contribute to the management of children with squint and amblyopia including
school nurses, health visitors, general practitioners, community
physicians, orthoptists, optometrists and others in a variety of settings.
It is therefore desirable to have locally agreed arrangements for the referral,
assessment, treatment and monitoring of progress of children identified
with relevant eye conditions, to which all parties contribute and
which can be matched to national standards as these become established.
are intended to be general principles, rather than specific protocols,
regarding the best management of patients with a particular disorder. In
drawing up these guidelines we wish to inform ophthalmologists and allied
professionals as to the current view of best practice endorsed by the College.
This is to enable the development of locally based protocols for the care
of children with strabismus and amblyopia .
is assumed throughout this document that those professionals dealing with
common and uncommon cases of strabismus and amblyopia will have had adequate
training and experience to manage children with these conditions.
(syn.squint) and amblyopia are common conditions in childhood, with strabismus
affecting about 5% of five year olds of whom 60% have eso-deviations and
has an estimated prevalence in childhood of 1.2% to 4.4% depending on the
defining criteria. (2,3)
or amblyopia may lead to failure to develop binocular vision which may
prevent an individual pursuing certain occupations. The associated cosmetic
disorder may interfere with social and psychological development with potentially
serious effects for patients young and old.
amblyopia persisting in adulthood is a significant risk factor for blindness
in the case of an individual losing sight in the fellow eye.(4,5)
Timely diagnosis and appropriate treatment of children with strabismus
and/or amblyopia is likely to reduce the prevalence of persistent amblyopia
and ocular misalignment in adults.
strabismus and/or amblyopia may be the presenting symptom in children with
a serious eye disease or systemic condition (e.g. retinoblastoma or hydrocephalus)
when urgent referral to a specialist may be necessary.
Aims of management
aims may be achieved in a single consultation while some of the therapeutic
aims may need to be pursued through childhood to 'visual maturity' e.g.
by regular orthoptic assessment to the age of eight.
or restore optimal vision in both eyes
or restore normal binocular vision
serious ocular pathology or neurological disease
cosmetically satisfactory alignment of the eyes
significant abonromal (compensatory) head posture
use of the term 'cosmetic' in this context refers to the effect of improving
the alignment of the eyes from an abnormal to a normal position. If achieved,
this may provide both functional and psychological benefits. (6,7)
of vision, principally visual acuity, due to interruption of normal visual
development during the sensitive period in childhood.
Types of amblyopia
Stimulus Deprivation Amblyopia
deprivation amblyopia should be suspected in an infant or young child with
eye disease which interferes with the eye's ability to form a focused retinal
image. This may be a unilateral or a bilateral condition. Many eye
conditions, such as corneal ulcer, glaucoma, ocular trauma or eye surgery
in a young child may lead to stimulus deprivation and, if suspected, this
should be specifically excluded on examination.(8)
many cases of unilateral or asymmetrical 'organic' eye disease (e.g. retina
or optic nerve lesion or partial cataract) there is an additional visual
acuity deficit due to amblyopia which can only be ascertained retrospectively
following successful amblyopia treatment.(9)
amblyopia is suspected when a child shows either constant unilateral squint
(without alternation of fixation) or a fixation defect with one eye. This
may take the form of eccentric fixation, unsteady central fixation or fixation
which on cover test is not maintained on removing the cover from the fellow
amblyopia occurs when an interocular difference in spherical or cylindrical
refractive error exceeds certain limits. In spherical anisometropia a minimum
difference of 1.25 DS may be significant. (10,11,12)
high myopia may also cause amblyopia and bilateral amblyopia may result
from high degrees of uncorrected hypermetropia such as occur in aphakia.
Presentation and referral
amblyopia is detected by the use of suitable tests performed on children
who have presented with manifest squint (see below). Anisometropic amblyopia
is usually discovered when a child presents having failed a screening test
of visual acuity.
may be of mixed aetiology; e.g. children with anisometropic amblyopia may
present with strabismus and unilateral cataract may lead to secondary squint
in which case the amblyopia is likely to be severe.
minimum criterion for diagnosing amblyopia on a test of visual acuity is
accepted to be two lines difference between the eyes on the linear Snellen
test. This is usually equivalent to a difference of one octave in spatial
frequency resolution. On repeated testing it may be possible to detect
amblyopia in an eye with visual acuity of 6/9 when the fellow eye sees
6/6 (i.e. one line difference).
Methods of examination
children with squint, the observation of abnormal fixation behaviour (including
an aversion to monocular occlusion) is the basis for diagnosing amblyopia.
is often a difficult observation to confirm. The demonstration of a spontaneous
shift of fixation from one eye to the other (alternation) under normal
circumstances excludes amblyopia. In large angle esotropia with crossed
fixation, alternation may be found when the fixation target passes the
on cover test the suspected amblyopic eye holds central fixation steadily
through a blink after removing the cover from the fellow eye, significant
amblyopia is thus excluded. Examination of fixation using vertical prisms
is useful in diagnosing amblyopia in the absence of strabismus. (13,14)
Visual Acuity Measurement
children mature they are capable of more demanding tests of vision. This
has the unfortunate effect of corrupting the analysis of serial measurements.
