IOL biomaterials: What every surgeon needs to know

IOLs: What Every Surgeon Needs to Know is an editorially independent video podcast series from Ophthalmology Times, hosted by Douglas D. Koch, MD. The series highlights clinical pearls, expert perspectives, and emerging advances in IOL technology and cataract surgery. Koch is a professor and the Allen, Mosbacher, and Law Chair in Ophthalmology at the Cullen Eye Institute at Baylor College of Medicine in Houston, Texas.

Watch the full episode: IOLs: What Every Surgeon Needs to Know | Ep. 1: IOL Biomaterials

This Q&A is an excerpt from the first episode, in which Koch is joined by guest Liliana Werner, MD, PhD, the H.A. and Edna Benning Presidential Endowed Chair and codirector of the Intermountain Ocular Research Center at the John A. Moran Eye Center in Salt Lake City, Utah, for a discussion covering the key classes of IOL materials, calcification risk, the light-adjustable lens, and new materials on the horizon.

Note: Transcript edited for clarity and length.

Douglas D. Koch, MD: Can you give us an overview of the categories of biomaterials currently used in IOL manufacturing?

Liliana Werner, MD, PhD: In general terms, there are 2 classes of biomaterials currently used for the manufacture of IOLs: acrylic and silicone. Acrylic lenses may be rigid—made of PMMA [poly(methyl methacrylate]—or foldable. Foldable acrylic lenses are further divided according to their surface and bulk properties into hydrophilic acrylic or hydrophobic acrylic. Silicone lenses, the second class of material, are all foldable. An important point is that each hydrophilic acrylic lens and hydrophobic acrylic lens is not the same; these are general classes of materials, and different copolymers can be used in their manufacture, generating different properties such as refractive index and mechanical characteristics. The same applies to silicone lenses, where different generations of materials have been used, with more modern versions tending to have a slightly higher refractive index.

Koch: In the US, hydrophobic foldable acrylics dominate while hydrophilic acrylics are used much less than in Europe. Why the difference?

Werner: The hydrophilic acrylic materials are very flexible and can be made very thin for insertion through incisions under 2 mm, which is quite popular in Europe. In the United States, I believe they are not as popular because of the issue of calcification. This is a class of material that has a higher tendency to calcify. I am not saying that all hydrophilic acrylic lenses are going to calcify; the rate of calcification is actually low. However, we receive explanted lenses from around the world and see them every single week.

The issue of calcification is interesting. There are instances where a relatively large number of the same lens from the same manufacturer calcifies, usually because of some change in the manufacturing procedure or polishing. But there is also a distinct, localized form of calcification in a round area on the anterior optic surface and subsurface, observed with any hydrophilic acrylic lens and not related to any particular manufacturer. This form is usually secondary to some secondary surgery. Initially, it was observed after procedures such as membrane peeling surgery, involving injection of air or gas into the anterior chamber, but the same pattern has since been seen after posterior segment surgeries, including retinal surgery and even intravitreal injections. The question is whether we always know in advance if our patients are going to need a secondary surgery down the road.

Koch: Can silicone IOLs calcify as well?

Werner: Silicone lenses may also calcify, but we always observe this in eyes with asteroid hyalosis. The calcification is different in character; the deposits are only on the posterior optic surface and are very superficial. They can actually be removed with YAG [yttrium aluminum garnet] laser, but because of the large supply of calcium phosphate in the vitreous, there will be reaccumulation of deposits afterward.

Hydrophobic acrylic lenses, to the best of my knowledge, I have never seen a single case of calcification proved by laboratory analysis of the explanted lens. I have heard about cases, but I have never seen one that was truly confirmed.

Koch: There is considerable variety even within hydrophobic acrylic materials. In the US, 3 hydrophobic acrylic materials are from Alcon (AcrySof/Clareon), Johnson & Johnson Vision (Tecnis), and Bausch + Lomb. Are there particular differences you want to highlight?

Werner: Standard hydrophobic acrylic lenses have a water content of less than 0.5%; the AcrySof material from Alcon is a good example. More recently, a new generation of hydrophobic acrylic materials with higher water content has emerged, ranging from approximately 1.5% up to 7%, while still remaining classified as hydrophobic acrylic. The advantage of these materials is that they are not prone to hydration-related phenomena such as glistenings and subsurface nanoglistenings. These phenomena rarely lead to explantation, but microvacuoles and a whitish appearance of the [IOL] optic under slit lamp examination are not desirable, and with a significant number of them, there is always potential for increased light scattering.

Koch: Can you tell us about the light-adjustable lens, which allows postoperative modification of IOL power?

Werner: The light-adjustable lens is made of a silicone material that contains unpolymerized molecules that can move within the optic upon application of near-UV light. This allows the power of the intraocular lens to be adjusted noninvasively in the postoperative period. The lens is FDA approved and growing in the market. Our laboratory performed the preclinical studies of this material in the rabbit model.

An important point is that patients must wear UV-protective glasses until the final lock-in of the lens power. There is evidence in the literature that even with the newer light-adjustable lens featuring an active shield, uncontrolled polymerization can occur with exposure to outdoor light. [Adherence to] this requirement is quite important.

Koch: What new materials are on the horizon?

Werner: There is a new class of materials that has recently been described, based on cross-linked polyisobutylene. This material is being used for the manufacture of an IOL in China. Considering parameters such as refractive index, mechanical properties, and flexibility, this is a very hydrophobic, very flexible material with a relatively high refractive index and low chromatic aberration—interesting characteristics.

The September and October 2025 issues of the Journal of Cataract & Refractive Surgery include papers on this material: One is a preclinical rabbit study demonstrating biocompatibility similar to a standard hydrophobic acrylic lens, and the other is a clinical study with a limited number of patients followed for 1 year, showing promising results.^1,2 I look forward to longer-term data.

Douglas D. Koch, MD

Koch is a professor and the Allen, Mosbacher, and Law Chair in Ophthalmology at the Cullen Eye Institute at Baylor College of Medicine in Houston, Texas, and host of the Ophthalmology Times podcast IOLs: What Every Surgeon Needs to Know.

Liliana Werner, MD, PhD

Werner is the H.A. and Edna Benning Presidential Endowed Chair and codirector of the Intermountain Ocular Research Center at the John A. Moran Eye Institute in Salt Lake City, Utah.

References

1. Zhao Y, Jin J, Yang F, et al. Evaluation of safety and stability after intraocular lens implantation using a novel material-crosslinked polyisobutylene: a preliminary study. J Cataract Refract Surg. Published online May 23, 2025. doi:10.1097/j.jcrs.0000000000001685

2. Qassoom A, Kleinmann G. Biocompatibility evaluation of a new material for intraocular lenses. J Cataract Refract Surg. 2025;51(10):909-914. doi:10.1097/j.jcrs.0000000000001708