A Clinical Trial Report: A Nasolacrimal Stent with Shape Memory as an Advanced Alternative to Silicone Products

Silicone tubes have been used as nasolacrimal stents for over 40 years due to their excellent elastic and biocompatible properties. Nonetheless, long-standing clinical issues persist, including biofilm formation, insufficient tear drainage, and invasiveness during insertion through occluded ducts. To address these issues, a prospective, single-arm, open-label clinical study was performed with 16 patients over 20 weeks using a shape memory stent. The shape memory function reduces invasiveness through temporarily thinned insertion by pulling, followed by diameter expansion upon accumulation of inner-body heat energy (on-site programming). The unique semicrystalline surface suppresses bacterial adhesion due to the spreading of anti-fouling crystalline ridges and the consequent narrow widths of the adhesive amorphous regions, effectively suppressing bacterial adhesion and subsequent biofilm formation. Furthermore, in aligned patterns, water-impenetrable crystalline ridges facilitate the flow-down of tears to the absorbable amorphous regions, thereby improving the drainage efficiency. Consequently, the clinical success rate (Munk's score of 0-1) reached 78.6% with a significant decrease in tear meniscus height over 20 weeks and postoperative fluorescein dye disappearance test grades ≤2 in all patients. Four cautionary symptoms occurred, leading to early stent removal in two patients due to corneal abrasion and insertion-site granuloma. These results suggest that the shape memory stent is a promising noninferior option to the silicone stent.