As a result of the crowding phenomenon single optotype acuity tests underestimate
the depth of amblyopia to an unpredictable extent.(15,16) The
standard test is a linear optotype test (e.g.Snellen) with a normal degree
of crowding. Ideally, a log MAR chart provides a more uniform progression
of difficulty which is most suitable for comparative studies of visual
is necessary to detect significant visual acuity deficits and, in the case
of unilateral amblyopia, to measure interocular differences in acuity.
acuity should always be measured with the appropriate optical correction
in place. In general, one should use the most demanding test for the child's
ability. It may be helpful to test the better eye first (if this can be
ascertained) to encourage younger children to perform the test, while the
worse eye should be tested first in older children since some may memorise
the test letters.
of tests of visual acuity should be available and the most appropriate
test employed for a particular child (see appendix).
Management of amblyopia
is a treatable condition in childhood, i.e. during a 'sensitive' period
and the limits of this period are still being defined. Improvements in
acuity in strabismic amblyopia have been reported in children up to nine
years of age, but in most cases the age of eight is taken as the
onset of visual maturity(18).
is treated by preventing the use of the better eye and enforcing the use
of the amblyopic eye for substantial periods of time. Occlusion of the
normal eye with an adhesive patch is the mainstay of treatment in all forms
of unilateral amblyopia. In anisometropic amblyopia it may be required
if the vision fails to improve despite the provision of suitable optical
duration and intensity of occlusion therapy will depend upon factors such
case of stimulus deprivation in infancy appropriate treatment to prevent
amblyopia may consist of surgical and optical intervention e.g. removal
of cataract and fitting of a contact lens plus patching of the normal eye
for extended periods.
onset of amblyopia
of the acuity deficit
response to treatment
with prescribed treatment
most important prognostic factor is compliance with treatment. In smaller
prospective studies. when compliance is closely monitored. success rates
are high and significantly better with good compliance. In larger retrospective
studies success rates are lower except when selection criteria tend to
exclude poor compliance. (19,20,21)
therefore needs to be accurately assessed and optimised.
variety of protocols of occlusion has been described for use in various
situations and none is universally applicable. If one should be found ineffective
others may be tried. In the case of severe unilateral stimulus deprivation
amblyopia, the presence of nystagmus and/or secondary squint may indicate
a hopeless prognosis and intervention e.g. cataract may not be recommended,
depending on the known duration of the disorder.
an example of a treatment regimen, Scott advocates full-time occlusion
in the first instance for a period of one week per year of life (up to
a maximum of four weeks) before re-assessment. If no improvement has occurred
following three consecutive age-related periods of treatment, then 50%
occlusion of the preferred eye is prescribed. If improvement occurs to
parity on fixation assessment or visual acuity test then maintenance
occlusion of 50% daily wearing is instituted, with gradual reduction in
alternative approach, advocated by Watson et al is to use minimal occlusion
therapy of as little as 20 minutes per day combined with active use of
the amblyopic eye in a visually demanding game. We feel this method is
better suited to maintenance of acuity gained by more energetic treatment
and in the older cooperative child. (22)
successful method of treating amblyopia is penalisation of the non-amblyopic
eye using optical defocus. This may be achieved by the use of topical atropine
with or without defocusing lenses. Penalisation has advantages, which include
the relatively easy application and prolonged effect of atropine as compared
to occlusion and the possible benefit of maintaining low spatial
frequency stimulation of the penalised eye. On the other hand, the
impact of cycloplegia alone may be insufficient to cause a switch of fixation
to the amblyopic eye and atropine may cause toxic and allergic reactions.
amblyopia treatment causes a reversal of amblyopia to affect the occluded
eye while the amblyopic becomes the fixing eye with a good visual prognosis.
This is more likely to occur in younger children (< 2 years of age).
response to treatment of amblyopia is quicker in younger children. (27-29)
treatment may safely be discontinued when serial assessments exclude the
persistence of amblyopia, it is necessary to monitor children in this situation
up to the age of visual maturity and many will require 'maintenance' treatment
in the treatment of amblyopia is highly dependent upon compliance. As the
parent or guardian is usually the principal therapist, they will want to
know the proposed treatment, its duration and likely outcome. It is therefore
essential that the nature of amblyopia and its impact on the child's present
and future vision is fully explained. It is then necessary to outline and
agree a treatment plan with the parent(s). This is a joint responsibility
of the ophthalmologist and orthoptist who should collaborate closely in
advising and supervising treatment.
attempts at treatment of amblyopia achieve no improvement after substantial
efforts by all parties, it is then wise to agree to discontinue treatment
after full discussion with the parents. The potential benefits of treatment
must be considered in the context of the particular child and the family.
Refraction and spectacle prescription
6% of one year olds have a significant refractive error. (31)
Hypermetropia and anisometropia greatly increase the risk of developing
amblyopia and strabismus. (32,33) Accurate refraction and appropriate
prescription for ametropia are therefore essential in the management of
Cycloplegia and retinoscopy
refraction in children usually requires full cycloplegia. Adequate cycloplegia
for retinoscopy may be obtained 20 to 30 minutes following the instillation
of cyclopentolate 1% eye drops. This is better tolerated if a topical anaesthetic
such as proxymetacaine (0.5%) is also used. Below the age of three months
mydriatics are used in lower concentration to reduce the risk of toxicity.
routine use of atropine for diagnostic cycloplegia or mydriasis is unnecessary
and may cause harmful side-effects. However, in patients with darkly pigmented
irides cyclopentolate may prove insufficient for full cycloplegia and it
may be necessary to use atropine eye drops or ointment. This will achieve
cycloplegia after 90 minutes, and so may be suitable for use prior to an
is carried out in a semi-darkened room using hand-held lenses to neutralise
fundus reflections along the visual axis. It is important to maintain the
child's attention for fixation and it should not be necessary to use any
to cycloplegia it is useful to examine the pupils in cases of constant
unilateral squint and following mydriasis it is necessary to examine the
fundi with direct and indirect ophthalmoscopy in all cases to exclude pathology
(e.g. optic disc hypoplasia).
exercise should be repeated in the case of failed amblyopia therapy.
is rarely necessary to perform an examination under anaesthesia in order
to carry out refraction and fundus examination and its routine use should
be discouraged. If general anaesthesia is to be employed for another purpose,
then this may offer an opportunity to examine the eyes more fully.
refraction is the rule in children with amblyopia, squint or high refractive
errors especially when amblyopia persists despite apparently adequate treatment.
