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Pui-Chuen Hui, James Chodosh, Claes H Dohlman, Eleftherios I Paschalis; In Vivo Optical Monitoring of Intraocular Pressure in Boston Keratoprosthesis. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2419. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular hypertension can lead to glaucoma, an important postoperative complication of prosthokeratoplasty. Managing glaucoma requires frequent intraocular pressure (IOP) measurements. Yet conventional tonometers are incompatible with the rigid corneal implant in keratoprosthesis (KPro) eyes. To fill this technological gap we fabricated a KPro integrated with a fiber-optic pressure sensor (PS). The device was evaluated in vitro and in vivo by longitudinal IOP measurements in rabbit eyes.
Long-term device stability was monitored via continuous manometry with two fiber-optic Fabry-Perot PSs (Fiso Technologies; 300μm in diameter, 2.1mm long) submerged in a water column. For the device fabrication, a PS was introduced into the periphery of the Boston KPro’s optical stem. IOP was measured by coupling light with an external fiber-optic probe and an optical correlator. Optical coupling, robust against eye motion during clinical exam, was expedited by implementing a novel self-alignment scheme using NdFeB micro-magnets fitted over the probe fiber and the PS. PS-endowed KPros were implanted in 6 New Zealand White rabbits which were followed for 6 weeks with weekly IOP measurements validated against the objective intracameral manometry (IM).
The pressure reading (spanning ~50mmHg) was stable over 2 years in vitro after a drift of 1.6±0.0mmHg in the first 71±3 days. Implantation of the PS-endowed KPro was uneventful. The fiber-optic access to the PS remained clear for successful optical interrogation over the study period. The mean of the absolute differences between the optical IOP and the IM measurements gradually rose from 4.0±2.5mmHg (7 days post surgery) to 30.0±14.7mmHg (51 days post surgery). OCT imaging showed retroprosthetic membrane (RPM) formation on all 6 KPros.
In vitro characterization, integration and in vivo interrogation of a fiber-optic PS in the Boston KPro were demonstrated. Longitudinal validation of the PS against IM and OCT imaging suggest the PS measurement deviation is likely attributed to RPM formation on the device's posterior surface. Strategies to minimize RPM formation may reduce IOP drift in vivo. Our preliminary demonstration shows promise in improving glaucoma management in KPro patients via an IOP-sensing KPro.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Fig. 1: (a) A Boston KPro fitted with a fiber-optic PS and a micro-magnet: i). Top; ii). side view. (b) A sensor-integrated KPro implanted in a rabbit eye.
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