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S.E. Varner, C. Panzan, L.J. Faia, A.C. Barnes, E. de Juan; Development of a Minimally Invasive IntravitrealImplant for Drug Delivery . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4214.
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Purpose: To develop a new generation of intravitreal drug delivery implant which can be implanted and explanted in a clinic-based setting. Methods: Minimally invasive design criteria were established based upon prior experience with vitreo-retinal surgical instrumentation. Stainless steel prototype devices were fabricated using traditional machining methods. The device design and method of implantation were refined iteratively based upon test results in cadaveric porcine and human eyes, as well as in acute rabbit implantations. Results: A helical implant was developed which allows for maximal surface area while minimizing the size of the implantation site. This device is inserted through a self-starting transconjunctival 25 gauge (0.5 mm diameter) site. The "wire" diameter is 25 gauge, while the helical shape allows the device to be "dialed" clockwise into the eye. The overall length of the device is less than 1 cm, ensuring that it rests outside the visual field. In the implanted configuration, an attached circular hub rests against the sclera, preventing the device from floating freely into the viteous. The conjunctiva slips over the scleral hub and, coupled with the shape of the intravitreal portion of the device, holds the device securely against the sclera. The wound created by this procedure is leakage free and requires no sutures for closure. Thus far, in acute experiments, the device is easily removable by engaging the scleral hub and "dialing" the implant counterclockwise. Drug delivery from the device can be achieved through a number of mechanisms. Initial experience with a polymer coating indicates that a sustained release of corticosteroid (1.9 ug/day) could be maintained for over 1 year from such device. Conclusions: A retrievable intravitreal device was created that is capable of delivering therapeutic levels of corticosteroid for up to one year. The implantion of such a device could ultimately be performed as a clinic-based procedure, which would be comparatively less expensive, shorter in duration, and carry fewer risks than surgical implantation.
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