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13 exotropia
Exotropia is an eye condition where the eyes turn outward. There are several types of exotropia including congenital, sensory, typical childhood, and convergence insufficiency. Exotropia is classified based on fusion status and the AC/A ratio. Treatment involves maximizing vision, glasses, patching, prisms, or surgery. Surgery typically involves recessing the lateral rectus muscles and may also include recessing or resecting the medial rectus muscles. The goal of surgery is to achieve a small angle of esotropia initially to prevent overcorrection and recurrence of exotropia.
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13 exotropia
- 1. Exotropia Pediatric Ophthalmology LSU MedicalCenter in Shreveport
- 2. Cause of Exotropia •In most cases cause is unknown • Theories – Excess divergence – Deficient convergence – Anatomic factors • Familial tendency present • Refractive errors – Average for age unless sensory due to marked anisometropia
- 3. Classification According toFusion Status • Exophoria: X • Intermittent Exotropia: X (T) • Exotropia: XT
- 4. Classification According toAC/A Deviation AC/A Example Convergence Insufficiency Low X= 0, X’= 12, or X(T)= 20, XT’=40 Basic Normal XT= XT’= 20 Divergence Excess High XT= 35, XT’=10
- 5. Exotropia: Clinical Types 1.Congenital 2. Sensory 3. Typical Childhood, or intermittent exotropia 4. Convergence Insufficiency 5. Consecutive
- 6. Secondary Exotropia • Confusingterm but still used at times • May mean occurs following surgery for ET, or • May mean sensory exotropia due to an underlying condition, e.g., anisometropic amblyopia, retinoblastoma, cataract • Better to use either consecutive or sensory rather than secondary to describe exotropia
- 7. Pseudoexotropia: often dueto large angle kappa (e.g. ROP)
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- 11. Congenital Exotropia • Rare •Constant Exotropia • Large angle • Often associated with other neurologic defects • Only treatment is surgical
- 12. Sensory Exotropia • Poorvision in one eye leads to exotropia • Sensory esotropia or exotropia may occur • Causes – Marked anisometropia • E.g., unilateral high myopia • Retinoblastoma (22% present with strabismus) • Unilateral cataract
- 13. Sensory Exotropia: Treatment 1.Treat underlying cause if possible • E.g. remove cataract, treat amblyopia 1. Surgery for exotropia • Fusional outlook variable • Small XT often best left alone
- 14. Convergence Insufficiency: Two Subtypes 1.Ex= 0, Exophoria or Exotropia at near • Low AC/A ratio • Remote NPC • Poor fusional convergence amplitudes • Usually responds to convergence exercises • Website: “ Computer Orthoptics (HTS)” exercises online or in office vision therapy combined with home therapy • May treat with base in prism • Usually do poorly with surgery
- 15. Convergence Insufficiency: Second Subtype •XT at distance, larger XT at near – Deficient accommodative convergence – Very low AC/A ratio – Poor response to convergence exercises – Often undercorrected with recess LR OU – Treatment: unilateral recess/resect or recess/tuck
- 16. Typical Childhood Exotropia orIntermittent Exotropia • Onset 6 months to 6 years of age • Average refractive errors • Deviation usually noted first with distance vision • Often normal sensory pattern when eyes aligned • Many progress through different phases • Some remain stable and do not progress
- 17. Progression of Exotropia •Phoria→ Tropia • Distance deviation> Near deviation • Progression more rapid under age 6, but progression in adulthood common also(may present with diplopia)
- 18. Typical Childhood Exotropia Phase0 • X but no XT and no X (T) • Usually no symptoms • No suppression
- 19. Typical Childhood Exotropia Phase1 • X (T) present, Ex’ = 0 • Mostly controlled • Symptoms often present – Diplopia: may close one eye – Noted by peers
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- 22. Exotropia: Area ofTemporal Retina Suppressed
- 23. Binocular Perimetry InExotropia: Nasal Scotoma
- 24. Alternating Scotoma inAlternating Exotropia
- 25. Typical Childhood Exotropia Phase2 • XT constant at distance, X’ or X(T)’ • Deviation noticeable • Fewer symptoms: suppression usually present • Divergence excess pattern ( or pseudo- divergence excess) common
