Ocular Rotation Research Articles

A protocol to quantify cross-sectional and longitudinal differences in duction patterns.

Currently, there is no established system for quantifying patterns of ocular ductions. This poses challenges in tracking the onset and evolution of ocular motility disorders, as current clinical methodologies rely on subjective observations of individual movements. We propose a protocol that integrates image processing, a statistical framework of summary indices, and criteria for evaluating both cross-sectional and longitudinal differences in ductions to address this methodological gap. We demonstrate that our protocol reliably transforms objective estimates of ocular rotations into normative patterns of total movement area and movement symmetry. This is a critical step towards clinical application in which our protocol could first diagnose and then track the progression and resolution of ocular motility disorders over time.

A trilogy of the oculomotor system: Part I: Ocular movements, finalities, and measurements.

The paper starts discussing the teleological concept that eye motions - rotations and translations - serve to vision (which supports the notion that torsions are not voluntarily driven, since they do not contribute to expand the visual exploration of space). It proposes that the primary position of the eye (not "of gaze") , the standard condition to measure them, must be defined as the coincidence of the orbital (fixed) and the ocular (movable) system of coordinates. However this becomes only a theoretic concept, since practical operations to obtain it are almost unfeasible. Besides, even a "simple" horizontal or vertical ocular rotation, though always occurring around a (presumably) fixed point (the center of ocular rotation) may be defined by different trajectories and magnitudes, depending on the two systems of measurement of eye positions and motions. Hence, in a graphical (plane) representation of such spherical coordinates, the so-called "tangent screen", an ocular "tertiary" position - a combination of a horizontal and a vertical rotations - may be described by four different points. Or, conversely, a specific eye position may be defined by four sets of angular coordinates. The mathematical representation of variation of three special coordinates in a specific rotation is best made by a matrix disposition, so that, multiplication (not commutative) of three matrices (one for each specific plane) generates six different systems (permutations) of measurements. So, though , actually, there are multiple trajectories possible between two points in space, the order in which rotations are considered influences the final result. With different systems of coordinates for each rotation and different possible orders by which they may be considered, one reaches 48 alternative systems for their measurements. Unfortunately, up to now, there I is no an established convention to express ocular rotations. So, usually, people consider that a vertical prism superimposed to a frontally placed horizontal prism, or vice-versa, correspond to equivalent processes. The paper finishes discussing inconveniences of the clinically used unity to measure eye rotations (the prism-diopter) and proposes other unities as alternative solutions.

Monopolar and bipolar electrooculography signal characteristics due to target displacements—have we seen the whole picture?

The development of electrooculography (EOG)-based human-computer interface systems is generally based on the processing of the commonly referred to horizontal and vertical bipolar EOG channels, which are computed from a horizontally-aligned and another vertically-aligned pair of electrodes, respectively. Horizontal (vertical) target displacements are assumed to result in changes in the horizontal (vertical) EOG channel only, and any cross-talk between the bipolar channels is often neglected or incorrectly attributed solely to electrode misalignment with respect to the ocular rotation axes. Objective. The aim of this work is to demonstrate that such cross-talk is intrinsic to the geometric relationship between the orientation of the verging ocular globes and the planar displacement of the gaze target with respect to the primary gaze position. Approach. Since it is difficult to record actual EOG data with electrodes which are perfectly-aligned with the ocular rotation axes, this is studied by simulating the EOG potential values for various horizontally- and vertically-displacing targets using a dipole model of the eye. Main results. We show that cross-talk between the horizontal and vertical bipolar EOG channels is manifested even if the electrodes are aligned with the ocular rotation axes. Specifically, for a horizontally- (vertically-)displaced target, while the monopolar EOG signals obtained from the horizontally- (vertically-)aligned electrodes exhibit an expected predominant potential displacement, a smaller displacement is also exhibited in the monopolar EOG signals obtained from the vertically- (horizontally-)aligned electrodes. These unexpected displacements in the vertically- (horizontally-)aligned monopolar channels may have different magnitudes, resulting in an effective potential displacement in the vertical (horizontal) bipolar EOG channel. Significance. This is significant as it shows that, unlike in many works published so far for EOG-based ocular pose estimation, it is not sufficient to only use the horizontal (vertical) bipolar EOG channel to estimate the horizontal (vertical) displacement of the ocular pose.

