Arch Dis Child: first published as 10.1136/adc.64.3.413 on 1 March 1989. Downloaded from Archives of Disease in Childhood, 1989, 64, 413-418 Personal practice The management of squint A R FIELDER Department of Ophthalmology, University of Leicester Medical School, Leicester Squint may be the first sign of a serious ocular or early neonatal life about 32% of infants are diver- systemic disorder, and yet it is also one of the most gent and only 3% convergent.4 As the incidence of common ocular conditions of childhood. It follows divergence is higher in preterm neonates it is likely that while most ocular deviations have no such that during development the eyes are initially sinister connotations, an understanding of the range divergent but that this resolves over the first few of associations is essential to be prepared for this weeks of life. comparatively infrequent but important possibility. Apart from those seen in the neonatal period, Screening for squint has been covered recently' squints are comparatively uncommon in the first few and in this article its presence will be assumed. The months of life, and the term 'infantile' is preferred clinical evaluation of the child with a squint will be to 'congenital' because this type of esotropia is considered first, followed by a discussion of the aims rarely if ever congenital but develops between 3 and and methods of treatment. The main thrust will be 6 months of age. Characteristically the deviation is directed towards the squint itself, but as amblyopia large, constant, and there is no appreciable refrac- is such a frequent and important association this tive error.5 topic will also be covered briefly. In order to avoid Apart from the infantile type, the onset of extensive and tedious repetition the associations of esotropia in childhood is most common between 11/2 squint will be listed using a predominantly system and 3 years of age. The deviation may range from based approach. Subdivision into paralytic and non- the hardly detectable (microtropia) to the cosmeti- paralytic types is only done at a later stage as both cally obvious manifest squint, and may be intermit- http://adc.bmj.com/ may occur in certain categories. Inevitably this tent or constant. In some the deviation increases- classification has limitations and inaccuracies, but or is only present-on accommodation (partially hopefully it will help the paediatrician to consider and fully accommodative squints respectively). the possible implications of a squint. For further Many, but by no means all, are associated with reference the reader may wish to consult two refractive errors. excellent standard texts.2 3 Exotropia is less common than esotropia at all ages and has less propensity to cause amblyopia. In Squint and its associations infancy ocular divergence should alert the clinician on October 1, 2021 by guest. Protected copyright. to the possibility of a severe visual impairment. SQUINT AS AN ISOLATED ANOMALY Paralytic squints do occur as an isolated anomaly Recently emphasis has been placed on early referral in an otherwise healthy child, but a careful search of infants and children with squint, but this has not for an underlying cause must always be undertaken taken into account that during the neonatal period (see acute central nervous system disease). Most, such a deviation may be a normal event. During but not all, paralytic squints in children are con- genital rather than acquired, although the role of birth trauma as a causal factor has probably been greatly overemphasised. A sixth cranial nerve palsy In terms will be used this article the following may present at this interchangeably: squint and strabismus, esotropia birth but characteristically and convergent squint, exotropia and divergent resolves over the ensuing few weeks. Apart from squint, comitant and non-paralytic squint, and this clinically obvious and rare exception, the most incominant and paralytic squint. Comitance will be common palsy, of the fourth nerve, is usually not assumed unless the terms incominant or paralytic diagnosed for a year or so as the ocular deviation is are used. difficult to elicit in infancy and the presenting sign is usually a compensatory head posture. Third nerve 413 Arch Dis Child: first published as 10.1136/adc.64.3.413 on 1 March 1989. Downloaded from 414 Fielder palsy is less common but more obvious, and in may be unilateral, bilateral, and concomitant or children is more likely to be congenital than acquired. paralytic, or both. Causes include raised intracranial A form of the latter that usually commences in pressure, intracranial tumours, trauma, degenera- childhood is ophthalmoplegic migraine. Benign tive and inflammatory diseases.6 12 recurrent sixth nerve palsy, thought to be a post- infective mononeuropathy as it usually follows a Neurodevelopmental disorders-In general, the inci- febrile illness, is included here because at presenta- dence of ocular abnormalities in children with tion there are no associated systemic or neurological neurodevelopmental disorders including Down's signs.6 In the superior oblique tendon sheath