Correction of Refractive Errors
of refractive errors in children with squint and/or amblyopia requires
a team approach and is best carried out under the supervision of a consultant
ophthalmologist. The prescription of spectacles for children with uncomplicated
ametropia is the responsibility of ophthalmologists or optometrists in
practice, subject to local agreement.
spectacles should always be provided with plastic lenses to reduce the
risk of injury.
forms of esotropia, full correction of hypermetropia is the treatment of
choice. In practice, a reasonable lower limit for spectacle correction
is + 1.50 dioptres (+ 3.00 ret. @ 2/3 metre). When prescribing, 'full correction'
means that only the working distance is allowed for with no subtraction
children without strabismus the precise indication for treatment of spherical
errors is ill defined and will depend on the age of the child and the magnitude
of the error.
instance, in infants with hypermetropia, emmetropisation may occur naturally
and this should be monitored.
bilateral balanced hypermetropia, without strabismus, some refractive correction
is advisable for errors greater than about + 4.OOD even in the presence
of normal uncorrected visual acuity, since this may prevent asthenopia
when the demands of school increase.(34)
convergence excess esotropia bifocals may be considered. High-top executive
bifocals are prescribed aiming to fully correct the near deviation and
allow fusion with the least addition needed up to + 3.00 DS add. Bifocals
are not suitable if only partial reduction in the squint angle is obtained.
Once binocular fusion has become established on this treatment, gradual
weaning is carried out to avoid long-term dependence.
Anisometropia and astigmatism
and astigmatism are potent causes of amblyopia in childhood which may be
missed in younger children in the absence of squint. Hypermetropic anisometropia
appears more likely to cause amblyopia than anisomyopia.
need to correct the refractive error will depend on its magnitude and the
age of the child. For instance, anisometropia of greater than 4.00 D is
likely to need correction at any age, whereas correction of 1.50 to 2.00
D may only be desirable in children of school age. When amblyopia is found,
prescribe for spherical or cylindrical anisometropia of more than 1.00
D. If spectacles are prescribed for hypermetropia and/or correction of
squint, one may prescribe to correct any amount of anisometropia.
balanced (symmetrical) astigmatism without squint in children less than
four years old, serial refraction may reveal 'normal' emmetropisation with
time.(35) Spectacles are not usually required but the child
should be reviewed to confirm that the astigmatism is no longer significant.
(-6.00 D or more) may require correction in infancy and moderate myopia
(4.00 D or more) in two year olds and older children. Lesser degrees of
myopia do not usually cause problems in small children and prescription
can be based on subjective refraction over the age of six years.
Strabismus (Syn: squint)
is a misalignment of the eyes in which the visual axes deviate from bifoveal
of strabismus may be based on a number of features including the relative
position of the eyes, whether the deviation is latent or manifest, intermittent
or constant, concomitant or otherwise and according to the age of onset
and the relevance of any associated refractive error. The type of strabismus
is established by a detailed history and orthoptic examination.
broad categories of strabismus are distinguished by having various aetiologies
and usually differ in prognosis with and without treatment.
esotropia (syn: congenital or essential esotropia) is an idiopathic syndrome
in which an esodeviation is present before the age of six months. It is
variably associated with other clinical features including dissociated
vertical deviation, inferior oblique overaction, latent nystagmus, crossed
fixation, asymmetrical monocular optokinetic responses (OKN) and, usually,
no refractive error. (36)
strabismus includes fully and partially accommodative refractive esotropia,
convergence excess esotropia, cyclic esotropia, occlusion esotropia and
various forms of paretic squint.(31)
may also occur in congenital and acquired forms, both concomitant and incomitant.
strabismus includes dissociated deviations, cyclovertical muscle anomalies
and restrictive conditions (e.g. Brown's syndrome) as well as rarities
such as double elevator palsy.
Presentation and referral
deviation of the eyes is a quite common finding in healthy neonates and
should not cause undue concern. Normal binocular coordination becomes evident
at about three months and strabismus after this age is significant.
squint is generally recognised early by the family, health visitor or general
practitioner. A positive family history of squint or amblyopia should alert
those in primary care when carrying out routine checks or immunisations.
is often found in association with neurological disease such as in cerebral
palsy and in craniofacial developmental anomalies.
amblyopia and refractive error are much more common in children with treated
or regressed retinopathy of prematurity (ROP).(40) Premature
infants with a history of stage III ROP or worse should be followed up
after the neonatal period to screen for these complications.(41,42)
squint or amblyopia is suspected in the primary care setting, it is appropriate
for local protocols to provide for direct referral to an optometrist or
an orthoptist to exclude refractive error and strabismus. If no abnormality
is detected, such patients may be discharged. Cases with intermittent or
constant manifest squint should be referred to an ophthalmologist
without delay. In all children referred with strabismus or amblyopia the
possibility must be considered that this is the presenting feature of a
serious ophthalmic or systemic disease requiring urgent management.
are five broad considerations in planning management.
