Persistence of eye movement following disinsertion of extraocular muscle

doi:10.1016/j.jaapos.2007.09.001

Journal of American Association for Pediatric Ophthalmology and Strabismus

Volume 12, Issue 1, February 2008, Pages 62-65

Presented at the 33rd Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Seattle, Washington, April 11-15, 2007 and at the 31st Meeting of the European Strabismological Association, Athens, Greece, May 20-23, 2007.

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Background

It is widely assumed that the insertion of the extraocular muscle is the sole site of force translation from muscle to eye. Our aim was to test this assumption by examining ocular motility after disinsertion of the extraocular muscle.

Methods

Forty-two adults (age, 20-45 years; median age, 26 years) underwent strabismus surgery. All surgeries were completed under topical anesthesia with lidocaine 2% jelly or peribulbar sensorimotor differential blocking anesthesia with ropivacaine 0.2%. Sixty-six rectus muscles and six oblique muscles were suture-locked and disinserted. After disinsertion of each muscle, the patient was asked to move the eye in the field of action of the muscle; eye movement was recorded as normal, reduced, or absent.

Results

For 50 rectus muscles (76%), eye movement was normal after disinsertion, while for 14 rectus muscles (21%), eye movement was reduced after disinsertion. For only two rectus muscles (3%), eye movement was absent after disinsertion. For all six oblique muscles (100%), eye movement was normal after disinsertion.

Conclusions

The unexpected, strong persistence of eye movement in the direction of action of the disinserted muscle indicates that anatomic insertion not only occurs at the point at which the muscle blends into the sclera but also involves the surrounding connective tissue. Orbital connective tissue can be considered an additional and important locomotor system.

Section snippets

Subjects and Methods

Informed, written consent was obtained according to a protocol compliant with the Declaration of Helsinki and approved by our local ethics committee. Forty-two strabismus surgeries were performed on 42 adult patients (25 men and 17 women; median age, 26 years; range, 20-45 years) with different types of strabismus between January 2005 and April 2006. Exclusion criteria were history of strabismus surgery in the operated eye, scleral buckle surgery, bleeding tendency, allergy to local

Results

The following ocular alignment abnormalities were observed in our sample of 42 patients: esotropia (n = 20), exotropia (n = 13), inferior oblique overaction (n = 3), dissociated vertical deviation (DVD) (n = 3), Brown syndrome (n = 2), and hypertropia (n = 1). Surgical management involved recession of 30 medial rectus, 18 lateral rectus, 2 superior rectus, and 4 inferior oblique muscles. We also resected eight medial rectus, six lateral rectus, and two inferior rectus muscles and lengthened two

Discussion

Our study shows that, after separation of any extraocular muscle from its scleral attachment, the eye still can move in the direction of action of the muscle. This indicates that, in addition to the scleral insertion of extraocular muscles, there is another functionally important insertion set that helps the muscle to exert additional active forces on the eye. Knowing the mechanism and the magnitude of such active force could be useful for diagnosis and management of different strabismus

References (14)

O.M. Hakim et al.
Strabismus surgery under augmented topical anesthesia
J AAPOS
(2005)
J.D. Porter et al.
Extraocular muscles: Basic and clinical aspects of structure and function
Surv Ophthalmol
(1995)
Y. Morad et al.
Medial transposition of the lateral rectus muscle in combined third and fourth nerve palsy
J AAPOS
(2000)
A.V. Mudgil et al.
Ophthalmologic outcome after third cranial nerve palsy or paresis in childhood
J AAPOS
(1999)
F.G. Velez et al.
Rectus muscle orbital wall fixation: A reversible profound weakening procedure
J AAPOS
(2004)
L. Koornneef
Orbital septa: Anatomy and function
Ophthalmology
(1979)
E.M. Helveston
Surgical management of strabismus: An atlas of strabismus surgery

There are more references available in the full text version of this article.