Optical Coherence Tomography Angiography Demonstrates Strain and Volume Effects on Optic Disk and Peripapillary Vasculature Caused by Horizontal Duction

Purpose The optic nerve mechanically loads the eye during ocular rotation, thus altering the configuration of the disk and peripapillary tissues. We used optical coherence tomography (OCT) angiography (OCTA) to investigate mechanical strains and volume changes in disk and peripapillary blood vessels during horizontal duction. Methods Structural OCT and OCTA were performed centered on optic disks; imaging was repeated in central gaze, and in 30° ab- and adduction. By an algorithm employing point-set registration of 3 D features, we developed a novel approach for measuring disk strains, and strains and volumes of the blood vessels associated with horizontal duction. Repeatability was demonstrated in each gaze position. Results 19 eyes of 10 healthy adults of average age 37 ± 15 (standard deviation, SD) years were imaged. The method was validated by demonstrating numerically consistent vascular volumes and strains for repeated imaging under identical conditions. Compared with central gaze, vascular volume increased by 5.2 ± 4.1% in adduction. Adduction and abduction caused strains of 3.0 ± 1.6% and 2.6 ± 1.8% in the optic disk, whereas blood vessels showed greater strains of 8.1 ± 1.3% and 8.2 ± 1.7%. Decomposition of strain components depending on directionality and regions demonstrated that adduction induces significant net tensile strains, suggesting traction exerted by the optic nerve. The decomposition also showed that nasotemporal compressive strains are larger in temporal hemidisks than nasal hemidisks. The Bruch’s membrane opening was significantly compressed horizontally in adduction by 1.1% (p = .009). Conclusion This novel analysis combining structural OCT and OCTA demonstrates that optic disk compression during adduction is associated with disk and vascular strains much larger than reported for intraocular pressure elevation and pulsatile perfusion, as well as compressing the disk and increasing peripapillary vascular volume. These changes may be relevant to the pathogenesis of optic nerve and retinal vascular disorders.

Simple method of measuring ocular rotation in supine position during small incision lenticule extraction.

To introduce a novel measurement method of static cyclotorsion in small incision lenticule extraction (SMILE) and to investigate the effect of preoperative parameters on cyclotorsion and the effect of cyclotorsion on postoperative outcomes. The medical records of 242 patients and 484 eyes who underwent SMILE surgery were retrospectively reviewed. Preoperative intraocular pressure, refractive error, and corneal thickness were investigated. Refractive values and visual acuity were measured at 1d, 1, 3, and 6mo. Ocular cyclotorsion in the supine position was measured by calculating the location and angle of the incision site of the cornea in the anterior slit photograph taken after surgery. Of the total 484 eyes in 242 patients, preoperative mean spherical equivalent (SE) was -4.10±1.64 D, and the mean astigmatism was -0.82±0.74 D. Uncorrected distance visual acuity (UCVA) and SE improved significantly after the surgery. Moreover, 219 (45.2%) eyes had excyclotorsion, 235 (48.6%) eyes had incyclotorsion, and 30 (6.2%) eyes had no torsion. The right eyes tended to be excyclotorted, and the left eyes tended to be incyclotorted (P<0.01). The mean cyclotorsion was 1.18°±3.69°, and the mean absolute value of cyclotorsion was 3.14°±2.26°. The range of cyclotorsion was 0.5°-11.4°. It was found that the smaller the preoperative sphere, the higher the amount of cyclotorsion (r=0.11, P=0.016). There was no significant association between the amount of cyclotorsion and preoperative astigmatism. There was no correlation between sex, preoperative corneal thickness, preoperative intraocular pressure, amount of cyclotorsion, and direction of cyclotorsion. The ratio of right eye excyclotorsion and left eye incyclotorsion on 1d was higher than that at 1, 3, and 6mo (all P<0.01). There was no difference between the 1, 3, and 6mo results in the right and left eyes (P=0.15, P=0.16, respectively). The newly devised ocular cyclotorsion measurement method can be used to evaluate ocular cyclotorsion after SMILE. Preoperative SE is associated with the amount of cyclotorsion, however, cyclotorsion doesn't have a significant effect on the results of SMILE surgery.

