PURPOSE: Flanged intrascleral haptic fixation (FISHF) is a useful method to secure intraocular lenses (IOLs) in eyes without capsular support. Biomechanical studies were conducted to support the use of this technique. DESIGN: Laboratory investigation METHODS: Haptics of 3-piece IOLs were passed through cadaveric human sclera using 30-gauge and 27-gauge needles. Flanges were created by melting 1.0 mm from the haptic ends using cautery. The forces required to remove the flanged haptic from the sclera and disinsert the haptic from the optic were measured using a mechanical tester and a custom-fabricated mount. RESULTS: The mean FISHF dislocation force using 30-gauge needles was greatest with the CT Lucia 602 (2.04 ± 0.24 N) compared to the LI61AO (0.93 ± 0.41 N; p=0.001), ZA9003 (0.70 ± 0.34 N; p=<0.001), and MA60AC (0.27 ± 0.19 N; p<0.001). Using 27-gauge needles with the CT Lucia resulted in a lower dislocation force (0.56 ± 0.36 N, p<0.001). The FISHF dislocation force was correlated with the flange-to-needle diameter ratio (r=0.975). The FISHF dislocation forces of the CT Lucia and LI61AO using 30-gauge needles were not significantly different from their haptic-optic disinsertion forces (p=0.79 and 0.27 respectively). There was no difference in flange diameter between 1.0 mm and 2.0 mm haptic melt lengths across the IOLs (p=0.15-0.85). CONCLUSIONS: This data strongly supports the biomechanical stability of FISHF with the polyvinylidene fluoride haptics of the CT Lucia using small diameter instruments for intrascleral tunnel creation. 1.0 mm of haptic may be the optimal melt length.