2. DEFINITION
īŽ It is a decrease in visual acuity in one or both
eyes that results from an inability to use the
eye or eyes for central fixation during a
critical period of visual development
īŽ Amblyopia is defined as the condition of
reduced visual acuity, usually unilateral nor
correctable by refractive means and nor
attributable to obvious structural or
pathological ocular anomalies
3. DEFINITION
īAmbloypia in simple means
dullness of vision or diminished
vision.
īIt arises from a greek word
īIt can be unilateral or bilateral.
8. STABISMIC AMBLYOPIA
īOccurs when there is longstanding
suppression.
īWhen it is constant, unilateral and
at all viewing distances.
īIn early childhood.
īFovea suppressed to prevent
confusion and diplopia.
9. STABISMIC AMBLYOPIA
īActive cortical inhibition point is
zero in deviating eye.
īStereopsis is severely decreased
or absent.
īVisual acuity loss is more
compared to anisometropic
amblyopia.
īSeverity of amblyopia depends
on type of deviation. More
11. REFRACTIVE AMBLYOPIA
īAMMETROPIC AMBLYOPIA
īDue to uncorrected high
refractive error.
īBilateral amblyopia.
īIsoametropic amblyopia can
be classified under this. Occurs
in children havin More than
+5.00D or More -10.00D.
13. STIMULUS DEPRIVIATION
AMBLYOPIA
īResult of lack of adequate visual
stimulus in early life.
īCan be unilateral or bilateral.
īCan be complete (when no light
entering) or Partial (when some
light enters).
14. AMBLYOPIA EXAMOPSIA
īDue to disuse of the eyes.
īE.g. Uniocular, congenital, or
traumatic cataract, corneal
opacity, complete ptosis
occlusion amblyopia.
15. IDIOPATHIC AMBLYOPIA
īUnilateral.
īOccurs in normal patients.
ī-Ve history of strabismus.
īClinically V/A and foveal
suppression will improve after
patching the good eye.
īBut it will recur once the treatment
is stopped.
16. ORGANIC AMBLYOPIA
īIrreversible.
īDue to undetectable organic
lesion in the visual pathway.
īClassified as Toxic amblyopia.
īVisual loss results from damage
to optic nerve fibers.
īDue to certain poisons such
such as tobacco, ethyl, alcohol,
chloroquimine.
19. CHARACTERISTICS OF
AMBLYOPIC PATIENT
ī Spatial uncertainty (hand and
eye coordination not good).
ī Crowding phenomena-
ī May have unsteady fixation.
ī May be associated with squint.
22. FIXATION PATTERN
ī Can be centric i.e. with fovea.
ī Can be eccentric i.e. any other
point except fovea.
23. CLASSIFICATION OF FIXATION
PATTERN
ī Foveal fixation with 2 degrees of
fovea.
ī Parafoveal fixation with 2-5
degrees of fovea.
ī Para macular 5-10 degrees.
ī More than 10 degrees i.e.
peripheral fixation.
24. DEFINITION
īŽ It is a decrease in visual acuity in one or both
eyes that results from an inability to use the
eye or eyes for central fixation during a
critical period of visual development
īŽ Amblyopia is defined as the condition of
reduced visual acuity, usually unilateral nor
correctable by refractive means and nor
attributable to obvious structural or
pathological ocular anomalies
25. īŽ The decrease in V/A is
due to reduction in form
discrimination.
īŽ Most pronounced
underphotopic visual
condition.
īŽ Critical period of
development ī from birth
to 6 yrs.
īŽ Amblyopia means
dullness of vision.
īŽ In general V/A < 6/9
is ī Amblyopia
īŽ In general 20/30 --
20/70 mild (shallow)
20/80 â 20/120 ī
moderate , worse
than 20/120 is
marked (deep).
Amblyopia
26. īŽ Amblyopia is also defined as by a difference
in visual acuity between two eyes.
For clinical purpose if the acuity
difference is two or more lines in both eye.
Then amblyopia is suspected.
e.g. Best corrected V/A
R 6/9 L 6/5
Other Definition
27. CLASSIFICATION
âĸ Different classification under different
authors.
