Frequent spontaneous eyeblink activity associated with reduced conjunctival surface (trigeminal nerve) tactile sensitivity

Abstract

Background: A number of recent studies have reported high spontaneous eyeblink rate (SEBR) values in apparently normal subjects, but the reasons for this are unclear.

Methods: An assessment was made of SEBR, in 60 educated adult male subjects aged between 22 and 40 years, over a period of 5 min in silence. Half of the subjects were classified as having frequent eyeblink activity. All subjects also had their corneal and conjunctival touch (tactile) sensitivity assessed with a Cochet-Bonnet aesthesiometer immediately after the video recording of SEBR.

Results: SEBR ranged from 4.6 to 43.5 (mean 18.6) eyeblinks/min. The SEBR was 26.8 +/- 6.0 eyeblinks/min for those with frequent eyeblink activity as compared to just 10.3 +/- 3.5 eyeblinks/min for those with normal eyeblink activity (p < 0.001). There was no difference in palpebral aperture or exposed ocular surface area between the two groups. The average central corneal sensitivity was only marginally different between the two groups (56.8 +/- 2.8 mm vs 58.5 +/- 2.3 mm) but the conjunctival threshold sensitivity was substantially different (at 23.8 +/- 4.3 mm vs 28.5 +/- 3.5 mm; p < 0.001). SEBR was inversely correlated with the conjunctival sensitivity in those with frequent eyeblink activity (p < 0.001).

Conclusions: Our study provides a clue as to the mechanism of inhibition of spontaneous eyeblink activity, namely that a certain level of ocular surface (conjunctival) sensitivity is required to keep SEBR low.