COVER FEATURE
Cataract Surgery Innovations
Point-counterpoint: ReZoom
by Asim Piracha, M.D.
With the recent CMS ruling and new advancements IOL technology, more and more ophthalmologists are offering presbyopic IOLs to their patients.
Discerning patients are also requesting presbyopic IOLs; therefore, it is imperative that ophthalmic surgeons become familiar with the strengths and weaknesses of each lens and be able to offer the best lens, or combination of lenses, that meets our patient’s needs.
What’s available?
The currently available presbyopic IOLs include the CrystaLens (eyeonics, Aliso Viejo, Calif.), ReStor (Alcon, Fort Worth, Texas), and the ReZoom (Advanced Medical Optics, AMO, Santa Ana, Calif.) The ReZoom lens is a refractive, distance dominant zonal aspheric lens with 2.6D of effective add; the ReStor lens is a combined refractive/diffractive lens with 3.2D of effective add; the CrystaLens is an accommodating monofocal lens. The goal of the presbyopic IOLs is to improve functional vision and reduce dependence on spectacle correction. All three lenses have benefits compared to standard monofocal IOLs in this regard and committed surgeons can be successful with all three lenses. Also, each lens may outperform the other lenses in specific applications. For instance, one can argue that the CrystaLens has the least incidence of night vision disturbances, while the ReZoom and ReStor outperform the CrystaLens in near vision. For this discussion, I will only be discussing the benefits of the ReZoom IOL over the ReStor IOL.
ReZoom
The ReZoom is a second generation refractive IOL that differs from its predecessor in two significant ways: optical design and lens material. The ReZoom is based on the AR40e platform with a hydrophobic acrylic optic, PMMA haptics, and OptiEdge triple-edge design that reduces internal reflections, edge glare, and posterior capsular opacity formation.
The most notable difference with the ReZoom optical design is that distance dominant zone 3 is 80% larger and the near dominant zone 4 is 55% smaller, which leads to better distance vision and less glare and haloes in mesopic conditions. There is also a 5% larger near zone 2 to provide better reading vision in photopic conditions. In reviewing the data of the two “multifocal” IOLs, it would appear that both lenses are excellent. For instance, both AMO and Alcon provide data stating that around 90% of the patients with their particular lens can see better than 20/40 distance and J3 near monocularly without correction and that over 90% of the patients in the clinical trials were spectacle independent.
So, which is better? The answer is: It depends.
On average, the ReStor provides better near vision compared to the ReZoom; however, the ReZoom provides better distance and intermediate vision. Also, the pupil size greatly affects the performance of these lenses. The ReStor lens will provide better reading vision in 2 mm pupils, but worse near vision in 5 mm pupils. On the other hand, the ReZoom will provide better distance vision than the ReStor in 2 mm pupils, but potentially more glare and halos in mesopic conditions. A distinguishing feature of the ReZoom is that this lens not only provides near and distance vision like the ReStor, but there is also a separate focal point for intermediate vision. This is accomplished with the aspheric transition zone b/n the near and distance zones and is termed Balance View Optics. With essentially a trifocal optic, this lens gives the full range of vision for not only near and distance, but also functional intermediate vision.
Intermediate vision is critical for individuals with active lifestyles, where working on the computer, cooking, and grocery shopping are part of their daily activities. In comparison, the ReStor is a bifocal IOL that has no separate focal point for intermediate vision. One can “push out” the near focal point to overcome the excessive add by aiming for a slightly hyperopic endpoint, which shifts the defocus curve to the left and leads to a more comfortable reading distance. Unfortunately, there is also an equal amount of loss in uncorrected distance vision when a hyperopic post-op goal is achieved. With the ReZoom, because the effective add creates a more comfortable reading distance, one can target emmetropia to provide excellent distance vision with good near and functional intermediate vision. Lastly, the ReZoom is a refractive IOL at all pupil sizes, which theoretically leads to better contrast sensitivity, whereas the ReStor is a diffractive IOL and only uses 84% of transmitted light when the pupil is 2 mm and 86% of transmitted light when the pupil is 3 mm in diameter.
Bottom line
What all this means to our patients is that the ReStor lens is a bifocal IOL that does not provide any functional intermediate vision unless one aims for a hyperopic post-op refractive error, and this leads to worse uncorrected-distance vision. Therefore, the ReStor does provide good near vision, but no intermediate vision unless distance vision is sacrificed. Also, in photopic conditions (or a 2 mm pupil) the lens is a diffractive IOL that limits the amount of light transmission and is essentially a bifocal IOL with equal power for near (38%) and far (43%). This can be an issue when performing activities in daylight—like driving a car, playing golf, or at the beach. It is true that the ReZoom is also affected by a small pupil and becomes highly distant dominant (83%) with functional intermediate vision (10%), but no near vision. In mesopic conditions (or a 5 mm pupil), the two lenses also perform differently; the ReStor is highly distance dominant (84%) with minimal near vision (10%), while the ReZoom has more near (30%) and intermediate (10%) power, with less distance power (60%). This can lead to more glare and halos at nighttime with the ReZoom and worse near vision with the ReStor in mesoptic conditions like reading a restaurant menu.
Overall, I believe both the ReZoom and the ReStor lenses are successful in making our patients spectacle independent for most activities. Each lens has a “sweet spot” and one must understand the patient’s desires pre-operatively to better choose the ideal presbyopic lens implant.
Dr. Piracha is not an AMO consultant; however, AMO did arrange for Dr. Piracha’s submission.
ABOUT THE PHYSICIAN
Asim Piracha, M.D., practices at the John Kenyon Eye Center, with offices in Jefferson, Ind., and Louisville, Ky. Contact him at 812-288-9011 or asimrp@yahoo.com.
