Meeting Patients' Visual Goals With Consistency

MICS and specially designed optics affect real-world outcomes.

Dr. Wallace: We've talked about some of the benefits of small-incision surgery, such as greater intraoperative anterior chamber control, less trauma and less inflammation. Are you seeing other benefits related to safety and/or meeting your patients' visual goals?

Dr. Malyugin: When I started doing this kind of surgery routinely, I observed an increase in the percentage of patients who achieved 20/20 vision without any kind of special preoperative measurements. That was very impressive to me. Outcomes in routine cases are just amazing.

Dr. Silverstein: With the benefits of small-incision surgery combined with the pristine optic of the Akreos lenses, my patients have a notably faster return to visual function and daily life. I've noticed this, and they've noticed this. The rapid return of visual acuity and normal lifestyle are exactly what drives everything we do in terms of our techniques and our IOLs today. With this type of surgery married to this type of optical quality, I don't have anything else that provides this more consistently.

The Benefits of an Aberration-Free Optic

Dr. Wallace: Most IOLs now have some form of an aspheric optic. How do you feel the Akreos lenses fare in this regard?

Dr. Peters: Of course, the lenses we used to implant had positive spherical aberration, and the normal cornea contains some positive spherical aberration, and the combination of the two degraded image quality for our patients. In an effort to remedy this problem, IOLs that contained negative spherical aberration were developed. Subsequently, aberration-free optics were incorporated into the Akreos lenses. As the description suggests, they are designed to add zero aberration to the visual system. The rationale is that having a small amount of residual positive spherical aberration would maintain or even enhance depth of field and contrast sensitivity. In my experience, the Akreos lenses accomplish these goals, and we have studies that confirm it as well.^12,13

The aberration-free optics make these IOLs an excellent option for monovision or blended monovision. Also, unlike lenses with negative spherical aberration, there is no downside to implanting them. When you introduce negative spherical aberration and the lens subsequently tilts or decenters, or the patient has a large angle kappa, you can potentially end up with worse vision. The aberration-free lenses do no harm, yet provide better quality of vision.

I should point out that I do use implants with positive spherical aberration in patients who have undergone hyperopic LASIK, which induces negative spherical aberration.

Dr. Weinkle: I'm very impressed with the depth of focus some patients exhibit with Akreos lenses. I have some patients who have 20/20 acuity but have residual refractive error of approximately −0.5D, and they can use a computer without eyeglasses comfortably. That is a really a nice feature because the depth of focus does allow them 20/20 vision even when I don't hit the refractive target dead on.

In addition, because these IOLs have uniform power across the entire lens surface, if some decentration occurs, the power will still be consistent. For example, it happens rarely, but sometimes after completing phaco and irrigation/aspiration I may see a tear in the capsulorhexis. I have placed the Akreos MICS lens in patients like this, and the lenses have centered very well. Even if they decenter slightly, I expect a stable refraction.

Dr. Malyugin: The uniform power across the lens is very forgiving of our sometimes imperfect IOL alignment. Eyes are not perfectly shaped. The pupil is slightly decentered, and the optical axis does not necessarily correspond with the apex of the cornea. Because of this, in many cases we see that we're not perfectly aligning the IOL. The optic design of the Akreos lenses renders this an insignificant issue.

Dr. Silverstein: I envision a time in the future when we'll be able to customize many features of an IOL for a given patient or a given eye. Preoperative measurements will dictate whether we use a positively or negatively aberrated spherical IOL or an aspheric IOL. Until that day arrives, the technology that benefits our patients the most is an optically well-tolerated aspheric platform that doesn't introduce additional problems with higher-order aberrations, and in cases where the eye has inherent positive corneal spherical aberration, enhances depth of field. In other words, until we can order up patient-specific IOL sphericity, toricity and perhaps even size, we're best served by utilizing a single aspheric platform that provides benefits to the largest number of patients, regardless of each eye's optical characteristics.

