2. INTRODUCTION
ď˝What is amblyopia?
ď˝What are the types of amblyopia?
ď˝What causes of amblyopia?
ď˝Classification of amblyopia?
ď˝What are the sign and symptoms of
amblyopia?
3. What is amblyopia?
⢠âLazy eyeâ
⢠A unilateral/bilateral condition
⢠The best corrected VA is poorer than 6/9 in
absence of the ocular media and fundus
anomalies or ocular disease.
⢠Prevalence:- occurs about 1 in 25 children develop some
degree of amblyopia.
⢠High risk of becoming blind.
8. What causes of amblyopia?
⢠There are four major causes of amblyopia which are:
ďśUnequal/Poor visual acuity
ďUnequal refractive error (Anisometropia)
ďBilateral equal high refractive errors (isoametropia)
ďUncorrected moderate/high astigmatism
ďśStrabismus/Misaligned Eyes
ďś Blockage or deprivation
ďś Toxic
10. Unequal/Poor visual acuity due to:
Uncorrected high myopia Uncorrected high hyperopia
2) Bilateral equal high refractive errors (isoametropia)
More than -6.00D to -9.00D More than +4.00D
Blurred image form onto the retina
because ray of light focused in front of
the retina.
Blurred image form onto the retina
because ray of light focused at the
back of retina.
11. Unequal/Poor visual acuity due to:
3) Uncorrected moderate/high astigmatism
Meridional amblyopia is a mild condition in which lines are seen less clearly
at some orientations than others after full refractive correction.
12. Unequal/Poor visual acuity due to:
3) Uncorrected moderate/high astigmatism
A Compound myopic
B Simple myopic
C Mixed astigmatism
D Simple hyperopic
E Compound hyperopic
Clinical types of astigmatism which can lead to meridonal astigmatism if it is not
corrected within plastic age.
15. Blockage or deprivation
an opacity in the line of vision-e.g: cataract
Due to: -Congenital/traumatic cataract
-Congenital ptosis
-Congenital/traumatic corneal opacities.
16. Toxic ⢠Drugs -
chloramphenicol,
digoxin, ethambuto
l
⢠Tobacco- piped
smoker, excessive
smoker
⢠Alcohol- alcoholic
⢠Chemicals- Lead,
methanol
⢠Nutritional
disorders - such as
Strachan's
syndrome, lack of
vitamin A and zinc.
The optic nerve head in acquired optic
neuropathies
17. What are the types of amblyopia?
⢠The nature of amblyopia differs depending
on the cause:-
Refractive amblyopia
Anisometropic amblyopia
Meridonial amblyopia
Strabismic amblyopia
Visual deprivation amblyopia
Toxic amblyopia
18. Classification of amblyopia
Functional Amblyopia
⢠Not due to the diseases in
the eye
⢠unilateral/bilateral of the
eye
⢠Reversible
⢠Examples:
â Refractive amblyopia
â Anisometropic amblyopia
â Meridonial amblyopia
â Strabismic amblyopia
Structural/Pathological Amblyopia
⢠Due to lesion in the eye or
visual pathway
⢠unilateral/bilateral of the
eye
⢠Irreversible
⢠Examples:
â Visual deprivation
amblyopia
â Toxic amblyopia
19. Type Causes
Refractive amblyopia ⢠Uncorrected isometropia
⢠Result :- A blurred image in both eyes.
Anisometropic amblyopia
(Second in frequency)
⢠Uncorrected anisometropia
⢠Result :- A blurred image in more ametropic
eye.
Meridonial amblyopia ⢠uncorrected high astigmatism
⢠Result :- A blurred and distorted image in
unilateral or bilateral eyes.
Strabismic amblyopia
(most common)
⢠Constant strabismus
⢠Suppression in deviated eye
Functional Amblyopia
20. Structural/Pathological Amblyopia
Types Causes
Visual deprivation amblyopia ⢠Opacities in ocular media or
structures
⢠Examples:- cataracts, cornea
opacities and cloudy vitreous in
infants.
Toxic amblyopia ⢠Drugs, tobacco, alcohol, chemicals,
nutritional disorders.
21. What are the sign and symptoms of
amblyopia?
Symptoms
⢠No symptoms
⢠Blurred vision
⢠Reduced vision
⢠Reduced contrast
sensitivity
Signs
⢠No obvious sign, unless
severe abnormality is
present.
