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The Role of Extraocular Muscle Pulleys in Incomitant Non-Paralytic Strabismus.

Clark RA - Middle East Afr J Ophthalmol (2015 Jul-Sep)

Bottom Line: Acquired disorders of pulley location can be divided into four broad categories: Connective tissue disorders (e.g., Marfan syndrome), globe size disorders (e.g., high myopia), senile degeneration (e.g., sagging eye syndrome), and trauma (e.g., orbital fracture or postsurgical).Preoperative diagnosis is aided by: (1) Clinical history of predisposing risk factors, (2) observation of malpositioning of the medial canthus, lateral canthus, and globe, and (3) gaze-controlled orbital imaging using direct coronal slices.Finally, surgical correction frequently involves novel techniques that reposition and stabilize the pulley and posterior muscle belly within the orbit using permanent scleral sutures or silicone bands without changing the location of the muscle's insertion.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, University of California, Los Angeles, California, USA.

ABSTRACT
The rectus extraocular muscles (EOMs) and inferior oblique muscle have paths through the orbit constrained by connective tissue pulleys. These pulleys shift position during contraction and relaxation of the EOMs, dynamically changing the biomechanics of force transfer from the tendon onto the globe. The paths of the EOMs are tightly conserved in normal patients and disorders in the location and/or stability of the pulleys can create patterns of incomitant strabismus that may mimic oblique muscle dysfunction and cranial nerve paresis. Developmental disorders of pulley location can occur in conjunction with large, obvious abnormalities of orbital anatomy (e.g., craniosynostosis syndromes) or subtle, isolated abnormalities in the location of one or more pulleys. Acquired disorders of pulley location can be divided into four broad categories: Connective tissue disorders (e.g., Marfan syndrome), globe size disorders (e.g., high myopia), senile degeneration (e.g., sagging eye syndrome), and trauma (e.g., orbital fracture or postsurgical). Recognition of these disorders is important because abnormalities in pulley location and movement are often resistant to standard surgical approaches that involve strengthening or weakening the oblique muscles or changing the positions of the EOM insertions. Preoperative diagnosis is aided by: (1) Clinical history of predisposing risk factors, (2) observation of malpositioning of the medial canthus, lateral canthus, and globe, and (3) gaze-controlled orbital imaging using direct coronal slices. Finally, surgical correction frequently involves novel techniques that reposition and stabilize the pulley and posterior muscle belly within the orbit using permanent scleral sutures or silicone bands without changing the location of the muscle's insertion.

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Related in: MedlinePlus

Intraoperative photo of the lateral rectus equatorial myopexy procedure shows a single 6–0 polyester monofilament suture is placed through the equatorial sclera and adjacent superior lateral rectus muscle belly (white arrow) to lock the posterior muscle belly into its correct temporal location, centered on the black dot marking the center of the retractor
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Figure 5: Intraoperative photo of the lateral rectus equatorial myopexy procedure shows a single 6–0 polyester monofilament suture is placed through the equatorial sclera and adjacent superior lateral rectus muscle belly (white arrow) to lock the posterior muscle belly into its correct temporal location, centered on the black dot marking the center of the retractor

Mentions: If only the LR pulley is involved, a more elegant approach uses permanent sutures to restore the normal LR pulley position. This technique, labeled equatorial myopexy,333435 begins with isolation of the LR insertion through a standard conjunctival incision, either fornix or limbal. With the insertion secured on a muscle hook, the anomalous inferotemporal posterior muscle path toward the equator of the globe can be clearly identified [Figure 4]. Any planned recession or resection of the insertion is performed first, followed by the equatorial myopexy procedure. Because the LR pulley is relatively deformable, the posterior LR belly can be repositioned by rotating the muscle hook until the midpoint of the muscle belly at the equator lies along an imaginary line connecting the medial and lateral canthi. The LR is locked into this position using a single permanent suture at the equator through the sclera and adjacent ¼ muscle belly [Figure 5] and then the conjunctiva is closed in the standard fashion. The procedure can be repeated bilaterally if both LR are involved.


