The Pursuit of Precision in Refractive Lens Exchange

Postoperative results and patient satisfaction in refractive lens exchange (RLE) have greatly improved in the last decade, mainly thanks to innovations in IOL power calculation. Despite the efficiency and precision of these calculations, there is still more work to be done, Giacomo Savini MD observed during a presentation at the Global Refractive Summit.

“Just as with refractive cataract surgery, refractive surprise in RLE (defined as a prediction error higher than 0.5 D) is still between 10% and 20% of patients, as noted in literature,” he said. “What differs between these procedures is that RLE patients typically have much higher expectations and can be extremely dissatisfied by the slightest difference in the surgical outcome.”

And a distressed patient is a distress for the surgeon, Dr Savini emphasised. According to the literature findings, therefore, one or two patients in every ten RLE procedures can be unhappy with the results. He further noted that sometimes a single disgruntled patient is all it takes to ruin a whole working week.

Dissatisfaction rates are even higher among the myopes and hyperopes who most commonly undergo RLE. In eyes shorter than 22 mm or longer than 26 mm, the risk of refractive surprise is about 30%. Dr Savini noted these percentages are an improvement from the 40% risk calculated using older formulas a decade ago. However, the risk remains 50% in myopic eyes longer than 30 mm, so he does not recommend performing RLE in this group due to the risk of retinal detachment.

Between 2015 and 2025, a new generation of formulas largely replaced the previous options, resulting in substantial improvements in RLE outcomes. A key milestone arrived in 2022 with the ESCRS IOL Calculator, containing seven formulas now considered the gold standard for RLE: Barrett Universal II, Cooke K6, EVO, Hill-RBF, Hoffer QST, Kane, and Pearl-DGS. Dr Savini noted that, since its introduction, the ESCRS IOL Calculator is the most logical and accurate solution for eyes requiring RLE.

Despite these advances, Dr Savini observed a sense of a plateau in terms of new formulas and predictive precision, noting that more research is needed to overcome the dreaded 10–20% threshold of refractive surprise. Some of the most promising updates in the field come from Zeiss, which has a next-generation AI-based paraxial raytracing calculator in the pipeline. It is the first calculator developed by a company instead of a physicist, he noted. However, it currently supports only a few IOL models.

There is also a need for more accurate toric calculators, as refractive surprises remain common when correcting astigmatism.

Communication with the patient is still key to avoid having a tough time, he stressed. No matter how many instruments and formulas are available, there will always be a margin of error. A 300-micron difference in lens positioning for an anatomical variability, for example, can lead to a refractive defect.

“We are still very far from being perfect,” Dr Savini said. “It is still necessary to talk to the patients and inform them on the risk of a refractive error.” 

Giacomo Savini MD is an ophthalmologist in private practice at the Studio Oculistico D’Azeglio, Bologna, Italy. giacomo.savini@startmail.com