Surgical Management of Strabismus Following Vitreo-Retinal Surgery

Article (PDF Available)inAmerican Orthoptic Journal 62(1):44-49 · July 2012with66 Reads
DOI: 10.3368/aoj.62.1.44
Abstract
orders, have been well described. 1– 5 Most commonly, these motility disorders follow scleral buckle repair for retinal detach-ment; however, strabismus has also been described following vitrectomy, pneumatic retinopexy, and cryotherapy alone. 6– 8 While the mechanisms by which stra-bismus develops have not been rigorously studied, it is clear that multiple etiologic factors are often present in the same indi-vidual. In scleral buckling surgery, which will be the focus of this discussion, the pro-posed mechanisms that create strabismus include: sensory disturbance, muscle re-strictions, redirection of muscle forces, direct muscle injury, malpositioning or
American Orthoptic Journal 1
© 2012 Board of Regents of the University of Wisconsin System, American Orthoptic Journal, Volume 62, 2012, ISSN 0065- 955X, E-ISSN 1553- 4448
orders, have been well described.
1– 5
Most
commonly, these motility disorders follow
scleral buckle repair for retinal detach-
ment; however, strabismus has also been
described following vitrectomy, pneumatic
retinopexy, and cryotherapy alone.
6– 8
While the mechanisms by which stra-
bismus develops have not been rigorously
studied, it is clear that multiple etiologic
factors are often present in the same indi-
vidual. In scleral buckling surgery, which
will be the focus of this discussion, the pro-
posed mechanisms that create strabismus
include: sensory disturbance, muscle re-
strictions, redirection of muscle forces,
direct muscle injury, malpositioning or
INTRODUCTION
Persistent motility disorders, strabismus
persisting longer than 3 months, following
surgical correction of vitreo- retinal dis-
ABSTRACT
Motility disorders and strabismus after vitreo- retinal sur-
gical intervention have multiple etiologic factors. The main
focus here is strabismus following scleral buckling surgery.
The preoperative evaluation of these patients must be in-
clusive for restrictions, redirected muscle forces, adherence
syndromes, muscle weakness, and visual sensory distur-
bance. Restoration of binocular function is generally the
goal of surgical intervention, but paramount to surgery is
assessing the potential for binocular function. Surgical tech-
niques for overcoming the barriers to fusion are discussed
with clinical vignettes to illustrate the principal. Surgery,
which is appropriately planned, based on these principals
can be highly successful in restoring visual functioning.
Surgical Management of
Strabismus Following Vitreo-
Retinal Surgery
Michael C. Struck, M.D.
From the Department of Ophthalmology and Visual Sci-
ences, University of Wisconsin, Madison, Wisconsin.
Requests for reprints should be addressed to: Michael C.
Struck, M.D., University of Wisconsin, Department of Oph-
thalmology and Visual Sciences, 2870 University Ave., Suite
206, Madison, WI 53705; e-mail: mcstruck@wisc .edu
Presented as part of a Symposium of the Joint Meeting of the
American Orthoptic Council, the American Association of
Certifi ed Orthoptists, and the American Academy of Oph-
thalmology, Orlando, Florida, October 23, 2011.
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SYMPOSIUM: 20/20 X 2
2 Volume 62, 2012
limitation as far as possible. The exam-
iner then attempts to advance the rotation
of the eye further with an instrument and
feels for restriction to movement. Active
generation is the next test. This involves
having the patient rotate the eye into the
eld of the restriction. The examiner then
“holds” the eye with an instrument and
instructs the patient to rotate the eye op-
posite (out of the fi eld of restriction), this
time feeling for the ability to generate a
force. Dynamic MRI could also be helpful
if the surgeon suspects a slipped or disin-
serted muscle.
CASE ONE
A 50-year- old woman presented with a history
of retinal detachment and scleral buckle re-
pair. Preoperatively, she complained of inter-
mittent diplopia, worsening with fatigue. She
was noted to have excellent visual acuity 20/ 25
in the affected eye and 20/ 20 in the fellow eye.
Prism cover testing revealed an intermittent
exotropia of 12
Δ
at distance and 18
Δ
at near,
with an 8
Δ
intermittent right hypertropia.
