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356 Theory and Practice of Squint and Orthoptics
fusion. So DRS patients usually have normal
binocularity in a preferred fusing position by
means of compensatory head posture despite
the incomitance. The face turn is towards the
affected eye in eso Duane and away from
affected eye in exo Duane.
4. Diplopia is complained very infrequently
despite the fact that prevalence of deviation in
primary position is quite common. This may be
because of either face turn to achieve fusion or
occurrence of suppression.
5. Sensory adaptations. Patients who suppress
also develop abnormal retinal correspondence
and amblyopia.
IV. Associated ocular abnormalities
• Anisometropia with hyperopia is a frequent
association and may even be the cause of
amblyopia in some cases. Therefore, refraction
is very important especially in children.
However, more recent studies have shown that
anisometropia in Duane's syndrome is no higher
than the normal population.
• Other ocular abnormalities which have been
associated with Duane's syndrome include
optic nerve hypoplasia, morning glory
syndrome, congenital ptosis, nystagmoid
movements, congenital cataract, heterochromia
iridis, persistent hyaloid arteries, choroidal
coloboma, distichiasis, pupillary anomalies,
keratoconus, microphthalmos and many
others.
V. Associated systemic abnormalities
Some of the systemic abnormalities which have
been reported to be associated with Duane's
retraction syndrome are as follows: Klippel-Feil
syndrome, Goldenhar's syndrome, facial hemiatrophy, cervical spina bifida, umbilical hernia,
polydactyly, Chiari I malformations, sensorineural hearing deficits and Wildervanck
syndrome or cervico-oculo-acoustic syndrome
(combination of Duane's syndrome, sensorineural hearing loss and Klippel-Feil anomaly of
the spine).
Diagnosis
• Duane's retraction syndrome is usually
diagnosed on version tests by its typical
signs. Carefully look for anomalous vertical
movements also, as this is important in
determining the surgical strategy. There is a
curved outward rotation pattern uniquely
characteristics of Duane's which shows complete
absence of abduction (–4) in horizontal gaze,
while more outward rotation in upgazes and
downgazes due to anomalous innervation in
upgaze and downgaze.
• Adduction saccadic velocity can be reduced
in the affected eye in all types of Duane's
syndrome.
• Abduction saccadic velocity is reduced only
in type I and III.
• Measuring the eyelid fissure in abduction and
adduction to determine the degree of globe
retraction. This represents an indirect sign of
amount of anomalous innervation to LR muscle.
A greater degree of anomalous innervations
is correlated with an increased amount of globe
retraction.
• Force duction and force augmentation tests.
The two components responsible for abduction
limitation are: amount of normal innervation to
LR and degree of contracture of MR. These can
be differentiated by force duction test and force
augmentation test which compares the
voluntary abduction end point with possible
extension of this end point by forcing further
abduction manually with forceps. This proves
the paralysis of agonist and no contracture of
antagonist.
Force generation test also helps to determine the
active force generated by LR. Adduction
limitations which are usually seen in patients
with severe anomalous innervation to LR that
prevents the eye from moving into adduction.
This can be determine by force degeneration test
described by Romero Apis.
In this test, the patient is asked to look halfway
between the primary position and full adduction
and then, eye is moved further into adduction
while the patent is asked to further adduct the
eye. Resistance caused by co-contracting LR in
adduction can be appreciated at this point. Then
the patient is asked to abduct the eye and
grasping at temporal limbus, the examiner
attempts to adduct the eye. Then note that if
resistance has disappeared as now in abduction,
LR does not receive abnormal innervation.
Incomitant Strabismus
357
• Rarely, an acquired form of Duane's retraction
syndrome (Pseudo-Duane's syndrome) may
occur as a result of scarring following muscle
surgery or other surgery involving the
conjunctiva and Tenon's capsule and thus
need to be differentiated from true Duane's
syndrome.
