Table 5.

Relation between myopia and reported near work

	Africans (n = 2258)				Non-Africans (n = 253)
Near work (hours per week)	Non-myopic median (n = 2151)	Myopic median (n = 107)	p Value*	Quality control kappa†‡ (n = 217)	Non-myopic median (n = 219)	Myopic median (n = 34)	p Value*	Quality control kappa†‡ (n = 17)
(1) Reading for pleasure
term	2	2	0.312	0.56	3	4.5	0.017	0.73
holidays	3	3	0.978	0.53	3	7	0.014	0.73
term and holidays§	2.3	2	0.362	0.57	3	5.5	0.010	0.73
last week (term time)	2	2	0.436	0.62	2	2	0.086	0.90
(2) Studying
term	20	20	0.624	0.53	14	14	0.984	0.69
holidays	15	14	0.110	0.39	8	7	0.387	0.64
term and holidays§	18.5	18	0.381	0.47	12	12	0.665	0.62
last week (term time)	18	15	0.438	0.36	12	10.5	0.456	0.65
(3) Reading for pleasure and studying	21.8	20.8	0.344	0.34	15.8	17.5	0.540	0.35
(4) Television
term	3	3	0.384	0.50	7	8	0.521	0.56
holidays	5	5	0.674	0.48	14	11.5	0.799	0.72
last week (term)	3	3¶	0.628	0.48	5	6.5	0.351	0.68
(5) Computer
term	<1	<1	0.463	0.45	1	2	0.080	1.00
holidays	<1	<1	0.586	0.62	2	3	0.120	0.81
last week (term)	<1	<1	0.340	0.35	1	1	0.232	1.00
(6) Sewing
term	<1	<1	0.331	−0.01	<1	<1	0.869	1.00
holidays	<1	<1	0.168	0.44	<1	<1	0.778	1.00
last week (term)	<1	<1	0.178	−0.01	<1	<1	0.422	1.00

*Wilcoxon’s rank sum test for two unpaired samples.

†Grouped in intervals of 5 hours, except for the sewing variables which were grouped in intervals of 4 hours (to avoid all values being in the same group).

‡Interpretation of kappa values: ≤0.20 = poor agreement, 0.21−0.40 = fair agreement, 0.41−0.60 = moderate agreement, 0.61−0.80 = good agreement, 0.81−1.00 very good agreement (13).

§Term: holidays weighted 3:1.

¶N=106.