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Squint..

squint principles

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  1. 1. Strabismus Samhaa Mohammed Abd Elmoneim Zagazig, 2018
  2. 2. Definitions • Visual axis: from fovea to nodal point to fixation point. • Anatomical axis: from post pole to center of cornea. • Angle kappa: angle between both. Anatomical axis Visual axis
  3. 3. Definitions • Binoocular single vision: 1. simultaneous perception, 2. fusion, 3. stereopsis.  Normal BSV needs: 1. Overlapping VF 2. Normal visual pathway 3. NRC normal retinocortical correspondence 4. Intact motor system 5. Equal image size and clarity of both eyes • Orthoporia: perfect alignment without fusion stimulus! • Heterophoria (latent squint): eye deviation tendency when fusion is blocked. • Heterotropia (manifest squint): misalignment, both visual axes do not intersect at point of fixation.
  4. 4.  Unequal images lead to confusion, diplopia. Or suppresion, ARC in children (sensory adation of squint).  Unequal image lead to head tilt, face turn, chin lift or depress (motor adaptation). Confusion of 2 dissimilar images
  5. 5. EOM
  6. 6. EOM
  7. 7. EOM
  8. 8. EOM action • MR adduction. • LR abduction. • SR elevation, adduction, intortion. • IR depression, adduction, extorter. • SO intorter, depression, abduction. • IO extorter, elevation, abduction.  Any superior is intorter & inferior is extorter.  Any rectus is adducted & oblique is abducted.
  9. 9. EOM action SR, IR 23° 67° • ‫فيه‬ ‫يعملوا‬ ‫وضع‬ ‫أحسن‬ elev/depession ‫والعين‬abducted 23° • ‫فيه‬ ‫يعملوا‬ ‫وضع‬ ‫أحسن‬ cyclotorion ‫والعين‬ adducted 67°
  10. 10. EOM action SO, I0 (Rt eye) 51° 39°51° • ‫فيه‬ ‫يعملوا‬ ‫وضع‬ ‫أحسن‬ cyclotorion ‫والعين‬ abducted 39° • ‫فيه‬ ‫يعملوا‬ ‫وضع‬ ‫أحسن‬ elev/depression ‫والعين‬adducted 51°
  11. 11. EOM • Spiral of tillaux MILS (5.5, 6.5, 6.9, 7.7 mm) from limbus respectively. • Bulley of ms:  CT condensation post to equator  Reducing vertical movement during horizontal action and vice versa, preserve eye movement coordination.  Pulley displacement leads to A, V patterns
  12. 12. Ocular movement • Duction ,Version ,Vergence  Six cardinal position (one ms in each eye is responsible of mov.)  Nine cardinal postions
  13. 13. Ocular movement laws • Synergism (same eye): 2ms of same action  Rt SR &Rt IO • Sherington law (same eye): reciprocal innervation to antagonist (for version & vergence)  Rt MR & Rt LR • Yoke ms (both eyes): for conjugate movement  Rt SO & Lt IR • Hering law (both eyes): equal innervation for yoke ms  Lt LR palsy & Rt MR for fixation (1ry angle of deviation)  Lt LR palsy for fixation & Rt MR (2ry angle of deviation)
  14. 14. 2ry angle of deviation
  15. 15. Definition:↓ BCVA without any ocular pathology. Difference > 2 lines between both eyes. • Strabismic, anisometropic, sensory deprivation types • Usually occurs during critical period→ (Binocular Single Vission) TTT: • Occlusion (reverse amblyopia). Full time occlusion should not exceed 1wk/ 1y • Penalization • Medical , Levodopa, Carbidopa. • Recently, video games training Amblyopia
  16. 16.  Unequal images lead to confusion, diplopia. Or suppresion, ARC in children (sensory adation of squint).  Unequal image lead to head tilt, face turn, chin lift or depress (motor adaptation). Confusion of 2 dissimilar images
