The influence of eye solutions on blinking and ocular comfort at rest and during work at video display terminals

The aim of this work was to study blink frequency changes and levels of ocu lar discomfort during work at a video display terminal, and the effects on these parameters of augmented or reduced humidification of the ocular surfa ce. Blink rate was measured from recordings of the electrical signal evoked by the contraction of the orbicularis oculi muscle. Blink rate and interblink intervals were analyzed at rest and during performance of a task with a com puter (playing a card game) for 10 or 30 min in steady environmental condit ions and during application of a continuous stream of air to the face. In t wo separate sessions, the effect of pretreatment with humidifying ocular so lutions of different elastoviscosity (balanced salt solution or elastovisco us 0.1% Hylan A solution) was assayed. At the end of each experimental peri od, the subjects marked the level of ocular discomfort experienced on a 0-1 0 cm visual analogue scale. The blink frequency at rest (12.4 +/- 1.2 blinks min(-1)) was reduced signi ficantly (to 10.3 +/- 1.1 blinks min(-1)) by pretreatment with elastoviscou s eyedrops both with and without air applied to the face. This effect was n ot obtained with balanced salt solution, During performance of the visual t ask for 10 or 30 min, basal blink rate decreased significantly, to about 40 % of the control value. Neither application of an air jet on the face nor a pplication of eye solutions of different viscosity modified this reduced bl ink rate. A low degree of ocular discomfort developed after performance of the visual task that was enhanced by air application to the face. This discomfort was reduced by pretreatment with ocular solutions, the elastoviscous eye solut ion being more efficient than the balanced salt solution. Interblink interv al duration was also more regular after treatment with the elastoviscous so lution. These data suggest that blink rate at rest is maintained in part by activat ion of sensory receptors of the cornea and conjunctiva, which are stimulate d by desiccation of the ocular surface. Reduction of eye blink frequency el icited by the performance of a visual task with a computer appears to depen d on central neural mechanisms that are quite independent of peripheral sen sory inputs. The reduction of blink frequency consecutive to computer use w as associated with a sensation of discomfort that was attenuated more effec tively by elastoviscous eyedrops than by regular balanced salt solution. (C ) 1999 Academic Press.