Spontaneous eye blink activity during slitlamp-based assessments.

Clinical Relevance: Slitlamp-type assessments of eye blink activity with head and chin support need to consider time-related differences that can occur.

Background: Previous studies have not assessed the predictability of changes in spontaneous eye blink rate occurring during slitlamp observations.

Methods: Video recordings were made of eye blink activity of 85 young adults who were either emmetropic or spectacle wearers for refractive errors between -8.25 D and +8.25 D. After an initial adjustment period of one to two minutes positioned at the slitlamp (including the time after removing spectacles), participants had a five minutes recording made in silence while seated with forehead and chin support and directing their gaze to a high-contrast target on a distant whiteboard under ambient luminance of 35 cd per square metre.

Results: The mean spontaneous eye blink rate values over five minutes were 13.4 ± 3.1 blinks/minute (± SD), ranging from 7.4 to 20.8 blinks/minute. Overall, incomplete eye blink events were noted 39 times in the total of 5,704 recorded (that is, 0.68 per cent of all eye blinks). There was a progressive decline in averaged spontaneous eye blink rate values (r = 0.897, p < 0.05), with 70.6 per cent of the participants exhibiting a higher spontaneous eye blink rate value in the first minute compared to the fifth minute. The inter-participant variability in spontaneous eye blink rate also progressively declined over time, but there was no detectable difference in either averaged values or the variability in spontaneous eye blink rate in relation to refractive error.

Conclusions: In slitlamp-based assessments of eye blink activity, a small progressive time-related reduction appears likely but is not obviously related to visual blur in ametropic individuals.