Computational and Experimental Analysis of an In Vitro Microfluidic Experimental Setup on Testing Molteno, Ahmed Valve and Ex-Press Implants and Their Critical Comparisons.

Abstract

PURPOSE/AIM OF THE STUDY\nResearchers have investigated glaucoma drainage devices in various in vitro experimental setups to overcome their disadvantages. In this study, it is aimed to perform in vitro analyses of glaucoma drainage devices that are actively utilized for glaucoma treatment.\n\n\nMATERIALS AND METHODS\nA new in vitro experimental setup is constructed and the first outcomes of numerical simulations and experimental trials are shared. Firstly, an in vitro experimental setup is designed and simulated in ANSYS Fluent, then assembled/fabricated using microfluidic equipment. Secondly, computational fluid dynamics results are expressed as pressure losses through an Ahmed Valve implant, a Molteno drainage device, an Ex-Press implant for physiological flow rates.\n\n\nRESULTS\nIn the scope of this study, Ahmed Valve (valved), Molteno (non-valved), Ex-Press (orbital shunt) implants, are examined numerically using computational fluid dynamics tools. Results are compared with in vitro studies of the proposed experimental setup. Poiseuille and Reynolds numbers versus pressure drop characteristics of tested glaucoma drainage devices are also obtained using in vitro microfluidic experimental setup. In the range of 1.6 - 2.5 µl/min, Ahmed Valve implant created an active and effective pressure drop of 5.6 to 12 mmHg. Ahmed Valve and Molteno showed similar characteristics in terms of Poiseuille and Reynolds numbers variations with pressure drop across implants. Ex-Press, opposing Molteno and Ahmed Valve, gave a reciprocal correlation between pressure drop and Po.\n\n\nCONCLUSIONS\nHigh resemblances of pressure drops between computational fluid dynamics results and in vitro microfluidic experimental results proved that the setup will be a better choice compared to syringe pump type setups for testing different glaucoma drainage devices at the same conditions. In conclusion, a new glaucoma drainage device should be equipped with a slimmer but larger end plate and a valve mechanism similar to Ahmed Valve in the perspective of intraocular pressure drop performance.