Amblyopia : classification & Occlusion therapy

defintion classification and treatment of amblyopia

1. Amblyopia : Classification and Occlusion Therapy Moderator presenters Dr.sanjeev bhattarai aayush chandan aastha subedi

2. PRESENTATION LAYOUT Introduction Pathophysiology Classification & types Clinical characteristics Clinical evaluation & diagnosis Management Occlusion Therapy References

3. Definition Derived from Greek word ( Amblyos : Dullness/Blunt ; Ops : Vision ) U/L or less commonly B/L reduction in BCVA that cannot be attributed directly to the affect of any structural abnormality of the eye or the posterior visual pathway Main cause of decreased vision in childhood Difference of >2 lines between 2 eyes

4. Prevalence Variable 2.0-2.5% of general population Preschool/school age children : 4.0-5.3% Globally 1.0-5.0% (WHO) In Nepal around 0.9-1.8%

5. Risk factors 4 times more prevalent in LBW & premature baby 6 times more prevalent in delayed milestone & CNS disorders Smoking & use of Drugs & alcohol during pregnancy have been a/w risk of amblyopia

6. Sensitive Period The capacity of the visual system to develop amblyopia is limited by its state of maturity During immaturity of the visual system the retinocortical connections are not firmly established and may be modified by the quantity or quality of the visual input This phase has been described as the sensitive, critical , or susceptible period The human is most sensitive to environmental manipulation during the first 2 years of life The human critical period is over by approximately 7 to 9 years of age

7. Classification Functional amblyopia Organic amblyopia Reversible Irreversible Refers to obligatory psychical suppression of the retinal image Refers to partial loss of vision caused by undetectable organic lesions in the eye or in the visual pathway Can be : Strabismic , Ametropic , Anisometropic , Meridional , Stimulus Deprivation Can be : Nutritional , Toxic , d/t Retinal diseases , Idiopathic Usually in Childhood Can cause VA defect at any age

8. Amblyopia of Arrest vs Extinction Given by Chavasse Amblyopia of Arrest caused by interference with the fixation reflex that begins before 6 months of age i.e. during critical period of development Amblyopia of extinction resulting from suppression of an already existing visual acuity (possible in children upto 6 years of age)

9. Pathophysiology

10. Amblyogenic factors

11. Role of Retina Decreased sensitivity of foveal cones in amblyopia Decreased inputs from rods & cones in the affected eye cause certain neurophysioloic changes, transmitted to the CNS which triggers amblyopia

12. Active Cortical Inhibition A developmental defect of spatial visual processing occurring in the visual pathway . Poor transmission from the fovea, optic nerve to the Striate Cortex of the affected eye. LGB & Striate cortex develop abnormally. Ganglion cells in foveal area are affected; Shrinkage of LGB Nucleus & Striate cortical fibres in the amblyopic eye . Loss of binocularly driven cells in LGB & Striate Cortex

13. Classification & types Strabismic amblyopia Stimulus deprivation or amblyopia of disuse Anisometropic amblyopia Meridional amblyopia Isoametropic amblyopia Amblyopia secondary to nystagmus Idiopathic amblyopia Organic amblyopia

14. Strabismic amblyopia Most common form of amblyopia Amblyopia is unilateral Seen in unilateral constant squint who strongly favour one eye for fixation Will develop in 100% of pts with constant untreated acquired esotropia under 3 years of age resulting in marked decrease in VA within week(treatment of this type of amblyopia following acquired esotropia therefore becomes daytime emergency) 19.7% of congenital cases of esotropia if untreated

15. Caused by active inhibition within the retinocortical pathway of visual input originating in the fovea of the deviating eye. Far more often in esotropes than in exotropes because exotropia is often intermittent at its onset Also be related to the nasotemporal asymmetry of the retinocortical projections. In esotropes the fovea of the deviating eye has to compete with the strong temporal hemifield of the fellow eye . In exotropia the fovea competes with the weaker contralateral nasal hemifield a/k suppression amblyopia Contd …

16. Stimulus deprivation amblyopia/Amblyopia of disuse(Amblyopia Ex Anopsia ) Primary cause is d/t disuse/under stimulation of the retina. Least common but most damaging. Caused when visual axis is obstructed.

