Search Results (16)

Previous models of extraocular mechanics have often assumed isotropic properties for ocular tissues, despite evidence indicating anisotropy in the optic nerve sheath (ONS). To investigate this further, we developed a finite element model (FEM) of horizontal eye rotation using MRI data from a living subject with normal tension glaucoma. Mechanical properties were derived from tensile tests on 17 post-mortem human eyes, revealing previously unrecognized anisotropic characteristics in the ONS. We simulated ±32° horizontal eye rotations and compared isotropic versus anisotropic ONS properties using the Holzapfel model. Strain distributions in the optic nerve (ON) were analyzed using ABAQUS 2024 software. During 32° adduction, stress and strain were concentrated at the ONS-sclera junction, reaching 8 MPa and 40% with isotropic properties, and 15 MPa and 30% with anisotropic properties. In contrast, during 32° abduction, stress was lower and strain was higher in the isotropic case (6 MPa and 30%) compared to the anisotropic case (12 MPa and 25%). Increased intraocular and intracranial pressures had minimal impact on the mechanical responses. These findings suggest that the anisotropic properties of the ONS increase stress concentration at the optic disc while reducing strain during eye movements, offering new insights into ocular biomechanics. A novel phenomenon emerged from the simulations: during larger ductions, the peripapillary Bruch’s membrane is predicted to wrinkle, forming undulations with an approximately 20 μm amplitude and 100 μm wavelength at its interface with the retina and choroid. Full article

Background/Objectives: When manipulating an object placed on the palm, the eyes and fingers move together. To perform this task precisely, coordination of the eyes and fingers is needed. Based on this view, the present study examined the three-way interaction among the central motor drives to the eyes, index finger, and little finger. Methods: Healthy male participants abducted the right index and/or little finger with or without concomitant saccadic eye movement to the right in response to a visual cue, while the forearm was in the pronated or supinated position. We measured the reaction time (RT), velocity, and amplitude of the eye movements, as well as the RT and amplitude of the electromyographic (EMG) responses in the prime movers for the independent and dependent finger movements. Results: The velocity, amplitude, and RT of the eye movement were not changed by the additional involvement of the finger movement, indicating that the central motor drive to the finger does not influence the eye motor excitability and central motor drive to the eyes. On the one hand, the RT of the finger was not changed by the eye movement, indicating that the central motor drive to the eyes does not influence the central motor drive to the finger muscle. On the other hand, the EMG amplitude in the first dorsal interosseous muscle at the movement onset decreased during the concomitant eye movement, indicating that the central motor drive to the eyes suppresses the motor excitability of the independent finger muscle. The RT increased and EMG amplitude decreased in one finger muscle when the other finger concurrently moved, indicating that the central motor drive to one finger muscle suppresses the motor excitability of and central motor drive to the other finger muscle. The change in the RT and EMG amplitude in one finger muscle caused by the concomitant execution of the other finger movement and/or eye movement varied with forearm position, indicating that forearm proprioception influences the interaction of the motor execution processes among the fingers and eyes. Conclusions: The central motor drive to the eyes or finger muscles suppresses the motor excitability of the other finger muscles and the central motor drive to that muscle, but the central motor drive to the finger muscles does not influence those for the eyes. Forearm proprioception influences the motor excitability of the finger muscle and central motor drive to that muscle. Full article

Background and Objectives: The aim of the report is to report the outcomes of the medial rectus (MR) disinsertion procedure for the management of large-angle esotropia (ET) patients. Materials and Methods: This is a retrospective case series of patients with large-angle ET who underwent an MR disinsertion procedure between March 2012 to April 2022. The procedure happened accidentally during muscle surgery. The demographic and clinical data, including sex, age, visual acuity, pre- and postoperative angle of strabismus, duction limitations, results of intraoperative forced duction tests, and follow-up duration were collected from medical records. Results: Five patients were enrolled in this study. The mean age was 62.2 ± 9.8 years, and the mean follow-up was 24.8 ± 8.7 months. The ET at the primary position of gaze was 92.0 ± 17.9 prism diopters (PD) before MR disinsertion and 38.0 ± 29.5 PD after MR disinsertion only. Abduction deficiency was −4 before after MR disinsertion, which improved to −1 at the last follow-up. Conclusions: The results of MR disinsertion were not as frustrating as anticipated. MR disinsertion may be considered in patients with large-angle sensory ET who refuse surgery on the opposite eye. Full article

