[A voxel-based magnetic resonance study of cortical gray matter structures in intermittent exotropia].

Objective: To explore the changes in gray matter volume of the cerebral cortex in patients with intermittent exotropia (IXT) using the voxel-based analysis and to analyze the correlation between these changes and clinical manifestations. Methods: This was a cross-sectional study. A collection of 15 consecutive patients diagnosed with IXT at Tianjin Eye Hospital from March 2021 to May 2022 formed the exotropia group, which comprised 8 males and 7 females, with an average age of (23.5±5.2) years. Ten healthy individuals, 3 males and 7 females, with an average age of (27.0±7.5) years, were selected as the control group. All participants underwent assessments of exotropia severity and Titmus stereoacuity. Three-dimensional high-resolution brain images were obtained through MRI scans. Voxel-based morphometry was employed to preprocess the MRI data, and the SPM toolbox in MATLAB was utilized to analyze differences of images between the two groups. Regions of interest (ROI) with structural abnormalities in the gray matter volume analysis were selected, and the ratio of gray matter voxel values in the ROI to the mean gray matter voxel values of the whole brain for each participant was calculated using the MarsBaR software. The correlation between this ratio and exotropia severity as well as the common logarithm of Titmus stereoacuity was analyzed. Results: The differences in age, gender distribution, and refractive error between the two groups were not statistically significant (all P>0.05). However, there were statistically significant differences in the degree of strabismus and Titmus stereoacuity (both P<0.001). Compared to the control group, patients in the strabismus group exhibited decreased gray matter volume in several brain regions, including the wedges of the medial surface of the cerebral hemisphere (decreased by 89 voxels), the left lingual gyrus (decreased by 176 voxels), the left calcarine sulcus V3 area (decreased by 30 voxels), the central anterior gyrus of the right frontal lobe (decreased by 192 voxels), the gray matter of the left hippocampal gyrus (decreased by 20 voxels), and the bilateral lateral geniculate nuclei (decreased by 100 and 40 voxels on the left and right sides, respectively). These differences were all statistically significant (all P<0.001). Additionally, there was an increase in gray matter volume in several brain regions, including the bilateral caudate nuclei (increased by 60 and 76 voxels on the left and right sides, respectively) and the left precentral gyrus (increased by 36 voxels). These differences were also statistically significant (all P<0.001). A group-level analysis identified 10 brain regions with structural differences between the two groups, which were used as ROI. The gray matter volume ratio was negatively correlated with the degree of exotropia (all P<0.05) in the ROI of the left wedges (r=-0.670), left calcarine sulcus V3 area (r=-0.610), and left lingual gyrus (r=-0.684). The gray matter volume ratio was negatively correlated with lgTS (all P<0.05) in the ROI of the left wedges (r=-0.568) and the central anterior gyrus of the right frontal lobe (r=-0.563). Conclusions: Patients with IXT exhibit decreased gray matter volume in the horizontal connection areas between the primary visual cortices V1 and V2. The reduction in gray matter volume of the lingual gyrus and the dorsal visual pathway V3 area becomes more pronounced with increasing exotropia severity, while the gray matter volume of the precentral gyrus (BA6 area) decreases with worsening stereoacuity.

Functional changes in fusional vergence-related brain areas and correlation with clinical features in intermittent exotropia using functional magnetic resonance imaging.

To explore the functional changes of the frontal eye field (FEF) and relevant brain regions and its role in the pathogenesis of intermittent exotropia (IXT) children via functional magnetic resonance imaging (fMRI). Twenty-four IXT children (mean age, 11.83 ± 1.93 years) and 28 normal control (NC) subjects (mean age, 11.11 ± 1.50 years) were recruited. During fMRI scans, the IXT children and NCs were provided with static visual stimuli (to evoke sensory fusion) and dynamic visual stimuli (to evoke motor fusion and vergence eye movements) with binocular disparity. Brain activation in the relevant brain regions and clinical characteristics were evaluated. Group differences of brain activation and brain-behavior correlations were investigated. For dynamic and static visual disparity relative to no visual disparity, reduced brain activation in the right FEF and right inferior occipital gyrus (IOG), and increased brain activation in the left middle temporal gyrus complex (MT+) were found in the IXT children compared with NCs. Significant positive correlations between the fusional vergence amplitude and the brain activation values were found in the right FEF, right IPL, and left cerebellum in the NC group. Positive correlations between brain activation values and Newcastle Control Scores (NCS) were found in the left MT+ in the IXT group. For dynamic visual disparity relative to static visual disparity, reduced brain activation in the right middle occipital gyrus, left cerebellum, and bilateral IPL was found in the IXT children compared with NCs. Significant positive correlations between brain activation values and the fusional vergence amplitude were found in the right FEF and right cerebellum in the NC group. Negative correlations between brain activation values and NCS were found in the right middle occipital gyrus, right cerebellum, left IPL, and right FEF in the IXT group. These results suggest that the reduced brain activation in the right FEF, left IPL, and cerebellum may play an important role in the pathogenesis of IXT by influencing fusional vergence function. While the increased brain activation in the left MT+ may compensate for this dysfunction in IXT children.