17. Conditions exists in -opacities of the ocular media s/a congenital or traumatic cataract, corneal opacities , blepharospasm , surgical lid closure , or U/L Complete ptosis - B/L ptosis is not amblyogenic because the pt maintains normal VA with a chin elevation

18. Anisometropic Amblyopia Abnormal binocular interaction caused by unequal fovea images in the two eyes causes development of the anisometropic amblyopia. Always U/L D/t active inhibition of the fovea. 30% of the cases are a/w strabismus With reduction in central VA , overall reduction of the contrast sensitivity 2 nd main cause of amblyopia.

19. The amount of anisometropia that can induce amblyopia varies a/c to type of refractive error Hypermetropic anisometropia is more amblyopic than myopic anisometropia However U/L high myopia (-6D or more) often results in severe amblyopia. Refractive error Amount of anisometropia Hypermetropia 1-2D Myopia 3D or more Astigmatism >1.25D

20. Meridional Amblyopia Amblyopia occurring in pts with uncorrected astigmatic refractive error d/t selective visual deprivation for visual stimulation of certain spatial orientation. occurs when a child progresses through the critical period with one visual meridian in sharper focus than the other. One study showed that half of neonates manifest astigmatism of between 0.75 and 2.00 D I t is probably best to consider prescribing lenses for young, school-age children if the astigmatism shows no signs of abating and is at least 2.00 D

21. Clinical highlight Meridional amblyopia is seen commonly in clinical practice. Depending on the meridian affected, certain optotypes can be especially difficult to resolve In the case of simple myopic, with-the-rule astigmatism ,horizontal gratings are out of focus. Consequently, a patient with meridional amblyopia secondary to this refractive error may find it difficult to resolve optotypes such as E or F , which have substantial horizontal components

22. Isoametropic amblyopia B/L amblyopia occurring in children with B/L uncorrected high refractive error. Results from the effect of blurred retinal image alone. Hyperopia > +5D Myopia > -10D Astigmatism >2D-2.5D

23. Amblyopia secondary to nystagmus B/L amblyopia may occur secondary to nystagmus But difficult to ascertain whether nystagmus is the cause or effect of reduced VA

24. Idiopathic Amblyopia U/L amblyopia occurring in apparently normal pt. with a negative history for strabismus & in the absence of other usual amblyogenic factors. Such pts have foveal suppression & VA improves after patching of the sound eye. A/c to Von Norden ; occurs d/t some amblyogenic factors (s/a transient anisometropia ) which are present in infancy for a short period but disappears with advancing age. In support of this hypothesis are observations that clinically significant astigmatism or anisometropia in infancy may disappear with advancing age

25. Organic Amblyopia Irreversible type which results from some pathological or anatomical abnormalities of retina R etinal eye disease -Toxoplasmosis chorioretinitis , Retinoblastoma , traumatic retinal lesion Nutritional amblyopia -occurs from nutrition deficiencies

26. Toxic amblyopia Vision loss d/t damage to the optic nerve fibrosis d/t effects of exogenous or endogenous poisons Types : Tobacco amblyopia Ethyl alcohol amblyopia Methyl alcohol amblyopia Quinine amblyopia Ethambutol amblyopia

27. Tobacco amblyopia -Typically occurs in men in pipe smokers, heavy drinkers Ethyl alcohol amblyopia -Usually in a/w tobacco amblyopia -May occur in non-smoker but heavy drinkers suffering from chronic gastritis

28. Methyl alcohol amblyopia -It is typically acute usually resulting in optic atrophy & permanent blindness Quinine amblyopia -May occur even with small doses of the drugs in susceptible individuals Ethambutol amblyopia -caused d/t anti-tubercular drugs

29. Clinical characteristics

30. Visual acuity Two line difference between amblyopic & normal eye. For B/L amblyopia VA should be less than 20/40 in each eye. Recognition acuity is more affected than resolution acuity & detection acuity. Snellens acuity & grating acuity are affected equally in anisometropic amblyopia whereas in strabismic amblyopia grating acuity is affected to half the extent of snellens acuity( strabismic amblyopia is under-estimated on grating test)

31. Stereoacuity Presence of amblyopia can be detected by defective performance on various stereograms Two pencil test is a clinically useful test and can be applied even when VA recording is unreliable or not possible Can also be easured by titmus fly test, randomdot stereogram

