ENGINEERING STRIP-TYPE DEVICES FOR LOWSTIMULUS TEAR COLLECTION
Yong Chan Cho1, Seung Ho Lee2, Young Bin Choy1,2,3
1Seoul National University, South Korea;
2Institute of Medical & Biological Engineering, Medical Research Center, Seoul National University, South Korea;
3Korea University College of Medicine, South Korea
Non-invasive diagnosis and self-monitoring of diseases have been considered as a new paradigm in healthcare. In this sense, basal tear can be a promising target for its high correlation with many disease markers. However, collection of basal tear is uneasy as eye surface is very sensitive. With currently-available methods, collection is very slow (1 μl/min), needing a long-time contact, hence discomfort or pain to patients. Therefore, reflex tear production and tissue damage would be highly probable, which may dilute concentration of disease markers. For this reason, tear is collected with professionals in hospital, with topical anesthetics. To resolve this, we sought to establish a proper design for the collector tip that is in contact with the eye surface for low-stimulus collection of basal tear. Considering less sensitivity, we chose inferior palpebral conjunctiva (IPC) as the region for tear collection. In this work, we fabricated the tip in round flat shape, where edges were also rounded. We prepared 3 distinct tip areas (i.e., A1 (area: 1π/4 mm2), A3 (area: 3π/4 mm2) and A4 (area: 4π/4 mm2)) and pressed each against the IPC at depths of 2, 3 and 4 mm. Area of damaged tissue and time for recovery were assessed. Our findings showed that no tissue damage was inflicted by the A4 strip with pressing depth from and below 3 mm (pressure: 19.70 kPa). At 4 mm pressing depth, the tissue damage was not severe and was recovered in less than 4 h. For the A1 strip, severe tissue damage was observed from and above 3 mm, which took more than 8 h to be recovered. Our results, therefore, demonstrated that among the A1, A3, and A4 strips tested in this work, the A4 strip with the largest contact area was most promising for low stimulus tear collection from the IPC.