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Rudell JC, Stager D, Felius J, McLoon LK. Morphological Differences in the Inferior Oblique Muscles from Subjects with Over-elevation in Adduction. Invest Ophthalmol Vis Sci 2021; 61:33. [PMID: 32539136 PMCID: PMC7415317 DOI: 10.1167/iovs.61.6.33] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Purpose We examined inferior oblique muscles from subjects with over-elevation in adduction for characteristics that might shed light on the potential mechanisms for their abnormal eye position. Methods The inferior oblique muscles were obtained at the time of surgery in subjects diagnosed with either primary inferior oblique overaction or Apert syndrome. The muscles were frozen and processed for morphometric analysis of myofiber size, central nucleation, myosin heavy chain (MyHC) isoform expression, nerve density, and numbers of neuromuscular junctions per muscle section. Results The inferior oblique muscles from subjects with Apert Syndrome were smaller, and had a much more heterogeneous profile relative to myofiber cross-sectional area compared to controls. Increased central nucleation in the Apert syndrome muscles suggested on-going myofiber regeneration or reinnervation over time. Complex changes were seen in the MyHC isoform patterns that would predict slower and more sustained contractions than in the control muscles. Nerve fiber densities were significantly increased compared to controls for the muscles with primary inferior oblique overaction and Apert syndrome that had no prior surgery. The muscles from Apert syndrome subjects as well as those with primary inferior oblique overaction with no prior surgery had significantly elevated numbers of neuromuscular junctions relative to the whole muscle area. Conclusions The muscles from both sets of subjects were significantly different from control muscles in a number of properties examined. These data support the view that despite similar manifestations of eye misalignment, the potential mechanism behind the strabismus in these subjects is significantly different.
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Al-Falki Y, Al-Shraim M, Alsabaani NA, Eid RA, Radad K. Ultrastructural changes of extraocular muscles in strabismus patients. Ultrastruct Pathol 2019; 43:145-153. [PMID: 31570030 DOI: 10.1080/01913123.2019.1671927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Strabismus is an ocular disorder characterized by partial or complete inability to keep eye alignment. It represents a very common ocular problem at ophthalmology clinics worldwide. The current study aimed to show the most encountered ultrastructural changes in extraocular muscles (EOMs) collected from patients with different forms of strabismus. Nine specimens of EOMs were collected from five patients during strabismus correction surgery and processed for light and electron microscopy examinations. Histologically, skeletal muscle fibers in normal EOMs appeared tight and normally arranged with clear striations. In strabismic muscles, the fibers appeared disarranged, and atrophied, swollen and disintegrated in some situations. By transmission electron microscopy, normal EOMs were formed of skeletal muscle fibers with intact basal membrane and sarcolemma, tightly aligned myofibrils with well-arranged sarcomeres, Z line and H zone, and normally distributed mitochondria. On the other hand, strabismic EOMs revealed vacuolation and degeneration of myofibrils, accumulation of lipid droplets, subsarcolemmal inclusions and clustering of mitochondria. EOMs obtained from a Down syndrome patient with V-pattern infantile esotropia showed extensive vacuolation and disintegration of myofibrils, and extra- and intracellular deposition of collagen fibers. Interestingly, some skeletal muscle cells exhibited features of autophagic cell death with a trial of engulfing process by neighboring cells. In conclusion, our study traces some characteristic ultrastructural changes in strabismic EOMs, most notably, extensive vacuolation, clustering of mitochondria, degeneration of myofibrils and autophagic changes. These changes might be emphasized as possibly secondary to strabismus.
