Study describes the biomechanics of flanged intrascleral haptic fixation of 3-piece IOLs

This study was a laboratory investigation of the flanged intrascleral haptic fixation (FISHF) strength of 4 various 3-piece intraocular lenses (IOLs).

Study design

Investigators compared the FISHF of the CT Lucia 602, the Tecnis ZA9003, the LI61AO, and the AcrySof MA60AC. They used cautery to create flanges on the distal end of the haptics, and 27- and 30-gauge needles to pass them through cadaveric human sclera. They tested flange lengths of 0.5 mm, 1.0 mm, and 2.0 mm. A mechanical tester was used to determine the forces required to remove the flanged haptic from the sclera and disinsert the haptic from the optic. The force test was repeated 5 times and averaged for each lens.

Outcomes

The force required to disengage the haptic from sclera with a 30-gauge needle was greatest for the CT Lucia 602 IOL, with no significant difference for haptic optic disinsertion force. There was no difference in flange diameters of 1.0 mm or 2.0 mm across all lenses, indicating that a 1.0 mm cautery is sufficient for stability.

Limitations

The ex-vivo nature of this study is a limiting factor, because tissue temperature and long-term fibrotic changes of scleral tissue can impact stability. In addition, force was applied directly perpendicular and may not account for all forces that may occur in vivo.

Clinical significance

This study adds data to the literature about the biomechanics of the CT Lucia 602, which anecdotally has been favored for FISHF. It also helped determine the effect of cannula diameter and flange melt length on disinsertion forces.