New IOL Materials Offer Clear Opportunity
Research opens clear path to improved IOL materials. Roibeard Ó hÉineacháin reports
After decades of dominating the intraocular lens (IOL) material market, hydrophobic and hydrophilic acrylates may soon face competition from non-acrylate materials, said Gerd Auffarth MD, PhD, FEBO, Ruprecht Karl University of Heidelberg, Heidelberg, Germany. Today’s non-acrylate materials offer superior optical properties and better biocompatibility without risk of latent opacification.
Rigid PMMA lenses, foldable silicone lenses, and early acrylic foldable lenses came onto the market in the ’80s and ’90s. However, by 2017, hydrophilic and hydrophobic acrylates accounted for 85% of global IOL market share for IOL materials while PMMA accounted for 12%, and silicone for a mere 3% of market share, Dr Auffarth told the Association for Research in Vision and Ophthalmology (ARVO) 2021 Annual Meeting.
The advantages of hydrophobic acrylate IOLs include a higher refractive index, which allows for thinner IOLs, and adhesive properties that give good rotational stability and a low rate of posterior opacification (PCO). Alternatively, hydrophilic IOLs can be easily moulded into any desired shape and are flexible enough to allow for injection through very small incisions.
Whether hydrophobic or hydrophilic, opacification is a problem with all acylate material lenses. In hydrophobic IOLs, this takes the form of “glistenings”, microvacuoles that result from fluid seeping into the empty spaces within the material’s polymer structure. Optical bench testing indicates glistenings have little effect on modular transfer function (MTF) but significantly increase stray light.
In hydrophilic IOLs, opacification is an outcome of calcification, which can result from defects in the material and changes in the aqueous milieu—as may occur during intraocular surgery and in patients with conditions such as uveitis and diabetes.
Dr Auffarth and his associates at the university’s David J Apple Laboratory for Ocular Pathology have developed means of testing the susceptibility of lens materials to glistenings and calcification. He noted that over the past 20 years, this type of research has led to the development of virtually glistenings-free hydrophobic acrylic IOLs such as the modern AcrySof IOLs and the Clareon IOLs (Alcon).
A non-acrylate material called cross-linked polyisobutylene (xPIB) is now under investigation as an IOL material, Dr Auffarth said. He added xPIB has been FDA approved since 2004 for use in coronary stents, and research has shown it has very good biocompatibility. It has a high refractive index (1.52) and is highly elastic, meaning it could be used for large-optic IOLs implantable through a sub-2.0mm incision. It also induces less chromatic aberration. Moreover, its molecular structure ensures xPIB is not susceptible to glistenings or calcification.
Gerd Auffarth: firstname.lastname@example.org