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Affiliation(s)
- Yahya Al-Falki
- Department of Surgery, Ophthalmology Division, College of medicine, King Khalid University, Abha, Saudi Arabia
| | - Mubarak Al-Shraim
- Department of Pathology, College of Medicine, King Khalid University, Abha, Saudi Arabia
| | - Nasser A Alsabaani
- Department of Surgery, Ophthalmology Division, College of medicine, King Khalid University, Abha, Saudi Arabia
| | - Refaat A Eid
- Electron Microscopy Unit, Department of Pathology, College of Medicine, King Khalid University, Abha, Saudi Arabia
| | - Khaled Radad
- Department of Pathology, College of Medicine, King Khalid University, Abha, Saudi Arabia
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Europa TA, Nel M, Heckmann JM. A review of the histopathological findings in myasthenia gravis: Clues to the pathogenesis of treatment-resistance in extraocular muscles. Neuromuscul Disord 2019; 29:381-387. [PMID: 31029532 DOI: 10.1016/j.nmd.2019.03.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/18/2019] [Accepted: 03/20/2019] [Indexed: 12/28/2022]
Abstract
In myasthenia gravis autoantibodies target components of the neuromuscular junction causing variable degrees of weakness. In most cases, autoantibodies trigger complement-mediated endplate damage and extraocular muscles may be most susceptible. A proportion of MG cases develop treatment-resistant ophthalmoplegia. We reviewed publications spanning 65 years reporting the histopathological findings in the muscles and extraocular muscles of myasthenic patients to determine whether pathological changes in extraocular muscles differ from non-ocular muscles. As extraocular muscles represent a unique muscle allotype we also compared their histopathology in myasthenia to those in strabismus. We found that in myasthenia gravis, the non-ocular muscles frequently demonstrate neurogenic changes regardless of myasthenic serotype. Mitochondrial stress/damage was also frequent in myasthenic muscles and possibly more evident in muscle-specific kinase antibody-positive MG. Although myasthenia-associated paralysed extraocular muscles demonstrated prominent fibro-fatty replacement and mitochondrial alterations, these features appeared commonly in paralysed extraocular muscles of any cause. We postulate that extraocular muscles may be more susceptible than limb muscles to poor contractility as a consequence of myasthenia, resulting in a cascade of atrophy signaling pathways and altered mitochondrial homeostasis which contribute to the tipping point in developing treatment-resistant myasthenic ophthalmoplegia. Early strategies to improve force generation in extraocular muscles are critical.
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Affiliation(s)
- Tarin A Europa
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Melissa Nel
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Jeannine M Heckmann
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa; Neurology Division, Department of Medicine, University of Cape Town, Cape Town, South Africa.
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Agarwal AB, Feng CY, Altick AL, Quilici DR, Wen D, Johnson LA, von Bartheld CS. Altered Protein Composition and Gene Expression in Strabismic Human Extraocular Muscles and Tendons. Invest Ophthalmol Vis Sci 2017; 57:5576-5585. [PMID: 27768799 PMCID: PMC5080916 DOI: 10.1167/iovs.16-20294] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Purpose To determine whether structural protein composition and expression of key regulatory genes are altered in strabismic human extraocular muscles. Methods Samples from strabismic horizontal extraocular muscles were obtained during strabismus surgery and compared with normal muscles from organ donors. We used proteomics, standard and customized PCR arrays, and microarrays to identify changes in major structural proteins and changes in gene expression. We focused on muscle and connective tissue and its control by enzymes, growth factors, and cytokines. Results Strabismic muscles showed downregulation of myosins, tropomyosins, troponins, and titin. Expression of collagens and regulators of collagen synthesis and degradation, the collagenase matrix metalloproteinase (MMP)2 and its inhibitors, tissue inhibitor of metalloproteinase (TIMP)1 and TIMP2, was upregulated, along with tumor necrosis factor (TNF), TNF receptors, and connective tissue growth factor (CTGF), as well as proteoglycans. Growth factors controlling extracellular matrix (ECM) were also upregulated. Among 410 signaling genes examined by PCR arrays, molecules with downregulation in the strabismic phenotype included GDNF, NRG1, and PAX7; CTGF, CXCR4, NPY1R, TNF, NTRK1, and NTRK2 were upregulated. Signaling molecules known to control extraocular muscle plasticity were predominantly expressed in the tendon rather than the muscle component. The two horizontal muscles, medial and lateral rectus, displayed similar changes in protein and gene expression, and no obvious effect of age. Conclusions Quantification of proteins and gene expression showed significant differences in the composition of extraocular muscles of strabismic patients with respect to important motor proteins, elements of the ECM, and connective tissue. Therefore, our study supports the emerging view that the molecular composition of strabismic muscles is substantially altered.