Development of binocular vision
with untreated infantile esotropia, when assessed at school age, will commonly
show equal visual acuity and a dense alternating suppression with no form
of demonstrable binocular cooperation. Early surgery is advocated on the
basis that the primary defect is a motor one and alignment of the eyes
before some critical age might permit the development of binocular function.(43)
This is the most controversial issue in the management of the condition
and has the greatest influence on the timing of any surgery. As yet,
there is not enough evidence to decide the matter and contrasting policies
are followed by different surgeons. To illustrate the variety of results
that have been obtained, three studies have been selected:
In a widely cited study that stimulated further work on early surgery,
93% of 106 children operated upon and successfully aligned before the age
of two years, had Worth 4-dot fusion or gross stereopsis. Of the children
aligned after this age, 31% demonstrated a similar outcome.(44)
to improve results, other studies have aimed for alignment by twelve or
even six months of age, but no better stereopsis has been achieved.(47)
In a series of 358 patients who had undergone surgery for infantile esotropia,
20% were orthotropic with fusional amplitudes and normal retinal correspondence.
None had stereopsis with TNO test and only three had low-grade stereopsis
on the Titmus test. The probability of achieving subnormal binocular vision
appeared to decrease with increasing age at surgery and was consistent
with the view that surgery before the age of two produces better results
but these may still be obtained in patients at a later age. (45)
In a recent prospective study of 98 out of 118 patients who underwent surgery
for infantile esotropia, and who had remained aligned to within 8 PD of
straight five years later, one third had stereopsis on the Titmus test
(range 200-3000 seconds of arc). Thus 22% of the original group had obtained
some form of binocular function and 68% had remained well aligned. No patient
with a divergent squint of any degree demonstrated stereopsis.(46)
most common outcome of successful surgery is the monofixation syndrome
with subnormal binocular vision. The surgical target in infantile esotropia
is, therefore, usually within 10 P1) of straight, this being the maximum
angle at which monofixation is possible.
advantages cited for various forms of subnormal binocular vision over complete
suppression are: simultaneous binocular perception, fusional vergence,
intact binocular field, normal distance judgement and, sometimes, gross
stereopsis. (48,49) An advantage to later surgery is a lower
risk of subsequent amblyopia.
an alternative to surgery, botulinum toxin injection into the medial recti
has been reported but is not at present in general use.(50)
Correction of amblyopia
many children with infantile esotropia demonstrate balanced alternating
fixation, amblyopia may occur. In untreated squint this is reported as
between 13% and 33%, rising to 20-80% after surgery. (51,52)
It is therefore important to monitor infants following squint surgery and
to treat any amblyopia detected.
that suitable orthoptic supervision is carried out, it is not necessary
to delay surgery until completion of amblyopia therapy.
General health issues
disorders which increase the risks of anaesthesia should be regarded as
a relative contraindication to early surgery. The angle and direction of
squint in infants with cerebral palsy and other neurological disorders
is often unstable. In such patients surgery for presumed infantile esotropia
may be better deferred at least until two years of age.(49)
However, in a prospective study of surgery for essential esotropia, the
outcome was no worse in the neurologically impaired or premature
of satisfactory cosmesis and the optimum age for surgery in a given case
are a matter for discussion between the parents, orthoptist and surgeon.
As regards the type of surgery, published evidence suggests that bi-medial
rectus recession is the most effective procedure, perhaps combined with
simultaneous resection of one lateral rectus for large angle squint. (54-56)
type and amount of surgery to perform for a particular squint is a decision
for the experienced surgeon. Parents need to be advised that, whilst accuracy
in measuring and operating upon strabismus is essential, the response to
surgery is variable and cannot be guaranteed. It is good practice to agree
the objectives and discuss the actions necessary if the desired surgical
outcome is not achieved.
Correction of associated features
of overacting inferior oblique muscles found in association with 'V' pattern
strabismus may be required on cosmetic grounds, including a compensatory
abnormal head posture and, if marked, is usually carried out at the same
time as the esotropia surgery. If binocular function is present after surgery,
persistent inferior oblique overaction may disrupt it.
summary, there is no series of cases reported in which successful alignment
in infantile esotropia has allowed the development of high grade stereopsis
associated with bi-foveal fixation (40 seconds of arc or better). If the
eyes are aligned to within 10 PD of orthotropia, up to one third of patients
develop subnormal binocular vision. There is evidence to suggest that this
binocular vision provides functional advantages. However, there are no
accurate means of predicting pre-operatively which patients will enjoy
Acquired strabismus in early childhood
the preceding recommendations in infantile strabismus management also apply
in acquired strabismus. The important differences are:
of these factors, treatment should aim to restore ocular alignment and
binocular vision as soon as possible. It is therefore necessary to consider
whether a given case of childhood strabismus has a chance of a good functional
result following therapy on the basis of the history, with particular regard,
e.g. to age, and findings such as the presence and severity of any associated
amblyopia and / or suppression. It may also be necessary to inform general
practitioners that delay in the referral of young children with strabismus
serves no useful purpose. Information regarding the mode (i.e. constant
or intermittent) and time of onset of a squint is helpful in assigning
appropriate urgency to appointments.
history of possibly normal binocular vision prior to the onset of squint.
likelihood that optical treatment alone will be required.
risk of loss of binocular vision if treatment for the squint is delayed.
important to measure and fully correct significant refractive error before
planning any surgical correction of strabismus. It is also desirable to
have corrected any amblyopia present.
