PATTERNS OF STRABISMUS

Patterns of Strabismus
A Pattern
V Pattern

 A Pattern
 Relative convergence on up gaze and
relative divergence on down gaze

 Minimum of 10-pd dioptres difference
b/w upgaze and down gaze

 V Pattern
 Relative divergence on up gaze and
relative convergence on down gaze

 Minimum of 15-pd dioptres difference
b/w upgaze and down gaze

 Thisallows for a slight physiological V
pattern

Variants of A and V patterns include:
X pattern: There is relative divergence on both
up- and downgaze.
Y pattern: There is relative divergence on upgaze
with no significant difference
between the primary position and downgaze.
λ pattern: There is relative divergence on
downgaze with no significant difference
between the primary position and upgaze.
♦ pattern: There is relative convergence on both
up- and downgaze.

why necessary???
 Common entity

 Countless surgical overcorrections and
undercorrections have been made due to
failure to recognise patterns

History…

 The alteration in the degree of convergence
and divergence on gaze change ---
Duane(1897)

History…
 Lancaster(1944) recommended measuring
deviation in upgaze and downgaze

 Scobee(1947) emphasized using versions to
detect oblique muscle OA

History…
 Albert suggested A pattern and V pattern

 Costenbader(1958) fully described and
designated A and V patterns

 Knapp recommended surgery on dysfunctional
oblique muscles for A and V patterns

Must-know points…
 Anatomy of EOMs
 Only
when there is integrity of a sensorimotor
apparatus is there a BSV

 Any anomaly---no normal BSV

 Origin of EOMs

Must-know points…
 Anatomical pecularities of IO
 Only EOM that does not originate from the orbital
apex

 Short tendon of less than 2 mm

 The tendon-insertion lies within 2 mm of macula

 Run shortest course

 Only muscle to come in contact with other two
muscles:IR and LR

AETIOLOGY:
 A great deal has been advanced as regards
the role of
 Horizontal,
vertical and oblique muscle
dysfunctions

 Facial characteristics

 Abnormal muscle insertions

AETIOLOGY:
 But no unanimity concerning pathophysiology
has been gained

 Several schools of thought have evolved and
some of them which are into acceptance are
presented here

AETIOLOGY:
 Horizontal school
V pattern esotropia: OA of MR on downgaze
OA of LR on upgaze

V pattern exotropia: OA of LR on upgaze
OA of MR on downgaze

A pattern exotropia: UA of MR on downgaze

 A pattern esotropia: UA of LR on upgaze

AETIOLOGY:
 Ifthis were the case then in case of bilateral
abducens paralysis, there would be invariably a
case of A pattern esotropia

 The pattern is only occasionally observed and this
contradicts the mechanism championed by Urist

AETIOLOGY:
 Ithas been found that there occurs an elevation
or depression upon adduction

 And this is a common feature in A and V pattern

 Villascea shared a view that although some
vertical elements could be present, the pattern
strabismus could be treated with the horizontal
surgery only

AETIOLOGY:

 Also in EMG studies in V exotropia it was found
that there occurred a cocontraction of both
horizontal muscles of the fixating eye and
abnormal LR activity of the deviating eye.

 Thiswould not suffice to be a real aetiological
factor

AETIOLOGY:
 Vertical school
 Brown championed opinion that A or V pattern
may be caused by primary anomalies in vertical
muscles which have adductive function in tertiary
action

AETIOLOGY:
 Vertical school
A syndrome: with eyes looking up and elevators
contracting, the increased adduction of eyes
could be caused by OA ing SR and by UA ing IOs
and with eyes looking down and the depressors
contracting the increased abduction could be due
to OA ing SOs and UA ing IR

AETIOLOGY:
 Vertical school
V syndrome: the increased abduction of eyes
when looking up would be due to OA ing IOs and
the UA ing SR and the increased adduction in
downgaze would be due to OA of IR and UA of
SOs.