The pathology of idiopathic intracranial hypertension (IIH), a disease characterized by papillary edema and increased intracranial pressure (IICP), is not yet understood; this disease significantly affects quality of life due to symptoms including vision loss, headache, and pulsatile tinnitus. By contrast, superficial siderosis (SS), a disorder in which hemosiderin is deposited on the surface of the cerebral cortex and cerebellum, potentially causes cerebellar ataxia or hearing loss. So far, no cases of IIH with infratentorial and supratentorial cortical SS have been reported. Herein, we report a case of a 31-year-old woman with obesity who developed this condition. The patient suddenly developed headache and dizziness, had difficulty walking, and subsequently became aware of diplopia. Fundus examination revealed bilateral optic nerve congestive papillae and right eye abducens disturbance. Head magnetic resonance imaging (MRI) showed prominent SS on the cerebellar surface and cerebral cortex. Lumbar puncture revealed IICP of 32 cmH₂O, consistent with the diagnostic criteria for IIH, and treatment with oral acetazolamide was started; subsequently, the intracranial pressure decreased to 20 cmH₂O. Her abduction disorder disappeared, and the swelling of the optic papilla improved. She was now able return to her life as a teacher without any sequelae. SS is caused by persistent slight hemorrhage into the subarachnoid space. In this case, both infratentorial and supratentorial cortical superficial SS was observed. Although cases of IIH complicated by SS are rare, it should be kept in mind that a causal relationship between IIH and SS was inferred from our case. Our findings also suggest that cerebrospinal fluid dynamic analysis using MRI is effective in diagnosing IIH and in determining the efficacy of treatment. Full article

Moebius syndrome is a collection of orofacial anomalies with highly variable features affecting many different systems but characterised by bilateral facial palsy and absent eye abduction. We largely regard Moebius syndrome as a diagnosis of exclusion. Lack of awareness and knowledge means that children often fall between services, leading to treatment delays and difficulty interfacing with social care and schools, with long-term impact on physical health and psychosocial development. We developed a multidisciplinary team comprising core clinicians (lead physician, geneticist, speech and language therapist, psychologist and specialist nurse) and an expanded group to encompass the other affected systems. The interactions between our specialties lead to the development of a treatment protocol, which we present. The protocol harnesses the aspects of care of children with a range of other rare diseases at a specialised paediatric centre and synthesises them into a holistic approach for MBS and related conditions. Management is sequenced on an “ABC-style” basis, with airway, feeding, vision and speech taking priority in the early years. We define management priorities as airway stabilisation with swallow assessment, ocular surface protection and maintenance of nutritional support. Management principles for issues such as speech, reflux, drooling and sleep issues are outlined. In later years, psychological support has a prominent role geared towards monitoring and interventions for low mood, self-esteem and bullying. Full article

A 77-year-old-man with arterial hypertension, diabetes mellitus type II presented at our clinic for a routine ophthalmological exam. He complained of intermittent double vision. The ophthalmic examination revealed paralysis of III (n. oculomotorius) and VI (n. abducens) cranial nerves with ptosis, deficit in elevation and abduction of the left eye. The patient underwent urgent MRI imaging of the brain/orbits and paranasal sinuses, and urgent neurological assessment. MRI revealed a volume-occupying process, starting from the posterior wall of the left maxillary sinus with perineural diffusion and involvement of the homolateral trigeminal nerve, intracranial spread in the medial cranial fossa and involvement of the cavernous, sphenoidal sinuses and the orbital apex on the left side. Biopsy was performed, and the histology resulted in sinonasal squamous cell carcinoma with intracranial spread. Full article

Adults with obesity experience high rates of disability and rapid functional decline. Identifying movement dysfunction early can direct intervention and disrupt disability development; however, subtle changes in movement are difficult to detect with the naked eye. This study evaluated how a portable, inertial measurement unit (IMU)-based motion capture system compares to a laboratory-based optokinetic motion capture (OMC) system for evaluating gait kinematics in adults with obesity. Ten adults with obesity performed overground walking while equipped with the OMC and IMU systems. Fifteen gait cycles for each participant were extracted for the 150 total cycles analyzed. Kinematics were compared between OMC and IMU across the gait cycles (coefficient of multiple correlations), at clinically significant time points (interclass correlations), and over clinically relevant ranges (Bland–Altman plots). Sagittal plane kinematics were most similar between systems, especially at the knee. Sagittal plane joint angles at clinically meaningful timepoints were poorly associated except for ankle dorsiflexion at heel strike (ρ = 0.38) and minimum angle (ρ = 0.83). All motions except for ankle dorsiflexion and hip abduction had >5° difference between systems across the range of angles measured. While IMU-based motion capture shows promise for detecting subtle gait changes in adults with obesity, more work is needed before this method can replace traditional OMC. Future work should explore standardization procedures to improve consistency of IMU motion capture performance. Full article

