Table 3. Logistic regression analysis of the relationship between tear lipid layer status in VDT users and working duration.

Category	Sub category	Tear lipid layer status (DR-1 grade >3)		OR† *	95% C I§
		Cases	Controls
		(n = 109)	(n = 492)
VDT working year	<4	36	142	reference
	4–8	22	108	0.90	0.49, 1.64
	8–12	29	137	0.99	0.55, 1.76
	≥12	22	105	1.05	0.53, 2.09
P trend = 0.896
Daily VDT hour	≤2	20	82	reference
	2–4	25	133	0.75	0.39, 1.45
	4–6	20	119	0.66	0.33, 1.32
	6–8	24	117	0.80	0.41, 1.59
	>8	20	41	2.03	0.96, 4.34
P trend = 0.190

†OR: odds ratio;

*Adjusted for gender and age;

§Confidence interval.