Cited by (20)

Intraoperative Findings in Consecutive Exotropia with and without Adduction Deficit
2017, Ophthalmology
Citation Excerpt :
Good (or better than expected) adduction in the presence of an abnormal or lost medial rectus muscle may be explained by other mechanical factors, such as attachments from the pulley to the globe. A study by Hakim et al20 found that for 76% of rectus muscles and 100% of oblique muscles, eye movement remained normal after the muscle had been disinserted, suggesting contracture of the orbital portion of the muscle with an effect on corresponding Tenon's fascia and pulley structures. When assigning cause of adduction deficit in consecutive exotropia, we considered other possible causative factors such as tightness of the lateral rectus muscle, demonstrable by finding restriction to adduction on intraoperative forced duction testing.
Consecutive exotropia may be associated with limited adduction, which has been reported to be caused by 1 or more anatomic abnormalities of rectus muscles or their insertions. We studied the relative frequency of grades of adduction deficit and the relative frequency of abnormal anatomic findings.
Retrospective cohort study.
Patients undergoing surgery for consecutive exotropia.
Preoperative duction deficits were graded on a −5 (severe limitation) to 0 (normal) scale. Operative reports were reviewed to classify intraoperative factors: (1) medial rectus muscle attachment type (normal, abnormal [slipped or stretched scar], attached to pulley, behind pulley, or mixed [a tenuous normal attachment, but with muscle fibers also attached to the pulley or behind the pulley]), (2) medial rectus muscle distal fiber location (millimeters from original insertion), and (3) lateral rectus muscle tightness (normal, mild restriction, moderate restriction).
Relationship of grade of adduction deficit to each intraoperative factor.
Of 143 eyes, 124 (87%) had an adduction deficit. Eyes with abnormal (n = 23), pulley (n = 9), behind pulley (n = 8), or mixed (n = 7) attachments had worse adduction deficits than normal attachments (n = 96; P < 0.02). There was a significant correlation between distal medial rectus muscle fiber location (0–19.5 mm recessed) and grade of adduction deficit (P < 0.0001). Eyes with mild or moderate lateral rectus muscle tightness on forced duction testing (n = 48/143 eyes) had worse adduction deficits than eyes without tightness (P < 0.001). Nevertheless, despite overall correlation, there was considerable individual variability. For example, for −1 and −2 adduction deficits, medial rectus muscle attachment could be at the pulley, behind the pulley, or include the pulley (19/87 eyes [22%]), and the lateral rectus muscle was tight in 36 of 87 eyes (41%).
Adduction deficits are common in patients with consecutive exotropia. Overall, more severe preoperative adduction deficits are associated with medial rectus muscle insertion abnormalities and abnormal forced ductions, but frequently there are exceptions. Severe medial rectus muscle insertion abnormalities, including lost muscles, may be found despite mild preoperative adduction deficits.
Rectus muscle flap tear as an independent cause of restricted motility
2012, Journal of AAPOS
Citation Excerpt :
We observed induced saccades within the eye's motility range as a substitute for the usual “forceps test” as indicated by the jerk component of optokinetic nystagmus. Although a recent study5 has shown that some degree of active force is retained even when a rectus muscle is disinserted, such a response is not characteristic for severe paralysis. Observing active force guided our decision not to give more time for spontaneous improvement and our conclusion that retention of the flap was not necessary.
Most published cases of rectus muscle flap tear have been associated with orbital trauma of various degrees of severity. When they accompany an orbital fracture, however, it is difficult to determine whether the flap tear is merely an incidental additional finding or a major contributing cause of the resulting restriction. How to treat the flap itself remains an open question. We report a 24-year-old man with an inferior rectus muscle flap tear caused by direct laceration of the muscle. The major finding was a “reverse leash” vertical restriction. Discarding the flap instead of reattaching it did not prevent a successful result. Our case supports the proposition that rectus muscle flap tear can be a restriction-producing entity.
Slipped, severed, torn and lost extraocular muscles
2011, Canadian Journal of Ophthalmology
Citation Excerpt :
If a muscle pulls away from a “cheese-wiring” suture during strabismus surgery, it has been recommended that the surgeon avoid any type of stimulus that may cause contraction of the muscle. The globe should not be forcefully manipulated to obtain maximum exposure because such maneuvers can possibly force the muscle posteriorly through the Tenon capsule in the event of disruption or severing of the orbital layer of the EOM to its corresponding pulley.8,9 In order to visualize the muscle while it is still anteriorly placed, the globe is displaced against the opposite orbital wall and is retroplaced, exposing the area of the Tenon capsule where the muscle is most likely to be found.