Management
Non-surgical measures Refractive error and/
or amblyopia, when present, should be treated
first, on general lines (see page 202)
Surgical treatment
Indications goals include:
• Abnormal head posture,
• A significant deviation in the primary position,
• Marked globe retraction, or
• Marked upshoots and downshoots.
• Limitations of surgical treatment. In general,
disappointing results of surgery have been reported
for this condition. Therefore, better one should
not operate, when binocular single vision is
present in primary position of gaze or if it can
be maintained with a slight head turn.
• Further, no set rules exist for surgical treatment
of Duane's syndrome and that planning in each
case should be made individually taking into
consideration the coexisting horizontal and
vertical deviations.
• Rough guidelines, recommended, are described
briefly.
deviation) is indicated in cases with large
esotropia (>20 PD).
Advantage of asymmetric MR recession is that it
produces a fixation dures without fear of
adduction deficiency in the good eye. In addition
to correcting esotropia in primary position, it will
also decrease the likelihood of MR contracture
of the affected eye through the fixation dures of
the good eye which leads to a continuous
inhibition of the MR of the affected eye.
Management of associated globe retraction
LR recession of the affected eye along with asymmetric
MR recession may be helpful in cases of
esotropia with severe globe retraction, due to
anomalous LR.
Management to improve abduction
Superior rectus transposition (SRT) or vertical
rectus transposition (VRT) to the lateral rectus
is useful to achieve abduction force in cases
where there is no severe anomalous LR
recruitment and there is marked abduction
deficit (–3 to –4). These procedures help to
improve the abduction and also less MR
recession is required to correct the exotropia.
SRT has decreased risk of anterior segment
ischaemia, but may induce vertical incomitance.
Balanced partial VRT, is therefore, preferred over
SRT by many surgeons.
I. Management of Eso-DRS
Esotropia is classically more common in DRS
type I where LR innervation is normal in
abduction and anomalous in adduction.
Sometime esotropia may also occur in DRS type
II and type III. Depending upon the findings esoDRS can be managed as below.
Management of esotropia
1. MR recession of affected eye may be effective
in small angle esotropia (<20 PD) in primary
position in patients with mild DRS (cases with
minimum anomalous LR activity and normal LR
in adduction).
2.Asymmetric bilateral MR recession with
more recession of the fellow good eye (even up
to9 mm depending upon the amount of
Management of upshoots and downshoots
1. Faden operation (posterior fixation suture)
with or without recession of the lateral rectus
muscle 14 mm posterior to its insertion has
been advocated in patients with marked
upshoots or downshoots of mechanical type.
(Leash phenomenon).
2. Y-splitting of the lateral rectus muscle. In
case of upshoots and downshoots, Y-split with
LR recession of the affected eye can be done in
addition to treating esotropia. The LR is split
from its insertion as far posteriorly as possible,
spreading the muscle halves 10 mm up and
10 mm down (20 mm between them). This is also
followed by LR recession 5–10 mm to negate the
resection effect created by splitting the muscle
halves.
358 Theory and Practice of Squint and Orthoptics
II. Management of exo-DRS
Patients with exo-DRS, usually have anomalous
LR innervation in adduction and normal or
subnormal LR innervations in abduction. There
may be associated globe retraction and upwards
and downshoot. Depending upon the situation,
following measures used:
1. LR recession (supramaximal) of the affected
eye may be useful for correcting exotropia and
globe retraction.
2. Large recession of ipsilateral MR and LR's
required when exotropia is large. Contralateral
LR recession is needed to balance the effect of
the large medial rectus recession on the affected
side.
3. LR periosteal fixation (PF) has been reported
to be effective in correcting exotropia, and
anomalous head posture, and improving
adduction (as PF wards off the anomalous
activity of LR). Further, it can be combined with
partial VRT to improve abduction in patients
with subnormal LR innervation.
4. LR recession with Y-split is an option for
exotropia with upshoot and downshoot in cases
with normal LR activity.
