Event Details - ACCOMMODATION AND CONVERGENCE DURING SUSTAINED COMPUTER WORK

PURPOSE: With computer usage becoming almost universal in the contemporary workplace, the reported prevalence of computer vision syndrome (CVS) is increasing. However, the precise physiological mechanism underlying CVS remains unclear. While abnormal accommodation and vergence responses have been cited as being responsible for this condition, there is little objective evidence to support this claim. Accordingly, this study measured both of these oculomotor parameters during a sustained period of computer use. METHODS: Subjects (N=20) were required to read text from a laptop computer at a viewing distance of 50cm for a sustained 30 min period through their habitual refractive correction. At 2min intervals, the accommodative response to the computer screen was measured objectively using a Grand Seiko WAM 5500 optometer. Additionally, immediately following the accommodation measurement, the vergence response was assessed by measuring the associated phoria (AP), i.e., prism to eliminate the horizontal fixation disparity using a customized fixation disparity target which appeared directly on the computer screen. Subjects were asked to rate the degree of discomfort during the reading task on a scale from 1-10. RESULTS: Mean accommodation and AP values were 1.07D and 0.74PD exo, respectively. The mean discomfort score was 4.9. No significant change in accommodation or vergence was observed during the 30min test period. There was no significant difference in the accommodative response as a function of subjective difficulty. However, the mean AP for those subjects who reported the least and greatest discomfort during the task was 1.55PD exo and ortho, respectively (p=0.02). CONCLUSIONS: CVS was worse in subjects exhibiting zero fixation disparity, but does not appear to be related to differences in accommodation. A slightly reduced vergence response increases subject comfort during the task.