7. Mechanism
Basically visual system is not being
used & incompatable in its
developemental period due to
⢠Abnormal binocular interaction
⢠foveal pattern deprivation
20. ⢠The ERG of amblyopic eyes are normal. In
contrast, VER reduced in amplitude
⢠fMRI
⢠Positron emission tomography(PET)
⢠Magnetencephalography(MEG)
Reduced levels of activation in the visual
cortex
25. Pattern deprivation is the
most severe form of visual
deprivation.
Light reaches the retina, but
all spatial detail (high and
low spatial frequencies) is
lost.
The most common cause of
pattern deprivation is
infantile cataract
⢠corneal opacity.ptosis
medial opacities
⢠blepharospasm. obstuction
of visual axis.
26. Research with monkeys has established
two of the basic requirements for
successful treatment and prevention of
amblyopia, in cases of form
deprivation:
⢠surgery before the age of 4 months
⢠occlusion
27. Strabismic amblyopia
⢠Most common.
Strabismus can lead
to amblyopia since
the eyes receive
uncorrelated retinal
images.
⢠The result is arrested
development of visual
function (including
visual acuity) and
amblyopia.
28. ⢠Commonly seen
in non alternating
ET.
⢠Neutral density
filter effect
⢠Eccentric fixation
29. Optical defocus
⢠Next common.
⢠Optical defocus is less damaging to
visual development than pattern
deprivation as defocus removes
high spatial frequencies (fine detail,
sharp edges, etc.) from the retinal
image, but low spatial frequencies
(large shapes) remain.
30. The most common cause of this kind
of amblyopia is anisometropia.
Ametropia ..Bil Amb
⢠very high myopia, >6D
⢠more hyperopic eye.>4D
⢠Astigmatism >2D
31. ⢠To prevent amblyopia is to correct the
refractive error as early as possible;
⢠> +2.50 diopters of hyperopia or
astigmatism, 75% amblyopic without
treatment, but only 25% developed
amblyopia who were corrected
33. Organic /relative
⢠Organic cause with amblyogenic
factors like anomalies of retina,medial
opacities ,optic nerve
⢠Improve with patching
34. Diagnosis
⢠Reduced V.A uni or Bil.
⢠Amblyogenic factors like vision
deprivation, Strabismus, optical
defocus
⢠Alternative causes for visual loss have
to be ruled out
45. Crowding
phenomenon
⢠Single letter acuity better than line acuity
⢠This is due to âspatial interference effects
seeing a visual contour that is produced
by a near by adjacent contour
⢠For followup..single acuity improves
faster than line
⢠If line acuity not achieved regression is
high on discontinuation of therapy
⢠typically found in strabismic amblyopia
[Bonneh, Y., Sagi, D., & Polat, U. (2004a)
46. ⢠A pattern can be difficult to identify
when surrounded by a âcrowdâ of
flanking patterns, a phenomenon called
âcrowdingâ (Stuart & Burian, 1962). A
briefly flashed pattern can be difficult to
identify when surrounded in time
(before and/or after) by other patterns (
Breitmeyer, 1984), forming a âtemporal
crowdingâ situation
47. ⢠This reduction in acuity is due to an
interference effect by the flanking
patterns, and it depends on their
distance from the central pattern . The
critical distance for crowding increases
with eccentricity, extending as far as
half the retinal eccentricity of the target
and at the periphery it appears to be
independent of the size of the target
48. Three tasks.
Levi D M et al. J Vis 2007;7:21
Š2007 by Association for Research in Vision and Ophthalmology
49. The central field of amblyopes is similar to
the normal periphery in many respects (e.g.,
Levi, 1991; Levi & Klein, 1985, Levi et al.,
1985; Levi et al., 1994a, 1994b, but see Levi
et al., 2002a). The similarity suggests that
amblyopia (or at least some aspects of
amblyopia) might be explained on the basis
of an âequivalent eccentricityâ, that is, an
eccentricity in the normal periphery where
performance is equivalent to that of the
amblyopic fovea.
