Edward B Moss1, Graham E Trope. 1. Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada. 5ebm@queensu.ca
Abstract
PURPOSE: To measure closing pressure in a series of new Model FP7 silicone Ahmed Glaucoma Valves (AGVs), using an in vitro gravity-driven system, in which closing pressure was measured directly from a dual manometer/pressure reservoir. METHOD: A straight length of tubing served as an open manometer, which connected via a 3-way stopcock to the inlet of the AGV submerged under 1.5 cm of balanced saline solution (BSS). Six AGV were assessed in 5 sequential trials and the mean inlet pressure at 90 minutes was recorded as the closing pressure. After testing, a single valve was primed a second time using greater force and retested. Control trials were performed with a submerged 26-G cannula opening directly into the BSS bath. RESULTS: At 90 minutes, the 6 valves equilibrated at a mean inlet pressure of 7.1 mm Hg, with a range from 1.4 to 13.5 mm Hg. Closing pressures at or less than 5 mm Hg were measured in half (3/6) of the valves tested. The average flow of BSS across the valves in the final 30 minutes was less than 1.5x10(-2) microL/min. In the single valve reperfused under greater pressure, the closing pressure increased. CONCLUSIONS: Model FP7 AGVs, in vitro, exhibit significant variability in closing pressure, with half closing at intraocular pressures considered potentially problematic in clinical situations. The results of the high-pressure perfusion experiment suggest that more research into the priming process is required so a precise description can be developed for surgeons.
PURPOSE: To measure closing pressure in a series of new Model FP7 silicone Ahmed Glaucoma Valves (AGVs), using an in vitro gravity-driven system, in which closing pressure was measured directly from a dual manometer/pressure reservoir. METHOD: A straight length of tubing served as an open manometer, which connected via a 3-way stopcock to the inlet of the AGV submerged under 1.5 cm of balanced saline solution (BSS). Six AGV were assessed in 5 sequential trials and the mean inlet pressure at 90 minutes was recorded as the closing pressure. After testing, a single valve was primed a second time using greater force and retested. Control trials were performed with a submerged 26-G cannula opening directly into the BSS bath. RESULTS: At 90 minutes, the 6 valves equilibrated at a mean inlet pressure of 7.1 mm Hg, with a range from 1.4 to 13.5 mm Hg. Closing pressures at or less than 5 mm Hg were measured in half (3/6) of the valves tested. The average flow of BSS across the valves in the final 30 minutes was less than 1.5x10(-2) microL/min. In the single valve reperfused under greater pressure, the closing pressure increased. CONCLUSIONS: Model FP7 AGVs, in vitro, exhibit significant variability in closing pressure, with half closing at intraocular pressures considered potentially problematic in clinical situations. The results of the high-pressure perfusion experiment suggest that more research into the priming process is required so a precise description can be developed for surgeons.
Authors: Marta Ibarz Barberá; Jose Luis Hernández-Verdejo; Jean Bragard; Javier Burguete; Laura Morales Fernández; Pedro Tañá Rivero; Rosario Gómez de Liaño; Miguel A Teus Journal: Transl Vis Sci Technol Date: 2021-11-01 Impact factor: 3.283
Authors: Inês C F Pereira; Rosanne van de Wijdeven; Hans M Wyss; Henny J M Beckers; Jaap M J den Toonder Journal: Eye (Lond) Date: 2021-06-14 Impact factor: 3.775