Pre-operative prism adaptation in acquired strabismus
is good evidence to show an improved predictability and outcome of surgery
in acquired esotropia following adaptation using Fresnel prisms on spectacles.
Briefly, the method is used to discover patients with fusion potential
and may disclose a larger angle of squint than that first measured. Surgery
carried out on this larger angle has a greater chance of success without
an increased risk of over-correction and prism-responders so treated are
less likely to require re-operation. This technique is recommended where
practicable, particularly if measurements of squint angle are variable.(57)
may be constant or intermittent and may present as a primary condition
or be consecutive (following esotropia) or secondary to unilateral visual
primary exotropia is much less common in this country than esotropia. It
is thought to be more commonly associated with other developmental abnormalities.
The deviation is usually large with alternating fixation and a low risk
of amblyopia and the squint is present on near and distance fixation even
when accommodation is stimulated.
contrast, intermittent exotropia, which may begin in infancy, is noted
when one eye drifts outward at times, particularly in bright conditions,
on distance fixation and when the patient is tired or unwell. When the
deviation is manifest there may be suppression or diplopia, typically overcome
by closing one eye. Intermittent exotropia may be found to measure the
same angle at near and distance. More commonly, the eyes are straight at
near and divergent in distant and far distant fixation. In convergence
weakness, the angle is larger on near fixation. Children who have straight
eyes on near testing demonstrate good stereopsis (60 seconds of arc or
better) when old enough to perform detailed tests.
aims are generally the same as for esotropia, namely eradication of amblyopia,
restoration of fusion where possible and re-alignment where necessary to
achieve satisfactory function and appearance.
treatment is useful in improving control of residual intermittent exotropia
in children with good fusion who are old enough to learn how to be aware
of the deviation of one eye. Training is then aimed at improving fusional
Surgery in childhood exotropia
of optimal timing of surgery in intermittent exotropia is not settled.
It is appropriate to consider a variable plan according to the age of the
child. Indications for surgical intervention include increasing frequency
of manifest deviation with symptoms and deteriorating binocular function
as demonstrated by serial orthoptic assessment. (58-60)
types of horizontal muscle surgery are effective in treating childhood
exotropia. These include unilateral and bilateral lateral rectus (LR) recessions
and LR recess/ MR resect procedures.(61) In basic exotropia,
recess/resect surgery appears more effective, whereas in simulated distance
exotropia, bilateral lateral rectus recession has a higher success rate.
exotropia with convergence insufficiency, a lateral rectus recession and
relatively large ipselateral medial rectus strengthening procedure may
also reduce the difference between distant and near angle.(63)
young children, Pratt-Johnson recommends an amount of surgery to fully
correct the exotropic angle measured in distant fixation. A small esophoria
is the ideal immediate post-operative state. In children over the age of
three, the aim of surgery is to produce a small initial over-correction
of the deviation (up to 10 PD) measured in far distant fixation, this being
likely to lessen with time but to reduce the frequency of recurrence of
esotropia persisting after one week requires attention to prevent amblyopia
and suppression. Alternate occlusion may be used or prisms fitted to spectacles
to establish and maintain binocular fusion. Once this is achieved, further
surgery may be necessary to improve the ocular alignment and remove the
need for prisms.
A and 'V Patterns in Horizontal Deviations
exotropia increases on upward gaze, or an esotropia on downward gaze, a
'V' pattern is said to exist. Similarly, an 'A' or 'X' pattern may be found.
'V' pattern horizontal deviations are usually found in association with
overaction of the inferior oblique muscles. Assessment of these patterns
on prism/cover testing should be made with the child wearing full refractive
correction and on distance fixation with either elevation or depression
of the chin.
to weaken overacting inferior oblique muscles in significant 'V' pattern
deviations may improve abnormal head posture and expand the field of binocular
fusion. In patients with 'V' exotropia without fusion the same procedure
may improve alignment on downward gaze.
deviations may be due to overacting superior oblique muscles and may be
corrected by superior oblique weakening procedures. 'A' and 'V' patterns
may also be treated by vertical displacement of the insertions of the horizontal
recti if there is no evidence of oblique muscle dysfunction.
most common causes of vertical strabismus in childhood are superior oblique
underactions and dissociated vertical deviations.
oblique weakness may be due to paresis or to maldevelopment of the muscle
tendon. (65) Typically, a hypertropia in the affected eye will
be associated with a compensatory head tilt to the opposite side with chin
depression and overaction of the ipselateral inferior oblique. The head
posture develops as soon as the infant gains head control when upright.
It may not be noticed by the family and photographs are useful evidence.
There is usually evidence of fusion in the presence of the head posture
in primary gaze. Fusion is prevented if the hyperdeviation or cyclodeviation
aim of surgery is to allow normal binocular fusion in primary gaze and
on looking down without abnormal head posture.
to weaken an overacting inferior oblique muscle may be achieved by myectomy,
recession or disinsertion. Surgery to 'strengthen' the superior muscle
by tucking the tendon on the temporal side of the superior rectus is appropriate
if it is found to be lax and if it is normally inserted in the globe. Dissociated
vertical deviation (DVD) typically develops later on in children who have
previously undergone treatment for large angle infantile esotropia. Correction
of DVD may be required if a marked cosmetic defect is present. Suitable
surgical procedures include posterior fixation sutures or large recessions
of the superior rectus or in the case of co-existing inferior oblique overaction,
disinsertion and anterior transposition of this muscle.(66,67)
forms of surgery are usually the province of the strabismus specialist.
