Dr Catt is one of approximately 12 doctors in NSW who have completed an international fellowship of at least one year for sub-speciality training in Paediatric Ophthalmology. She was the prize-winning Fellow during her training at the Hospital for Sick Children in Toronto, Canada, the second-largest pediatric research hospital in the world. She has a playful, gentle and thorough approach to her paediatric patients. Dr Catt gives children and their families the time they need to have their questions answered fully.
In addition to seeing paediatric patients in her private rooms in the Sydney CBD and at St Leonards, she is a consultant paediatric ophthalmologist at the Children’s Hospital at Westmead and the Neonatal Intensive Care Unit at Liverpool Hospital.
Conjunctivitis is one of the most common paediatric eye problems. It can be difficult to accurately distinguish the cause of the conjunctivitis and thereby initiate the correct treatment. Any conjunctivitis in a neonate is an ophthalmic emergency and should be referred to a paediatric ophthalmologist for assessment and treatment.
Most cases of viral conjunctivitis are caused by adenovirus. This DNA virus is also associated with upper respiratory infections and gastroenteritis and the conjunctivitis may occur in conjunction with these systemic diseases. The conjunctivitis is usually bilateral (often sequential), sometimes it is haemorrhagic, and the discharge is usually watery. A pre-auricular lymph node may be palpable. The diagnosis can be confirmed by taking a conjunctival swab for adenovirus PCR although this is usually not indicated. Some may elect to treat with a topical antibiotic (such as chloramphenicol, 1 drop, QID to both eyes) until the conjunctivitis resolves, to prevent a secondary bacterial infection. Older children who are not averse to using eye drops may get symptomatic relief from also using an over-the-counter preservative-free lubricating eye-drop as required. Most importantly, educate the family on strategies to minimize transfer within the family eg. hand washing before and after instilling eye drops, using separate towels etc. Being highly contagious, be sure to clean your hands and examination room thoroughly!
Bacterial conjunctivitis is very common in school-aged children, with Streptococcus, Haemophilus and Moraxella being the commonest causative organisms. Cases present with unilateral of bilateral conjunctival hyperaemia, purulent discharge and a history of the eyelids being sealed closed with discharge upon waking. Conjunctival swabs are usually not indicated as most cases resolve with a 10 – 14 day course of broad-spectrum topical antibiotics, used 4-6 times per day.
There are many subtypes of ocular allergy, all attributable to a Type 1 hypersensitivity reaction, with the following clinical features in common: Bilateral conjunctival injection and swelling with chronic, relapsing-remitting nature, possibly with seasonal recurrence and thick, ropy discharge. The upper tarsus may become covered in irregular lumps (giant papillae) and in more severe forms, the cornea can ulcerate. The most consistent feature and the symptom that is most highly suggestive is redness and itchiness. Not all will have a history of atopic disease as ocular allergy can exist in isolation. Treatment involves eliminating the offending allergen (if known) and reducing allergen concentration by washing the face, brows and lashes regularly. Topical mast cell stabilizers (eg. topical Olopatadine or Ketotifen, 1 drop BID both eyes) can be effective in preventing and treating seasonal flare-ups but they take 6 weeks to have their full effect and should not be used for longer than 3 months at a time. Topical steroids and topical immunomodulators are useful and should be prescribed after a comprehensive ophthalmological assessment including intraocular pressure assessment.
Another common eye condition I treat as a paediatric ophthalmologist is amblyopia. Amblyopia is defined as reduced vision that cannot be attributed to a structural abnormality of the eye or the visual pathway. It is an important diagnosis to consider in children because it is potentially reversible if it is identified and treated, early. Amblyopia has several possible causes including:
- Stimulus deprivation. For example, due to a cataract or ptosis that obscures the visual axis.
- Asymmetry of refractive error (anisometropia). For example, if the right eye has 2 dioptres of hypermetropia and the left eye has 5 dioptres of hypermetropia, the left eye is likely to become amblyopic.
