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A. Todani, M. A. Fava, S. A. Melki, C. H. Dohlman; Measurement of IOP With Intraocular Pressure Transducer. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5220.
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To demonstrate the implantation technique & tolerance of a novel wireless silicone-encased pressure transducer unit inside the eyes of unrestrained rabbits. The device can conceivably provide a reliable way to measure the IOP in situations where it is difficult to register with present technology, for instance in eyes with keratoprosthesis implants.
The transducer, manufactured by Mesotec GmbH (Hannover, Germany), is a fully digital ultra miniature system, integrating pressure sensing, data handling and telemetry on a single microchip. It is donut-shaped with 11.3 mm external diameter, 7 mm internal diameter and 0.9 mm thickness, and weighing about 0.1 gram. The microchip is connected to a telemetry coil and requires no internal power source. It generates very little heat and has a transmission range of up to 5 cm. The data is received using an external reader unit.The transducer was initially tested for calibration in enucleated bovine eyes. It was sterilized with ethylene oxide. In an adult NZW rabbit, an 11 mm corneal-limbal incision was made and the crystalline lens was extracted by extra-capsular technique. The transducer was placed in the iris sulcus and the eye closed with interrupted 10-0 nylon sutures. Daily observations and weekly full clinical examinations were performed.
The transducer was well-tolerated, with minimal corneal irritation and intraocular inflammation. Although there was significant corneal edema after the surgery, this resolved gradually over the next 2 weeks with the use of topical steroids and antibiotic drops. The pressure obtained with the transducer showed a good correlation with that obtained with a Tonopen.
Early results seem to indicate that the Mesotec transducer can be easily implanted and tolerated. A larger followup study is currently being undertaken to demonstrate its long-term tolerance.
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