Flanged Scleral Fixation: Thermoplastic Properties of Suture Materials and Implications for Flange Geometry

Background: Flanged scleral fixation techniques are increasingly used in the management of intraocular lens dislocation and aphakia. However, complications such as conjunctival erosion and scleral migration remain a concern. Flange geometry may play a critical role in anchoring stability. This study investigates the thermoplastic properties of various suture materials to identify optimal conditions for flange formation. Methods: A disposable electrocautery device with a power supply and tip temperature of 392°C was used for standardised application. Seven suture materials were used: polypropylene (6/0), polyamide 6 (6/0), polyamide 6.6 (6/0), vinylidene fluoride-co-hexafluoropropylene (PVDF) (6/0), polyester (5/0), and polytetrafluoroethylene (PTFE) (5/0 and 6/0). All sutures were heated 0.5, 1, 2, 3, 4, and 5 mm from the distal end and examined in 4 repeat measurements. The prepared flanges were photographed and measured using a digital microscope. The flange dimensions and geometry were assessed. Ratios of flange length to flange width and flange diameter were calculated. Results: All suture materials except polyamide 6.6 (6/0) and PTFE (5/0) formed a flange shape due to the increase in temperature as demonstrated by repeated measurements with a high degree of reproducibility. While polypropylene and PVDF took on a mushroom/rhomboid shape, the flange shape of polyamide 6 and polyester was spherical. The flange geometry of PTFE was funnel-shaped with sharp edges. With increasing duration of heat exposure, the flange length of polypropylene and PVDF increased more significantly than the flange width. Conclusion: Polypropylene and PVDF demonstrate favorable thermoplastic properties for flanged scleral fixation, enabling reproducible flange formation with short heating times. A heating length of approximately 1 mm appears optimal for controlled flange geometry. Further biomechanical and in vivo studies are required to validate clinical performance.