A general summary of AV Pattern strabismus outlining the various types of AV patterns and their treatment and management/

1. PRESENTS..
Alphabetic pattern Strabismus
‘A’ pattern ‘V’ Pattern

2. DEDICATED TO...
• Dr. Burton J. Kushner, MD.
• Your interest in this subject of Binocular vision & Strabismus is what has kept me interested and enjoying doing what I
do...
A. J. Hamilton

3. HISTORY OF AV PATTERN
STRABISMUS
• Originally described as “an abnormal variation in the angle of horizontal strabismus in
vertical gaze” by Alexander Duane in 1897.
• Later labelled as “Horizontal strabismus with associated vertical elements” from 1896-1956.
• First official series of papers with emphasis on the measurement of horizontal deviation in
vertical gaze was penned by Uretts-Zavalia in 1948, in his papers “Abducción en la elevación”
and “Paralisis bilateral congenita del musculo oblicuo inferior”. Attention was also made to
the point that overaction and subsequently underaction of the oblique muscles were in fact
associated with increased and decreased convergence or divergence.
• By the late 1950’s, the syndrome was officially given the title of ‘A’ or ‘V’ Pattern strabismus,
by Dr. D. G. Albert and F. D. Costenbader in 1955 and 1957 respectively, owing to both ‘A’ and
‘V’ patterns being the most commonly noticed forms. The name was then shortened to ‘A-V
Pattern Strabismus’ as it stands today.
• The syndrome as a whole falls under the Strabismus sub-group of ‘Complex strabismus’ or
‘comitant horizontal/vertical deviations in Strabismus’

4. INCIDENCE OF AV PATTERN STRABISMUS
• 15-25% of cases of pediatric strabismus occur with A/V Pattern Strabismus as a subsidiary symptom
associated with most common forms of Strabismus: Brown’s Syndrome, Duane’s retraction Syndrome, or
any association with any form of over/underaction of the Superior/Inferior obliques
• A/V Pattern Strabismus is the most common form of Infantile Strabismus.
• While ‘A’ Pattern is perhaps the most common, ‘V’ Pattern in either esotropia or exotropia is quite
prevalent in both pediatric and adult strabismus categories.
• Other rarer forms such as ‘X’ pattern, Lambda pattern, and ‘Y’ pattern strabismus have also been
documented and seen; Lambda pattern being a sub-group of ‘A’ pattern, while ‘Y’ pattern is more closely
associated with ‘V’ pattern. ‘X’ pattern to date remains a group of its own, since so little is still unknown
of this sub-type.
• These special forms of incomitance in vertical gaze consist of nothing more than modifications of the
classic A or V patterns; therefore,they should not be regarded as separate entities.

5. COMMON FORMS OF AV PATTERN
STRABISMUS

6. ‘A’ PATTERN STRABISMUS
‘A’ PATTERN ESOTROPIA
• An A pattern is present when a horizontal deviation shows a more convergent (less divergent)
alignment in upgaze compared with downgaze.
• An ‘A’ pattern is considered significant if the difference between upgaze and downgaze is ≥10 Δ.
• Patients with ‘A’ pattern esotropia will show on clinical presentation:
• An increase of the esotropia in midline upgazes, and a decrease of the esotropia on
midline downgazes
• The eyes will be mostly straight in Primary gaze and direct downgaze
• Patients will adopt a chin-up head posture to compensate for single binocular vision.
• An ‘A’ Pattern is often associated with:
• Primary superior oblique overaction
• Inferior oblique underaction/palsy with subsequent superior oblique overaction.
• Inferior rectus underaction

7. ‘A’ PATTERN ESOTROPIA
This 6-year-old girl presents
with a evident ‘A’ pattern
Esotropia associated with a
right superior oblique
overaction, visible as an
overshoot of the right eye on
adduction. Noticeable is the
child’s assumed chin-up head
tilt to the left to compensate
for single binocular vision in
primary gaze. Also evident is
the convergence of the eyes
on direct upgaze, hence an ‘A’
pattern.

