The document discusses amblyopia, including its definition, causes, types, visual development milestones, diagnosis, and abnormalities found in amblyopic eyes. It provides details on epidemiology, pathophysiology, classification, and visual characteristics of amblyopia such as crowding phenomenon, eccentric fixation, and reduced contrast sensitivity. The document also outlines methods for diagnosing amblyopia in pre-verbal children through tests of fixation, red reflex, and induced tropia.

1. Dr Bhawana Khanal
2nd year Resident
Tilganga Institute of Ophthalmology

2. Introduction
Epidemiology
Pathophysiology
Visual Developmental Milestones
Classification
Diagnosis

3.  AMBLYOPIA: Dullness in vision
 Ambly - dull, ops – vision
“Condition in which the observer sees nothing and the patient sees
very little”- Von Graefe
Dr. Gunter Von Norden ‘‘Decrease in visual acuity caused by abnormal binocular
interaction occurring in one or both eyes as a result of patterned visual deprivation
during critical period ,for which no cause can be detected during physical
examination of the eye(s) and which in appropriate cases is reversible by
therapeutic measures’’

4.  Amblyopia is caused by abnormal visual stimulation during visual
development, resulting in abnormalities in the visual centers of the brain.
 There are two basic forms of abnormal stimulation: pattern distortion
(i.e., blurred retinal image) and cortical suppression (i.e., constant
suppression of one eye).1
• Amblyopia is defined as abnormal visual development that is clinically
defined as a reduction of best corrected Snellen acuity to less than 6/9
(20/30) in one eye or a two-line difference between the two eyes, with no
visible signs of eye disease.
1.Handbook of Pediatric Strabismus and Amblyopia.
Kenneth W. Wright

5. There are few studies on school going children which shows the prevalence
of amblyopia to be 0.9 to 1.8% 2
Amblyopia and amblyopia treatment study
Shrestha UD,* Adhikari S 2
Prevalence of amblyopia in Nepal: 0.7 - 1.8% 3
Type of Amblyopia Percentage
Anisometropia 53%
Ametropia 29%
Strabismic 14%
Mixed 3%
Stimulus deprivation 1%
Yuddha D. Sapkota, et al (2008) The Prevalence of Visual Impairment in School Children of Upper-
Middle Socioeconomic Status in Kathmandu, Ophthalmic Epidemiology,
Sapkota et al Prevalence of amblyopia and patterns of refractive error in the amblyopic children of
a tertiary eye care center of Nepal3

6.  Amblyopia accounts for the leading cause of visual impairment and blindness in
children in Nepal4
-4Causes of visual impairment and blindness in
children in three ecological regions of nepal:
nepal Pediatric Ocular Diseases study 2015
S Adhikari, MK Shrestha, K Adhikari

7.  Changes have been found in the lateral geniculate
nucleus (LGN) and visual cortex

8.  LGN in Thalamus is a layered
structure with each layer receiving
input from a hemiretina of only one
eye
 LGN are subdivided into
Magnocellular (layer 1 and 2) and
Parvocellular (Layer 3,4,5 and 6)
subdivisions.
 Cell shrinkage has been noted to
occur in the parvocellular layers,
which receives input from the
amblyopic eye

9.  Ocular dominance columns in the striate cortex are damaged as a result of a
unilateral blurred image during early development.
 cells present in the visual cortex can lose their ability to respond to stimulation
of 1 or both eyes, and the cells that remain responsive show significant functional
deficiencies.

10.  Amblyopia is associated with histologic and electro- physiologic
abnormalities in the visual cortex.
 Hubel and Wiesel pioneered methods of studying the effects of
changing visual experience in kittens and other animals by suturing
eyelids of one eye closed.
 The layers of the LGN corresponding to input from the amblyopic eye
along with ocular dominance columns have been shown to be
markedly attenuated.
Harley’s Pediatric ophthalmology 6th edition

11. VISUAL DEVELOPMENT
-Current Understanding of What Infants See-
Lea Hyvarinen
Crucial Milestones
Ability to make
eye contact
Social
Smile
Awareness of
Hands
Ability to watch
hand movements
Eye positioned
straight
Goal directed
hand movements
Recognition
of familiar
face
Pictures in
books
and
picking up
certain objects

12. Crucial Milestones
1. Stable eye contact
Age
Birth – 8 weeks
Maintains stable eye
contact when awake
and alert.
Stable- holding eye
contact

13. Crucial Milestones
2.Social smile
Age
2nd - 3rd month
Importance:
Tells us that the brain and visual system is developing
Accommodation is developing
Can see clearly at varying distances

