Eyeworld

SUMMER 2025 | EYEWORLD | 37 R Relevant disclosures Gorovoy: None McKee: Bausch + Lomb, Haag Streit, JelliSee, Zeiss Wortz: Alcon, Bausch + Lomb, Johnson & Johnson, Omega Ophthalmics, Rayner Contact Gorovoy: mgorovoy@gorovoyeye.com McKee: mckeeonline@mac.com Wortz: 2020md@gmail.com What's next McKee said there have been good improvements in the IOL material scene in recent years. At this point, he said most IOL research is focused on creating a functional and predictable accom- modating IOL. This technology will require a highly flexible material, like silicone or collamer. "Innovation in IOL material is likely to move toward improving accommodation function in the future," he said. Dr. Gorovoy said he's happy with IOL mate- rials at this point but would like to see new de- signs, specifically those that reduce or eliminate dysphotopsias. He would also like to see better three-piece lenses for scleral fixation, as well as piggyback lenses. Dr. Wortz's wish list also wasn't necessarily for better materials, but he said he would like to see lenses with larger optics for patients with larger pupils, a true accommodating IOL, and anything that's more biocompatible that reduces or eliminates PCO. Additionally, future IOL plat- forms need to be designed on an exchangeable platform. "Since no material is perfect, and we cannot predict the future pathology of the eye or what a patient will tolerate, I think we need to have a better backup plan for IOL exchanges of all lenses regardless of material. We should not risk damaging the bag or zonules in order to remove an optic that is not functioning for a patient," he said. Dr. McKee said to really understand IOL materi- als, it's important to understand the definitions of the common attributes that determine their behavior. Here's how Dr. McKee described the following terms. Abbe number: This measures the degree of chromatic aberration of a lens (change of re- fractive index vs. wavelength). The human eye cannot detect chromatic aberration in a lens if the Abbe number is above 40. The crystalline lens typically has an Abbe number around 45. Asphericity: This measures deviation from a perfect sphere, expressed as the Q value. Neg- ative Q values indicate a prolate lens; positive Q values indicate an oblate lens. Aspheric IOLs can alter spherical aberration, which can affect contrast sensitivity vs. depth of field. In ophthal- mology, Q factor typically refers to the corneal asphericity. Considering corneal Q factor, an IOL can be chosen to minimize spherical aber- ration to increase contrast sensitivity or allow for a small amount of spherical aberration to increase depth of field at minimal expense to contrast sensitivity. Hygroscopy: This is the propensity of a material to adsorb water. Hydrophobic IOLs with low hygroscopy tend to form glistenings. Glass transition temperature (Tg): This is the temperature at which a polymer changes from a rigid (glassy) state to a flexible state. A high Tg results in a non-foldable IOL (PMMA). Foldable IOLs do not unfold easily below their Tg. The lowest Tg and thus fastest unfolding IOL material is silicone. Refractive index: Higher refractive index IOLs can be thinner but may also have more surface reflection and dysphotopsias (hydrophobic acrylic). Lower refractive index IOLs may have less of these problems but are thicker and may require a larger incision size (silicone). "Ideally, we want an IOL that is foldable for re- ducing incision size, optically clear with minimal chromatic dispersion (high Abbe number), a refractive index near the natural lens (1.4, to prevent reflections and dysphotopsias), the largest optical zone, the lowest incidence of dysphotopsias, the highest biocompatibility, and that does not opacify under any conditions in the eye. This is asking a lot, but I think we are fairly close to that ideal material." Definitions

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