Eyeworld

FALL 2026 | EYEWORLD | 59 R About the physicians Francesco Carones, MD Medical Director and Physician CEO ADVALIA Vision Milan, Italy Karolinne Rocha, MD, PhD Professor of Ophthalmology Medical University of South Carolina Storm Eye Institute Charleston, South Carolina References 1. Carones F. Residual astig- matism threshold and patient satisfaction with bifocal, trifocal and extended range of vision intraocular lenses (IOLs). Open Journal of Ophthalmology. 2017;7:1–7. 2. Rocha KM, et al. A compar- ative analysis of tolerance to induced astigmatism across various categories of intraocular lenses. J Cataract Refract Surg. 2026. Online ahead of print. 3. Rocha KM, et al. Tolerance to induced astigmatism with a monofocal intraocular lens designed to extend the depth of focus. J Refract Surg. 2023;39:222–228. 4. Ang RE. Small-aperture intra- ocular lens tolerance to induced astigmatism. Clin Ophthalmol. 2018;12:1659–1664. by Ellen Stodola Editorial Co-Director R esidual refractive error can leave a pa- tient less than satisfied after ophthal- mic surgery. Specifically, induced astig- matism is a common type of refractive error that may require additional consideration to ensure patient happiness. Lens choice in these patients can influence residual refractive error, though continual study and innovation have begun to take this into account, with some lenses now being more forgiving to residual refractive error. Francesco Carones, MD, and Karolinne Rocha, MD, PhD, have both researched this topic. Dr. Carones did a study 1 looking at four dif- ferent lenses, comparing the impact of induced astigmatism: AcrySof ReSTOR +2.5 D (Alcon), AcrySof ReSTOR +3.0 D (Alcon), AcrySof PanOptix (Alcon), and Tecnis Symfony ZRX00 (Johnson & Johnson Vision). He said the moti- vation for this research came from clinical expe- rience. "Even though current biometry, surgical planning, and intraoperative guidance have come a long way, we still don't know for sure what the refractive results of cataract surgery will be," he said. "Even when surgery is done very carefully, some patients still have a small amount of residual refractive cylinder. This may be attributable to factors such as wound healing, corneal biomechanics, or constraints in quantifying posterior corneal astigmatism." Residual refractive cylinder is not uncom- mon, Dr. Carones said. In standard practice, certain individuals may exhibit between 0.25 D and 0.75 D of residual astigmatism, despite meticulous surgical intervention. "For a patient with a monofocal lens, this level of astigmatism may not be clinically relevant, but for a patient with a multifocal or diffractive design, it may be considerably more obvious and irritating," he said. "This underscored the necessity of examin- ing 'tolerance to refractive error' across various IOL platforms, as a more forgiving lens could determine patient happiness or discontent." He had some predictions as to what his re- search would find before he started. "I thought that diffractive bifocal and trifocal lenses would be less tolerant of residual astigmatism," he said, because they work by splitting light into separate foci. As a result, every optical flaw could have a bigger effect. "On the other hand, I thought the extended range of vision (ERV) lens would be more forgiving because its design widens the depth of focus instead of splitting light. This could make it more resistant to slight changes from emmetropia." He noted that his lens choices for the study were intentional. At the time, these lenses were the most popular, high-end IOL designs utilized in clinics: two multifocal diffractive designs, one trifocal design, and one lens with a wider range of vision. "This let us see how the main catego- ries acted under the same simulated situations, which gave us a more complete picture instead of only focusing on one model," he said. Dr. Carones said the results of this research corroborated that simulated astigmatism exert- ed minimal clinical effects on visual acuity for the majority of lenses, however, patient satisfac- tion was more significantly affected by the level of refractive tolerance. He noted that the ERV lens showed superior resistance to more modest quantities of residual refractive cylinder than bifocal or trifocal designs. "When choosing lenses, you shouldn't just think about how likely they are to make patients independent of glasses; you should also think about how sensitive a certain design is to refractive errors," he said. "In practice, we can't always ensure flawless emmetropia, especially in eyes that have had surgery on the cornea, have irregular astigmatism, or have long axial lengths. In these situations, selecting a lens with greater tolerance, such as an ERV, may lead to increased satisfaction and a reduction in complaints of dysphotopsias or hazy vision. Surgeons must exercise exceptional precision in refractive planning and astigmatism correction for diffractive designs, as these lenses exhibit diminished tolerance to minor inaccuracies." Dr. Carones said the IOL landscape is con- stantly changing, even since his initial analysis was published. He noted that there are en- hanced monofocal and non-diffractive extended depth of field (DOFi) lenses that are better than the old ones. "These are meant to increase the depth of field while keeping the image quality good and possibly making them more tolerant of refractive error than older presbyopia-cor- recting versions," he said. Understanding lens tolerance to refractive error and astigmatism continued on page 60

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