Table 2. The prevalence of different types of refractive errors by gender, school types and grades.

Demographic variable	Myopia, n (%)	p	Hyperopia, n (%)	p	Astigmatism, n (%)	p
Gender
Male	319 (27.5)	0.399	40 (3.4)	0.815	33 (2.8)	0.881
Female	329 (29.1)		37 (3.3)		31 (2.7)
Grade
1st	135 (17.6)	<0.001	36 (4.7)	0.044	17 (2.2)752	0.425
5th	207 (27.0)		20 (2.6)		22 (2.9)
9th	306 (40.5)		21 (2.8)		25 (3.3)
School type
Gymnasiums	309 (29.1)	0.409	31 (2.9)	0.279	29 (2.7)	0.871
General education schools	339 (27.5)		46 (3.7)		35 (2.8)
Total	648 (28.3)		77 (3.4)		64 (2.8)