Surgery involved scleral buckle removal with
a right superior rectus recession and right me-
dial rectus resection with adjustable sutures.
Postoperatively, she was noted to have a 4– 6
Δ
esotropia at distance and orthotropic at near,
but “unable to fuse.” Subsequently, she was
measured with 5° of excyclotorsion. A right
Harada- Ito surgery was performed and fusion
was reestablished.
This case represents three important prin-
ciples of surgical intervention:
Principle One: The ability to regain sensory fu-
sion must be determined preoperatively.
Because the patient was intermittently
aligned preoperatively, the torsional compo-
nent was not fully appreciated. Prism and
cover testing alone is insuffi cient evaluation of
sensory function. In this case, prism adapta-
tion preoperatively, double Maddox rod test,
or synoptophore testing could have delineated
the impact of the torsional component. Addi-
tional testing for metamorphopsia, aniseiko-
nia, visual fi eld loss, or ectopic fovea may also
be benefi cial in some patients.
Principle Two: All three axes of deviation must
be addressed.
Small residual deviations in any of the three
axes: horizontal, vertical, or torsional may
repositioning of a muscle, and restrictive
adherence of nonmuscular tissues.
9
SURGICAL CONSIDERATIONS
Strabismus associated with scleral
buckle surgery imposes a unique set of
problems for the strabismus surgeon. Of-
ten, the seeming majority of these cases
involve incomitant deviations. The goal
of surgery is to eliminate diplopia, restore
alignment in the primary position, pre-
serve down- gaze function, and expand
the diplopia- free field. Due to the mul-
tiple etiologic infl uences and prior surgi-
cal intervention, prediction of response to
strabismus surgery is poor and standard
surgical dose tables prove to be unreli-
able. Accomplishing the surgical goal may
depend on removal of the scleral buckle,
band and/or sponge, and determination of
the prospects for this should be planned
in consultation with the retinal surgeon
prior to strabismus surgery. Often, risks
are reduced and removal of the buckle is
feasible if it has been in place for over 6
months. Visual potential and retinal func-
tion, however, may limit the potential for
normal postoperative binocular function.
EVALUATION
As with any surgical intervention in a
patient with strabismus, a thorough or-
thoptic evaluation and determination of
the preoperative potential for sensory fu-
sion postoperatively is mandatory. The de-
tails for the orthoptic and sensory evalu-
ation are covered nicely in this issue by
Hodgetts [see AOJ 62 page??]. However,
a more detailed motility examination is
likely necessary, which can be particularly
helpful in evaluation of patients follow-
ing scleral buckle. Passive forced duction
testing should be assessed in the clinic in
any cooperative patient. The test involves
topical anesthesia followed by the patient
actively rotating the eye opposite to the
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STRUCK
American Orthoptic Journal 3
eratively revealed the expected restriction to
up- gaze. However, active force generation test-
ing revealed a weak inferior rectus duction to
down- gaze. Surgery involved removal of the
buckle with release of the scarring, reattach-
ment of the left inferior rectus muscle (which
was found attached to the posterior aspect of
the buckle), and an “adjustable faden” opera-
tion on the contralateral right inferior rectus
muscle.
This case represents three more important
principles in strabismus surgery after scleral
buckle:
Principle Four: Muscle paresis or weakness
may accompany restrictions.
Direct muscle injury, paresis, and weak-
ness have been described as a complication of
scleral buckle surgery.
11
In this case, the left in-
ferior rectus muscle may have been weakened
by stretching or manipulation as described
by Seaber et al.
3
However, it also was noted
that the insertion of the inferior rectus had
“slipped” or eroded over the buckle, weaken-
ing its effective force. In other cases, proposed
mechanisms for weakening of the muscles in-
cludes cryotherapy, tenotomy, and myotoxicity
from local anesthetic injections.
8, 12, 13
Principle Five: After scleral buckle surgery, the
functional insertion of the muscle may become
the posterior edge of the buckle piece.
The muscle tissue overlying the buckle be-
comes compressed by the space occupying
buckle, and, in this area, the muscle may be-
come ischemic and atrophic.
