Clinical update Treatment of amblyopia A Dr Steve Colley, Ophthalmologist. Tel 9385 6665. mblyopia (Greek amblys “dim” ops “eye”) is reduced vision due to abnormal wiring of the visual cortex as a result of impairment to the visual experience of one or both eyes. Amblyopia affects 2% of the population. It is readily treatable, if detected early. The typical pathologies that result in amblyopia include refractive error (blurring), strabismus (misalignment) and, less frequently, deprivation (cataract, ptosis, vitreous haemorrhage). The rationale for treatment is to improve visual function, not only to provide a useful “spare eye” but also to prevent limiting career opportunities. Although it is important to treat amblyopia as early as possible, some studies suggest children will respond to treatment even after the critical first seven years (and some children even as teenagers). Strabismic amblyopia This is the most common type of amblyopia. The deviating eye most commonly turns in (esotropia) or out (exotropia), and is suppressed in order to prevent double vision. This suppression can become so effective that the affected eye loses its visual potential. The diagnosis becomes difficult when the deviation is small and thus is not obvious. The cover test is essential in diagnosing this condition. Refractive amblyopia This is the most difficult type of amblyopia to detect. If the two eyes have significantly different refractive states, the young child may rely on the sight of the more focused eye, causing the other eye to lose its visual potential. The child will appear to have normal vision because the better eye is being used for visual tasks. If both eyes are out of focus, both may become amblyopic. Cycloplegic retinoscopy is essential for diagnosis and to determine the correct spectacles for treatment. Deprivation amblyopia This usually causes the most severe vision loss. It typically affects children with unilateral or bilateral congenital cataracts but also may occur in those with corneal or vitreous opacity or severe ptosis. The lack of a red reflex on ophthalmoscopy or even standard photography should be taken seriously. Atropine has shown to be as effective as patching treatment for moderate amblyopia and may only require instillation once a week. Systemic side effects are possible. Frequent follow-up is suggested as 25% of patients may experience a reduction of vision within 12 months of cessation of treatment. Failure of a child to respond to treatment may be due to poor compliance but it should also trigger further examination, and if no obvious cause is found, then electrophysiology or neuro-imaging should be considered. Treatment An organic cause for vision loss must be ruled out, and any obstacle to vision treated (e.g. cataract). Congenital cataracts must be removed as soon as possible and aphakic treatment (contact lens or glasses) instigated. Significant refractive errors need to be corrected (particularly anisometropic hypermetropia – unilateral long-sightedness). Studies have shown it may take as many as five months for visual improvement to maximise with corrective spectacles. If residual amblyopia persists then penalisation therapy, in the form of patching of the ‘good eye’or atropine drops, is warranted. It is important to remember that the majority of treatment is carried out by the parents of the affected child and that it can be difficult and time consuming, making compliance a real issue. Contemporary randomised trials have shown that significantly less patching than was previously advocated, can be just as effective. In moderate amblyopia (6/12-6/24). two hours a day is advocated, while with severe amblyopia (6/30-6/120) six hours per day is now considered appropriate. Declaration: Perth Eye Centre Pty Ltd, being the management company for the Eye Surgery Foundation, has supported this clinical update through an independent educational grant to Medical Forum. Author – no competing interests. Fact Box • Amblyopia is the most common form of monocular vision loss in children (and young adults). • Early recognition and prompt treatment are essential in preventing permanent vision loss. • Most treatment is delivered by the child's parents, and may be arduous for them. Fortunately, contemporary management regimes have lessened that burden. • Relapses are common and failure to respond may suggest other pathology, so close follow-up is important. 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