a-v pattern strabismus
DESCRIPTION
The presentation I have made and uploaded provides you with an in-depth insight into the patterns the strabismus may take following anomalies of extraocular muscles, deformities of the orbital structures,innnervational disturbances. The author does not assume responsibility or legal liability for any errors in the text or for the misuse or misapplication of material in this work. No copyright infringement, or plagiarism intended. Amrit PokharelTRANSCRIPT
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
Signs: Anomalous Head Posture
A eSotropia and V exotropia have fusion in the downward gaze
So usually have chin elevation
Clinical Features
Signs: Anomalous Head Posture
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
Urist MJ. The etiology of the so called A and V syndromes. Am J Ophthal 1951; 46:245-267
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
Investigation
Investigation
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
Treatment Surgical Treatment
Goals of treatment To eliminate abnormal head posture
To improve the cosmetic appearance of the patient
MANAGEMENT
Treatment Surgical 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 Surgical 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 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 syndromes. Am J Ophthal 1951; 46:245-267
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!!!