AETIOLOGY:
 Oblique school
A syndrome: OA of SOs

V Syndrome: OA of IOs

AETIOLOGY:
 Oblique school
A syndrome: OA of SOs
 Overaction may be primary or secondary to
UA(paresis) of IOs.
 SO is abductor and its abducting factor will be most
noticeable in depression
 There occurs relative divergence of eyes producing A
pattern

AETIOLOGY:
 Oblique school
V syndrome: OA of IOs
 Overaction may be primary or secondary to
UA(paresis) of SOs.
 IO is abductor and its abducting factor will be most
noticeable in elevation
 There occurs relative divergence of eyes producing V
pattern

AETIOLOGY:
 Anatomical factors:
 Urrets-Zavalia reported association of A esotropia
(with UA ing IOs) and V exotropia (with OA ing
IOs) in patients with mongoloid features

 Mongoloid features:
 Hyperplasia of malar bones
 Upward slanting of palpebral fissures
 Straight lower lid margin

 Mongoloid
feature

Eg A
eSotropia

AETIOLOGY:
 Urrets-Zavalia reported association of V esotropia
(with OA ing IOs) and A exotropia (with UA ing
IOs) in patients with antimongoloid features

 Antimongoloid features:
 Hypoplasia of malar bones
 Downward slanting of palpebral fissures
 S-shaped contour of lid margin

 Antimongoloid
feature

V eSotropia

 Projection of the positions of the extraocular muscles onto a horizontal
plane. Dimensions, to scale, are from measurements in rectilinear three-
dimensional coordinates (see Table 2, Ruete's figures). The oblique
muscles have nearly the same plane of action. (Modified from Hering E:
The Theory of Binocular Vision. New York, Plenum Press, 1977.)

AETIOLOGY:
 Normally the direction of the IOs and the reflected
portion of the tendon of SO are || to each other in relation
to the Y axis.

 Sagitallisation or desagittalisation of oblique muscles due
to variations in origin and/or insertion of muscles can
result in pattern strabismus

AETIOLOGY:
 Forexample plagiocephaly increases the angle
b/w the reflected part of the SO and the plane of
the IO

 Thus decreasing depressing action of the SO and
resulting in OA of IO

AETIOLOGY:
 Coats reported the association of V pattern
strabismus in 10 out of 14 cases of craniofacial
synostosis

 Paysse observed strabismus in 59% of patients
with Spina bifida and 47% of strabismic patients
had A pattern strabismus

AETIOLOGY:
 Muscle Insertion:
 Many have reported anomalies in the insertions of
horizontal recti muscles; thus, if the muscles
insertions are higher or lower than normal,
adduction or abduction is subsequently increased
in upgaze or downgaze

AETIOLOGY:
 Raised insertion of MR has been found in pxs
with elevation on adduction

 In
V pattern, the MR insertions were higher than
normal and the LR insertions were lower than
normal

 Resultingin increased abduction of LR on elevation
and increased adduction of MR on depression

AETIOLOGY:
 In
A pattern, the LR insertions were higher than
normal and the MR insertions were lower than
normal

 Resultingin increased adduction of MR on elevation
and increased abduction of LR on depression

AETIOLOGY:
 Sensory Deprivation:
 Guyton and Weingarten hypothesized that poor
binocular function may result in pattern
strabismus.

 Deficient fusion is a/w excyclotorsion of globe

 Withexcyclotorsion, MR becomes a partial
elevator whereas SR has a reduced elevating
component

AETIOLOGY:
 Sensory Deprivation:

 Kusheralso discussed the effect that torsion of
globe has on horizontal function in upgaze and
downgaze

Prevalence:
 Co-existence of A or V pattern with horizontal
strabismus is seen in
 12.5% to 50% of cases

Urist MJ. The etiology of the so called A and V
syndromes. Am J Ophthal 1951; 46:245-267

Prevalence:

100 87.7
80 58.4
60 35
40 17.5 15
20
0

Prevalence:
 According to 1964 American Academy of
Ophthalmology:
V eSo> A eSo> V eXo> A eXo

 However, a somewhat different distribution
was reported by von Noorden and Oslon:
V eXo> A eXo> V eSo> A eSo

Clinical Features
 Symptoms:
 Age at presentation
 58% of patients had age of onset at 12 months or
younger out of 421 patients, as reported by
Costenbader

 Ifthe pattern is small in magnitude it may not be
recognised until the early school when head posture
becomes apparent or reading difficulties are noted.

