A – V PATTERNS : Introduction , Types & Management

A – V PATTERNS : Introduction , Types & Management

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  A – VPATTERNS Jasmin
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  Context
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  Introduction • Horizontal deviationsare comitant in horizontal gaze but may not in vertical gaze • Vertical are not…..It is called as ….. vertical incomitant comitant horizontal deviation • Introduced alphabets The latter is because the changes of horizontal deviation in up- and downgaze resembles the alphabets A or V.
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  What is A& V Pattern Exodeviation which becomes more divergent in upgaze and less divergent in the downgaze V V A A
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  • 1. A-exotropia(exodeviation more in down gaze, less in upgaze). • 2. A-esotropia (esodeviation less in down gaze, more in upgaze). • 3. V-exotropia (exodeviation more in up gaze, less in downgaze). • 4. V-esotropia (esodeviation less in upgaze, more in downgaze). It may • be a pure V-pattern with exodeviation in upgaze, esodeviation in • downgaze and ortho-in primary position. • 5. X-exotropia (exodeviation more in both up and downgazes). • 6. Y-exotropia (exodeviation more in upgaze only). • 7. λ-exotropia (exodeviation more in down-gaze only), delta exotropia. • 8. exotropia (diamond exotropia) exodevia- tion only in primary position • not in up and downgazes. • Clinically these patterns may be present with or without oblique muscle overactions
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  Prevalance • Since Urrets-Zavaliadescribed them in 1948, A and V patterns have been commonly seen in at least one-third of esotropia and exotropia. • V patterns are more common than A patterns. While esodeviations are more common in the West the exodeviations are more common in the Indian and the African races. The A- esotropia is the least type of pattern amongst the four main types, otherwise the diamond pattern is the least of all.
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  Etiology : Horizontalschool • Urist championed the role of horizontal recti, assuming that lateral recti are more effective in upgaze and medial recti more effective in downgaze. An overaction of lateral recti causes V-exotropia and underaction of medial recti causes A-esotropia • Cases with A-V patterns which do not have oblique muscle overactions could be responsible because of this factor. Based on this principle Urist advocated surgery to correct the specific anomaly, i.e. in case of overaction of the recti, recess them and in case of underaction resect them.
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  Pattern Caused by V-exotropiaOveraction lateral recti V-esotropia Overaction of medial recti A-exotropia Underaction of lateral recti A-esotropia Underaction of medial recti
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  Vertical school • Theprinciple behind being the adducting property of vertical recti. Thus weak superior recti would result in less adducting power in upgaze causing a V pheno-menon. However, it seems logical to think that the actions of vertical recti and oblique muscles are linked inseparably. • Thus underacting superior recti would have underacting superior obliques (ipsilateral antagonist of contralateral syner gist). • Thus it would be more appropriate to have the vertical recti and obliques as a combined factor this is the cyclovertical school
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  Pattern caused by Inferior obliqueSuperior oblique V pattern Inferior rectus Superior rectus V pattern Superior oblique Inferior oblique A pattern SuperiorSuperior Inferior rectus A pattern
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  Structural factors • Thetrochlea acts as the functional origin of the superior oblique. • The role of sagittalization: the oblique muscles becoming more parallel to the sagittal (anteroposterior) axis • Desagittalization: when the oblique muscles become more parallel to the coronal plane have been stressed by Gobin. If the superior oblique is desagittalised due to the retro placement of trochlea (as in plagiocephaly), it becomes a poorer depressor. And relatively the inferior oblique becomes a stronger elevator (Figs 9.10a and b). • Similarly with a more frontally placed trochlea (as in hydrocephalus with frontal bossing), superior oblique becomes more sagittalised in relation to the inferior oblique making it a stronger elevator. This relative action of the obliques can cause A and V patterns.
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  • Sagittalization and desagittalizationof superior obliques (SO) sagittal axis (SA). Trochlea • (TN = normal position) Ts: anteriorly placed trochlea = sagittalization TD: posteriorly placed trochlea • = desagittalization
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  Diagnosis • The horizontaldeviations are measured in 25° upgaze and 35° downgaze in addition to the primary position. Sometimes it may be desirable to check in 45° downgaze position to exclude a significant A pattern. • A 15 pd difference is taken as significant for a V pattern and a 10 pd difference is taken as significant for A pattern. For repeatable and reproducible measurements these positions are quantified with the help of a scale and a protractor on the lateral side of the head. A 35° chin-up and 25° chin down position is used with a 6 m distance target for distance fixation measurement. For near fixation at 33 cm, either the head is similarly tilted or the target is suitably fixed. • A cephalodeviometer has been devised using a mirror with markings drawn on it. The patient is made to wear a head band with a vertical marker, and head is suitably tilted for the required position. • Children with V-exotropia with BSV in downgaze may have a chin-up posture and with A-esotropia with BSV in upgaze may have a chin down
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  • The fundusshould always be evaluated for the torsional changes in A-V patterns especially with oblique overactions • Fundus picture of a case with V pattern with inferior oblique overaction (left eye) showing extorsion in (a), and corrected after surgery (b).
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  Treatment
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  5. V-esotropia withoutoveraction Bi-medial recession with MR down-shifted 5 mm 6. V-exotropia (no overaction) Bi-lateral recession with LR up-shifted 5 mm 7. A-esotropia (no overaction) Bi-medial recession with MR shifted up 5 mm 8. A-exotropia (no overaction) Bi-lateral recession with LR shifted down 5 mm 9. Pure V-pattern (exo-up, eso- Bilateral Inferior oblique down) (Figs 9.15a and b) weakening 10. Pure A pattern (eso-up, exodown) Bilateral superior oblique weakening 11. X-pattern with inferior and superior oblique overaction Pattern & Surgery 1. V-esotropia with inferior overaction Medial rectus recession or recession-resection surgery + inferior oblique weakening 2. V-exotropia with inferior oblique overaction (Figs 9.13a and b) Lateral rectus recession or R-R surgery + inferior oblique weakening 3. A-esotropia with superior oblique overaction Medial rectus recession or R-R surgery + Superior oblique weakening 4. A-exotropia with superior oblique overaction (Figs 9.14a and b) Lateral rectus recession or R-R surgery + Superior oblique weakening