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Case of the week 75 (
September 2012 )
Alternating Exotropia
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This 23 years old girl complains of this huge
outward eye deviation. She claims that the
condition started since only 6 years, family
photographs prove that she was fine till at
least the age of 15.
Vision : 6/6 OD
6/6 OS
Normal refraction , Normal fundus
She is about to marry and ask for surgical
correction for this ugly deviation.
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Post operative |
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Many patients with
alternating exotropia are
likely to have intermittent exotropia as a child
which became decompensated with age.
All of these patients have nearly equal vision
in both eyes, that is because
each eye is taking fixation half of the time.
Although stereo acuity is almost lost, those
patients have a very characteristic feature -you
have to put in mind-, people
with alternating exotropia can have an enlarged
peripheral field - which "shrinks" after the
eyes are straightened surgically - warn these
exotropic patients before surgery! Then reassure
them that they will stop noticing the reduction
in field in a few weeks.
Preoperative diplopia testing is extremely
important in the determination of what surgical
management should be done. It helps in deciding
if the patient should have surgery, what surgery
should be done, and when to do it. The
evaluation of postoperative diplopia also helps
in determining the course of action—e.g.,
whether to wait and reassure, manage medically
with prisms, or reoperate.
Intractable
diplopia after strabismus surgery in adults
without previous diplopia is very rare. The
diagnostic use of prisms prior to surgery may
identify some patients who have little or no
risk of postoperative diplopia, as well as a
group of patients with a small but definite risk
of intractable postoperative diplopia.
The prism adaptation test
is a pre-operative diagnostic test to identify
the potential for fusion and predict the risk of
diplopia in patients without the potential for
binocular single vision, before embarking on
cosmetic surgery.
In a patient like
this with huge XT ( 80 PD ), the surgical plan
is BLR recession 10mm combined with one MR
resection 7mm, this works good with me.
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