  17. 17.  BSV assessment: 1. Base out prism 2. Stereopsis tests (titmus, random dot) 3. Worth four dot test 4. Synsptophore 5. 4 prism test (for mictotropia)  Deviation measurement: • Hirschburg, Bruckner test (1mm = 7° = 15 PD) • Kirmisky test & modified kirmsky (prism reflection test). • Cover (tropia) uncover (phoria) test. • Alternate cover test (for total deviation) • Prism cover, alternate prism cover test. • Maddox wing (for near cyclophoria) • Maddox rod (for far total deviation) • Hess chart (incomitant squint) Assessment of strabismus
  18. 18. Base out prism test
  19. 19. Titmus fly stereo test
  20. 20. Worth 4 dot test
  21. 21. Synaptophore
  22. 22. 4 Δ test
  23. 23. Hirschburg light reflex
  24. 24. Cover uncover test
  25. 25. Alternate cover test
  26. 26. Prism cover test
  27. 27. Prism cover test
  28. 28. Maddox rod test
  29. 29. Squint case basic exam. Exclude pseudo Observe CHP Manifest deviation Hirschburg F & N Pupil margin Midway Limbus Cover / uncover F & N Cover fixated eye & look tropic eye look at covered eye (phoria) Alternate cover F & N Rt or Lt Allternating both eyes Motility 9 cardinal P A V pattern Pursuit & saccade VA, refraction & fundus
  30. 30. Deviation tests Prism tests for deviation Kirmsky Infront fixating eye Modified kirmsky Infront of deviating eye Alternate Prism cover Total angle Other tests Maddox rod Cannot differentiate phoria from tropia Maddox wing Near phoria Post op diplopia test Botulinum toxin
  31. 31. Deviation tests Other tests Hess chart Incomitant squint NPC 10cm NPA 8cm at 20, 45cm at 50y Fusional amplitude Diplopia or eye drift
  32. 32. Types of strabismus True squint Horizontal Esotropia Comitant Angle variation within 5° in all gazes Incomitant Angle variation within > 5° in all gazes Exotropia Comitant Incomitant Vertical 2ry: IOOA SOOA Paralytic: SO palsy IO palsy 3rd n palsy MG Restrictive: Brown $ TED Blow out fracture Multiple ms Congenital fibrosis $ Double elevator palsy DVD (hering law) A & V pattern TED MG
  33. 33. Types of strabismus True esotropia ET Infantile < 6m Infantile essential ET Early accomodative Duan type 1 Mobius syndrom 6th n palsy Nystagmus blockadge $ Acquired Comitant: Accomodative Sensory Consecutive Divergence insuffiency Stress induced Cyclic ET Incomitant : 1. Paralytic 6th n palsy MG 2. Restrictive TED Medial wall fracture Mobius $
  34. 34. Types of strabismus True exotropia XT Congenital < 6m Early onset XT Duan type 2 Acquired Comitant: Intermittent XT Sensory Consecutive Convergence insuffiency Incomitant : 1. Paralytic 3rd n palsy MG INO 2. Restrictive TED
  35. 35. HETEROPHORIA Fusional amplitude is insufficient to maintain alignment. • Associated convergence or divergence excess or insufficiency. • TTT: Orthoptic ttt in convergence weakness, RE correction • Symptom releif using frenel prism. CONVERGENCE INSUFFICIENCY CI More common in individual with high near vision demand (students) • Reduced NPC • TTT: Orthoptic exercise, if persistent (prism base in) ACCOMODATIVE INSUFFICIENCY AI Idiopathic , post viral, treated with weak reading glasses. DIVERGENCE INSUFFICIENCY Exclude neurological cause (SOL, accident) NEAR REFLEX SPASM Pseudomyopia, miosis, ET, female, treated with reassurance, atropine
  36. 36. Types of strabismus True esotropia ET Infantile < 6m Infantile essential ET Early accomodative Duan type 1 Mobius syndrom 6th n palsy Nystagmus blockadge $ Acquired Comitant: Accomodative Sensory Consecutive Divergence insuffiency Stress induced Cyclic ET Incomitant : 1. Paralytic 6th n palsy MG 2. Restrictive TED Medial wall fracture Mobius $
