Download Efficacy of Hangback Inferior Oblique Recession in the Management

74th AIOC 2016, Kolkata
This paper was conferred with the AIOS prem prakash disha Award for the BEST PAPER of SQUINT Session.
Efficacy of Hangback Inferior Oblique
Recession in the Management of Superior
Oblique Palsy
Dr. Prolima Thacker
S
uperior Oblique Palsy (SOP) is one of the most commonly occurring
isolated cranial nerve palsies seen by the strabismologist. It may be
congenital (most common) or may result from trauma, a microvascular
accident or a mass lesion.1,2,3,4,5,6
Weakening of the inferior oblique (the direct antagonist of superior oblique)
is the most commonly performed surgery in superior oblique palsy,
particularly in Class 1 cases (Knapp’s Classification).7 Here we describe
a new technique of inferior oblique muscle weakening – the hangback
recession- in the management of unilateral and bilateral SOP.
Hang-back muscle recession and its various modifications have been used
mainly for recessing recti.8 However, its efficacy on obliques has not been
extensively studied so far.
MATERIALs AND METHODS
This prospective study was conducted over a period of 9 months at Guru
Nanak Eye Centre, New Delhi. Cases were selected from patients attending
the Squint Clinic of the centre. In this study, we included patients having
unilateral or bilateral SOP with Inferior Oblique Over Action (IOOA)
ranging from 15 to 30 PD as measured by prism bar cover test in lateral
gaze. Those requiring simultaneous surgery on a cyclovertical muscle other
than inferior oblique, history of previous extraocular muscle surgery, and
those with comitant or restrictive strabismus were excluded. All patients
underwent a complete ophthalmologic assessment including history, visual
acuity, ductions and versions, prism cover test in all cardinal positions at
distance and near, slit-lamp, posterior segment examination, and cycloplegic
refraction.
We quantified IOOA by measuring the amount of hypertropia in lateral
gaze. IOOA was graded as follows:
Mild IOOA <15 PD
Moderate IOOA 15-30 PD
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Severe IOOA >30PD
Amount of hang back IO recession performed depended on the grading of
IOOA
Mild IOOA- 8mm recession
Moderate IOOA- 10 mm recession
Severe IOOA 12mm recession
Since all our patients had moderate IOOA, we performed 10mm unilateral
or bilateral hangback IO recession in all patients. Simultaneous horizontal
rectus surgery was performed if primary position horizontal deviation was
present.
Surgical Procedure- All surgeries were performed by the same surgeon
(KK) with an operating microscope using low magnification. The lateral
rectus bridle suture was passed and retracted to expose the inferolateral
quadrant of the eye. A fornix conjunctival incision was made in the
inferolateral quadrant 8 mm from the limbus, and Tenon’s capsule was cut
perpendicular to the conjunctival incision to expose bare sclera. Dissection
of Tenon’s capsule was performed to identify the inferior oblique muscle, and
the fascial attachments of the muscle were cut under direct visualization. A
muscle hook was positioned under the belly of the inferior oblique muscle
under direct visualization to avoid injury to the muscle sheath and the
vortex vein.
A double-armed 6-0 polyglactin 9-0 suture was passed 5 mm from the
insertion site through the width of the inferior oblique muscle, with locking
bites on both ends. The same suture was then passed proximally 3 mm from
the insertion site in a loose fashion. In this way loops were formed between
the proximal and distal suture bites on the inferior oblique muscle. The
intermediate area between the two suture lines was then cut. The proximal
part of the severed muscle was then suspended from the distal muscle end.
The amount of recession to be performed was then measured on both arms
of the polyglactin suture. While the surgeon held the suture with the help of
smooth forceps, the proximal ends of the sutures were tied.
The proximal portion of the muscle was allowed to retract into its sheath
and was expected to stay recessed according to the amount of recession,
preserving the normal course of the muscle. Horizontal muscle surgery was
performed if required, depending on the amount of deviation in primary
gaze. Conjunctiva was then closed using 6-0 polyglactin 910 sutures. The
operated eye(s) was covered with a pad and bandage for 12 to 18 hours.
Topical steroid/antibiotic combination was prescribed for the operated eye
for 1 week, commencing when the patient arrived home. Outpatient followup lasted for at least 3 months.
74th AIOC 2016, Kolkata
RESULTS
We performed hang back recession of inferior oblique in 15 patients of
superior oblique palsy. The mean age was 16.7± 8.9 years. Of these, 8 patients
were females and 7 were males. 12 patients had congenital sop while only
three cases were acquired in nature, of which, all 3 were post – traumatic
palsies. 4 patients had unilateral sop while the rest 11 had bilateral affection.
