8 EyeWorld Asia-Pacific | December 2024 FEATURE Pathways to Precision and Perfection – Light Adjustable Lens (LAL) vs. IOL Formulae The theme for this year’s Combined Symposium of Cataract & Refractive Societies (CSCRS) session is “Pathways to Precision and Perfection”, and the idea is to provide different perspectives on 3 alternative pathways to perfection. Light Adjustable Lens (LAL) vs. IOL Formulae by David Chang, MD Light Adjustable Lens (LAL) Adoption of the Light Adjustable Lens (LAL; RxSight) and its newer iteration, the LAL Plus, is accelerating in the United States. Through a combination of greater surface convexity and negative spherical aberration, the LAL Plus may provide up to a diopter of extended depth of focus in a slightly myopic eye. Cataract surgery with LAL implantation is performed using standard techniques. Approximately 3-4 weeks later, the patient is refracted and a slit lamp based digital light delivery device (LDD) system is used to deliver UV light in a precisely programmed pattern to induce a predictable change in the shape and refractive power of the optic. Treatment times range between 60-120 seconds. After the newly-adjusted refraction is confirmed several days later, a “lock-in” dose is given with the LDD, at which point no further refractive change will occur. We have many excellent non-adjustable, advanced technology IOLs and hitting the refractive target remains crucial for these eyes. A common question is: do we really need adjustable IOLs given how much better our formulas and biometry have become? I would answer that when we miss the refractive target, the confounding variable is usually the corneal curvature measurement, rather than an inaccurate formula. The very best formulas still yield different results due to corneal variability in patients with dry or abnormal ocular surfaces. Because the biometry/ IOL calculation printout is derived from a single moment in time, our practice routinely repeats the entire biometry/ calculation process twice (IOL Master 700, Zeiss) and I am struck by how frequently the resulting predictions differ due to variable keratometry. For me, the ultimate verdict was when Warren Hill, MD reported in an ASCRS presentation last April that he chose the LAL for both his and his wife’s eyes. Beyond achieving greater precision in hitting emmetropia, there is a second major benefit that comes with using an adjustable IOL. Some patients – perfectionists and engineers for example – agonize preoperatively over what specific refractive target they want. With the LAL, these patients can wait to try out their binocular pseudophakic vision postoperatively, and then confirm or modify their refractive preference based on their daily experience. This, and the fact that they won’t have diffractive ring halos, dramatically relieves the anxiety for this type of patient.For another example, many patients prioritize not having to wear readers, and don’t mind distance glasses. These individuals can customize and determine the optimal amount of myopia in one or both eyes based on their binocular postoperative experience. LAL patients
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