PURPOSE: To investigate the long-term vision outcomes of amblyopia treatment in "successfully" compared with "unsuccessfully" treated patients. METHODS: Forty-two participants (n=42, mean age 14.8 years, range 10-25 years) were enrolled in the study. Individuals with strabismic or mixed (strabismic and anisometropic) amblyopia were examined at a mean of 6.6 years (range 1-18 years) after cessation of amblyopia treatment. Participants were classified as being "successfully" treated (Group 1) if visual acuity of 6/7.5 or better was achieved at cessation of treatment, or "unsuccessfully" treated (Group 2) if visual acuity of 6/9 or less was achieved at cessation of treatment. Visual acuity was analyzed by calculating an interocular score or difference in visual acuity between the amblyopic and non amblyopic normal (control) eye. RESULTS: A deterioration of visual acuity occurred in 62% of the participants in both Groups 1 and 2. The mean deterioration of visual acuity over time for either group was less than one LogMAR chart line and was not "statistically significant" by convention (F [1,39]=3.361, p=0.074). The outcomes achieved at cessation of treatment did not "statistically significantly" affect the mean deterioration that occurred over time (F [1,49]=0.031, p=0.860). CONCLUSION: Visual acuity was relatively stable over a mean followup period of 6.6 years. The treatment outcome and the success of amblyopia treatment were found to be irrelevant to long term stability of visual acuity. These findings suggest that amblyopia treatment mostly results in a lasting improvement in visual acuity, and that both unsuccessfully and successfully treated individuals maintain their visual acuity improvement achieved during treatment.