Magnetic resonance imaging findings of age-related distance esotropia in Japanese patients with high myopia

Purpose This study aimed to investigate the characteristics of the extraocular muscles and the orbital connective tissue pulleys in Japanese patients with age-related distance esotropia (ARDE) and high myopia using magnetic resonance imaging (MRI). Methods This was a retrospective case-series study. High-resolution coronal MRI scans of 12 orbits were obtained in 6 patients with ARDE and high myopia (age range: 51–69 years). We analyzed the images to determine the positions of the rectus muscle pulleys relative to the center of the globe, the integrity of the lateral rectus-superior rectus muscle (LR-SR) band, and the LR angle (the angle between the major axis of the LR and the vertical plane). Results The distance esotropia ranged from 4 to 25∆, and 3 cases exhibited vertical deviations. The mean (±standard deviation (SD)) axial length was 28.5 (± 1.6) mm. The mean positions of the medial rectus muscle pulley and LR pulley were 1.3 mm inferior and 1.4 mm inferior, respectively, to those seen in the normal control group in our previous study (P = 0.002 and P = 0.05, respectively). All 12 orbits had abnormal elongated LR-SR bands, and 8 orbits (67%) displayed ruptured LR-SR bands. The LR angle (mean±SD; 18.8° ± 8.5°) increased significantly with the inferior displacement of the LR pulley (R2 = 0.77, P = 0.0002). Conclusions Inferior displacement of the LR pulley and abnormal LR-SR bands were seen in Japanese ARDE patients with high myopia, as was found in ARDE patients without high myopia. The LR angle might be useful for judging the degree of LR pulley displacement

Absence of Relationship between Oblique Muscle Size and Bielschowsky Head Tilt Phenomenon in Clinically Diagnosed Superior Oblique Palsy

PURPOSE. To study whether the variation in maximum oblique muscle size accounts for individual variation in the Bielschowsky head tilt phenomenon (BHTP) in clinically diagnosed superior oblique (SO) palsy. METHODS. Seventeen subjects with clinically diagnosed earlyonset or idiopathic SO palsy and 14 normal subjects were enrolled in the study. Magnetic resonance imaging (MRI) in coronal and sagittal planes was used for quantitative morphometry of inferior oblique (IO) and SO muscles. Maximum crosssectional area of the SO and IO cross section at the mid-inferior rectus crossing were determined in central gaze and compared with paretic eye hypertropia on ipsilesional versus contralesional head tilt. RESULTS. Mean (ϮSD) maximum SO cross section was 18.1 Ϯ 3.2 mm 2 in normal subjects, 14.2 Ϯ 6.8 mm 2 ipsilesional to SO palsy, and 19.2 Ϯ 4.5 mm 2 contralesional to SO palsy. The ipsilesional SO cross section was significantly smaller than the contralesional (P ϭ 0.004) and normal (P ϭ 0.01) ones. The mean IO cross section was 18.3 Ϯ 3.5 mm 2 in normal subjects, 21.3 Ϯ 7.9 mm 2 ipsilesional to SO palsy (P ϭ 0.43), and 22.0 Ϯ 6.7 mm 2 contralesional to SO palsy (P ϭ 0.26). Hyperdeviation varied with head tilt by 20.1 Ϯ 5.5°in subjects with SO atrophy, and 10.3 Ϯ 5.6°in subjects without SO atrophy (P ϭ 0.003). Although oblique muscle cross sections did not correlate with BHTP, subjects with clinically diagnosed SO palsy segregated into groups exhibiting normal versus atrophic SO size. CONCLUSIONS. SO size does not account for the variation in BHTP in clinically diagnosed SO palsy, supporting the proposition that the BHTP is nonspecific for SO function. (Invest Ophthalmol Vis Sci. 2009;50:175-179) DOI:10.1167/iovs.08-2393 P atients with early onset or idiopathic superior oblique (SO) palsy are heterogeneous. Only when orbital imaging shows a large asymmetry in cross-sectional areas of the SO muscles is actual muscle weakness 1-4 likely. SO palsy may not necessarily be neuropathic, because abnormalities of the SO tendon, 5-8 or of orbital pulleys may cause incomitant vertical strabismus mimicking SO palsy. 9,10 For this reason, the gold standard for the diagnosis of SO palsy is ultimately radiographic. Nevertheless, much clinical literature on SO palsy is based on clinical, not radiographic, criteria. If clinical criteria are nonspecific for SO palsy, then some beliefs about SO palsy may benefit from reexamination. The Bielschowsky head tilt phenomenon (BHTP) consists of a greater hypertropia during head tilt to the ipsilesional than contralesional shoulder in patients seated upright and is used as a clinical lateralizing test for SO palsy. The biomechanical basis of the BHTP is not fully understood, but probably includes loss of downward and intorsional torque of the palsied SO in compensatory ocular counterrolling (OCR). 11 The BHTP is considered by many clinicians to be the defining clinical criterion for SO palsy. Oblique muscles have both vertical and torsional actions. Contractility of the SO can be radiographically determined by evaluating the change in SO cross-sectional area during gaze shift from supraduction to infraduction. In patients with SO palsy, SO contractility is well correlated with maximum SO cross-sectional area in central gaze. 12 Further, MRI evidence of SO muscle contractile change in vertical gaze shift resembles similar MRI findings during ocular counterrolling. 13 During static ocular counterrolling, 13 the posterior SO cross section was found to be greater during head tilt to the ipsilateral than the contralateral side, reflecting SO contraction to implement ocular torsion. 2 Because changes in SO cross section due to vertical duction resemble changes associated with OCR, we sought to analyze whether variation in SO size accounts for variation in BHTP in SO palsy. Recognizing that maximum SO cross-sectional size in the central gaze is highly correlated with SO contractility, 12 we supposed that the BHTP would also correlate with SO size if this diagnostic test directly reflects SO function. METHODS Subjects Subjects with clinically diagnosed congenital or idiopathic SO palsy, including presumably decompensated cases, were recruited from a prospective study of extraocular muscle function at Okayama University Hospital. The subjects agreed to participate and gave written informed consent according to a protocol conforming to the tenets of the Declaration of Helsinki. Diagnosis of SO palsy was based on clinical criteria including: ipsilesional hypertropia greater in the contralesional than the ipsilesional version, and greater during head tilt to the ipsilateral than the contralateral shoulder when seated upright (Bielschowsky head tilt test); a deficit in infraduction when the ipsilesional eye was adducted; and results of Hess screen testing performed by strabismologists confirming greater hypertropia in deorsumversion and V pattern. All participants underwent complete ophthalmic examinations, including measurement of heterophorias with prism and cover testing. The BHTP was defined quantitatively to be the difference From th

