Eye Movements and Squint

Question 1

What is strabismus?

Answer 1

Abnormalities of coordination of ocular movmement characterised by misalignment of the visual axes

Question 2

What is esotropia and exotropia? When do they occur?

Answer 2

Esotropia is convergenti squint - one eye turned in - most common in children
Exotropia is divergent squint - one eye tuned out - occurs in older children

Question 3

What are the two types of squint?

Answer 3

Non-paralytic (concomitant) - common

Paralytic (rare

Question 4

When do non-paralytic squints start?Why do they occur? Are they constant? Esotropic or exotropic?

Answer 4

In childhood
Imbalance in extra ocular muscles
Can be constant or not
Esotropic>Exotropic

Question 5

What are tests for strabismus?

Answer 5

Corneal reflection test:
Hold light source 30cm from bace to see if the light reflects centrally and symmetrically on each cornea - if asymmetrical there is a squint.

Cover test:
Ask child to focus on object
Cover one eye
Movement of the uncovered eye to take up fixation as the other eye is covered demonstrates manifest squint. Latent squint is reviled by moment of the covered eye as the cover is removed.

Question 6

How is strabismus managed?

Answer 6

OOO
Optical
Assess refractive state after cyclpentolate 1% drops (cycloplegia allows objective determination of the refractive state, mydriasis allows a good view into the eye to exclude abnormality) - provide spectacles.

Orthoptic:
Patching the good eye encourages use of the one which squints and prevents amblyopia (lazy eye)

Operations:
Resection and recession of rectus muscles to help alignment
Botox may be used

Question 7

What is amblyopia

Answer 7

Vision development disorder in which an eye fails to achieve normal visual acuity even with prescription glasses or lenses
Lazy eye

Question 8

Describe paralytic squint

Answer 8

Diplopia is most on looking in the direction of pull of the paralysed muscle

Question 9

Describe third nerve palsy

Answer 9

Occulomotor palsy
Ptosis due to paralysis of elevator palpebral superioris
Mydriasis - fixed pupil dilation due to paralysis of the sphincter papillae
Down and out due to action of superior oblique and lateral rectus

Question 10

Describe fourth nerve palsy. Causes?

Answer 10

Trochlear palsy
Paralysis of the superior oblique
Results in extorsion leading to head tilt - ocular torticolilis)
Eye looks upward in adduction and cannot look down and in
Diplopia

Trauma, diabetes, tumour, idiopathic

Question 11

Describe 6th nerve palsy. Causes?

Answer 11

Abducens palsy
Paralysis of lateral rectus
Inability to abduct affected eye
Diplopia in horizontal plane
Eye is medially deviated

Tumour causing RICP - compresses nerve on edge of petrous temporal bone
Base of skull fracture
Vascular
MS

Question 12

Rectus muscle function?

Answer 12

Medial - adduction
Lateral - abduction
Superior - elevation, intorsion
Inferior - depression, intorsion

Question 13

Oblique muscle functions?

Answer 13

Superior oblique
Intorsion
Look down in adduction - down and in

Inferior oblique
Extorsion
Elevates gaze

Question 14

When are best results achieved in strabismus?

Answer 14

Early detection
If > 7 amblyopia may be permanent
Conscientious and disciplined amblyopia treatment
Optimal glasses

Question 15

What is pseudo quint?

Answer 15

Wide epicanthic folds give the appearance of a squint in the eye looking towards the nose
Corneal reflection confirms aligned eyes

Question 16

What happens in cover test of left convergent squint

Answer 16

When right eye is covered left eye moves outwards to take up fixation (becomes normal)

Question 17

What happens in cover test of left divergent squint

Answer 17

When right eye is covered, left moves inwards to take up fixation