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Affiliation(s)
- Andrea B Agarwal
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
| | - Cheng-Yuan Feng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
| | - Amy L Altick
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
| | - David R Quilici
- Mick Hitchcock Nevada Proteomics Center, University of Nevada, Reno, Nevada, United States
| | - Dan Wen
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, China
| | - L Alan Johnson
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States 4Sierra Eye Associates, Reno, Nevada, United States
| | - Christopher S von Bartheld
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
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Schiavi C. Extraocular Muscles Tension, Tonus, and Proprioception in Infantile Strabismus: Role of the Oculomotor System in the Pathogenesis of Infantile Strabismus-Review of the Literature. SCIENTIFICA 2016; 2016:5790981. [PMID: 27006860 PMCID: PMC4781980 DOI: 10.1155/2016/5790981] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 01/27/2016] [Indexed: 05/04/2023]
Abstract
The role played by the extraocular muscles (EOMs) in the etiology of concomitant infantile strabismus is still debated and it has not yet definitively established if the sensory anomalies in concomitant strabismus are a consequence or a primary cause of the deviation. The commonest theory supposes that most strabismus results from abnormal innervation of the EOMs, but the cause of this dysfunction and its origin, whether central or peripheral, are still unknown. The interaction between sensory factors and innervational factors, that is, esotonus, accommodation, convergence, divergence, and vestibular reflexes in visually immature infants with family predisposition, is suspected to create conditions that prevent binocular alignment from stabilizing and strengthening. Some role in the onset of fixation instability and infantile strabismus could be played by the feedback control of eye movements and by dysfunction of eye muscle proprioception during the critical period of development of the visual sensory system. A possible role in the onset, maintenance, or worsening of the deviation of abnormalities of muscle force which have their clinical equivalent in eye muscle overaction and underaction has been investigated under either isometric or isotonic conditions, and in essence no significant anomalies of muscle force have been found in concomitant strabismus.
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Affiliation(s)
- Costantino Schiavi
- Department of Experimental, Diagnostic, and Specialty Medicine (DIMES), University of Bologna, St. Orsola-Malpighi Teaching Hospital, Via P. Palagi 9, 40138 Bologna, Italy
- *Costantino Schiavi:
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Yao J, Wang X, Ren H, Liu G, Lu P. Ultrastructure of medial rectus muscles in patients with intermittent exotropia. Eye (Lond) 2015; 30:146-51. [PMID: 26514242 DOI: 10.1038/eye.2015.213] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 09/11/2015] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To study the ultrastructure of the medial rectus in patients with intermittent exotropia at different ages.PATIENTS AND METHODS The medial recti were harvested surgically from 20 patients with intermittent exotropia. Patients were divided into adolescent (age<18 years, n=10) and adult groups (age >18 years, n=10). The normal control group included five patients without strabismus and undergoing eye enucleation. Hematoxylin and eosin staining and transmission electron microscopy were used to visualize the medial recti. Western blot was used to determine the levels of myosin and actin.RESULTS Varying fiber thickness, atrophy, and misalignment of the medial recti were visualized under optical microscope in patients with exotropia. Electron microscopy revealed sarcomere destruction, myofilament disintegration, unclear dark and light bands, collagen proliferation, and fibrosis. The adolescent group manifested significantly higher levels of myosin and actin than the adult group (P<0.05).CONCLUSION Younger patients with intermittent exotropia show stronger contraction of the medial recti compared with older patients. Our findings suggest that childhood was the appropriate time for surgery as the benefit of the intervention was better than in adulthood.