8. ‘A’ PATTERN STRABISMUS
‘A’ PATTERN EXOTROPIA
• In cases of an ‘A’ pattern exotropia, the deviation of the eyes is more pronounced as the
eyes move more towards midline downgaze rather than midline upgaze.
• There is an evident divergence of the eyes in direct downgaze, with the eyes ‘splaying
outwards’.
• Like in ‘A’ pattern esotropia, a patient’s eyes in primary and upgaze will often look
straight, and work together closely to normal. ‘A’ pattern exotropia is much more
prevalent in midline downgazes, rather than upgaze. This misalignment is often not
noticed by parent’s whose children have this form of strabismus.
• Similar again to an ‘A’ pattern esotropia, patients will often assume an abnormal head
posture, except that it will be a chin-down, head turn, again allowing the patient to
achieve single binocular vision in primary gaze.

9. Mongoloid feature
- On upgaze, the eyes
converge inward
-In Primary position
eyes are slightly
exotropic
- On downgaze, the
eyes diverge outward
“A” PATTERN EXOTROPIA:

10. ‘A’ PATTERN EXOTROPIA
This 20-year-old girl shows
a visible ‘A’ pattern
exotropia associated with
overaction of her right
superior oblique, most
evident in down and left,
and down and right gazes.
In primary gaze she adopts
a chin-down head turn
away from the affected
eye, in order for both her
eyes to fuse in single
binocular gaze. In direct
downgaze there is a visible
‘outward splaying’ of both
eyes. The exotropic
deviation is minimal to
normal in all upgazes.

11. ‘V’ PATTERN STRABISMUS
‘V’ PATTERN ESOTROPIA
• First described by Alexander Duane in 1897 when he described a patient with
bilateral superior oblique palsy
• Patients with a ‘V’ pattern esotropia, as similar to ‘A’ pattern, will show a definite
increase of horizontal deviation more so in downgaze, with a corresponding decrease
of the deviation in upgaze.
• The inferior oblique is an abductor also, and secondary or primary overaction of
that muscle will result in a relatively less convergent or more divergent position in
upward gaze, producing a V pattern.

12. Anti-mongoloid
feature
- Upgaze eyes
diverge outwards
- Primary position
eyes are evidently
esotropic
-Downgaze eyes
converge inwards
“V” PATTERN ESOTROPIA:

13. ‘V’ PATTERN ESOTROPIA
This 6 ½ year old boy shows a
very apparent ‘V’ pattern
esotropia, made evident by the
extreme chin-down head
posture, which he has adopted
in order to fuse in primary
position. Evident also is the
apparent ‘upshoot’ of his left eye
on adduction, and apparent
‘overshoot’ on elevation in
adduction, causing both his eyes
to ‘splay outwards’, also evident
on direct upgaze. This is a
result of an evident overation of
his left inferior oblique. On
direct downgaze, his eyes seem
to work in tandem almost
normally.

14. ‘V’ PATTERN STRABISMUS
‘V’ PATTERN EXOTROPIA
• In cases of a ‘V’ pattern exotropia, the deviation of the eyes is more pronounced as the
eyes move more towards midline upgaze rather than midline downgaze.
• There is an evident divergence of the eyes in direct upgaze, with both eyes “splaying
outwards”.
• Overaction of the Inferior oblique can be quite apparent in an evident “upshoot” of the
globe on adduction.
• Similar again to an ‘A’ pattern esotropia, patients will often adopt an abnormal head
posture, except that it will be a chin-up head turn. This allows the patient to achieve
single binocular vision in primary gaze. Parents of children with a ‘V’ pattern will often
notice that their child will occasionally ‘tilt’ their head upwards, to bring their eyes to an
downward position in order to achieve binocular vision in primary gaze.