Clinical Features
 Symptoms:
 Asthenopia and Diplopia
 A eXotropia and V eSotropia

Clinical Features
 Signs:
 Anomalous Head Posture

 11% of patients with alphabet patterns

Kushner BJ. Ocular causes of abnormal head
posture. Ophthalmology 1979; 86:2115

Clinical Features
 Signs:

 A eSotropia
and V exotropia have fusion in the
downward gaze
 So usually have chin elevation

Clinical Features
 Signs:

V eSotropia and A exotropia have fusion in the upward
gaze
 So usually have chin depression

Clinical Features
 Signs:
 Amblyopia

 Same as found in other forms of strabismus

 However,a dissertation titled “CLINICAL
EVALUATION AND MANAGEMENT OF A OR V
PATTERN TROPIAS IN SQUINT” prepared at the
Minto Ophthalmic Hospital, Bangalore Medical College
& Research Institute, Bangalore maintained:

Clinical Features

27.7

Amblyopia
No Amblyopia

72.22

Clinical Features
 Signs:
 Amblyopia

 Ciancia
found abnormal retinal correspondence in
89% of cases of A or V pattern

Patients at high risk
 Craniofacial anomalies like
craniosynostosis, spina bifida

 Antimongoloid lid fissures (A eXotropia and V
eSotropia)

 Mongoloid lid fissures (A eSotropia and V
eXotropia)

 Infantile esotropia (V eSotropia)

PSEUDOPATTERNS…
 Patients with accommodative eSotropia may
have
 Pseudo- V pattern

 This is particularly apparent if the patient is
examined without hypermetropic correction as
with

 Uncorrectedhyperopia there is a tendency to
accommodate in the primary gaze and
downgaze, thus simulating a V pattern

Diagnosis
 Measure patient‟s alignment in 25º upgaze
and 25ºdowngaze with the patient fixating an
accommodative target at distance, with fusion
prevented

Urist MJ. The etiology of the so called A and V

Diagnosis
 Measure patient‟s alignment in 25º upgaze
and 35ºdowngaze with the patient fixating an
accommodative target at 33 cm.

Noorden, G. K. von, and Oslon, C.L.:
Diagnosis and surgical management of
vertically incomitant horizontal strabismus
, Am. J. Ophthalmol. 60:434, 1964

Diagnosis

 Full refractive correction should be worn and
accommodation should be well controlled to
prevent the appearance of pseudo V pattern

Diagnosis
 The position of sursumversion and
deosursumversion may be achieved
 By
moving the fusion target upwards or
downwards, or

 By
moving the patient‟s head downwards or
upwards

Stella found no difference in the measurements
under both conditions. This view is supported by

Diagnosis
 Grading of Inferior oblique muscle overaction
 Inferior oblique overaction is graded by observing
the angle the adducting eye makes with the
horizontal line as it elevates and abducts on
lateral version to the opposite side

 Grade 1- upto 15º angle with the horizontal line

Diagnosis
 Grading of Inferior oblique muscle overaction
 For practical purposes, oblique overaction is
graded as

 Mild-
if hyperdeviation is present in sursumduction
 Moderate- if hyperdeviation is present adduction
 Severe-if hyperdeviation is present in primary position

Investigation
 Aims
 To detect and measure A/V patterns

 To assess ocular movements a/w A/V patterns

 Toassess significance of A/V patterns for
prognosis and management

Investigation
 Criteria for diagnosis
 V pattern: minimum difference of 15 pd from
upgaze to downgaze
 A pattern: minimum difference of 10 pd from
upgaze to downgaze
(Knapp 1959)

There is a physiological tendency to relatively diverge
in upgaze, and thus the minimum standards required
for a V pattern is larger than that for an A pattern

MANAGEMENT
 Pre Treatment Evaluation
 Detailed History
 Assessment of BCVA
 Cycloplegic Refraction and correction

 Measurement of angle of deviation in all the 9
positions of gaze for near and far, with and
without optical correction

 Uniocular and binocular motility with particular
attention to the oblique muscle dysfunction

