Strabismus |
CONGENITAL strabismus syndromes — such as congenital esotropia , congenital exotropia , congenital nerve palsies , Duane syndrome and Brown syndrome — will be evident in the first year of life . Variable , intermittent strabismus is very common in newborns up until the age of 16 weeks . Thereafter , any form of strabismus is not normal and should be assessed by an ophthalmologist . |
Esotropia . |
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Congenital esotropia Congenital esotropia is a constant , large-angle convergent strabismus , which starts before six months of age . Children with this condition will often ‘ crossfixate ’. They will use their convergent right eye to look at objects on their left and their convergent left eye to look at objects on their right . This alternation of fixation between their right and left eyes may protect them from developing amblyopia .
Treatment is primarily surgical and usually involves recessing each medial rectus muscle posterior to its original insertion ( to weaken its action ) between the ages of 12 and 24 months . Because of the large angle , up to 30 % of children require a second operation to fully correct the strabismus . Occasionally , spectacles and part-time occlusion therapy are also used .
Pseudo-esotropia This is a common differential diagnosis of a true esotropia in early childhood . In pseudo-esotropia , the ocular alignment is intact , but the shape of the face and eyelids gives the appearance of an esotropia . This is common in young children because , compared with older children , they have flatter nasal bridges and wider epicanthic folds , giving the impression of a convergent squint .
The proof is in a cover test —
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VARIABLE , INTERMITTENT STRABISMUS IS VERY COMMON IN NEWBORNS UP UNTIL THE AGE OF 16 WEEKS . |
a truly deviated eye will move to take up fixation ; in contrast , it will stay steady in a pseudo-esotropia . A positive stereopsis test result ( which measures depth perception ) proves good ocular alignment .
Cover and stereopsis tests are difficult to perform in young children , and given the potential for a poor outcome if a true strabismus is dismissed or missed , it is always appropriate to refer these children for a complete ophthalmic assessment . Given the incidence of a true esotropia is higher in children previously diagnosed with a pseudo-esotropia , it is my practice to examine these children on two separate occasions , unless I can prove they have stereopsis .
Congenital exotropia This is an uncommon condition . It is a large angle , constant divergent squint , which starts before six months of age . It is generally associated with ocular and systemic conditions including prematurity , cerebral palsy , seizure disorders and chromosomal anomalies .
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Congenital nerve palsy The most common congenital nerve palsy affects the trochlear ( fourth ) nerve . This nerve supplies |
the superior oblique muscle , which is responsible for elevating the eye when it is in the adducted position . A palsy of this nerve causes the affected eye to become hypertropic , especially when it is the adducted position , and also causes the eye to excyclotort ( where the ‘ 12 o ’ clock position ’ of the eye rotates towards the temple ).
In order to avoid double vision and to continue using both eyes together , children with this condition may develop a head tilt or head turn away from the affected side . This will become apparent only after the child learns to sit up independently .
Duane syndrome Duane syndrome is a cranial misinervation syndrome in which the sixth cranial nerve fails to develop properly and cannot innervate the lateral rectus muscle . It instead receives an anomalous branch of the third cranial nerve . The affected eye cannot move fully in all directions and some movements will cause the globe to retract and a ptosis to be induced . Strangely , the left eye is affected much more frequently than the right .
Surgery is occasionally useful if the condition is associated with
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a strabismus in the primary position , a significantly altered head posture , or if the globe retraction is troublesome . In the absence of surgery , any associated refractive error and amblyopia is managed , and children will often develop compensatory head postures to give themselves better binocular function and to improve the cosmesis of their ocular alignment .
Brown ’ s syndrome This may be congenital or acquired and is rare in the first year of life . It is caused by a mechanical restriction of the superior oblique muscle through the trochlea , a bony and tendinous pulley in the superonasal orbit . The eye cannot elevate in adduction .
Children will compensate for this by lifting their chin and turning their head away from the affected side . This will only become apparent when they have learned to sit up independently . Surgery is only occasionally performed for this condition .
Treatment is usually not required unless the onset is sudden ( acquired ). In those circumstances , oral NSAIDs and peritrochlear steroids can be trialled .
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Retinoblastoma |
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WHILE rare , retinoblastoma is the most common malignant ocular tumour of childhood , caused by a mutation in the RB1 gene ( a tumour suppressor gene ).
In familial / hereditary cases , the child is born with a mutation in one copy of the RB1 gene . A mutation in the second copy of the RB1 gene in an immature retina cell results in the development of a retinoblastoma . Because the second mutation is a relatively common event , the usual pattern is for multiple tumours to develop in both eyes .
Familial cases often present within the first year of life and tumours may even be present before birth .
Because children with a hereditary or germline RB1 mutation have the mutation in every cell of their body , they are at high risk of developing other tumours , such as sarcomas , breast cancer , lung cancer and lymphoma . For this reason , radiation in the form of CT scans or X-rays to any part of the body should be avoided in these patients . MRI and ultrasound are
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the preferred imaging modalities .
In non-hereditary cases , a single cell needs to undergo a mutation in both of its RB1 genes . Because this is a relatively rare event , non-hereditary cases tend to be unilateral and tend to present after the first year of life , but usually before the age of 3-5 .
The most common presenting sign of retinoblastoma is leukocoria or photoleukocoria ( a white pupil or asymmetry of the red reflex on flash photography or ophthalmoscopy ) ( see figure 6 ), followed by strabismus . Any sign suggestive of retinoblastoma should be referred urgently to an ophthalmologist .
Retinoblastoma is managed with a multidisciplinary approach and treatment may include enucleation , laser or cryotherapy to intraocular tumours , local and systemic chemotherapy . Genetic counselling , nursing support , social work and play therapy are essential components of the multidisciplinary approach . cont ’ d next page
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Figure 6 . Retinoblastoma . Source : Meilahti Hospital , Department of Ophthalmology bit . ly / 2qrXjdd |