Korean J Ophthalmol Vol.24, No.4, 2010 the frequency of amblyopia development was higher in chil- dren with an initial visual acuity ＜20/40 than it was in chil- dren with an initial visual acuity of ≥20/40. This result sug- gests that, under conditions of high dependence on the sound eye, abnormal binocular interaction and/or visual deprivation resulted. Older children with amblyopia generally respond less fa- vorably to treatment [1]. Hussein et al. [9] demonstrated that age greater than six years at the onset of treatment was a risk factor for failure to achieve functional success. According to Leon et al. [12], children age three and older had an increased risk of amblyopia compared with that of younger children for moderate (≥4, ＜6 line difference) levels of anisometropia. However, Woodruff et al. [4] could not find a correlation be- tween unfavorable amblyopia treatment outcome and age at initiation of treatment. Rho et al. [17] also could not docu- ment a statistical significance between age at initial treatment and treatment outcome. In the current study, there was no statistical significance of amblyopia prevalence in patients ＜5 year of age at the time of initial spectacle correction. We also found that there was no significant difference of am- blyopia risk between the ＜5 year of age group and ≥5 year of age group among patients with an initial BCVA ＜20/40. Such a discrepancy between studies indicates the need for more research to determine whether age at initial treatment affects treatment outcome. Previous studies have demonstrated that poor patching compliance was associated with a poor outcome. Hussein et al. [9] demonstrated inadequate compliance with treatment according to parental report at the first follow-up examination was a key predictive factor for failure risk. Choi and Kim [18] have demonstrated a relationship between anisome- tropic amblyopia and occlusion therapy when the treatment age was younger and the compliance rate was higher in the success group compared with those of the failure group. In the current study, patching therapy and the amblyopia prev- alence had no significant relationship; however, poor com- pliance with patching was a risk factor for the prevalence of amblyopia. A difference in the BCVA between the eyes is related to treatment outcome in amblyopia. Lee et al. [19], in a study of 80 patients with strabismic amblyopia and anisometropic amblyopia, demonstrated that patients with ≤4 lines of differ- ence in the BCVA between the sound and amblyopic eyes at the initial visit had a high success rate with patching therapy. Although strabismic amblyopia was excluded from our study, we also found that BCVA differences between sound and amblyopic eyes of ≥4 lines was a risk factor for the devel- opment of amblyopia in patients having undergone patching therapy. Regarding the limitations of the current study, there was a relatively small number of patients and lacks of stand- ardization in the age groups and treatment method. A large prospective study is thus required to establish more statisti- cally powerful results. 228 In conclusion, eyes with an initial visual acuity of ＜20/40, a high magnitude of anisometropia, and a ≥4 line difference in BCVA between the sound and amblyopic eyes were less likely to achieve successful outcomes. Therefore, such children must receive careful treatment. In addition, parents and guardians must be fully aware of the risk through sufficient explanation, regular observation, and amblyopia treatment. 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