It is logical and common sense that the earlier the amblyopia is treated, the better the outcome. There has been a great deal of research exploring the effect of the type of treatment used, such as the effect of the length of masking and the frequency of atropine use on treatment outcomes. Several studies have shown that either masking or atropine dilatation for amblyopia can improve visual acuity. Repka’s long-term follow-up study showed that improvement in visual acuity with amblyopia treatment was maintained at least through age 15, and that masking with pupils was equally effective. The study reported on the visual acuity of patients with moderate amblyopia who participated in treatment when they were younger than 7 years old and were followed up to 15 years of age. A total of 419 children with amblyopia (visual acuity between 20/100 and 20/40) were randomized in the multicenter clinical trial to a blindfolded group (at least 6 h/day) and a 1% atropine sulfate eye drop group (once daily) for 6 months. Follow-up treatment was determined by the investigator after 6 months of treatment. Two years after enrollment, 188 of the children were enrolled in long-term follow-up. The children’s visual acuity was measured at the age of 15 years using the ETDRS scale. The mean visual acuity in the amblyopic eye was 0.14 logMAR (about 20/25) in 147 children at age 15 years; 59.9% of the amblyopic eyes had visual acuity of 20/25 or better and 33.3% had visual acuity of 20/20 or better. Nine children (6.1%) had other treatment (other than glasses) from 10 to 15 years of age. At 10 and 15 years of age, the mean interocular visual acuity differences were similar (2.0 and 2.1 rows, respectively; P = 0.39). At 15 years of age, children entering the treatment group under 5 years of age had better visual acuity relative to those entering at 5-6 years of age (mean logMAR, 0.09 vs. 0.18; P < 0.001). At age 15 years, there was no significant difference in the effect of initial treatment modality (atropine treatment or masking therapy) on visual acuity in the amblyopic and contralateral eyes (P = 0.44 and P = 0.43). CONCLUSION: Most children with moderate amblyopia who begin treatment before age 7 years achieve good vision by age 15 years, although mild residual amblyopia is common. The visual prognosis was similar regardless of whether the initial treatment was with atropine or masking. The results of this study suggest that visual acuity improvement with amblyopia treatment is maintained until at least 15 years of age