⢠Rubbing or squinting of
eyes
⢠Misaligning eyes
⢠Reduced VA
⢠Droopy eyelid
23. Assessment of deviation
â Compare magnitude at distance versus near
⢠Laterality
⢠Concomitancy
⢠frequency
â The test is
⢠Cover test
⢠Hirchberg test
â Uses pen torch
â Corneal reflexes
⢠Bruchner test
â Uses ophthalmoscope
â Observe the color and brightness of fundus reflexes and
compared
25. Strategies in assessment of amblyopia
1. Visual Acuity (VA)
⢠Degree of amblyopia
⢠Crowding phenomena
â Normal Snellen Chart
⢠Line Acuity
â Single Letter Chart
⢠Single Letter Acuity
2. Neutral Density (ND) Filter
⢠Depth of amblyopia
⢠Differentiate between
organic amblyopia or
functional amblyopia
26. 1. Visual Acuity (VA)
â Amblyopes perform better when isolated letters
are used instead of full chart.
â Crowding effect
⢠Single letter acuity
â Infant
⢠Teller acuity chart
â Preschool-aged children
⢠Lea symbols, HOTV or broken wheel cards
â School-aged children
⢠Snellen chart or Log MAR chart
28. Single Letter Acuity
Advantage
⢠Directly measures acuity
especially in children 3-6
years old.
Disadvantage
⢠Isolated letters can be
used, which may lead to
under estimated
amblyopia visual loss.
Solutions:
ďś Crowding bar may help alleviate this problem
29. Crowding effect
⢠Crowding bar, or contour interaction bars, allow the examiner to
test the crowding phenomenon with isolated optotype.
⢠Bar surrounding the optotype mimic the full of optotype to the
amblyopia child.
E O
31. ⢠In strabismic eye, mostly
it use other part of area
instead of fovea area
which consist rod.
⢠Image that form will
reduce in contrast.
⢠Hence, it also reduce the
visual acuity of the eye.
32. 2. Neutral Density (ND) Filter
⢠Strabismic amblyopia
â Better VA with ND filter
compared to the normal
eye
â The use of a neutral-
density (ND) filter in
front of the fixing eye
enhanced motion-in-
depth performance.
â exhibit residual
performance for motion
in depth, and it is
disparity based
⢠Anisometropic amblyopia
â Cannot be diagnosed
with neutral density filter
ND bar
33. Neutral Density (ND) Filter
Strabismic amblyopia Anisometropic amblyopia
VA increased with ND filter VA cannot be diagnosed with ND
filter
34. Contrast sensitivity test
â Detect functional differences between
strabismic and anisometropic amblyopes
â Strabismic amblyopes showed abnormalities
only in the high spatial frequency range
â Anisometropic amblyopes showed an
abnormal function both in the low and high
spatial frequency range
36. The contrast sensitivity function
⢠A- normal contrast
sensitivity function
⢠B- mid to low contrast
sensitivity losses
⢠C- more severe
refractive errors or
severe amblyopia
⢠D- Mild refractive
error or mild
amblyopia
Examples of how the CSF is altered due
to refractive error or disease.
* The pivotal visual developmental study of Harwerth et al.