  37. 37. 1. At 6 m. 2. +ve FH 3. Angle: (large angle >30 pd, stable, far>near) 4. Normal RE (not accomodative) 5. Cross fixation in side gaze, alt fixation in PP 6. Latent nystagmus, DVD, IOOA, assym. OKN. 7. Abduction with dolls head maneuver (exclude 6th n palsy) DD: TTT: • Surgery to preseve BSV at 1 y, or at 2 y if EOR. (aim is residual ET 10 pd) • BMRR +/- IOOA ttt • Post op FU for amblyopia (50%), acc. error, microtropia (CSS can preserve BSV), IOOA, DVD. Infantile ET
  38. 38. Alt. fixation in PP Cross fixation in side gaze
  39. 39. Post surgery microtropia IOOA
  40. 40. Refractive accomodative Fully accomodative: Corrected in all distances with glasses. Normal AC/A Normal BSV with optical correction TTT with glasses Partially accomodative: Angle is reduced but not fully eliminated ARC, suppression may occur TTT glasses + surgery Non refractive accomodative Convergence excess High AC/A Normal near point of acc Angle near > far TTT bifocal Hypoacc, convergence excess High AC/A Remote near point of acc Near angle > far TTT bifocal Accomodative ET
  41. 41. DD: TTT: • Hyperopia correction<6y with full cycloplegic error. • After 8 y prescribe error without cyclo. • For convergence excess, bifocal is prescribed to maintain bifoveal fixation at near. • TTT amblyopia. • Surgery indication: ET not fully corrected with glasses. • Amount of surgical correction: 1. Standard: esidual far angle not corrected with glasses→undercorrection. 2. Augmented: average near deviation with & without correction → overcorrection. 3. Prism adaptation: ↑base out prism /wk till stabilized angle. Accomodative ET RE Amblyopia Surgery
  42. 42. Post surgery microtropia IOOA
  43. 43. Partially accomodative Fully accomodative ET
  44. 44. Far orthophoria Near ET Near orthophoria through bifocal
  45. 45. Types of strabismus True exotropia XT Congenital < 6m Early onset XT Duan type 2 Acquired Comitant: Intermittent XT Sensory Consecutive Convergence insuffiency Incomitant : 1. Paralytic 3rd n palsy MG INO 2. Restrictive TED
  46. 46. 1. At birth. 2. Normal refraction. 3. Large constant angle. 4. DVD 5. NEUROLOGICAL anomalies DD: TTT: • Surgery to preseve BSV at 1 y, or at 2 y if EOR. Infantile XT
  47. 47. 1. At 2y, depends on fixation distance & concentration. 2. XP breaks down to XT in inattention, fatigue, illness. 3. Straight with BSV at times, suppression at other times. Classification: 1. D angle > N • Simulated (pseudo divergence excess) due to tonic fusion convergence ↑ AC/A. → D = N after add +3 pd or occlude one eye to relax accomodation. • True divergence excess D> N. 2. N > D in convergence insuffiency. 3. D = N Basic Intermittent XT
  48. 48. TTT: • Overminus RE correction. • Correct amblyopia. • Othoptic fusional exercise for convergence insuffiency → pencil pushups, base out prism. • Surgery indication: • Increase XT angle. • Decrease stereopsis. • Abnormal head posture AHP. Intermittent XT
  49. 49. Surgical TTT: • LR recession. • LR recess, MR resect. • V pattern XT (LR recess + IO weakening or LR upward transposition. 1. Basic (N=D) & pseudo: correct D angle. 2. True divergence excess (D > N): correct ½ ( D angle+ N angle) Intermittent XT
  50. 50. Ortho. XT with fatiglue Lt sensory XT, AHP
  51. 51. • Post ET surgical correction • In amblyopic eye • If early post operative, consider muscle slippage. • Assess post operative diplopia before surgery • Redivergence after 1o y may occur. Consecutive XT
  52. 52. • Mono/ binocular visual defect (media opacity) • Treat cause then squint • Intractable diplopia in minority cases due to loss of fusion Sensory XT