Structural and Functional Changes of Brain in Children With Intermittent Exotropia: A Study Combining Multiple MRI Modalities.

BACKGROUND: To investigate structural and functional changes of brain in children with intermittent exotropia (IXT) and their relationship with clinical features. METHODS: Twenty-one IXT patients (mean age 9.38 ± 2.62 years) and 21 age-, gender-, education-, and handedness-matched healthy controls (HCs, mean age 9.52 ± 3.28 years) underwent high-resolution T1 imaging, diffusion tensor imaging (DTI), and resting-state functional MRI (rs-fMRI). The gray and white matter volume analyzed by voxel-based morphometry (VBM) based on T1 imaging, the fractional anisotropy (FA) and mean diffusivity (MD) indices based on DTI, and the amplitude of low frequency fluctuation (ALFF) value based on rs-fMRI were compared between these 2 groups. The correlations between MRI-derived parameters in significant brain regions and various clinical characteristics of IXT were analyzed. RESULTS: Compared with HCs, IXT children showed significantly decreased FA in right precentral gyrus (PRG) and right postcentral gyrus (POG), and significantly decreased ALFF in bilateral calcarine sulcus, bilateral cuneus, left lingual gyrus, and left superior occipital gyrus. The FA value in right PRG and right POG was negatively correlated with disease duration (r = -0.520, P = 0.016), angle of exodeviation at near (r = -0.549, P = 0.010), and angle of exodeviation at distance (r = -0.547, P = 0.010). CONCLUSIONS: IXT children exhibited abnormalities of white matter microstructure and reduced spontaneous neural activities in brain regions involving in oculomotor performance and binocular fusion. Further studies are needed to determine whether these findings are related to the neuropathologic mechanism or downstream changes of IXT.

More than static: altered dynamic functional connectivity of primary visual cortex in the comitant exotropia patients.

Previous neuroimaging studies have demonstrated that comitant exotropia (CE) patients exhibit dysfunction in various visual cortical areas. However, whether the CE patients showed abnormal dynamic functional connectivity (dFC) in primary visual cortex (V1) changes remains unknown. A total of 36 CE patients (25 males and 11 females) and 36 well-matched healthy control subjects (HCs) were enrolled in the study. The dFC with sliding window method was applied to investigate the dynamic functional connectivity changes in primary visual cortex (V1). Compared with HCs, CE patients had decreased dFC values between left V1 and right fusiform (Fus), right lingual (LING), left orbital medial frontal gyrus, left Fus, left calcarine and left precuneus (PreCUN). Meanwhile, CE patients had decreased dFC values between right V1 and left cerebelum_6 (CER_6), right lingual and left inferior occipital gyrus. Our study demonstrates that CE patients showed altered dFC within visual network and V1-default mode network, which might indicate the decreased variability FC values in the primary visual cortex in CE patients.

Altered voxel-wise degree centrality associated with patients with comitant exotropia.