MANAGEMENT
 Pre Treatment Evaluation
 Bielschowsky head tilt test to r/o associated
fourth nerve palsy

 Tests like Bagolini glasses, Worth‟s 4 dot test

 Anterior segment evaluation

 Posterior segment evaluation

MANAGEMENT
 Treatment
 Nonsurgical Treatment
 Use of oblique prisms: Conjugate and oblique
prisms may be tried in patients with:

 Diplopia

 Small deviations

 Patients not fit for surgery

MANAGEMENT
 Treatment
 Nonsurgical Treatment
 Use of oblique prisms: Conjugate and oblique
prisms may be tried in patients with:

Diamond reported good results with bilateral
conjugate and oblique prisms in V eSotropia
and diplopia
The use of prisms resulted in the reorientation of
the motility field

Diamond S. V-Esotropia aided by conjugate oblique prism

MANAGEMENT
 Treatment
 Treatment of Amblyopia

 Conventional occlusion therapy to improve
fixation and VA in the amblyopic eye

 Occlusion therapy is effective till 12 years of
age but few authors have seen improvement till
19 years of age so a trial of occlusion therapy is
given to all patients till 18-19 years of age.

MANAGEMENT
 Treatment
 Treatment of Amblyopia

 Inverse occlusion in patients with EF to supress
the non- foveal primary directionalisation and to
encourage central fixation

 After the central fixation in the affected eye is
restored the occlusion is changed over to the
fixing eye and treatment is continued.

MANAGEMENT
 Treatment
 Surgical Treatment
 Goals of treatment
 To correct the horizontal and vertical alignment in
useful positions of gaze
 To eliminate motor obstacles to maintain and regain
binocular single vision

MANAGEMENT
 Treatment
 Goals of treatment
 To eliminate abnormal head posture

 To improve the cosmetic appearance of the patient

MANAGEMENT
 Treatment
 Indications and timing of surgery
 Difference of angle of deviation in upgaze and in
down gaze of > 15 pd

 Squint interfering with the development of BSV

 Patients with AHPs

MANAGEMENT
 Treatment
 Indications and timing of surgery
 Refractive error and amblyopia treated

 Surgery before 8 yr usually results in the attainment
of good fusion

 But after 8 yr there may be post operative
vertical, horizontal, torsional diplopia

MANAGEMENT
 Treatment
 Surgical options…

MANAGEMENT
Terminologies
 Recession: the tendon of the muscle is
severed from the globe at its insertion and
reattached to the sclera
 Marginal Tenotomy: the muscle is weakened
by means of a series of marginal incisions at
right angles to the plane of the muscle

MANAGEMENT

Terminologies
 Simple Tenotomy: the tendon of the muscle is
severed from the globe at its insertion and not
reattached by sutures
 Resection: the severed tendon of the muscle is
severd from the gobe and reattached further
forward on to the sclera

MANAGEMENT
Terminologies
 Tucking or tenoplication: the muscle and/or its
tendon is folded upon itself and the folds firmly
stitched together so as to produce a shortening
effect
 Myectomy: the muscle is cut near its origin, or
near its insertion

References:

 von Noorden GK, Chapter 3 „Summary of the
Gross Anatomy of the Extraocular Muscles‟ in
“Theory and Management of Strabismus” 5th
ed, The C.V.Mosby Company, 1996:41-52

 Fiona J. Rowe, Chapter 11 „A and V patterns‟
in “Clinical ORTHOPTICS” 3ed ed, WILEY-
BLACKWELL, 2012

References:
 Urist MJ. The etiology of the so called A and V

 von Noorden GK, Chapter 17 „A and V patterns‟
in “Theory and Management of Strabismus” 5th
ed, The C.V.Mosby Company, 1996:41-52

References:
 Pradeep Sharma. Chapter 6 „Examination Of A
Case Of Squint‟ in “Strabismus Simplified”, 3rd
reprint, 2004

 von Noorden GK, Chapter 4 „Physiology of the
Ocular Movements‟ in “Theory and
Management of Strabismus” 5th ed, The
C.V.Mosby Company, 1996:41-52

PATTERNS OF STRABISMUS

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