Strabismus - Fundamentals of Clinical Ophthalmology.pdf

STRABISMUS
more persistent diplopia. It is in this group of
patients that the argument for adjustable sutures
is strongest. The alignment can be corrected in
the ward or the clinic under local anaesthesia.
Lost or slipped muscles
The fascial connections between the oblique
muscles and the inferior, lateral and superior
rectus muscles make recovery of any one of these
muscles easier than the medial rectus, which is
the commonest muscle to lose its attachments
completely. In our experience in nearly every
case, a lost medial rectus muscle remains in the
sub-Tenon’s space, and a careful search with the
operating microscope should be made, though
the muscle may be found as far back as the optic
nerve. The surgeon should be extremely
cautious venturing outside Tenon’s capsule and
disturbing the orbital fat and particularly
allowing fat into the sub-Tenon’s space which
may result in adhesion syndromes.
If sutures are not tied tightly, marked
limitation of abduction may be present on the
first postoperative day. It is important to return
to surgery promptly following diagnosis, as
contraction and fibrosis may occur; however, in
our experience, patients present with lost
muscles even 20 years later.
Case example
A 28-year-old nurse presented as an adult
with a history of sudden onset of divergent
squint following surgery for convergent squint as
a child. The patient was still distressed at the
appearance and limited ability to adduct the eye.
The patient had had unsuccessful exploration to
retrieve the lost medial rectus followed by eight
subsequent surgeries on other ocular muscles
with an outcome she still regarded as
cosmetically unsatisfactory. With the advantage
of the operating microscope and good
illumination, exploration of the sub-Tenon’s
space revealed the medial rectus muscle on the
medial side of the left eye 2 mm from the optic
nerve. Although some gliosis and contracture
had occurred, it was still possible with the
microscope to recover the muscle and reattach it
10 mm from the limbus with a dramatic
improvement in ocular posture, although there
was an incomitance because of residual
contracture in the muscle.
Slipped muscles within the muscle sheath
Slippage of muscles within the muscle sheath
is difficult to recognise initially, as in the
immediate postoperative period the eyes may
look reasonably straight or slightly divergent. A
month or two later, for example in the case of
medial rectus recession, the divergence is worse,
and the muscle is underacting even more. Risk
of inferior rectus muscle slippage needs
emphasis because it may go unrecognised.
Reoperation may be misleading as careful
surgery may reveal the sheath of the muscle
appropriately attached to the sclera, and the
surgeon may be misled into thinking that he or
she is dealing with an attenuated muscle. It is
important to continue to explore the muscle and
the bunched up muscle further back in the
sheath must be grasped and reattached. Again
some incomitance of movement may be the
result of contracture if surgery is done late.
Restriction of upgaze after inferior oblique
muscle weakening surgery
This has been referred to as an adherence
syndrome. 15 The usual explanation is breaching
Tenon’s capsule with the disturbance of fat and
bleeding. Surgery is almost always required and
inferior rectus recession is effective. The forced
duction test may be positive. The complication is
avoided with careful separation of the inferior
oblique from Tenon’s capsule and being careful
to keep the muscle hook from tearing the capsule.
Hazards of inferior rectus recession
The objective of recession of the inferior
oblique muscle must include the patient’s ability
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