Objective of the study is to investigate the altered intrinsic functional hubs in patients with comitant exotropia (CE) using the voxel-wise degree centrality (DC) analysis method. A total of 28 CE patients and 28 healthy controls (HCs) similarly matched in sex, age, and education level were recruited in this study. All subjects underwent a resting-state functional MRI scan, the voxel-wise DC method was applied to evaluate brain network hubs alterations in CE patients. Then, the DC maps between two groups were chosen to be classification features to distinguish patients with CE from HCs based on the support vector machine (SVM) model. The algorithm performance was evaluated by a permutation test. Compared with HCs, CE patients exhibited significant enhanced DC value in the left cerebelum 8 and the right cerebelum 3; and remarkably decreased DC value in the right precentral gyrus, right anterior cingulated, and paracingulate gyri (two-tailed, voxel level: P < 0.01; GRF correction, cluster level: P < 0.05). However, no relationship was found between the observed average DC of the different brain regions and the clinical features ( P > 0.05). In addition, the SVM model showed an accuracy of 83.93% to clarify CE patients from HCs using the DC maps as a classification feature. CE patients displayed altered functional network hubs in multiple brain areas associated with cognition and motor control, and the DC variability could classify patients from HCs with high accuracy. These findings may assist to understand the neuropathological mechanism for the disease.

The predictive value of local to remote functional connectivity changes in comitant exotropia patients.

BACKGROUND: Comitant exotropia (CE) is a common eye disease with abnormal eye movement, whereas altered synchronous neural activity in CE patients is poorly understood. The purpose of our study was to investigate local to remote functional connectivity of blood oxygen level-dependent (BOLD) signals changes in CE patients. MATERIAL AND METHODS: Thirty-four patients and thirty-four healthy controls (HCs) underwent resting-state MRI scans. The ReHo and FC method was applied to investigate the local to remote functional connectivity changes in CE patients. RESULTS: Compared to the HC group, CE patients showed significant increased ReHo values in the left cerebellar_crus2 and left middle frontal gyrus. Meanwhile, CE patients showed significant decreased ReHo values in the right middle temporal gyrus, left postcentral gyrus and right angular. Moreover, CE patients showed an increased FC between the cerebellar network, sensorimotor network (SMN) and default-mode network (DMN). The support vector machine (SVM) classification was up to a total accuracy of 94.12%. The AUC of the classification model was 0.99 on the basis of ReHo map. CONCLUSION: Our result highlights that CE patients had abnormal local to remote functional connectivity in the cerebellar network, SMN, DMN, which might indicate the neural mechanism of eye movements and stereo vision dysfunction in CE patients. Moreover, the SVM algorithm reveals ReHo maps as a potential biomarker for predicting clinical outcomes in CE patients.

Abnormal biorbital angle in children with infantile exotropia.

PURPOSE: The causative factors of infantile exotropia are unknown. The purpose of this study was to investigate the relationships between the biorbital angle and the pathogenesis of infantile exotropia. STUDY DESIGN: Retrospective. METHODS: Of all patients diagnosed as infantile exotropia with onset prior to 12 months of age between 2010 and 2017, 31 patients without any neurological disorders or developmental delay were identified. The angle between both lateral walls of the orbit, defined as the biorbital angle, was measured in the horizontal plane at the optic nerve and where the horizontal extraocular muscles appeared on axial magnetic resonance imaging (MRI) or computed tomography (CT) of the orbit. These patients' data were compared with those of 129 ophthalmologically normal children. All subjects of this study were Japanese. RESULTS: The mean biorbital angle was significantly larger in patients with infantile exotropia than in the normal children (106.6 ± 5.7° vs 94.2 ± 5.1°, p < 0.001). Of the patients with infantile exotropia, 21 (68%) had an angle outside the 95% confidence interval calculated in normal children. All cases were divided into a constant (15 cases) and intermittent (16 cases) group; there was no significant difference between them in the mean biorbital angles (107.9 ± 5.6° vs 105.4 ± 5.8°, p = 0.224). No correlations were identified between the biorbital angle and the angle of exodeviation, either distant or near. CONCLUSIONS: Children with infantile exotropia have a larger biorbital angle. This anatomical abnormality may be an associate factor of infantile exotropia.

Evaluation of the insertion distance of the medial rectus in consecutive exotropia by means of intraoperative measure and optical coherence tomography.