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Affiliation(s)
- J Yao
- Department of Ophthalmology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - X Wang
- Medical College of Soochow University, Suzhou, Jiangsu Province, China
| | - H Ren
- Department of Ophthalmology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - G Liu
- Department of Ophthalmology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - P Lu
- Department of Ophthalmology, The First Affiliated Hospital of Soochow University, Suzhou, China
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Hamdi MM, El-Hawary GR, El-Hefnawy NG, Salman MI. Histopathological and electron microscopic study for different grades of inferior oblique muscle overaction. Clin Ophthalmol 2013; 7:917-21. [PMID: 23723682 PMCID: PMC3665640 DOI: 10.2147/opth.s43705] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose To correlate between the clinical degree of inferior oblique muscle (IO) overaction and the histopathological changes of the muscle. Settings Departments of Ophthalmology and Pathology, Faculty of Medicine, Ain Shams University, Cairo, Egypt. Patients and methods Biopsies from 12 IO muscles were taken during strabismus surgery for cases of IO muscle overaction. One biopsy from a normal IO was taken as a control. All samples were examined under light microscopy and transmission electron microscopy. Results In light microscopy, all cases showed histopathological changes, in the form of degenerated and regenerating muscle fibers, increased fibrofatty infiltration, and mild variability of muscle fiber size. Hypertrophied nerve bundles also appeared in biopsies from patients with grade II and grade III IO overaction. Endomysial and perimysial fibrosis, mononuclear inflammatory infiltrates, and focal fatty infiltration were seen in biopsies from cases of grade III IO overaction. In electron microscopy, ultrastructural examination revealed an increased number of mitochondria associated with some degree of mitochondrial pleomorphism. Hypercontracted fibers, vacuoles, and fat droplets were also noticed. Conclusion IO overaction is always accompanied by histopathological changes that differ in severity according to the clinical grading of the overaction. Changes in nerve fibers can also occur in severe cases.
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Affiliation(s)
- Momen M Hamdi
- Ophthalmology Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt
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Altick AL, Feng CY, Schlauch K, Johnson LA, von Bartheld CS. Differences in gene expression between strabismic and normal human extraocular muscles. Invest Ophthalmol Vis Sci 2012; 53:5168-77. [PMID: 22786898 DOI: 10.1167/iovs.12-9785] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Strabismic extraocular muscles (EOMs) differ from normal EOMs in structural and functional properties, but the gene expression profile of these two types of EOM has not been examined. Differences in gene expression may inform about causes and effects of the strabismic condition in humans. METHODS EOM samples were obtained during corrective surgery from patients with horizontal strabismus and from deceased organ donors with normal EOMs. Microarrays and quantitative PCR identified significantly up- and down-regulated genes in EOM samples. Analysis was performed on probe sets with more than 3-fold differential expression between normal and strabismic samples, with an adjusted P value of ≤ 0.05. RESULTS Microarray analysis showed that 604 genes in these samples had significantly different expression. Expression predominantly was upregulated in genes involved in extracellular matrix structure, and down-regulated in genes related to contractility. Expression of genes associated with signaling, calcium handling, mitochondria function and biogenesis, and energy homeostasis also was significantly different between normal and strabismic EOM. Skeletal muscle PCR array identified 22 (25%) of 87 muscle-specific genes that were significantly down-regulated in strabismic EOMs; none was significantly upregulated. CONCLUSIONS Differences in gene expression between strabismic and normal human EOMs point to a relevant contribution of the peripheral oculomotor system to the strabismic condition. Decreases in expression of contractility genes and increases of extracellular matrix-associated genes indicate imbalances in EOM structure. We conclude that gene regulation of proteins fundamental to contractile mechanics and extracellular matrix structure is involved in pathogenesis and/or consequences of strabismus, suggesting potential novel therapeutic targets.