37. Eccentric fixation
â Fixate away from fovea
⢠In strabismic amblyopic eye
â Visuscopy
⢠Detect and assess eccentric fixation
⢠Explain decreased vision and lead to a more
accurate measurement of strabismus
⢠Grid center is temporal to foveal reflex(temporal
EF)
⢠Grid center is nasal to foveal reflex(nasal EF)
⢠Grid center is superior to foveal reflex(superior EF)
⢠Grid center is inferior to foveal reflex(inferior EF)
39. Binocularity/stereoacuity test
â Ambyopia reduced VA, it also has reduced stereopsis
â Stereo smile for infant
â Preschool random-dot stereogram or random-dot test for
preschool children
TNO test
41. Refraction
â commonly can determine anisometropia
â Cycloplegic refraction
⢠Spasm the ciliary muscle to inactive the
accommodation by using drug
â Uses 1% cyclopentolate hydrochoride
â Usually more hyperopic or more astigmatic eye
for the amblyopic eye
42. External and internal ocular
examination of the eye
â Determine either it is visual deprivation
amblyopia or afferent pupillary defect are
characteristic of optic nerve disease but
occasionally appear to be present with
amblyopia
â To rule out ocular pathology
â These examination consist of assessment
⢠Physiological function
⢠Anatomical status
44. ďźGOAL OF TREATMENT:
to restore and improves visual acuity by two
strategies:
1. present CLEAR retinal image to the amblyopic eye
⢠eliminate causes of visual deprivation
⢠correcting visually important refractive errors
2. make the child use the amblyopic eye
⢠Recommended treatment should be based on
â patientâs age, visual acuity, compliance with previous
treatment & physical, social and psychological status
45. ďź CHOICES OF TREATMENT
the choices of treatment of amblyopia are used alone or in
combination to achieve goal of treatment
1. Passive therapy:
The patient experiences a change in visual stimulation without any
conscious effort
i. Proper refractive correction
ii. Occlusion
iii. Penalization
46. Passive therapy:
i. Proper refractive correction
⢠PURPOSE:
â to provide sharp images and
providing OPTIMAL environment for
amblyopia therapy
⢠Give pt proper optical correction
alone
â Short period of time (6-8 weeks)
before initiation of other therapy
47. Passive therapy:
ii. Occlusion
⢠PURPOSE:
cover good eye to stimulate amblyopic eye
⢠Enable the amblyopic eye to enhance neural input to the visual cortex
⢠Decreasing inhibition better eye
48. ⢠occlusion can be classified in several ways:
â Ways of patching
⢠adhesive patch
⢠spectacles occlude
⢠opaque contact lens
â Type
⢠direct occlusion: to stimulate amblyopic eye
⢠inverse occlusion: to weaken eccentric fixation
â Duration
⢠full time occlusion : for deprivational amblyopia
⢠part time occlusion : to help preserve fusion
49. ⢠Ways of patching
â There are several ways of patching
â Excluding light and form:
⢠Adhesive patching
⢠Spectacle occlude
⢠Opaque contact lens
â Excluding form (ie: frosted glass)
50. - Partial patching form
⢠allow appreciation of form but diminish
acuity
â ie. Translucent materials (Bangerter foil)
â foil is cut to size and positioned on inner
lens surface
⢠or occlusion covering part of spectacles
â ie. Lower half of spectacles
â to promote use of the amblyopic eye for
near work
51. ⢠Type
⢠Direct occlusion
⢠Patch the good eye
⢠stimulate amblyopic eye
⢠Indication for
⢠deprivation amblyopia
⢠anisometropic amblyopia
52. ⢠Inverse occlusion
⢠For amblyopia associated with EF --> strabismic
amblyopia
⢠Patching the amblyopic eye
⢠To weaken eccentric fixation of amblyopic eye
⢠If children under 5 year old age
⢠direct full time occlusion may risk reverse amblyopia
⢠Do direct occlusion alternate with inverse occlusion
⢠Ie: for 3 years old children, may need 3 days direct and 1
day indirect occlusion consider 1 cycle and repeated
period of time
53. ⢠Duration
â Based on binocular vision status, age,
performance need
⢠Full time occlusion
⢠24 hours a day/waking hours
⢠For children over 7 yearsď over plastic age
⢠When there is no binocular vision
⢠strabismic amblyopia
â Alternate strabismus
â Constant strabismus
⢠Also anisometropic amblyopia with poor binocular
vision
⢠Shows more rapid development
54. ⢠Part time occlusion
⢠For specific periods / prescribed activities
⢠When binocularity is present
⢠anisometropic amblyopia
⢠To help preserve fusion
⢠Prevent occluded eye become amblyopic if doing full time
occlusion
⢠Children under 4 years
⢠2 hours per day
⢠Prevent deprivation amblyopia in good eye
55. ⢠Occlusion is maintained until there has
been no further improvement for the last 5-
6 weeks
⢠Frequent check are necessary to monitor
ocular health, binocular status and each
eyeâs acuity
56. 1. Drug penalization
⢠1 gtt of 1% atropine instilled daily
⢠to good eye
⢠Provide sufficient blur to force the
child
⢠use amblyopic eye at near
⢠good eye at distance
1. Has cosmetic advantages and does
not totally disrupt binocular vision
⢠Effective method of treatment
⢠for mild to moderate amblyopia in
children
Active therapy:
Penalization
57. 2. Optical penalization
⢠Children who do not tolerate
patching
⢠Fog the good eye (non-
amblyopic eye) +3.00 D
⢠Amblyopic eye use for distance
and good eye use for near
⢠Not practically applicable
â Do near work most of time
compared to distance
58. 2. Active therapy:
⢠is designed to improve visual performance by the patient âs conscious
involvement in a sequence of a specific, controlled visual task that
provide feedback
i. CAM visual stimulator
ii. Intermittent photic stimulation
iii. Pleoptic
59. Active therapy:
i. CAM visual stimulator
⢠Treat amblyopia
â by intense visual stimulation for
short period of time
⢠Grating of different spatial frequency
are rotated in front of amblyopic
eye
⢠The good eye is occluded
⢠Method based on:
â cortical cell response to specific line
orientation and to certain spatial
frequency.
