Pattern strabismus
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what is strabismus ? what are different type of verticle squint ? what is A pattern = means a relative convergence in upgaze & relative divergence in down gaze with minimum difference of 10 PD between upgaze & downgaze . what is V pattern strabismus ? it is relative divergence in upgaze & relative convergence in downgaze with minimum difference of 15 PD between upgaze & downgaze … what is alphabate pattern strabismus ? PBCT is more sensitive than Krimsky test ? the measurement of squint in upgae 25 degree & in downgaze 33-35 degree i.e PBCT ( PRISM BAR COVER TEST ) what is Lamba pattern strabismus ? what is X pattern strabismus ? what is delta pattern ?
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Pattern strabismus
- 1. Pattern strabismus 6th January, 2020
- 2. Contents • Introduction • Etiology • Clinical features • V pattern • A pattern • Y pattern • X pattern
- 3. Definition • The presence of significant incomitance from upgaze to downgaze in patients who have esotropia, exotropia, or no horizontal misalignment in primary position
- 4. Introduction • A horizontal deviation changes in magnitude between upgaze and downgaze • V pattern : Most common type • A pattern • Y , X , λ (lambda) pattern
- 5. Incidence Data from Costenbader FD.Trans Am Acad Ophthalmol Otolaryngol 1964;68:354–5.
- 6. Etiology
- 7. Etiology • Dysfunction of oblique muscles / Oblique school • Dysfunction of horizontal rectus muscles / Horizontal school • Dysfunction of vertical rectus muscles/Vertical school
- 8. Dysfunction of oblique muscles • Oblique school • Apparent inferior oblique muscle overaction :V patterns • Superior oblique muscle overaction : A patterns
- 9. Dysfunction of horizontal rectus muscles • Varying effectiveness of the lateral rectus muscles in the upper half of the vertical gaze field and of the medial rectus muscles in the lower half of this field • Increases in lateral rectus or medial rectus muscle action produce :V pattern • Decreased action of these muscles produces : A pattern
- 10. Horizontal school • V pattern esotropia: OA of MR on downgaze • V pattern exotropia : OA of LR on upgaze • A pattern exotropia: UA of MR on downgaze • A pattern esotropia: UA of LR on upgaze
- 11. Dysfunction of vertical rectus muscles • Increases or decreases in the tertiary adducting action of these muscles may result in a less convergent or more divergent alignment in upgaze or downgaze and a corresponding pattern
- 12. Vertical school • A syndrome Upgaze :Elevators contracting, the increased adduction of eyes could be caused by OA of SR and by UA of IO Downgaze: Depressors contracting and the increased abduction could be due to OA of SOs and UA of IR
- 13. Vertical school • V syndrome Increased abduction in upgaze - OA of IOs and UA of SR Increased adduction in downgaze - OA of IR and UA of SO
- 15. High risk • Craniofacial anomalies like craniosynostosis, spina bifida • Antimongoloid lid fissures (A eXotropia andV eSotropia) • Mongoloid lid fissures (A eSotropia andV eXotropia) • Infantile esotropia (V eSotropia)
- 16. Clinical features • Symptoms • Age at presentation : 12 months or younger • Not recognised until the early school • Asthenopia and Diplopia A eXotropia andV eSotropia
- 17. Signs • Anomalous Head Posture V esotropia and A exotropia have fusion in the upward gaze -----So usually have chin depression
- 18. Signs • Anomalous Head Posture A esotropia andV exotropia have fusion in the downward gaze ------So usually have chin elevation • Amblyopia
- 19. Identification • Measuring alignment • Patient fixates on an accommodative target at distance • Primary position and in straight upgaze and downgaze, approximately 25° from the primary position • Proper refractive correction
- 20. V pattern
- 21. V pattern • Most common type of pattern strabismus • Occurs most frequently in patients with infantile esotropia
- 22. V pattern • A ‘V’ pattern is said to be significant when the difference between upgaze and downgaze is ≥15 Δ
- 23. Causes • Inferior oblique overaction associated with fourth nerve palsy • Superior oblique underaction with subsequent inferior oblique overaction • Superior rectus underaction • Brown syndrome • Craniofacial anomalies featuring shallow orbits and down- slanting palpebral fissures
- 24. Treatment • Oblique dysfunction is present - Inferior oblique weakening or superior oblique strengthening • No oblique dysfunction ‘V’ pattern esotropia : bilateral medial rectus recessions and downward transposition of the tendons ‘V’ pattern exotropia : bilateral lateral rectus recessions and upward transposition of the tendons
- 25. A pattern
- 26. A pattern • Second most common type • Occur most frequently in patients with exotropia • Craniofacial malformations,Trisomy 21, Myelomeningocele
- 27. A pattern • An ‘A’ pattern is considered significant if the difference between upgaze and downgaze is ≥10 Δ • Difficulty with reading
- 28. Causes • Primary superior oblique overaction is usually associated with exodeviation in the primary position of gaze • Inferior oblique underaction/palsy with subsequent superior oblique overaction • Inferior rectus underaction
- 29. Treatment • Oblique dysfunction - Superior oblique posterior tenotomy • Without oblique muscle dysfunction ‘A’ pattern esotropia : bilateral lateral rectus resections and downward transposition of the tendons ‘A’ pattern exotropia :bilateral medial rectus resections and upward transposition of the tendons