32. Neutral density filter NDF reduces overall luminance without inducing a color change Decreased luminance of the visual target results in diminished central acuity in normal eyes Decreased luminance of visual target has less of an effect on amblyopic eyes because they are not using central acuity It was found that neutral filters profoundly reduce vision in eyes with organic amblyopia whereas vision of eyes with functional amblyopia was not reduced & occasionally even slightly improved

33. Telescope test Chart is viewed with amblyopic eye with 2.5xtelescope If organic amblyopia acuity increase by a factor of 2.5 (20\100 improve to 20\40) If further improvement in visual acuity it is functional amblyopia(20\100 to 20\25)

34. Pharmacological effects o n Vision of amblyopic eyes Gallois found that the use of vasodilators improved vision of amblyopic eyes. Duffy et al found that Bicuculline a ϒ - aminobutyric acid (GABA) receptor blocker If injected intracisternally in animals , substances involved in the maturation of the central nervous system delayed the maturation time and therefore eliminated the occurrence of amblyopia.

35. Crowding phenomenon/Spatial interaction Amblyopic pts exhibit better VA for single O ptotypes than for letters placed in a row . Although not specific for amblyopia, it may be pronounced in amblyopic eye compared to better eye. Based on phenomenon of simultaneous masking U se of spatial gratings (the mask) to interfere with the detection of a stimulus composed of similar frequencies (the target). Since both frequencies share the same spatial frequency channels, there is a reduction in the visibility of the target gratings.

36. Single line acuity improves more than line acuity during treatment So it is important to record both single & line visual acuity everytime as it is prognostic indicator . Vision testing with single optotype is likely to overestimate VA in pts with amblyopia More accurate assesment of monocular VA is obtained with the presentation of line of optotypes or single optotype with crowding bars that surround the optotype being identified

37. Fixation pattern Bangerter’s classified fixation pattern in amblyopia as : i.central fixation ii.Eccentric fixation( nonfoveolar ) iii.No fixation Eccentric fixation can be divided into: a.parafoveolar (adjacent to foveolar reflex) b.parafoveal (outside but close to foveal wall) c.peripheral eccentric(somewhere between edges of fovea & disc)

38. Visual field Monocular VF are usually recorded as normal in strabismic amblyopia . Although there is obviously a relative defect in the fovea it is difficult to demonstrate it on a target screen or goldmann perimeter This clearly differentiates strabismic amblyopia from organic amblyopia in which a scotoma involving the fovea area can be plotted

39. Localization of an object of regard Localization of an object of regard is normal in patients having amblyopia with central as well as eccentric fixation . However ,in patients having amblyopia with eccentric viewing , localization of an object of regard is faulty.

40. Color vision Often abnormal , esp. when the amblyopia is severe . Could simply be a function of the eccentricity of fixation.

41. Pupillary Responses An afferent pupillary defect of amblyopic eyes has been reported by several authors( 9% to 93 %) ( Dole´nek ) On Pupillographic measurements on the eyes of amblyopic children it was found that on average the pupil of the amblyopic eye was 0.5 mm larger than the pupil of the normal eye in the natural state and 0.3 mm larger in miosis induced by a light stimulus ( Dole’nek & Kru¨ger ).

42. Dark Adaptation The dark adaptation curves to colored test targets of 26 amblyopic subjects were studied. Their normal eyes were used as controls. No defects were found in the group having foveal fixation, but significant defects were uncovered in the group having eccentric fixation Dark Adaptation in Strabismic Amblyopia; The Use of Colored Filters Flynn J.T. · Glaser J.S .  November 27, 2009

43. Critical Flicker Frequency Elevation of the CFF in the macular region relative to peripheral area.( Lohmann & Teraskeli ) Normal CFF values in amblyopic eyes.( Weekers et al) No difference in foveal CFF of amblyopic eye and its fellow eye CFF was significantly faster in amblyopic eye that fixated eccentrically than in those with foveal fixation.( Jacobson et al)

44. Electrophysiology Recordings ERG is essentially normal & EOG shows unsteadiness of fixation in Amblyopia . Reduction in amplitude & slightly prolonged Latency in found in VEP.

