Tear Breakup Dynamics: A Technique for Quantifying Tear Film Instability

Abstract

These methods allow objective quantification and tracking of the phenomenon of tear breakup. Our results suggest that tear breakup stresses the corneal surface, resulting in stimulation of underlying nociceptors. The tear film of dry eye subjects was less stable than controls. They had a larger AB measured from the last video frame before MBI (i.e., just before blinking) than did controls. This perhaps reflects adaptation to the repeated stress of tear instability in dry eye.

Quantitative Analysis of Tear Film Fluorescence and Discomfort During Tear Film Instability and Thinning

“…The differences between groups reached statistical significance (Mann-Whitney U test, P < 0.05) for ''irritation'' and ''pricking.'' These results agree with our previous studies, which indicate that TBU in eye opening trials was associated with irritation, stinging, and burning, 15,20,22 but also suggest that diminishing corneal fluorescence over time without TBU is associated with an irritative affective response. The difference in discomfort experienced by subjects in the BU and BUmin groups is illustrated in Figures 2 and 3, which show individual data for the change in discomfort during trials reported by four of the subjects in this study.…”

“…23 Subjects were then seated behind a slit lamp biomicroscope fitted with a digital video camera, and 2 lL of sodium fluorescein (2%) was pipetted into the tested eye while the other eye was patched shut. As in previous studies, subjects were asked to keep the tested eye open as long as possible 20,21 while they turned a knob (potentiometer) to indicate the level of discomfort in the tested eye on a 0 to 10 scale (0 ¼ no discomfort and 10 ¼ very uncomfortable). 22 Following each trial, subjects rated their overall discomfort on separate integer scale of 1 (no discomfort) to 10 (very uncomfortable) and then indicated the level of irritation, stinging, burning, pricking, and cooling on visual analogue scales (VAS).…”

“…20,21 For this analysis, TBU was defined in the traditional clinical sense, as areas of dark spots, streaks, or amorphous areas in the fluorescent corneal tear film. 29,30 A clinically trained observer masked to subject and trial information identified the threshold PI that included all areas of TBU in the final image of each trial.…”

“…Previously, we have shown that tear film breakup (TBU) is associated with sensations of burning and stinging and results in increased symptoms of ocular irritation, implying that increased tear film hyperosmolarity or other adverse conditions may occur during TBU, stimulating ocular surface nerves. [20][21][22] In this study, we quantified global thinning and regional TBU by employing a pixel-based analysis of fluorescence and compared the concurrent sensory responses of TBU versus tear thinning during the interblink period. We hypothesize that changes in corneal fluorescence during the interblink period are due tear film thinning and/or TBU, and that both are associated with sensory stimulation to the cornea.…”

Agreement between Automated and Traditional Measures of Tear Film Breakup

“…Studies have shown fluorescein tear break up time (FBUT) to be different between dry eye and normal patients, 1-3 and it is often used within clinical research to monitor the effectiveness of treatments. 4-6 However, this measure has been shown to have modest repeatability at best when the same examiner performs the test.…”