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)
*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.
(1) Reading for pleasure
    term and holidays§2.320.3620.5735.50.0100.73
    last week (term time)220.4360.62220.0860.90
(2) Studying
    term and holidays§18.5180.3810.4712120.6650.62
    last week (term time)18150.4380.361210.50.4560.65
(3) Reading for pleasure and studying21.820.80.3440.3415.817.50.5400.35
(4) Television
    last week (term)30.6280.4856.50.3510.68
(5) Computer
    last week (term)<1<10.3400.35110.2321.00
(6) Sewing
    last week (term)<1<10.178−0.01<1<10.4221.00