Paediatric ophthalmology

Question 1

What are some causes of amblyopia (lazy eye)?

Answer 1

Anisometropia (difference in shape between eyeballs, leading to different refractive powers)
Strabismus
Strabismic anisometropia
Visual deprivation
Organic causes - problems with retina / optic nerve

Question 2

What is the crowding phenomenon?

Answer 2

An amblyopic eye can be found to have a much higher VA than the unaffected eye when tested with single isolated letters
There is reduced contrast sensitivity so lines of letters are difficult to read

Question 3

What is the pathophysiology of amblyopia?

Answer 3

1. Monocular visual deprivation during visual development means there is competition between the neural pathways of the two eyes for impact on the brain
2. Anatomic relationships of photoreceptors and ganglion cell receptors affect amblyopia development also
3. Age of onset and duration of disability determine the severity

Question 4

What vision problems would a patient with amblyopia have?

Answer 4

Impaired VA
Poor stereo vision
Diminished pattern recognition
Low sensitivity to motion and contrast

Question 5

How is amblyopia managed?

Answer 5

Patch over good eye for varying amounts of time
Glasses
Chemical patching of good eye
Cannot reverse over age of 9

Question 6

What are the main classifications of strabismus (cross-eyed)?

Answer 6

Pseudostrabismus (pseudoesotropia / -exotropia)
Heterophoria (latent, occurs only at rest)
Heterotropia squint (concomitant = remains the same in all directions of gaze and incomitant = angle of deviation changes in different directions of gaze)

Question 7

What risk factors are there for strabismus?

Answer 7

Down’s syndrome
Apert-Crouzon syndrome
Premature infants with low birth weight
Family history (immediate)

Question 8

What are the two main theories of the pathophysiology of strabismus?

Answer 8

Claude Worth theory = caused by an inherent absence of cortical fusional potential
Chavasse theory = caused by poor motor alignment which leads to a poor sensory status

Question 9

What is the management for strabismus?

Answer 9

1. Correct refractive errors
2. Treat amblyopia
3. Orthoptic exercises (exotropia)
4. Miotics (esotropia, reduces accommodation)
5. Botulinum toxin (temporary paralysis of extraocular muscles)

Question 10

What are the main classifications of ptosis?

Answer 10

1. Neurogenic - defective innervation of the levator muscle of upper eyelid
2. Myogenic - levator muscle myopathy
3. Mechanical - levator function impaired due to mass effect of an abnormal structure
4. Aponeurotic - defective levator aponeurosis
5. Traumatic

Question 11

What are the main 2 muscles responsible for upper eyelid elevation?

Answer 11

1. Levator palpebrae superioris (CN III)

2. Muller’s muscle (sympathetic innervation)

Question 12

What can be found on examination of a patient with ptosis?

Answer 12

Absent upper lid crease in congenital cases
Miosis (Horner’s) or mydriasis (CN III palsy)
Deranged ocular motility (CN III palsy)

Question 13

How is ptosis managed?

Answer 13

Managed non-surgically in myogenic and some neurogenic cases with (eg) eyelid crutches
Surgical: levator resection, superior rectus utilisation, raising of frontal muscle, aponeurotic strengthening