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NR 10-12/2008
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The reduction of A-V
patterns with oblique muscles overaction in unilateral and
bilateral surgery
Redukcja zespołów literowych
z nadczynnością mięśni skośnych w zabiegach jedno- i
obustronnych
Olimpia Nowakowska1, Anna
Broniarczyk-Loba2, Piotr J. Loba1
1 Department Ophthalmology and Ophthalmology Clinic
of Medical University of Łódź
Chief: Professor Wojciech Omulecki, MD, PhD
2 Department Pathophysiology Binocular Vision and
Strabismus Therapy of Medical University of Łódź
Chief: Anna Broniarczyk-Loba, MD, PhD |
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| Summary: |
Purpose: A-V
strabismus patterns may occur with or without oblique
muscles overaction and thus require different surgical
approach. The aim of our study was to evaluate the
efficacy of unilateral vs bilateral surgery for A and V
pattern strabismus in children with oblique muscles
overaction.
Material and methods: A retrospective review of
45 children with oblique muscles overaction was
performed. All children underwent unilateral or
bilateral oblique weakening procedures over a period of
2 years. The mean reduction of A-V pattern angle was
measured in all groups.
Results: Among the patients with V pattern,
treated with unilateral surgery the mean angle reduction
was 11.8∆ ± 6.26∆ and among those who underwent
bilateral procedure it was 17.06∆ ± 8.46∆. In A pattern
group the mean angle reduction were 8.0∆ ± 2.82∆ and
15.0∆ ± 8.9∆ respectively.
Conclusions: The bilateral oblique weakening
procedure is significantly more effective (p<0.01) in
reducing the angle in A-V patterns than the unilateral
surgery. It appears that in A pattern with superior
oblique overaction the bilateral surgery gives better
results than in V pattern with inferior oblique
overaction. |
| Słowa kluczowe: |
strabismus, A and V
patterns, strabismus surgery. |
| Key words: |
zez, zespoły A i V,
leczenie chirurgiczne zeza. |
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Background and objective
Alphabetical patterns A and V are conditions in which the
strabismus’ angle is different in down and up gaze. The
incidence of those entities ranges from 12% to 50%, of all
strabismus’ patients (1). They may coexist with esotropia or
exotropia and with or without oblique muscles overaction. A
pattern may be diagnosed when the difference between angles
measured in up and down gaze is greater than 10∆ and V pattern
when greater than 15∆ (2).
Several theories concerning the etiology of A-V patterns have
been proposed. Most authors suggest that oblique muscle
dysfunction plays a major role (1). On the other hand those
entities may originate from abnormal rectus muscle insertions or
pulley anomalies (3,4).
Surgery is the only effective treatment reported in the
literature (1,2,5). The amount of the surgery needed, depends on
the presence of oblique muscle overaction, primary position and
down-gaze alignment, binocular function, torsion and anomalous
head posture. As the oblique muscle dysfunction is considered to
be a major cause of A-V patterns the surgery on those muscles is
recommended (5,6). The procedure may be performed unilaterally
or bilaterally depending on the magnitude of the overaction (1).
In cases with clinically dominant inferior oblique overaction,
graded recession and anterior transposition is suggested (7).
Tucking should be performed in patients with superior oblique
underaction and tenotomy or silicon expander implantation are
used in it’s overaction (2,8).
The aim of this study was to evaluate the reduction in
strabismus angle in vertical gaze positions in children with A
and V patterns and oblique muscle overaction, after unilateral
and bilateral surgery.
Patients and Methods
A retrospective review of 45 children 3 to 14 years old (mean
8.97 ± 3.84) that had undergone a surgery in our department for
A or V pattern over a period of 2 years (2003-
-2005) was performed. The inclusion criterion was oblique
muscles dysfunction. The studied group consisted of 35 patients
(15 males, 20 females) with V pattern and 10 patients (5 males,
5 females) with A pattern strabismus. The follow-up period
ranged from 6 to 12 months.
A complete history was taken and the patients underwent full
ocular and orthoptic examination. The ocular alignment in
primary position, upgaze and down-gaze were measured by a
prismatic cover test before and after the surgery.
In most patients oblique muscle dysfunction coexisted with
horizontal strabismus. In 18 (40%) patients there was V
esotropia, in 16 (35.5%) V exotropia, in 7 (15.5%) A esotropia
and in 3 (6.7%) A exotropia. In just one case (2.3%) with V
pattern, in primary position there was no horizontal deviation.
To adjust ocular alignment, a number of surgeries were performed.
Patients with V pattern undergone inferior oblique weakening
procedures, which were in 43% bilateral. In a total of 50
muscles, tenotomy was performed on one muscle, 34 muscles were
recessed in ‘+1’ overaction, 12 muscles in ‘+2’ and recession
and anterior transposition was done on 3 muscles in ‘+3’. There
were no cases with ‘+4’ overaction in the studied group.
In patients with A pattern and superior oblique overaction,
various width of tenotomy was performed. In a total of 18
muscles, 1/3 of the tendon was incised in 9, 1/2 in 7 and 2/3 in
2 muscles. Bilateral surgery was performed in 8 (80%) cases.
In many patients rectus muscle adjustments were indicated. In 11
patients one horizontal rectus muscle was involved, in 17 two,
in 6 three and in 2 four muscles. In 9 cases there was no
indication for rectus muscle surgery, mostly because oblique
muscle surgery positively influenced the horizontal alignment.
Only in 5 patients adjustment of vertical muscles was required.
In 3 patients one muscle was operated and in 2 patients three
muscles were operated. In most cases the surgery was performed
in two or three stages.
Results
We have assessed the effectiveness of the surgery performed by
measuring the mean reduction of the alphabetical patterns.
