Ophthalmology: Sub-specialty—Paediatric ophthalmology

Visual acuity in children

Before children can speak they can see, and surprisingly, we can measure their visual acuity fairly accurately using the tests described in this chapter.

Aim

How to assess visual acuity in different aged children.

Visual development

A child’s vision continues to develop after birth and maturation.
Normal visual development in both eyes is important for children to perceive the world, their education and their social interactions. An infant who appears not to see well may have delayed visual maturation or a more serious cause. Measuring visual acuity in children requires skill and patience, but even simple techniques can be used to elicit vision and reassure the parent.
It is important to detect amblyopia, as this can be treated by glasses and/or patching if discovered early enough.

Newborn child up to 2 months

Assessment of vision in the neonate is dependent on the age and behavioural state of the child. When a child is pre-verbal, you depend on his/her eye movements for information about visual function. At 6 weeks of age, children are able to smile. Without making any noise, smile at the child, and if the child smiles back, you know they can see!
A number of techniques are used to test vision in newborns:

Fix and follow

Use a pen torch or large brightly coloured silent toy to see if the child fixes and follows.
With the child sitting on the mother’s knee, move the toy slowly from left to right about 33 cm in front of the child’s face. If the child can see, they will follow the toy only if awake and if the toy is moved slowly as eye movements are immature at this age.
If possible, test each eye separately by occluding one eye with an occlusive patch.
If the child fixes and follows the target, record the vision as ‘fixes and follows’.
If the child doesn’t follow the toy, this may be because they can’t see, is drowsy or is just not interested; therefore, try again later.

Spinning baby test

Whilst spinning the child, observe his eye movements. The spinning will cause a conjugate deviation (nystagmus) in the opposite direction to the rotation if he can see. This is the vestibulo-ocular reflex (VOR).
When you stop spinning, there is a post-rotational nystagmus. If the nystagmus persists after a few seconds, the child may be severely visually impaired or have a cortical lesion.

Other clinical tests

Preferential looking

Cards have different-sized grating patterns on the right or left half of the card and are plain on the other half of each card. The card is shown to the infant, who will look towards the grating side if she can see it.

Visual evoked potentials (VEPs)

The child has electrodes on her head which record brain signals if she sees the pattern on the screen.

Infants up to 3 years of age

Cardiff Acuity Test

Another way of recording vision in these infants is to use the Cardiff Acuity Test, frequently referred to as Cardiff Cards (CCs) in clinical practice.
Each card has a line drawing of a familiar object on either the upper or lower half of the card, and the thickness of the lines varies. According to the thickness of the line, the card will have a letter (e.g. CC H) with a Snellen and LogMAR equivalent on the back for the examiner to see (e.g. 6/6 Snellen or 0.00 LogMAR for the finest line).
From a distance of 50 cm or 1 m, the cards are rapidly shown to the child and the examiner observes the child making vertical eye movements up and down to the location of the picture. For example, visual acuity is recorded as ‘CC H at 50 cm–Snellen Equivalent 6/9’. If possible, the acuity of each eye should be recorded separately.

Toddler (18 months–4 years)

Once the child can speak, you can use a subjective vision test and ask him to verbally identify some simple and familiar pictures.

Single and Crowded LogMAR Kay Picture Tests

The most common method of assessing vision in this group is with the Kay Picture Test.
The Single LogMAR Kay Picture Test consists of a spiral-bound book of cards. On each page, there is a single black line drawing of a picture on a white background which can usually be recognized by children from 18 months old.
The Crowded LogMAR Kay Picture Test consists of a larger spiralbound book of cards, on each of which there are four line picture drawings in a rectangular box on a white background. This allows for a linear visual acuity with a crowding effect for increased testing sensitivity, which can be used prior to the child learning letters. This test is recommended from 3 years old.
For both the Single and Crowded Kay Picture Test books, each line drawing has a Snellen and LogMAR equivalent depending on the size of the drawing (i.e. the largest drawing is equivalent to the 6/60 letter on the Snellen chart).
The examiner stands 3 m from the child and asks her to identify each picture.
The child can name the pictures, or if she is unable or too shy to name them, she can match the pictures using a matching card held by the child or by the parent that she is sitting with.

Young children (4–5 years)

Keeler Crowded LogMAR Test

The Keeler Crowded LogMAR Test consists of a box containing two crowded books and one uncrowded book.
In the crowded books, each page has four letters of one size.
The examiner stands 3 m away and presents letters on the card.
The child is asked to name the letters. If the child is unable to name the letters, he is given a matching card to use instead.
Each eye is examined separately, and the acuity recorded.

