Comparison of the biomechanical behavior of foldable intraocular lenses

Abstract

Purpose: To compare a standardized battery of biomechanical laboratory tests to assess the performance of popular foldable intraocular lenses (IOLs). Setting: Biomedical testing facilities, Alcon Research, Ltd., Fort Worth, Texas, USA. Methods: Using industry-standard biomechanical testing techniques, 1- and 3-piece foldable IOLs (Alcon AcrySof® MA60BM, MA30BA, SA30AL, SA60AT; Allergan Sensar® AR40, PhacoFlex® II SI-40NB; Bausch & Lomb Soflex® LI61U; Pharmacia & Upjohn CeeOn® 920) and a 1-piece all-poly(methyl methacrylate) (PMMA) IOL (Alcon MZ30BD) were tested under identical conditions with regard to (1) tensile/elastic properties by comparing haptic pull strength and haptic elongation and (2) compression properties by comparing haptic compression forces, haptic compression force decay over time, and axial displacement. All tests were performed with the IOLs submersed in a controlled-temperature water bath (mean 35°C ± 2°C [SD]). Results: For all IOLs, the ultimate elongation and pull strength of the haptics before failure was highest with the Alcon SA30AL and SA60AT. Similarly, the force required to compress haptics to a prescribed 10.0 mm diameter was least with the SA30AL and the SA60AT lenses. These 1-piece lenses also showed the least decay of residual compression force as a function of time. Optic displacement along the optical axis with haptic compression to 10.0 mm was least with the Alcon 1-piece IOLs and the all-PMMA control IOL. Conclusion: AcrySof 1-piece SA30AL and SA60AT IOLs demonstrated superior biomechanical characteristics over other foldable IOL designs.