Slipped, severed, torn and lost extraocular muscles (EOM) are infrequently encountered in clinical practice but constitute significant complications of strabismus and other eye surgery and of orbital injuries. Knowledge of the clinical aspects of these various disease entities and their anatomical underpinnings are of utmost importance in providing effective recognition and treatment. These conditions share some common presenting signs, symptoms and clinical findings that are discussed in this review. The literature will be reviewed and management strategies will be presented.
On voit rarement les muscles extraoculaires (MEO) glissés, rompus, déchirés ou perdus en pratique clinique, mais ils comportent d’importantes complications touchant le strabisme et d’autres chirurgies oculaires ainsi que les blessures orbitales. La connaissance des aspects cliniques de ces diverses entités morbides et leurs étayages anatomiques ont la plus grande importance pour l’efficacité de la reconnaissance et du traitement. Ces états ont en commun certains signes de présentation, des symptômes et des résultats cliniques dont traite cet article qui présente une revue de la littérature et des stratégies de gestion.
Traumatic superior oblique tendon rupture
2009, Journal of AAPOS
"Heavy Eye" syndrome in the absence of high myopia: A connective tissue degeneration in elderly strabismic patients
2009, Journal of AAPOS
In axial high myopes with “heavy eye” syndrome, orbital MRI can be use to demonstrate degeneration of the lateral rectus–superior rectus (LR-SR) band, with the result that the lateral rectus muscle slips inferiorly and causes esotropia and hypotropia. We investigated whether this degeneration might also cause strabismus in nonmyopic elderly patients.
Three elderly patients with strabismus, 3 strabismic high myopes, and 12 orthotropic elderly subjects underwent ophthalmic examinations and orbital MRI. The lateral rectus muscle position was determined relative to globe center from quasicoronal images and correlated with LR-SR band structure. MRI scans were compared with histology of 4 cadaveric orbits ranging in age from 17 months to 93 years.
Two strabismic patients exhibited hypotropia; one exhibited esotropia. Mean axial length was 24.1 ± 0.8 mm (mean ± SD), compared with 31.6 ± 1.4 mm for myopes. The lateral rectus muscle position of elderly strabismic subjects averaged 4.6 ± 1.7 mm inferior to globe center, which was significantly lower than that of orthotropic elderly subjects (2.1 ± 1.9 mm; p = 0.01) and similar to that of high myopes (5.1 ± 3.2 mm). On MRI scanning, 100% of strabismic elderly orbits, 67% of strabismic myopic orbits, and 12.5% of control elderly orbits showed LR-SR band thinning, discontinuity, or displacement. LR-SR band degeneration was present histologically only in older cadavers.
Age-related LR-SR band degeneration permits the lateral rectus muscle to slip inferiorly in elderly nonmyopes, a mechanism of strabismus similar to myopic “heavy eye” syndrome. Imaging may assist in diagnosing this mechanical cause of age-related strabismus.
Posterior Inflection of Weakened Lateral Rectus Path: Connective Tissue Factors Reduce Response to Lateral Rectus Recession
2009, American Journal of Ophthalmology
Citation Excerpt :
Innervational tone in both the LR muscle and LR pulley tissue in the alert patient seems to be sufficient to restore LR muscle tension to near preoperative levels. In fact, a recent report suggests that orbital layer force exerted on the pulley tissues is sufficient alone to permit normal or nearly normal ductions even after disinsertion of the LR muscle from the sclera.27 There are two implicit assumptions in our analysis of these data.
To determine why lateral rectus (LR) muscle recession has a variable effect on binocular alignment using magnetic resonance imaging (MRI).
Prospective, observational, interventional case series.
Posterior LR muscle path lengths from the orbital apex to first globe contact were determined by axial plane, surface coil MRI in eight patients with unilateral LR muscle palsy and in four patients before and after bilateral LR muscle recession.
Posterior paths of paretic LR muscles were 2.2 to 6.0 mm longer (mean, 3.4 mm; P = .0002) than normal contralateral paths. Each paretic LR muscle was sharply inflected laterally at a point in the anterior orbit corresponding to the histologic location of the LR muscle pulley sleeve. Every recessed LR muscle was 0.8 to 4.4 mm (mean, 2.4 mm; P = .0008) longer after surgery than before surgery, with less temporal deflection.
The LR muscle pulley suspension contributes to LR muscle tension, tightening the muscle belly by stretching it temporally when LR muscle tone is reduced. The increase in LR muscle path length resulting from temporal inflection offsets the effect of recession by up to 4 mm. Connective tissue action explains some response variability after LR muscle recession.

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Major articlePersistence of eye movement following disinsertion of extraocular muscle

Background

Methods

Results

Conclusions

Section snippets

Subjects and Methods

Results

Discussion

J AAPOS

Surv Ophthalmol

J AAPOS

J AAPOS

J AAPOS

Ophthalmology

Surgical management of strabismus: An atlas of strabismus surgery

Major article
Persistence of eye movement following disinsertion of extraocular muscle