Strabismus

Question 1

What is meant by antagonist-agonist muscles?

Answer 1

These are muscles which are found on the same eye but move the eye in different directions e.g. MR and LR

Question 2

What is meant by the term synergist muscles?

Answer 2

These are muscles in the same eye which work to move the eye in the same direction e.g. Inferior rectus and Superior orbital both depress the eye

Question 3

What orbital muscles are innervation by CNIII

Answer 3

Superior Rectus
Inferior Rectus
Medial Rectus
Inferior Oblique

Question 4

What orbital muscle is innervated by CNIV

Answer 4

Superior rectus

Question 5

What orbital muscle is innervated by CNVI

Answer 5

Lateral Rectus

Question 6

What muscle primarily elevates the eye?

Answer 6

Superior Rectus

Question 7

What muscle is responsible primarily for depressing the eye?

Answer 7

Inferior rectus

Question 8

What muscle primarily adducts the eye?

Answer 8

Medial rectus

Question 9

What muscle primarily abducts the eye?

Answer 9

Lateral rectus

Question 10

What muscle is primarily responsible for the intorsion of the eye?

Answer 10

Superior oblique

Question 11

What muscle is primarily responsible for the extorsion of the eye?

Answer 11

Inferior oblique

Question 12

What is meant by the term yolk muscles?

Answer 12

These are the muscles which are responsible for moving both eyes in the same direction? e.g. right LR and Left MR are responsible for moving the eyes to the right

Question 13

What does Hering’s Law state?

Answer 13

That yolk muscles in a particular direction of gaze receive equal stimulus and simultaneous flow of innervations.

Question 14

What does Sherrington’s Law state?

Answer 14

An increase in the innervation of one muscle results in a decrease to the innervation of the antagonist muscle.

Question 15

What is meant by Amblyopia?

Answer 15

This is when the visual acuity is reduced in the early years of life (<8) due to developmental failure of the visual pathway between the eye and the occipital lobe’s visual cortex.
(Usually unilateral)

Question 16

What can cause amblyopia?

Answer 16

Strabismus
Refractive errors
Stimulus deprivation e.g. cataracts

Question 17

How can amblyopia be managed/prevented?

Answer 17

Manage underlying cause.

Eye patches on the good eye to allow visual connections to develop. Pharmacological penalisation using atropine

Question 18

What is meant by the term binocular vision?

Answer 18

This is the ability to fuse images from both eyes into one single image

Question 19

Define stereopsis:

Answer 19

Perception of depth

Question 20

What are the different components of fusion in binocular vision?

Answer 20

Stereopsis
Sensory fusion
Motor fusion

Question 21

What is heterophoria?

Answer 21

This is deviation of the eye which is hidden by fusion

Question 22

When would heterophoria become apparent?

Answer 22

When the fusion is broken, often by covering one eye

Question 23

Define eso and exo - phoria:

Answer 23

Esophoria: inward deviation
Exophoria: outward deviation

Question 24

Define heterotropia:

Answer 24

this is an abnormal alignment of the eye, also referred to as a manifest squint.

Question 25

Define eso and exo tropia:

Answer 25

Esotropia: Convergent squint
Exotropia: Divergent squint

Question 26

Which squint is the most common in children in the UK and what is it usually associated with?

Answer 26

Esotropia

Hypermetropia

Question 27

What are the different subtypes of accommodative esotropia?

Answer 27

Fully accommodative - resolves following hypermetropia correction
Partially accommodative - partially resolves following hypermetropia correction
Convergence excess - requires bifocal or surgery. Occurs in near vision only due to high convergence

Question 28

What is Brown syndrome?

Answer 28

This Is a unilateral syndrome caused by mechanical restriction of the tendon of the SO at the trochlea leading to limited elevation in adduction or on up gaze.
Can have an associated click sensation.

Question 29

What is Duane Retraction Syndrome?

Answer 29

This is a rare condition which arises from innervation of the LR muscles by CNIII rather than CNVI.
It is often assoc. w/ CNVI nucleus hypoplasia and can cause retraction of the globe on adduction.

Question 30

What other symptoms may be seen in Duane retraction syndrome?

Answer 30

Deafness
Goldenhar syndrome
(split into three types)

Question 31

What surgical technique may be used for a highly active IO:

Answer 31

Disinsertion.

involves separating the tendon at its insertion to make it weaker

Question 32

What is the indication for the surgical ‘tucking’ procedure?

Answer 32

Congenital 4th nerve palsy

Involves strengthening the superior orbit

Question 33

What is the indication for the surgical advancement procedure?

Answer 33

This involves bring the muscle closer to the limbus, and is done to strengthen the muscle. Often done in a previously recessed EOM.

Question 34

What is surgical resection vs recession used for?

Answer 34

This involves shortening the muscle to strengthen it, while recession is loosening the muscle to weaken it.
In constant exotropia, bilateral LR recession and MR resection corrects the eye misalignment

Question 35

What can exotropia’s be classified as and what are they associated with?

Answer 35

Constant
Intermittent
Assoc. w/ myopia

Question 36

What is intermittent exotropia:

Answer 36

This is the more common form of exotropia, and can be further classified as near or distance.
In near exotropia the exotropia gets worse on near objects.
In distance exotropia, the exotropia is worsened by looking at a distance with a normal A/C ratio.

Question 37

What is constant exotropia and how is it managed?

Answer 37

This type of exotropia is commonly seen in neurological anomalies, and occurs within the first 6 months of life. It is a constant large angle exotropia and is managed surgically with bilateral LR recession and MR resection.

Question 38

What class of patients is a near exotropia often seen in?

Answer 38

Young adults and teenagers with myopia.

Question 39

Define microtropia:

Answer 39

This is a small angle squint. patients will have a subnormal binocular singular vision with sensory and motor fusion, and reduced stereopsis.