Continuous monitoring of intraocular pressure: rationale and progress toward a clinical device

Intraocular pressure (IOP) is a dynamic physiologic parameter with regular circadian variations and unpredictable short-term and long-term fluctuations. Current methods of measuring IOP are suboptimal with a typical clinical practice only performing periodic IOP measurements during regular office hours. Diurnal and 24-hour IOP measurements obtained on an in-patient basis can increase measurements but are inconvenient and expensive, and do not allow ambulatory monitoring of IOP. The goal of continuous IOP monitoring is to provide automated 24-hour recording of ambulatory IOP. Continuous IOP monitoring involves 2 complementary paradigms. Temporary noninvasive monitoring, possibly involving a contact lens-based pressure sensor, would be used to measure 24-hour IOP on a periodic basis. Permanent monitoring would be more invasive, using an implantable pressure sensor. Despite numerous previous attempts at continuous IOP monitoring, a device suitable for clinical use is not yet available. However, devices currently in development for permanent IOP monitoring seem to be nearly ready for human testing. The technologic issues for temporary monitoring may be greater than for permanent monitoring.