (n = 7) absent SO tendons underwent anterior and nasal transposition of the inferior oblique (IO) muscles, some in combination with horizontal rectus recession for horizontal strabismus. They were evaluated 6 to 46 months postoperatively for alignment and oculomotor examination. Cyclodeviations were not evaluated in most children. RESULTS: Postoperatively, all patients improved. Both unilateral cases were orthotropic with no abnormal head posture. In the bilateral cases, vertical deviation in adduction and exotropia in upgaze had largely cleared, although some symptoms remained, most notably vertical deviation in side gaze (3 patients) and V-pattern esotropia in downgaze (2 patients). A patient missing both SO tendons as well as the left superior rectus muscle, who had the anterior and nasal transposition on the right side only, remained with 25(Delta) left hypotropia. CONCLUSIONS: Anterior and nasal transposition of the IO muscle reduces overelevation in adduction and helps eliminate or reduce divergence of the eyes in upgaze, but esodeviation may persist in downgaze. This procedure was most effective in unilateral absence of the SO tendon. It is likely to benefit patients with severe congenital fourth nerve palsy in which standard IO muscle weakening procedures have been ineffective.     

Superior oblique muscle involvement in thyroid ophthalmopathy.

BACKGROUND: Rectus muscle involvement in thyroid ophthalmopathy is well documented. The inferior rectus is the most frequently involved, followed by the medial, superior, and infrequently the lateral rectus. This study reports involvement of the superior oblique muscle as a contributory cause of restrictive strabismus in patients with thyroid ophthalmopathy. METHODS: This is a retrospective review of four patients with known thyroid ophthalmopathy who presented with incomitant vertical strabismus, A-pattern, overdepression in adduction, underelevation in adduction, and incyclotorsion. All patients underwent preoperative orbital imaging. Two of the four patients had previous orbital decompressions. All patients underwent surgery on the SO muscle. RESULTS: Preoperative scans showed enlargement of one or both SO muscles in all patients and intraoperative forced duction testing revealed restriction to elevation in adduction in all cases. Preoperative A-pattern ranged from to 6 to 22 prism diopters. All subjects had preoperative incyclotorsion, ranging from 2 and 14 degrees. Improvement of the versions, hypertropia, and cyclotorsion followed surgical weakening procedures on the SO muscle. CONCLUSION: Thyroid ophthalmopathy may involve the SO muscle. Clinical manifestations include preoperative A-pattern strabismus, incyclotorsion, and restrictive limitation to elevation in adduction. Orbital imaging documents SO muscle enlargement. Awareness of SO involvement in thyroid ophthalmopathy assists the surgeon to develop a more precise surgical strategy to correct the hypotropia.     

Extraocular muscle imaging in complex strabismus.

BACKGROUND AND OBJECTIVE: Abnormalities of extraocular muscle are an unusual cause of complex strabismus. The traditional evaluation based on clinical examinations is insufficient for the interpretation of incomitant motility disorders resulting from extraocular muscle anomalies. Extraocular muscle imaging by computed x-ray tomography (CT) or magnetic resonance imaging (MRI) can provide useful information for diagnosis, pathophysiology, and treatment of complex strabismus. PATIENTS AND METHODS: Five cases of complex strabismus resulting from congenital anomalies of the extraocular muscles and their successful evaluation using extraocular muscle imaging are described. RESULTS: Orbital CT or MRI scan was obtained in five patients who had unusual incomitant strabismus. It confirmed the diagnosis of the absence of the medial rectus muscle, accessory lateral rectus muscle, atrophy of the inferior or both superior and medial rectus muscles, and abnormal thickening of the levator palpebrae superioris and superior rectus muscle. CONCLUSIONS: Extraocular muscle imaging is a useful technique for evaluating anatomic abnormalities. It should be considered when evaluating patients with atypical strabismus.     

Flap tear of rectus muscles: an underlying cause of strabismus after orbital trauma

