Download MBBS Ophthalmology PPT 20 Binocular Single Vision And Amblyopia Lecture Notes

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Binocular Single Vision and

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Amblyopia

Extra ocular muscles

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Names

Nerve supply and insertion

Action

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OCULAR MOTILITY

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A Uniocular movements are cal ed `ductions' and

1. Adduction.

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2. Abduction

3. Supraduction.

4. Infraduction.

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5. Incycloduction

6. Excycloduction

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B Binocular movements.

versions and vergences.

Versions (conjugate movements)

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1.Dextroversion
2.Levoversion
3.Supraversion
4.Infraversion
5.Dextrocycloversion

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6.Levocycloversion

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Vergences (dysconjugate movement)

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1. Convergence

2. Divergence

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1.Synergists.

2.Antagonists.

3.Yoke muscles.

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4.Contralateral antagonists.

Binocular single Vision

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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

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perceives a single image.

This state is called binocular single vision.

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Grades of binocular single vision

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Grade I -- Simultaneous perception.

Grade I --Fusion.

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Grade I I-- Stereopsis.

Grade I -- Simultaneous perception. Ability to see two dissimilar

objects simultaneously.

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Grade I --Fusion. It consists of the power to superimpose two

incomplete but similar images to form one complete image.

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Grade I I-- Stereopsis : Depth perception.

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Prerequisites of development of BSV

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Straight eyes (motor mechanism)
Clear vision in both eyes (Sensory

mechanism)

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Ability of visual cortex to promote BSV
(Central mechanism)

Advantage of BSV

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Enlargement of field of vision
Depth perception
Combined binocular visual acuity is better

than uniocular VA.

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Anomalies of binocular vision
Suppression

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Amblyopia

Suppression
It is a temporary active cortical inhibition of

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the image of an object formed on the retina

of the squinting eye.

Understanding Amblyopia

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AMBLYOPIA: DEFINITION

Amblyopia refers to partial loss of

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vision in one or both eyes, in the

absence of any detectable organic

cause.

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Understanding Amblyopia

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AMBLYOPIA:

SIGNIFICANCE

2%?4% of population affected

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Commonly unilateral

Bilateral amblyopia (rare) may mean permanently

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decreased visual acuity

Amblyogenic factors include :

Visual (form sense) deprivation as occurs in

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anisometropia,

Light deprivation e.g., due to congenital

cataract,

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Abnormal binocular interaction e.g., in strabismus.

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Understanding Amblyopia

SCREENING: IMPORTANCE

Amblyopia is usual y preventable or

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treatable

Early detection is key to effective

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treatment

Life-threatening disorders may present as

amblyopia

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Screening responsibility rests with primary

care physician

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Types of Amblyopia

1.

Strabismic

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2.

Anisometropic

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3.

Stimulus deprivation

4.

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Isoametropic

5.

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Meridional

6.

Idiopathic

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7.

Organic

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Diagnosis
1. Reduced VA
2. Effect of neutral density filter.

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3. Crowding phenomenon
4. Fixation pattern
5. Colour vision unaffected

Treatment

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Treatment of underlying cause fol owed

by:

1. Occlusion therapy

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2. Atropine Penalization
3. Drugs like levodopa.

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Understanding Amblyopia

EARLY DETECTION:

IMPORTANCE

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Visual function develops early in life

Treatment depends on plasticity of visual

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system

Treatment less likely to be effective as

children age increases

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Preventing Amblyopia

PREVENTING AMBLYOPIA:

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CONSIDERATIONS

Predisposing factors

Presenting features

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Detection methods

Treatment rationale

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Preventing Amblyopia

AMBLYOPIA:

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PREDISPOSING FACTORS

Poor clarity (media opacities) or blockage of light

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pathway (ptosis)

Poor focus (refractive error)

Poor aim (strabismus)

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Preventing Amblyopia

UNILATERAL AMBLYOPIA:

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PRESENTATION

Failed vision test

Strabismus

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Parental concern

Family history of amblyopia or strabismus

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Preventing Amblyopia

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VISION SCREENING AGES 3-5

May peek around ocluder

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Adhesive patch works best

Preventing Amblyopia

Strabismus is common underlying cause of amblyopia.