Biomechanical modeling of actively controlled rectus extraocular muscle pulleys

The Active Pulley Hypothesis (APH) is based on modern functional anatomical descriptions of the oculomotor plant, and postulates behaviors of the orbital pulleys proposed to be positioned by the extraocular muscles (EOMs). A computational model is needed to understand this schema quantitatively. We developed and evaluated a novel biomechanical model of active horizontal rectus pulleys. The orbital (OL) and global (GL) layers of the horizontal rectus EOMs were implemented as separate musculoskeletal strands. Pulley sleeves were modeled as tube-like structures receiving the OL insertion and suspended by elastic strands. Stiffnesses and orientations of pulley suspensions were determined empirically to limit horizontal rectus EOM side-slip while allowing anteroposterior pulley travel. Independent neural drives of the OL greater than GL were assumed. The model was iteratively refined in secondary gazes to implement realistic behavior using the simplest mechanical configuration and neural control strategy. Simulated horizontal rectus EOM paths and pulley positions during secondary gazes were consistent with published MRI measurements. Estimated EOM tensions were consistent with the range of experimentally measured tensions. This model is consistent with postulated bilaminar activity of the EOMs, and the separate roles of the GL in ocular rotation, and OL in pulley positioning.

The unique rectus extraocular muscles of cetaceans: Homologies and possible functions.

Each rectus extraocular muscle in cetaceans divides into two portions: a massive palpebral belly that inserts into the deep surface of the eyelids and a smaller scleral belly that inserts onto the eyeball. While the cetacean palpebral insertions have long been recognized, their homologies and functions remain unclear. To compare cetacean rectus EOM insertions with the global and orbital rectus EOM insertions of other mammals we dissected orbital contents of 20 odontocete species, 2 mysticete species and 18 non-cetacean species, both aquatic and terrestrial. Four cetacean species were also examined with magnetic resonance imaging (MRI). All four rectus muscles in cetaceans had well-developed palpebral bellies and insertions. Adjacent palpebral bellies showed varying degrees of fusion, from near independence to near complete fusion. Fusion was most complete towards palpebral insertions and less towards origins. A medial moiety of the superior rectus palpebral belly is likely the levator palpebrae superioris. Smaller but still robust scleral insertions were present on all recti, with the medial rectus (MR) being significantly more muscular than the others. All non-cetacean species examined had recti with distinct global and orbital insertions, the latter generally onto Tenon's capsule. Orbital insertions in pygmy hippopotamus and Florida manatee extended into the deep surfaces of the eyelids, hence qualifying as palpebral insertions. Our results suggest that rectus EOMs of mammals generally have both global and orbital insertions, and that palpebral bellies of cetaceans and other species are modified homologs of the orbital insertions. The presence of palpebral insertions in pygmy hippopotamus and absence in other cetartiodactyls suggests an intermediate condition between terrestrial cetartiodactyls and cetaceans. Palpebral insertions in Florida manatee and reports of their presence in some pinnipeds suggest parallel evolution in multiple aquatic lineages. Various functions of cetacean palpebral recti have been proposed, including eyelid dilators, protection during diving and thermogenesis for warming eye and brain. For further insight into their possible functions, we observed eye movements of captive bottlenose dolphins (Tursiops truncatus) at the U.S. National Aquarium. Our observations showed that in addition to rotation of the eyeball the entire surrounding palpebral region also moves during gaze changes. For example during upward gaze the globe not only rotates in supraduction but translates dorsally as well. It appears the rectus palpebral bellies are responsible for flexing the palpebral structures and thus also translating the globe, while the scleral insertions act directly for ocular rotation. Along with frequent non-conjugate eye movements, the oculomotor mechanics and repertoire of cetaceans are thus quite distinctive. Summarily, axial displacement within the orbit is a major 'eye movement' in cetaceans, with protrusion and retraction mediated by well-developed circular muscles and retractor bulbi respectively. Torsional eye movements driven by elaborate oblique EOMs are likewise significant. The roles of rectus EOMs for ocular rotation via their scleral insertions, especially the highly muscular MR, are for typical supra/infraductions and nasal/temporal ductions. The palpebral bellies accentuate these ductions by translating the globe and surrounding structures in the same direction.

Superior Rectus Transposition in the Management of Duane Retraction Syndrome: Current Insights.