45. Contrast Sensitivity Reduction in contrast sensitivity more for higher frequencies. Improves during amblyopia therapy & useful to monitor the progress. Contrast threshold becomes normal in strabismic amblyopia when luminance levels were reduced , while the deficit persists in anisometropic amblyopia.

46. Clinical evaluation & Diagnosis Thorough clinical history Binocular red reflex test(Bruckner’s Test) Binocularity/stereo acuity testing Evaluation of visual acuity and fixation pattern Binocular alignment and ocular motility External examination Pupillary examination Thorough ocular examination including fundus examination. Cycloplegic R etinoscopy / Refraction Neutral density filter and testing for crowding phenomenon

47. Prognostic Factors in Amblyopia Positive factor Negative factor functional organic Central fixation Eccentric fixation Random dot stereopsis No random dot stereopsis Short duration Long duration Young patient, motivated Older patient, un-motivated Strabismic > Anisometropic myopia > Anisometropic hypermetropia Stimulus deprivation > Organic Degree of prognosis

48. Management of amblyopia Vision screening programs should be done. I-ARM test ( Inspection- Acuity, Red reflex & Motility) Bruckner’s red reflex test is vital for screening. Cataract:- white reflex Retinoblastoma:- yellow-white reflex Anisometropia:- unequal red reflex Strabismus:- brighter red reflex Prevention & Early detection Treatment of amblyopia

49. Treatment of Amblyopia Goals Monocular goals Eliminate eccentric fixation Eliminate eccentric localization Establish foveal fixation Establish foveal localization Improve visual acuity Binocular goals Eliminate sensory anomalies Improve sensorimotor visual skills Stabilize binocular vision in open space VS

50. Strategies to treat amblyopia Eliminate cause of visual deprivation & provision of clear retinal image in amblyopic eye. Correction of ocular dominance Perceptual training Recommended treatment should be based on:- Patient’s age Visual acuity Compliance with previous treatment Physical, social & psychological status

51. Media clearance (for clear retinal image) Childhood cataract, severe congenital ptosis & corneal opacity should be treated as early as possible to prevent stimulus deprivation amblyopia. Significant congenital cataract should be removed during 1 st 2-3 month of life. In symmetric bilateral cases , interval between operation should not be more than 1-2 weeks. Acutely developing severe traumatic cataract in child < 8-10 yrs should be removed within few weeks of injury. Refractive correction for aphakia should be given without delay.

52. Correction of ocular dominance Occlusion therapy Penalization A ctive stimulation Pleoptics Pharmacologic manipulation Choices of treatment of amblyopia are used alone or in combination Passive Therapy The patient experiences a change in visual stimulation without any conscious effort Proper refractive correction Occlusion Penalization Pharmacological manipulation

53. II) Active Therapy designed to improve visual performance by the patient’s conscious involvement in a sequence of a specific, controlled visual task that provide feedback Pleoptics Near activities Active stimulation therapy using CAM vision stimulator Syntonic phototherapy Role of perceptual learning Binocular stimulation Software-based active treatments These therapies are briefly described below with occlusion therapy in detail

54. Occlusion therapy Introduction P assive treatment Occlusion of the sound eye is the most effective treatment for amblyopia treatment by forcing the patient to use the amblyopic eye. Mainstay of treatment since 18 th century to till now. Highly effective until 8 years of age.

55. Causes progressive changes in visual functioning . Success rate 30-92 % When fixation is central: simple & effective When fixation is eccentric : <7yrs central fixation recover Older the child harder to regain central fixation

56. Mode of action Prevent fixating eye taking part in act of vision and removes inhibitory stimulus that arises from stimulation from fixating eye (non-amblyopic eye) Occlusion goals Differential diagnosis Improvement of amblyopia Elimination of suppression Awareness or elimination of diplopia Disruption of anomalous correspondence .

