Binocular vision ppt, Albinism and Amblyopia

1. AMBLYOPIA
Mahendra Singh
Assistant Professor and
consultant Optometrist.
CL Gupta Eye Institute.
UP India

2. DEFINITION
 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
 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
Ambloypia in simple means
dullness of vision or diminished
vision.
It arises from a greek word
It can be unilateral or bilateral.

4. ETIOLOGY
Oclusion, strabismus,
anisometropia, uncorrected high
refractive errors.
Opacities of ocular media.
Depriviation of light or form sense.

5. CLASSIFICATION
Functional amblyopia- which is
reversible.
Organic amblyopia- which is not
reversible.

6. FUNCTIONAL AMBLYOPIA
It is sub classified as :-
Stabismus amblyopia.
Refractive amblyopia.
Anisometropic amblyopia.
Ammetrpoic amblyopia.
Meridonial amblyopia.

7. FUNCTIONAL AMBLYOPIA
Stimulus depriviation amblyopia
Amblyopic examopsia
Idiopathic amblyopia
Amblyopia secodary to
Nystagmus
Hysterical amblyiopia

8. STABISMIC AMBLYOPIA
Occurs when there is longstanding
suppression.
When it is constant, unilateral and
at all viewing distances.
In early childhood.
Fovea suppressed to prevent
confusion and diplopia.

9. STABISMIC AMBLYOPIA
Active cortical inhibition point is
zero in deviating eye.
Stereopsis is severely decreased
or absent.
Visual acuity loss is more
compared to anisometropic
amblyopia.
Severity of amblyopia depends
on type of deviation. More

10. REFRACTIVE AMBLYOPIA
ANISOMETROPIC
AMBLYOPIA
Most common cause of
amblyopia.
Difference in the refractive
error of both eyes.
Dissimilarity of foveal image
clarity, size, clarity.

11. REFRACTIVE AMBLYOPIA
AMMETROPIC AMBLYOPIA
Due to uncorrected high
refractive error.
Bilateral amblyopia.
Isoametropic amblyopia can
be classified under this. Occurs
in children havin More than
+5.00D or More -10.00D.

12. REFRACTIVE AMBLYOPIA
MERIDONIAL AMBLYOPIA
Occurs due to uncorrected
astigmatic refractive error.

13. STIMULUS DEPRIVIATION
AMBLYOPIA
Result of lack of adequate visual
stimulus in early life.
Can be unilateral or bilateral.
Can be complete (when no light
entering) or Partial (when some
light enters).

14. AMBLYOPIA EXAMOPSIA
Due to disuse of the eyes.
E.g. Uniocular, congenital, or
traumatic cataract, corneal
opacity, complete ptosis
occlusion amblyopia.

15. IDIOPATHIC AMBLYOPIA
Unilateral.
Occurs in normal patients.
-Ve history of strabismus.
Clinically V/A and foveal
suppression will improve after
patching the good eye.
But it will recur once the treatment
is stopped.

16. ORGANIC AMBLYOPIA
Irreversible.
Due to undetectable organic
lesion in the visual pathway.
Classified as Toxic amblyopia.
Visual loss results from damage
to optic nerve fibers.
Due to certain poisons such
such as tobacco, ethyl, alcohol,
chloroquimine.

17. PATHOPHYSIOLOGY OF
AMBLYOPIA.
1. Amblyopic Factor-
1.Visual Depriviation.
2.Light depriviation.
3.Abnormal binocular
interaction.

18. CHARACTERISTICS OF
AMBLYOPIC PATIENT
 Reduced vision.
 Decreased contrast sensitivity.
 Suppression.
 Decreased stereopsis.
 Defective accommodation,
convergence and fusional vergence
affected.

19. CHARACTERISTICS OF
AMBLYOPIC PATIENT
 Spatial uncertainty (hand and
eye coordination not good).
 Crowding phenomena-
 May have unsteady fixation.
 May be associated with squint.

20. INVESTIGATIONS
 History.
 Visual acuity.
 Refraction.
 Cover test.
 Ocular motility.

21. INVESTIGATIONS
 Binocular assesment.
 Fixation pattern.
 Neutral density filter.

22. FIXATION PATTERN
 Can be centric i.e. with fovea.
 Can be eccentric i.e. any other
point except fovea.

23. CLASSIFICATION OF FIXATION
PATTERN
 Foveal fixation with 2 degrees of
fovea.
 Parafoveal fixation with 2-5
degrees of fovea.
 Para macular 5-10 degrees.
 More than 10 degrees i.e.
peripheral fixation.

24. DEFINITION
 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
 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.  The decrease in V/A is
due to reduction in form
discrimination.
 Most pronounced
underphotopic visual
condition.
 Critical period of
development  from birth
to 6 yrs.
 Amblyopia means
dullness of vision.
 In general V/A < 6/9
is  Amblyopia
 In general 20/30 --
20/70 mild (shallow)
20/80 – 20/120 
moderate , worse
than 20/120 is
marked (deep).
Amblyopia

26.  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
• Different classification under different
authors.
I :- Classification according to cause 
1. Strabismic Amblyopia
2. Anisometropic Amblyopia
3. Isometropic Amblyopia
4. Image degradation Amblyopia
5. Psychogenic Amblyopia

28. STRABISMIC AMBLYOPIA
 Occurs in long standing foveal suppression
 Constant unilateral strabismus in childhood
 Fovea got suppressed to prevent confusion
 Suppression is more intense than
anisometropic amblyopia .( as acuity loss
is more intense )
 Highly associated with eccentric fixation

29. ANISOMETROPIC AMBLYOPIA
 Most common cause of Amblyopia
 Flynn and Cassady reported  microtropia mostly
found with anisometropic amblyopia.
 He said 20%  solely anisometropia
48%  purely strabismic
32%  both strabismic & anisometropic
 It occurs due to decrease in contrast &
Aniseikonia.
 Severity of Amblyopia is depend upon amount of
error.
 Meridional Amblyopia

30. ISOMETRIC AMBLYOPIA
 2° to high symmetric refractive error
( hyperopia , myopia , astigmatism )
 Detected earlier than anisometropic
amblyopia.
 Little or no suppression.