III. Management of ortho-DRS
Ortho DRS is present in type III DRS, however,
may be present sometimes in cases of type I and
type II- DRS also. These patients are usually
orthotropic in primary position but there is
severe globe retraction with upshoots and
downshoots.
1. Symmetrical recession of MR and LR of the
affected eye with adjustable sutures on one
muscle and Y-split of LR is a good option in such
cases.
2. Posterior fixation suture on the LR of affected
side may reduce upshoots and down shoots.
Management of Y and lambda patterns in DRS
Such patients usually have:
• Less deficient abduction,
• Anomalous LR innervation only in vertical
gazes
• No globe retraction, and
• Adduction in the involved eye is worse in
upgaze.
1. Bilateral LR recession with elevation of
tendons in Y-pattern and downshift in lambda
pattern is the procedure of choice.
2. Bilateral SR recession in Y-pattern and
bilateral IR recession in lambda pattern can also
be considered.
HORIZONTAL GAZE PALSY WITH PROGRESSIVE
SCOLIOSIS
Etiology and genetics
Horizontal gaze palsy with progressive scoliosis
(HGPPS) is a rare autosomal recessive disorder
with the locus on chromosome 11 (11q 23–25).
The condition is thought to result from agenesis
of the abducens nucleus including both alpha
motar neurons and interneurons.
Clinical features
• Congenital horizontal gaze palsy with
progressive scoliosis (HGPPS), as the name
indicates, is characterized by complete
absence of conjugate horizontal gaze and
childhood onset progressive scoliosis.
• Vertical eye movements and convergence are
preserved.
• There are no associated ptosis and other
somatic abnormalities.
• Some patients may have nystagmus, esotropia,
and/or retraction on adduction.
MRI scan of brain in patients with HGPPS
shows hypoplasia of pons, absence of facial
colliculi, butterfly configuration of medulla and
deep midline pontine cleft (split pons sign).
II. CCDDs PRIMARILY AFFECTING VERTICAL
OCULAR MOTILITY
These disorders result from the developmental
anomalies of third and fourth cranial nerves or
their nuclei. These include:
• Congenital fibrosis of extraocular muscles
(CFEOMs), and
• Congenital ptosis.
CONGENITAL FIBROSIS OF EXTRAOCULAR MUSCLES
Congenital fibrosis of extraocular muscles
(CFEOMs) refers to a group of disorders that
result from primary dysinnervation of oculomotor
Incomitant Strabismus
359
and/or trochlear innervated extra-ocular
muscles. The genetic loci for the CFEOMs
phenotypes are known as FEOM. Till date, three
CFEOMs and four FEOM loci have been
defined.
CFEOM 1 phenotype
Genetics. It is an autosomal dominant disorder
with main locus FEOM 1, on chromosome 12.
Primary defect. In this condition is of superior
division of oculomotor nerve.
Clinical features include bilateral (Fig. 12.48A):
• Congenital ptosis,
• Globe infraducted in primary position
• Gaze restriction is noticed in upgaze as well as
horizontal gaze.
• Misdirected eye movements in the form of marked
synergistic convergence on attempted upgaze.
• Forced duction test is often positive in upgaze.
• Marcus Gunn jaw winking phenomenon is
noticed in 30–40% cases.
CFEOM 2 phenotype
Genetics. Autosomal recessive disorder with
main locus, FEOM 2, on chromosome 11.
Primary defect is in the development of both the
oculomotor and trochlear nuclei.
Clinical features (Fig. 12.48B).
• Ptosis is often severe
• Exotropia is usually of large angle
• Ocular movements, horizontal as well as
vertical are severely restricted.
CFEOM 3 phenotype
Genetics. Inheritance is autosomal dominant
with incomplete penetrance. The main locus is
the FEOM 3 on chromosome 16.
Primary defect in the development of
oculomotor nucleus is variable.
Clinical features are variable:
• Forced duction test is usually positive
• Misdirected eye movements or globe retraction
are rarely seen.