  53. 53. Types of strabismus True squint Horizontal Esotropia Comitant Angle variation within 5° in all gazes Incomitant Angle variation within > 5° in all gazes Exotropia Comitant Incomitant Vertical 2ry: IOOA SOOA Paralytic: SO palsy IO palsy 3rd n palsy MG Restrictive: Brown $ TED Blow out fracture Multiple ms Congenital fibrosis $ Double elevator palsy DVD (hering law) A & V pattern TED MG
  54. 54. • Muscles firosis, dysinnervation!. 1. Duan retraction syndrome 2. Mobius syndrome. 3. Congenital fibrosis of EOM. 4. Strabismus fixus. Congenital cranial dysinnervation disorders
  55. 55. 1. Hypoplastic 6th n nucleus → LR dysinnervation. 2. LR is supplied by fibers from 3rd n. 3. Bilateral often. 4. 50% have deafness, speech, skeletal, external ear problems. C/P 1. Face turn to maintain BSV. 2. Complete / partial LR restriction. 3. Adduction restriction. 4. Globe retraction in adduction, widening or narrowing palpebral fissure (MR, LR cocontraction) 5. Up/ down shot (tight LR). Duane retraction $
  56. 56. Huber classification:  Duane 1: limited or absent abduction, limited or normal adduction, straight or ET.  Duane 2: limited adduction, limited abduction, ortho or slight XT.  Duane 3: limited add, abd, ortho or slight ET. Duane retraction $
  57. 57. Lt Duane 1 Lt duane 3
  58. 58. TTT: • Correct amblyopia. • Surgery indication: • AHP • Unacceptable upshot, down shout • Squint in PP • Never resect. Do recession MR/ LR. Duane retraction $
  59. 59. Mobius syndrome • Sporadic congenital • Bilateral 6th, 7th, n palsy. Lid problem. • 5th, 8th, 10th, 12th may be affected, skeletal Congenital fibrosis of EOM • AD, non progressive. • Bilateral ptosis, restrictive external ophthalmoplegia. Strabismus fixus • Bilateral MR / LR tightening
  60. 60. 7th n palsy, defect in lid closure Tongue atrophy, 12th n palsy Strabismus fixus Convergent & divergent
  61. 61. • SO tendon restriction around trochlea Classification : 1. Congenital: congenital click $. 2. Acquired: trauma, inflamation (RA, scleritis) Signs: • Limited elevation in adduction, PP, normal elevation in abduction. • + ve FDT. • CHP, ipsilat head tilt, hportropia. TTT: treat acquired cause. • Surgery indication (SO lengthenng): AHP, significant hypotropia Brown syndrome
  62. 62. Rt brown syndrome Chin elevation
  63. 63. • Sporadic, Double elevator palsy. • Restrictive contracted IR, hypoplastic SR Signs: • Limited elevation. • Orthophoria in PP • Chin elevation. • + ve FDT. TTT: • Prism base up Monocular elevation defeciency MED
  64. 64. • Up & downgaze difference > 15 pd Causes: • IOOA IN SO palsy • IOOA with infantile ET • SR underaction • Brown $ TTT: • Oblique dysfunction: IO – or SO ++ • V pattern ET: MR rrecession & downward transposition. • V pattern XT: LR recession & upward transposition. Alphabet patterns V pattern MALE (MR to Apex, LR to Empty space)
  65. 65. • Up & downgaze difference > 10 pd • Difficult reading Causes: • SOOA • IO underaction • IR underaction TTT: • Oblique dysfunction: SO -- tenotomy • A pattern ET: MR rrecession & upward transposition. • A pattern XT: LR recession & downward transposition. Alphabet patterns A pattern MALE (MR to Apex, LR to Empty space)
  66. 66. Squint surgery
  67. 67. Strengthening Resection Tucking Advancement Weakening Recession Myotomy Myectomy (disinsertion) Post fixation suture (Faden) Squint surgery
  68. 68. Transposition MALE AV pattern, LR palsy, CCDD Duane Adjustable suture Incomitant (unpredictable results) Squint surgery
  69. 69. LR recession video
  70. 70. MR recession video
  71. 71. LR resection video
  72. 72. SO tucking video
  73. 73. IO myectomy video
  74. 74. IO recession video
  75. 75. Adjustable suture video

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