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Yong Joon Kim, Kyung-Seek Choi, Sungkil Jo, Youngcheol Joo; A computational study of the pressure burden on localized retina during vitrectomy. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5787.
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There is significant correlation between infusion pressure of vitrectomy device and manometric intraocular pressure. But infusion pressure does not provide the informations about intraocular pressure-gradient during surgery. This computerized study was conducted to analyze the static and dynamic pressure and quantify the pressure burden on localized retina during fluid-fluid, fluid-air, and air-gas exchange.
A computational model of the eye was designed using three-dimensional modeling software which contains the broad physical modeling capabilities needed to model flow and turbulance. Intraocular fluid dynamics was simulated with a conventional mesh-based techniques. We used the pressure-based coupled algorithm, which is combination of continuitiy equation and momentum equation, to analyze the fluid dynamics. Parameters including gauge of instruments, intrusion length of aspiration instrument into eye, infusion pressure were altered for each individual run.
In situation of short intrusion of instrument and and small gauge system, high pressure gradient was revealed. When aspiration instrument deeply inserted into vitreous cavity, fluid flows seems to be interfered with instrument. But the point of retina which opposite to infusion cannula revealed highest dynamic and static pressure, consistently. When aspiration instrument extracted from vitreous cavity, sudden decreasing of IOP was observed. After 2 seconds, overall IOP became lower than infusion pressure and stably maintained. In this condition, intraocular pressure-gradient was increased up to 2 mmHg with the various infusion pressure and gauge of instrument during fluid-fluid exchange, and higher during fluid-air and air-gas exchange .
Using computer simulations, we could quantify the pressure burden on each point of retina in various conditions. Although the computational model is somewhat different from real clinical situation, our study provided the conceptual information about pressure-burden induced mechanical damage on retina. In our simulations, high pressure-gradients which can damage the localized retina were noticed during fluid-air and air-gas exchange with small gauge system and high infusion pressure. Although fluid-fluid exchange seems to be relative safe procedure than fluid-air or air-gas exchange, caution is always needed in performing vitrectomy with small gauge system and high infusion pressure.
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