Relationship between Myopia Progression and School Entrance Age: A 2.5-Year Longitudinal Study

Table 4

Comparison of variables among the grade groups in 7- and 8-year-old students.

Variables	7 years					8 years
	Grade 1		Grade 2		value	Grade 2		Grade 3		value
	n	%	n	%		n	%	n	%
Continuous read-write time
<1 h	252	81.3	152	72.4	0.042	248	75.8	133	62.7	0.004
≥1 h and <2 h	34	11	38	18.1		58	17.7	62	29.2
≥2 h	24	7.7	20	9.5		21	6.4	17	8
Continuous mobile game time
<1 h	277	89.6	182	86.3	0.303	266	81.8	182	85.8	0.419
≥1 h and <2 h	17	5.5	19	9		34	10.5	19	9
≥2 h	15	4.9	10	4.7		25	7.7	11	5.2
Continuous use of computer time
<1 h	261	84.2	172	81.5	0.194	263	80.4	165	77.8	0.299
≥1 h and <2 h	27	8.7	28	13.3		34	10.4	31	14.6
≥2 h	22	7.1	11	5.2		30	9.2	16	7.5
Keep watching TV
<1 h	263	85.1	177	83.9	0.091	250	76.7	157	74.4	0.259
≥1 h and <2 h	31	10	22	10.4		53	16.3	44	20.9
≥2 h	15	4.9	12	5.7		23	7.1	10	4.7

The Chi-squared test was used to assess the difference of variables between grade groups. N = number of cases, % = percentage of cases.