57. Types of occlusion

58. Total VS Partial Occlusion Total Partial (light transmission) All light is prevented from entering eye Employed in amblyopic eyes with acuity less than 6/24 Occlusion using elastoplast , gauze pad, tape, doynes rubber occluder Does not cut off the total light entering eye Degrades the vision of normal eye such that amblyopic eye gets better vision and preference Occlusion using cellophane, transparent nail polish, or a higher plus lens

59. Partial /translucent occlusion Total occlusion Given in nystagmus Amblyopia treatment

60. Conventional or Direct Inverse Occlusion of sound eye Foveal or unsteady eccentric fixation is present in amblyopic eye. Occlusion of amblyopic eye so that eccentric fixation becomes less fixed. Steady eccentric fixation Conventional vs Inverse occlusion

61. Additional points Inverse occlusion is prescribed whenever occlusion is needed but direct occlusion is intolerable to the patient. Given only if the patient is strongly resistant to direct occlusion. For example:- A strabismic patient with deep amblyopia may not be able to perform needed visual tasks with amblyopic eye . So 1 st inverse occlusion is started & changed to direct occlusion once more central fixation and improved visual acuity are obtained Inverse occlusion is started first to introduce the hesitant patient to a patching regime .

62. Full Time vs Part Time Full time Part time (Intermittent) Removed only while going to bed at night i.e all waking hours. Short time each day during close work .commonly( 1-6 hrs /day) Choice of initial Rx Given for constant strabismic amblyopes .(regardless of size of deviation) In relapses after Rx and also for maintenance Given for intermitten t strabismics or non strabismic amblyopes

63. Some exceptions to general rule Constant exotropic patients who change quickly to an intermittent strabismus with therapy ,instead of full time occlusion may need only part time occlusion or even no occlusion. Some non strabismic amblyopes with dysfunctional binocular vision may need minimal to no occlusion esp when amblyopia is treated actively with simultaneous improvement of sensorimotor processing.(Cohen 1981 ; Pickwell 1976) Intermittent strabismic or heterophoric patients with symptoms d/t inefficient binocular vision may need full time occlusion rather part time to allay binocular symptoms until BSV is improved. After recovery of symptoms, patching schedule is changed to part time.

64. Contd.. In infants & toddlers< 2 yrs of age, d/t greatest plasticity in neural processing system,to prevent occlusion amblyopia, maximum 2 hrs /day is given & passive lens,prism therapy is given together with active therapy. Occlusion in Intermittent Strabismus Time of occlusion depends on patient’s level of sensorimotor skills. Since constant occlusion may break down binocular skills only part time occlusion is recommended. When not wearing patch patient’s existing binocular skills can be reinforced through passive therapy & sensory anomalies such as suppression can be eliminated when wearing patch.

65. Contd. In intermittent strabismics,part time occlusion eliminate central or foveal suppression & treat shallow amblyopia eye after binocularity is achieved. Nonstrabismic anisometropes or intermittent strabismics with deep amblyopia requires most hours of part time general occlusion Intermittent strabismics with good peripheral sensorimotor fusion & shallow or no amblyopia requires least hours of part time general occlusion.

66. Occlusion in Constant strabismus Earlier, full time occlusion followed by a day of rest was advocated. This allows constant strabismus to regress to anomalous strabismic visual processing on free day. Nowadays, full time occlusion is prescribed initially. When intermittency is achieved in open space ,part-time occlusion is given allowing some reinforcement of binocular skills in normal activities.

67. Points on Occlusion The presence (or absence) of amblyopia and its fixation pattern determine which eye to patch The frequency of strabismus determines the amount of time that the eye is patched Alternate occlusion When equal visual acuity is present in each eye, ( e.g :- a constant alternate esotropia ) , full time occlusion is alternated daily between two eyes. The purpose of full time occlusion for strabismics with no amblyopia is to eliminate suppression and possibly disrupt anomalous correspondence.

68. Types of occluders Adhesive skin patches made of micropore (best method) Commercially available opticlude Spectacle occluder :- patched eye remains visible to observer ,diffuse light enters occluded eye from unblocked sides around the frame. Child may look from top of glasses. Good cosmesis Contact lens occluder :- Opaque center on contact lens Total blockage of form & light Good cosmesis Bandage occluder :- Total blockage of form & light Difficult to remove Greater chances of occlusion amblyopia Poor cosmesis

69. Contact lens occluder Bandage occluder Patches Micropore Spectacle occluder

70. Tie-on occluder :- Easily removed or flipped up no skin problems as bandage Clip-on occluder :-Attached to spectacle lens diffuse light enters as in spectacle occluders Occlusion lens:-Form recognition is reduced by lens induced optical blur a/k/a penalization lens or fogging lens Occlusion filters:-for the treatment of suppression & amblyopia decrease both light & form transmission neutral density or red filters are placed before normal eye & are increased in density until fixation is forced to non preferred eye

71. Tie-on occluder Clip-on occluder Occlusion lens Occlusion filter

72. Field coverage Depends on how much of the visual field to block Either the visual stimulation is blocked to whole visual field (total occlusion) or just to specific portions of the visual field (partial occlusion) (d/t presence and frequency of strabismus in a specific gaze or distance) Other consideration is whether to cover both peripheral and the central retina or just the central retina of the deviating eye.

