Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Ophthalmology PPT 20 Binocular Single Vision And Amblyopia Lecture Notes
Binocular Single Vision and
Amblyopia
Extra ocular muscles
Names
Nerve supply and insertion
Action
OCULAR MOTILITY
A Uniocular movements are cal ed `ductions' and
1. Adduction.
2. Abduction
3. Supraduction.
4. Infraduction.
5. Incycloduction
6. Excycloduction
B Binocular movements.
versions and vergences.
Versions (conjugate movements)
1.Dextroversion
2.Levoversion
3.Supraversion
4.Infraversion
5.Dextrocycloversion
6.Levocycloversion
Vergences (dysconjugate movement)
1. Convergence
2. Divergence
1.Synergists.
2.Antagonists.
3.Yoke muscles.
4.Contralateral antagonists.
Binocular single Vision
When a normal individual fixes on an object
of regard, the image is formed on the fovea
of both the eyes separately; but the individual
perceives a single image.
This state is called binocular single vision.
Grades of binocular single vision
Grade I -- Simultaneous perception.
Grade I --Fusion.
Grade I I-- Stereopsis.
Grade I -- Simultaneous perception. Ability to see two dissimilar
objects simultaneously.
Grade I --Fusion. It consists of the power to superimpose two
incomplete but similar images to form one complete image.
Grade I I-- Stereopsis : Depth perception.
Prerequisites of development of BSV
Straight eyes (motor mechanism)
Clear vision in both eyes (Sensory
mechanism)
Ability of visual cortex to promote BSV
(Central mechanism)
Advantage of BSV
Enlargement of field of vision
Depth perception
Combined binocular visual acuity is better
than uniocular VA.
Anomalies of binocular vision
Suppression
Amblyopia
Suppression
It is a temporary active cortical inhibition of
the image of an object formed on the retina
of the squinting eye.
Understanding Amblyopia
AMBLYOPIA: DEFINITION
Amblyopia refers to partial loss of
vision in one or both eyes, in the
absence of any detectable organic
cause.
Understanding Amblyopia
AMBLYOPIA:
SIGNIFICANCE
2%?4% of population affected
Commonly unilateral
Bilateral amblyopia (rare) may mean permanently
decreased visual acuity
Amblyogenic factors include :
Visual (form sense) deprivation as occurs in
anisometropia,
Light deprivation e.g., due to congenital
cataract,
Abnormal binocular interaction e.g., in strabismus.
Understanding Amblyopia
SCREENING: IMPORTANCE
Amblyopia is usual y preventable or
treatable
Early detection is key to effective
treatment
Life-threatening disorders may present as
amblyopia
Screening responsibility rests with primary
care physician
Types of Amblyopia
1.
Strabismic
2.
Anisometropic
3.
Stimulus deprivation
4.
Isoametropic
5.
Meridional
6.
Idiopathic
7.
Organic
Diagnosis
1. Reduced VA
2. Effect of neutral density filter.
3. Crowding phenomenon
4. Fixation pattern
5. Colour vision unaffected
Treatment
Treatment of underlying cause fol owed
by:
1. Occlusion therapy
2. Atropine Penalization
3. Drugs like levodopa.
Understanding Amblyopia
EARLY DETECTION:
IMPORTANCE
Visual function develops early in life
Treatment depends on plasticity of visual
system
Treatment less likely to be effective as
children age increases
Preventing Amblyopia
PREVENTING AMBLYOPIA:
CONSIDERATIONS
Predisposing factors
Presenting features
Detection methods
Treatment rationale
Preventing Amblyopia
AMBLYOPIA:
PREDISPOSING FACTORS
Poor clarity (media opacities) or blockage of light
pathway (ptosis)
Poor focus (refractive error)
Poor aim (strabismus)
Preventing Amblyopia
UNILATERAL AMBLYOPIA:
PRESENTATION
Failed vision test
Strabismus
Parental concern
Family history of amblyopia or strabismus
Preventing Amblyopia
VISION SCREENING AGES 3-5
May peek around ocluder
Adhesive patch works best
Preventing Amblyopia
Strabismus is common underlying cause of amblyopia.