15. ‘V’ PATTERN EXOTROPIA
This 7-year-old girl presents
with an evident ‘V’ pattern
esotropia, clearly shown by
the chin-up head posture
which she has adopted in
order to obtain single
binocular vision in primary
gaze. Evident is the
significant overaction of her
left inferior oblique in the
form of a gross overshoot of
her left eye in adduction and
elevation in adduction. Also
significant is the quite
evident “outwards splaying’
of both her eyes in direct
upgaze. Note the horizontal
deviation is significantly less
noticeable in downgazes, and
more so in upgazes, hence a
‘V’ pattern.

16. RARER FORMS OF AV PATTERN STRABISMUS

17. ‘A’ PATTERN “LAMBDA” STRABISMUS
This young girl shows a
definitive λ pattern, a variant
of an ‘A’ pattern exotropia,
associated with a bilateral
superior oblique overaction. As
with an ‘A’ pattern exotropia,
she adopts a chin-down head
posture in primary. Note that
the divergence is only
manifested most in downgaze
to her right. The divergence is
evident by the ‘outward
splaying’ of both her eyes on
downgaze right, and direct
downgaze. As with an ‘A’
pattern exotropia, there is a
definite convergence of her eyes
on direct upgaze.

18. ‘X’ PATTERN STRABISMUS
• Patients with ‘X’ pattern often present with a visible exotropia that is only present
or evident in direct upward and downward gaze.
• They often have little to no horizontal deviation on either adduction, or abduction,
with only minimal deviation in primary position.
• Most patients will not adopt an abnormal head posture, but will ‘raise’ or ‘dip’ their
head, depending on which direction they are needing to visualize, be it upgaze or
downgaze, in order to bring both eyes into single binocular vision.

19. ‘X’ PATTERN STRABISMUS
This boy presents with an ‘X’
pattern strabismus, made evident
by that there is a definite
divergence of both eyes, shown by
the hallmark ‘outward splaying’ of
both eyes on both upgaze and
downgaze. This is heightened by
the fact that he ‘dips’ his head
down to bring his eyes “up” on
upgaze, and ‘raises’ his head to
bring his eyes ‘Downwards” on
downgaze. What makes this
pattern difficult to distinguish is
that there is little horizontal
deviation on either adduction or
abduction, and that he doesn’t
adopt any abnormal head posture
in primary.

20. ‘Y’ PATTERN STRABISMUS
• Like ‘X’ pattern, patients with this form of AV pattern strabismus will only display
the deviation of the eye in all gazes above midline gaze.
• There is little to no deviation in either primary position or direct downgaze.
• This pattern is often hard to distinguish from a bilateral Inferior oblique overaction,
but has been documented in the form of ‘Pseudo Y pattern associated with Inferior
Oblique overaction’.
• The most adopted theory as to the cause for a ‘Y’ pattern is an abberant innervation
of the Lateral Rectus in up gaze.

21. ‘Y’ PATTERN ANTI ELEVATION SYNDROME
• Occurs as a complication of the inferior oblique anterior transposition. This
procedure changes the Inferior oblique from being an elevator, which restricts
elevation in adduction.
• Typically, there is marked fundus extortion associated with this sub-pattern of ‘Y’
pattern strabismus.
• Treatment for this usually involves a retroplacement of the anteriorly placed
Inferior oblique, thus reverting it to a standard recession.

22. ‘Y’ PATTERN ANTI-ELEVATION
SYNDROME
This teenage boy shows an Anti-elevation pattern following bilateral IO anterior
transposition. On looking to his left, what looks like an overelevation of his right eye in
abduction, is actually a secondary deviation due to fixation duress. His right (adducted) eye
is ‘stuck’ in an elevated and adducted position, due to the IO now having become an anti-
elevator., thus restricting its normal rotation