Differential diagnosis
CFEOMs should be differentiated from:
• Monocular elevation deficiency,
• Brown’s syndrome,
• Congenital progressive external ophthal-
moplegia (CPEO), and
• Duane’s retraction syndrome.
A
B
Fig. 12.48 Congenital fibrosis of extraocular muscles
(CFEOM): (A) Type I and (B) Type II
III. CCDDS PRIMARILY AFFECTING FACIAL
MUSCLES WITH ASSOCIATED OCULAR
MOTILITY DEFECTS
These disorders result from the abnormalities
in the development of the facial nerve and/or
nucleus. These include:
• Congenital facial weakness, and
• Möbius syndrome
MÖBIUS SYNDROME
The eponym Möbius syndrome refers to
congenital bilateral abducent paralysis
associated with congenital facial palsy with
variable other associations.
Etiology and genetics
Möbius syndrome is being considered a heterogeneous group of congenital disorders caused
360 Theory and Practice of Squint and Orthoptics
by developmental defects related to a variety of
insults such as ischaemia, toxic effects of
prenatal used drugs such as misoprostol,
benzodiazepines.
To date, two phenotypes with responsible
genotypes reported are:
• MBS 1 phenotype with the locus 13q12.2–13, and
• MBS 4 phenotype with the locus 1p22.
Clinical features (Fig. 12.49)
• Abduction is usually limited in both eyes.
• Gaze palsy may be there
• Deviation. Usually eyes are straight in primary
position, a few patients may have esotropia
• Facial weakness is characterised by:
– Mask-like facies with mouth constantly held
open.
– Eyelids cannot be closed completely.
Associations include:
• Paralysis or hypoplasia of tongue due to involve-
ment of hypoglossal nerve with speech and
swallowing difficulties are extremely common.
• Other cranial nerves which can be involved are
3rd, 4th, 9th, and 10th.
• Craniofacial anomalies which may be associated
are epicanthal folds, microstomia, micrognathia
and external ear defects.
• Limbs abnormalities include webbed fingers
and toes, supernumerary digits, club foot and
syndactyly.
• Deafness and mental retardation are also reported.
• Congenital heart defects such a ventricular septal
defect are also reported.
• Respiratory defects with tachypnoea and other
respiratory difficulties occur in some patients.
Management
• Prevention of exposure keratitis due to facial
weakness may be done by tarsorrhaphy.
• Esotropic patients, though rare, may be managed
by MR recessions with or without LR resection.
B. RESTRICTIVE STRABISMUS DUE TO
MECHANICAL RESTRICTIONS
Restrictive strabismus due to mechanical
restrictions may be caused by:
I. Tight extaocular muscles, as occurs in:
• Inelastic superior oblique in congenital
Brown’s syndrome
• Thyroid ophthalmopathy
• Entrapped inferior rectus muscle in blow-out
fracture of orbital floor.
• Monocular elevation deficiency (MED),
caused by fibrotic IR muscle.
• Strabismus fixus.
II. Structural adhesions, e.g. as seen in:
• Fat adherence to extraocular muscles or sclera
after strabismus surgery, retinal detachment
surgery or periocular trauma
• Congenital fibrotic bands
• Acquired Brown’s syndrome due to scarring/
inflammation around, the trochlea
• Conjunctival and Tenon’s capsule scarring
III. Orbital mass lesions, e.g.
• Orbital tumours causing mass effect on the
globe movements.
• Glaucoma explant with large bleb causing
mass effect.
Note. A few of the conditions are described
here.
Fig. 12.49 A child with möbius syndrome (Courtesy: Dr.
Kalpana and Dr. Sandra).
TIGHT EXTRAOCULAR MUSCLES
BROWN'S SYNDROME
Brown syndrome refers to mechanical
restriction (a significant limitation) of elevation
in adduction caused by an overly taut superior
oblique tendon of the same eye. On version
testing, the condition mimics an inferior oblique
palsy except that a V-pattern is present in
contrast to A-pattern associated with inferior
oblique palsy.