Various surgical approaches have been described for the management of Duane retraction syndrome (DRS), a type of congenital cranial dysinnervation disorder (CCDD), the goals of which include correcting the primary position deviation and abnormal head posture (AHP), minimizing globe retraction and overshoots and improving the ocular rotations. Vertical rectus transposition (VRT) is one such technique, found more effective in improving abduction and thereby expanding the field of binocular vision, as compared to horizontal muscle surgery. VRT, however, is associated with the risk of inducing vertical deviations and also poses a risk for development of anterior segment ischemia. To overcome these concerns, transposition of only the superior rectus to the lateral rectus was proposed and evaluated to reveal improvement in alignment, AHP and motility comparable to VRT but with lesser surgical time and fewer post-operative complications. With promising results in the management of DRS, superior rectus transposition (SRT) has been extensively studied and has evolved over the last decade with several modifications to further increase the efficiency and reduce the risk of post-operative complications. This article focusses on the pre-operative considerations while planning SRT in DRS, various approaches and surgical techniques described, and the outcomes and complications of SRT in DRS. The role of SRT in the management of other CCDDs may be explored with further studies.

Superior oblique tendon thinning as a surgical treatment for Brown syndrome

To evaluate the results of a superior oblique thinning technique for the treatment of congenital Brown syndrome. The medical records of consecutive patients at a single institution who were diagnosed with congenital Brown syndrome and underwent superior oblique thinning were retrospectively reviewed. In all cases, the prism cover test was used to assess ocular alignment. Standardized nine-gaze photographs were used to evaluate ocular rotations. Ocular torsion was measured using fundus retinography. Intraoperatively, all patients showed a positive forced duction test for elevation from adduction that became negative after a strongly maintained traction test maneuver. A total of 21 eyes of 20 consecutive patients (mean age, 5.8±2.5years) were included. Preoperatively, 16 patients were orthotropic in primary position; 4, hypotropic. Postoperatively, all patients were orthotropic in primary position. Limitation of elevation in adduction improved from -3.4±-0.6 (range, -2 to -4) to 0.6±1 (range, 0 to -3; P<0.01). Fundus retinography showed >1° change in ocular torsion after surgery in 3 of 6 patients (P>0.5). Superior oblique underaction or hypertropia did not occur. No superior oblique palsy appeared in any patient. There were no changes beyond 3months postoperatively except for 1 patient who relapsed 9months after surgery and 1 patient who improved after 4years. Superior oblique thinning is effective in improving elevation in adduction and hypotropia in primary position in patients with Brown syndrome associated with a thickened superior oblique tendon.

Finite Element Model of Ocular Adduction by Active Extraocular Muscle Contraction.

PurposeIn order to clarify the role of the optic nerve (ON) as a load on ocular rotation, we developed a finite element model (FEM) of incremental adduction induced by active contractility of extraocular muscles (EOMs), with and without tethering by the ON.MethodsThree-dimensional (3-D) horizontal rectus EOM geometries were obtained from magnetic resonance imaging of five healthy adults, and measured constitutive tissue properties were used. Active and passive strain energies of EOMs were defined using ABAQUS (Dassault Systemes) software. All deformations were assumed to be caused by EOM twitch activation that rotated the eye about a fixed center. The medial rectus (MR) muscle was commanded to additionally contract starting from 26 degrees adducted position, and the lateral rectus (LR) to relax, further adducting the eye either with or without loading by the ON. Tridimensional heat maps were generated to represent the stress and strain distributions.ResultsTensions in the EOMs were physiologically plausible during incremental adduction. Force in the MR increased from 10 gm at 26 degrees adduction to approximately 28 gm at 32 degrees adduction. Under identical MR contraction, adduction with ON loading reached 32 degrees but 36 degrees without it. Maximum and minimum principal strains within the MR were 16% and 22%, respectively, but when ON loading was included, resulting stress and strain were concentrated at the optic disc.ConclusionsThis physiologically plausible method of simulating EOM activation can provide realistic input to model biomechanical behavior of active and passive tissues in the orbit to clarify biomechanical consequences of ON traction during adduction.

Assessment of objective ocular cyclodeviation under monocular condition and binocular condition using fundus photography

ObjectiveThe relationship between retinal structure and function of glaucomatous eyes has attracted a great deal of research attention. However, visual field tests are conducted under monocular condition, and ophthalmic imaging...

Myosin heavy chains in extraocular muscle fibres: Distribution, regulation and function.

