Purpose: To evaluate the effectiveness of early in comparison to late(r) treatment in children with (1) amblyopia or (2) its risk factors, such as refractive errors and strabismus.
Methods: Eight bibliographic databases were searched with no limitation to a specific year of publication or language. Studies including children and juveniles with amblyopia or its risk factors were considered for this review.
Results: In total, five studies (three direct comparisons within one study; one indirect comparison between two studies) met the inclusion criteria. (1) Treatment of amblyopia: one comparison suggested that amblyopia treatment in preschool children is more effective than treatment later in life. However, a subgroup analysis of children who have never received any treatment indicated that patching may also have an effect after the "sensitive phase." The second comparison showed that a delay in treatment until the age of 5 did not seem to influence effectiveness. (2) Treatment of amblyogenic risk factors: two comparisons showed that hyperopia treatment and strabismus surgery (outcome: remaining amblyopia) is more effective under 2 years of age than later in life. However, the studies showed methodological weaknesses (for example, a high loss to follow-up, unmasked outcome assessments) limiting the validity of their findings. The current literature does not provide data evaluating quality of life or school performance.
Conclusions: Uncertainties remain about the age at which treatment for amblyopia or its risk factors is most effective. Beside methodological limitations, the design of the studies made it challenging to address this question sufficiently.