Incomitant Strabismus
361
Etiology
The condition may be congenital or acquired.
Originally, Brown divided the syndrome into
true sheath syndrome (now congenital) and
simulated sheath syndrome (now acquired).
1. Congenital Brown's syndrome is presently
thought to be caused by a congenitally taut
superior oblique tendon (short and inelastic
tendon). Originally, Brown thought that these
cases occur due to congenitally shortened anterior
sheath of the superior oblique tendon; the theory
which has not been proved by subsequent
workers. In fact, Parks observed that the superior
oblique tendon sheath does not exist at all and
that the term 'superior oblique tendon sheath
syndrome' introduced by Brown is a misnomer.
2. Acquired Brown's syndrome is presently
thought to be caused by an acquired taut
superior oblique tendon, secondary to following
conditions:
• Tenosynovitis of the superior oblique
trochlear apparatus.
• Trauma to the trochlear region in any form
may cause this abnormality. The 'canine
tooth syndrome' of Knapp also falls into this
category. Surgical trauma has emerged
as another cause of acquired Brown's
syndrome (traumatic Brown's syndrome).
• Rheumatoid nodules on the superior oblique
tendon posterior to the trochlea. Association
with other autoimmune diseases like SLE,
Sjögren syndrome and Graves' ophthalmopathy is also reported.
• Retrotrochlear thickening of the tendon or
anomalies of the trochlea itself may lead to
impaired slippage of the tendon through the
trochlea.
• Idiopathic
Main consistent clinical features include the
following (Fig. 12.50):
1. Elevation is limited significantly, characteris-
tically in adduction and present in abduction.
There may or may not be mild limitation of
elevation in midline. Degree of limitation is
same on versions and ductions.
2. Overaction of superior oblique is characteris-
tically absent which normally would be found
with a paretic inferior oblique muscle.
3. Divergence in upgaze producing a V-pattern.
4. Forced duction test is positive on attempts to
elevate the adducted eye; but is negative on
attempts to elevate the abducted eye.
Less important and variable clinical features
include:
1. Downshoot in adduction.
2. Widening of the palpebral fissure on adduction.
3. Straight eyes in primary position are present
in most patients but a few may have
hypotropia.
4. Compensatory head posture (chin up) may be
present in patients with hypotropia.
Clinical features
Congenital cases (also known as true or primary
syndrome) are constant and unilateral in 90%
percent of patients. Most acquired cases are
intermittent and more likely to improve
spontaneously. The syndrome is rarely seen in
adults. The clinical features of this syndrome can
be divided into main consistent features and less
important variable features.
Fig. 12.50 Brown's syndrome right eye: (A) Note limitation
of elevation in right eye which is marked in adducted
position (B) (Courtesy: Dr Kalpana and Dr Sandra).
362 Theory and Practice of Squint and Orthoptics
5. An audible click may be produced when such
patients are able to elevate their adducted
eye. Some observers have even used the term
'superior oblique click syndrome' for such
patients.
6. Inflammatory signs like superonasal orbital
pain, and tenderness may be present in
acquired cases.
Bilateral Brown's syndrome, when present,
exhibits 'V' pattern exotropia. Rest features being
similar to unilateral cases.
Grading of Brown's syndrome
Eutis et al have graded Brown's syndrome into
mild, moderate and severe (Table 12.11).
Table 12.11 Grading of Brown's syndrome (Eutis et al)
Grade Restriction of Downshoot Hypotropia
elevation in in adduction in primary
adduction position
1–Mild + – –
2–Moderate + + –
3–Severe + + +
Brown plus syndrome, is the term used by
Jampolsky for the cases having vertical deviation
in the primary position or in adduction, with or
without compensatory head posture.
Differential diagnosis
1. Inferior oblique paralysis versus Brown's
syndrome
• Limitation to elevation in adduction is greater on
testing for ductions than versions in inferior
oblique paralysis, while in Brown's syndrome,
it is equal.