Strabismus (squints)

You will find that the terms ‘squint’ and ‘strabismus’ are used interchangeably.
Strabismus is the correct medical term. A child with strabismus can have a lazy (amblyopic) eye, whilst in an adult it can be indicative of a wide range of disorders: a cranial nerve palsy, tumour, trauma, thyroid eye disease or the like. In this chapter, we are concentrating on strabismus in children. Many of the principles of examination of a child also apply to an adult.

Aim

Understand strabismus terminology.
Do a cover test to detect strabismus.
Know the basic principles of amblyopia therapy.
A child with strabismus will not ‘grow out’ of it. There may be a sinister cause such as cataract or retinoblastoma, so you should always do a red reflex and if there is a white reflex, this is indicative of more serious pathology. Any child suspected of having strabismus should be referred to an orthoptist for precise measurements and possible patching, and to an ophthalmologist for assessment, including refraction and for management.
Orthoptists are allied health professionals who assess patients with diplopia (double vision), strabismus and eye movement defects. They work closely with ophthalmologists in the management of children’s visual development, testing paediatric visual acuity and treating amblyopia.

Aetiology and pathophysiology

Concomitant strabismus

Concomitant means that the deviation remains the same in all positions of gaze.

Binocular single vision (BSV) usually develops by 3–5 months old. If BSV does not ‘lock in’, esotropia (convergent strabismus) can develop at this time, although most concomitant strabismus develops later at around 2–4 years, particularly with hypermetropia (longsightedness requiring plus dioptre glasses).
Any cause of reduced vision in one eye will interrupt BSV and result in strabismus, such as cataract, retinoblastoma or anisometropia (a difference of refraction between the two eyes).
Children with a family history of strabismus or refractive error and those with developmental abnormalities have a higher incidence of concomitant squint.

Incomitant strabismus

Incomitant means that the angle of the deviated eye changes with position of the gaze and is not constant like in concomitant strabismus.

Congenital causes are rare (e.g. third, fourth or sixth nerve palsy).
Acquired incomitant strabismus presents with diplopia in adults. A child may adopt a compensatory head posture to minimize diplopia and therefore may not complain of diplopia. A very young child will suppress the second image and develop amblyopia if untreated.
Acquired causes include cranial nerve palsy (paralytic) secondary to intracranial pathology, thyroid eye disease and post-traumatic orbital floor fracture (restrictive).

Management

Orthoptists, optometrists and ophthalmologists collaborate in the management of strabismus using a combination of glasses, surgery and orthoptic treatment.

Childhood concomitant and congenital incomitant strabismus

Role of the orthoptist:

Measures visual acuity (VA).
Detects and measures strabismus using the Hirschberg test, cover tests and prism bar measurements.
Assesses eye movements.
Assesses binocular vision (including tests for stereopsis).
Monitors amblyopia therapy with patching ± atropine occlusion.

Refraction

The optometrist or ophthalmologist performs refraction (cycloplegic if child aged <7 years). In fully or partial accommodative esotropia with high hypermetropia (with dioptre glasses required), wearing glasses will fully or partially correct the deviation as well as improve visual acuity, and surgery may not be required.

Amblyopia therapy

Spectacles (if applicable) and a patch worn on the better eye for a specified number of hours per day, depending on the child’s age and visual acuity. The patch completely covers the good eye to encourage the bad eye (amblyopic one) to be used and develop vision.
This treatment method is generally unsuccessful after age 7 years.

Surgery

Strabismus surgery is performed if the strabismus is socially unacceptable and to restore or improve binocular vision. In esotropia, the horizontal rectus muscles are operated, recessing the medial rectus and resecting the lateral rectus or bimedial rectus recessions.

Acquired incomitant strabismus (children and adults)

The underlying cause must be established and treated (e.g. intracranial tumour, diabetes or hypertension).
Orthoptic management is by joining the diplopia with Fresnel prisms or prisms incorporated into the spectacle prescription.
Surgery is performed if BSV is not comfortably restored once the extraocular muscles recover or have been stable for at least 6 months.

Neonates

Aims

Confidently check for a red reflex.
Differential diagnosis of leukocoria.
Main sight-threatening eye problems in neonates.

Leukocoria

Leukocoria is derived from the Greek words ‘leuko’ = white, and ‘coria’ = pupil, when noted an urgent referral is indicated.
Leukocoria is seen as a white-coloured pupillary reflex when an ophthalmoscope light is shone at the pupil. In a normal red reflex, the ophthalmoscope light bounces off the red-orange retina and an overall red reflex is seen. Leukocoria can indicate severe ocular pathology and be amblyogenic. Causes of leukocoria include the following.