â Therefore rotation ensured that a
large range of cortical neurons are
stimulated
⢠Better for anisometropic amblyopia
60. Active therapy:
ii. Intermittent photic stimulation
⢠Mallet IPS unit
⢠described as the "heightened
response" to a visual stimulus
⢠The targets
â consisted of slides containing much
detail of varying type and angular
dimension
â viewed against a red flickering
background.
⢠Red slight stimulation at 4Hz
⢠detailed visual task for 20-30
minutes
62. Active therapy:
iii. Pleoptics
⢠Purposes :
â To disrupt eccentric fixation in strabismic
amblyopia
⢠Apparatus based on ophthalmoscope
principle
⢠Euthyscope, projectoscope, pleutophore
⢠Exposed peripheral retina to a very bright
light while protecting the macular area
⢠Only suitable for children >7 years old
Euthyscope
63. Surgery
If amblyopia is due to:
⢠cataract ď cataract surgery
⢠nonclearing vitreous opacities ď vitrectomy
⢠corneal opacities ď corneal graft
⢠Blepharoptosis ď tarsal tuck
Introduction
What is amblyopia?
neurophysiology of amblyopia
types
causes
Classification
sign and symptoms
Assessment
VA testing
Contrast sensitivity test
ND filter test
Stereoacuity test
Eccentric fixation
Management
Passive therapy
Active therapy
The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.
Amblyopia:Â The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye. Amblyopia is the most common cause of decreased vision in children.
in normal vision, an image is seen by both eyes and blended into one picture by the brain
When one eye is weaker, the brain ignores the image sent by the weaker eye
amblyopia or loss of vision results.
Amblyopia can be caused by anything that interferes with vision for a significant amount of time during the critical period from birth to about 6 years of age.
poor aim- most common
poor focus- most difficult to detect
poor clarity- most severe
most difficult to detect
each eye have unequal refractive error
Both eye cannot be in focus at the same time
Blurred image in one eye is ignored by the brain
Meridional amblyopia is a mild condition in which lines are seen less clearly at some orientations than others after full refractive correction. An individual who had an astigmatism at a young age that was not corrected by glasses will later have astigmatism that cannot be optically corrected after 2 y/o.
most common
Both eyes not aimed in exactly same direction
Brain turns off misaligned eye to avoid double vision
Age onset of a strabismus:
Critical period- developing amblyopia(birth-3y/o)(5-7y/o)
-deep constant suppression
After critical period/ adulthood- not lead to amblyopia
- constant diplopia because suppression of the eye is difficult and the both eyes retain good VA
most severe
disuse/ understimulation of the retina
Due to eye disorder- e.g cataract,corneal opacties,ptosis, eyelid tumors,etc.
visual not develop well - brain
Drugs: - chloramphenicol- use in certain infection can cause toxic antibiotics
digoxin-Antiarrhythmic Agent
 ethambutol-Antitubercular Agent
Tobacco amblyopia â a condition in which the vision is lost because of the use of tobacco. The toxic effects of tobacco constrict the vessels of the body and interfere with circulation. The optic nerve is very sensitive to tobacco and can be easily irritated by excessive smoke. As a result, the optic nerve swells, a condition known as optic neuritis.
Alcohol- disorder involves lost vision, including scotomas (blind spots) and decreased visual acuity within the central portion of the visual field
Chemicals-Â Lead, methanol can cause optic nerve damage
Nutritional disorders- Strachan's syndromeď
Figure 2 The optic nerve head in patients with ischemic optic neuropathies
Refractive, anisometropic- affected same proportionally the centrally and peripherally.