PURPOSE: To assess the agreement between the measurements of the distance from the medial rectus muscles insertion to the limbus measured by intra-operative spectral-domain optical coherence tomography (SD-OCT) in consecutive exotropia (cXT). METHODS: An analysis was performed on total of 14 medial rectus (MR) muscles of 14 patients who underwent surgery for the treatment of cXT. The limbus-insertion distance of the MR muscles was measured using preoperative SD-OCT and intraoperatively using a calliper. The intraclass correlation coefficient (ICC) and Bland Altman plots were calculated to determine the agreement between the two methods, as well as the correlation. RESULTS: Mean age was 36.3 ± 16.0 years (range 13-60), with 60% being women. Mean preoperative deviation was 38.7 ± 16.9 prismatic dioptres (PD) (range 16-65), being +1.3 ± 6.3 PD (range -12 to +10 PD) after surgery. Intraoperatively the MR insertion was found at 8.7 ± 2.1 mm (range 5.5-12.0) and by OCT at 7.7 ± 1.2 mm (range 5.3-10.0). The ICC showed a moderate to good agreement (0.659; 95% confidence interval: 0.157-0.885; p < 0.001), with a correlation of R = 0.792 (p = 0.011). A better agreement was observed in those MR that were less retro-inserted. CONCLUSIONS: SD-OCT is able to measure the insertion to the limbus distance of the medial rectus muscles that have been previously operated on, showing moderate to good agreement with intraoperative measurements. However, the agreement was poor in muscles with a large retro-insertion.

Quantitative Analysis of Eyeball Rotation During Lateral Gaze in Intermittent Exotropia: A Magnetic Resonance Imaging Study.

Purpose: To evaluate the eyeball rotation during lateral gaze in patients with intermittent exotropia (IXT) using three-dimensional magnetic resonance imaging (MRI). Methods: In this prospective observational study, patients with IXT (n = 29) underwent orbital MRI during central, right, and left gazes. Fixation targets were placed at a 40° angle for lateral gaze. After acquisition of MR images, the position of the static tissues other than the eyeball in the MR images were matched three-dimensionally. The optical axis was defined as the perpendicular line to its lens passing through the corneal vertex. The rotation angle was measured as the angle between optical axes in central gaze and lateral gaze using ImageJ. A difference of 3° or more in the rotational angle between both eyes was considered a significant difference. Results: Eight patients (26.7%) had a larger adduction angle than the abduction angle of the fellow eye and six patients (20.0%) showed a smaller adduction angle during lateral gaze on at least one side. There was no significant factor associated with the pattern of rotation. Conclusions: Almost one-half of the patients with IXT had significant difference in the rotation angle between both eyes during lateral gaze. Measurement of the rotation angle during lateral gaze using MRI showed that IXT is not a perfectly comitant disturbance of gaze in some subjects. Translational Relevance: Quantitative analysis for eye movements using MRI can provide useful information for physiologic mechanism and proper surgical planning in patients with IXT.

Prevalence of strabismus and its risk factors among school aged children: The Hong Kong Children Eye Study.

The study aims to determine the prevalence of strabismus and its risk factors among school children in Hong Kong. This is a cross-sectional study involving 6-8 year old children from different districts in Hong Kong. 4273 children received comprehensive ophthalmological examination, cycloplegic auto-refraction, best corrected visual acuity (BCVA), anterior segment examination, cover/uncover test, ocular motility, and fundus examination. Demographic information, pre- and post- natal background, parental smoking status, and family history of strabismus were obtained through questionnaires. Strabismus was found among 133 children (3.11%, 95% CI 2.59-3.63%), including 117 (2.74%) exotropia and 12 (0.28%) esotropia cases (exotropia-esotropia ratio: 9.75:1). There was no significant difference in prevalence across age (6-8 years) and gender. Multivariate analysis revealed associations of strabismus with myopia (≤ - 1.00D; OR 1.61; 95% CI 1.03-2.52; P = 0.037) hyperopia (≥ + 2.00D; OR 2.49; 95% CI 1.42-4.39; P = 0.002), astigmatism (≥ + 2.00D; OR 2.32; 95% CI 1.36-3.94; P = 0.002), and anisometropia (≥ 2.00D; OR 3.21; 95% CI 1.36-7.55; P = 0.008). Other risk factors for strabismus included maternal smoking during pregnancy (OR 4.21; 95% CI 1.80-9.81; P = 0.001), family history of strabismus (OR 6.36; 95% CI 2.78-14.50, P < 0.0001) and advanced maternal age at childbirth (> 35 years; OR 1.65; CI 1.09-2.49, P = 0.018). The prevalence of strabismus among children aged 6-8 years in Hong Kong is 3.11%. Refractive errors, family history of strabismus and maternal smoking history during pregnancy are risk factors. Early correction of refractive errors and avoidance of maternal smoking during pregnancy are potentially helpful in preventing strabismus.

