BLOG: The IOL sorting hat
Frequently we see the approval of a new lens implant offering a set of features and characteristics that serve a different set of patients.
Colleagues often tell me the process of picking a lens recommendation for a patient seems like a dark science, like the “sorting hat” in Harry Potter’s Hogwarts School of Witchcraft and Wizardry, whose mystical insights sort new students into different houses. But actually, there is some sense to choosing lenses for different patients. While each experienced refractive cataract surgeon has their own preferences and experience, I present the following as an approach that works well for many (Table).
Let’s assume that most patients want to have some degree of spectacle freedom, and most have at least a half diopter of anticipated astigmatism to be corrected with surgery. Let’s also divide patients among those who desire a binocular range of vision from distance to intermediate and perhaps near vs. those who are mostly motivated for binocular distance vision only. And separately let’s consider those who have had a previous positive experience with monovision or are at least open to taking a chance on monovision with their implants. Like many practices, we use a software package to automatically gain these insights from incoming patients and drive their understanding and acceptance of premium lenses.
Beyond patients’ expressed visual desires, it’s worthwhile to sort patients into one of three categories of ocular health. Let’s call them green, yellow and red. Each represents a stratum of ocular health and visual potential. Often, comorbidities can be treated to move a patient from red to yellow or yellow to green. For example, dry eye, basement membrane dystrophy, Salzmann’s nodules and some retinal pathology can respond well to medical or surgical treatment, and it’s generally best to address these comorbidities before performing cataract surgery.
Green category
Patients in the green category have essentially fully healthy eyes except for cataract. They have no prior refractive surgery, no corneal pathology, no significant dry eye and no meaningful maculopathy. These eyes are really candidates for any technology that suits them best. Assuming they want a binocular range of vision, the new PanOptix from Alcon, in our experience, provides much higher spectacle freedom than any previous presbyopia-correcting lens. In a study of 60 bilateral PanOptix implants I conducted with Quentin Allen and Michael Jones, we found 83% of patients never wore glasses for any activity. That’s more than double the rate of spectacle freedom we have seen with any previous lens or lens combination in 18 years. Any multifocal or extended depth of focus combination like Symfony (Johnson & Johnson Vision) is also reasonable for these patients, as is the Crystalens/Trulign lens system (Bausch + Lomb).
The Light Adjustable Lens (RxSight) is also a widely applicable lens. Although it doesn’t offer a significant range of vision in each eye, its precision is remarkable, making it suitable for those who are willing to give a bit of extra money and time for extra visits. Whether used binocularly for distance vision or for monovision, it’s a choice whose popularity is appropriately growing.
The Vivity lens from Alcon is another appealing offering with about 1.5 D of range of vision and no more glare and halos than a monofocal lens. This works extremely well for mini-monovision. Other options for these green patients who want monovision would be a toric monofocal or limbal relaxing incision, or a Crystalens/Trulign.
Yellow category
Patients in the yellow category have mildly abnormal eyes. Previous LASIK with total corneal higher-order aberrations less than 0.5 µm would fit here. Mild irregular astigmatism from previously treated corneal disease, mild dry eye, or even mild maculopathy would be in this category. Generally, these conditions should not reduce the best corrected vision any more than the cataract itself.
Multifocal and EDOF lenses should be approached with caution in this group of patients, including PanOptix, Symfony, Tecnis (Johnson & Johnson Vision) and ReSTOR (Alcon). Vivity or Crystalens/Trulign are good choices but with more limited expectations and less precision.
For binocular distance acuity, again the LAL, a toric monofocal, Crystalens/Trulign or a simple monofocal with an LRI are options. The same could also be used for monovision.
Red category — beware
The last and most challenging patients are those who have a loss of best corrected visual acuity from their comorbidities. RK and some PRK/LASIK eyes with higher corrections or significantly abnormal topographies fall in this category, as do keratoconus and eyes with mild maculopathy that reduces vision by one or two lines. For binocular range of vision, we don’t have many choices. The Vivity and Crystalens are probably the two safest but with very limited expectations. All multifocals and Symfony should probably be avoided. For binocular distance vision only, the LAL, toric monofocals, Crystalens/Trulign or LRIs can safely be employed — again with very tempered expectations. Monovision in patients with significant non-cataract ocular pathology is generally best avoided with limited exceptions. The vision in each eye simply generally doesn’t support a functional monovision result, and most patients end up wearing glasses.
Naturally, this set of guidelines may not apply to all patients. Many variables could alter the best choices for individuals, but consider both ocular health and patient desires to achieve satisfaction in a greater and greater percentage of patients as IOL technology continues to improve.
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