Clinical Parameters Reflecting Globe/orbit Volume Imbalances in Japanese Acquired Esotropia Patients with High Myopia but without Abduction Limitations

In high myopia, eye dislocation due to increased globe volume or tight orbital volume causes acquired esotro-pia. GOR (globe/orbit volume ratio), an indicator of the degree of progression of this pathology, was investi-gated the relationships among easily obtained clinical parameters. In this retrospective study, 20 eyes from 10 acquired esotropia patients with high myopia but without abduction limitations were examined. The mean age of the patients was 63.7 ± 8.2 years (mean ± standard deviation). Volumes were measured on the three-dimen-sional fast imaging employing steady-state acquisition magnetic resonance imaging images using the vol-ume-measurement function. Correlations between GOR and the displacement angle of the globe (DA), axial length (AL), and equatorial diameter (ED) were investigated. Mean DA, AL, ED, and GOR values were 107.5 ± 8.5°, 28.86 ± 1.92 mm, 25.00 ± 1.16 mm, and 0.36 ± 0.05, respectively. Only AL was correlated with GOR (p < 0.0001, R2 = 0.6649); DA (p = 0.30, R2 = 0.0633) and ED (p = 0.91, R2 = 0.0008) were not. AL was the only clinically available parameter to indicate globe/orbit volume imbalances in acquired esotropia with high myopia but without abduction limitation. AL may be important for the clinical assessment of the progression of this pathology

Congenital Multiple Ocular Motor Nerve Palsy Complicated by Splitting of the Lateral Rectus Muscle

We report a case of congenital multiple ocular motor nerve palsy combined with splitting of the lateral rectus muscle (LR). A 59-year-old Japanese female was investigated for worsening esotropia after corrective surgery. She presented with left hypertropia (35Δ) and esotropia (45-50Δ). Orbital magnetic resonance imaging (MRI) showed reduced belly sizes in the superior rectus, inferior rectus, and superior oblique muscles and splitting of the LR, extending from the origin to the belly, in the left eye. Splitting of the LR belly was detected on MRI in a case of congenital multiple ocular motor nerve palsy

Shape analysis of rectus extraocular muscles with age and axial length using anterior segment optical coherence tomography

Purpose This study aimed to evaluate the shape of the extraocular muscles (EOMs) in normal subjects using the en-face images of anterior segment optical coherence tomography (AS-OCT). The EOM insertion and the direction of the muscle fibers were investigated. Subjects and methods A total of 97 healthy normal subjects (194 eyes) at Okayama University Hospital (age, 47.1±21.5 years; range, 8–79 years) participated in the study. A series of 256 tomographic images of the rectus EOMs were captured using the C-scan function of the AS-OCT (CASIA2, TOMEY Co., Japan), and the images were converted to en-face images in multi-TIFF format. The anterior chamber angle to EOM insertion distance (AID) and the angle of the muscle fibers from the insertion site (angle of muscles) were measured from the images. The correlations of AID and angle of muscles with age and axial length were investigated and evaluated. Results AID and angle of muscles were significantly correlated with age or axial length in some EOMs. The AIDs of medial rectus (MR) (P = 0.000) and superior rectus (SR) (P = 0.005) shortened with age. The AIDs of MR (P = 0.001) and inferior rectus (IR) (P = 0.035) elongated with axial length, whereas lateral rectus (LR) (P = 0.013) shortened. The angles of MR (P = 0.001) and LR (P = 0.000) were found to have a more downward direction toward the posterior in older subjects. Conclusion En-face images can be created by AS-OCT, and the shape of the EOMs in normal subjects using these image measurements was available. With the ability to assess the EOMs, AID and angle of muscles are expected give useful information for treating and diagnosing strabismus-related diseases

