Amblyopia (lazy eye) is a term describing reduced vision in one or both eyes. Amblyopia can sometimes be caused by a need for glasses. The need for glasses may be greater in one eye causing amblyopia only in the worse eye. This happens because the brain receives a weaker image from the eye with the greater need for glasses and prefers to use the eye with a clearer image. Sometimes there may be a strong need for glasses in both eyes causing amblyopia in both eyes. This is because the brain receives a blurred image from both eyes.
Children who have amblyopia due to a need for glasses in one eye only are often asked to wear a patch over the good eye, in addition to wearing their spectacles, to improve their vision. This review found that for some children with this type of amblyopia a period of glasses wear alone can restore normal vision. For those children for whom glasses wear alone does not improve vision there is evidence that wearing a patch can further improve vision. At present it is not possible to tell at the start of treatment which children will respond to glasses alone and which ones will need a patch as well. The amount of patching needed for an individual child cannot yet be predicted. This is because the effects of factors such as age are not fully understood. These findings are based on the results of eleven high-quality trials.
Children who have amblyopia in both eyes because of a need for glasses in both eyes are currently advised to wear their glasses as much of the time as possible in order to improve their vision. No trials looking at treatment for children who had reduced vision in both eyes were found.
In some cases of unilateral refractive amblyopia it appears that there is a treatment benefit from refractive correction alone. Where amblyopia persists there is evidence that adding occlusion further improves vision. Despite advances in the understanding of the treatment of amblyopia it is currently still not possible to tailor individual treatment plans for amblyopia. The nature of any dose/response effect from occlusion still needs to be clarified. Partial occlusion appears to have the same treatment effect as glasses alone when started simultaneously for the treatment of unilateral refractive amblyopia. Treatment regimes for bilateral and unilateral refractive amblyopia need to be investigated further.
Refractive amblyopia is a common cause of reduced visual acuity in childhood, but optimal treatment is not well defined. This review examined the treatment effect from spectacles and conventional occlusion.
Evaluation of the evidence of the effectiveness of spectacles, occlusion or both in the treatment of unilateral and bilateral refractive amblyopia.
We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 1), MEDLINE (January 1950 to January 2012), EMBASE (January 1980 to January 2012), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to January 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 24 January 2012. We manually searched relevant conference proceedings.
Randomised controlled trials of treatment for unilateral and bilateral refractive amblyopia by spectacles, with or without occlusion, were eligible. We included studies with participants of any age.
Two authors independently assessed abstracts identified by the searches. We obtained full-text copies and contacted study authors where necessary. Eleven trials were eligible for inclusion. We extracted data from eight. Insufficient data were present for the remaining three trials so data extraction was not possible. We identified no trials as containing participants with bilateral amblyopia. We performed no meta-analysis as there were insufficient trials for each outcome.
For all studies mean acuity (standard deviation (SD)) in the amblyopic eye post-treatment was reported. All included trials reported treatment for unilateral refractive amblyopia.
One study randomised participants to spectacles only compared to no treatment, spectacles plus occlusion compared to no treatment and spectacles plus occlusion versus spectacles only. For spectacles only versus no treatment, mean (SD) visual acuity was: spectacles group 0.31 (0.17); no treatment group 0.42 (0.19) and mean difference (MD) between groups was -0.11 (borderline statistical significance: 95% confidence interval (CI) -0.22 to 0.00). For spectacles plus occlusion versus no treatment, mean (SD) visual acuity was: full treatment 0.22 (0.13); no treatment 0.42 (0.19). Mean difference (MD) between the groups -0.20 (statistically significant: 95% CI -0.30 to -0.10). For spectacles plus occlusion versus spectacles only, MD was -0.09 (borderline statistical significance 95% CI -0.18 to 0.00). For two other trials that also looked at this comparison MD was -0.15 (not statistically significant 95% CI -0.32 to 0.02) for one trial and MD 0.01 (not statistically significant 95% CI -0.08 to 0.10) for the second trial.
Three trials reviewed occlusion regimes.One trial looked at two hours versus six hours for moderate amblyopia: MD 0.01 (not statistically significant: 95% CI -0.06 to 0.08); a second trial 2003b reviewed six hours versus full-time for severe amblyopia: MD 0.03 (not statistically significant: 95% CI -0.08 to 0.14) and a third trial looked at six hours versus full-time occlusion: MD -0.12 (not statistically significant: 95% CI -0.27 to 0.03). One trial looked at occlusion supplemented with near or distance activities: MD-0.03 (not statistically significant 95% CI -0.09 to 0.03). One trial looked at partial occlusion and glasses versus glasses only: MD -0.01 (not statistically significant: 95% CI -0.05 to 0.03).