Treatment of amblyopia (lazy eye) caused by strabismus (squint) with patching or optical treatment (glasses or penalisation) or both

Review question: Treatment of amblyopia (lazy eye) caused by strabismus (squint) with patching or optical treatment (glasses or penalisation) or both.

Background: Amblyopia is a common childhood condition which causes a reduction in vision of one or both eyes which is not caused by any eye disease. Amblyopia can be caused by the presence of a squint (misalignment of the eyes where one eye may turn inwards, outwards, upwards or downwards). This review aims to look at the treatment of reduced vision caused by the presence of a squint, not the treatment of the squint itself.

Search date: Searches were last run 30 January 2014.

Study characteristics: Three randomised controlled trials (RCTs) conducted in the United States were included in this review.

Key results: The results of one of these trials indicate that patching therapy combined with any necessary glasses is more effective than glasses alone in the treatment of this condition. Two of the trials analysed the role of adding near activities to supplement patching therapy. These trials suggest there may be benefit to adding near activities to prescribed occlusion regime. No trial examining the role of optical penalisation (altering glasses strength) or using partial occlusion (frosted lens opposed to a patch) was found. The effectiveness of optical penalisation and partial occlusion for the treatment of strabismic amblyopia is unknown.

Quality of the evidence: The quality of the available evidence is high.

Authors' conclusions: 

Occlusion, whilst wearing necessary refractive correction, appears to be more effective than refractive correction alone in the treatment of strabismic amblyopia. The benefit of combining near activities with occlusion is unproven. No RCTs were found that assessed the role of either partial occlusion or optical penalisation to refractive correction for strabismic amblyopia.

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Background: 

Amblyopia is reduced visual acuity in one or both eyes in the absence of any demonstrable abnormality of the visual pathway. It is not immediately resolved by the correction of refractive error. Strabismus develops in approximately 5% to 8% of the general population. The aim of treatment for amblyopia is to obtain the best possible level of vision in the amblyopic eye. Different treatment options were examined within the review.

Objectives: 

By reviewing the available evidence we wanted to establish the most effective treatment for strabismic amblyopia. In particular this review aimed to examine the impact of conventional occlusion therapy for strabismic amblyopia and to analyse the role of partial occlusion and optical penalisation for strabismic amblyopia.

Search strategy: 

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2013, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to January 2014), EMBASE (January 1980 to January 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to January 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 30 January 2014.

Selection criteria: 

We included randomised controlled trials (RCTs) for the treatment of strabismic amblyopia including participants of any age.

Data collection and analysis: 

Two authors working independently extracted and entered data into Review Manager 5 and then independently checked the data for errors.

Main results: 

We included three RCTs in this review. The studies reported mean logMAR visual acuity achieved. Mean difference in visual acuity was calculated. When comparing conventional part-time occlusion (with any necessary glasses), PEDIG 2006 reported that this treatment was more beneficial than glasses alone for strabismic amblyopia; the mean difference between groups was -0.18 LogMAR (statistically significant 95% confidence interval (CI) -0.32 to -0.04). Supplementing occlusion therapy with near activities may produce a better visual outcome compared to non-near activities after four weeks of treatment (PEDIG 2005). The results of the pilot study showed mean difference between groups was -0.17 LogMAR (95% CI -0.53 to 0.19). Results from a larger RCT (PEDIG 2008) are now available, showing that supplementing occlusion therapy with near activities may produce a better visual outcome after eight weeks of treatment; the mean difference between groups was -0.02 LogMAR (95% CI -0.10 to 0.06). One further article ia awaiting assessment as in its current format there is insufficient information to include (Alotaibi 2012).

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