As with more common operations for squint, it is necessary to discuss the
rationale for a particular operation and the possible untoward effects
which may occur such as post-operative Brown's syndrome after shortening
of the superior oblique tendon or masked bilateral superior oblique weakness
following unilateral surgery. (68)
occasions, a child with acquired strabismus or amblyopia may be found to
have a primary neurological disorder such as optic glioma or medulloblastoma.
This is more likely in the presence of features such as nystagmus, persisting
amblyopia or deteriorating visual acuity. A careful examination should
be performed to exclude an afferent pupil defect, papilloedema, optic atrophy
or other cranial nerve disorder. The finding of any abnormal neurological
signs should prompt referral to a paediatrician and consideration of the
need for cranial imaging and electrophysiology.
facilities for children in hospital are defined in 'Ophthalmic Services
in a community clinic or in a hospital eye department there should be adequate
provision of space, time and equipment to allow the clinician to properly
examine the patient and provide any necessary treatment. Many factors influence
the ease with which assessment in hospitals and clinics is achieved. These
include comfortable surroundings in waiting and play areas for children
and their attendants, minimal delay in seeing the clinician and a friendly,
professional approach by staff to the parents and child.
optometrist and orthoptist should have easy access to the ophthalmologist,
ideally in adjacent accommodation or with the opportunity to jointly examine
the child (i.e. concurrent clinics where possible).
is important to be able to maintain the child's attention for examination,
especially if accurate retinoscopy is to be achieved. It is helpful to
have easy control of the lighting in the examination room to prevent
distraction and to have access to a variety of toys and pictures to attract
of children with strabismus involves a number of disciplines and may take
place in a variety of locations and adequate communication between staff
and patients and parents may be difficult to achieve.
between staff is essential in order to provide coherent advice to parents.
Clear and detailed medical and orthoptic records should be kept and be
mutually available when patients attend clinics and on admission for surgery.
Letters should generally be sent to general practitioners on all new cases
and whenever there is a change in the clinical condition or treatment of
a patient. It is good practice to copy correspondence to the community
paediatrician concerning children undergoing treatment for squint or amblyopia
when other conditions such as developmental delay coexist.
and patient (+family)
staff and orthoptists and optometrists in hospitals
orthoptists and medical officers
practitioners and health visitors
services (e.g. teachers, school nurses, non-hospital optometrists)
recommend the local provision of information sheets for parents explaining
the nature of the conditions concerned and their treatment and expected
outcomes in simple clear language. These should be available in out-patient
departments and wards.
aid communication in the treatment of amblyopia we recommend the development
of record books held by parents, in which the serial prescriptions of e.g.
occlusion therapy and a diary of treatment carried out and the visual acuity
achieved are recorded .
case discussions should be encouraged. Staff should be supported to attend
relevant academic meetings and maintain appraisal of the literature.
are many aspects of strabismus and amblyopia management which require audit
from time to time in order to be sure of the quality and efficacy of care
provided. Audit requires clear objectives and adequate resources in order
to be carried out successfully.
order to audit the results of treatment in strabismus, reference should
be made to the aims of treatment which are: i) Optimum visual acuity in
each eye ii) Optimum binocular function iii) Good cosmetic appearance
first two aims may be quantified on examination, while the third requires
questions to be asked of the patient and parents, although alignment of
the eyes to within 10 prism dioptres of straight is usually compatible
with an acceptable appearance and with peripheral fusion.
data to be assessed in audit are the following:
during and after amblyopia treatment
surgery i) target angle
ii) surgical dose
iii) technique iv) complications
of audit carried out locally should be compared to those published in relevant
literature. National audit initiatives, when deemed appropriate, might
be carried out under the auspices of the College.
PA. The epidemiology of strabismus. Br.J Ophthalmol, 1974; 58:224-231.
Simons E, Reinecke RD. Amblyopia screening and stereopsis. Symposium on
strabismus Eds. Helveston EM et al. Trans. New Orleans Acad. Ophthal. CV
Mosby St.Louis 1978: p. 15-50.
Thompson JR, Woodruff G, Hiscox FA, Strong N and Minshull C. The incidence
and prevalence of amblyopia detected in childhood. Public Health 1991;105:
Vereecken EP, Brabant P Prognosis for vision in amblyopia after loss of
the good eye. Arch.Ophthalmol. 1984; 102: 220-224.
Tommila V, Tarkkanen A. Incidence of loss of vision in the healthy eye
in amblyopia. Br.J.Ophthalmol. 1981; 65: 575-577.
Morris RJ, Scott WE, Dickey CE Fusion after surgical alignment of longstanding
strabismus in adults. Ophthalmology 1993; 100: 135-138.
Burke JP, Leach CM, Davis H. Psychosocial implications of strabismus surgery
in adults. J.Pediatr. Ophthal.Strab. 1997; 34:159-164.
Awaya S, Sugawara M, Miyake S. Observations in patients with occlusion
amblyopia. Trans. Ophthalmol. Soc. UK 1979; 99: 447-454.
Kushner Bj. Functional amblyopia associated with organic ocular disease.
Amj.Ophthalmol. 1981; 91: 39-45.
Ingrain RM. Refraction as a basis for screening children with squint and
amblyopia. Br.J.Ophthalmol. 1977; 61: 8-15.