Retinoblastoma

This malignant tumour of the retina is the most common intraocular tumour of childhood.
It is the most sinister cause of leukocoria as it can potentially kill the child.
Urgent assessment and treatment are required by a joint paediatric oncology and paediatric ophthalmology team in a specialist centre.
Can be either hereditary (usually bilateral) or sporadic (usually unilateral).
Treatment involves radioactive plaque or enucleation and adjuvant chemotherapy.
90–95% survival at 5 years with treatment.

Congenital cataract

Presents as leukocoria, a dull red reflex, squint or nystagmus.
If bilateral, the child may be visually inattentive.
There is usually no relative afferent papillary defect unless there is other retinal or optic nerve pathology.
Causes include idiopathic (most common), familial autosomal dominant, galactosaemia and rubella (also causes microcephaly, congenital heart defects, corneal clouding and retinopathy).
Needs urgent (within days) assessment with a view to cataract surgery and subsequent amblyopia therapy. Some cataracts are small and need monitoring and amblyopia therapy.

Coloboma of the eye and eyelid

Failure of the choroidal fissure to close during embryological development. It is associated with a mutation in the PAX2 gene.
A chorio-retinal coloboma or large optic disc coloboma can also give a white retinal reflex and is associated with severe
amblyopia. Smaller colobomas of the iris can exist without affecting the posterior part of the eye and be associated with normal visual development.

Non-accidental injury (NAI)

A neonate with leukocoria or any type of ocular trauma may have NAI.

Retinopathy of prematurity (ROP)

Pre term babies born at <30 weeks and with birth weight <1500 g are screened.
Incomplete retinal vascularization leads to relative hypoxia causing new abnormal blood vessels to grow which leak and scar.
Leukocoria is seen only in advanced disease due to a large tractional retinal detachment.
The mainstay of treatment is ablation of the avascular retina and reduction of VEGF production with cryotherapy or laser.
Recently, the Bevacizumab Eliminates the Angiogenic Threat of Retinopathy of Prematurity (Beat-ROP) study has shown that intravitreal bevacizumab has a role in treatment for zone 1 and stage 3 disease.
Complications of treatment include cataract and myopia.
In severe ROP with retinal detachment, vitreoretinal surgery is often only palliative.

Other less common causes of Leukorcoria

familial exudative retinopathy
Coat’s disease
infections: toxoplasmosis and toxocariasis
hyperplastic primary persistent vitreous (HPPV).

Other neonatal ophthalmic conditions

Ophthalmia neonatorum is a notifiable disease.
The neonate usually has a unilateral or bilateral purulent conjunctivitis within a few days of birth.
Take swabs for bacteria (including Gram and Giemsa stains), a Chlamydia immunofluorescent antibody test and viral culture.
Suspect Neisseria gonorrhoeae (usually within 3 days of birth) or Chlamydia trachomatis (usually sub-acute from day 5 post-birth) until proved otherwise as both can cause blindness.
Systemic and topical treatment is essential, as is the referral of both parents to a sexually transmitted disease (STD) clinic.

Buphthalmos

A large eye in an infant associated with congenital glaucoma and a cause of blindness or defective vision
The intraocular pressure can be measured with a handheld tono-pen or ‘iCare’.

Anophthalmos and microphthalmos

Total absence of an eye (anophthalmos) or a very small ocular remnant (microphthalmos)
The aim of management is to promote orbital bony development by keeping the ocular remnant (microphthalmos or cyst) and expanding the soft tissue of the orbit and eyelids sequentially. Eventually, an ocular prosthesis (artificial eye) can be made specific to the patient.

Watering eyes (epiphora) due to congenital nasolacrimal duct obstruction (NLDO)

Aetiology: opening of the lower end of the nasolacrimal duct (where it enters the nose in the inferior meatus at the valve of Hasner) is often delayed for several months.
Note: an important differential for watery eyes in an infant is congenital glaucoma (assess for buphthalmos by measuring the diameter of the cornea).
Treatment of congenital NLDO:
○ Advise the parent that the watering is likely to resolve by age 1 year in 90% of cases.
○ Apply daily small-finger massage over the lacrimal sac at the medial canthus to open the valve.
○ An expressible mucocoele suggests nasolacrimal duct block requiring dacryocystorhinostomy surgery.
○ For persistent watering over age 1 year, do a syringe and probing (S&P) under general anaesthesia. If recurrent repeat S&P and consider intubation or DCR.

Ptosis

A neonate with an upper eyelid drooping across the visual axis is likely to have a weak levator palpebrae superioris (LPS) function. They should be referred urgently to an ophthalmologist with a view to urgent frontalis suspension surgery as this is an amblyogenic stimulus.
Otherwise, wait until age 4 years if visual development is not threatened.

