GRAVITY, BLINK RATE, AND LACRIMAL DRAINAGE CAPACITY

PURPOSE: To investigate the influence of gravity and blink rate on lac rimal drainage capacity and to learn whether lacrimal pump function ca n be measured with the drop test. METHODS: The drop test: for lacrimal drainage capacity was performed in 20 test subjects, aged 12 to 30 ye ars. Drops of a known volume of lukewarm saline solution were repeated ly instilled in the rear film for 3 minutes. Excessive saline solution was then removed, and the volume drained by the lacrimal passages was calculated. The drop test was performed both with the nasolacrimal du ct. in a 45-degree position and with the nasolacrimal duct in a horizo ntal position, The drop test was performed two times in each position, with the individual reading and not reading, A lower blink rate was i nduced by reading. RESULTS: There was a high correlation between blink rate and lacrimal drainage when the nasolacrimal duct was in a horizo ntal position. The volume drained with each blink was approximately 2 mu l. However, when gravity acted upon the fluid in the lacrimal sac-n asolacrimal duct in the direction of the tear flow, the lacrimal drain age capacity showed a significant but variable increase, and there was no significant correlation between blink rate and lacrimal drainage c apacity. CONCLUSIONS: Lacrimal drainage capacity in young individuals was significantly affected by both blink rate and gravity. Lacrimal pu mp function can be measured quantitatively with the drop test.