Hardman Lea Sj, Loades J, Rubinstein MP. The sensitive period for anisornetropic
amblyopia. Eye 1989; 3: 783-790.
Kmschke Pj, Scott VvI, Keech RV. Anisometropic amblyopia. Ophthalmology
1991; 98: 258-263.
Zipf PE. Binocular fixation pattern. Arch. Ophthalmol. 1976; 94: 401-405.
KW, Walonker F, Edelman P. 10-diopter fixation test for amblyopia. Arch.Ophthalmol.
1981; 99: 1242-1246.
Hilton AF, StanleyJC. Pitfalls in testing children's vision by the Sheridan-
Gardiner single optotype method. Br.J. Ophthalmol. 1972; 56: 135-139.
Atkinson J, Pimm-Smith E, Evans C, Harding G, Braddick O. Visual crowding
in young children. Doc. Ophthalmol. Proc. 1986; 45: 201-203.
Ferris FL, Kassoff A, Bailey I. Visual acuity charts for clinical research.
Amj.Ophthalmol. 1982; 94: 91-96.
Scott WE, Dickey CE Stability of visual acuity in amblyopic patients after
visual maturity. Von Graefe's Arch. Clin Exp. Ophthalmol. 1988;226: 154-157
Levi DM, Carkeet A. Amblyopia: a consequence of abnormal visual development.
In Simons K (ed) Early visual development, normal and abnormal. Oxford
University Press, New York. 1993 pp 491-508.
Scott WE, Stratton V13, Fabre J. Full-time occlusion therapy for amblyopia.
Am. Orthopt. J. 1980; 30:125-130.
Hiscox F, Strong N, ThompsonjR, Minshull C, Woodruff G. Occlusion for amblyopia:
a comprehensive survey of outcome. Eye 1992; 6: 300-304.
Watson PG, Sanac AS, Picketing MS. A comparison of various methods of treatment
of amblyopia: a block study. Trans.Ophthalmol. Soc. UK 1985; 104:319-328.
von Noorden GK, Attiah F. Alternating penalization in the prevention of
amblyopia recurrence. Am. J. Ophthalmol. 1986; 102: 473-475.
Simons K Gotzler KC, Vitale S. Penalization versus part-time occlusion
and binocular outcome in treatment of strabismic amblyopia. Ophthalmology
1997; 104: 2156-2160.
Repka MY, Ray JM. The efficacy of optical and pharmacological penalization.
Ophthalmology 1993; 100: 769-774.
Foley-Nolan A, McCann A, O'Keefe M. Atropine penalisation versus occlusion
as the primary treatment for amblyopia. Br. J. Ophthalmol. 1997; 81: 54-57.
Fulton AB, Mayer DL. Esotropic children with amblyopia. Effects of patching
on acuity. Von Graefe's Arch. Clin. Exp.Ophthalmol, 1988; 226: 309-312.
Lithander J, Sjostrand J. Anisometropic and strabismic amblyopia in the
age group 2 years and above: a prospective study of the results of treatment.
Br. J. Ophthalmol. 1991; 75: 111-116.
Flynn JT, Cassady JC. Current trends in amblyopia therapy. Ophthalmology
1978 ; 85: 428-450.
Oster JG, Simon JW, Jenkins P When is it safe to stop patching? Br J.Ophthalmol.
1990; 74: 709-711.
1. Ingram RM, Walker C, Wilson JM, Arnold PE, Dally S. Prediction of amblyopia
and squint by means of refraction at one year. Br. J.Ophthalmol. 1986;
Ingrain RM, Barr A. Changes in refraction between the age of 1 and 3 years.
Br. J.Ophthalmol. 1979; 63: 339-342.
Phelps WL, Muir V. Anisometropia and strabismus. Am. Orthopt. J. 1977;
Spencer JB, Mets MB. Refractive abnormalities in childhood. Ophthal Clin.
N.Arner. 1990; 3: 265-279.
Sjostrand J, Abrahamsson M. Risk factors in amblyopia. Eye 1990; 4: 787-793.
Costenbader FD. Infantile esotropia.Trans Am. Ophthalmol. Soc. 1961; 59:
Pratt-Johnson JA, Tillson G. Management of strabismus and amblyopia. Thieme,
New York 1994; p. 91.
Hainline L, Riddell PM. Binocular alignment and vergence in early infancy.
Vision Research 1995; 35: 3229-3236.
Aurell E, Norrsell Y. A longitudinal study of children with a family history
of strabismus: factors determining the incidence of strabismus. Br. J Ophthalmol.
1990; 74: 589-594.
Kushner BJ. Strabismus and amblyopia associated with regressed retinopathy
of prematurity. Arch. Ophthalmol. 1982; 100: 256-261.
Page JM, Schneeweiss S, Whyte HEA, Harvey P Ocular sequelae in premature
infants. Pediatrics 1993; 92: 787-790.
Cryotherapy for Retinopathy of Prematurity Cooperative Group. The natural
ocular outcome of premature birth and retinopathy: status at one year.
Arch.Ophthalmol. 1994; 112: 903-912.
Chavasse FB. Worth's Squint. Bailliere, Tyndal & Cox, London 1939.
Ing MR. Early surgical alignment for congenital esotropia. Ophthalmology
1983; 90: 132-135.
von Noorden GY. A reassessment of infantile esotropia. XLIV Edward Jackson
memorial lecture. Am. J. Ophthalmol. 1988; 105: 1-10,
Kushner BJ, Fisher M. Is alignment within 8 prism diopters of orthotropia
a successful outcome for infantile esotropia surgery? Arch.Ophthalmol.
