CATARACT EWAP JUNE 2023 23 A s advanced -technology IOLs have become more mainstream and more continue to enter the market, surgeons have refined their understanding and use of these technologies. The EyeWorld Cataract Editorial Board wanted to gain insights on the best formulas and what a reasonable adaptation period looks like with these modern IOL technologies. EyeWorld reached out to Li Wang, MD, PhD, Linda Tsai, MD, and Kamran Riaz, MD, for their expertise in these areas. “Formula choice is an interesting topic these days,” Dr. Riaz said. “A plethora of newer, multivariable formulas have emerged in the past few years. These formulas incorporate biometric variables besides axial length (AL) and keratometry (K), such as central corneal thickness (CCT), lens thickness (LT), and anterior chamber depth (ACD). The more recent introduction of posterior corneal power measurements, such as total keratometry (TK) with the IOLMaster 700 [Carl Zeiss Meditec], allows potentially more accurate measurements of total corneal power. Given that TK values were designed to be compatible with existing IOL formulas, significant research has gone into optimizing use of TK in regular eyes, eyes receiving presbyopia-correcting IOLs, and post-laser vision correction eyes.” While none of the physicians said that they use specific formulas for specific presbyopia-correcting IOL platforms, they had some insights to achieve the most accurate calculations. Dr. Riaz said that total keratometry measurements in formulas may help improve outcomes with toric trifocal IOLs, but he said that the conventional keratometry is better than TK with multifocal IOLs. 1,2 “I primarily use the Johnson & Johnson Vision IOL platform for presbyopia-correcting advanced-technology IOLs. For most presbyopia-correcting IOLs on this platform … I use a multivariable formula (with the ESCRS IOL Calculator) and ideally want all seven formulas to agree,” he said. “I give preference to the EVO, Barrett, and Cooke K6 formulas in case of discrepancies. I use the K values for this calculator but will use the TK values for trifocal IOLs (which I rarely do, unless the patient specifically requests them). I like to look at the Barrett TK formula that uses the TK values (on the IOLMaster 700 printout) as well for these premium IOL patients. Aiming closest to plano (even erring about 0.12 D hyperopic) is an ideal strategy since any myopic refractive error decreases objective and subjective visual function.” This is a patient with good angle alpha and angle kappa values on ray tracing aberrometry (iTrace). Corneal higher-order aberrations were less than 0.4 µm on Scheimpflug tomography (Pentacam). This patient is a potential candidate for diffractive optics presbyopia-correcting IOLs. Source: Kamran Riaz, MD Contact information Riaz: kamran-riaz@dmei.org Tsai: tsai@wustl.edu Wang: liw@bcm.edu Advanced-technology IOLs: Formulas and adaptation by Liz Hillman EyeWorld (US) Editorial Co-Director This article originally appeared in the April 2023 issue of EyeWorld. It has been slightly modified and appears here with permission from the ASCRS Ophthalmic Services Corp.
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