I :- Classification according to cause ī
1. Strabismic Amblyopia
2. Anisometropic Amblyopia
3. Isometropic Amblyopia
4. Image degradation Amblyopia
5. Psychogenic Amblyopia
28. STRABISMIC AMBLYOPIA
īŽ Occurs in long standing foveal suppression
īŽ Constant unilateral strabismus in childhood
īŽ Fovea got suppressed to prevent confusion
īŽ Suppression is more intense than
anisometropic amblyopia .( as acuity loss
is more intense )
īŽ Highly associated with eccentric fixation
29. ANISOMETROPIC AMBLYOPIA
īŽ Most common cause of Amblyopia
īŽ Flynn and Cassady reported ī microtropia mostly
found with anisometropic amblyopia.
īŽ He said 20% ī solely anisometropia
48% ī purely strabismic
32% ī both strabismic & anisometropic
īŽ It occurs due to decrease in contrast &
Aniseikonia.
īŽ Severity of Amblyopia is depend upon amount of
error.
īŽ Meridional Amblyopia
30. ISOMETRIC AMBLYOPIA
īŽ 2° to high symmetric refractive error
( hyperopia , myopia , astigmatism )
īŽ Detected earlier than anisometropic
amblyopia.
īŽ Little or no suppression.
31. IMAGE DEGRADATION
AMBLYOPIA
īŽ Caused by physical obstruction to clear
vision in childhood.
īŽ Due to light & form stimulus deprivation.
īŽ Commonest cause is congenital cataract.
32. PSYCHOGENIC AMBLYOPIA
īŽ Due to hysteria & malingering.
īŽ Common in children
īŽ Can occur in adults those are under
stressful situation.
34. FUCTIONAL AMBLYOPIA
īŽ Functional means psychological.
īŽ It is reversible
īŽ Causes like strabismus ,
anisometropia , isometropia ,
amblyopia â Ex â anopsia.
35. ORGANIC AMBLYOPIA
īŽ It is due to any ocular pathology.
īŽ It is of irreversible type
īŽ Causes like Corneal lesions, any
retinal abnormality, cortical pathology.
36. AMBLYOPIA â EX â ANOPSIA
īŽ Now called as Amblyopia of Disuse.
īŽ It is due to stimulus deprivation.
īŽ Causes like Corneal Opacity ,
cataract
38. īŽ Amblyopia of Extinction :- It is to refer to
deteroration of central visual acuity to
levels lower than the patient had
previously attained.
īŽ Amblyopia of Arrest :- It is used to refer
to reduced central vision caused by
disturbance that prevented visual
development.
39. IV CLASSIFICATION
a) Organic amblyopia
1. Developmental Amblyopia
2. Toxic Amblyopia
3. Nutritional Amblyopia
4. Other types
b) Psychogenic Amblyopia
1. Hysteric Amblyopia
2. Malingering Amblyopia
40. īŽ Developmental ī Associated with strabismus,
refractive error, visual deprivation.
īŽ Toxic ī Due to ethambutol, Chloramphenical,
quinine etc.
īŽ Other Types ī Associated with ischemic optic
neuropathy, temporal arthritis, retrobulbar
neuropathy.
īŽ Nutritional ī Due to vit-B12 deficiency.
īŽ Hysterical ī 2 to an unconscious psychogic
disturbance.
īŽ Malingering ī Conscious faking
41. ELECTROPHYSIOLOGICAL
TESTS
īŽ VER ( visually evoked response)
īŽ It reflects visual input from photoreceptors to
the occipital cortex.
īŽ Pattern stimulus is used instead of flashing to
produce less variability.
īŽ In infants it tell that 20/20 V/A reached by age
of 6 months
īŽ If V/A in two eyes is equal , then difference in
amplitude in VER is close to zero & ratio of
two eyes is almost one.
īŽ So we can find any developmental
amblyopia.
42. PATHOPYSIOLOGY
īŽ Two fundamental mechanism
responsible for developmental
amblyopia.
a) Visual Deprivation
b) Active Cortical Inhibition
43. VISUAL DEPRIVATION
īŽ Could be uniocular or binocular
īŽ Studies shown that there is a clearly
defined period during which deprivation
has a profound effect on the development
of normal behavior & physiologic
responses.
