a-v pattern strabismus

A PATTERN STRABISMUS

V PATTERN STRABISMUS

Amrit Pokharel

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

This allows 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 differencebetween the primary position and downgaze. λ pattern: There is relative divergence on downgaze with no significant differencebetween the primary position and upgaze. ♦ pattern: There is relative convergence on both up- and downgaze.

‘A’ pattern

‘V’ pattern.

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

Rotational axes

Muscle Actions???

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:

Horizontal school If this 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:

Horizontal school It has 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:

Horizontal school

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.

This would 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:

Anatomical factors: 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:

Anatomical factors: 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:

Anatomical factors: For example 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:

Anatomical factors: 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:

Muscle Insertion: 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

Resulting in increased abduction of LR on elevation and increased adduction of MR on depression

AETIOLOGY:

Muscle Insertion: In A pattern, the LR insertions were higher

than normal and the MR insertions were lower than normal

Resulting in 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

With excyclotorsion, MR becomes a partial elevator whereas SR has a reduced elevating component

AETIOLOGY:

Sensory Deprivation:

Kusher also 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:

Costenbader

Breinin Magee Holland Maggi0

10

20

30

40

50

60

70

80

90

17.5 15

35

58.4

87.7

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

If the 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


A eSotropia and V exotropia have fusion in the downward gaze

So usually have chin elevation

Clinical Features


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

72.22

AmblyopiaNo Amblyopia

Clinical Features

Signs: Amblyopia

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

11

89

NRCARC

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)

Crouzon syndrome

PSEUDOPATTERNS…

Patients with accommodative eSotropia may have Pseudo- V pattern

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

Uncorrected hyperopia 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


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

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 the members of 1964 AAOO Panel

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 Grade 2- upto 30º angle with the horizontal line Grade 3- upto 60º angle with the horizontal line Grade 4- upto 90º 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

To assess 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

Investigation

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 correction: case report. Am J Ophthalmol 1970;69:133-134

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


Goals of treatment To eliminate abnormal head posture

To improve the cosmetic appearance of the patient

MANAGEMENT


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


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


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:


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

References:

Thank you!!!

a-v pattern strabismus

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