73. Terminology Indication Visual field coverage Total Constant strabismus at all distances & gazes Full field Half- patch Constant strabismus at one distance & intermittent or heterophoria at other. Distance or near field Sector patches Incomitant strabismus.(intermittent in one field of gaze & constant in other) BSV remain in nonaffected & nonoccluded field Anomalous sensory processing can be disrupted or diplopia can be eliminated in affected field Achieve goal of binocular therapy sequence Selected gazes Field Coverage Occluders

74. Terminology Indication Visual field coverage Binasal Constant Esotropia Nasal fields( temporal retina) Bitemporal Constant exotropia Temporal fields(nasal retina) Bipatches block the visual stimulation to a specific retinal region of nonfixating eye which under unoccluded conditions would receive anomalous visual stimulation d/t turning of eye. Both trigger alternation in viewing to amblyopic eye, leading to improved visual acuity or elimination of foveal suppression. Both are alternate to total occlusion. Bitemporal occlusion disturb panoramic vision. So, not much favoured .

75. Bitemporal occlusion Binasal occlusion Sector occlusion

76. Age of patient (in yrs ) Period of occlusion (days) Direct vs Inverse Follow up after every Up to 2 2 : 1 15 days 3 3 : 1 15 days 4 4 : 1 1 month 5 5 : 1 1 month 6 or older 6 : 1 1 month A simplified schedule for initial occlusion therapy for amblyopia

77. How to go about Occlusion? Compliance is the keyword of success. Motivation of child and parents is necessary. First the near vision then distance vision starts improving. Active vision exercises by amblyopic while non- amblyopic eye is occluded Occlusion is continued till amblyopic eye has developed equal vision and equal preference of fixation May take 3-6 month If there is no improvement, on three consecutive monthly follow ups then treatment is stopped, reevaluation is done. Incomplete response to occlusion tends to be associated with anisohypermetropia & anisoastigmatism .

78. Follow up-depending on age, severity of amblyopia and compliance- to look for VA, fixation pattern and occlusion amblyopia When to stop occlusion - VA equals in both eyes - Alternation of fixation ( Repka 2008 ) When VA is stable patching may be decreased slowly Because amblyopia recurs in large no. of pts. maintenance therapy or tapering of therapy should be strongly considered

79. Disadvantages of occlusion Occlusion amblyopia Psychological distress Allergic skin rash Cosmetically inacceptable Strabismic diplopia Deviation changes

80. Occlusion amblyopia When normal or preferred eye is occluded, visual acuity may decrease & occlusion amblyopia may occur in the occluded eye. The younger the child ,faster is the acuity loss & become profound and permanent.Esp :- full time occlusion when given to infant <2yrs (critical developmental yrs ) Alternate patching is given to prevent this & shorter period of direct occlusion for younger children For the remedy of skin reactions d/t patch that is in contact with skin , hypoallergenic patch (Opticlude) can be used. Tincture benzoin may be applied to the skin before applying patch. This forms a protective layer & increase adhesiveness.

81. Strabismic diplopia Occurs d/t extended period of total occlusion without resolution of strabismus esp in older patients & those with anomalous correspondence. In pts <10 yrs , suppression may regain in few weeks after discontinuation of occlusion even after experiencing diplopia for several months when occluder is removed. d/t tendency of suppression to lessen with age Difficulty in achieving BSV in long duration strabismus

82. Deviation changes Appears to be expected progression of strabismic syndrome such as accommodative esotropia or essential esotropia . Dissociated vertical deviation may appear or previously measured primary vertical deviation may increase in size. Exodeviations may increase in size with full time or part time occlusion & later become stable. Some esotropic deviations continue to increase in size( without increase in hyperopia) with time & after months they stabilize at a given angle.