This study investigates the change in horizontal saccadic eye movement and smooth pursuit in patients with acquired comitant esotropia (ACE), before and after strabismus surgery. The horizontal saccades and pursuit in 11 patients with ACE were recorded using a video eye-tracker under binocular viewing before and after strabismus surgery. Participants were instructed to fixate on the new target as rapidly as possible when it randomly appeared at either 18.3° rightward or 18.3° leftward. For smooth pursuit, participants were asked to track, as accurately as possible, a step-ramp target moving at ±6.1°/s. The asymmetry of adduction-abduction and the binocular coordination in gains of saccade and pursuit were compared between the pre- and post-surgical data. The asymmetry of adduction-abduction saccade gain in each eye after surgery tended to be smaller than that before surgery. The binocular coordination of saccade showed significant improvement after surgery in only the non-dominant eye direction. Adduction-abduction asymmetry in the smooth pursuit gain in each eye after surgery tended to be smaller than before surgery. After surgery, the binocular coordination of pursuit was improved significantly in both directions. In patients with ACE, binocular coordination of saccade and smooth pursuit was poor. Binocular coordination of saccade and pursuit seems to be improved due to the improvement in ocular deviation angle and binocular visual function after surgery. Full article

Vision relies on precise eye movements controlled by six extraocular muscles (EOMs). Training kits and functional eye models are crucial for ophthalmological studies. The study investigates the potential of shape memory material (SMM) in ophthalmology, focusing on eye model mechanics and four thermally actuated smart EOMs. SMM was chosen over other actuators because of its high-power density (36 W/kg), high actuation forces (100 gf), and high displacements (200%). Finite element method (FEM) simulation on a 3D eye model was performed to analyze the thermo-mechanical properties of smart muscle, revealing the shape memory effect and super elasticity which result in the four eye movements of elevation, depression, adduction, and abduction. FEM simulation, compared to the eye model prototype, yielded a 16 mm deformation in smart muscle with a thermal actuation of 313 K (40 °C). FEM analysis, while combining smart muscle with the eye model, resulted in a 6.8517 mm deformation in the simulation. Prototype deformation was acquired as 7.262 mm. The successful actuation of the eye using thermally actuated smart muscles proves its potential for ophthalmology kits. Full article

Intraorbital and transorbital injuries are included in the group of head injuries with low frequency. In particular, such injuries rarely result in infectious processes in the brain parenchyma. This case presents a case where a 57-year-old man reported to the neurosurgery department that he had sustained an injury to the conjunctiva of the upper eyelid a month earlier. The patient was injured by a tree branch, which he removed on his own initiative. After persistent eye abduction palsy, an MRI was performed, which showed a compressive mass in the frontal lobe of the brain. A surgical procedure was indicated, which found a piece of twig 3 mm long inside the abscess. Surgical intervention and antibiotic therapy led to the complete recovery of the patient. Full article

Magnetic resonance imaging (MRI) was used to measure in vivo local strains in the optic nerve (ON) associated with horizontal duction in humans. Axial and coronal MRI were collected in target-controlled gazes in 24 eyes of 12 normal adults (six males and six females, 59 ± 16 years) during large (~28°) and moderate (~24°) ductions. The ON, globe, and extraocular muscles were manually identified, and the pixels were converted to point-sets that were registered across different imaging planes and eye positions. Shape of the ON was parameterized based on point-sets. Displacements and strains were computed by comparing deformed with initial ON configurations. Displacements were the largest in the most anterior region. However, strains from adduction were uniform along the length of the ON, while those during abduction increased with distance from the globe and were maximal near the orbital apex. For large gaze angles, ON strain during abduction was primarily due to bending near the orbital apex that is less transmitted to the eye, but during adduction the ON undergoes uniform stretching that transmits much greater loading to the posterior eye, implied by greater strain on the ON. Full article

