. 2020 Aug 27;15(8):e0238122. doi: 10.1371/journal.pone.0238122

Table 1. Characteristics of the schoolchildren [mean ± SD or n (%)].

Group	All	2014	2016	2018	P-value (3 years)
N	4365	1517	1394	1454
Sex					0.01
Male	2054 (47.1%)	696 (45.9%)	629 (45.1%)	729 (50.1%)
Female	2311 (52.9%)	821 (54.1%)	765 (54.9%)	725 (49.9%)
Age	11.12 ± 1.66	11.08 ± 1.81	11.04 ± 1.66	11.23 ± 1.49	0.008
Age groups (N, % of total)					< 0.001
6 and 7	158 (3.6%)	74 (4.9%)	57 (4.1%)	27 (1.9%)
8	301 (6.9%)	126 (8.3%)	92 (6.6%)	83 (5.7%)
9	552 (12.7%)	189 (12.5%)	202 (14.5%)	161 (11.1%)
10	874 (20.0%)	285 (18.8%)	279 (20.0%)	310 (21.3%)
11	1248(28.6%)	408 (26.9%)	390 (28.0%)	450 (30.9%)
12	625 (14.4%)	210 (13.8%)	185 (13.3%)	230 (15.8%)
13	408 (9.4%)	128 (8.4%)	134 (9.6%)	146 (10.0%)
14 and 15	199 (4.6%)	97 (6.4%)	55 (3.9%)	47 (3.2%)
Prevalence Refractive errors
Myopia	176 (4.0%)	53 (3.5%)	61 (4.4%)	62 (4.3%)	0.41
Hyperopia	1935 (44.3%)	959 (63.2%)	528 (37.8%)	448 (30.9%)	< 0.001
Emmetropia	2254 (51.6%)	505 (33.3%)	805 (57.8%)	944 (64.9%)	< 0.001
Overall SER (D)	0.69 ± 0.91	0.89 ± 0.86	0.62 ± 0.89	0.56 ± 0.95	< 0.001
Male	0.66 ± 0.88	0.84 ± 0.85	0.58 ± 0.81	0.56 ± 0.96	< 0.001
Female	0.72 ± 0.94	0.93 ± 0.88	0.65 ± 0.96	0.56 ± 0.99	< 0.001
Overall astigmatism (D)	-0.16 ± 0.39	-0.16 ± 0.40	-0.17 ± 0.38	-0.15 ± 0.39	0.32
Male	-0.16 ± 0.40	-0.16 ± 0.40	-0.15 ± 0.39	-0.15 ± 0.41	0.51
Female	-0.16 ± 0.38	-0.16 ± 0.37	-0.17 ± 0.38	-0.15 ± 0.39	0.43
Astigmatism^† direction
WRT (30–0–150⁰)	474 (53.1%)	131 (37.9%)	146 (60.6%)	197 (64.4%)	< 0.001
ATR (60–120 ⁰)	372 (41.7%)	193 (55.8%)	84 (34.9%)	95 (31.0%)	< 0.001
Oblique (31–59 ⁰ and 121–149 ⁰)	47 (5.3%)	22 (6.4%)	11(4.6%)	14 (4.6%)	0.51

SER = spherical equivalent refraction.

† astigmatism > 0.25D.