50. Neutral density filters
⢠Does not cause reduction in VA..in
StrabismicAmb
⢠More specific
⢠Differentiate organic from functional
Amb & aniso metropic
51. ⢠Contrast sensitivity reduced
⢠Eccentric fixation
⢠increase in the foveal thickness of
amblyopic eyes along with a reduced
foveal pit in the horizontal, but not
vertical, meridian.[3]
⢠Bruce A, Pacey IE, Bradbury JA, Scally AJ, Barrett BT. Bilateral Changes in Foveal Structure in Individuals with Amblyopia. Ophthalmology.
Sep 29 2012;[Medline].
â˘
58. Spects
⢠Accurate optical correction
⢠Never cut the cylinder
⢠Deduct hyperopic power equally for
both eyes
⢠Objective measurement are more imp.
⢠Prompt correction of aphakia
59. Optical correction
⢠Acc.ET with amblyoia ::Full + correction
⢠Non acc ET:: <full +
⢠Acc. is symmetrical. Fixing eye
determines amount of acc.Any
decrease in + must be symmetrical
61. Optical correction
⢠> 1.50 d sphere or 1.00 cylinder wait
for spects before starting patching
Anisometropia
⢠Knapps rule..aniseikonia will not occur
if anisometropia is axial
62. Occlusion
⢠Widely recognised ,time tested method.
⢠Neither substitute nor shortcut.
⢠Occlusion with adhesive skin patch is the
most effective means of therapy
⢠Near vision exercises will hasten
improvement
63.
64.
65. ⢠Occlusion Dose Monitor electronically measures compliance
with the prescribed hours of occlusion so that visual
improvement may be correlated with the actual time patched.
67. ⢠At any age
⢠Fulltime or part time
⢠Total coverage of eye
⢠No fogging or rubber
occluders
⢠Re-examined at
regular intervals
Younger the patient
greater risk of
occlusion amb
69. Techniques of active
treatment
⢠Mallet Intermittent photic stimulation
⢠Red filter over amblopic eye
⢠Euthyscope,Haidingers brushes- foveal fixation
⢠Chequer board light box with flashes
⢠Dotting: child fills series of circles
⢠Colouring pictures within lines,Video games
72. When to stop occlusion
⢠V.A becomes equal
⢠Fixation is alternating
⢠No change in V.A. even after 3months
73. Prognostic considerations
⢠Younger the child better the prognosis
⢠Most effective in strabismic Amb.
⢠Myopic better than Hyperopic
⢠Fulltime occlusion
74. ⢠Central fixation better than eccentric
⢠Near vision exercises will hasten
improvement
⢠Better after surgical allighnment
75. Occlusion after 9 yrs Encouraging in
⢠anisometropic,
⢠Ametropic
⢠after squint correction
76. ⢠One study by Levartovsky et al showed
deterioration in 75% of children with
anisometropia of 1.75 diopters or more
after occlusion therapy.[29]
Recidivism
can occur, even several years after the
initial treatment period, and is as high
as 53% after 3 years.
78. PENALISATION
⢠Atropine 1% drops one drop instilled once
daily by the mother in the sound eye
⢠Cosmetically acceptable,good compliance
⢠Not as effective as patch
⢠Useful in moderate and not dense
amblyopia
⢠NIH- randomised clinical trial: succes rate
patch 79%, penalisation 74%
79. ⢠OPTICAL PENALISATION
Can be achieved by over correction with
+3DS equivalent to decrease dist vision of
better eye
EW CONTACT LENS used in infants
80. PHARMOCOLOGICAL
THERAPY
⢠Levadopa and Carbidopa are used
⢠Levadopa is a precursor of dopamine which
is nuerotransmitter at retinal level and also in
the visual cortex
⢠Carbidopa is a peripheral decarboxylase
inhibitor that prevents breakdown of
levadopa
⢠L- dopa administration showed changes in b
wave in ERG, oscillatory potentials, implicit
time of VEP
81. Prevention
⢠Screening for V.A ,Corneal reflex test,
refraction,&Stereopsis
⢠Team effort: parents,teachers,family
physician,paediatrician,ophthalmologist
⢠Surgical dressing.
