Twenty-three (50.0%) of 46 patients who were treated with patching therapy had amblyopia, and ten (58.8%) of 17 pa- tients without patching treatment had amblyopia. Good com- pliance with patching occurred in 25 patients, ten (40.0%) of whom had amblyopia. Of the 21 patients with poor com- pliance, 13 (61.9%) had amblyopia. Poor compliance with patching was a risk factor for amblyopia (p=0.027), while no differences existed in patients who were or were not treated with patching therapy (p=0.534) (Table 3). Among the patients with good compliance to patching therapy, 11 had ＜4 lines of difference in the BCVA between the sound and amblyopic eyes at the initial presentation, and two (18.2%) patients had amblyopia at the final visit. Eight (57.1%) of 14 patients who had ≥4 lines of difference in the BCVA between the eyes at the initial visit presented with am- blyopia at the final visit. A difference in the BCVA between the sound and amblyopic eyes ≥4 lines was a risk factor for the development of amblyopia in patients with good com- pliance to patching therapy (p=0.045) (Table 4). Discussion Amblyopia is one of the leading causes of acquired mo- nocular visual impairment [10], with an estimated prevalence in the pediatric population ranging from 4.7% to 7.5% [11]. Children with anisometropic amblyopia typically are diagnosed later than are children having other types of amblyopia, like- ly reflecting the lack of noticeable physical abnormalities in these children, in contrast to children with strabismus, who usually have an obvious condition that is easily recognized [3-5]. With respect to the magnitudes of anisometropia, Leon et al. [12] demonstrated that children with higher magnitudes of anisometropia had a higher prevalence and greater depths of amblyopia. However, Hussein et al. [9] concluded that the type, amount of refractive error, and the difference in re- fractive power between the eyes were significant risk factors for treatment failure. In the current study, children with high- er magnitudes of anisometropia had a higher prevalence of amblyopia. CE Lee, et al. Factors Influencing Anisometropic Amblyopia It is known that amblyopia is more severe and more fre- quent in hypermetropic anisometropia than it is myopic ani- sometropia [13]. In a study by Weakley [8], there was a ten- dency for the development of amblyopia at lower levels of hyperopic anisometropia (spherical hypermetropic anisome- tropia ＞1-2 D) compared to that with myopic anisometropia (spherical myopic anisometropia ＞-2 to -3 D). However, in patients with equal levels of spherical myopic anisometropia and spherical hypermetropic anisometropia ＞2 D, both the incidence and severity of amblyopia were remarkably similar. Kim et al. [14] reported that there is no significant difference in the frequencies of amblyopia between spherical and cylindrical anisometropia patients; however, in spherical anisometropia, hyperopic anisometropia patients have a higher risk for developing amblyopia. However, in this study, there were no differences in the frequency of amblyopia de- velopment among patients having myopic spherical aniso- metropia, hypermetropic spherical anisometropia, or astigmatic anisometropia. The lack of statistical significance for this comparison was probably due to the relatively higher mag- nitude of anisometropia in the myopia anisometropia group than in the other groups, and the small numbers in each group of this study. Several studies have suggested that that the factors influ- encing outcomes of amblyopia are the initial age of treatment and the BCVA of the weaker eye at the time of the initial treatment. According to Kim et al. [15], in a study involving 66 amblyopic children, the duration of treatment was longer in children with an initially poorer BCVA and in younger children compared to that in older children with better BCVAs at the time of diagnosis. Chen et al. [16] reported that, of 60 anisometropic amblyopic children with spectacle correction alone, the resolution of amblyopia was related to better initial visual acuity and lesser degrees of anisometropia. Hussein et al. [9] found that an initial visual acuity in the am- blyopic eye of 20/200 or worse was a risk factor of treatment failure, and patients with very poor vision in the amblyopic eye can have significant improvement in vision, but may not achieve a final vision of 20/40 or better. In the current study, Table 3. Comparison between patching therapy and non-patching therapy groups Good compliance† 10 (40.0) 15 (60.0) Amblyopia (%) Non-amblyopia (%) *p=0.534 (Pearson’s chi-square test); †p=0.027 (Pearson’s chi-square test). Patching (+)* Poor compliance† 13 (61.9) 8 (38.1) Table 4. Prevalence of amblyopia as a function of the BCVA differences between sound and amblyopic eyes ＜4 lines ≥4 lines BCVA of amblyopic eye Initial Final* 0.68±0.13 0.86±0.15 0.30±0.12 0.75±0.21 BCVA=best corrected visual acuity. *After patching of the sound eye for 4 to 6 hours per day; †p=0.045 (Pearson’s chi-square test). Total 23 (50.0) 23 (50.0) Non-amblyopia† 9 (81.8%) 6 (42.9%) Patching (－)* 10 (58.8) 11 (41.2) Amblyopia† 2 (18.2%) 8 (57.1%) 227