Lights-out Surgery for Strabismus Using a Heads-Up 3D Vision System

During strabismus surgery using illumination from a light source, patients complain of photophobia. The NGENUITYⓇ (Alcon) system is equipped with a high-dynamic-range (HDR) camera. A 4K display viewed by wearing circularly polarized glasses provides clear three-dimensional images of the operative field. A light source is usually required for surgeries of the anterior segment (including strabismic surgery), but the digital processing function of the NGENUITYⓇ system allows image display in relatively dark regions even without a light source. We devised a novel ‘lights-out’ surgery that does not use a microscope’s light source, and we examined the usefulness of this technique in 2 cases of strabismic surgery. We performed strabismus surgery using the NGENUITYⓇ system in two patients between January and June 2018. The HDR function was used, and the aperture was opened to the maximum while the gain was adjusted. Surgery was conducted without using the microscope’s light source. We report the 2 cases’ results and evaluate the novel method. The surgeries were performed without problem even though the microscope’s light source was not used. The patients’ photophobia was alleviated. Lights-out surgery is a potentially useful modality for strabismus surgery

Risk factors for excessive postoperative exo-drift after unilateral lateral rectus muscle recession and medial rectus muscle resection for intermittent exotropia

Background: To detect significant factors associated with excessive postoperative exo-drift in young patients with intermittent exotropia who had undergone unilateral lateral rectus muscle recession and medial rectus muscle resection. Methods: We retrospectively examined the records of 64 consecutive patients Results: Younger patients (P = 0.007), and those with larger preoperative exo-deviation at distance (P = 0.033), a lower incidence of peripheral fusion at distance (P = 0.021) or a greater postoperative initial eso-deviation (P = 0.001), were significantly more likely to have an excessive postoperative exo-drift (> 20 prism diopters). Univariate analysis revealed significant associations between excessive postoperative exo-drift and age at surgery (P = 0.004), preoperative exo-deviation at distance (P = 0.017) and postoperative initial eso-deviation at distance (P Conclusions: Postoperative exodrift in unilateral RR is predicted by the initial postoperative eso-deviation, which may offset the overcorrection. However, the exo-drift is greater in cases with a large preoperative exo-deviation and/or at a younger age, and should be followed carefully

Twist Knot: A New Sliding Noose in Adjustable Suture Strabismus Surgery

To permit noose movement without fraying the sutures following strabismus surgery, we designed a new sliding noose, the “twist knot” and investigated its advantages and disadvantages. We measured the tensile strength required to move the twist knot in a tightly tied state (134±19 gf) and in a loosened state (21±7 gf), and that required to move the conventional sliding noose in a tightly tied state (48±14 gf), and used the Kruskal-Wallis test to compare them. A significant difference was observed among the three tensile strengths (p<0.001). The twist knot technique allowed easy sliding without the multifilament braided suture becoming frayed and a knot to be firmly fixed without slipping. However, if the 2 strings of the pole sutures exit from the sclera at 2 widely separated positions, the sliding noose may become slack. Therefore, the distance between the pole sutures should be small. The simple twist knot technique was found to be an effective approach following adjustable surgery of strabismus

Formulas to Estimate Appropriate Surgical Amounts of Unilateral Recession-Resection in Intermittent Exotropia with Distance-Near Disparity

The purpose of this study was to derive new formulas to provide an optimal surgical procedure and optimal amount of recession-resection (RR) surgery in intermittent exotropia (IXT) with a disparity in angle of deviation depending on the fixation distance. The records of 117 consecutive patients with IXT who underwent RR surgery between March 2008 and December 2011 at Okayama University Hospital were retrospectively examined. Multivariable linear regression analysis was performed using the observed corrective angle of deviation at distance or near fixation as the dependent variable, and amounts of lateral rectus muscle (LR) recession (mm) and medial rectus muscle (MR) resection, and age at surgery (years) as independent variables. Two simultaneous formulas were derived: corrective angle of deviation at distance fixation (°)=1.8×recession (mm)+1.6× resection (mm)+0.15×age (years)–6.6, and corrective angle at near fixation (°)=1.5×recession (mm)+1.7× resection (mm)+0.18×age (years)–3.8. Comparisons of coefficient values of the formulas between distance and near fixation revealed that LR recession was more affected by the corrective angle in distance than near fixation. MR resection was more affected at near than distance fixation. We found that our new formulas estimated the appropriate amount of unilateral RR surgery