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Computer use has been linked to computer vision syndrome (CVS), which is the complex of eye and vision-related problems, such as eyestrain, blurred vision, dry and irritated eyes, tired eyes, and headaches, that have been associated with computer use (Anshel, 1998). Studies of adult computer use have shown that CVS is significantly associated with the daily hours of computer use (Hedge, 1991). CVS has also been shown to be more prevalent in workplaces illuminated with direct, down lighting systems, such as those found in schools, compared with indirect, up lighting systems (Hedge, Sims and Becker 1995). Unfortunately, to date there has been relatively little research on these topics with children, but the few studies that have been conducted suggest that we should expect a similar association between computer use and CVS.
Marumoto et al. (1996) investigated whether sitting posture is associated with the failing eyesight of young students while studying at a computer. They found that the viewing distance of myopic children was significantly shorter than that of the normal-sighted children, and the average viewing distance of the 10 my opes studied was 15.0 cm, which is extremely short given the generally recommended viewing distance of 50 to 70 cm for computer screen operation that is derived from the resting position of the eye. They found that viewing distance was significantly correlated with the neck flex ion angle, viewing angle, near-point, and accommodative power. They also showed that the shorter viewing distance while studying created postural problems, such as extreme neck flex ion, which also decreased the accommodative power of the eyes and exacerbated failing eyesight of young students. In a subsequent study, Marumoto et al., (1999) conducted a more detailed investigation of how the posture of 19 13-year-old students was related to degradation of vision. When the students were studying printed materials a significant relationship between viewing distance and eye accommodation, near point (cm), viewing angle, and neck angle was demonstrated, and they concluded that poor posture, particularly decreased neck angle, is significantly related to the degradation of vision in children.
A field study of office workers investigated the preferred position of computer visual displays relative to the eyes, how this affected reports of visual strain, and whether there were any systematic individual differences in screen arrangement (Jaschinski, Heuer, and Kylian, 1998). Results showed that those working at high screens (screen center at eye level) reported greater eyestrain than those with lower screens (screen center 18 cm below eye level). When free to adjust screen distance, the most comfortable and preferred screen position was placement this at a viewing distance between 60 and 100 cm and at a 16-degree downwards vertical inclination of gaze. More visual strain was reported when forced to work at a shorter viewing distance.