After metering a measured dose of sensor chemistry directly into the eye region, a miniaturised fluorescence spectrometer emits an eye-safe level of light at the excitation wavelength of the specific fluorescent dye in the eye sensor chemistry.

The instrument uses a photodiode to record the reflected fluorescence emission spectrum (through FRET) produced by the eye sensor, and this is proportional to the concentration of glucose in the lachrymal fluid in contact with the sensor chemistry. Developing the metering and sensing systems to provide measurement and monitoring using optical techniques was a complex task and several patents now exist to protect these developments. Renfrew Group is involved in the ongoing development of this patented system.