Response of the lipid and aqueous layers of the precorneal tear film to horizontal saccades. Novel findings and a new paradigm

Abstract

AbstractPurpose To consider the effect of horizontal saccades on the lipid and aqueous layers of the tear film.Methods i. The interference pattern of the tear film lipid layer (TFLL) was studied in the left eye of 6 normal subjects, using the DR‐1TM video‐interferometer. Images were recorded continuously within a single interblink, with the eye in the primary position to capture the TFLL pattern: a. at least 1 second after the blink, when the pattern had stabilised and b. immediately after return to the primary position following a nasal saccade. ii. In a separate study, the movements of the aqueous layer, stained with fluorescein, were recorded during horizontal saccades, using standard slit‐lamp video equipment.Results i. In all subjects, the TFLL pattern after the first return saccade strongly resembled the initial pattern, but showed some degradation with multiple saccades. ii. The stained, precorneal aqueous layer moved with the cornea during saccades, with minimal displacement which was rectified on return to the primary position.Conclusion Two alternative explanations are offered for these findings: i. The precorneal TFLL is ‘glued’ to the aqueous subphase so that these fluid layers move together with the cornea, during horizontal rotations of the eye. ii.Cooling of the tear film during the interblink, causes an increase in stiffness of the viscoelastic TFLL, so that it behaves like a stable carapace, uninfluenced by movements of the aqueous layer. Further experiments are planned to resolve these alternative hypotheses.