Transcript exodeviations

exodeviations
An exodeviation is a divergent
strabismus that can be latent or
manifest.
etiology
 The exact etiology of most exodeviation
is unknown, proposed causes include:
 Anatomical and mechanical factors
within the orbit.
 Innervational abnormalities such as
excessive tonic divergence.
Pseudoexotropia
 An appearance of exodeviation when in
fact the eyes are properly aligned.
 Wide interpupillary distance.
 Positive angle kappa without other
ocular abnormalities.
 Positive angle kappa together with
ocular abnormalities such as temporal
dragging of the macula in ROP.
exophoria
 Is an exodeviation controlled by fusion.
 An exophoria is detected when binocular
vision is interrupted, as during an
alternate cover test.
 Exophoria is usually asymptomatic.
 Prolonged, detailed visual work or
reading may bring about asthenopia.
 Treatment is usually not necessary
unless an axophoria progresses to an
INT XT.
Intermittent exotropia
 With the possible exception of exophoria
at near, the most common type of
exodeviation is intermittent exotropia.
Clinical characteristics
 The onset is an early, before age 5.
 The deviation often becomes manifest during
times of visual inattention, fatigue, or stress.
 Parents report that the exotropia occurs late in
the day with fatigue or during illness,
daydreaming, or drowsiness upon awakening.
 Exposure to bright light often causes a reflex
closure of 1 eye.
 During the early stages, the deviation is
usually larger for distance than for near.
 Later, the near and distance
exodeviations tend to be more equal in
magnitude.
 Intermittent exotropias can be
associated with small hypertropias, A or
V patterns, and oblique muscle
dysfunction.
 In many patients, untreated intermittent
exotropia progresses toward constant
exotropia.
 Children younger than 10 years of age may
initially have diplopia but often develop the
cortical adaptations of suppression and ARC.
 However, NRC and good binocular function
remain when the eyes are straight.
 Amblyopia is uncommon unless the exotropia
progresses to constant at an early age.
Clinical evaluation
 History of the age of onset of the
strabismus.
 The clinician records how often and
under what circumstances the deviation
is manifest.
 A qualitative measurement of the control
of the deviation, is an important
component of the evaluation.
 Good control: exotropia manifests only after
cover testing, and the patient resumes fusion
rapidly without blinking or refixating.
 Fair control: exotropia manifests after fusion is
disrupted by cover testing, and the patient
resumes fusion only after blinking or refixating.
 Poor control: exotropia manifests
spontaneously and may remain manifest for an
extended time.
 The deviation at near fixation is often less than
the deviation at distance fixation.
 The difference may be due to either a high
AC/A ratio or to tenacious proximal fusion.
 Tenacious proximal fusion is a proximal
vergence aftereffect that occurs in some
patients with intermittent XT.
 This aftereffect is due to a slow-to-dissipate
fusion mechanism that prevents intermittent
exotropia from manifesting at near fixation.
 For patients with significantly more
exodeviation in the distance than at
near, 1 hour of monocular occlusion,
eliminates the effects of tenacious
proximal fusion and may help to
distinguish between a truly high AC/A
and a pseudo high AC/A.
 A patient with a pseudo high AC/A ratio
would have equal distance and near
measurement after occlusion.
Classification
 Basic type.
 Divergence excess type.
 Convergence insufficiency type.
Basic type
 Is present when the exodeviation is
approximately the same at distance and
near fixation.
Divergence excess
 Consist of an exodeviation that is greater
at distance fixation than at near.
 It can be divided into 2 subtypes.
 1-true divergence excess.
 2-simulated divergence excess.
True divergence excess
 Refers to those deviations that remain
greater at distance than at near even
after a period of monocular occlusion.
 Some of these patients prove to have a
high Ac/A ratio when tested at near with
+3 D lenses.
Simulated divergence excess
 Refers to a deviation that is initially
greater at distance than at near but that
becomes about the same after 1 eye is
occluded for 1 hour ( to remove the
effect of tenacious proximal fusion).
The convergence insufficiency
 Is present when the exodeviation is
greater at near than at distance.
 This type excludes isolated convergence
insufficiency.
 Sensory testing usually reveals excellent
stereopsis and NRC when the
exodeviation is latent.
 And suppression with ARC when the
deviation is manifest.
 However, if the deviation manifests
rarely, diplopia may persist during those
manifestations.
Treatment
 Some ophthalmologists prefer to delay
surgery in young children.
 Other ophthalmologists worry that
delaying surgery could allow for
development of permanent suppression
and loss of long-term stability following
surgical correction.
Nonsurgical management
 Corrective lenses for any significant
refractive error.
 Mild to moderate hyperopia are not
routinly corrected.
 Hyperopia of more than 4.00 D and
astigmatism of more than 1.50 D is
better to be corrected.
 Correction of even mild myopia may help
to control the deviation.
 Additional minus lens power to stimulate
accomodative convergence may help to
control the deviation.
 Part-time patching of the dominant eye
4-6 hours per day, can be an effective
treatment for small-to moderate-sized
deviations. persumably due to disruption
of suppression.
Active orthoptic treatments
 Antisuppression therapy, diplopia
awareness and fusional convergence
training, can be used alone or in
combination with patching, minus lenses,
and surgery.
