Time spent indoors with studying was significantly associated (univariate analysis) with maternal and paternal myopia, white collar occupation of mother and father, taller body height, urban region of habitation, higher school grade, less time spent outdoors, longer axial length, deeper anterior chamber, higher AL/CC ratio, more myopic refractive error, longer vertical optic disc and cup diameter, and larger area of beta zone (
Table 5). In the multivariate analysis, we first dropped vertical optic cup diameter (variance inflation factor: 10.9), father's occupation (variance inflation factor: 3.5), smoking by the mother (
P = 0.65), time spent outdoors (
P = 0.70), mother's occupation (
P = 0.47), paternal myopia (
P = 0.71), maternal myopia (
P = 0.83), anterior chamber depth (
P = 0.59), horizontal optic cup diameter (
P = 0.37), axial length (
P = 0.66), refractive error (
P = 0.23), body height (
P = 0.14), and vertical disc diameter (
P = 0.68). In the final model, time spent indoors with studying was significantly (regression coefficient:
r = 0.52) associated with larger area of beta zone (
P = 0.01), higher AL/CC ratio (
P = 0.006), and urban region of habitation (
P < 0.001;
Table 6)