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

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