Table 2.

Baseline smartphone usage (h/d) and baseline digital eye strain (n = 1,508)

Smartphone usage (min/d)	Double vision	Blurred vision (reading)	Blurred vision (change from reading to distance viewing)	Difficulty in refocusing	Eye strain	Dry eyes	Eye fatigue	Irritated or burning eyes	Photophobia	Headache	Total score (SD)
0–60 (n = 277)	18.1%	23.8%	27.8%	21.7%	14.4%	6.5%	42.6%	26.4%	9.8%	23.8%	2.15 (2.50)
61–120 (n = 171)	16.4%	22.8%	30.4%	21.6%	15.8%	11.1%	48.5%	25.7%	9.9%	26.3%	2.29 (2.58)
121–180 (n = 134)	21.6%	29.9%	31.3%	23.9%	17.2%	7.5%	46.3%	24.6%	10.5%	32.8%	2.46 (2.60)
181–240 (n = 160)	21.9%	30.0%	37.5%	21.3%	20.0%	11.3%	50.0%	28.1%	16.3%	32.5%	2.69 (2.63)
241 + (n = 766)	24.5%	38.6%	46.3%	35.3%	23.4%	15.4%	60.2%	41.9%	21.4%	38.1%	3.45 (3.09)
p-value	0.07	< 0.001	< 0.001	< 0.001	0.01	0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
p-value for trend	0.006	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001