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 width to flange length and flange width to suture 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.