14. Crucial Milestones
3.Awareness of hands
Age
3rd – 4th month Awareness of hands
and exploration of
mouth with hands
Importance:
Hand eye co-ordination
Visual conception

15. Crucial Milestones
4.Watching hand movements
Age
5th month Keen watching of
hands of other people
and begin to copy
those
Importance:
Beginning the process of learning by looking at others
and imitating

16. Crucial Milestones
5. Straight eyes
Age
6th month Eyes straight
not crossing or
drifting
Importance:
Eyes must be straight for good binocular visual
development

17. Crucial Milestones
6. Goal directed hand movements
Age
6th – 7th months
Goal directed hand
arm movement
Importance:
Reaching for desired object leads to goal directed
behavior and shows desire, interest and curiosity –
critical elements for learning
If baby is not reaching for objects maybe baby cannot
see the objects.

18. Crucial Milestones
7.Recognition of family / care giver
Age
6th – 7th months
Recognizing care giver
Importance:
Indicator of social and visual development
Red Flag- wants to be constantly carried
Possibly cannot see the face of caregiver so clings to
parent for support

19. Crucial Milestones
8. Pictures, picking objects
Age
9th-12th month
Points to individuals
turns pages and
points to pictures in
books.
Importance:
Continuing the development of hand eye co-ordination
Vision is sharp and clear

20. Milestones …
Visual acuity matches adult acuity levels with
adult in pediatric acuity cards
18th month of age
3 years of age Matches adult values on Snellen acuity
Contrast sensitivity develops
5-6 years of age Stereoacuity fully develops

21. • birth to 3-5 years of age
The period of
development of visual
acuity
• a few months to 7 or 8 years of age
The period during
which deprivation
may cause amblyopia
• time of deprivation to the teenaged
years or even into the adult years
The period during
which recovery from
amblyopia can be
obtained

23. Classification
Amblyopia
Functional
amblyopia
(potentially
reversible)
Organic
amblyopia
( irreversible)
Harley’s Pediatric ophthalmology 6th
edition

24. 1. Strabismic
2. Refractive
1. Anisometropic
2. Isoametropic
3. Meridional
3. Form deprivation
4. Reverse

25. Strabismic
Results from abnormal binocular interaction that
occurs when the visual axis of fellow eyes are
misaligned.
This abnormal interaction causes the foveae of
the two eyes to be presented with different
images
Results in Diplopia and visual confusion
Harley’s Pediatric ophthalmology 6th edition

26. Cortical suppression of image from deviating eye
Favors fixation strongly with one eye
Abnormal binocular interaction
Strabismus
inhibition of the retinostriate pathways of visual input originating in
the fovea and peripheral retina of the deviating eye

27.  Refractive amblyopia occurs due to
uncorrected refractive error leading to
visual blur.
 In anisometropic amblyopia, dissimilar
refractive errors in the 2 eyes cause 1
retinal image to be chronically
defocused.
 Levels of anisometropia that commonly
lead to amblyopia are greater than 1.50
diopters (D) of anisohyperopia, 2.00 D
of anisoastigmatism, and 3.00 D of
anisomyopia

28. Amblyopia
Impaired stimulation in
development of visual
pathway in weaker eye
Refractive error
Image blur
Inter ocular inhibition
of the defocused
image

29. Isoametropic amblyopia
Isoametropic amblyopia (bilateral ametropic amblyopia) is bilaterally
decreased visual acuity resulting from chronically defocused retinal images,
which are due to similarly large uncorrected refractive errors in both eyes.
BCSC 2021-2022 06.Pediatric Ophthalmology and Strabismus

30. Refractive amblyogenic factors

31. Meridional
• Uncorrected astigmatism during
early development can result in
Meridional Amblyopia.6
• Bilateral high astigmatism may
cause loss of resolving ability
specific to the chronically
blurred meridians
6. Amblyopia and amblyopia treatment study
Shrestha UD, Adhikari S

32. Deprivation
 visual deprivation amblyopia is due to an eye
abnormality that obstructs the visual axis or
other wise interferes with central vision.
 Amblyopia results from disuse or under
stimulation of the retina due to lack of
pattern stimulation to the retina
• The most common cause : congenital or early-
acquired cataract
• Other causes : Congenital ptosis, periocular
lesions obstructing the visual axis, corneal
opacities, congenital macular scars
BCSC 2021-2022 06.Pediatric Ophthalmology and
Strabismus

33. Reverse Amblyopia
• Iatrogenic interference with vision in childhood
(therapeutic occlusion or cycloplegia)
• Severe amblyopia has been reported after as little
as 1 week of unilateral patching in children under
2 years of age following minor eyelid surgery.7
• However with the newer concept of part time
occlusion, reverse amblyopia does not occur in
the normal eye
7Abrahamsson M, Sjostrand J. Natural history of infantile
anisometropia. Br J Ophthalmol 1996;80:860-3.