• Overaction of the superior oblique muscle is
typically absent in Brown's syndrome, while
it is present in inferior oblique palsy.
• Forced duction test is positive in Brown's
syndrome, while it is negative in inferior
oblique palsy.
• Park's 3-step test is positive in inferior oblique
palsy.
2. Other conditions with restriction of elevation
which need to be differentiated from the Brown's
syndrome are double elevator palsy, fracture of
the orbital floor, Graves' ophthalmopathy and
congenital fibrosis of the inferior rectus muscle.
In all these conditions, elevation is equally
restricted in adduction, primary gaze and in
abduction; while in Brown's syndrome,
elevation is restricted only in adduction.
Management
1. Conservative treatment. Acquired cases
should be observed, since spontaneous
improvement has been reported. These cases
depending upon the situation may need:
• Range of eye motility exercises (elevation and
adduction exercises).
• Steroids either orally or by injection near the
trochlea in inflammatory cases.
• Correction of the underlying cause, when possible
such as trauma to the trochlea.
2. Surgical treatment. Results of the surgery for
this entity are controversial and, therefore,
surgery should only be undertaken in severe (grade
3) cases of Brown's syndrome, i.e. in the presence
of:
• A significant cosmetically disfigurement head
tilt; or
• Severe and constant congenital Brown
syndrome that threatens binocularly and
development of amblyopia
• A large hypotropia, in primary position or
• Unacceptable downshoot in adduction.
Surgical procedures recommended are as
follows:
1. Superior oblique tenotomy. It is a simple, safe
and effective procedure in treating Brown's
syndrome. However, about 50% cases develop
symptoms of superior oblique paralysis which
can be managed by recession of either ipsilateral
inferior oblique or contralateral inferior rectus.
2. Superior oblique tenectomy. To avoid the risk
of superior oblique palsy, Parks recommends
performing a 6 mm superior oblique tenectomy
within the intermuscular septum along the nasal
border of superior rectus.
3.Superior oblique weakening with a silicone
expander has also been advocated by Wright in
1991 to prevent superior oblique palsy following
tenotomy. This procedure involves expanding
the length of the tendon using a silicone spacer
usually silicone retinal 240 band. The weakening
Incomitant Strabismus
363
effect is graded by varying the length of the
silicone that bridges the gap between the cut
ends of the tendon. In a Brown syndrome
6–7 mm expander is recommended. A chicken
suture can be placed in lieu of an expander to
retain the cut-ends of superior oblique tendon
together. However, this procedure is difficult
and cumbersome. Such a procedure may
actually be more relevant in cases with superior
oblique overaction (Brown plus).
4. Other superior oblique weakening or lengthening
procedures such as:
• Chicken suture in nasal half of tendon or
• Loop suture at the insertion may also be tried.
THYROID OPHTHALMOPATHY
This term is coined to denote typical ocular
changes which include lid retraction, lid lag, and
proptosis. These changes have also been labelled
as: Endocrine exophthalmos, malignant
exophthalmos, dysthyroid ophthalmopathy and
ocular Graves' disease (OGD).
Etiopathogenesis
It may be a part of Graves' disease (the syndrome
consisting of hyperthyroidism, goitre and eye
signs) or may be associated with hypothyroidism or even euthyroidism. Thus, a direct
causative connection between the thyroid
dysfunction and the ocular changes remains
elusive. There is an increasing evidence to
suggest that Graves' ophthalmopathy has an
autoimmune etiology. Most data presently
support the postulate that an autoantigen is
coexpressed in the thyroid gland and orbital
fibroblast. This antigen is recognised by the
circulating T cell lymphocytes. Activating the T
cells (CD4 cell) triggering an immune response.
The activated T cells secrete various cytokines,
interferon, interleukin L-alpha and tumour
necrosis factor (TNF), which cause proliferation
of fibroblasts in the orbit and production of
glycosaminoglycans (GAGs).
