Update in tonometry. Phosphene and rebound tonometries, self-tonometry and technologies for the future

The Proview phosphene (eye-pressure) tonometer and the Rebound tonometer ICare are relatively new devices basically different from the Goldmann applanation tonometry (GAT). Both technologies will be presented in this review with respect to their principle, their technique, their advantages and limits, as well as their accuracy, the IOP measurements agreement with GAT, and the influence of central corneal thickness on the reliability of these measurements. Because the current data base for the interpretation of glaucoma disease course and its management are still relatively small, the development of a continuous, accurate, reliable and harmless monitoring of IOP over 24 hours is strongly desirable in the future. Approaches for self-tonometry and devices such as smart contact lenses which can take the IOP from the corneal surface have been developed with this goal. The future will probably confirm whether telemetric IOP monitoring with an implantable active microsystem allows a reliable IOP monitoring or not. In any case, active implants will open new and important perspectives in the diagnosis and the treatment of glaucomatous optic neuropathy.