- 30. Y Pattern
- 31. Y Pattern • Normal ocular alignment in primary position and downgaze • Diverge in upgaze • Appear to have overacting inferior oblique muscles, but the deviation actually results from aberrant innervation of the lateral rectus muscles in upgaze
- 32. Y Pattern- clinical characteristics (1)The overelevation is not seen when the eyes are moved directly horizontally, but it becomes manifest when the eyes are moved medially and slightly elevated (2)There is no fundus torsion (3)There is no difference in vertical deviation with head tilt (4)There is no superior oblique muscle underaction
- 33. X Pattern
- 34. X Pattern • When the deviation in primary position increases in both upgaze and downgaze • Associated with overelevation and overdepression in adduction when the eye moves slightly above or below direct side gaze • Most commonly seen - Large-angle exotropia - The apparent overaction results from contracture of the lateral rectus muscle, with slippage of the globe as the eye adducts
- 35. λ Pattern
- 36. λ Pattern • Rare pattern is a variant of A-pattern exotropia • It is present when the deviation is the same in primary position and upgaze and increases in downgaze
- 37. Take home message • Common entity • Countless surgical overcorrections and undercorrections have been made due to failure to recognise patterns
- 38. References • Pediatric Ophthalmology and strabismus , AAO, 2015-2016 • BinocularVision & Strabismus – GkVon Noorden -5th Edition • Clinical Ophthalmology ,Kanski -8th Edition • MyronYanoff ,Ophthalmology 4th edition
Editor's Notes
- Selective innervation of horizontal rectus muscles Abnormalities of the orbital pulley system
- Whether a true primary overaction of the oblique muscles exists, especially with respect to their vertical actions, is controversial (see Chapter 11). Because the terms overelevation in adduction (OEAd) and overdepression in adduction (ODAd) accurately describe the abnormality without implying an etiology, they have been suggested as alternatives to the traditional terminology.
- 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
- superior rectus muscles are primarily underacting, their adductive effect in upward gaze will diminish; in fact, the eyes will diverge in upward gaze because of secondary overaction of the inferior oblique muscles.
- small in magnitude it may not be recognised until the early school when head posture becomes apparent or reading difficulties are noted
- V esotropia with chin depression. Upward gaze, 8 intermittent exotropia; primary position, 30 esotropia The patient with A esotropia and V exotropia and fusion in downward gaze may hold his or her chin in an elevated position. Conversely, V esotropia and A exotropia may cause chin depression (ET); downward gaze, 45 ET.
- 11% of patients with alphabet patterns---Kushner BJ. Ocular causes of abnormal head posture. Ophthalmology 1979;
- An A pattern is considered clinically significant when the difference in measurement between upgaze and downgaze is at least 10 prism diopters (Δ); for a V pattern, the difference must be at least 15Δ. The difference is larger for a V pattern because normally there is some physiologic convergence in downgaze Full refractive correction should be worn and accommodation should be well controlled to prevent the appearance of pseudo V pattern
- Usually, the pattern is not present when the esotropia first develops but becomes apparent during the first year of life or later. V patterns also may occur in patients with superior oblique palsies, particularly if they are bilateral, and in patients with craniofacial malformations
- The muscles are transposed from one-half of the width to the full width of the insertion. The medial rectus muscles are always moved toward the “apex” of the pattern (ie, upward in A patterns and downward in V patterns). The lateral rectus muscles are moved toward the open end or “empty space” (ie, upward in V patterns and downward in A patterns). A useful mnemonic is MALE: Medial rectus muscle to the apex, lateral rectus muscle to the empty space. These rules apply whether the horizontal rectus muscles are weakened or tightened
- Tenectomy of the posterior 7/8 of the insertions is an effective method for treating approximately 20Δ of A pattern, with no significant effect on torsion. Lengthening of the tendon by recession, insertion of a spacer, or a Z-lengthening procedure may also be used. Bilateral superior oblique tenotomy is a very powerful procedure that may correct up to 40Δ–50Δ of A pattern. There is a risk of induced torsional imbalance with this procedure, which may cause problems for patients with fusional ability. The muscles are transposed from one-half of the width to the full width of the insertion. The medial rectus muscles are always moved toward the “apex” of the pattern (ie, upward in A patterns and downward in V patterns). The lateral rectus muscles are moved toward the open end or “empty space” (ie, upward in V patterns and downward in A patterns). A useful mnemonic is MALE: Medial rectus muscle to the apex, lateral rectus muscle to the empty space. These rules apply whether the horizontal rectus muscles are weakened or tightened
- The λ pattern is usually associated with ODAd.