23. PSEUDO-INFERIOR OBLIQUE OVERACTION
ASSOCIATED WITH ‘Y’ PATTERN
STRABISMUS
• Described by Dr. Burton J Kushner, Pseudo-inferior oblique overaction occurs in an unusual
manner in which patients with this strabismus pattern will demonstrate the general features of a
‘Y’ pattern, but with the addition of an over elevation of the adducting eye in the field of the inferior
oblique muscle, resulting in a ‘Y’ pattern with a large evident exotropia in all up gazes.
• When compared to a true inferior oblique overaction it is very difficult to distinguish on
presentation. It is only by noting the rapid ‘overshoot’ of the adducting eye as it reaches maximum
elevation from direct adduction. This rapid overshoot of the adducting eye is best seen in still
frames taken from a film of the patient as they look from direct adduction to direct elevation.
• A hypertropia only develops after the eyes have passed beyond midline gaze. This hypertropia then
reverts to a gross abduction of the adducting eye once it has reached maximum elevation in
adduction.

24. PSEUDO ‘Y’ PATTERN STRABISMUS
A) This teenage girl shows a pseudo-inferior
oblique overaction with ‘Y’ pattern exotropia. When
viewed in the field of the inferior obliques, it is
indistinguishable from a true inferior oblique
overaction. In primary and midline gazes there is
no overaction of the inferior oblique. B) It is only by
breaking down the frame rate to 0.1 second
intervals from direct adduction to upgaze in
adduction, can one see that there is no ‘outward
splaying” of the eyes until she has reached
maximum elevation in adduction.
B

25. GRADING OF OBLIQUE
MUSCLE OVERACTION
• Grading of oblique muscle overaction in practice is more of measuring the amount
by visual interpretation rather than exact science. Most surgeons use a grading
scale of 1+ to 4+ overaction. For inferior oblique grading, 1+ overaction means only
slight overaction or over elevation in adduction. Grade 4+ means the most
overelevation possible. Grades 2+ and 3+ overaction are the two gradations between
those extremes.

26. GRADING SEVERITY OF OBLIQUE
OVERACTIONS

27. CAUSES OF AV PATTERN
STRABISMUS
In Strabismic documentation and presentation, there are three main groups of causes
of AV Pattern Strabismus. These are:
• Oblique muscle dysfunction
• Orbital abnormality, and
• Abduction with a large exodeviation

28. MANAGEMENT AND TREATMENT OF AV
PATTERN STRABISMUS
• Of the four main forms of Alphabet pattern
strabismus (‘A’, ‘V’, ‘X’ & ‘Y’) each have certain
methods of treatment. Some correlate with
others while some require more extensive
corrective measures.

29. AV PATTERN STRABISMUS WITH
ORBITAL ABNORMALITY
This young boy has Crouzon’s disease with an evident ‘V’ pattern associated with a craniofacial
abnormality. Note the ‘upshoot’ and ‘downshoot’ of both eyes as he looks to both his left, in
abduction, and right, in adduction. The arrow mark above his left eye is the surgeon’s mark
indicating a left ‘V’ pattern exotropia.

30.  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

31. TREATMENT
• Factors for treatment of A V pattern strabismus are as follows:
• When binocular vision is disturbed, as in A exotropia and V esotropia,
and the treatment is surgery.
• An increase in deviation in downgaze (with A exotropia and V
esotropia) may cause discomfort during reading or in near work.
• Patients with large A or V patterns usually also have significant
corresponding oblique muscle dysfunctions.

32. TREATMENT
• Bilateral superior oblique weakening can collapse large A patterns up 30−40 PD or
more. Bilateral IO weakening is not expected to collapse as large a pattern.
• Bilateral inferior oblique weakening can collapse large V patterns when significant
IO overaction is present.
• In patients with V pattern and IOOA in association with congenital esotropia
complex, consideration should be given to performing IO anterior transposition,
even if DVD is not obvious.
• The A and V patterns can be diminished by horizontal offsets of the vertical rectus
muscles. temporal

33. TREATMENT
TRANSPORTATION OF THE INFERIOR RECTI
• Transposition of the inferior recti will expand the closed end of the V pattern by
weakening the adduction vector of the inferior recti in downgaze. Transposing the
SRs nasally will help close the open end of the V pattern in an exotropic patient and
transposing the IRs nasally will help close an A-pattern exotropia.
M a l e