īŽ Deprivation during the early part of the
critical period is more detorterious than at
later times. The period of sensitivity begins
as the ocular media clear and continuous
through visual maturation.
44. Active cortical inhibition
īŽ Both physiological an pharmacological
evidence exist for an active inhibitory
process in developmental amblyopia
īŽ In physiological evidence, normal eye may
be responsible for active cortical inhibition
īŽ Pharmacological evidence
e.g.:-nor epinephrine, GABA (gamma
amino butyric acid) {neurotransmitter
inhibitors}
45. Retina In amblyopia
īŽ Along with the lgb and striate area retina also
shows some abnormal changes
a) Receptor amblyopia:-some amblyopic eyes
have abnormal Stiles-Crawford effect. A defect
of the orientation of the retinal receptors results
in only a small V/A loss and abnormal Stiles-
crawford effect is actually a manifestation of
undetected eccentric fixation.
46. b) Pupil light reflex:- usually the pupil light
reflex is not abnormal in developmental
amblyopia. However with profound
developmental amblyopia there can be an
afferent pupilary defect. Normally central
retina stimulation causes marked
constriction then peripheral stimulation and
reverse is there in amblyopia.
47. c) Critical flicker Frequency:- The rate at
which the flicker of an intermittent light
stimulus disappears and become a continuous
sensation.CFF change does occur in
amblyopia.
d) Colour Vision:- It is effected if V / A is
below20/100 and also get effected in eccentric
fixation.
e) Light Perception:- dark perception is almost
normal,but form determination is worse at
photopic luminance.
48. f) ERG (Electro retino gram):- It shows some
abnormal changes.They include a lowered
amplitude of âbâ wave and diminished
potential of âaâ wave.
g) Saccadic and pursuit movements:- they
are also abnormal in amblyopia.3
abnormalities of saccadic system have
been reported:
i. Increased latency
ii. Decrease peak velocity
iii. Dysmetria ( inaccuracy )
49. INVESTIGATIONS
1) History:- relevant questions should be
asked related to strabismus,refraction
and social history.
2) Visual Acuity:- Charts available
a) Snellen acuity charts
b) Bailey lovie charts
c) Tumbling âEâ charts
d) Picture cards
e) OKN,VEP,Preferential looking test.
50. While recording visual acuity examiner
should suspect amblyopia if:-
a) Letters are missed on several lines using
the full chart
b) Letters in the middle of a line are more
frequently misread than those at the ends
of the line.
c) Letters are transposed in position.
d) Isolated letter acuity is better by one or
two lines than single line or full chart
acuity.
51. 3) Refractive error
4) Crowding Phenomenon
( Linear acuity and single letter acuity )
5) Neutral density filter
6) Visual Fields
7) Fixation
8) Cover test
9) Angle of Deviation
ContinueâĻ..
53. How to evaluate fixation
īŽ Angle kappa
īŽ Arc perimeter
īŽ Major amblyoscope
īŽ Visuscope
īŽ Ophthalmoscope
īŽ Euthyscope
īŽ Co-oridinator
īŽ Space co-oridinator
īŽ Synaptophore using
haidinger brushes
īŽ Maxwell spot (round,
dark, purplish spot
approx 3arc degree
in diameter)
īŽ Haidinger brushes
test
54. Treatment
For Centric Fixation
īŽ Full refraction under cycloplegics
īŽ Direct occlusion
īŽ Auto flashing
īŽ Red filter
īŽ Anti suppression
īŽ Haidinger brushes
īŽ VTPâs
55. īŽ Full refraction under
cycloplegic
īŽ Inverse occlusion for at
least 1 month
īŽ Once fixation become
unsteady then
continue with inverse
occlusion and auto
flashing
īŽ Haidinger brushes
īŽ Direct occlusion when
fovea takes its
properties and fixation
become central
īŽ Surgery
īŽ Auto flashing
īŽ Anti suppression
īŽ VTP
īŽ Physiological diplopia
For Eccentric Fixation
58. VTPâs
īŽ Examples:-
a) Thread and beat
b) Thread and needle
c) Drawing pictures
d) Games require strong fixation
e) Watching Television
f) Work require hand eye co-ordination