Pattern value was calculated for each patient by subtracting the
measured angle in up- and down-gaze. The angle reduction was
calculated by subtracting the pattern values from before and
after the surgery. In general, mean angle reduction found after
unilateral surgery was 5.82∆ ± 3.35∆ and 8.96∆ ± 5.13∆ after
bilateral surgery. By means of statistical analysis, using
t-test, we found that the angle reduction in A-V patterns was
significantly (p<0.01) higher after bilateral surgery.
Discussion
Among our patients V esotropia was more common than V exotropia,
A esotropia and A exotropia. V patterns contributed for 75.5% of
all cases what is similar to the incidence reported by Rizk and
Taalab (5). In their study they found A pattern in only 13.2%
and slightly higher frequency of exotropia to esotropia. Similar
study made by Arezzo et al. (9) also indicates the dominance of
V pattern (69.4%), but with a higher incidence of esotropia
(37.75%) what is more consistent with our results. Ohba et al.
(10) reports 90.3% of exotropes in which 51.6% were V patterns.
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All patients with V
pattern underwent unilateral (57%) or bilateral (43%) graded
recession of inferior oblique muscle. Similar procedure was
carried out by Monteiro de Carvalho et al. (7) in 53 patients
with V pattern and +1 to +3 inferior oblique overaction. In
their study satisfactory result (V pattern less or equal to 8∆)
was achieved in 57% to 75% depending on the basic deviation.
Better results were attained in patterns that were less than 20∆
and more disappointing in those over 29∆. In all cases
considered as satisfactory undercorrection was noted.
Caldeira (6) performed a bilateral inferior oblique recession in
22 patients with V pattern exotropia, although he encountered
bilateral overaction only in 86.4%. After the surgery 72.7% of
his patients had the deviation under 15∆ and in this group 36.4%
had it totally eliminated. On the basis of his research he
suggests, that bilateral inferior oblique recession is the most
effective procedure in such cases.
In the group with A pattern we conducted unilateral (20%) or
bilateral (80%) superior oblique weakening procedure. We incised
the tendon form 1/3 to 2/3 of its width. Rizk and Taalab (5)
proposed a variety of superior oblique weakening procedures.
They performed not only tenotomy, but also tenectomy,
Z-tenotomy, recession to the nasal margin of superior rectus
with posterior transposition and silicon expander implantation.
The authors proposed a detailed algorithm for the management of
A-V patterns.
Surgery on the horizontal muscles was needed in 36 and on
vertical muscles in 5 patients. The necessity of operating on
oblique, horizontal or sometimes vertical muscles is unanimously
underlined by other strabologists (1,5). Caldeira (8) states
even that recession of the inferior oblique muscle, particularly
bilateral, may induce vertical disparity.
Rizk and Taalab (5) estimated the joint decrease of the A-V
pattern value at 19.6∆. The amount of the surgery performed in
their study was not limited to one or both oblique muscles but
was extended to 3 or 4 oblique muscles in some cases. In their
estimations they have also included vertical muscles
transpositions. Similar reduction measurements were carried out
in the paper by Ohba et al. (10,11) giving the mean of 10.3∆ for
V pattern and 20.3∆ for A pattern.
Conclusions
The bilateral oblique weakening procedure is significantly more
effective (p<0.01) in reducing the angle in A-V patterns than
the unilateral surgery. It appears that in A patterns with
superior oblique overaction the bilateral surgery gives better
results than in V pattern with inferior oblique overaction.
Refferences:
1. Von Noorden GK: Binocular Vision and Ocular Motility. Theory
and Management of Strabismus, 6th ed., St. Louis, PA: Mosby
2002, 396-413.
2. Wright KW: Pediatric Ophthalmology and Strabismus, 1st ed.,
St. Louis, PA: Mosby 1995, 203-209.
3. Urist MJ: Horizontal squint with secondary vertical
deviations. Arch Ophthalmol 1951, 46, 245.
4. Clark RA, Miller JM, Rosenbaum AL, Demer JL: Heterotopic
muscle pulleys or oblique muscle dysfunction? JAAPOS 1998, 2,
17.
5. Rizk A, Taalab AA: V Patterns Strabismus: Clinical
Characteristics & Guidelines for Surgical Treatment.
Transactions of the 30 th ESA Meeting 2005, 251-254.
6. Caldeira JA: Some clinical characteristics of V – pattern
exotropia and surgical outcome after bilateral recession of the
inferior oblique muscle: a retrospective study of 22 consecutive
patients and a comparison with V – pattern esotropia. Binocul
Vis Strabismus Q 2004, 19, 139-150.
7. Monteiro de Carvalho KM, Minguini N, Dantas FJ, Lamas P, Jose
NK: Quantification (grading) of inferior oblique muscle
recession for V – pattern strabismus. Binocul Vis Strabismus Q
1998, 13, 181-184.
8. Caldeira JA: V – pattern esotropia: a review; and a study of
the outcome after bilateral recession of the inferior oblique
muscle: a retrospective study of 78 consecutive patients.
Binocul Vis Strabismus Q 2003, 18, 35-48.
9. Arezzo C, Guccione L, Parrilla R, Placentino L: Of
Neurological Disorders In A – V Pattern. Transactions of the
30th ESA Meeting 2005, 247-250.
10. Ohba M, Nagakawa T: Treatment for „A” and „V” exotropia by
slanting muscle insertions. Jpn J Ophthalmol 2000, 44, 433-
-438.
11. Ohba M, Ohtsuka K, Osanai H: Treatment for A and V
strabismus by slanting muscle inse rtions. Binocul Vis
Strabismus Q 2004, 19, 13-20.
Praca wpłynęła do redakcji 04.04.2008 r. (1043)
Zakwalifikowano do druku 20.10.2008 r.
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