34. Grading of Amblyopia
Types of amblyopia according to severity as defined in ATS:
• Mild to Moderate: visual acuity in the amblyopic eye between 20/80
(6/24 metric scale) or better
• Severe: visual acuity in the amblyopic eye between 20/100 and 20/400.
8 (6/36- 6/120 metric scale)
8. Amblyopia and amblyopia treatment study
Shrestha UD, Adhikari S

35. Amblyopic Vision
Includes the following:
 Crowding phenomenon
 Neutral density filter effect
 Eccentric fixation
Handbook of Pediatric Strabismus and Amblyopia.
Kenneth W. Wright

36. Crowding phenomenon
 The crowding phenomenon relates to the fact that
patients with amblyopia have better visual acuity
reading single optotype than reading multiple
optotypes in a row (linear optotypes).
 Often, patients with amblyopia will perform 1 or 2
Snellen lines better when presented with single
optotypes versus linear optotypes.
 Crowding bars are often used around a single
optotype to provide a more sensitive test for
amblyopia.
Handbook of Pediatric Strabismus and Amblyopia.
Kenneth W. Wright

37. Crowding phenomenon

38. Neutral density filter effect
 A neutral density filter reduces overall luminance
without inducing a color change.
 Decreased luminance of the visual target results in
diminished central acuity in normal eyes
 Decreased illumination of visual targets has less of an
effect on amblyopic eyes because they are not using
central acuity.
Handbook of Pediatric Strabismus and Amblyopia.
Kenneth W. Wright

39. Eccentric fixation sense
 All amblyopes have some degree of extrafoveal fixation.
 Patients with eccentric fixation appear to be looking to the
side, not directly at the fixation target.
 They have poor smooth pursuits, so they do not accurately
follow a moving target.
-Handbook of Pediatric Strabismus and Amblyopia.Kenneth W. Wright

40. Eccentric fixation sense
-Handbook of Pediatric Strabismus
and Amblyopia.Kenneth W. Wright

41. Contrast Sensitivity
Strabismic and anisometropic amblyopic eyes have marked
losses of threshold contrast sensitivity, especially at higher
spatial frequencies; this loss increases with the severity of
amblyopia. 10
10. Amblyopia and amblyopia treatment study
Shrestha UD, Adhikari S

42. Binocular function
• Amblyopic eye is associated with changes in binocular function
or stereopsis
• Stereopsis will never be obtained unless amblyopia is treated,
the eyes are aligned, and binocular fusion and function are
achieved before the critical period for stereopsis ends (before
24 months).

44. History
Examination
Visual acuity( agewise)
EOM
Pupillary response
Color vision
Contrast sensitivity
Binocular function and stereopsis
Squint evaluation

45. History
History
Family History
Birth history
Prenatal:
toxin/infections
,genetic,
metabolic
Perinatal :
APGAR
Birth Weight
Prematurity
Postnatal :
Motor
sensory
visual
Congenital
cataract
RB,
Glaucoma,
strabismus
Vaccination
status ,
school
performance

46. Fixation and following
Assessed using bright attention-
grabbing targets (a face is often
best). This method indicates whether
the infant is visually alert and is of
particular value in a child suspected
of being blind.

47. Fixation behavior
used to establish unilateral preference if a manifest squint is present.
Fixation is promoted in the squinting eye by occluding the dominant eye
while the child fixates a target of interest (preferably incorporating a light).
Fixation is then graded as central or non-central and steady or unsteady (the
corneal reflection can be observed)

48. Visual acuity testing in pre-verbal children
Fixation behavior
The other eye is then uncovered and the ability to maintain
fixation is observed.
○ If fixation immediately returns to the uncovered eye, then VA is
probably impaired.
○ If fixation is maintained through a blink, then VA is
probably good.
○ If the patient alternates fixation, then the two eyes
probably have equal vision.
Kanski’s clinical ophthalmology 9th edition

