Abstract
Purpose :
To determine the scratch and shear mechanical properties of novel, hydrophobic acrylic intraocular lens (IOL) materials in the wet state relative to a previous base material and a competitive IOL platform, across a range of commercially available dioptric powers.
Methods :
A nanoscratch tester (CMS Instruments, Needham, MA) with a diamond stylus was used to induce ramped-load scratches on the surface of four unique hydrophobic materials (MX60, MX60E-4, MX60E-5, and Acrysof IQ) across a range of commercially available intraocular lens diopter powers used in cataract surgery. Each lens type was subjected to a progressive load of 0.3-80 mN using an 8 micron radius, 60 degree conical diamond stylus, while submerged in saline solution. A scratch velocity of 5 mm/minute and a loading rate of 199.25 mN/minute were used in all scenarios. After scratch generation was complete, an optical microscope was used to examine the morphologies of the induced scratches to determine the onset of material cracking and relative vulnerability of each material to incidental damage from surface directed forces.
Results :
Qualitatively, the MX60, MX60E-4, and MX60E-5 material samples exhibited superior resistance to the surface scratching when compared to the Acrysof IQ material. This relative invulnerability to surface scratches was maintained over the range of physiological powers tested with only a trace increase in vulnerability noted in the high dioptric group. The MX60E subgroups tested appeared to have an earlier onset of surface failure relative to the MX60 group, but further examination with stereomicrograph imaging of the scratched lenses did not reveal any significant differences in performance among any of the MX60 samples tested.
Conclusions :
Assessment of the relative surface strength of various intraocular lenses is beneficial for surgeons concerned with the impact of incidental scratches may have on optical performance an implanted IOL. Both MX60 and MX60E hydrophobic acrylic materials outperform Acrysof IQ material in terms of scratch resistance in this bench study. No significant difference in scratch resistance was detectable across all subtypes of MX60 material tested.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.