It is unusual that you would need to do more than examine cranial nerves in a child in day to day practice, but this is for the purpose of clinical exams. It is a step by step guide for performing a thorough eye examination in a child with more details on potential findings and implications of these below.

Step-by-step

General Inspection

Plotting weight, height and head circumference is essential for any paediatric examination and can give you a lot of information.

• E.g. the child may be small for age due to prematurity and preterm babies can have reduced vision due to retinopathy of prematurity
• The child may be microcephalic due to a intrauterine TORCH infection which has caused chorioretinitis

Ptosis

• Caused by supranuclear lesions, e.g. contralateral lesion of cerebral hemisphere
• Caused by lesions of oculomotor complex, including CN III palsy
• Caused by lesions of oculosympathetic pathway (Horner syndrome), occurs with a constricted pupil. Early onset Horner is associated with heterochromia iridium
• Duane syndrome can cause Ptosis on the side of eye abduction. There is limited abduction of the affected eye with retraction of the eyeball into the socket on abduction. In 80% is unilateral
• Myopathy can cause bilateral Ptosis
• Mechanical problems can cause a Ptosis such as haemangioma or orbital cellulitis

Aniridia

• Hypoplasia of the iris. Can be associated with other developmental anomalies of the eye such as cataract, glaucoma and corneal opacification
• Can be autosomal dominant or can occur in WAGR syndrome

Cataracts

• Cause opacity
• No cause detected in 50% but some causes are hereditary, e.g. autosomal dominant, or chromosomal such as T21. Some metabolic disorders are associated with cataracts such as galactossaemia. Intrauterine TORCH infections can cause cataracts.

Visual Acuity and Stages of Visual Development

• Neonates will turn head towards a diffuse light source
• 6 week old infants will follow a face or large, coloured object
• By 3 months old infants eyes converge for finger play
• At 4 months infants follow objects through 180 degrees and turn the head
• At 5 months old infants reach for a toy within their visual field and are able to regard a small raising on a table
• At 6 months old infants move eyes together in all directions. A squint from 6 months onwards is abnormal. From 6 months and onwards the Stycar graded ball test can be used to test visual acuity formally.
• By 9 months old a baby should be able to pick up a raisin in a raking grasp and look for fallen toys and play peek a boo
• At 12 months, babies should be able to pick up a raisin with a neat pincer grasp and may be ble to pick up a hundred and thousand. If they can pick up a hundred and thousand then visual acuity must be at least 6/24
• By 2yo the visual acuity should be 6/6 and for preschool children the Sheridan Gardner test or E test can be used to test visual acuity.

Visual Fields

Most common visual field defects in paediatrics include:

• Bitemporal hemianopia, caused by a lesion in the pituitary compressing the optic chasm, e.g. a craniopharyngioma. This may be accompanied by other signs of pituitary dysfunction such as poor growth, hypothyroidism, Cushing disease, precocious puberty. May also cause signs of raised intracranial pressure such as headaches, vomiting, papilloedema and CNVI palsy.
• Homonymous hemianopia is caused by a lesion from the optic tract to the optic cortex
• Superior homonymous quadrantinopia is caused by a temporal lobe lesion
• Inferior homonymous quadrantinopia is caused by a parietal lobe lesion (PITS – pituitary causes inferior and temporal causes superior)

Eye Movements

CNIII (optic) innervates medial rectus muscle (controls abduction), superior and inferior rectus muscles (elevate and depress the eye) and the inferior oblique (elevates the adducted eye)

CNIV (Trochlear) innervates the superior oblique muscle (depresses the adducted eye)

CNVI (Abducens) innervate lateral rectus muscle (abducts the eye)

Lid lag can occur in thyrotoxicosis. Fatiguability on upward gaze can occur in myasthenia gravis

CNIII palsy can occur due to space occupying lesions, vascular lesions, arthritis, or demylination

CNIV palsy can be caused by space occupying lesions

CNVI palsy is often the first sign of raised intracranial pressure which could occur due to a space occupying lesions or idiopathic intracranial hypertension

Diplopia

• Side by side images are bought on by weakness of the lateral or medial recti muscles
• If images are above one another then the oblique or superior or inferior recti are weak
• Covering up the affected eye will make the second image disappear

Nystagmus

• Caused by an imbalance between ocular muscles
• Horizontal nystagmus can be caused by vestibular lesions, cerebellar lesions and toxins
• Vertical nystagmus can be caused by cerebellar or brain stem lesions
• Pendular nystagmus is caused by retinal problems, such as in oculocutaneous albinism or congenital nystagmus
• Other causes of nystagmus include: septa-optic dysplasia, Arnold-Chianti malformation, congenital nystagmus, space occupying lesions CNVI, inner ear pathology

Cover/Uncover Test

Examining for a latent squint. Before starting with the cover, uncover test, shine a pen torch into the eyes from a distance and look for an asymmetrical reflection which would indicate strabismus

A non paralytic squint is not due to a problem with Extraocular muscles or cranial nerves and can be esotropic or exotropic. Esotropia is a convergent squint and exotropia is a divergent squint

Fundoscopy

You should not be expected to perform Fundoscopy in a clinical examination as it is poorly tolerated by children and difficult to perform well without dilating the pupil beforehand.

However, you should know what you are looking for on Fundoscopy in children. The main pathology would be papilloedema or lens changes or lens dislocations. Other pathology could be diabetic retinopathy in an older child with terrible diabetic control, optic nerve hypoplasia in septo-optic dysplasia, or signs of retinopathy of prematurity

Papilloedema is swelling of the optic disc caused by raised intracranial pressure. In practice the optic disc will look swollen, and pale with raised edges, blurred margins and may obscure retinal vessels

Written and Edited by Dr Bex Evans, Paediatric Registrar