Approach

Offer treatment to all children with amblyopia, regardless of age (especially if not treated previously), even though success rates decline with increasing age. Preferred treatment will depend on the child's age, amblyopia subtype, and severity.[1]​​​[56]

The goals of treatment are:[1]​​​[56]

  • To correct any cause of visual deprivation

  • To correct refractive errors likely to cause blur

  • To promote use of the amblyopic eye to improve visual acuity.

Start by ensuring treatment and ongoing management of the underlying cause. Treating the refractive error alone can improve visual acuity in anisometropic, strabismic, or combined amblyopia, whether unilateral or bilateral. Patching and atropine penalisation of the better-seeing eye is usually sufficient to promote use of the amblyopic eye, and for moderate cases (20/40 to 20/80) can be limited to just 2 hours/day or weekend use, respectively. Once maximal visual acuity is obtained, taper and stop ongoing treatment.

Mild to moderate strabismic and/or mild to moderate anisometropic amblyopia (visual acuity better than 20/100)

All types of amblyopia require optical correction of significant refractive errors if present. For mild to moderate anisometropic (unequal refractive error between the two eyes) amblyopia, the first-line treatment can be spectacles alone.[57][58] Guidelines for prescribing eyeglasses to treat amblyopia in young children depend on patient age and other risk factors. Clinicians should be aware of the importance of good adherence to glasses wearing, in addition to other forms of treatment, especially during optical treatment alone, as it has been found that adherence to glasses wearing is highly variable and affects visual outcomes.[59]

If amblyopia does not resolve with spectacles alone, either patching or atropine is an acceptable additional treatment. Improvement in visual acuity can be allowed to plateau before atropine or patching is introduced. This first phase works gradually and is called 'optical treatment' or 'refractive adaptation', with studies suggesting that visual improvements from this treatment may continue for up to 30 weeks.[57][58][60]​​[61][62]​ It has been suggested that the improvement in visual acuity in the amblyopic eye is considerable at 4-12 weeks and then reaches a plateau, after which it only improves slowly.[57] In general, the recommended time length to achieve the maximum outcome of refractive adaptation is 18-22 weeks.[61] Further research is required to determine when additional treatment should be implemented. The decision about which additional treatment to use needs to be made after discussion with the parents.

Patching

Patches are used to occlude the eye with better vision. They are usually stuck directly onto the periorbital skin. They can be stuck to the spectacle lens, although the child will then be able to look around the sides. One study found a favourable response when 2 hours of daily patching was compared with the continuation of spectacles alone in children (3-7 years of age) with mild to severe strabismic and/or anisometropic amblyopia.[63]​ It confirmed that there is benefit in adding patching to spectacles in children with residual amblyopia, once visual acuity has stabilised with spectacles alone. Different durations of occlusion with patching have been compared. Patching for 2 hours/day has been found to result in an equal treatment response after 4 months when compared with patching for 6 hours/day in this group.[64]

[Figure caption and citation for the preceding image starts]: Treatment of amblyopia with spectacles and patchingFrom the collection of Tina Rutar, MD [Citation ends].com.bmj.content.model.Caption@159f34f6

Compliance with patching is an important issue to consider when interpreting the results of trials. Poor initial visual acuity has been found to be associated with poor compliance with patching.[65] There is evidence for a dose-response relationship between actual patching duration and amblyopia treatment response.[65][66]​​[67]​​ In one randomised trial, increasing daily patching dosage to 6 hours resulted in greater improvement in visual acuity in patients who ceased to improve with 2 hours of daily patching.[68] One trial comparing 6-hour with 12-hour prescribed patching found no significant difference in the amount of patching received by either treatment group.[66] The study results suggested a dose-response relationship with up to 4-5 hours of actual daily patching, although older children (particularly those over 6 years of age) required more patching than younger children.[66] Randomised controlled trials have shown the benefit of using interventional materials to improve treatment compliance in poorly adherent subjects and in children of non-native parents who speak the host country language poorly.[69][70]​​​

Atropine

Atropine eye drops to blur the vision in the better eye (atropine or optical penalisation therapy) are sometimes used as an alternative to patching. Patching and atropine penalisation are equally effective, and visual benefits of treatment are maintained in the long term.[71][72]​ Different atropine regimens have been compared. An equal treatment response has been demonstrated with daily atropine compared with weekend-only atropine or two consecutive days.

Plano lens in the atropinised eye

A plano lens blurs the sound atropinised eye more than a typical refractive correction. There may be a small additional benefit of a plano lens in patients undergoing weekend atropine penalisation.[73]

Other types of optical penalisation

The eye can be penalised by using a lens higher than the patient's refractive error. The induced hyperopia blurs vision primarily at distance. One randomised trial comparing twice-weekly atropine to full-time use of a plus lens in the sound eye in children aged 2-10 years for the treatment of mild strabismic and/or anisometropic amblyopia found a superior response with atropine after 6 months.[74] However, relatively mild optical penalisation was used in this study. Due to the limited evidence for this treatment, it is not generally recommended. In practice, it may be used for a patient who refuses patching or is intolerant to atropine but accepts wearing spectacles or contact lenses that incorporate optical penalisation.