Forward walking (FW) is a common balance assessment tool. However, its sensitivity is limited by the ceiling effect. Reverse gait, such as backward walking (BW), has been reported to have more advantages than FW for balance assessment. Three factors related to postural instability (i.e., increased speeds, restricted arm swing, and reduced visual feedback) during BW were investigated to determine BW conditions that have the potential to predict falls. Three-dimensional analyses were used to analyze seven walking conditions. FW and BW at self-selected and fast speeds were analyzed to identify the effects of speed. Walking with normal arm swings, crossed arms, and abducted arms during BW was tested to determine the effects of arm position. BW with closed and open eyes was compared to investigate the effects of visual feedback. BW had a significantly shorter step length than FW at high speeds. When the arms were abducted, the stance phase (%) was significantly lower compared to when arms were crossed during BW. Moreover, BW with closed eyes revealed significantly higher mediolateral center of mass (COM) displacements than with open eyes. We observed that BW with fast speeds, a crossed arm position, and closed eyes has the potential to help assess fall risk because it requires higher balance ability through spatiotemporal and COM adjustment. Full article

(1) Background: This study aimed to evaluate the clinical outcome of Sandwich (Amnion/Conjunctival-Limbal Autograft/Amnion) transplantation for recurrent pterygium with restrictive strabismus. (2) Methods: This retrospective study included 11 eyes in 11 patients diagnosed with recurrent pterygium with restrictive strabismus who received sandwich transplantation. The outcomes were measured by pterygium recurrence, best-corrected visual acuity, esotropia (prism diopters), and treatment complications. (3) Results: Eleven patients (six males, five females) had a mean age of 60.5 (range 36–80) years. The previously received pterygium excision surgery number was 1.8 ± 1.02 (range 1–4). The mean follow-up period was 19.9 ± 8.41 (range 12–36) months. All patients had a restriction of abduction in the previously operated eye, causing esotropia in the primary position. Pre-operative esotropia was 17.2 (range 10–30) prims diopter (PD). Five eyes (45.5%) had symblepharon before surgery. All patients were orthotropic until the last follow-up. Symblepharon was released in all eyes. Free ocular motility was present in all eyes. No donor site scar formation, scleral melt, or corneal ulcer was noted. (4) Conclusions: Sandwich transplantation for recurrent pterygium with restrictive strabismus is safe and effective. Full article

Hip-joint position sense (JPS) accuracy may be impaired in individuals with type 2 diabetes mellitus (T2DM). An impaired hip JPS can alter postural control and bodily balance. The objectives of this study are to (1) compare the hip JPS between T2DM and asymptomatic and (2) assess the relationship between hip JPS and glycosylated hemoglobin (HbAlc). This comparative cross-sectional study included 117 elderly individuals with T2DM (mean age: 59.82 ± 6.80 y) and 142 who were asymptomatic (mean age: 57.52 ± 6.90 y). The hip JPS was measured using a digital inclinometer. The individuals were repositioned to a target position with their eyes closed, and the magnitudes of matching errors were estimated as reposition errors. The hip JPS was evaluated in the flexion and abduction directions. The magnitude of reposition errors was significantly larger in the T2DM group in the right flexion (p < 0.001), the right abduction (p < 0.001), the left flexion (p < 0.001), and the left abduction (p < 0.001) directions compared to the asymptomatic group. HbA1c values showed a significant positive correlation with JPS in the right-hip flexion (r = 0.43, p < 0.001), the right-hip abduction (r = 0.36, p < 0.001), the left-hip flexion (r = 0.44, p < 0.001), and the left-hip abduction (r = 0.49, p < 0.001) directions. Hip JPS testing may be considered when assessing and formulating treatment strategies for individuals with type 2 diabetes. Future research should focus on how hip JPS can impact balance and falls in individuals with T2DM. Full article

Despite the popularity of outdoor fitness equipment (OFE) in public spaces with the aim of increasing physical activity (PA), very little research has been conducted to investigate the effectiveness of the equipment’s use, especially for achieving the target fitness goal. This study designed an OFE training protocol incorporating four modalities of PA: endurance (air walker and ski machine), resistance (rowing machine and bonny rider), flexibility (arm stretch and shoulder wheel), and balance exercise (waist twister). Seniors who completed the protocol demonstrated that for endurance training, participants were at moderate intensity from heart rate and perceived exertion, while significantly improving cardiac endurance in the two min step test. For resistance/flexibility/balance interventions, only the handgrip strength test, the 30 s chair stand test, the right-hand shoulder flexion test, the right-hand shoulder horizontal abduction test, the single-leg stance test, and the eyes open foam surface clinical test for sensory balance were significant, using a repeated measure analysis of variance. The results demonstrated that older adults aim for the OFE target for specific fitness goals can reach moderate intensity and improve their cardiorespiratory endurance. Yet, results for resistance/flexibility/balance are inconclusive. More studies are needed to carefully assess the effectiveness of using OFE. Full article