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Affiliation(s)
- Amy L Altick
- Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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Berg KT, Hunter DG, Bothun ED, Antunes-Foschini R, McLoon LK. Extraocular muscles in patients with infantile nystagmus: adaptations at the effector level. ARCHIVES OF OPHTHALMOLOGY (CHICAGO, ILL. : 1960) 2012; 130:343-9. [PMID: 22411664 PMCID: PMC3759680 DOI: 10.1001/archophthalmol.2011.381] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To test the hypothesis that the extraocular muscles (EOMs) of patients with infantile nystagmus have muscular and innervational adaptations that may have a role in the involuntary oscillations of the eyes. METHODS Specimens of EOMs from 10 patients with infantile nystagmus and postmortem specimens from 10 control subjects were prepared for histologic examination. The following variables were quantified: mean myofiber cross-sectional area, myofiber central nucleation, myelinated nerve density, nerve fiber density, and neuromuscular junction density. RESULTS In contrast to control EOMs, infantile nystagmus EOMs had significantly more centrally nucleated myofibers, consistent with cycles of degeneration and regeneration. The EOMs of patients with nystagmus also had a greater degree of heterogeneity in myofiber size than did those of controls, with no difference in mean myofiber cross-sectional area. Mean myelinated nerve density, nerve fiber density, and neuromuscular junction density were also significantly decreased in infantile nystagmus EOMs. CONCLUSIONS The EOMs of patients with infantile nystagmus displayed a distinct hypoinnervated phenotype. This represents the first quantification of changes in central nucleation and myofiber size heterogeneity, as well as decreased myelinated nerve, nerve fiber, and neuromuscular junction density. These results suggest that deficits in motor innervation are a potential basis for the primary loss of motor control. CLINICAL RELEVANCE Improved understanding of the etiology of nystagmus may direct future diagnostic and treatment strategies.
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Affiliation(s)
- Kathleen T Berg
- Department of Ophthalmology, University of Minnesota, Minneapolis, MN 55455, USA
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Porter JD, Baker RS. Developmental adaptations in the extraocular muscles ofMacaca nemestrinamay reflect a predisposition to strabismus. Strabismus 2009; 1:173-80. [DOI: 10.3109/09273979309052368] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Park SE, Sa HS, Oh SY. Innervated myotendinous cylinders alterations in human extraocular muscles in patients with strabismus. KOREAN JOURNAL OF OPHTHALMOLOGY 2009; 23:93-9. [PMID: 19568357 PMCID: PMC2694299 DOI: 10.3341/kjo.2009.23.2.93] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Accepted: 03/12/2009] [Indexed: 11/23/2022] Open
Abstract
Purpose To analyze innervated myotendinous cylinders (IMCs) in the extraocular muscles (EOMs) of normal subjects and strabismic patients. Methods The rectus muscles of 37 subjects were analyzed. Distal myotendinous specimens were obtained from 3 normal subjects, 20 patients with acquired strabismus, 11 with infantile strabismus, and from 3 with congenital nystagmus, and were studied by using light microscopy. Some specimens (6 rectus muscles) were also examined by transmission electron microscopy. Results IMCs were found in the distal myotendinous regions of EOMs. The IMCs of patients with acquired strabismus showed no significant morphological alterations. However, significant IMCs alterations were observed at the distal myotendinous junction of patients with congenital strabismus and congenital nystagmus. Conclusions This study supports the notion that IMCs in human EOMs function mainly as proprioceptors, along with effector properties, and a disturbance of ocular proprioceptors plays an important role in the pathogenesis of oculomotor disorder. We suggest that a proprioceptive feedback system should be stimulated and calibrated early in life for the development of binocular vision.