 This type of treatment can be effective
for deviations of 20 P or less, but is not
recommended for poorly controlled
deviations.
Surgical treatment
 Many patients with intermittent exotropia
ultimately require surgery,
 The best sensory outcomes are probably
achieved with motor alignment before
age 7 or before 5 years of strabismus
duration, or while the deviation is still
intermittent.
 Many surgeons use manifestation of the
deviation more than 50% of the time as
criterion for surgery.
 Symmetric recession of both LR is the
most common surgical procedure.
 R&R procedure is an acceptable
alternative and may be preferred in basic
type INT XT.
 Unilateral LR recession may be
performed in small-angle exodeviations.
Management of surgical
overcorrection
 A temporary overcorrection of up to 10-
15 P is desirable after bilateral LR
recession.
 Persistent overcorrection may require
treatment with base-in prisms or
alternate patching to prevent amblyopia
or diplopia.
 Corrective lenses or miotics should be
considered if hyperopia is significant.
 Bifocals can be used for a high AC/A
 Unless in a case of slipped or lost
muscle, a delay of several months is
recommended before reoperation
because spontaneous improvement is
common.
 Bilateral MR muscle recession, R&R of
the fellow eye.
 Botulinum toxin injection into 1 MR
muscle may be effective.
Management of surgical
undercorrection
 Mild to moderate residual XT is only
observed alone if fusional control is
good.
 Aggressive base-in prism management
with a gradual weaning of the prism
dosage.
 Postoperative patching and orthoptic
treatment can be useful.
 Botulinum toxin injection into LRM.
Indication for reoperation
 If the nonsurgical management failed.
 The type of surgery is related to the type
of previous surgery.
 The surgical dose-response curve
appears to be similar to that for the initial
surgery.
Constant exotropia
 Congenital exotropia.
 Sensory exotropia.
 Consecutive exotropia.
Congenital exotropia
 Presents before age 6 months.
 Large angle constant deviation.
 Most of these patients have associated
neurologic problems or craniofacial
disorders.
 Early surgery can lead to gross SBV.
 DVD and IO overaction may be seen in
these patients.
Sensory exotropia
 Any condition that reduces visual acuity
in 1 eye can cause sensory exotropia.
 Anisometropia, corneal and lens
opacities, optic atrophy or hypoplasia,
macular lesions, and amblyopia.
 Both sensory ET and XT are common in
children, but exotropia predominates in
older children and adults.
 Loss of fusional abilities, known as
central fusional disruption, or horror
fusionis, can lead to constant and
permanent diplopia when adult-onset
sensory exotropia has been present for
several years prior to visual rehabilitation
and realignment.
 In these patients, intractable diplopia
may persist, even with well aligned eye.
Consecutive exotropia
 An exotropia that follows previous
surgery for esotropia.
 Treatment of consecutive exotropia
depends on many factors, including the
size of the deviation, the type and
amount of previous surgery, the
presence of duction limitation, lateral
incomitance, and the level of visual
acuity in each eye.
Exotropic Duane retraction
syndrome
 Duane syndrome can present with
exotropia, usually accompanied by a
face turn away from the affected eye.
 Adduction is most often markedly
deficient.
 Other signs include eyelid narrowing,
glob retraction, and upshoot and
downshoot.
Dissociated horizontal
deviation
 DVD may contain vertical, horizontal, and
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torsional components.
DHD is when the dissociated abduction is
predominate.
It may be confused with a constant or
intermittent exotropia.
DVD and latent nystagmus often coexist with
DHD.
Treatment consists of unilateral or bilateral LR
recess in addition to any necessary oblique or
vertical muscle surgery.
Convergence insufficiency
 Characteristics are:
 Asthenopia, blurred near vision, reading
problems.
 Poor near fusional convergence
amplitude
 Remote near point of convergence.
 The patient, typically an older child or
adult
 May have an exophoria at near.
 Rarely accomodative spasm may occur
in an effort to overcome the convergence
insufficiency.
Treatment
 Orthoptic exercises.
 Base-out prisms can be used to
stimulate fusional convergence.
 Stereogram, pencil pushups and other
near point exercises are often used.
 If these exercises fail, base-in prism
reading glasses may be needed.
 Unilateral or bilateral MR resection may
be used in rare cases but may be
associated with risk of diplopia in
distance viewing.
 Patients with combined convergence
and accomodative insufficiency may
benefit from plus lenses and base-in
prisms for reading.
Convergence paralysis
 Is usually secondary to an intracranial lesion.
 Is characterized by normal adduction and
accomodation with exotropia and diplopia on
attempted near fixation only.
 It differs from convergence insufficiency in its
relatively acute onset and the patient,s inability
to overcome any base-out prism.
 It usually results from a lesion in the corpora
quadrigemina or the nucleus of the cranial
nerve 3 and may be associated with Parinaud
syndrome.
Treatment
 Is limited to providing base-in prism at
near to alleviate diplopia.
 When accomodation is also weakened,
plus lenses also may be needed.
 If SBV can not be restored at near by
any way, occlusion of one eye is
indicated during reading.
 Eye muscle surgery is contraindicated.