- 26. Typical Childhood Exotropia Phase3 • XT constant at distance and near • Noticeable • Usually no diplopia present • Amblyopia may be present
- 27. Clinical Course ofTypical Childhood Exotropia Phase Deviation at distance Deviation at near Diplopia Suppression 0 X X’ _ _ 1 X(T) X’ + _ 2 XT X(T)’ or X’ _ + 3 XT XT’ _ +
- 28. Kushner’s Classification of Exotropia TypeDescription Percent Basic XT=XT’ 37 Tenacious Proximal fusion XT>XT’, but after 60 minutes occlusion, XT=XT’ 40 High AC/A Ratio XT>XT’ and hi AC/A with minus lenses 5 True Divergence Excess XT>XT’ even after 60 minutes occlusion, but AC/A normal 4 Convergence Insufficiency Ex= 0, X’or XT< XT’ 4 Pseudo convergence insufficiency XT<XT’, but after 1 hour occlusion, XT=XT’ <1
- 29. Non Surgical Treatmentof Exotropia 1. Maximize vision – Glasses especially for myopia – Treat amblyopia 1. Minus lenses 2. Base in prism with or without minus lenses 3. Orthoptics • Mainly useful for convergence insufficiency with Ex=0, X’ or X(T)’ 5. Part time patching: may improve control
- 30. Prisms for Exotropia •Base In Prisms useful in – Small angle exotropia – For reading with convergence insufficiency • Base out Prisms: – Temporary treatment of esotropia after exotropia surgery
- 31. Non Surgical Treatmentof XT • 7 y/o: VA OD 20/80, OS 20/80 • X (T) = 30 • Refraction: OD –1.50 20/20 • OS –1.50 20/20 • Rx: glasses • Six weeks later Ex=0 with glasses
- 32. Surgical Treatment ofExotropia • Rarely if ever improves (4% in one study) • Natural course – Neonatal exotropia often improves spontaneously – Some infantile exotropia remains intermittent – Other cases become constant exotropia – Most progress to some degree
- 33. Surgical Treatment ofExotropia • Maximize vision first • Phase 0: X, no XT – No treatment needed
- 34. Surgical Treatment ofExotropia • Phase 1: X(T), Ex’=0 • Watch if: – Infrequent deviation – No symptoms: peers or patient • Operate if: – Deviation frequent – Progressive deviation – Symptomatic
- 35. Surgical Treatment ofExotropia • Phase 2: XT at distance, X’ or X(T)’ near – Surgery recommended without delay – Patient in danger of losing binocular vision • Phase 3: XT far, XT’ near – Surgery for social reasons if desired – Small chance of improving binocularity
- 36. Surgery for Exotropia •Children under age 5 – 18 diopters or less: can recess one lateral rectus – Over 20 diopters: recess LR OU but use 2/3 amount of adult “numbers” – High chance of overcorrection with recession LR OU if use regular adult numbers for surgery in young children
- 37. Surgery for Exotropia •Usually recess LR OU as initial operation • Convergence insufficiency with XT distance less than XT at near: – Recess one LR, Resect one MR • Poor vision in one eye – Recess LR, Resect/Tuck MR of eye with reduced vision
- 38. Surgery for Exotropia •Beware of surgery for high AC/A ratio – Surgery for distance deviation likely to cause esotropia and diplopia at near • If prolonged cover testing reveals no deviation at near: patch one eye 60 minutes – If XT or X appears at near less than XT at distance: recess LR OU – If no deviation at near after patching: measure AC/A ratio at distance with minus lenses • If high AC/A ratio: prescribe minus lenses • Can do recession LR OU with posterior fixation MR OU
- 39. Exotropia: Clinical Examples 1.2 y/o X(T) = 30, X’=18 2. 6 month old XT=XT’=55 3. 6 y/o VA OD 20/20, OS 20/200 • CR: OD + 0.25, OS –6.00 • LXT = 25
- 40. Exotropia: Clinical Examples 4.12 y/o XT= 30. Surgery for ET age 3 5. 23 y/o medical student – Eyes tired with reading – Ex=0, X(T)= 15
- 41. Surgical Treatment ofExotropia • Basic Exotropia XT=XT’ – May be treated with Recess LR OU or recess one LR, resect/tuck one MR – Various studies show different results, some advocate one operation over the other – Most surgeons currently use recess LR OU
- 42. Surgical Treatment ofExotropia • Desired position of eyes one week post op is: – LR recession OU over age 5: ET 4-10 diopters – Eyes become more exo in the weeks following surgery – High recurrence rate if XT undercorrected at age one week – With Recession one LR, desire smaller E after surgery (2-6 diopters)