The Role of Extraocular Muscle Pulleys in Incomitant Non-Paralytic Strabismus.

Clark RA - Middle East Afr J Ophthalmol (2015 Jul-Sep)

Intraoperative photo of the lateral rectus equatorial myopexy procedure shows a single 6–0 polyester monofilament suture is placed through the equatorial sclera and adjacent superior lateral rectus muscle belly (white arrow) to lock the posterior muscle belly into its correct temporal location, centered on the black dot marking the center of the retractor
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4502169&req=5

Figure 5: Intraoperative photo of the lateral rectus equatorial myopexy procedure shows a single 6–0 polyester monofilament suture is placed through the equatorial sclera and adjacent superior lateral rectus muscle belly (white arrow) to lock the posterior muscle belly into its correct temporal location, centered on the black dot marking the center of the retractor
Mentions: If only the LR pulley is involved, a more elegant approach uses permanent sutures to restore the normal LR pulley position. This technique, labeled equatorial myopexy,333435 begins with isolation of the LR insertion through a standard conjunctival incision, either fornix or limbal. With the insertion secured on a muscle hook, the anomalous inferotemporal posterior muscle path toward the equator of the globe can be clearly identified [Figure 4]. Any planned recession or resection of the insertion is performed first, followed by the equatorial myopexy procedure. Because the LR pulley is relatively deformable, the posterior LR belly can be repositioned by rotating the muscle hook until the midpoint of the muscle belly at the equator lies along an imaginary line connecting the medial and lateral canthi. The LR is locked into this position using a single permanent suture at the equator through the sclera and adjacent ¼ muscle belly [Figure 5] and then the conjunctiva is closed in the standard fashion. The procedure can be repeated bilaterally if both LR are involved.

Bottom Line: Acquired disorders of pulley location can be divided into four broad categories: Connective tissue disorders (e.g., Marfan syndrome), globe size disorders (e.g., high myopia), senile degeneration (e.g., sagging eye syndrome), and trauma (e.g., orbital fracture or postsurgical).Preoperative diagnosis is aided by: (1) Clinical history of predisposing risk factors, (2) observation of malpositioning of the medial canthus, lateral canthus, and globe, and (3) gaze-controlled orbital imaging using direct coronal slices.Finally, surgical correction frequently involves novel techniques that reposition and stabilize the pulley and posterior muscle belly within the orbit using permanent scleral sutures or silicone bands without changing the location of the muscle's insertion.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, University of California, Los Angeles, California, USA.

ABSTRACT
The rectus extraocular muscles (EOMs) and inferior oblique muscle have paths through the orbit constrained by connective tissue pulleys. These pulleys shift position during contraction and relaxation of the EOMs, dynamically changing the biomechanics of force transfer from the tendon onto the globe. The paths of the EOMs are tightly conserved in normal patients and disorders in the location and/or stability of the pulleys can create patterns of incomitant strabismus that may mimic oblique muscle dysfunction and cranial nerve paresis. Developmental disorders of pulley location can occur in conjunction with large, obvious abnormalities of orbital anatomy (e.g., craniosynostosis syndromes) or subtle, isolated abnormalities in the location of one or more pulleys. Acquired disorders of pulley location can be divided into four broad categories: Connective tissue disorders (e.g., Marfan syndrome), globe size disorders (e.g., high myopia), senile degeneration (e.g., sagging eye syndrome), and trauma (e.g., orbital fracture or postsurgical). Recognition of these disorders is important because abnormalities in pulley location and movement are often resistant to standard surgical approaches that involve strengthening or weakening the oblique muscles or changing the positions of the EOM insertions. Preoperative diagnosis is aided by: (1) Clinical history of predisposing risk factors, (2) observation of malpositioning of the medial canthus, lateral canthus, and globe, and (3) gaze-controlled orbital imaging using direct coronal slices. Finally, surgical correction frequently involves novel techniques that reposition and stabilize the pulley and posterior muscle belly within the orbit using permanent scleral sutures or silicone bands without changing the location of the muscle's insertion.

Show MeSH
Related in: MedlinePlus