Preventing Amblyopia
DIPLOPIA IN CHILDREN
Not a feature of strabismus
May indicate a serious condition
Evaluate promptly and refer
Preventing Amblyopia
AMBLYOPIA: EARLY
DETECTION
Assess red reflex
Determine visual acuity
Evaluate ocular alignment
Preventing Amblyopia
Normal red reflex
Preventing Amblyopia
Asymmetric red reflex
Preventing Amblyopia
Direct ophthalmoscope
Preventing Amblyopia
NORMAL INFANT VISION
Good visual function
Fixate and follow with each eye
Steady fixation
Preventing Amblyopia
REFERRAL: IMMEDIATE
Poor red reflex in one or both eyes
Concern about visual function by parent or
doctor
Asymmetric or diminishing visual acuity
Constant or acute-onset strabismus
Preventing Amblyopia
AMBLYOPIA:
TREATMENT RATIONALE
Clearing the media
Focusthe image
Initiating amblyopia therapy
Preventing Amblyopia
Congenital cataracts
Preventing Amblyopia
OCCLUSION THERAPY: PURPOSE
Improves visual acuity
Does not eliminate strabismus
Preventing Amblyopia
OCCLUSION THERAPY:
PRECAUTIONS 1
Monitor visual acuity carefully at close intervals
Ensure vision is not being reduced in non-patched
eye ("occlusion amblyopia")
Preventing Amblyopia
OCCLUSION THERAPY:
PRECAUTIONS 2
Part-time occlusion may suffice
Ensure parents understand purpose of patching and
importance of compliance
Follow child's visual status into the teen years
Preventing Amblyopia
ATROPINE PENALIZATION
THERAPY
Atropine ointment or drops in non-amblyopic eye
at prescribed levels
Atropinized eye cannot accommodate for near
vision
Child can still use better-seeing eye for distance
Child switches fixation at near to amblyopic eye
Preventing Amblyopia
ATROPINE THERAPY:
PRECAUTIONS
Monitor VA carefully.
Ensure near VA in amblyopic
eye can support near tasks
Allergic reactions are rare
(<1%)
Systemic side effects are
uncommon and minimal
Warn parents that one eye wil
have a "fixed and dilated pupil."
MCQs
1. The primary action of superior oblique muscle is:
a. Incyclotorsion
b. Adduction
c. Depression
d. Elevation
MCQs
2. The secondary action of medial rectus muscle is:
a. Incyclotorsion
b. Adduction
c. Depression
d. None
MCQs
3. The secondary action of superior rectus muscle is:
a. Incyclotorsion
b. Adduction
c. Depression
d. None
MCQs
4. The extra ocular muscle inserted closest to the limbus:
a. IR
b. MR
c. SR
d. LR
MCQs
6. The extraocular muscle which does not arise from annulus of zinn:
a. IR
b. MR
c. SR
d. IO
MCQ
7. Amblyopia results from:
a. Abnormal binocular interaction
b. Defective spacial visual processing occurring in central visual
pathways
c. Stimulus deprivation
d. All
MCQs
8. What is amblyopia?
a. Unilateral or bilateral subnormal vision without any organic cause
b. Bilateral subnormal vision with organic cause
c. Bilateral subnormal vision due to macular pathology
d. Unilateral subnormal vision with organic cause
MCQs
9. A 4 yr old boy presented with inward deviation of either for 6 months.
On dilated retinoscopy the patient had refractive error of +4 DS.
What would be the first line of management?
a. Refractive correction
b. Squint surgery
c. Occlusion therapy
d. Orthoptic exercise
MCQ
10. The best treatment modality for amblyopia is:
a. Refractive correction only
b. Refractive correction followed by occlusion therapy
c. Orthoptic exercise
d. Ocular surgery
This post was last modified on 07 April 2022