Strabismus is misalignment of eyes resulting
in failure of the two eyes to simultaneously focus on the same image, leading
to loss of binocular single vision1. The incidence of adult
strabismus is estimated to be 4%2. Strabismus may be present in
adults for a variety of reasons, including uncorrected or consecutive childhood
strabismus, thyroid eye disease, decrease vision in one eye, and surgical
trauma to the extra ocular muscles. Strabismus in adults may be associated with
diplopia, torticollis, impaired stereopsis, and negative psychosocial
effects3. Strabismus
surgery in adults has a high rate of success and has been shown to be
beneficial in improving diplopia, binocular fusion, and psychosocial well being4.
Furthermore, adult strabis-mus surgery has been shown to be cost effective,
with a cost equivalent to cataract surgery5.
Unusual results after strabismus surgery
have been frustrating for both surgeon and patient. The adjustable suture
surgical technique offers the surgeon the opportunity to place the eye in the
required position within one day to few hours after surgery6. This
technique allows the surgeon to fine adjust ocular alignment in the period just
after surgery while patient is awake and free of the effects of anesthesia
gases. The improved adjustable suture technique has improvised surgical results
in strabismus patients and has markedly reduced the number of redo’s,
especially in more complicated cases7.
The adjustable suture technique is most
effective in patients with complicated strabismus such as paralytic strabismus,
large angle strabismus, reoperations, thyroid myopathy, and advancement of a
lost or slipped muscle. In contrast, the adjustable suture technique has
limited application in the patient with restrictive strabismus secondary to fat
adherence syndrome, in which scarring of the globe or eye muscle causes the
strabismus8.
Selection of patient is important, if not
crucial, for successful implementation of the adjustable suture technique. The
adjustment procedure is somewhat uncomfortable and in some patients evokes
substantial anxiety. The cotton-swab test, which consists of touching a cotton
swab to the medial or lateral aspect of the bulbar conjunctiva, is a simple yet
accurate way of identifying patients who will be suitable for the adjustment
procedure. If the patient is able to tolerate manipulation of the bulbar
conjunctiva without topical anesthetic, then he or she should do well with the
adjustment procedure. Other indications of a patient’s suitability for
the adjustable suture technique include his or her facility with contact lenses,
ability to undergo applanation tonometry, facility with topical drops, or
cooperation with forced duction testing. It is mandatory to advise patients
that the adjustment procedure will be uncomfortable, and it is best to avoid
patients who are unwilling or fearful of the procedure9.
In this study all operations were performed
under general anesthesia and the adjustment was done in the recovery room after
6 hours.
MATERIAL AND METHODS
The research ethical committee of LRBT Free
Base Eye Hospital, Karachi approved this study. A retrospective record review
was done of all the patients who had undergone strabismus surgery by adjustable
suture technique for exotropia in the practice of one surgeon (MS) from April
2010 to March 2011. The
data collection was performed by two investigators (ZK and SAB) independently
of the surgeon. There were 13 (72.2%) males and 5 (27.7%)
females out of 18 patients. Age ranged from 16-30 years ± 4.30. All
patients had exotropia (Fig 1) with a range of deviation from 30 prism dioptres
to 80 prism dioptres with a mean of 60 prism dioptres. Patients having previous
strabismus surgery, congenital sixth nerve palsy were excluded from the study.
All
the patients had a preoperative ocular exami-nation and orthoptic assessment,
including angle of deviation for near (1/3m) and distant vision (6m) with and
without correction, and measurement by prism cover test. Fusional ranges were
also measured by prism. Written consent was obtained from all patients or first
degree relatives. All patients were followed up to 6 months. The main outcome
measures were a need for reoperation, patients’ satisfaction with regard
to final cosmetic appearance and change in angle of deviation at the end of
follow up.