Presence of mucopolysaccharides, predominantly hyaluronic acid, together with
interstitial oedema and inflammatory cells
accounts for the proptosis, and swelling of
extraocular muscles.
Clinical features
1. Lid signs. These are: (i) retraction of the upper
lids producing the characteristic staring and
frightened appearance (Dalrymple's sign),
(ii) Lid lag (von Graefe's sign), i.e. when globe is
moved downwards, the upper lid lags behind,
(iii) fullness of eyelids due to puffy oedematous
swelling (Enroth's sign), (iv) difficulty in
eversion of upper lid (Gifford's sign), (v)
infrequent blinking (Stellwag's sign).
2. Conjunctival signs. These include deep
injection and chemosis.
3. Pupillary signs. These are of less importance
and may be evident as inequality of dilatation
of pupils.
4. Ocular motility defects. These range from
convergence weakness (Mobius's sign) to partial
or complete immobility of one or all of the
extrinsic ocular muscles. Severe restrictive
myopathy occurs due to lymphocytic infiltration
of the extraocular muscles and varying amounts
of oedema, inflammation and fibrosis.
• The most common ocular mobility defect is a
unilateral elevator palsy, Fig. 12.51 caused by
involvement of the inferior rectus muscle
followed by failure of abduction due to
involvement of medial rectus muscle.
• Thus, thyroid (endocrine) myopathy is a
common cause of acquired vertical deviation in
adults, especially females. It is a rare cause of
acquired vertical deviation in children.
5. Exophthalmos. It is a common and classical
sign of the disease. As a rule, both eyes are
affected; but it is frequent to find one eye being
more prominent than the other. Even unilateral
proptosis is not uncommon. In majority of cases,
it is self-limiting.
6. Exposure keratitis and symptoms of ocular
surface discomfort. These include sandy or gritty
sensation, lacrimation and photophobia. Corneal
exposure has been attributed to upper lid
retraction, exophthalmos, lagophthalmos, inability
to elevate the eyes and a decreased blink rate.
7. Optic neuropathy. It occurs due to direct
compression of the nerve or its blood supply by
the enlarged rectus muscles at the orbital apex.
It may manifest as papilloedema or optic
atrophy with associated slowly progressive
impairment of vision.
364 Theory and Practice of Squint and Orthoptics
Fig. 12.51 A patient with Graves' ophthalmopathy depicting limitation of left superior rectus muscle due to involvement
of left inferior rectus muscle.
American Thyroid Association (ATA)
classification
ATA has classified Graves' ophthalmopathy,
irrespective of the hormonal status into following
classes characterised by the acronym 'NOSPECS'
Class 0 : No signs and symptoms.
Class 1 : Only signs, no symptoms (signs are
limited to lid retraction, with or
without lid lag and mild proptosis).
Class 2 : Soft tissue involvement with signs
(as described in class-1) and symptoms
including lacrimation, photophobia,
lid or conjunctival swelling).
Class 3 : Proptosis is well established.
Class 4 : Extraocular muscle involvement
(limitation of movement and diplopia).
Class 5 : Corneal involvement (exposure
keratitis).
Class 6 : Sight loss due to optic nerve involve-
ment with disc pallor or papilloedema
and visual field defects.
For practical purposes, it has been described
as 'early' (which include ATA class 1 and 2) and
'Late Graves' ophthalmopathy' (class 3 to 6).
Investigations
1. Thyroid function tests. These should include:
serum T3, T4, TSH and estimation of radioactive
iodine uptake.
2. Positional tonometry. An increase in intraocular
pressure in upgaze helps in diagnosis of
subclinical cases.
3. Ultrasonography. It can detect changes in
extraocular muscles even in class 0 and class 1
cases and thus helps in early diagnosis. In
addition to the increase in muscle thickness,
erosion of temporal wall of orbit, accentuation
of retrobulbar fat and perineural inflammation
of optic nerve can also be demonstrated in some
early cases.