14
Additionally, the
capsule of scar that forms around the buckle
piece may incorporate the muscle, leaving an
inelastic, encapsulated anterior edge of rectus
muscle. These two forces will often combine to
leave the “new insertion” of the rectus muscle
at the posterior edge of the buckle. This new
attachment point can be surgically identifi ed
as a transition between healthy muscle tissue
and fi brotic tissue. Or, in contrast, it may be
the only area where the muscle attachment
can be located. Suturing of the muscle in this
situation may require the resection of the tis-
sue in front of the posterior edge of the buckle,
thereby causing a “resection effect” by shorten-
ing the lever arm of the muscle attachment. If
the muscle is being advanced in this situation
there may be no need to compensate for this
nding. However, if the surgical plan involves
recession of this muscle, one may consider us-
ing permanent polyester suture material in
order to create the adequate weakening effect
become a barrier to fusion. While many stra-
bismus patients may be able to compensate
for a few degrees of torsion or prism diopters
of residual tropia, patients with a history of
scleral buckle may have mechanical restric-
tions or adhesions or a component of direct
muscle injury or paresis that limits the com-
pensatory vergence mechanisms. These pa-
tients may have a very small residual devia-
tion that prohibits sensory fusion beyond the
expectation for the magnitude of the deviation.
Correction of even a slight deviation may prove
benefi cial to re- establish binocular function
and relieve symptoms.
Principle Three: Lysis of adhesions and buckle
removal alone may not be suffi cient to restore
functional alignment.
Published literature regarding the effect of
removing the buckle alone is minimal; how-
ever, Wong et al.
10
recently reported fi ve pa-
tients with strabismus and diplopia in whom
the sole treatment was removal of the exo-
plant. They found no signifi cant difference in
the median primary position deviation. Fison
et al.
2
found some improvement in deviation
following buckle removal in four patients.
Further, Rosenbaum
5
states that aggressive
dissection of scar, especially if accompanied
by orbital fat may foster recurrent adhesions.
These could potentially be worse than the orig-
inal restriction.
A corollary principle to this fi nding, how-
ever, is: buckle removal may be necessary for
adequate surgical repair of strabismus. I par-
ticularly prefer to remove the buckle entirely
if possible at the time of surgery. The necessity
for using adjustable sutures often requires a
clear space between the original insertion of
the muscle and extending for several millime-
ters posterior (the area where the muscle will
reattach if adjusted). This area is generally
the same area occupied by the buckle band
and element. Removal of the buckle and dis-
section of the capsule around the buckle down
to sclera will allow for the muscle to reattach
to the sclera without hindrance. Additionally,
it eliminates one of the mechanisms of stra-
bismus, which is the redirection of muscle
forces caused by the buckle itself.
CASE TWO
A 49-year- old man presented with a 12
Δ
left
hypotropia that increased on up- gaze and re-
versed on down- gaze. No torsion was noted and
the patient had sensory fusion with a chin-up
head posture. Passive forced ductions preop-
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4 Volume 62, 2012
table before the muscles are reattached and
before the conjunctiva is closed. Fat adherence
syndrome
15
is also noted in the strabismus af-
ter scleral buckle procedures. Adequate cor-
rection may require meticulous dissection
of adherence followed by intensive topical or
local steroid to limit recurrence. The buckle
and the capsule around the buckle itself can
contribute to these adhesions.
3
Large sponge
pieces or the sleeve of the buckle band can be
the nidus for these lease adhesions. Finally, as
depicted in this case, conjunctival foreshorten-
ing may itself limit the rotations of the eye and
successful alignment and motility may require
conjunctival recession.
Principle Eight: Ocular alignment deviations
may have multiple causes.
The above case illustrates the oblique
muscle adherence syndrome.
16
The inferior
oblique muscle in this situation is pulled into
the encircling buckle and scarred to the sclera.
This causes an up- gaze defi cit, dramatic ex-
cyclotorsion, and hypotropia. However, the
inferior rectus muscle is often also restricted.
This additional restriction adds to the hypot-
ropia and up- gaze defi cit. A third factor may
be the buckle piece itself, lying under the infe-
rior rectus and changing the force vector of its
effect. Without addressing the multiple etio-
logic causes of the deviation, surgical under-
correction would result. In a similar fashion,
incarceration of the superior oblique and su-
perior rectus restriction have been described
both contributing to a hypotropia and down-
gaze defi cit.
