Download MBBS (Bachelor of Medicine and Bachelor of Surgery) 3rd Year (Third Year) Ophthal Binocular Single Vision Topic Handwritten Notes
When a normal individual fixes his visual
attention on an object of regard , the
image is formed in the fovea of both the
eyes separately but the individual
perceives a single image
OR
Coordinated use of both eyes so as to
produce a single mental impression
DEVELOPMENT OF
BINOCULAR SINGLE VISION
Basic visual functions are innate and
therefore present at birth
Binocular single vision being a
conditioned reflex is not present at
birth
It is acquired during the first 6
months and completed in few years
MILESTONES
Birth-No central fixation
First month-central fixation starts
developing
Six months-central fixation established
Macular stereopsis and accomodation
reflex fully developed
Six years-visual acuity 6/6 attained and
binocular vision fully developed
PREREQUISITES
MOTOR MECHANISM
Correct neuromuscular development so
that the visual axes are directed at the
object
SENSORY MECHANISM
Approximately equal image
clarity and size in the two eyes
Normal visual pathways
MENTAL PROCESS
Ability of visual cortex to promote
binocular single vision
GRADES OF BINOCULAR
SINGLE VISION
GRADE 1 ? SIMULTANEOUS PERCEPTION
Simultaneous perception exist when signals
transmitted from the two eyes to the visual
cortex are perceived at the same time.
It consist of the ability to see two dissimilar
objects simultaneously.
GRADE 2-FUSION
It is the ability of the two eyes to
produce a composite picture from two
similar pictures each of which is
incomplete in one small detail
GRADE 3-STEREOPSIS
Ability to obtain impression of depth by
superimposition of two images of the
same object seen from two slightly
different angles.
Tested with stereopsis slides in
synoptophore
ANOMALIES OF BINOCULAR
VISION
Suppression
Amblyopia
Abnormal retinal correspondence
(ARC)
Diplopia
Confusion
SUPPRESSION
It is a temporary active cortical inhibition
of the image of an object formed on the
retina of the squinting eye
Occurs only during binocular vision
AMBLYOPIA
Partial reversible loss of vision in one or
both eyes for which no cause can be
found by physical examination of the eye
Also called LAZY EYE
PATHOGENESIS
Improper visual development of visual pathway
due to operation of AMBLYOGENIC FACTORS
during the critical period of visual
development(birth to 6 years of age)
AMBLYOGENIC FACTORS
qVisual deprivation-anisometropia
qLight deprivation-congenital cataract
qAbnormal binocular interaction-strabismus
TYPES OF AMBLYOPIA
Strabismic Amblyopia
Stimulus Deprivation Amblyopia
Anisometric Amblyopia
Isoametropic Amblyopia
Meridional Amblyopia
CLINICAL FEATURES
Visual acuity is reduced
Effect of neutral density filter
Crowding phenomenon
Central or eccentric fixation pattern
Colour vision may be affected
TREATMENT
Occlusion therapy
Penalization- atropine/ optical
Pleoptic exersice
Pharmacologic manipulation-levodopa
/carbidopa
Perceptual learning
Computerised vision therapy
OCCLUSION THERAPY
Occlusion of the normal eye to force use
of amblyopic eye.
It should be ensured that opacity should
be removed and refractive error should
be corrected fully.
ABNORMAL RETINAL
CORRESPONDENCE
A state in which fovea of the normal eye
and an extra foveal point on the retina
of the squinting eye acquire a common
visual direction.
Crude type of binocular single vision
CONFUSION
When squinting occurs the two foveas
view two different objects that are
physically separated in objective space
and send two different images to a
single cortical perceptual area.
DIPLOPIA
Simultaneous perception of two images of
a single object
When squinting occurs an object in space
is perceived by the fovea of one eye and
extrafoveal point of the other eye, which
has a different projection. Thus an object
will be localized twice in space.
BINOCULAR DIPLOPIA
CAUSES
Paralysis of extraocular muscles
Space occupying leision
Restriction of ocular movements
Anisometropia
TYPES
Uncrossed diplopia
Crossed diplopia
UNIOCULAR DIPLOPIA
CAUSES
Subluxated clear lens
Subluxated introcular lens
Double pupil
Incipient cataract
Keratoconus
TESTS TO DETECT
ABNORMALITIES
Suppression-Worth's 4-dot test, 4
dioptre base out prism test,Red glass
test, Synoptophore test.
ARC- Worth's 4 ?dot test, Litmus stereo
test, Bagolini striated glass test, After
image test, Synoptophore test
This post was last modified on 11 August 2021