Current CGM systems are invasive, costly and can give skin problems. We recently showed that measurement of glucose in tear fluid is possible and comparable with the results of the Freestyle Libre. We now show the results in 24 additional patients.
24 subjects with T1D, already wearing a Freestyle Libre device, were recruited from Haaglanden Diabetes Centre. In fasting state, the device was applied by the ophthalmologist. Glucose levels from the blood and interstitial fluid were recorded every 15 minutes, the current measured with tear glucose sensor was recorded continuously. The eye surface and lower eyelid and tolerability were regularly checked. A calibration algorithm to convert tear glucose to blood values was built using a neural network model and cross validated.
13 subjects were male, 11 were female. Apart from mild irritation due to probe wires exiting the eye no side effects were found and all patients could finish the 5-hour test. The MARD values for the 24-patient subset was 16.7. The MedARD was 13.3. The Abbott Freestyle Libre device generally shows an MARD of 15.7 on the first day dropping to 11.9 by day 2. Comparing this to the published data from Abbott, the NovioSense device is almost identical considering that the device was allowed only 5 hours performance time before the MARD was measured.
We have demonstrated that the NovioSense Tear glucose sensor measures blood glucose values from tears comparably to the Abbott Freestyle Libre and may become a good alternative for invasive devices.