1
CONCLUSIONS
Strabismic deviations following retinal
surgery are not simply restrictive in origin.
Multiple etiologies including muscle weak-
ening or paresis, redirection of muscle
forces, malpositioning or repositioning of
a muscle itself, and restrictive adherence
of nonmuscular tissues frequently act
in combination with muscle restrictions
and the sensory disturbances found af-
ter scleral buckling surgery. The surgical
goals of eliminating diplopia in primary
position, preserving down- gaze function,
and expanding the diplopia- free visual
eld can be accomplished by observing the
surgical principles outlined above.
without the problem of nonadherence or posi-
tioning of the attachment forces too far pos-
terior.
Principle Six: Strabismus surgery on the fel-
low eye may be necessary or suffi cient for the
best outcome.
Achieving an expansion of the diplopia- free
eld will sometimes require matching force
vectors of the fellow eye with the eye that
has limitations to full excursion. In the case
outlined above, the infraducting force of the
affected eye was notably weak. However, be-
cause of the restrictions caused by the buckle
and fi brosis, the eye was hypotropic not hy-
pertropic as one might have predicted. Simply
advancing the muscle to restore depression
forces in this case would have worsened the
hypotropia. By operating on the contralateral
agonist muscle, and creating a “fi xation du-
ress” to down- gaze, the muscle forces on both
eyes with attempted down- gaze are made more
equivalent, without compromising the align-
ment in primary position.
In some cases, the deviation after scleral
buckle surgery may occur without restriction
and be measured as completely concomitant. If
this happens, the strabismus surgeon may be
able to successfully operate on the nonscleral
buckle eye, with standard strabismus tech-
niques, to reestablish normal motility.
CASE THREE
A 30-year- old man presented with a 16
Δ
right
hypotropia, increasing on up gaze with a se-
vere up gaze defi ciency of the affected eye.
Additionally, 14° of excyclotorsion localizing
to this eye was noted. He had chronic diplopia
and no area of single binocular vision; however,
he was able to demonstrate binocular sensory
fusion on synoptophore testing. Passive forced
ductions revealed a complete restriction to
up- gaze. Surgery involved a recession of the
right inferior rectus muscle, inferior oblique
myectomy, conjunctival recession and release
of scarring.
This case outlines two fi nal principles in
dealing with strabismus following scleral
buckle:
Principle Seven: Surgical under- correction
may result from nonmuscular restrictions.
Leash and reverse leash adhesions have
been described contributing to the limitations
of movement and surgical under- corrections.
Rosenbaum
5
recommends frequent assess-
ment of the passive ductions on the operating
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STRUCK
American Orthoptic Journal 5
6. Wright LA, et al.: Motility and binocularity out-
comes in vitrectomy versus scleral buckling in
retinal detachment surgery. Graefes Arch Clin
Exp Ophthalmol 1999; 237:1028– 1032.
7. Hilton GF, Tornambe PE: Pneumatic retinopexy:
An analysis of intraoperative and postoperative
complications. The Retinal Detachment Study
Group. Retina 1991; 11:285– 294.
8. Bell FC, Pruett RC: Effects of cryotherapy upon
extraocular muscle. Ophthalmic Surg 1977;
8:71– 75.
9. Guo S, et al.: Diplopia and strabismus follow-
ing ocular surgeries. Surv Ophthalmol 2010; 55:
335– 358.
10. Wong V, et al.: The effect of scleral exoplant re-
moval on strabismus following retinal detach-
ment repair. J AAPOS 2011; 15:331– 333.
11. Spencer AF, Newton C, Vernon SA: Incidence of
ocular motility problems following scleral buck-
ling surgery. Eye 1993; 7:751– 756.
12. Hamlet YJ, Goldstein JH, Rosenbaum JD: De-
hiscence of lateral rectus muscle following in-
trascleral buckling procedure. Ann Ophthalmol
1982; 14:694– 697.
13. Guyton DL: Strabismus complications from lo-
cal anesthetics. Semin Ophthalmol 2008; 23:
298– 301.