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Affiliation(s)
- Sung-Eun Park
- Department of Ophthalmology, Eulji University School of Medicine, Eulji General Hospital, Seoul, Korea
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Abstract
Extraocular muscle is fundamentally distinct from other skeletal muscles. Here, we review the biological organization of the extraocular muscles with the intent of understanding this novel muscle group in the context of oculomotor system function. The specific objectives of this review are threefold. The first objective is to understand the anatomic arrangement of the extraocular muscles and their compartmental or layered organization in the context of a new concept of orbital mechanics, the active pulley hypothesis. The second objective is to present an integrated view of the morphologic, cellular, and molecular differences between extraocular and the more traditional skeletal muscles. The third objective is to relate recent data from functional and molecular biology studies to the established extraocular muscle fiber types. Developmental mechanisms that may be responsible for the divergence of the eye muscles from a skeletal muscle prototype also are considered. Taken together, a multidisciplinary understanding of extraocular muscle biology in health and disease provides insights into oculomotor system function and malfunction. Moreover, because the eye muscles are selectively involved or spared in a variety of neuromuscular diseases, knowledge of their biology may improve current pathogenic models of and treatments for devastating systemic diseases.
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Affiliation(s)
- Robert F Spencer
- Department of Anatomy, Medical College of Virginia, Richmond, VA 23298, USA
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Porter JD, Baker RS, Ragusa RJ, Brueckner JK. Extraocular muscles: basic and clinical aspects of structure and function. Surv Ophthalmol 1995; 39:451-84. [PMID: 7660301 DOI: 10.1016/s0039-6257(05)80055-4] [Citation(s) in RCA: 173] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Although extraocular muscle is perhaps the least understood component of the oculomotor system, these muscles represent the most common site of surgical intervention in the treatment of strabismus and other ocular motility disorders. This review synthesizes information derived from both basic and clinical studies in order to develop a better understanding of how these muscles may respond to surgical or pharmacological interventions and in disease states. In addition, a detailed knowledge of the structural and functional properties of extraocular muscle, that would allow some degree of prediction of the adaptive responses of these muscles, is vital as a basis to guide the development of new treatments for eye movement disorders.
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Affiliation(s)
- J D Porter
- Department of Ophthalmology, University of Kentucky Medical Center, Lexington, USA
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Carry MR, Ringel SP, Starcevich JM. Mitochondrial morphometrics of histochemically identified human extraocular muscle fibers. Anat Rec (Hoboken) 1986; 214:8-16. [PMID: 2937349 DOI: 10.1002/ar.1092140103] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Three fiber types--coarse, granular, and fine--were readily identified in histochemical cryostat sections of human extraocular muscle (EOM). The cryostat retrieval method was utilized to identify these three fiber types in serial electron microscopic thin sections. Using morphometric techniques, five mitochondrial variables (mitochondrial volume fraction, mitochondrial profile size, mitochondrial profile density, and clusters of two or of three or more mitochondrial profiles) were determined for a total of 162 histochemically identified fibers from two regions (orbital and global zones) from six EOMs. Coarse fibers had numerous large-sized mitochondrial profiles, often occurring in clusters. Granular fibers had fewer and smaller-sized profiles scattered across the fiber. Fine fibers had the most numerous, but smallest-sized mitochondrial profiles. Despite significant differences in group (fiber types) means for the mitochondrial variables, no single variable was sufficient for separating fiber types into distinct populations. Although a scattergram plot of two variables was sufficient to separate orbital zone fibers, a computer-generated, multivariate discriminant analysis was needed to separate the global zone fibers into distinct populations. These results will aid future studies on normal and pathological human EOM by providing a morphometric basis for identifying fiber types in the orbital and global zones.
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Meyer E, Ludatscher RM, Zonis S. Primary and secondary overacting inferior oblique muscles: an ultrastructural study. Br J Ophthalmol 1984; 68:416-20. [PMID: 6722074 PMCID: PMC1040366 DOI: 10.1136/bjo.68.6.416] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Biopsy material from primary and secondary overacting inferior oblique muscles were examined by light and electron microscopy. Most muscle fibres were in different stages of atrophy. A high variation of alterations was encountered in all muscles. The most striking abnormalities were huge accumulations of mitochondria and muscle vacuolisation related mainly to the enlargement of the tubules of sarcoplasmic reticulum. The mitochondrial aggregates and vacuolisation occupied more muscle surface in the inferior muscles of primary overaction than those of secondary overaction.
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