4. Computerised tomographic scanning. It may
show proptosis, muscle thickness, thickening of
optic nerve and anterior prolapse of the orbital
septum (due to excessive orbital fat and/or
muscle swelling).
Management of Graves' ophthalmopathy
It is in addition to and independent of the
therapy for the associated thyroid dysfunction;
as the later usually does not alter the course or
ophthalmic features. The treatment modalities
employed are as follows:
1. Topical artificial tear drops in the day time
and ointment at bedtime are useful for relief of
foreign body sensation and other symptoms of
ocular surface drying.
2. Guanethidine 5% eyedrops may decrease the
lid retraction caused by overaction of Muller's
muscle.
Incomitant Strabismus
365
3. Systemic steroids may be indicated in acutely
inflamed orbit with rapidly progressive
chemosis and proptosis with or without optic
neuropathy.
4. Immunosuppressive drugs may be required
to control acute inflammation when steroids are
not effective or contraindicated.
5. Radiotherapy (2000 rads given over 10 days
period). It may help in reducing orbital oedema
in patients where steroids are contraindicated.
6. Lateral tarsorrhaphy should be performed
in patients with exposure keratopathy (with
mild to moderate proptosis) not responding to
topical artificial tears.
7. Prismatic glasses may help to relieve the mild
diplopia in primary position or rending gaze.
But since the deviation is usually very
incomitant, prism often does not alleviate the
diplopia in all positions of gaze.
8. Surgical orbital decompression: It should be
performed, only when systemic steroids and
radiotherapy have proved ineffective in patients
with marked proptosis associated with severe
exposure keratopathy and/or optic neuropathy
with imminent danger of permanent visual
loss.
The most commonly employed technique is
'two wall decompression' in which part of the
orbital floor and medial wall are removed.
9. Extraocular muscle surgery. It should be
carried out for left out diplopia in primary gaze,
after the congestive phase of disease is over
and the angle of deviation is constant for the
last 6 months.
Recession of the affected muscle (inferior rectus,
medial rectus or superior rectus as the case may
be) is the primary surgical treatment. Strengthening procedure should be avoided. Extraocular
muscle surgery may eliminate diplopia in
primary gaze but rarely restores normal motility
because of the restrictive myopathy that typifies
Graves' ophthalmopathy.
Adjustable suture surgery may help optimize the
alignment and rotations in these difficult cases.
Since late overcorrection frequently occurs,
especially with large inferior rectus recessions,
slight undercorrection (fusion with a slight chinup position) is desirable at the time of surgery.
10. Cosmetic surgery for persistent lid
retraction. It consists of levator and Muller's
muscle recession. Recently, implantation of
scleral grafts has become a popular technique.
11. Blepharoplasty. It may be performed by
removal of excess fatty tissue and redundant
skin from around the eyelids.
ORBITAL BLOW-OUT FRACTURE
These are isolated communited fractures which
occur, when the orbital walls are pressed
indirectly. Blow-out fractures mainly involve
orbital floor and medial wall.
Etiology
These generally result from trauma to the orbit
by a relatively large, often rounded objects, such
as tennis ball, cricket ball, human fist (Fig. 12.52)
or part of an automobile. The force of the blow
causes a backward displacement of the eye and
an increase in intraorbital pressure with a
resultant fracture of the weakest point of the
orbital wall, usually this point is the orbital floor,
but this may be the medial wall also.
Classification
1. Pure blow-out fractures. These are not
associated with involvement of the orbital rim.
2. Impure blow-out fractures. These are associated
with other fractures about the middle third
of the facial skeleton.
Clinical features
• Periorbital oedema and blood extravasation in and
around the orbit (e.g. subconjunctival
ecchymosis) are initial lesions. This may mask
certain signs and symptoms seen later.
Fig. 12.52 Mechanism of blow-out fracture of the orbital
floor.