31. IMAGE DEGRADATION
AMBLYOPIA
 Caused by physical obstruction to clear
vision in childhood.
 Due to light & form stimulus deprivation.
 Commonest cause is congenital cataract.

32. PSYCHOGENIC AMBLYOPIA
 Due to hysteria & malingering.
 Common in children
 Can occur in adults those are under
stressful situation.

33. II CLASSIFICATION
1. Functional
2. Organic

34. FUCTIONAL AMBLYOPIA
 Functional means psychological.
 It is reversible
 Causes like strabismus ,
anisometropia , isometropia ,
amblyopia – Ex – anopsia.

35. ORGANIC AMBLYOPIA
 It is due to any ocular pathology.
 It is of irreversible type
 Causes like Corneal lesions, any
retinal abnormality, cortical pathology.

36. AMBLYOPIA – EX – ANOPSIA
 Now called as Amblyopia of Disuse.
 It is due to stimulus deprivation.
 Causes like Corneal Opacity ,
cataract

37. III CLASIFICATION
• Chavasse’s divided amblyopia into two
types.
1. Amblyopia of Extinction
2. Amblyopia of Arrest

38.  Amblyopia of Extinction :- It is to refer to
deteroration of central visual acuity to
levels lower than the patient had
previously attained.
 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.  Developmental  Associated with strabismus,
refractive error, visual deprivation.
 Toxic  Due to ethambutol, Chloramphenical,
quinine etc.
 Other Types  Associated with ischemic optic
neuropathy, temporal arthritis, retrobulbar
neuropathy.
 Nutritional Due to vit-B12 deficiency.
 Hysterical  2 to an unconscious psychogic
disturbance.
 Malingering  Conscious faking

41. ELECTROPHYSIOLOGICAL
TESTS
 VER ( visually evoked response)
 It reflects visual input from photoreceptors to
the occipital cortex.
 Pattern stimulus is used instead of flashing to
produce less variability.
 In infants it tell that 20/20 V/A reached by age
of 6 months
 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.
 So we can find any developmental
amblyopia.

42. PATHOPYSIOLOGY
 Two fundamental mechanism
responsible for developmental
amblyopia.
a) Visual Deprivation
b) Active Cortical Inhibition

43. VISUAL DEPRIVATION
 Could be uniocular or binocular
 Studies shown that there is a clearly
defined period during which deprivation
has a profound effect on the development
of normal behavior & physiologic
responses.
 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
 Both physiological an pharmacological
evidence exist for an active inhibitory
process in developmental amblyopia
 In physiological evidence, normal eye may
be responsible for active cortical inhibition
 Pharmacological evidence
e.g.:-nor epinephrine, GABA (gamma
amino butyric acid) {neurotransmitter
inhibitors}

45. Retina In amblyopia
 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 “b” wave and diminished
potential of “a” 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 “E” 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
Continue…..

52. Fixation
 Central
 Eccentric
a) Foveal (2˚)
b) Parafoveal (2˚-5˚)
c) Paramacular (5˚-10˚)
d) Peripheral (beyond 10˚)
e) unsteady

53. How to evaluate fixation
 Angle kappa
 Arc perimeter
 Major amblyoscope
 Visuscope
 Ophthalmoscope
 Euthyscope
 Co-oridinator
 Space co-oridinator
 Synaptophore using
haidinger brushes
 Maxwell spot (round,
dark, purplish spot
approx 3arc degree
in diameter)
 Haidinger brushes
test

54. Treatment
For Centric Fixation
 Full refraction under cycloplegics
 Direct occlusion
 Auto flashing
 Red filter
 Anti suppression
 Haidinger brushes
 VTP’s

55.  Full refraction under
cycloplegic
 Inverse occlusion for at
least 1 month
 Once fixation become
unsteady then
continue with inverse
occlusion and auto
flashing
 Haidinger brushes
 Direct occlusion when
fovea takes its
properties and fixation
become central
 Surgery
 Auto flashing
 Anti suppression
 VTP
 Physiological diplopia
For Eccentric Fixation

56. Goals of amblyopia treatment
Monocular goals
 Eliminate eccentric
fixation
 Eliminate eccentric
localization
 Establish foveal
fixation
 Establish foveal
localization
Binocular goals
 Eliminate sensory
anomalies
 Improve sensory
motor skills

57. VTP’s
 They improves –
1) Depth perception
2) Visual motor co-ordination
3) Focusing skills
4) Vision
5) Eye tracking
6) Stereopsis
7) Binocular co-ordination

58. VTP’s
 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

59. VTP,s

60. VTP,s

61. OTHER TECHNIQUES
1) CAM vision stimulator
2) Pleoptics
3) Penalization
Distance penalization
Near penalization
Total penalization
4) Computer Software's

62. MEDICAL TREATMENT
1) Citicholine
2) Levodopa
3) 6-hydroxydopamine
4) Naloxone
5) Bicuculline

63. TREATMENT PROBLEMS
1) Patching
e.g Elastoplasts
Opticlude
2) Parental cooperation
3) Occlusion Amblyopia
4) Recurrence