83. Occlusion removal & Maintenance occlusion treatment Occluder is not removed until comfortable ,efficient binocularity has been obtained, and patient is capable of maintaining binocular vision in open space without regressions. Most errors are made in removing the occluder too soon. Regressions from non strabismus to strabismus may occur in a relatively short time (1 to 3 months).esp. intermittent or constant strabismus Once the vision has been equalized, the maintenance occlusion should be continued till the amblyogenic , i.e up to at least 9 years of age. Maintenance by occlusion is accomplished a part-time occlusion for 2-3 hours in a day with active vision exercises at home.

84. Treatment of Anisometropic Amblyopia

85. Treatment of Strabismic Amblyopia T reatment options for strabismus 1.No treatment 2.Lens 3.Prism 4.Occlusion 5.Filters 6.Orthoptics 7.self-monitoring system 8.Medication 9.Surgery 10.Referrals

86. Amblyopia Treatment Study Paediatric Eye Disease Investigator Group( PEDIG ) is a collaborative network dedicated to facilitating multicenter clinical research in strabismus , amblyopia & other eye disorder that affect childrenn In the ATS , mild to moderate amblyopia VA in the amblyopic eye of 6/24 or better; severe amblyopia is VA in the amblyopic eye of 6/60 to 6/120

87. ATS Age of child Objective (to compare) Conclusion 3 7-17 Various treatment of amblyopia VA (6/12 to 6/120) Optical correction alone improves VA in 1/4 th of the pts. 7-12 2-6 hrs of patching with near activities or atropine,VA improved even if amblyopia has been previously treated. 13-17 2-6 hrs of patching with near activities ,VA improved even when amblyopia has not been treated previously.

88. ATS Age of child Objective (to compare) Conclusion 4 <7 yrs Daily vs weekend atropine for strabismic or anisometropic amblyopes with VA 6/12 to 6/24 Daily = weekend 5 3-7 yrs Effectiveness of refractive correction alone for untreated anisometropic amblyopia Resolution occurs in at least 1/3 rd of pts. VA improved by >= 2 lines in 77% 5(2) 3-7 yrs 2hrs patching ( with near activity) vs spectacle alone in mod to severe amblyopes Patching >> spectacle correction alone

89. ATS Age of child Objective (To compare) Conclusion 13 3-7 yrs. VA improvement in children with strabismic & combined strabismic-anisometropic amblyopia treated with optical correction alone Treatment effect was greater for strabismic than combined mechanism amblyopia. 15 3-8 yrs. Increasing patching for 2-6 hrs. with VA(20/50-20/400) When VA stops improving with 2 hrs. of patching, increasing patching to 6 hrs. result in VA improvement.

90. Practical examples of occlusion Three factors govern occlusion schedule There is no hard & fast rule to prescribe occlusion schedule .

91. Some points Direct occlusion is given age hrs /day. i.e 4yrs:- 4hrs/day > 6 yrs :- 6hrs/day VA is plays most important rule. No. of lines difference in VA:- same ratio in direct occlusion . eg :- 3 lines difference= 3:1 ratio When lens are prescribed for the first time , it is advisable to wait for 4 weeks & reassess frequency of strabismus before determing appropriate occlusion plan.

92. Age RE LE Ratio (RE:LE) Time /day 4 yrs 6/6 with plano 6/18 with +2.00 Dsph 3:1 4hrs/day 5 yrs 6/60 with +5.00 Dsph 6/18 with +2.00 Dsph 1:3 5hrs/day 7 yrs 6/6 with plano 6/60 with +3.00 Dsph 6:1 6hrs/day

93. Age RE LE Ratio (RE:LE) Time ( hrs /day) 4 yrs 6/9 with +1.00 Dsph 6/12 with +2.00 Dsph 2:1 4 hrs /day 8 yrs 6/18 with +3.00 Dsph 6/18 with +3.00 Dsph 1:1 6 hrs /day 6 yrs 6/18 with +1.50/-3.00*180 6/60 with +1.50/-5.00*180 3:1 6hrs/day

94. Age RE LE Ratio (RE:LE) Time ( hrs /day) 7 yrs 6/6 with plano 5/60 with +6.00 Dsph 6: free 6hrs/day 5 yrs 6/18 with +3.00 Dsph 5/60 with +7.00 Dsph < 4:1 (3:1) given 5 hrs /day (close f/ups) 2 yrs Only LE is patched initially. 2hrs/day. (close f/ups) RE constant esotropia . VA Couldn’t be assessed.

