Korean J Ophthalmol Vol.24, No.4, 2010 Visual acuity was measured at a 4 m distance using an inter- national standard vision chart (Jin’s vision chart), and am- blyopia was defined as a BCVA difference between the sound and amblyopic eyes of more than two lines on the vi- sion chart. Any patient with structural ocular abnormalities, including strabismus, history of spectacle correction, occlu- sion or penalization therapy, previous ocular surgery, ocular trauma, or neurologic disorders which could influence visual acuity, or with BCVA of the sound eye ＜20/40 was excluded from the research. Each patient’s age at diagnosis, un- corrected visual acuity and BCVA, and examination of the external eye and fundus were studied. Cycloplegic refraction was performed after application of 1% cyclopentolate eye drops. Eyeglasses were prescribed based on the results of cy- cloplegic refraction. The prevalence of amblyopia at the final visit was ana- lyzed by studying the type of anisometropia (myopia, hyper- metropia, and astigmatism), magnitude of anisometropia, BCVA at the start of treatment (≥20/40 or ＜20/40), BCVA differences between the sound and amblyopic eyes (≥4 lines or ＜4 lines), and the age at which eyeglasses were first worn (＜5 years of age or ≥5 years of age). Anisometropia was divided into the following two groups: spherical anisometropia, in which the difference in the spherical equivalent between the eye was ＞2 D, while the cylinder power difference was ＜2 D, and cylindrical anisometropia, which had a ＞2 D cy- lindrical power difference. The magnitude of anisometropia was graded into an arbitrary three-category classification (Group 1, 2 to ＜3 D; Group 2, 3 to ＜4 D; Group 3, ≥4 D). Full spherical and astigmatic refractive errors were cor- rected in each patient, and, depending on the visual improve- ment at the second visit (≥2 lines difference between sound and amblyopic eyes persisted), the patient was required to patch the sound eye for 4 to 6 hours per day. The compliance with patching treatment was divided into the following two groups based on the parents’ estimate: children with good compliance who followed the treatment guideline an esti- mated ≥75% of the time, and poor compliance (＜75% of the time). A chi-square test and t-test were conducted for statistical analysis using SPSS ver. 15.0 (SPSS Inc., Chicago, IL, USA), and a p＜0.05 was considered to be statistically significant. Results The mean age at the start of treatment was 5.9±3.9 years. Thirty-three patients (52.3%) were male and 30 patients (47.7%) were female. The follow-up period averaged 57.2 ±38.0 months, with a maximum of 147 months. Forty-one patients were diagnosed with spherical anisometropia, 18 were diagnosed with myopic spherical anisometropia, and 13 (72.2%) patients had amblyopia. Twelve of 23 (52.1%) pa- tients with hypermetropic spherical anisometropia also had amblyopia, and eight of 22 (36.4%) astigmatic anisometropia patients had amblyopia. There were no frequency differences 226 according to the type of anisometropia (myopic spherical anisometropia, hyperopic spherical anisometropia, and astig- matic anisometropia; p=0.770) (Table 1). Nine (39.1%) of 23 patients in Group 1 (≥2 D, ＜3 D), 12 (52.1%) of 23 patients in Group 2 (≥3 D, ＜4 D), and 12 (70.6%) of 17 patients in Group 3 (≥4 D) had amblyopia. In general, children with higher magnitudes of anisometropia had a higher prevalence of amblyopia (p=0.021) (Table 2). Twenty-seven patients had an initial BCVA of ＜20/40, 17 (63.0%) of which had amblyopia. Sixteen of 36 (44.4%) pa- tients with BCVA ≥20/40 had amblyopia. There were differ- ences among the statistical frequencies of amblyopia be- tween the two groups (p=0.008), and an initial BCVA ＜20/40 in the amblyopic eye was a risk factor for the devel- opment of amblyopia. Among 18 patients ＜5 years of age at the initial visit, 12 had an initial BCVA of ＜20/40, and seven (58.3%) of these 12 patients had amblyopia. Of the six pa- tients whose initial BCVA ≥20/40, one (16.7%) had amblyopia. Forty-five patients were ≥5 years of age at initial presentation. Fifteen patients had an initial BCVA of ＜20/40 and ten (66.7%) of these patients had amblyopia. Fifteen of 30 (50.0%) patients whose initial BCVA ≥20/40 had amblyopia. Given an initial BCVA ＜20/40, the risk of am- blyopia at the final visit was not significantly different be- tween the initial presentation groups with respect to age (p=0.656). Eighteen patients were ＜5 years of age at the time of the initial spectacle correction and nine (50.0%) had amblyopia, while 24 (53.3%) of 45 patients ≥5 years of age had amblyopia. There was no statistical significance regarding the preva- lence of amblyopia between patients ＜5 and ≥5 years of age at the time of initial spectacle correction (p=0.811). Forty-six patients underwent patching therapy, and the mean duration of patching therapy was 22.2±17.9 months. Table 1. Prevalence of amblyopia as a function of the type of anisometropia at the initial visit Myopia 18 13 (72.2) 5.13±3.55 Hypermetropia Astigmatism 23 22 12 (52.0) 8 (36.4) 2.95±0.99 3.18±1.33 No. of patients Amblyopia (%) Average anisometropia (D) p=0.770 (Pearson’s chi-square test). D=diopters. Table 2. Prevalence of amblyopia as a function of the magnitude of anisometropia Group I* Group II† Group III‡ Total Amblyopia (%) 9 (39.1) 12 (52.2) 12 (70.6) 33 (52.4) Non-amblyopia (%) 14 (60.9) 11 (47.8) 5 (29.4) 30 (47.6) Total 23 23 17 63 p=0.021 (Pearson’s chi-square test). *≥2 diopters (D), ＜3 D; †≥3 D, ＜4 D; ‡≥4 D (anisometropia magnitude).