The Blink Frequency Relationship between Reading from a Computer Screen and Reading from a Printed Page

Abstract

One of the components of what has become known as Computer Vision Syndrome (CVS) is a complaint of dry eyes which is not present in other near work situations. The etiology of the dryness is believed to be decreased blink rate and/or a wide palpebral aperture while viewing a computer monitor. This study examined the first theory only, although if the first theory is disproven the second one gains more credence. Methods: There were 31 subjects enrolled in this study. All initially filled out a questionnaire of symptomatology and underwent a series of refractive and ocular examinations in order to exclude those subjects with clinical dry eye or other related ocular conditions. In the second phase each subject read a selection for 10 minutes once from a computer screen and once from a printed page. This experimental phase was conducted in a standard classroom with standard lighting, without internal air conditioning or heating. The order of reading and selected tests was performed randomly during morning hours on consecutive days. The text and angle of gaze was uniform for both sessions, with each condition (computer screen or paper) having its own specific working distance and angle of gaze. The performance was filmed with an internet camera and later the amount of blinking was scored manually. Results: The number of blinks per minute while reading from a computer screen was greater, on average (1.73 ± 0.43) than reading from a printed page. However, this difference was only significant at the p=0.22 level. 18 subjects had a higher blink rate with computer work while 13 had a higher blink rate with a printed page. The subjects with the higher blink rate reading from a computer screen had a higher differential between the two scores. Conclusions: No significant difference in blink rate was found between the blink rate when reading from computer screen as opposed to a printed page. Even the mildly significant result indicated the opposite. This would indicate that the theory that dry eye associated with computer work is not caused by excessive "staring" and lower blink rate. This gives indirect support to the theory that the height of the computer screen is a more important variable.