A passive pressure sensor for continuously measuring the intraocular pressure in glaucomatous patients

Objective. ­ The main risk factor for the development of glaucoma, a retinal disease leading to blindness, is an increase in the intraocular pressure (IOP). Reducing this IOP can be obtained by eye drops but unfortunately the disease can still progress because IOP increases are painless, can fluctuate and, thus remain undetected during a visit to an ophthalmologist. The "MATEO" ANR project aims to develop sensors embedded in a contact lens for continuously IOP monitoring. Materials and methods. ­ Pressure sensors were produced by MEMS technology and tested with pig eyes obtained at a local slaughterhouse. Solution was injected by 50 L steps in the eye with a Hamilton syringe while IOP was monitored in parallel with a TonoVET system and an industrial pressure transducer inserted in the injection tubing system. Results. ­ Our first pressure sensor prototypes were generated and inserted in a lens compatible with eye application. A wireless system was developed to excite the sensor. At same time, it was recorded the data in components inserted into spectacles and a pocket recorder. In parallel, we showed that injecting a solution in the eye anterior chamber triggered an IOP increase smaller and more stable than injections in the posterior chamber. Finally, a direct correlation was observed between IOP measured on the corneal surface with the TonoVET and the pressure transducer placed close to eye injection point. Discussion. ­ Our results indicate that our in vitro model on pig eyes is adequate to test our new lens sensor. Finally, the pressure sensor was successfully inserted in contact lens opening the way for their in vitro and in vivo preclinical validation.