The
statistical analysis of the data was done by the software Statistical Package
for Social Sciences (SPSS) version 17. Descriptive statistics were calculated
in terms of mean, standard deviation, minimum, maximum and range. Mean and
standard deviation were calculated for quantitative variable like age of the
patients. Frequency and percentage were calculated for gender, cosmetic
appearance and rate of re-operations. Paired sample test was used to calculate
p-value, and p-value of < 0.005 was considered significant.
Surgical Technique
The
eye was prepared and draped in the usual ophthalmic manner. Two fixation
sutures with 6-0 silk were inserted near limbus at the points perpendicular to
the muscles to be operated upon (that is, at 12 and 6 o’clock for horizontal
muscle operation). Recession was done first. A limbal conjunctival approach was
used with radial relaxing incisions. A double-armed 6-0 vicryl suture on a fine
spatulaled needle was placed near its insertion and locked at the sides with a
double-throw knot to prevent bunching up of the muscle. The muscle was then
cut. The arms of the suture were passed through the scleral tunnel starting
near each end of insertion and emerging 1.5 mm apart. The suture was then
secured with a double throw knot followed by half bow. Any redundant suture was
shortened. Subsequent adjustment in all cases is eased by ability to fix globe
which is best done with the aid of a bucket – handle suture with 6
– 0 vicryl placed in the sclera at or near the insertion. Resection of the
antagonist if indicated was done as in conventional strabismus surgery.
The
patient was seated up on the table after the general anesthesia effect wore
off. The deviation was measured for near and far distant vision by a prism
cover test by an orthoptist (Fig. 2). Propracaine1% eye drops were instilled
and adjustment was made until the deviation was less than 15 PD in the primary
position, with no abnormal head posture (Fig. 3). The conjunctival incision was
closed and the eye was padded for one more hour.
RESULTS
Eighteen eyes of eighteen patients who were
operated for exotropia ranging from 30 PD to 80 PD with a mean of 60 PD by
adjustable suture technique in LRBT Free Base Eye Hospital Karachi. There were
13 (72.2%) males and 5 (27.7%) females out of 18 patients. Sixteen out of
eighteen (88.8%) patients were satisfied with their cosmetic appearance (table
1). One out of eighteen (5.55%) patients needed reoperation because
Fig. 1: Right
eye Exotropia (pre-operative)
Fig. 2: Post-surgery orthoptic
assessment
Fig. 3: Post-adjustment
of
residual exotropia of 30 PD (table 2). Mean change in angle of deviation at the
end of follow up was from 60.55 ± 11.75PD to 15.22 ±
5.15 PD with a percentage change of 74.62%
(p= 0.000).
The
paired sample test, statistics and correlations are illustrated in table 3, 4
and 5 respectively.
DISCUSSION
Adjustable
strabismus surgery first described by Jampolsky10, it has the
advantage of decreasing the redo surgeries and increasing the accuracy of end point
in strabismus correction which has resulted in more surgeons opting for this
technique in cooperative patients11. The post operative
adjustment of the rectus muscle in two stages is commonly used, while an intra
operative adjustment in one stage under local anesthesia is less commonly done12.
Intra operative one stage adjustment has been limited in literature to few
patients because it is a lengthy and tedious task & requires an experienced
surgeon, as well as a cooperative candidate.13 However, in a two
stage adjustment procedure, there is usually time gap between surgery and
starting adjustment. Some surgeons do adjustable surgery using retrobulbar
anesthesia rather than general anesthesia, but the patient and surgeon should
wait until the anesthetic effect wears away6.
In this study all operations were performed under
general anesthesia and the adjustment was done on recovery room after 6 hours.
In this study mean change in angle of
deviation at the end of follow up was 74.62%, whereas in another study average
change in angle of deviation was 87.5%14. Melhuish and Kemp
presented a series of 20 patients operated using adjustable sutures and
claiming an 85% success rate15.
Zhang M S also reported 74.8% success rate
in patients undergoing strabismus surgery by adjustable suture method.16 In
this study Sixteen
out of eighteen (88.8%) patients were satisfied with their cosmetic
