Differentiation of lipid tear deficiency dry eye by kinetic analysis of tear interference images

Objective: To use kinetic changes to characterize tear interference images in patients with lipid tear deficiency (LTD) dry eye. Methods: We used a DR-1 camera to digitize and analyze sequential images of tear interference on the central 8 mm of the cornea at the start of complete blinking in 11 healthy volunteers and 8 patients with LTD and noninflamed meibomian gland dysfunction. Main Outcome Measures: We studied tear lipid spread time and pattern, stability of the lipid after spread, and distribution of thickness in a prospective, case-control study. Results: On complete lid closure, the lipid spread was horizontal in healthy eyes but vertical in LTD (P<.001). Mean +/- SD lipid spread time was 0.36 +/- 0.22 seconds in healthy eyes but 3.54 +/- 1.86 seconds in LTD (P<.001). Conventional DR-1 grading could not distinguish these groups (P=.32). Mean +/- SD lipid film thickness in healthy eyes was 74.5 +/- 6.9 nm, thicker than the 43.8 +/- 10.6 nm in LTD (P<.001), and this result was confirmed by qualification with intensity histogram (P<.001). Conclusions: Kinetic analysis of the tear interference revealed distinctive differences in the time and pattern of lipid spread and the distribution and stability of resultant lipid thickness between healthy subjects and patients with LTD. This method can be coupled with others for formulating effective therapies for patients with dry eye.