14. Wolff SM: Strabismus after retinal detachment
surgery. Trans Am Ophthalmol Soc 1983; 81:
182– 192.
15. Wright KW: The fat adherence syndrome and
strabismus after retina surgery. Ophthalmology
1986; 93:411– 415.
16. Kushner BJ: The inferior oblique muscle adher-
ence syndrome. Arch Ophthalmol 2007; 125:
1510– 1514.
Key words: strabismus, vitreo- retinal
surgery, scleral buckle
Meticulous preoperative assessment
and orthoptic evaluation with attention to
all the axes of alignment and preoperative
binocular visual potential is crucial to for-
mulating a successful surgical plan. Ancil-
lary testing is often indicated and opera-
tion on the fellow eye may be necessary for
the best functional outcome. Preoperative
consultation with the retina surgeon, for
potential removal of the buckle, should be
sought in all cases if possible. Adjustable
suture strabismus surgery should be en-
couraged in these cases, as the standard
surgical dose tables prove inaccurate.
Strabismus surgery can be quite success-
ful in accomplishing the goals outlined in
this discussion; however, the patient also
needs to understand that complete recov-
ery of muscle function and normal motility
is usually not possible.
REFERENCES
1. Munoz M, Rosenbaum AL: Long- term strabismus
complications following retinal detachment sur-
gery. J Pediatric Ophthalmol Strabismus 1987;
24:309– 314.
2. Fison PN, Chignell AH: Diplopia after retinal
detachment surgery. Br J Ophthalmol 1987; 71:
521– 525.
3. Seaber JH, Buckley EG: Strabismus after reti-
nal detachment surgery: Etiology, diagnosis, and
treatment. Semin Ophthalmol 1995; 10:61– 73.
4. Farr AK, Guyton DL: Strabismus after retinal de-
tachment surgery. Curr Opin Ophthalmol 2000;
11:207– 210.
5. Rosenbaum AL: Strabismus following retinal de-
tachment surgery. Am Orthopt J 2001; 51:47– 53.
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  • [Show abstract] [Hide abstract] ABSTRACT: Thirty-three consecutive patients with persistent strabismus following retinal detachment surgery were studied retrospectively. A large number of vertical and torsional problems were seen. Various restrictive abnormalities were identified during strabismus surgery. These included superior oblique tendon displacement anteriorly, leash and reverse leash types of restrictions, myoscleral adhesions posterior to the exoplants, and stretching of the muscles induced by large underlying exoplants. The results following strabismus surgery were analyzed. Eighty percent of the patients were able to achieve single binocular vision in the primary field of gaze, with a low incidence of complications. The adjustable suture procedure was thought to be helpful.
    Article · Nov 1987
  • [Show abstract] [Hide abstract] ABSTRACT: Diplopia following retinal detachment usually responds to simple measures. Fifteen out of 311 cases developed diplopia lasting more than three months after conventional retinal detachment surgery. Binocular single vision was restored in 12 of the 15 cases (80%). The mean follow-up was four years. Diplopia was eliminated stepwise. If prisms were ineffective, our first surgical procedure was removal of the scleral buckle. If the retina was flat, we were prepared to remove the buckle early. When diplopia persisted after buckle removal, we proceeded to strabismus surgery. Our most consistent results followed strabismus surgery on the untreated eye. Prisms alone restored binocular single vision in six patients (40%), one of whom preferred to adopt a compensatory head posture. Removal of the scleral buckle restored binocular single vision in three patients (20%), with the help of a prism in one case and a compensatory head posture in another. Binocular single vision was restored after buckle removal and strabismus surgery in three further patients (20%), one requiring a prism in addition. Binocular single vision was not restored in three patients (20%).
    Article · Aug 1987
  • [Show abstract] [Hide abstract] ABSTRACT: Between 5% and 25% of patients may experience persistent diplopia after surgery for retinal detachment. The complexity of the presentation poses a distinct challenge to both the retinal and the strabismus surgeon. Careful evaluation to determine factors contributing to the strabismus and assessment of fusional capabilities are essential before treatment. A combination of the appropriate surgical approach with nonsurgical adjuncts such as prisms or botulinum toxin is often successful in relieving symptoms.
    Article · Apr 1995
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