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Sidath E. Liyanage, Ian Eames, Romesh I. Angunawela, G W. Aylward; Fluid Dynamics of Intraocular Gas and its Impact in Macular Hole Surgery. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4499.
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Intraocular gas tamponade has become an integral part of macular hole surgery. It is thought to improve success rates of hole closure by providing a tamponade which either forces the healing hole against the retinal pigment epithelium or isolating the hole from liquefied vitreous humor. Various measures have been employed to lengthen the duration of contact between the healing macula and the tamponade agent, including (1) face-down posturing, (2) the use of longer-acting gases and (3) lens extraction to increase the volume of gas used. We aim to investigate whether these practices are effective in increasing this duration of contact by using fluid dynamics modeling.
The volume of gas absorbed was calculated as a function of initial volume and time, using the absorption rates of different intraocular gases - air, 20% sulfur hexafluoride and 14% perfluoropropane. This volume of gas was used to derive the angle of retina tamponaded by the bubble. The area of retina tamponaded is dependent both on the angle of retina tamponaded and the direction of gaze. This relationship was used to determine when face-down posturing becomes necessary for posturing. Using physiological measurements, the effect of lens extraction on duration of tamponade was calculated.
Using intraocular air as an example, apposition between the hole and the bubble is maintained with the head in a neutral position and horizontal gaze until day 2 post-operatively. Full face down posturing is not needed until day 4. If sodium hexafluoride or perfluoropropane is used, horizontal gaze will maintain the tamponade until day 5 and day 16 respectively. Removing the lens will potentially increase the length of tamponade by 3%.
Based on the modeling of intraocular gas dynamics following macular hole surgery, maintaining a horizontal gaze in a neutral head position will result in an air bubble tamponading the hole until day 2 post-operatively. After this period, face down positioning will be required to maintain tamponade. Longer acting gases such as sulfur hexafluoride and perfluoropropane will significantly increase the duration of this tamponade. Lens extraction does not significantly increase the length of tamponade.
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