Temporal progression and spatial repeatability of tear breakup

This study used image analysis to compare the temporal progression and spatial reoccurrence of the area of tear film breakup (AB) in dry eye and normal subjects.

Tear breakup was induced in 10 control and 10 dry eye subjects during the Staring Tear Breakup Dynamics (S-TBUD) test, which involves keeping one eye open for as long as possible, termed the maximum blink interval (MBI). Video imaging of tear film fluorescence measured the onset and progression of the AB. AB location and area were mapped. The progression of ABs from the first trial, the rate of tear breakup or dry area growth rate (DAGR), and the overlap of ABs in three successive trials 5 minutes apart were computed by custom MATLAB programs.

The final AB before the blink was significantly greater (average, 30.7%+/-12.5% vs. 16.1%+/-9.2%) and the MBI was significantly less (average, 19.5+/-9.0 seconds vs. 56.5+/-38.9 seconds) among dry eye subjects compared with controls (p<0.05, Mann-Whitney U test). The DAGR was four times greater among dry eye subjects, who also showed significantly more tear breakup in the central cornea than controls (p<0.0001, Mann-Whitney U test). When the final image from three successive trials was overlapped, tear breakup occurred more often in the same location in three trials than would be expected by the overlap of independent points.

Structural influences such as the "black line" or corneal lid defects appeared to influence the recurrence of breakup in the same region. The S-TBUD quantitative image analysis technique demonstrates that the tear film of subjects with dry eye continues to rapidly destabilize after an initial first break; thus, a low TBUT was combined with a high DAGR. The central corneal region of subjects with dry eye appeared especially susceptible to increased tear breakup when compared with controls.