34. TRANSPOSITION OF THE RECTI TO CORRECT
AV PATTERN STRABISMUS
•
This boy initially presented with a ‘V’ pattern exotropia which is evident by the exotropia of his left eye in
primary, and the ‘outward splaying’ of both eyes in direct upgaze. In the second 9-nine gaze diagnostic
versions, we see him again following a bilateral lateral rectus recession. Now his eyes are straight in
primary position, and there is no evidence of any horizontal deviation in upgaze.

35. IN SUMMARY
• Treatment of AV Patterns is relatively summed up in this crucial treatment goal:
Weaken the Overacting oblique muscles to alleviate the horizontal deviation!!!
• IF, there is no oblique dysfunction, treatment can consist of bilateral or unilateral
surgery on transpositioning of the horizontal recti muscles.
• Regarded as the most recognizable form of Infantile strabismus.
• Evidence of any type of horizontal deviation is particularly demonstrated in either direct
upgaze, or direct downgaze.
• ‘A’ & ‘V’ pattern strabismus accounts for 15-25% of most horizontal strabismus anomalies
to date.

37. REFERENCES
Online references:
• The Strabismus Minute: http://www.cybersight.org
• Strabismus Summary series: http://www.geocities.ws/sapatney/webavst.htm
• McGill University Pediatric & Adult Strabismus:
http://www2.medicine.mcgill.ca/strabismus/atlas/patients/atlasNav/atlas.php
• A Pattern Esotropia & Exotropia/V pattern Esotropia & Exotropia:
https://emedicine.medscape.com/article/1199714-overview
& https://emedicine.medscape.com/article/1199825-overview
• Pattern Strabismus - Grand Round lectures by Dr. Robert O. Hoffman, John A. Moran Eye
care centre, Utah: https://www.youtube.com/watch?v=APjGJ_soPG4

38. REFERENCES CON’T
Paper references:
• Duane A. Isolated paralysis of the ocular muscles. Arch Ophthalmol,1897; 26: 317–34.
• Albert DG. Personal Communication. In Parks MM. Annual review: Strabismus. Arch
Ophthalmol 1957; 58: 136–60.
• Costenbader FD. The “A” and “V” patterns in strabismus. Trans Am Acad Ophthalmol
Otolaryngol, 1964; 68: 354–86.
• Sharat, S. Parija, S. A-V Pattern Strabismus- A Simplified Approach. Orissa Journal of
Ophthalmol 2010; 40-43.
• Kushner BJ. Pseudo inferior oblique overaction associated with ‘Y’ and ‘V’ patterns.
Ophthalmology 1991; 98: 1500–5.

39. REFERENCES CON’T
Textbook references:
• Rosenbaum, Arthur L., Santiago, Alvina P. Clinical Strabismus management. Principles and Surgical techniques.,
The Curtis Centre, Philadelphia, Philadelphia, Pennsylvania. W.B. Saunders ,1999.
• von Noorden, Gunter K. MD, Campos, Emilio C. Binocular Vision and Motility – Theory and management of
Strabismus, 6th edition. Baylor College of Medicine, Houston, Texas, Mosby 2002
• Ellis, George S. At the Crossings – Pediatric Ophthalmology and Strabismus, New Orleans Academy of
Ophthalmology, 2004.
• Taylor, David MD, Hoyt, Creig S. Pediatric Ophthalmology and Strabismus 4th edition. Elsevier Saunders 2005
• Coats, David K., Olitsky, Scott E. Strabismus Surgery and it’s complications, Springer 2007
• Kanski, Jack J., Bowling, Brad. Clinical Ophthalmology – A Systematic approach, 7th edition. ExpertConsult,
Elsevier Saunders, 2011
• Kushner, Burton J. Strabismus – Practical pearls you won’t find in Textbooks. Springer 2017.