PURPOSE: To present an avulsion injury of the rectus muscle after orbital trauma, usually the inferior rectus, and detail its diagnosis and operative repair. METHODS: Forty-three patients underwent repair of flap tears of 62 rectus muscles. During surgery, we found the muscle abnormality was often subtle, with narrowing or thinning of the remaining attached global layer of muscle. The detached flap of external (orbital) muscle was found embedded in surrounding orbital fat and connective tissue. Retrieval and repair were performed in each case. RESULTS: The causes of orbital trauma were as follows: orbital fractures (15 patients), blunt trauma with no fracture (11 patients), suspected trauma but did not undergo computerized tomographic scan (12 patients), and status after retinal detachment repair (5 patients). Of note, 15 of the 43 patients (35%) underwent repair of the flap tear alone, without any additional orbital or strabismus surgery. Diagnostically, the predominant motility defect in 45 muscles was limitation toward the field of action of the muscle, presumably as a result of a tether created by the torn flap; these tethers simulated muscle palsy. Seventeen muscles were restricted away from their field of action, simulating entrapment. The direction taken by the flap during healing determined the resultant strabismus pattern. All patients with gaze limitation toward an orbital fracture had flap tears. The worst results after flap tear repair were seen in patients (1) who had undergone orbital fracture repair before presentation, (2) who had undergone previous attempts at strabismus repair, and (3) who had the longest intervals between the precipitating event and the repair. The best results were obtained in patients who underwent simultaneous fracture and strabismus repair or early strabismus repair alone. CONCLUSIONS: Avulsion-type flap tears of the extraocular muscles are a common cause of posttraumatic strabismus. Early repair produces the best results, but improvement is possible despite long delay.     

麻痹性斜视183例临床分析

目的:探讨近年来麻痹性斜视的病因、麻痹肌分布和对视功能的影响。方法:对我院2009-03/2012-03住院行斜视矫正术的183例麻痹性斜视患者的病历资料进行回顾性研究。结果:先天性麻痹性斜视占80.87%,后天性麻痹性斜视占19.13%;原因不明者最多(77.60%),其次为外伤(14.21%)。垂直斜视中上斜肌麻痹占81.19%,下直肌麻痹占8.26%,上直肌麻痹占6.88%,下斜肌麻痹占2.29%,双上转肌麻痹占0.92%,双下转肌麻痹占0.46%。水平斜视中外直肌麻痹占54.17%,内直肌麻痹占45.83%。166例患者术前进行同视机检查,有双眼视功能患者占28.92%。结论:麻痹性斜视病因复杂,眼外肌中上斜肌最常累及,对双眼视功能有明显的影响,应尽早进行手术治疗。     

Congenital absence of the inferior rectus muscle--diagnosis and management.

BACKGROUND: Congenital absence of the inferior rectus muscle is a rare cause of apparent inferior rectus palsy especially in the absence of associated cranial facial anomalies. METHODS: We report three cases of isolated congenital absence of the inferior rectus muscle and its successful surgical management. RESULTS: Failure of the normal embryologic development of the mesodermal complex around the eye can lead to agenesis of the extraocular muscles. In apparent palsies of the inferior rectus muscle and no definite cause, a high index of suspicion and orbital imaging can confirm the diagnosis of congenitally absent inferior rectus preoperatively. Surgical correction may involve inferior transposition of the horizontal rectus muscles. CONCLUSIONS: Although rare, congenital absence of the inferior rectus muscle is a possible cause of apparent inferior rectus muscle palsy particularly in the absence of another identifiable cause. Strabismus surgery in conjunction with intramuscular botulinum toxin injection can offer significant improvement in function and cosmesis of these patients.     

Paralytic strabismus

In the last year, published works on paralytic strabismus have concerned many topics. New advances have been made in the knowledge of epidemiology of ocular nerve palsies in children, muscular causes of paralytic strabismus, and neuroimaging management of patients with third nerve palsy who are at risk of cerebral aneurysms. The author describes reports on rare associations of oculomotor imbalances and neurologic diseases as well as atypical orbital localizations of tumors. He also discuss new neuroimaging findings in congenital superior oblique muscle palsy and new acquisitions on cyclofusion deterioration in acquired trochlear palsy.     

The retinopathy in neuronal ceroid-lipofuscinoses in comparison to retinitis pigmentosa – Workshop held at Bad Horn,Switzerland, March 1-2, 1997

Abstract

Purpose: We analyzed findings of orbital and cranial magnetic resonance imaging (MRI) in patients with congenital fibrosis of the extraocular muscles (CFEOM). We described surgery and its outcome.

Material and method: Nine out of 10 patients with clinical findings of CFEOM underwent orbital and cranial MRI to perform a study of the extraocular muscles and cranial nerves. A multimodality workstation platform developed by the imaging laboratory of our hospital for PC computer allowed us to visualize and measure the cross sections of the extraocular muscles in a coronal section. Surgery was indicated to resolve strabismus. Outcome was considered favorable if the final deviation was <10?pd in the primary position without head turn.

Results: In 8 cases (6 males, 5 unilateral [3 left eye]), MRI revealed atrophy of at least 1 of the extraocular muscles supplied by the third nerve. Five patients had third nerve aplasia or hypoplasia. Clinical findings were compatible with a probable diagnosis of CFEOM in all 10 patients. Four patients underwent ptosis surgery before being diagnosed with CFEOM. Four patients underwent surgery to correct strabismus and, of these, 2 required multiple interventions (1 needed 4 interventions). Outcome was successful in only 2 cases.

