Methods and devices for monitoring intra-ocular pressure of a patient using a miniature implantable sensor device are provided herein. Methods include obtaining multiple pressure measurements each day during an increment of an extended monitoring period according to a sampling program and wirelessly transmitting stored measurement data and wirelessly charging the device. Measurements and data process is performed with low power requirements such that sampling can be performed hourly for at least one week using energy stored on the miniature device and measurement data can be transmitted and the device charged rapidly when an external portable data acquisition/charging device is held in proximity to the device. In one aspect, methods include switching between differing use modes and powering the sampling device with a high impedance battery by switching between a supercapacitor and the battery with a microcontroller to perform impedance conversion.