Influence of mouth and jaw movements on dynamics of spontaneous eye blink activity assessed during slitlamp biomicroscopy.

BACKGROUND

To evaluate oculo-mandibular interactions during evaluation of spontaneous eye blink rate (SEBR) of normal young adult human subjects while seated at a slitlamp.

METHODS

Repeat video recordings of five minutes duration were made on 76 young adult emmetropic subjects aged 18-25 years. The subjects were instructed to direct their gaze horizontally toward a distant target with the entire cornea of the left eye illuminated with a broad beam cobalt blue light. Repeat recordings were made: (a) on the following day in silence in group one; (b) immediately in silence for group two; and (c) immediately either while holding their mouth open slightly or while responding to casual conversation for groups three and four.

RESULTS

For group one the averaged SEBR values for the first and second recordings were 13.5 and 14.6 blinks/minute, and similar results were obtained for group two if the subjects were relaxed (for example 13.9 and 12.0 blinks/minute). A slight, but statistically significant, time-related decline in SEBR was usually noted. For non-relaxed (restless) subjects exhibiting spontaneous mouth and jaw movements while being videographed, the averaged SEBR values were around 27 blinks/minute. For groups three and four, analyses of those individuals who managed to maintain a mouth open posture for the video recordings, the averaged SEBR was 7.2 blinks/minute, while those engaged in casual conversation had an averaged SEBR of 20.3 blinks/minute.

CONCLUSIONS

Mouth and jaw movements and a non-relaxed state can substantially affect spontaneous eye blinking.