EVALUATION OF THE LACRIMAL DRAINAGE FUNCTION BY THE DROP TEST

PURPOSE: To compare the fluorescein dye disappearance test with a new test for lacrimal drainage capacity, the drop test. METHODS: In the fl uorescein dye disappearance test, 1 mu l of fluorescein solution was i nstilled into the conjunctival sac of normal subjects and of patients with epiphora. Fluorescence from the tear him was measured, and the ra te of dye disappear ance was calculated as a measure of tear drainage. In the drop test, drops of 10 mu l of lukewarm saline solution were r epeatedly instilled into the con junctival sac for 3 minutes. Excessiv e saline solution was then removed from the tear him 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% confid ence interval) per minute, which was not age dependent. The drop test showed a decreased lacrimal drainage capacity with increasing age in n ormal subjects, with a mean capacity of 150 +/- 38.5 mu l/3 min for th ose 41 to 80 years old. In patients with indoor epiphora, the fluoresc ein 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 min or epiphora and was further decreased with increasing severity of symp toms. CONCLUSION: The drop test provides a quantitative measurement fo r lacrimal drainage function and is more sensitive than the fluorescei n dye disappearance test.