After the amblyopia has been treated, children with residual strabismus typically undergo strabismus surgery.

Severe strabismic and/or severe anisometropic amblyopia (visual acuity of 20/100 or worse)

All types of amblyopia require optical correction of any significant refractive errors if present. Children with severe strabismic and/or anisometropic amblyopia are likely to require additional treatment.[57][58] Patching is the more traditional additional treatment, although preliminary studies suggest that atropine is also effective.[75]

Adding patching to spectacles, after visual acuity has stabilised with spectacles alone, is beneficial in this group.[63] Patching for 6 hours has been found to be equally effective to patching full time.[76] Compliance with patching needs to be taken into consideration. Patching for just 2 hours also improves visual acuity in severe amblyopia, although the magnitude of improvement may be less than with more robust patching regimens.[77] Until additional trials have been performed to compare prescribed 2-hour versus 6-hour patching regimens for severe amblyopia, it may be sensible to initially prescribe 6 hours of patching for severe amblyopia.[77]

After the amblyopia has been treated, children with residual strabismus typically undergo strabismus surgery.

Bilateral ametropic amblyopia

A prospective study evaluated the response to spectacle treatment for bilateral ametropic (high and similar refractive errors in both eyes) amblyopia in children aged 3-9 years. Mean binocular visual acuity improved from 20/63 at baseline to 20/25 at 1 year.[78] This study confirmed that ametropic amblyopia often resolves with spectacle treatment alone.

Form-deprivation amblyopia

Early surgery is recommended when the cause of amblyopia is obstruction of the visual axis, such as corneal opacity, cataract, non-clearing vitreous haemorrhage, or severe ptosis. Surgical intervention is less urgent when the form deprivation occurs bilaterally as opposed to unilaterally. Deprivation amblyopia may co-exist with other forms of amblyopia, including anisometropic and strabismic. These should be addressed in conjunction with treatment to clear the visual axis.

To maximise visual outcomes, surgery for bilateral congenital cataracts should be performed before 14 weeks of age and earlier if possible, and surgery for unilateral congenital cataracts should be performed before 6 weeks of age.[79][80] For patients with unilateral or asymmetric amblyopia, such as children with unilateral congenital cataract, patching is a necessary adjunctive treatment.

Residual strabismic or anisometropic amblyopia

After treatment of moderate amblyopia resulting from strabismus or anisometropia with refractive correction and 2 hours of patching, some patients have residual amblyopia. A randomised clinical trial evaluated the effectiveness of increasing prescribed daily patching from 2-6 hours in children with stable residual amblyopia. Increasing patching to 6 hours was more effective than continuing patching at 2 hours daily, with a modest 1.2-line compared with 0.5-line additional visual acuity improvement.[68] This study brings into question whether 2 hours of prescribed daily patching is truly enough or optimal in the treatment of moderate strabismic and anisometropic amblyopia.

Refractory amblyopia (non-compliant patient)

Refractory amblyopia in a non-compliant patient can be treated by closing the eyelid over the better-seeing eye temporarily, using surgical or medical techniques. These include the use of sutures, injection of botulinum toxin to the levator muscle, and application of cyanoacrylate glue to the eyelid margin.[81][82] However, carers might be hesitant to use these techniques for the management of amblyopia in view of the need for anaesthesia, as well as the cosmetic and psychological effects on the child. Other less invasive ways to improve compliance include the use of interventional materials, such as cartoons or information booklets. Randomised controlled trials have shown the benefit of using interventional materials to improve treatment compliance in poorly adherent subjects and in children of non-native parents who speak their host country language poorly.[69][70]

Older children (>7 years)

Although the treatment for amblyopia is more likely to produce a better response in children <7 years, there is evidence that older children (aged 7-12 years) respond partially to amblyopia treatment with spectacles, atropine, and patching, and that visual benefits are maintained in the long term.[83][84]​ The treatments do not differ for older children (at least to age 15 years), although the exact regimens may vary.[1]​​​ Patching (initially 2 hours/day, increased for non-response to 4 hours/day) has been compared with weekend atropine (increased to daily for non-response) in children aged 7-12 years with mild to moderate amblyopia. After 4 months, both groups showed similar modest gains in visual acuity of approximately 1.5 lines.[85]

Full-time patching has been compared with daily atropine therapy in 8- to 20-year-old patients with anisometropic amblyopia and visual acuity 20/40 to 20/200. Patients were initially treated with 6 weeks of spectacle correction. After 6 months of treatment, visual acuity improved 2.3 to 2.4 lines in both groups.[86]

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