Macular perfusion density evaluation in constant and intermittent exotropia by means of optical coherence tomography angiography.

BACKGROUND: To quantify and compare retinal microvascular features using optical coherence tomography angiography (OCTA) in constant (XT) and intermittent exotropia (IXT). METHODS: An observational cross-sectional study was conducted from September 2020 to November 2020 at the Affiliated Eye Hospital of Wenzhou Medical University. OCTA examination was performed to evaluate the macular perfusion density of the deep capillary plexus (DCP), superficial capillary plexus (SCP), and foveal avascular zone (FAZ) parameters in XT and IXT patients, and in age-matched controls. The study parameters were analyzed. RESULTS: A total of 76 participants, including 16 (21%) XT patients, 24 (32%) IXT patients, and 36 (47%) controls, were recruited. The exodeviation angle was 39.06 ± 10.38 prism degrees (PD) at near and 43.00 ± 9.74 PD at distance in the XT group, and 27.13 ± 18.28 PD at near and 31.04 ± 18.82 PD at distance in the IXT group. The macular perfusion density of the DCP in 6 × 6-mm scans and the SCP in 3 × 3-mm scans were lower in the deviating eyes than in the fixating eyes of XT patients (p < 0.001, p = 0.032, respectively). The macular perfusion density of the DCP in the deviating eyes of XT and IXT patients was significantly lower than that of the controls. There was no significant difference in the FAZ parameters among the groups. CONCLUSIONS: In XT patients, OCTA revealed lower macular perfusion density in deviating eyes than in fixating eyes and control eyes. IXT patients showed no difference between the two eyes, but the macular perfusion density of the DCP was lower than that of the controls.

[MRI study of rectus extraocular muscles in concomitant exotropia with small angle vertical deviation].

Objective: To observe the changes of four pulley locations of extraocular rectus muscles and rectus muscle volumes, as well as superior and inferior part ratio of horizontal rectus muscles, in concomitant exotropia with small-angle vertical deviation in primary gaze. Methods: Cross-sectional study. Data was collected from January 2018 to December 2019 in Tianjin Eye Hospital. The pulley position changes and volumes of four extraocular rectus muscles in the coronal position of patients who had concomitant exotropia without vertical deviation (group A) or with small-angle vertical deviation in primary gaze (<5 prism diopter; group B) and normal controls (group C) were observed using MRI, and the changes of the volume ratio of the superior and inferior parts of the horizontal rectus muscle were calculated. One way analysis of variance and Kruskal-Wallis test were used for statistical analysis. Results: There were 19 patients (38 eyes; 10 males, 9 females) aged (30±7) years in group A, ten patients (20 eyes; 4 males, 6 females) aged (27±6) years in group B, and 20 healthy volunteers (40 eyes) in group C. Age and gender distribution were matched among the three groups (all P>0.05). Among the three groups, the pulley locations of the four extraocular rectus muscles were not significantly different (all P>0.05). The medial rectus muscle volume in groups A [(358.6±44.9) mm3; t=6.405, P<0.01] and B [(334.7±35.6) mm3; t=6.025, P<0.01] was significantly smaller than group C [(437.5±49.3) mm3]. There was no statistically significant difference in the superior and inferior muscle volume ratio of the lateral rectus in three groups (all P>0.05), while the ratio in group B was more dispersive. Conclusions: The pulley location changes of four extraocular rectus muscles of patients with concomitant exotropia and small-angle vertical deviation in primary gaze are not significant, but the medial rectus volume in patients who had concomitant exotropia with vertical deviation or not is significantly smaller. The dispersive superior and inferior muscle volume ratio of the horizontal rectus muscles may be related to the small angle of vertical deviation in clinical examinations. (Chin J Ophthalmol, 2021, 57: 223-227).

Improved SSD network for accurate detection of optic disc and fovea and application in excyclotropia screening.

The detection of the optic disc (OD) and fovea is essential to many automatic diagnosis systems for retinal diseases. The single shot multibox detector (SSD) can generate predictions from feature maps of various resolutions, which has not been introduced into the OD and fovea detection. To enhance the detection performance, we propose an improved SSD network, which has strengthened information flow enabled by the dense connections. The proposed method can achieve multiscale detection of the OD and fovea with strengthened feature propagation. Extensive experiments on the publicly available Messidor database and local fundus images are performed to evaluate the performance of the proposed method. Compared with seven types of representative solutions in the Messidor database, the proposed method can achieve competitive performance compared to state-of-the-art algorithms. Furthermore, the proposed method is applied to the excyclotropia screening. The screening results demonstrate promising application prospects for the proposed method in medical practice.

