Purpose: To compare the fluorescein dye disappearance test with a new test for lacrimal drainage capacity, the drop test.
Methods: In the fluorescein dye disappearance test, 1 microliter of fluorescein solution was instilled into the conjunctival sac of normal subjects and of patients with epiphora. Fluorescence from the tear film was measured, and the rate of dye disappearance was calculated as a measure of tear drainage. In the drop test, drops of 10 microliters of lukewarm saline solution were repeatedly instilled into the conjunctival sac for 3 minutes. Excessive saline solution was then removed from the tear film and measured. The volume of saline solution drained by the lacrimal passage could thus be calculated.
Results: The fluorescein dye disappearance test showed, in normal subjects, a tear turnover rate of 10.9 +/- 3.1% (95% confidence interval) per minute, which was nor age dependent. The drop test showed a decreased lacrimal drainage capacity with increasing age in normal subjects, with a mean capacity of 150 +/- 38.5 microliters/3 min for those 41 to 80 years old. In patients with indoor epiphora, the fluorescein dye disappearance test values were significantly reduced. However, the fluorescein dye disappearance test could not differentiate among normal eyes, eyes with minor epiphora, or eyes with moderate epiphora. The drop test showed a significant decrease even in patients with minor epiphora and was further decreased with increasing severity of symptoms.
Conclusion: The drop test provides a quantitative measurement for lacrimal drainage function and is more sensitive than the fluorescein dye disappearance test.