Vertical deviation in primary position ranged from 10PD to 24PD with a
mean deviation of 20PD± 4PD. Amount of IOOA was measured in lateral
gaze using prism bars and IOOA was graded as described above. All 15
patients had moderate IOOA. We performed 10 mm hang back recession
in 26 eyes of 15 patients. Patients were followed up biweekly for the first
month and monthly afterwards. Final residual IOOA was measured at the
end of 6 months. Success was defined as residual IOOA<5PD at 3 months
post-op. We found that vertical deviation in primary position was reduced
to 4±1PD and IOOA was reduced to an average of 7± 2 PD, with 24 eyes
having a residual IOOA of <5PD. In 2 eyes, residual IOOA was found to be
12 PD and 14 PD respectively.
DISCUSSION
With the help of this study, our aim is to describe a suspension technique to
weaken the inferior oblique muscle in patients of superior oblique palsy. We
performed a 10 mm suspension recession weakening of the inferior oblique
muscle in 26 eyes of 15 patients with SOP and studied its efficacy with
regard to the amount of residual IOOA and primary position hypertropia
at the end of 6 months following surgery.
A variety of procedures to weaken the inferior oblique muscle have been
described in literature.9 In the beginning, myotomy was the procedure of
choice. However, the severed ends of the cut muscle had the tendency to
reunite. To avoid this, myectomy, which included removal of a section of the
muscle to prevent the myotomized ends from re-uniting, became popular.
Disinsertion at the scleral attachment of the inferior oblique muscle is
another technique of IO weakening. However, the reattachment rate of the
inferior oblique tendon is not predictable. In Parks method of IO recession,
a 10-mm recession requires placement of the anterior suture 2 mm temporal
and 3 mm posterior to the temporal insertion of the inferior rectus muscle,
with the posterior suture placed 3 mm more posteriorly.9 Because the
inferior oblique muscle inserts near the macula, there may be concern
about penetration of the macula which can cause macular hemorrhage,
visual impairment, or visual loss. Also, performing the procedure within
a small operative field with limited visibility is more difficult compared
to a myectomy or disinsertion. Elliott and Nankin10 modified the standard
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recession procedure by transposing the inferior oblique muscle anteriorly
toward the insertion of the inferior rectus muscle. Anterior and nasal
transposition of the IO is a relatively new procedure devised by Stager
et. al.11 It is recommended for patients who have bilateral marked inferior
oblique overaction with dissociated vertical deviation. Besides these
procedures, denervation, with or without, extirpation is seldom done for
weakening the inferior oblique muscle.12
However, there is still no gold standard procedure for weakening the inferior
oblique muscle. In our study, many advantages of hangback recession of
inferior oblique over conventional recession were noted, including (1)
no need to identify anatomical landmarks for scleral suturing; (2) this
procedure avoids both intra scleral suturing, which risks scleral perforation,
and snaring of Tenon’s capsule; and (3) it incorporates other advantages of
hangback recession, such as the potential for postoperative adjustment. We
hypothesized that suspension of the inferior oblique muscle is as efficacious
as conventional recession and, in addition, eliminates these drawbacks. It
also offers a theoretical advantage of intra- or postoperative adjustment
of the inferior oblique muscle. In this study we obtained a mean IOOA
correction of 21± 2 PD and mean reduction in primary position hypertropia
of 16±2PD after performing a 10 mm suspension in cases having moderate
IOOA.
In a longitudinal study by Shipman et. al., a standard 10mm recession in
superior oblique palsy reduced the hyperdeviation by a median of 8 PD in
primary position and by 16 PD in contralateral gaze.13 Cooper and Sandall
stated that a measured recession will decrease the hyperdeviation by 6.88
PD in primary position and by 12.3 PD in the field of action of the overacting
inferior oblique muscle.14 This compares well with Kutschke and Scott who
found a reduction of 6.9 PD in primary position and 15.6 PD in contralateral
gaze.15 Mittleman and Folk reported a decrease of 9 PD from a 10–12 mm
measured recession.16 Our method of hangback recession has shown better
results in both these parameters. Kamlesh et. al. performed hangback
recession of IO to correct V pattern and obtained satisfactory results with
an average V-pattern correction of 20±5PD, 19± 2PD for the V-exotropia
group, and 22± 7PD for the V-esotropia group.17 Our hypothesis is that,
like inferior oblique myectomy, suspension recession of the inferior oblique
muscle makes it possible for the muscle to adjust its postoperative recession
according to the inherent tension in the muscle.
The limitations of this study include the small sample size and lack of
controls: it included patients with both esotropia and exotropia and
patients undergoing unilateral as well as bilateral procedures. In 2 eyes,
residual IOOA was found to be 12 PD and 14 PD respectively. This was
74th AIOC 2016, Kolkata
seen in a patient who had bilateral IOOA of 28PD. In this case, IO was re
explored and its anterior transposition was done with satisfactory results.
In retrospect, we felt that this under correction could have occurred due
to miscalculation of IOOA preoperatively. Also, short-term follow-up is not
helpful with oblique muscle surgery because inferior oblique overaction is
known to recur gradually over 2 years while in our study; the follow up
period was only 6 months.9
In conclusion, suspension recession of the inferior oblique muscle offers
another method for weakening its overaction to correct the over elevation in
adduction. This procedure seems to offer a theoretical advantage for intra
or postoperative adjustment, which deserves further investigation.
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