49. DIAGNOSING AMBLYOPIA
-Handbook of Pediatric Strabismus and Amblyopia.Kenneth W. Wright
Fixation Testing

50. DIAGNOSING AMBLYOPIA
Fixation Testing
-Handbook of Pediatric Strabismus and Amblyopia.Kenneth W. Wright

51. Central Steady Maintenance
C: Central Corneal Light reflex with fixation
under uniocular conditions
S: Steadiness of fixation when the target is
stationary and with slow movement under
monocular conditions
M: The ability to maintain fixation and
alignment of each eye under binocular
viewing conditions
Kanski’s clinical ophthalmology 9th edition

52. Menace Reflex :
Closing of eyelids on rapid approaching
of an object near the eyes.

53. Visual acuity testing in pre-verbal children
 Aka Red Reflex test
 Used for screening of :
Amblyopia
Strabismus
Refractive error
Media opacities
Bruckner’s test:

54.  Check for:
Intensity of red reflex
Position of light reflex
Size of pupil
Comparison with fellow eye: the reflexes should be mirror image of
each other

55. Bruckner’s test:

56. Bruckner’s test:

57. Bruckner’s test:

61. The Induced tropia test
In the absence of strabismus, fixation preference testing done with a
vertical base up or base down 10 prism diopter (PD) lens to create
diplopia has been shown to be effective in detecting about a three-
line visual acuity difference between the eyes and identifying
moderate to severe amblyopia
Kanski’s clinical ophthalmology 9th edition

62. (A) Vertical prism is placed in front of one eye to
identify which eye is fixing, and therefore fixation
preference can be determined. (A) One can identify that
the right eye is fixing because the right eye is in primary
position and the patient is ignoring the vertical
displaced image in the left eye. (B) Patient is still fixing
with the right eye. Both eyes shift upward because the
right eye is viewing through the prism. This is a base-
down prism, so the eyes move up.

63. Rotation test
Gross qualitative test of the ability of an infant to
fixate with both eyes open. The test is performed as
follows:
○ The examiner holds the child facing him or her and rotates briskly
through 360°.
○ If vision is normal, the eyes will deviate in the direction of rotation under
the influence of the vestibulo-ocular response. The eyes flick back to the
primary position to produce a rotational nystagmus.
○ When rotation stops, nystagmus is briefly observed in the opposite
direction for 1–2 seconds and should then cease due to suppression of post-
rotatory nystagmus by fixation.
○ If vision is severely impaired, the post-rotation nystagmus does not stop
as quickly when rotation ceases because the vestibulo-ocular response is not
blocked by visual feedback.
Kanski’s clinical ophthalmology 9th edition

64. Teller acuity
Lea grating acuity
Cardiff acuity
the child’s response to a visual stimulus is observed to
assess visual acuity.

65. Preferential looking
Teller Acuity Cards can be used to measure visual acuity in a preverbal child. If the
pattern is visible to the child, the eyes gaze toward the grating; otherwise, the
stripes blend into the gray background.

66. Preferential looking
Keeler acuity
cards

67. Preferential looking

68. Preferential looking

70. Testing in verbal children
Crowded Kay picture
Sonksen crowded tests
• Lea Symbols chart
•Broken Wheel acuity cards
• HOTV test.

71. Testing in verbal children
Crowded Kay picture

72. Testing in verbal children
LEA Symbols chart

73. Testing in verbal children
Broken Wheel acuity cards

74. Testing in verbal children
HOTV test

75. Visual Acuity Testing
When evaluating amblyopia, linear acuity
is more desirable than single optotype
presentation because single optotype
presentation underestimates the degree of
amblyopia.

77. VISION SCREENING
Vision screening examinations should start at birth and continue as
part of routine checkups for primary care physicians. The acronym I-
ARM (inspection—acuity, red reflex, and motility) can be a helpful
reminder of the essential parts of a pediatric screening examination.
-Handbook of Pediatric Strabismus and Amblyopia.Kenneth W. Wright

78. -Handbook of Pediatric Strabismus and Amblyopia.Kenneth W. Wright

79. References
• Handbook of Pediatric Strabismus and Amblyopia.
Kenneth W. Wright
• Amblyopia and amblyopia treatment study .Shrestha UD, Adhikari S
• Binocular vision and ocular motility , Theory of management of
strabismus by Gunter K,Von Noorden:1996
• Harley’s Pediatric Ophthalmology 6th edition
• Current Understanding of What Infants See-Lea Hyvarinen’s Review
article
• Kanski’s clinical ophthalmology 9th edition
• BCSC 2021-2022 Pediatric Ophthalmology and Strabismus

80. THANK YOU