Minimal invasive vertical muscle transposition for the treatment of large angle exotropia due to congenital medial rectus hypoplasia: Case Report and Literature Review.

Reports of isolated anomalies of the medial rectus (MR) muscle in literature are sparse. It has been identified as a subtype of congenital cranial dysinnervation disorder that affects the normal development of brainstem motor neurons. Herein, we report a 37-year-old male presented with large-angle exotropia since the birth of right eye with palpebral fissure widening. On examination of ocular movements, there was -6 limitation of adduction. There was no limitation in other ocular movements. In the preoperative CT scan, all extraocular muscles were present. He underwent surgery in right eye. Intraoperatively in the site of medial rectus, we found an empty sheath without muscle fibers indicating medial rectus hypoplasia. The width of muscle insertion was normal. Surgery consisted of lateral rectus muscle recession 10 mm in hang-back method and vertical muscle transposition procedure, by a modification of Nishida technique, in which the vector of superior and inferior recti was transposed medially by inserting non-absorbable sutures at nasal margins of muscles secured to sclera 8 mm posterior to medial rectus site without tenotomy or splitting. The deviation was decreased to less than 10 PD exotropia in primary position. The adduction was improved from -6 to -4. The palpebral fissure asymmetry was also corrected. Here, we also reviewed clinical features of all cases of medial rectus hypoplasia/aplasia in the literature and discussed surgical approaches. For vertical rectus transposition and horizontal muscle weakening, this technique has the advantages of being simpler and less traumatic to ocular tissues and unlike the traditional transposition procedures, there is no need for tenotomy and splitting.

Analysis of new attachment site in medial rectus resection with advancement using anterior segment optical coherence tomography.

OBJECTIVE: To evaluate the surgical outcome of unilateral medial rectus resection with small advancement for recurrent exotropia, ≤30 prism diopters (PD), and verify new attachment site anatomically using anterior segment optical coherence tomography (ASOCT). METHOD: This study is a retrospective chart review of patients who underwent 1.0 mm advancement of unilateral resected medial rectus from original medial rectus (OMR) insertion for recurrent exotropia since 2014. The age at operation, sex, preoperative angle of deviation, near stereopsis, and suppression were evaluated. Success was defined as ≤5 PD of esodeviation or ≤10 PD of exodeviation at the final visit. Preoperative scleral thickness was measured using ASOCT, 1.0 and 0.5 mm anterior to OMR insertion, and at the insertion. RESULTS: A total of 76 patients, including 30 males (40.2%), were reviewed retrospectively. Continuous values were presented as mean ± standard deviation. Age at operation was 11.6 ± 6.6 years. The preoperative deviation was 20.9 ± 3.6 PD, and the amount of resected unilateral medial rectus was 4.5 ± 0.6 mm. The minimum required follow-up period after operation was 12 months after surgery. The postoperative follow-up period was 21.3 ± 8.0 months. A total of 65 patients (87.8%) showed successful outcome at the final visit. Preoperative scleral thickness at 1.0 and 0.5 mm anterior to OMR insertion site, and at OMR insertion site were 0.52 ± 0.05, 0.52 ± 0.06, and 0.43 ± 0.04 mm, respectively. Scleral thickness at OMR insertion site was significantly less compared with 1.0 and 0.5 mm from the OMR insertion site (p = 0.03). CONCLUSION: The scleral thickness 1.0-0.5 mm anterior to OMR insertion site was thicker that than at the OMR insertion site. The new technique of medial rectus resection with small advancement may be safer and more effective than conventional technique.