Strabismus â affected foveal area.
Meridonial â affected the area along the blurred astigmatic meridian.
Visual and toxic- may affected part or entire visual field.
Amblyopia is primarily a defect of central vision. There is a critical period for sensitivity in developing amblyopia.
The time necessary for amblyopia to occur during critical period is shorter for stimulus deprivation than for strabismus or anisometropia.
Visual deprivation amblyopia
It is usually caused by congenital or early acquired media opacity.
This form of amblyopia is the least common but most damaging and difficult to treat.
In bilateral cases acuity can be 20/200 or worse.
Toxic amblyopia
Endogenous/ Exogenous poisoning.
Most severe
Characteristics of Amblyopia
General characteristics of amblyopia are:
1. Abnormal position of pupil2. Blinking or rubbing eyes frequently 3. Narrowing his/ her eyes or slanting when looking at objects4. Looking at objects in a very close distance 5. Leaning forward or aside when looking at object in distance 6. Having problems when reading, such as skipping words 7. Always making mistake when writing or copying 8. Excessive tearing and sensitive to light 9. Red eyes, swollen eyelid and secretion in eyes 10. Motion sickness when travelling long journey
The contrast sensitivity function provides a more thorough representation of the visual system. For example, the pivotal visual developmental study of Harwerth et al. (17) characterized the changes in the contrast sensitivity function after different periods of monocular deprivation in monkeys. The loss of sensitivity in the mid to high spatial frequencies was profound during abnormal visual development, with increased deprivation leading to further contrast losses. Not only will certain disease/disorders of the eye reduce visual acuity, contrast sensitivity will also be affected (18). For example, patients with multiple sclerosis will have mid to low contrast sensitivity losses (Fig. 25B), whereas patients with cataracts will have an overall reduction in contrast sensitivity (Fig. 25C). Mild refractive error or mild amblyopia will lead to a CSF similar to D in Fig. 25, with more severe refractive errors or severe amblyopia, resulting in a CSF similar to curve C.
1. Passive therapy: The patient experiences a change in visual stimulation without any conscious effort
Optical correction
Occlusion
Penalization
2. Active therapy: is designed to improve visual performance by the patient âs conscious involvement in a sequence of a specific, controlled visual task that provide feedback
CAM visual stimulator
Intermittent photic stimulation
Pleoptic
*Passive therapy (spectacles, occlusion, pharmacological agents). The patient experiences a change in visual stimulation without any conscious effort
*Active therapy is designed to improve visual performance by the patient âs conscious involvement in a sequence of a specific, controlled visual task that provide feedback
Useful to give the patient a short period of time (6-8weeks) with proper optical correction alone before the initiation of other amblyopia theapy
This animation shows the wiring involved with amblyopia, and why we patch eyes to correct vision.
1. Total patching excluding all light and form
Adhesive patch
Spectacle occlude
Opaque contact lens
2. Total patching excluding form only
allowing the passage of some light.
Semi opaque occlusion material such Blenderm tape or frosted glass, is effectively total occlusion.
under 5 year old age
Full time direct occlusion may risk reverse amblyopia
Need to establish alternate occlusion (direct and inverse)
Ie: for 3 years old children, may need 3 days direct and 1 day indirect occlusion consider 1 cycle and repeated period of time
described as the "heightened response" to a visual stimulus when an active exposure to light of one second was alternated with a dark period of thirty seconds
provide alternate stimulation of the amblyopic eye with equal dark and light intervals, the frequency of four light flashes persecond (4Hz) being chosen after much clinical experimentation.
The targets consisted of slides containing much detail of varying type and angular dimension, and were viewed against a red flickering background.
provide alternate stimulation of the amblyopic eye with equal dark and light intervals
The underlying purposes :
eccentric fixation must be disrupted first and then the fovea retrained to resume normal fixation
Apparatus based on ophthalmoscope principle
Euthyscope, projectoscope, pleutophore
Used to exposed peripheral retina to a very bright light while protecting the macular area
This resulted in after images, which, if negative, had a clear area corresponding to the macula, which the patient was then trained to localized correctly.
Pleoptic treatment was only suitable for older children or adults