After reading this chapter you should be able to assess, diagnose and manage:
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visual impairment
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proptosis and ptosis
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strabismus and nystagmus
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glaucoma, papilloedema, eye tumours and cataract
Eye and vision disorders affect 10% of otherwise healthy UK children but are much more prevalent in children with underlying neurological or systemic conditions. Eye anomalies often occur as part of a genetic syndrome and may aid recognition of an underlying systemic diagnosis. The early detection and management of childhood ophthalmic conditions is important to prevent lifelong visual impairment.
Vision in childhood
Eye and vision screening programmes
Visual neuroplasticity is at its most critical and malleable in the first 3 months of life and gradually declines over the first decade. Unless rapidly addressed, poor quality visual input during this period will result in abnormal neuronal development and permanent visual impairment due to amblyopia.
The impairment can be caused by:
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visual deprivation—as seen with infantile cataract or ptosis
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retinal image blur—if there are uncorrected refractive errors
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visual suppression from one eye—due to strabismus-producing diplopia
The eye and vision screening programmes in the UK are designed to detect the conditions that cause amblyopia at two time points:
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newborn and infant physical examination (NIPE)
This checks for the presence of the red reflex within 72 hours of birth and at 6–8 weeks, primarily to enable management of congenital cataract within the critical period.
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4- to 5-year school vision screening—test of each eye to enable management of amblyopia within the period of neuroplasticity
Visual development and visual impairment
Vision is a multifaceted sense comprising:
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visual acuity (resolving power)
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peripheral vision
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colour and contrast sensitivity
The neuronal cells forming the visual pathway continue to mature after birth and visual function reaches adult levels by 4–5 years of age. In the U.K., nearly 4% of the childhood population are registered severely visually impaired or blind (compared to 12% in resource-poor countries), and half these children will have additional motor, sensory, learning impairments or systemic disease. The screening programmes, and access to specialist paediatric ophthalmic care, prevent many children from developing severe visual impairment, and consequently the majority (75%) of those who are registered blind have an unpreventable and untreatable cause. The most common cause of childhood visual impairment in resource-rich countries is cerebral visual impairment and in resource-poor countries is cataract. Visual impairment certification may be based on reduced visual acuity, restricted visual field or a combination of the two ( Table 28.1 ).
| Structure | Features to assess |
|---|---|
| orbits and eyelids | – symmetry of the orbits and presence of proptosis which is more obvious if viewed from above symmetry of the eyelid height – a ptosis that covers half or more of the pupil will be amblyogenic |
| eye alignment and movement | – symmetry of the corneal light reflections to a pen torch – elicited eye movements to a toy or torch – cover test for near and distant targets – assessment of nystagmus |
| globe and pupil | – symmetry of globe size, assessment of corneal diameter and clarity – pupil symmetry, shape and response to light – presence of a relative afferent pupillary defect |
| ocular media | – red reflex assessment with ophthalmoscope |
| fundus | – ophthalmoscopy of the optic nerve head and macula |
Testing visual function
Most children over 6 years old can use an adult visual acuity chart such as a Snellen chart. Viewing distance is important; standard Snellen charts are viewed from 6 metres, and at this distance the child should be able to resolve letters down to line 6 (6/6 or 20/20 vision). The child who is only able to resolve the top letter will have 6/60 vision (a person with “normal vision” would be able to see this letter from 60 metres away).
Many specialists now use logMAR visual acuity notation, and 0.00 logMAR is equivalent to 6/6 visual acuity and 1.00 logMAR is equivalent to 6/60. Specialist charts are usually required for visual acuity testing in young children, although digital apps using symbol charts can be helpful.
Assessment of the red reflex
This examination should be performed whenever a child is seen with visual symptoms or ocular signs. Its prime function is to detect treatable opacities in the ocular media such as cataract and retinoblastoma.
Abnormal ophthalmic findings
Proptosis
Proptosis is abnormal forward displacement of the globe and indicates either insufficient space within the orbit or an acquired increase in the volume of intraorbital tissue. The globe may be nonaxially displaced away by an orbital mass, whereas an axial proptosis suggests a mass within the muscle cone of the orbit. Proptosis may be easier to detect if the child’s face is viewed from above, and objective assessment is possible by measuring the horizontal distance from the lateral orbital ridge to the corneal surface of each eye using a ruler.
Causes of proptosis
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congenital—craniosynostosis; encephalocele; dermoid
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inflammatory—orbital cellulitis; myositis
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neoplastic—haemangioma; rhabomyosarcoma; neuroblastoma; optic nerve glioma
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traumatic—orbital haematoma; complex orbital facture
Orbital cellulitis requires urgent intravenous antibiotic therapy and treatment should not be delayed, but an atypical presentation or failure to improve on antibiotics warrants orbital imaging and further investigation. Rhabdomyosarcoma causes a rapidly progressive, non-axial proptosis, associated with pain and inflammation of the periocular tissues which may mimic orbital cellulitis. Orbital biopsy may be required if neoplasm is suspected. Proptosis can lead to a compressive optic neuropathy or amblyopia, given that many of the patients present at a young age.
Treatment and management
All children should have specialist referral since proptosis can lead to corneal exposure which, if untreated, can lead to corneal ulceration and perforation. Regular lubrication, lid taping or a tarsorrhaphy may be necessary to protect the cornea
Ptosis
Ptosis is drooping of the upper eyelid which may be unilateral, bilateral and asymmetrical and can be congenital or acquired.
Causes of ptosis
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congenital
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isolated congenital levator muscle dysgenesis (most common cause)
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congenital myasthenic syndromes
Clinical Scenario
A 3-year-old girl presented with a 4 day history of headache, polydipsia and polyuria and 1 day history of bulging of her right eye. She had previously been well and there was no history of trauma. Past medical and family history revealed nothing of relevance. Immunisations were up to date.
Examination showed that she was quiet and withdrawn but responsive to her parents’ commands. She was apyrexial, heart rate 100 and BP 90/65. She had an obvious proptosis to her right eye which was evident when viewed from above. There was no obvious orbital erythema. Her pupils were equal and reactive to light, there was no relative afferent pupillary defect.
An urgent referral was made to paediatric ophthalmology. A nonaxial proptosis and limitation of ocular motility was identified. Formal visual acuity assessment was not possible but the child could fixate and follow small toys when the left eye was occluded. Fundoscopy was difficult and inconclusive.
Initial investigations including urea and electrolytes were undertaken and showed: sodium148(135–146 mmol/l)
potassium4.9(3.5–5.3 mmol/l)
urea5.5(2.5–6.5 mmol/l)
creatinine85(13–39 μmol/l)
glucose5.2(3.0–6.0 mmol/)
Serum osmolality was 295 mOsmol/kg and urine osmolality 130 mOsmol/kg. These findings indicate diabetes insipidus. An urgent MRI scan was obtained and demonstrated a mass in the pituitary fossa extending into the orbit and multiple lytic lesions in the skull.
These findings suggested a diagnosis of Langerhans cell histiocytosis, and biopsy of the orbital mass confirmed this. Further staging was undertaken and the child started on intensive systemic therapy. A full recovery was obtained. The absence of a relative afferent pupillary defect suggested a good visual prognosis, and full visual function was reestablished following a period of amblyopia therapy.
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