The visual system in children is more ‘plastic’ than adults and amblyopia is the brain’s way of adapting (for example, to avoid double vision if the eyes are misaligned) or of being efficient (for example, by ‘shutting down’ the vision in an occluded eye). If identified in childhood, the plasticity of the visual system can be used to our advantage for treatment: when used in combination with treating the cause of the amblyopia, patching therapy forces the brain to ‘exercise’ the visual system of the amblyopic eye and can result in a significant improvement in vision. In children who do not tolerate a patch, atropine eye drops can be used to blur the vision in the good eye instead. Patching and atropine therapy should be initiated and supervised by an ophthalmologist as excessive treatment can result in unwanted side effects including ‘reverse amblyopia’ of the good eye. These treatments are most effective if initiated before the age of 7 years, but can have some effect after this.
Nasolacrimal duct obstruction is also common and fortunately does not usually threaten sight. The usual pathway for draining tears from the ocular surface starts at the punctum of the inner eyelid. Tears drain through the puncta into the upper and lower canaliculi, which empty into the lacrimal sac. The lacrimal sac drains into the nasal cavity via the nasolacrimal duct. Congenital nasolacrimal duct obstruction is common and may be identifiable at the 6-8 week baby check. It may be unilateral or bilateral and parents will notice the eye is sticky or watery every day. It is important to consider and assess for other causes of a watery eye in a neonate, such as congenital glaucoma, in which the cornea may appear cloudy and the child will be photophobic. Children with NLDO are not photophobic.
The majority (>90%) of congenital nasolacrimal duct obstructions resolve within the first year of life with conservative treatment, comprising massage of the lacrimal sac (see separate box). Topical antibiotics are not routinely required: they are only used if there is associated infection of the conjunctiva.
Those that do not resolve with conservative treatment may need probing of the nasolacrimal duct by a paediatric ophthalmologist. This is usually done within the first 12-24 months of life, requires a brief general anaesthetic and is often successful in opening the obstruction after a single procedure. If it recurs despite more than one successful probing, the nasolacrimal duct may require intubation with silicon tubing. The tubes are left in place for several weeks or months to help ‘stent’ the system open, at which stage they can be removed.
Complications of congenital nasolacrimal duct obstruction are uncommon. They can include conjunctivitis, a dacryocystocoele (a collection of sterile fluid in the lacrimal sac seen as a blue-coloured mass overlying the lacrimal sac in newborn babies) or dacryocystitis (infection of the lacrimal sac fluid collection). A dacryocystoceole may require probing in the neonatal period if it is not reducible, as the risk of developing a dacryocystitis is high. Dacryocystitis usually requires admission to hospital for intravenous antibiotics and may also require early probing.
Approximately 6 in 10,000 children are affected by cataract. Paediatric cataracts may be unilateral or bilateral, isolated or part of a systemic disease, congenital or acquired, familial or sporadic. Most familial cataracts are autosomal dominant so it is prudent to refer the children of patients with a history of congenital cataract for assessment within the first few weeks of life. Prompt diagnosis and management can avoid life-long vision impairment, which is why making an assessment of the red-reflex at the 6 week baby check is such a powerful clinical test. A dull red reflex, any asymmetry of the red reflex or any leukocoria requires urgent referral to an ophthalmologist. Management often involves surgical extraction followed by intraocular lens implantation and/or glasses and/or contact lenses.
Another common paediatric eye condition is strabismus, a term describing any condition where the visual axes of the eyes are not aligned with each other. Strabismus has implications for vision and visual function and may have significant implications for a child’s social development and opportunity. Strabismus often runs in families and is frequently associated with refractive error. The most common types of ocular misaligment are:
- Esotropia – the non-fixing eye deviates in, toward the nose (‘cross-eyed’)
- Exotropia – the non-fixing eye deviates out, away from the nose (‘wall-eyed’)
- Hypertropia – the non-fixing eye deviates up
- Hypotropia – the non-fixing eye deviates down
The causes of a strabismus are numerous but those seen most commonly in children are:
- Congenital esotropia. The esotropia in these children onsets before the age of 6 months. Because the angle of the turn is large, these babies will often use their left eye to look at objects on their right side and use their right eye to look at objects on their left side. This phenomenon, called cross-fixation, protects them from amblyopia because they are using the vision in each eye alternately. These children tend to have no significant refractive error and the treatment is surgical, before the age of 12-24 months.