Infants and older children

Aims

Identify common paediatric eyelid, tear duct and orbital problems.
Know why and when to operate on ptosis.
Management of orbital cellulitis.

Eyelid lumps

Capillary haemangioma

Swelling appears at birth or shortly afterwards, then increases in size for about 6 months. This is most common in the superonasal orbit and eyelid. It grows slowly, during which time it can cause mechanical ptosis and risk of amblyopia if the lid covers the visual axis or its weight causes astigmatism. This used to be treated with local infiltration of steroids to speed up resolution and reduce the bulk of the haemangioma, but it is now treated with oral beta-blockers. It usually spontaneously regresses after age 1 year.

Stye (external hordeolum)

Lash follicle infection—hot red lump that resolves rapidly.

Chalazion

Lump due to an inflamed blocked meibomian gland duct, which will usually gradually resolve over a few weeks without treatment.
Topical antibiotic ointment for 7–10 days.
Incise and curette under a short general anaesthetic if not improving with treatment.

Molluscum contagiosum

Typically small, dome-shaped itchy lesions with central core of softer material.
On hands, face and trunk and around eyes.
Causes a follicular conjunctivitis.

Common oculo-orbital problems

Limbal dermoid: benign congenital tumour often associated with eyelid coloboma in Goldenhar’s syndrome.
Dermoid cyst: smooth round non-tender immobile lump on orbital rim. Gradually grows. Risk of rupture. Contains
cheesy white material +/− hairs.
Dermolipoma: benign congenital conjunctival and orbital yellow fatty lesion. Lies very close to lacrimal ductile openings, therefore advise caution in excision or leave. Risks a severe dry eye from lacrimal ductile damage.

Ptosis (drooping eyelid)

Congenital dystrophic (fatty levator muscle).
Acquired third cranial nerve palsy (rare).
Inflammation, such as vernal keratoconjunctivitis.

Ptosis assessment

Measure the visual acuity, levator function, vertical palpebral aperture distance and skin crease height. Observe Bell’s phenomenon. Look for aberrant eyelid movements with chewing and talking (Marcus Gunn jaw–winking ptosis).

Surgery

Depends on the levator function.
Very poor (<5 mm), internal suspension to the frontalis muscle (frontalis suspension).
Good levator function from >5 mm up to 15 mm.
Anterior or posterior approach levator resection (ALR or PLR, respectively).

There is a risk of amblyopia when the eyelid covers the pupil axis. Do an urgent frontalis suspension with non-autologous material (Gortex or Prolene) and later autogenous fascia lata frontalis suspension (where fascial strips are taken from their upper leg). If the eyelid is only slightly drooping and the child can easily ‘see out from beneath it’ by adopting a small chin-up head position, there is less risk of amblyopia. Wait until aged 4 years before ptosis surgery.

Sticky watering eyes

A blocked nasolacrimal duct requires syringing and probing under endoscopic endonasal monitoring or dacryocystorhinostomy (DCR).
Vernal and atopic conjunctivitis: photophobia, swollen eyelids and itchy, stringy discharge that is worse in summer. History of atopy. Large giant papillae on tarsal conjunctiva and some small limbal lumps (limbal vernal). Treat with topical anti-inflammatory drops.
Blepharitis: red-rimmed sticky eyes with a tendency to recurrent chalazia, blepharoconjunctivitis and watering. Treat by eyelid cleaning and topical antibiotic ointment.

Severe Orbital cellulitis

Distinguish between pre-septal and post-septal orbital cellulitis when the child can be ill or febrile and requires admission.

Pre-septal cellulitis

Involves only the eyelids but can spread posterior to the orbital septum to become post-septal.
One or both eyelids are swollen and tender.
Involves a white eye which moves fully with no impairment of vision or proptosis.
Treat with intravenous (IV) antibiotics.

Post-septal cellulitis

Potentially severe life-threatening condition (cavernous sinus thrombosis), unless treated.
Painful orbital or eyelid red swelling and proptosis; child is feverish and unwell.
Associated with an upper respiratory tract infection and undiagnosed sinusitis.
May not be able to open eye to see limited eye movements.
Conjunctiva red and swollen.
Vision may be affected: reduced visual acuity and red desaturation with a relative afferent papillary defect due to optic nerve compression.
Do a computed tomography scan to exclude sinus disease and subperiosteal abscess, which need surgical draining and bacteriology.
Infection from Haemophilus influenzae, Streptococcus or Staphylococcus Gram-negative rods.
Urgent admission, blood cultures and treatment with IV antibiotics.

Teenagers

Teenagers have their own visual problems with the onset of myopia, presentation of Leber’s optic neuropathy, usually in the mid to late teens, ‘hysterical’ loss of vision, headaches and convergence insufficiency.