This review examines kinetic properties and distribution of the 11 isoforms of myosin heavy chain (MyHC) expressed in extraocular muscle (EOM) fibre types and the regulation and function of these MyHCs. Although recruitment and discharge characteristics of ocular motoneurons during fixation and eye movements are well documented, work directly linking these properties with motor unit contractile speed and MyHC composition is lacking. Recruitment of motor units according to Henneman's size principle has some support in EOMs but needs consolidation. Both neurogenic and myogenic mechanisms regulate MyHC expression as in other muscle allotypes. Developmentally, multiply-innervated (MIFs) and singly-innervated fibres (SIFs) are derived presumably from distinct myoblast lineages, ending up expressing MyHCs in the slow and fast ends of the kinetic spectrum respectively. They modulate the synaptic inputs of their motoneurons through different retrogradely transported neurotrophins, thereby specifying their tonic and phasic impulse patterns. Immunohistochemical analyses of EOMs regenerating in situ and in limb muscle beds suggest that the very impulse patterns driving various ocular movements equip effectors with appropriate MyHC compositions and speeds to accomplish their tasks. These experiments also suggest that satellite cells of SIFs and MIFs are distinct lineages expressing different MyHCs during regeneration. MyHC compositions and functional characteristics of orbital fibres show longitudinal variations that facilitate linear ocular rotation during saccades. Palisade endings on global MIFs are postulated to respond to active and passive tensions by triggering axon reflexes that play important roles during fixation, saccades and vergence. How EOMs implement Listings law during ocular rotation is discussed.

Myectomy of the four horizontal rectus muscles with pulley fixation for the treatment of horizontal nystagmus in 10 adults: a pilot study

Myectomy and release of the four horizontal rectus muscles can ameliorate nystagmus, but may result in adduction limitation, convergence insufficiency, or exotropia. We developed a modified four-muscle myectomy with pulley fixation, in which the myectomized muscles are attached to the pulley rather than released. The purpose of this study was to present a prospective review of the clinical, nystagmographic, and quality-of-life data in a cohort of adults. Ten adults with horizontal infantile nystagmus syndrome were recruited between July 2018 and October 2018. Subjects were grouped according to presence or absence of foveal hypoplasia (FH). Following myectomy, all four horizontal rectus muscles were sutured within the pulley or encircling fascia. All participants completed a comprehensive sensorimotor examination, videonystagmography, and a nystagmus-specific quality-of-life questionnaire. Of the 10 subjects, 5 were in the FH group and 5 in the no-FH group. Postoperatively, all 10 subjects experienced an improved quality of life, with median increases of 73% (FH) and 104% (No-FH). Nystagmus amplitude and slow-phase velocity were reduced, and binocular best-corrected visual acuity improved in both groups. Foveation time increased, but inconsistently, within subjects and between groups. Horizontal ocular rotations were reduced by up to 58%. Five subjects required transposition surgery for symptomatic exotropia (4) or hypertropia (1). In this small study cohort, four-muscle myectomy with pulley fixation reduced the amplitude and velocity of nystagmus and improved quality of life and visual acuity, notwithstanding reduced ocular rotation and reoperation. Fixation of the muscle to the pulley did not reduce the risk of exotropia.

Mechanical model of extrinsic muscles of the eyeball

The mathematical modeling of the physiological behavior of extraocular muscles in ocular rotation, contributes to the learning of the oculomotor system and the development of technologies for the control of devices, through the precise prediction of the ocular displacement path. We propose in this article a mechanical model of eye movement, which incorporates the physiological properties of extraocular muscles in the force-elongation relationship and the action of agonist and antagonist muscles. An easy to understand model is presented that allows the analysis of forces applied in muscle contraction, the variation of extraocular muscle length, which generates rotation of the eye and the vector interpretation of the direction in the space towards which the eye directs the view, in movements of adduction, abduction, elevation and depression. The proposed model allows a simplification of the mathematical description, compared with other models, in relation to the action of the mechanical elements (springs and dampers) that represent the anatomical and physiological components of the contractile mechanics of the extraocular muscles. The implementation of the proposed model could serve in the future in the development of technologies that emulate horizontal or vertical eye movements for the control of devices.