Dr. Peters: Speaking of higher-order aberrations, as we discussed previously, we know that smaller incisions induce less astigmatism, i.e., less second-order aberrations. When we transitioned from 2.8-mm to 2.2-mm to 1.8-mm incisions in our practice, we tested patients before and after surgery to detect changes in corneal higher-order aberrations with the various incision sizes. With a 2.8-mm incision we had a statistically significant induction of horizontal and vertical coma, trefoil and astigmatism oriented in the axis of the incision, as we would expect. When we went down to 1.8 mm, we didn't experience any statistically significant induction of higher-order aberrations.

It's difficult in a cataract population to measure best-corrected visual acuity (BCVA) outcomes and use that as an indicator of how well a lens performs because there are so many other potential factors affecting BCVA. However, we know we did not alter higher-order aberrations with 1.8-mm incisions but we did with 2.8-mm incisions, and that can only contribute in a positive manner to improving BCVA.

Looking Toward the Future

Dr. Wallace: What do you see coming through the pipeline in the area of MICS lenses? Do you have any ideas for future improvements?

Dr. Weinkle: I would be excited to be able to use an Akreos MICS lens that has astigmatism correction. This type of modification would be ideal, especially because the lens remains positioned in the capsular bag so well by virtue of its good capsular contact. It does not rotate; it stays in place.

Dr. Malyugin: It is possible to remove the lens through an incision barely larger than 1.0 mm, but we are restricted by our implants. A limitation I see is in the biomaterials currently used for IOLs, having index of refraction within certain limits. That means they have to be thick enough to have a good optic. I believe we will come to a point when we will be able to split the lens and inject two optics separately, combining them right inside the eye. If we want our incisions to be smaller than 1.8 mm, this may be the next step we have to take.

Dr. Wallace: I often think about how around 25 years ago, phaco was not mainstream. Extracapsular surgery was being performed and it was not unusual to have incisions as large as 9 or 10 mm for removing the nucleus. That was certainly much better than intracapsular cataract surgery, but still a relatively lackluster worldwide standard. So many naysayers were talking about how unimportant phaco was, but the introduction of foldable lenses certainly changed the picture. Everyone moved toward phacoemulsification.

In our time, we have witnessed an incredible evolution and important improvements for our patients, so it is difficult to imagine what will happen with cataract surgery 25 years from now. I suspect it will be amazing.

We have learned a lot through our group discussion, and I hope we have been able to give our surgeon colleagues some ideas on how to incorporate MICS into their practices and why it is definitely worth considering. ■

Supplement References

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2. Mullner-Eidenbock A, Amon M, Schauersberger J, et al. Cellular reaction on the anterior surface of 4 types of intraocular lenses. J Cataract Refract Surg 2001; 27:734-740.
3. Abela-Formanek C, Amon M, Schild G, et al. Uveal and capsular biocompatibility of hydrophilic acrylic, hydrophobic acrylic, and silicone intraocular lenses. J Cataract Refract Surg 2002; 28:50-61.
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6. Amzallag T. Akreos Micro-Incision IOL: final results of a pilot clinical study at one year follow up. Free Paper presented at ESCRS Congress, London, England, September 2006.
7. Ernest PH, Lavery KT, Kiessling LA. Relative strength of scleral corneal and clear corneal incisions constructed in cadaver eyes. J Cataract Refract Surg 1994;20:626-629.
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9. Wilczynski M, Supady E, Piotr L, Snyder A, Palenga-Pydyn D, Omulecki W. Comparison of surgically induced astigmatism after coaxial phacoemulsification through 1.8 mm microincision and bimanual phacoemulsification through 1.7 mm microincision. J Cataract Refract Surg 2009;35:1563-1569.
10. Dick HB. Bi-axial microincision versus co-axial small incision using the Stellaris Vision Enhancement system. Paper presented at the Annual Congress of the ESCRS, Barcelona, 2009.
11. Wallace RB 3rd. Capsulotomy diameter mark. J Cataract Refract Surg 2003;29(10):1866-68.
12. Santhiago MR, Netto MV, Barreto J Jr, et al. Wavefront analysis, contrast sensitivity, and depth of focus after cataract surgery with aspherical intraocular lens implantation. Am J Ophthalmol 2010;149(3):383-389.
13. Shentu X, Tang X, Yao K. Spherical aberration, visual performance and pseudoaccommodation of eyes implanted with different aspheric intraocular lens. Clin Experiment Ophthalmol 2008;36(7):620-624.