Conclusion: Orbital and cranial MRI provided useful information about extraocular muscles and cranial nerves in CFEOM. Surgery must be performed on an individual basis; the number of reoperations is high. The outcome of surgery was favorable in half of the cases.     

Rectus muscle orbital wall fixation: a reversible profound weakening procedure.

INTRODUCTION: Surgical treatment of third nerve palsy, sensory exotropia and strabismus secondary to anomalous innervation of the rectus muscles, frequently require large rectus muscle recessions in an attempt to maintain alignment in the primary position and reduce the effects of misinnervation. The aim of this study was to describe and evaluate the results of inactivation of a rectus muscle by its attachment to the adjacent orbital wall. METHODS: Seven subjects diagnosed with third-nerve palsy (three cases), Duane syndrome (two cases), sensory exotropia (one case), and congenital aberrant innervation of vertical rectus muscles (one case) underwent rectus muscle inactivation by orbital wall fixation. The rectus muscle was disinserted from the globe and reattached to the adjacent orbital periosteum using non-absorbable sutures. This surgery was performed on the lateral rectus muscle in six subjects, and surgery was performed on both ipsilateral vertical rectus muscles in one. RESULTS: Postoperatively four of six patients were aligned within 12 prism diopters of orthotropia in primary position. All patients had improvement of the anomalous head posture. In Duane syndrome, lateral rectus inactivation markedly reduced co-contraction and globe retraction. No overcorrections resulted. CONCLUSION: A rectus muscle may be functionally inactivated when its insertion is attached to the orbital periosteum. Advantages of this procedure over extirpation and free tenotomy include permanent disinsertion of the muscle from globe and reversibility.     

High-resolution magnetic resonance imaging demonstrates varied anatomic abnormalities in Brown syndrome.

INTRODUCTION: Although Brown syndrome classically is considered to be limited to the SO tendon sheath and trochlea, it does not always respond to SO surgery. We investigated mechanisms of Brown syndrome by magnetic resonance imaging (MRI). METHODS: Three patients with congenital and 8 with acquired Brown syndrome were compared with matched normal subjects under a prospective protocol of high-resolution, multipositional orbital MRI using surface coils. Muscle size and contractility were determined using digital image analysis. RESULTS: Five of 8 patients with acquired Brown syndrome had a history of trauma or surgery and demonstrated extensive scarring, avulsion, or fracture of the trochlea. One of the 8 had a cyst in the SO tendon. One congenital and one acquired case demonstrated inferior displacement of the lateral rectus (LR) pulley in adduction, with a normal SO tendon-trochlear complex. Such cases of Brown syndrome responded to surgical stabilization of the LR pulley. Two congenital cases had clinical findings of ipsilateral SO palsy confirmed on MRI by atrophy or absence of the SO belly. In congenital absence of the SO belly, the anterior tendon was present but terminated directly on the trochlea. CONCLUSION: High-resolution MRI demonstrates a variety of abnormalities in patients presenting with Brown syndrome, including atrophy or absence of the SO belly. Management in Brown syndrome should be tailored to the pathophysiology of the individual patient.     

Superior oblique palsy with class III tendon anomaly

PURPOSE: To describe the clinical findings and surgical results of superior oblique palsy with class III tendon anomaly. DESIGN: Observational case series. METHODS: One hundred and forty-one cases of congenital and idiopathic superior oblique palsy were operated on by one surgeon (M.S.) between September 1, 1995 and August 31, 2007. The superior oblique tendons were explored in 26 cases. Among these, five cases were found to have the distal end of the tendon inserted into the Tenon capsule. Preoperative eye alignment, visual acuity, stereopsis measured with Titmus stereo acuity tests (Stereo Fly SO-001; Stereo Optical Co, Chicago, Illinois, USA), and magnetic resonance imaging findings were collected from the patients' records. Main outcome measures included preoperative eye position, surgical results, and stereoscopic acuity. Stereopsis and the amount of vertical deviation were compared in cases with class I, II, and IV tendon anomalies. RESULTS: A total of eight surgeries were performed on five patients with class III superior oblique tendon anomaly. Three muscles were operated on for each patient. The amount of vertical deviation was not significantly different from other types of tendon anomaly. Patients with class I to III tendon anomalies obtained good stereopsis after strabismus surgery, whereas cases with class IV anomaly achieved only limited stereopsis. The number of surgeries performed was significantly higher in cases with class IV anomaly. CONCLUSIONS: Without careful search of the Tenon capsule, the condition can be misdiagnosed as an absent tendon. Strengthening the superior oblique tendon in the Tenon capsule can improve the alignment significantly.     