95. Refractive error correction • Improves VA in 25-33% of patients with anisometropic amblyopia and also in strabismic amblyopia • Cycloplegic refraction followed by adequate optical correction • ATS 5 concluded that amblyopia improved with optical correction in 77% and resolved in 27% • Chen et al (AJO 2007) concluded that penalization and occlusion is required only if the child doesn’t improve with glasses for four months • In general eye glasses are well tolerated by children especially when there is improvement in visual function.

96. When to prescribe??

97. Other Treatment modalities Besides occlusion therapy; Penalization Pleoptics Active vision therapy using CAM vision stimulator Pharmacological manipulation Software based active treatments plays important role in amblyopia treatment.

98. Refractive error correction Penalization

99. Penalization Literally means to punish or inhibit. Therapeutic technique performed by optically defocusing the eye with better vision by using cycloplegia or altering the eye glass lens. Force the amblyopic eye to a greater use for distance, near or both ny penalizing the sound eye for near, distance or both. Indications No compliance for occlusion Mild degrees of amblyopia Maintainence after occlusion Anisometropic amblyopia Unless penalisation decreases the VA of dominant eye below the amblyopic eye this form of treatment is not adviced

100. Advantages : Cheap, better compliance Disadvantages : Side effects of drugs - Risk of occlusion amblyopia - Systemic absorption Methods of penalisation Near penalization Distance penalization Fixing eye is atropinized & fully corrected for distance. Fixing eye is atropinized & overcorrected for near. Amblyopic eye is overcorrected with +2 to +3 D for near. Amblyopic eye is fully corrected for distance. Total penalization:- fixing eye is atropinized & under corrected by 4 to 5 D, amblyopic eye is fully corrected

101. Pleoptics Involves active stimulation of fovea to overcome eccentric fixation & improves VA The peripheral retina including the eccentrically fixing area around the fovea is dazzled. After lights are turned off, fovea functions better because the surrounding retinal area is in a state of hypo function Only indication is cooperative and intelligent child older than 6yrs having eccentric fixation. This can be followed by direct stimulation of fovea by pleoptophore ( Bangerter’s method) or indirectly by producing after image (Cupper’s method)

102. (Active stimulation therapy using CAM vision stimulator) Non amblyopic eye is occluded Amblyopic eye is stimulated for 7 mins by slowly rotating (at about 1 revolution per min) high contrast square wave grating of different spatial frequencies The treatment is carried out once in a week for 3 to 4 weeks The sound eye remains open between the weekly treatment sessions. Assumption that rotating grating provides specific stimulation for cortical neurons

103. Pharmacological Manipulation Levodopa & citicoline are the most extensively studied drugs Studies indicate that plasticity of visual system during the sensitive period is dependent on input from non-adrenergic neurons Levodopa , precursor for the catecholamine dopamine, a neurotransmitter, known to influence visual system at retina and cortical level Speeds up recovery of visual functions, improves compliance, reduces cost & duration of treatment. Nowadays, Catecholamine based medical treatment, Citicholine has been demonstrated to improve vision in amblyopic eyes.

104. Pleoptophore CAM vision stimulator (Active Vision Therapy) Pharmacological manipulation

105. Summary The clinical features and laboratory findings in eyes with amblyopia permit certain conclusions for understanding the nature of the processes underlying amblyopia and its treatment. Decreased visual acuity, although clinically the most tangible defect, is but one of the many disturbances associated with amblyopia regardless of its etiology Basic amblyogenic mechanisms are the same even though their contribution to each type of amblyopia varies Most of the active therapy methods have good results when used together with patching therapy Early detection & Screening programs should be done to prevent amblyopia Amblyopia is still an unsolved problem, the best modality of treatment is still to be explored in future

106. REFERENCES Binocular Vision & Ocular Motility ; Gunter K. Von Noorden Theory and practice of Squint & Orthoptics ; A.K Khurana Management of strabismus & Amblyopia ; John A. pratt -Johnson Clinical management of Strabismus ; Elizabeth E. Caloroso Previous Presentations Internet