Inestabilidad de la polea como causa de estrabismo / Pulley instability as a cause of strabismus

RESUMEN La caracterización de las poleas de los músculos extraoculares ha sido de gran trascendencia en la fisiopatología del equilibrio óculo-motor. El efecto mecánico de la polea funcional es cambiar el eje de acción del músculo de acuerdo con la orientación que el globo ocular presente. Los trastornos en la localización o estabilidad de las poleas pueden crear patrones de estrabismo incomitante. Es importante el conocimiento de estas anomalías porque los procedimientos quirúrgicos estándar no corrigen los desplazamientos de las poleas. Se realizó una búsqueda del tema de los últimos 10 años utilizando la plataforma de infomed(AU)

ABSTRACT Characterization of extraocular muscle pulleys has had great relevance in the physiopathology of ocular motor balance. The mechanical effect of the functional pulley is to change the axis of action of the muscle in keeping with the orientation of the eyeball. Pulley location or stability disorders may create incomitant strabismus patterns. It is important to be aware of these anomalies because standard surgical procedures do not correct pulley displacement. A search was conducted on the Infomed platform of papers published about the topic in the past ten years(AU)

Functional anatomy of extraocular muscles during human vergence compensation of horizontal heterophoria.

We employed magnetic resonance imaging to quantify human extraocular muscle (EOM) contractility during intermittent convergent and divergent strabismus with each eye viewing monocularly at 20 cm compared with centered target fusion. Contractility, indicated by posterior partial volume change, was analyzed in transverse rectus and in medial and lateral superior oblique (SO) muscle compartments. In five subjects with intermittent esotropia, abduction of the deviated eye to monocular target fixation was associated with significant whole lateral rectus (LR) contraction, but with medial rectus (MR) relaxation that was significantly greater in the superior than inferior compartment. Esotropic eye abduction to binocular fusion was associated with similar relaxation in the two MR compartments, but with greater contraction in the LR's superior than inferior compartment. The whole diverging eye SO muscle relaxed. In three subjects with intermittent exotropia, converging eye fusional adduction was associated with significant whole LR relaxation and with MR contraction attributable to significantly greater contraction in the superior than inferior compartment. In adduction of the exotropic eye to monocular target fixation but not fusional adduction, the whole SO exhibited significant relaxation. Rectus pulley positions were not significantly altered by fusion of either form of intermittent strabismus. Globe rotational axis was eccentric in intermittent strabismus, rolling the eye so that rectus EOM lever arms facilitated vergence. These results confirm, and extend to fusion of intermittent horizontal strabismus, differential compartmental function in horizontal rectus EOMs and suggest a novel role for the SO in compensation of both intermittent esotropia and exotropia. NEW & NOTEWORTHY Disjunctive eye movements normally permit binocular fixation in near visual space but also compensate for mechanical imbalances in binocular alignment developing over the life span. Magnetic resonance imaging of the extraocular muscles demonstrates important differential function in muscle compartments during compensation of large-angle intermittent convergent and divergent strabismus in humans. Eye translation during rotation also enhances vergence compensation of intermittent strabismus.

Hemangioma cavernoso orbitario múltiple de 18 años de evolución / Multiple orbital cavernous haemangioma of 18 years evolution

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Altered Functional Connectivity of the Primary Visual Cortex in Adult Comitant Strabismus: A Resting-State Functional MRI Study.

PURPOSE: The aim of this study was to examine the functional connectivity between the primary visual cortex and other cortical areas during rest in normal subjects and patients with comitant strabismus using functional magnetic resonance imaging (fMRI). METHODS: A prospective, observational study was conducted. Ten patients with comitant exotropia and eleven matched healthy subjects underwent resting-state fMRI with their eyes closed. Resting-state fMRI was performed using a 3.0 T MR scanner. The primary visual cortex was subdivided into anterior and posterior subdivisions. The resting-state functional connectivities within the primary visual cortex and between the primary visual cortex and other cortical areas were calculated for each group and compared between the strabismic and normal control groups. fMRI data were analyzed using Statistical Parametric Mapping software and Analysis of Functional NeuroImages software. RESULTS: Compared with the normal controls, patients with comitant strabismus had increased functional connectivity between the posterior primary visual cortex and other cortical areas, especially the visual cortex [Brodmann area 19 (BA19)] and other oculomotor regions, such as the frontal eye field (BA6). CONCLUSIONS: The fMRI results suggest that ongoing and permanent cortical changes occur in patients with comitant strabismus. Disrupted brain functional connectivities are associated with abnormal eye movement and loss of stereopsis. Our study provides a neurological basis for understanding the pathophysiology of comitant strabismus, which may prompt new areas of research to more precisely define this basis and extend these findings to enhance diagnosis and treatment.