Ophthalmologists have had a new expansion of technology in the world of presbyopia-correcting lenses ushered in by the many variations in add power among existing platforms as well as a new class of extended depth of focus (EDOF) lenses. So, how do we educate our patients about these various options, and, more important, how do we surgeons decide when and where each lens type should fit into our presbyopia-correcting options?
SPEAKING IN BROAD THEMES
In the process of attempting to be “full service” in our offerings, we can often confuse not only our patients but also our staff, who are, in some cases, the most essential part of the patient education process. Sometimes if our patients are given too many options, they choose the simplest one—staying in glasses or “whatever my insurance covers.”
Therefore, I find it helpful to speak in broad themes when refining lens options with patients. First, it is important to know what type of reading our patients are doing. With the advent of e-readers and tablets, many people seldom read newspaper-type printed material anymore and would prefer to have vision optimized for intermediate to meet their needs. Once a patient has expressed an interest in reducing the need for glasses, and with a brief understanding of the loss of intermediate and near vision that monfocal IOL’s optically produce, then the surgeon can home in on which technology is best for the patient.
At this point, a few concise questions can further clarify the patient’s needs and desires. First, is the patient a frequent night driver? Or, put another way, would they be willing to accept some nighttime driving disturbances (“rings around lights”) in trade for good unaided near vision? Most patients will quickly self-determine their willingness to potentially give up some quality of night driving vision with this question. If it is clear that the patient desires high-quality night driving vision due to hobby, occupation, or family circumstance, then this type of patient may benefit from a low-add multifocal or EDOF lens in contrast to a “strong” (high-add) multifocal optimized for near vision, at the expense of nighttime loss of contrast.
The two lenses I use in this situation are the ActiveFocus Restor 2.5 (Alcon) and the Symfony IOL (Abbott Medical Optics). These lenses both minimize nighttime dysphotopsias and emphasize intermediate vision over reading vision. With both lenses, patients may expect to wear low-power readers for fine print due to the reduced add power compared with other multifocal lenses. This is not a flaw in lens design but an inherent optical feature of low-add multifocal lenses, allowing preservation of high optical quality and contrast by employing less diffraction relative to high-add multifocals.
The other lens available in the low-add multifocal segment is the AMO ZKBOO, which has an add power of 2.75 D. With the Symfony and the Restor 2.5 ActiveFocus in my armamentarium, I did not feel the need to add another low-add lens for patients to choose from. Additionally, the halo and glare profile may be more prominent with the ZKBOO, as it has more diffractive steps.1
Symfony. The Symfony is particularly well suited to computer users, with a near point at 66 cm (26 inches) and a full diffractive optic, which produces a constant 47%/53% light split for distance and intermediate under all lighting conditions.2 However, this may also be the reason this lens may be associated with occasional reports of what some patients describe as spiderweb-type photic phenomena under mesopic conditions. In my experience, these disturbances are usually well tolerated due to the overall high contrast of this IOL compared with other multifocal lens platforms. Correction of chromatic aberration with this IOL is also thought to play a role in improving optical image quality and contrast.
ActiveFocus Restor 2.5. Similarly, the ActiveFocus Restor 2.5 lens defocus curve illustrates a near point at 53 cm (21 inches) optimized for intermediate tasks. However, this lens may not have as high-quality computer or near vision in low light settings, when the pupil increases in size. This may be an issue in younger patients with larger pupils. This weakness becomes a strength, however, in mesopic conditions, where the 100% distance-dominant center button and the full distance outer refractive zone of the lens produce minimal diffraction and extremely high contrast, with very few reported nighttime visual disturbances. In fact, at a 5-mm pupil size, over 80% of the incoming light rays are directed to distant foci with the ActiveFocus Restor 2.5 lens.
For patients desiring good quality night driving vision and some additional range of near focus, we have an expanded armamentarium of lens choices from which to choose. These new lenses offer excellent visual quality, with each one having its own unique strengths. In fact, with the recent approval of the ActiveFocus toric platform, and the Symfony toric, both lenses can now be safely used in a larger portion of the patient population presenting for cataract surgery.
1. Vega F, Alba-Bueno F, Millan MS, Varon C, Gil MA, Buil JA. Halo and through-focus performance of four diffractive multifocal intraocular lenses. Invest Ophthalmol Vis Sci. 2015;56(6):3967-3975.
2. Esteve-Taboada JJ, Dominguez-Vicent A, Del Aguila-Carrasco AJ, Ferrer-Blasco T, Montes-Mico R. Effect of large apertures on the optical quality of three multifocal lenses. J Refract Surg. 2015;31(10):666-676.