syn- syndrome and cerebral palsy ranges from about 40% drome (Brown's syndrome) elevation of the eye in to 90%.12 Of these squint is the most common with adduction is limited. The aetiology of this condition an average incidence of about 40%,12 15 depending may differ between cases from a congenital anomaly both on patient selection and the nature of the of the tendon sheath to an acquired swelling of the neurodevelopmental disorder. Although both comi- tendon. tant and incomitant deviations occur the former are far more common. SQUINT AND OCULAR DISEASE Squint may be the presenting sign of serious ocular Brain stem dysfunction-Two conditions need to be disease. The eyes of a blind infant are commonly, considered in this category: Duane's and Mobius' but not invariably, divergent. Most important, syndromes. Duane's syndrome is relatively common squint either convergent or divergent may be the and superficially resembles a sixth nerve palsy and first sign of a treatable and potentially life threaten- its identification can obviate the need for extensive ing condition such as retinoblastoma. Thus squint investigation Often an isolated anomaly, it can be can be associated with unilateral or bilateral ocular associated with other congenital abnormalities such disease, including cataract and retinal disorders such as Goldenhar's syndrome, spina bifida, and deafness. as regressed retinopathy of prematurity (see below). Mobius' syndrome is either a developmental defect Esotropia also develops in some children with or an acquired hypoxic insult to the cranial nerve congenital nystagmus. nuclei and is characterised by bilateral facial weak- ness, horizontal gaze palsies, and esotropia in some SQUINT AND SYSTEMIC CONDITIONS cases. Affected children are usually mentally re- Many systemic conditions can be associated with tarded, deaf, and exhibit limb malformations. strabismus and it would not be sensible or indeed possible to list them all here. Instead only a few will Muscle disease http://adc.bmj.com/ be considered and these will be grouped into broad Uncommon in routine clinical practice and can categories. easily therefore be misdiagnosed. Extraocular muscle involvement in myasthenia usually involves Prematurity the levator muscle of the eyelid resulting in ptosis The incidence of comitant squint is increased in and may also affect any other extraocular muscle infants born prematurely with figures quoted from leading to diplopia. Characteristically myasthenic -9 with and the can be 11% to 19%. The pathogenesis of this association symptoms increase fatigue signs on October 1, 2021 by guest. Protected copyright. is not well understood but is almost certainly due in unilateral or bilateral. Ocular motility hIay be part to both the perinatal neurological insults and affected in other muscle disorders and esotropia retinopathy of prematurity to which these infants may occur in myotonia congenita. Ophthalmoplegia are susceptible. A high incidence of squint has also is seen in a number of muscle disorders including been reported in term and preterm infants who congenital and other myopathies, dystrophia myo- have had phototherapy for the treatment of tonia and mitochondrial cytopathy. As in these last hyperbilirubinaemia,l° but a causal relationship mentioned conditions the limitation of ocular move- between these two and squint has not been defined ments is usually symmetrical, diplopia is not a particularly as many of these babies will also have common symptom. Rarely only the extraocular suffered the aforementioned complications. muscles are involved as in the congenital fibrosis syndrome. Disorders of the central nervous system Acute diseases of the central nervous system-The ORBITAL CONDITIONS association between squint and acute serious disease In this group of conditions certain ocular move- of the central nervous system is well known, and it ments are limited, due not to a neurogenic cause, must always be remembered that it may be the first but to mechanical restriction of the muscle move- sign of serious neurological disease. The deviation ment. Examples include injury such as orbital blow Arch Dis Child: first published as 10.1136/adc.64.3.413 on 1 March 1989. Downloaded from The management of squint 415 out fractures and infections. Squint may be the first caution as children can confuse physiological and sign of an orbital tumour such as rhabdomyosarcoma. pathological diplopia. The term diplopia is also sometimes used to describe blurred vision, as in the Investigation uncorrected myope. As children relatively rarely complain of diplopia, indirect evidence such as Even now the evaluation of a squint, and its. effect closing one eye when looking in a particular on the visual system, remains essentially clinical. direction can be helpful. Often there is a disparity The obvious priority is to identify first those con- between history and findings concerning the follow- ditions that require urgent treatment, and inves- ing signs: squint, ptosis, compensatory head pos- tigation should consequently be directed initially ture, proptosis, and pupil inequality.