Whale carcass scavenging by sharks

Sharks are well known to scavenge whale carcasses, but observations are rare. Here we (1) describe new observations of whale carcass scavenging behaviour by white (Carcharodon carcharias) and tiger (Galeocerdo cuvier) sharks, and (2) review the scientific and grey literature on the topic. Our new observations are from the east coast of New South Wales, Australia and include a sperm whale (Physeter microcephalus) carcass in 2015, a humpback whale (Megaptera novaeangliae) carcass and fin whale (Balaenoptera physalus) carcass in 2018. Analysis of these observations revealed that feeding preferences differed among whale species for each species of shark. Feeding behaviour (including test biting, head shaking, palatoquadrate protrusion, ocular rotation and nictitating membrane use) were employed by both tiger and white sharks, with little inter or intraspecific aggression. Behaviour of sharks scavenging whale carcasses differs in the primary literature depending on whale carcass and species of shark present. Most of our results support past observations regarding feeding behaviours and little inter or intraspecific aggression. However, our results differed from past events. We observed increased palatoquadrate protrusion by white sharks and avoidance of flukes or pectoral fins feeding by tiger and white sharks. Review of the literature demonstrates that scavenging events are more commonly reported in grey literature than in scientific documents.

Effect of Cyclotorsion Compensation With a Novel Technique in Small Incision Lenticule Extraction Surgery for the Correction of Myopic Astigmatism.

To comparatively investigate the clinical outcomes of small incision lenticule extraction (SMILE) surgery with or without cyclotorsion compensation for the correction of myopic astigmatism. This prospective, double-blinded, randomized controlled trial included patients who underwent SMILE surgery with bilateral myopic astigmatism. Two eyes of a single patient were randomly divided into the static cyclotorsion compensation (SCC) group and the control group. In the SCC group, the intraoperative cyclotorsion was manually compensated with a novel technique. In the control group, the cyclotorsion was not compensated. Visual acuity, manifest refraction, aberrations, objective visual quality, and contrast sensitivity were measured preoperatively and postoperatively. A total of 132 eyes from 66 patients were analyzed at the 3-month follow-up. The mean preoperative cylinder values in the SCC and control groups were -1.52 ± 0.81 and -1.57 ± 0.82 diopters (D), respectively. The mean cyclotorsion during surgery was 0.60° ± 0.63° (range: 0° to 3.2°) in the SCC group and 3.21° ± 2.33° (range: 0.1° to 10.8°) in the control group (P < .001). Both groups showed favorable results in the correction of myopic astigmatism. No statistically significant difference was found between the two groups in visual and refractive outcomes, vector parameters, entire eye aberrations, objective visual quality, or contrast sensitivity. No significant benefit was gained from cyclotorsion compensation, even in the high astigmatism subgroup. The cyclotorsion compensation technique used in this study helped minimize the alignment error but was not compulsory because the ocular rotation in SMILE surgery using a well-controlled position was too small to affect the astigmatic outcomes or postoperative visual quality. [J Refract Surg. 2019;35(5):301-308.].

Non-commutative, nonlinear, and non-analytic aspects of the ocular motor plant.

The ocular motor plant, consisting of the globe, extraocular muscles (EOMs), and connective tissue suspension, constitutes an intricate and non-linear actuator of eye movements. The pulley system of the rectus EOMs constitutes a non-linear inner gimbal actuated by the orbital layers of these EOMs that renders the sequence of ocular rotations effectively commutative to the central controller, and can be rotated by the outer gimbal driven by the oblique EOMs. Optic nerve (ON) length is insufficient to permit large angle adduction without tethering by the ON and sheath, creating at and beyond this threshold a large additional load on the medial rectus muscle. Finite element modeling suggests that adduction may eventually cause repetitive strain injury to the ON and glaucomatous optic nerve damage.