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Preventing Amblyopia

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DIPLOPIA IN CHILDREN

Not a feature of strabismus

May indicate a serious condition

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Evaluate promptly and refer

Preventing Amblyopia

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AMBLYOPIA: EARLY

DETECTION

Assess red reflex

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Determine visual acuity

Evaluate ocular alignment

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Preventing Amblyopia

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Normal red reflex

Preventing Amblyopia

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Asymmetric red reflex

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Preventing Amblyopia

Direct ophthalmoscope

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Preventing Amblyopia

NORMAL INFANT VISION

Good visual function

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Fixate and follow with each eye

Steady fixation

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Preventing Amblyopia

REFERRAL: IMMEDIATE

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Poor red reflex in one or both eyes

Concern about visual function by parent or

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doctor

Asymmetric or diminishing visual acuity

Constant or acute-onset strabismus

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Preventing Amblyopia

AMBLYOPIA:

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TREATMENT RATIONALE

Clearing the media

Focusthe image

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Initiating amblyopia therapy

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Preventing Amblyopia

Congenital cataracts

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Preventing Amblyopia

OCCLUSION THERAPY: PURPOSE

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Improves visual acuity

Does not eliminate strabismus

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Preventing Amblyopia

OCCLUSION THERAPY:

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PRECAUTIONS 1

Monitor visual acuity carefully at close intervals

Ensure vision is not being reduced in non-patched

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eye ("occlusion amblyopia")

Preventing Amblyopia

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OCCLUSION THERAPY:

PRECAUTIONS 2

Part-time occlusion may suffice

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Ensure parents understand purpose of patching and

importance of compliance

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Follow child's visual status into the teen years

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Preventing Amblyopia

ATROPINE PENALIZATION

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THERAPY

Atropine ointment or drops in non-amblyopic eye

at prescribed levels

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Atropinized eye cannot accommodate for near

vision

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Child can still use better-seeing eye for distance

Child switches fixation at near to amblyopic eye

Preventing Amblyopia

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ATROPINE THERAPY:

PRECAUTIONS

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Monitor VA carefully.

Ensure near VA in amblyopic

eye can support near tasks

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Allergic reactions are rare

(<1%)

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Systemic side effects are

uncommon and minimal

Warn parents that one eye wil

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have a "fixed and dilated pupil."

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MCQs

1. The primary action of superior oblique muscle is:

a. Incyclotorsion

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b. Adduction
c. Depression
d. Elevation

MCQs

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2. The secondary action of medial rectus muscle is:

a. Incyclotorsion
b. Adduction

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c. Depression
d. None

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MCQs

3. The secondary action of superior rectus muscle is:

a. Incyclotorsion

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b. Adduction
c. Depression
d. None

MCQs

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4. The extra ocular muscle inserted closest to the limbus:

a. IR
b. MR

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c. SR
d. LR

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MCQs

6. The extraocular muscle which does not arise from annulus of zinn:

a. IR

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b. MR
c. SR
d. IO

MCQ

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7. Amblyopia results from:

a. Abnormal binocular interaction
b. Defective spacial visual processing occurring in central visual

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pathways

c. Stimulus deprivation
d. All

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MCQs

8. What is amblyopia?

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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

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MCQs

9. A 4 yr old boy presented with inward deviation of either for 6 months.

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On dilated retinoscopy the patient had refractive error of +4 DS.

What would be the first line of management?

a. Refractive correction

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b. Squint surgery
c. Occlusion therapy
d. Orthoptic exercise

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MCQ

10. The best treatment modality for amblyopia is:

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a. Refractive correction only
b. Refractive correction followed by occlusion therapy
c. Orthoptic exercise
d. Ocular surgery

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