⢠Hyphema
⢠Lid edema
82. New ideas
Perceptual learning >9yrs
⢠Gabor signal gratings.set of 3
contrasting dark &light ovals that form
Basic unit of visual perception
83. Implantable collamer lens
(ICL)
⢠Refractive Amblyopia not respondinfg
to patching with spects or contacts
Reversibility
High errors
Thin corneas
84. Recent studies
Amblyopia Treatment Study(ATS)
by Paed.Eye Disease Investgator
Group (PEDIG)
ATS1..
⢠Penalistion vs occlusion..moderate
Amb..Results showed similar response
after 6 months.In occlusion results are
faster.near vision activities must
85. ATS2⌠Dosage of occlusion
⢠2hrs/day vs 6hrs/day for mod.Amb
⢠6hrs/day vs fulltime occlusion in severe
Amb
⢠After 6 mths effect same
86. ATS 3
⢠Regular treatment for7-12 yrsand 13-
17yrs is encouraging
ATS 4
⢠Weekend atropine vs daily atropine for
mod. Amb
Amb treatment advice will be consistant
around the world and evidence based.
87. ⢠After controlling baseline refractive error,&
alignment a decrease in hyperopia of
amblyopic eye . This shift toward
emmetropia was associated with ocular
alignment, supporting the idea that better
motor and sensory fusion promote
emmetropization.
⢠Marjean T. Kulp,1
Nicole C. Foster,2
Jonathan M. Holmes,3
Raymond T. Kraker,2
B. Michele Melia,2
Michael X. Repka,4
and D. Robbins Tien5
, on behalf of the
Pediatric Eye Disease Investigator Group
88. ⢠6 hours daily rather than 2 hours yield
greater improvement at 10 weeks. intense
patching protocol suggests that this strategy
is worth considering in children with residual
amblyopia.
⢠stable residual amblyopia after 12 weeks of
2-hour patching, an increase to 6-hour
patching c bring further improvement
⢠to achieve the best result in the shortest
amount of time, it may be worthwhile to
bypass 2-hour patching and start with 6-hour
patching instead
89. Trial of Patching vs Acupuncture for
Anisometropic Amblyopia in Children
Aged 7 to 12 Years
Jianhao Zhao, MD; Dennis S. C. Lam, MD, FRCOphth; Li Jia Chen, PhD; Yunxiu Wang, BMed; Chongren Zheng, DEpid; Qiaoer
Lin, DN; Srinivas K. Rao, FRCS; Dorothy S. P. Fan, FRCS; Mingzhi Zhang, MD; Ping Chung Leung, MD; Robert Ritch, MD,
FRCOphthArch Ophthalmol. 2010;128(12):1510-1517. doi:10.1001/archophthalmol.2010.306.
90. Most cases of amblyopia are
reversible if detected and treated
early,
Thank u
Thank u
Hinweis der Redaktion
Three tasks. While fixating a mark, the observer is asked to identify one isolated letter (left) or one letter surrounded by random flanking letters (middle) or to read a stream of words (e.g., âgarage six blocks away and whenâ), presented one after another (RSVP), each surrounded by new random flanking letters (right). In each case, we use an adaptive procedure to determine the critical size (covaried with spacing) for 50% correct identification. It is of no consequence, but the actual stimuli differed from this illustration in using different fixation marks and using bright (instead of dark) letters for the two letter-identification tasks (see Methods). Our measurement of flanked and unflanked acuity to test for crowding is computerized, but is otherwise similar to older printed tests, such as Tommila&apos;s (1972) flanked and unflanked tumbling E charts and the Cambridge Crowding Cards (Atkinson, Anker, Evans, Hall, & Pimm-Smith, 1988).