In irregular eyes, which advanced-technology IOL would you implant?
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Light Adjustable Lens
There are different types of corneal irregularities.
I usually divide them into those that are surgically induced due to a history of laser vision correction and those that are due to preexisting natural causes such as dystrophies, degenerations or some forms of dry eye, which result in an unpredictable corneal curvature. In both cases, IOL power prediction can be challenging.
The Light Adjustable Lens (RxSight) is theoretically the perfect solution for these difficult corneas because through postoperative titrations in IOL power, the refractive outcomes can be tailored to the patient’s preferences. However, it is important to ensure that the corneal irregularity comes with a minimum amount of anterior high-order aberrations on aberrometry measurement. If aberrations are high, those eyes will do better with a pinhole optics lens because the Light Adjustable Lens does not correct high-order aberrations.
Preoperative assessment should include a careful evaluation of the anterior curvature of the cornea by topography and anterior Placido disc images to make sure that the level of corneal irregularity is low enough to warrant a Light Adjustable Lens. Another way to assess this is to see how the patient’s manifest refraction was before they developed the cataract. If the patient’s vision was correctable and good enough with the use of spectacles, we can be fairly sure that corneal high-order aberrations are low enough for them to do well with this type of lens. On the other hand, patients who used to wear rigid gas permeable contact lenses are likely to have higher-than-normal high-order aberrations and would do better with a pinhole optics lens rather than a Light Adjustable Lens.
I love implanting the Light Adjustable Lens in patients with corneal irregularities due to previous vision correction, provided that their central aberrations are low. These patients do well because the main issue with IOLs after refractive surgery is challenging, and the current formulas often lead to unintended postoperative refractive error. An implant that enables us to adjust the lens power postoperatively to personalize the refractive outcomes according to the patient’s preferences and expectations is the perfect lens for these types of irregular corneas.
Marjan Farid, MD, is an OSN Cornea/External Disease Board Member.
Small-aperture Apthera
I have a long history with the small-aperture Apthera IOL (AcuFocus).
I was involved in the development of this product for more than a decade, as well as in the initial U.S. trial as medical monitor. In the U.S., the lens itself is not labeled for irregular corneas, but it has clearly found that niche as an excellent application.
The depth of focus that it imparts is a significant attribute: We get about 1.5 D of extended range and can actually make that even more functional by targeting slight myopia. If we target –0.75 D or –0.5 D, because the depth of focus goes in both directions, we do not lose much in distance and still can achieve 20/20 vision, with up to +2 D for reading. The Apthera is implanted in one eye, but rather than monovision, the visual experience we obtain is what we call “blended vision” because you do not have a situation in which you have alternating suppression of images. Your distance vision is binocular, and near vision is enhanced.
The off-label use of this lens in irregular corneas has been a major plus for the ability to mitigate fluctuations in vision. If you have a post-RK cornea that has fluctuations in the curvature over the course of the day, you can significantly mitigate this effect with the Apthera. It is a huge benefit, and patients who have that difficulty are incredibly happy.
There are patients with atypical topographic patterns that may not reach the level of a keratoconus diagnosis but still catch the attention of the clinician. These are the types of individuals in which there is a corneal contribution to the image quality that diminishes from the absolute best macular potential. If they are looking for a premium option, my choice is the Apthera. I can provide them with the best quality distance vision because the small aperture will mitigate the aberrations of the cornea, as well as the depth of focus for intermediate and near vision, which is desirable. This lens has significant potential to improve quality of vision and quality of life, and it is a welcome new option for surgeons who want to offer a premium experience to every patient, including those with irregular eyes.
John A. Vukich, MD, is an OSN Presbyopia Board Member.
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