1996; 114: 176-180.
Helveston EM. Ultra-early surgery for infantile esotropia. In Strabismus
and ocular motility disorders. EC. Campos (ed) MacMillan 1990: 325-333.
Rogers GL, Chazan S, Fellows R, Tsou BH. Strabismus surgery and its effects
upon infant development in congenital esotropia. Ophthalmology 1982; 89:
Zak TA, Morin JD. Early surgery for infantile esotropia; results and influence
of age upon results. Can. J. Ophthalmol. 1982; 17: 213-218.
Scott AB, Magoon EH, McNeer KW, Stager DR. Botulinum treatment of childhood
strabismus. Ophthalmology 1990; 97: 1434-1438.
Good WV, da Sa LCF, Lyons CJ, Hoyt CS. Monocular visual outcome in untreated
early onset esotropia. Br.J.Ophthalmol. 1993; 77: 492-494.
Murray ADN, Calcutt C. The incidence of amblyopia in longstanding untreated
infantile esotropia. Eye 1998; 12: 167-172.
Charles SJ, Moore AT. Results of early surgery for infantile esotropia
in normal and neurologically impaired children. Eye 1992;
Kushner BJ, Morton GV A randomised comparison of surgical procedures for
infantile esotropia. Am. J. Ophthalmol. 1984; 98: 50-61.
Kushner BJ, Lucchese NJ, Morton GV. Should recessions of the medial recti
be graded from the limbus or the insertion?. Arch,Ophthalmol. 1989; 107:
Scott VVE, Reese PD, Hirsch CR, Flabetich CA. Surgery for large angle congenital
esotropia: two versus three and four horizontal muscles. Arch.Ophthamol.
1986; 104: 374-377.
Prism Adaptation Study Research Group. Efficacy of prism adaptation in
the surgical management of acquired esotropia. Arch.Ophthalmol. 1990; 108:
Keenan JM, Willshaw HE. The outcome of strabismus surgery in childhood
exotropia. Eye 1994; 8: 632-637.
Pratt-Johnson JA, Barlow JM, Tillson G. Early surgery in intermittent exotropia.
Am. J. Ophthalmol. 1977; 84: 689-694.
Hardesty HH, Boynton JR, Keenan PJ. Treatment of intermittent exotropia.
Arch.Ophthalmol. 1978; 96: 268-274.
Nelson LB, Bacal DA, Burke MJ. An alternative approach to the surgical
management of exotropia- the unilateral lateral rectos recession. J.Pecliatr.
Ophthalmol. Strabismus 1992; 29: 357-360.
Kushner BJ. Selective surgery for intermittent exotropia based on distance/
near differences. Arch.Ophthalmol. 1998; 116: 324-328.
Kraft SP, Levin AV Enzenauer RW. Unilateral surgery for exotropia with
convergence weakness. J.Pediatr.Ophthal. Strabismus 1995; 32: 183-187.
JA, Tillson G. Management of Strabismus and Amblyopia. A practical guide.
Thieme, New York 1994. P 141.
Helveston EM, Giangiacomo JG, Ellis F13. Congenital absence of the superior
oblique tendon. Trans. Arn. Ophthalmol. Soc.
Scott WE, Sutton VJ, Thalackerj. Superior rectus recessions for dissociated
vertical deviation. Ophthalmology 1982; 89: 317-322.
Burke JP, Scott WE, Kutschke PJ. Anterior transposition of the inferior
oblique muscle for dissociated vertical deviation. Ophthalmology 1993;
100: 245- 250.
Kraft SP, Scott WE. Masked bilateral superior oblique palsy. J. Pediatr.
Ophthal. Strabismus 1986; 23: 264-272.
Ophthalmic Services for Children, report of a joint working party. British
Paediatric Association and Royal College of Ophthalmologists 1994.
GK. Binocular Vision and Ocular Motility; theory and management of strabismus,
5th edition CVMosby Co. St.Louis 1996.
Practice Pattern: Amblyopia; American Academy of Ophthalmology, San Francisco
Practice Pattern: Esotropia; American Academy of Ophthalmology, San Francisco
J, Trimble R. Diagnosis and Management of Ocular Motility Disorders Blackwell,
MM, Wheeler MB. Concomitant esodeviations; in Tasman W, Jaeger EA (eds.)
Duane's Clinical OphthalmologyjB Lippincott Pa. 1989, vol. 1 Ch. 12.
work on these guidelines was carried out by an ad hoc committee:
Alec Ansons Royal Eye Hospital, Manchester.
Michael Clarke Royal Victoria Hospital, Newcastle Upon Tyne.
Robert Doran General Infirmary, Leeds. (Chairman)
Ian Strachan Royal Hallamshire Hospital, Sheffield.
Hoole General Infirmary, Leeds.
development was carried out by members of the Paediatric sub-committee
of the College :
Robert Doran (Editor)
Alistair Fielder (Chairman Scientific Committee)
Richard Markham. (Chairman)
the British Orthoptic Society Over sixty fellow consultants and orthoptist
colleagues contributed helpful information prior to final drafting.
of visual acuity
(PL) Gratings-based (Teller, Keeler)
Matching (Kay, Elliott)
letter (Sheridan-Gardiner, Sonksen-Silver)
Snellen and log MAR (Bailey-Lovie, Glasgow)
years and on
guidelines will require revision in the light of new information. Proposed
expiry date: December 2004.