Effect of transposition of superior rectus muscle on vertical deviaton and cyclotropia

Objective To analyze the effect of transposition of superior rectus muscle on vertical deviation and cyclotropia. Methods A prospective study. All 16 patients with ocular abduction dysfunction underwent superior rectus transposited to external rectus insertion. The degree of esotropia was measured with synoptophore, and the vertical deviation was measured with Maddox rod plus prism. The subjective cyclotropia was examined with the double Maddox, and the ocular rotation was evaluated objectively with fundus photography (fovea-disc angle, FDA). Results The difference of pre- and post-operative horizontal strabismus and limit of abduction and adduction were statistically significant, from pre-operative 35.00°±2.21° to post-operative 2.19°±0.78° (t=12.776, P=0.000), from -3.62±0.22 to -2.37±0.15 (t=-7.319, P=0.000), and from -0.06±0.06 to -2.12±0.15 (t=10.688, P=0.000). The vertical deviation was improved from 0.69△+ 0.50△ to 0.63△+ 0.73△ (t=0.083, P=0.935). The subjective cyclotropia were improved from 1.25°±0.50°to -0.69°±0.46° (t=3.422, P=0.004); the objective cyclotropia were improved from 8.93°±0.81°to 6.96°±1.08° (t=2.889, P=0.018). Conclusion Transposition of superior rectus muscle is an effective and safe method to treat ocular abduction dysfunction, which can correct esotropia, improve abduction limitation and restore a certain range of binocular single vision in primary position. Key words: Transposition, superior rectus muscle; Abduction nerve disease; Vertical deviation; Cyclotropia

Longterm surgery outcome of Möbius syndrome

Objective: To investigate clinical features and the long-term surgery results of Möbius syndrome patients. Methods: This investigation presents a retrospective study of Möbius syndrome in 7 children we found since 2009. All 7 patients had MRI scan, ocular alignment in primary position, the limitation of versions and ductions and forced duction under general anesthesia. Early surgery is done to the 7 esotropia children. The pre-operative and post-operative outcomes, including the ocular alignment, deviation measurements and ocular rotations, were evaluated and compared. Results: MRI showed absence of uni- or bilateral CN6 and CN7 in all 7 patients. All 7 patients underwent extra large recession of medial rectus at the first surgery, (6.17±1.47) mm/eye. Variation of ocular deviation in the primary position within 6 months postoperatively in all patients, demonstrating that strabismus surgical stabilization needs time. Three patients with esotropia deviation≥40° preoperative were under corrected and needed the secondary operations. The average deviation in the primary position was +35.00°±16.58° before surgery and +2.14°±5.67° after surgery(t=6.040, P<0.01). The abduction in affected eye is limited both pre and postoperatively and a smaller limitation of adduction after surgery. Conclusions: Möbius syndrome has been classified to congenital cranial dysinnervation disorders (CCDDs). We recommend MR recession as the first surgical choice because of the lack of abduction ability. Longterm surgical results were considered satisfactory, improving patient self-esteem and the parent satisfaction. (Chin J Ophthalmol, 2017, 53: 897-902).

Inferior Rectus Transposition: A Novel Procedure for Abducens Palsy

Superior rectus transposition has been popularized for the treatment of abduction deficiencies. Potential complications include induced vertical deviation and torsion. A new procedure, the inferior rectus transposition (IRT), may be similarly beneficial for patients at risk for postoperative vertical deviation or incyclotropia. The purpose of this study is to describe the outcomes of patients undergoing IRT. Prospective, interventional case series. Five patients in an academic pediatric ophthalmology and strabismus practice with a complete lateral rectus palsy who underwent IRT were studied. Changes in anomalous head posture, ocular rotations, ocular alignment, and torsion preoperatively to postoperatively were compared. The patients ranged in age from 19-89 years. There was a significant correction in the angle of esotropia (ET) from 39±17Δ (14-55Δ) to 12 ± 9.8Δ (0-22Δ) postoperatively (P= .02). Two of 5 patients had preoperative hypertropia of the affected eye (1.4 ± 2.2Δ; range, 2-5Δ). One of those had no vertical deviation postoperatively and 1 patient resulted in 2Δ hypotropia. One patient without vertical misalignment preoperatively developed a small postoperative vertical deviation. Torticollis significantly improved from 31.4 ± 11.6° to 5 ± 5.8° (P= .004). All patients improved abduction, with a mean of-4.4 ± 0.5 preoperatively to-3.4 ± 0.9 postoperatively (P= .07). Initial postoperative follow-up in patients with abducens palsy undergoing IRT shows a significant improvement in ocular alignment and torticollis. In patients with preoperative hypertropia, IRT resulted in a downward shifting effect on the operated eye. IRT may be a beneficial procedure for patients with preoperative hypertropia or intorsion requiring transposition procedures. Future studies with larger populations and longer durations of follow-up will be required before this procedure can be recommended.