Congenital microphthalmos with orbital cysts: distinct diagnostic features and management

PURPOSE: To review the clinical features and treatment strategies for microphthalmic globes with orbital cyst. METHODS:: The clinical records of 23 patients treated for microphthalmos associated with orbital cysts were reviewed retrospectively. RESULTS: Most cases of congenital microphthalmos with orbital cysts were first noted at birth, and all were confirmed by means of computed tomography and/or ultrasonography. Six of the 23 cases were bilateral. Sixty-seven percent of bilateral and 29% of unilateral cases also had other congenital malformations. Mild microphthalmos was noted in 3 orbits, moderate in 16 orbits, and severe in 10 orbits. On the basis of clinical findings, 8 orbits were treated with enucleation and cyst excision and 15 were treated with cyst excision only. Cyst aspiration was performed on 5 orbits; 2 required aspiration and subsequent cyst excision. Twenty-six orbits had good cosmesis and 2 had acceptable cosmesis. The mean follow-up interval was 5.15 years. CONCLUSIONS: Management of microphthalmos with orbital cyst is a cosmetic issue. Cyst size, degree of microphthalmos, and general condition of the patient determine the best treatment approach.     

Ocular Overelevation in Adduction in Craniosynostosis: Is It the Result of Excyclorotation of the Extraocular Muscles?

PURPOSE: We sought to determine whether radiological evidence supports excyclorotation of the extraocular muscle cone as a cause of overelevation in adduction in children with craniosynostosis. METHODS: This was a retrospective case series of 40 patients with craniosynostosis. Ophthalmic findings were assessed for incomitant vertical strabismus in particular excessive elevation in adduction. Computed tomography and magnetic resonance imaging scans were reviewed. Those scans with adequate coronal imaging of their orbits to assess the position and angulation of the horizontal extraocular muscles were identified, and the degree of rotation of the muscles formally measured along with aged matched controls. These groups were analyzed for the association between presence of overelevation in adduction and degree of excyclorotation of the extraocular muscle cone. RESULTS: The identified updrift on adduction that mimics inferior oblique muscle overaction was present in 63% (25/40) of patients. Imaging that permitted accurate measurement of the muscles positions was available in 10 of the 40 patients. Of these 10, 8 had the updrift, and 7 of these 8 (88%) demonstrated more excyclorotation than their aged matched controls. Comparison of scan measurements of patients revealed a significant difference in degree of excyclorotation (mean difference = 16.2, 95% confidence interval 6.2-31.5; P = 0.006) between patients with and without excess elevation in adduction. CONCLUSION: Overelevation in adduction is significantly associated with excyclorotation of the extraocular muscle cone in children with craniosynostosis. We demonstrate a simple method to assess for the excyclorotation. Our findings support the importance of imaging of the orbits in these children before strabismus surgery.     

The efficacy of superior oblique split Z-tendon lengthening for superior oblique overaction.

PURPOSE: To evaluate the efficacy of superior oblique muscle split Z-tendon lengthening in the treatment of superior oblique muscle overaction with respect to normalization of superior oblique ductions and versions, reduction of A-pattern strabismus and correction of vertical deviations. In addition, to determine the incidence of complications of the procedure including overcorrection and the effect of the procedure on horizontal deviation. METHODS: A retrospective review was performed of 19 patients who underwent superior oblique muscle split Z-tendon lengthening for A-pattern strabismus or significant vertical deviation associated with superior oblique overaction between June 1980 and September 1999. Ten males and 9 females were included, ranging in age from 2 to 45 years (mean: 9 years). Patients underwent either a unilateral or bilateral superior oblique tendon lengthening based on the patient's clinical picture. RESULTS: Ten of 11 patients (91%) who underwent unilateral tendon lengthening and 10 of 16 eyes (63%) that underwent bilateral superior oblique tendon had complete normalization of superior oblique action. Seven of 10 patients (70%) who underwent unilateral or bilateral tendon lengthening for a clinically significant A-pattern had the A-pattern completely eliminated or brought to a clinically insignificant level. All 8 patients who underwent a unilateral tendon lengthening for a clinically significant vertical deviation had reduction of the vertical deviation. There was no statistically significant effect of either the unilateral or bilateral procedure on horizontal deviation. CONCLUSIONS: The superior oblique muscle split Z-tendon lengthening procedure is highly effective for normalization of superior oblique muscle function and reduction of A-pattern strabismus and vertical deviations associated with superior oblique muscle overaction.