- Accommodative esotropia. Children born with a high AC:A ratio will develop an esotropia which is larger when looking at objects that are close (for example, when looking at a book). These children usually present aged 18 months – 3 years and require treatment with glasses (sometimes with bifocal lenses) and sometimes surgery. Features of both refractive and accommodative esotropia often co-exist and the treatment will reflect this.
- Refractive esotropia. It is very common for children to be hypermetropic (far sighted) and in the absence of any other eye disease, low-grade hypermetropia is considered normal and does not need to be treated with glasses. Children’s eyes can accommodate much more strongly than adult eyes so children who have significant hypermetropia (³4 dioptres) are able to pull most objects into focus but in doing so, they activate the accommodation reflex very strongly which may cause their eyes to converge (esotropia). Correcting the refractive error with glasses reduces the size and the frequency of the turn but some may require surgery to straighten any residual esotropia.
- Intermittent exotropia. In this condition, one eye intermittently drifts out during times of visual inattention (‘day-dreaming’) or fatigue, or when looking off into the far distance. An associated feature is the child will close the affected eye in the sunshine as it drifts out. Parents will often comment that they notice their child closes one eye when they are looking across a park or playground. The frequency of the turn can worsen with age and it is reasonable to consider surgery if the eye deviates more than half of the day or if the turn is having an impact on the child’s social development. Glasses that force the child to accommodate more strongly may be a temporizing treatment strategy. In a smaller subset of patients, the eye will drift out when looking at objects that are close and these children can be helped by exercises prescribed by an orthoptist, such as ‘pencil push-ups’, which help to strengthen ocular convergence.
- Pseudo-strabismus. This is a common condition where the shape of the face or the conformation of the nasal bridge can give the impression that the eyes are misaligned. A cover test will demonstrate that the eyes are actually well aligned. This is particularly common in young children of Asian familial origin. It becomes less obvious as the child grows and the nasal bridge becomes higher.
- Duane’s syndrome. This is a cranial misinervation syndrome where the nerve supply to the lateral rectus muscle (usually supplied by the 6th cranial nerve and responsible for ABducting movements of the eye) doesn’t develop normally. The effects are multiple but the characteristic feature in all cases is retraction of the eyeball into the orbit (enophthalmos) causing the upper eyelid to drop slightly (pseudo-ptosis), on attempted ADduction of the affected eye.
- Brown’s syndrome. The tendon of the superior oblique muscle, responsible for elevating the eye when it is ADducted, passes through a bony and ligamentous pulley called the trochlea, which is located in the antero-supero-nasal orbit. In Brown’s syndrome, there is a mechanical restriction of the tendon’s movement through the trochlea. This results in failure of the eye to elevate when it is in the ADducted position.
- Sensory esotopia. An eye that sees poorly will usually become strabismic, regardless of the cause of the poor vision. All children with strabismus require a thorough examination to exclude a sensory cause, such as cataract or retinoblastoma. Although we do not fully understand why, children usually become esotropic in the context of reduced vision, whilst adults become exotropic.
- Congenital exotropia. Congenital exotropia refers to a constant exotropia present before the age of 6 months. It is rare in otherwise healthy infants. Many children with a constant exotropia have associated neurological or craniofacial disorders. Early surgical management may have a role in some cases.
- Nerve palsies. The extraocular muscles are controlled by cranial nerves III (the Oculomotor nerve, supplying the medial rectus, inferior rectus, superior rectus and inferior oblique muscles) IV (the Trochlear nerve supplying the superior oblique muscle) and VI (the Abducens nerve, supplying the lateral rectus muscle). In children, nerve palsies may be congenital or acquired. Acquired causes of a 3rd cranial nerve palsy in children include severe head trauma, central nervous system inflammation or neoplasm and migraine. A 4th nerve palsy is more commonly congenital and often presents with an altered head posture (the head tilts away from the affected side) but may also follow a closed head injury, even a mild one. A 6th nerve palsy may be related to infectious or inflammatory causes but in approximately one third of children it is associated with an intracranial mass lesion. The 6th nerve palsy is frequently the result of raised intracranial pressure.