Roundtable: Creating a New Standard for Cataract Surgery

Ocular Surgery News: What makes for an optimal phaco procedure?

Y. Ralph Chu, MD: The goal of an optimal phaco procedure is to give the patient excellent visual outcomes, corneal clarity, and optimal endothelial and ocular health after the procedure.

Douglas Grayson, MD: An optimal phaco procedure is one that is completed with maximum efficiency and minimal trauma to the eye and results in the best possible technical outcome.

Mark Packer, MD: Achieving vision of 20/40 or better with a clear cornea has become the standard when assessing eyes on postoperative day 1. This can be achieved using the latest lens- removal technology that features responsive fluidics, precise modulation of ultrasound power, and efficient cutting through transversal movement of the phaco tip. I prefer lens-removal technology that produces improved results without requiring me to change technique.

OSN: How has the incorporation of latest-generation technologies affected your practice?

Chu: Innovative technologies are driving the conversion of cataract surgery to refractive surgery in which patients expect excellent visual outcomes, not only in Snellen visual acuity, but also in improved contrast sensitivity. Using a combination of technologies, surgeons can now remove the cataract safely and efficiently while keeping the eye quiet and can implant an IOL that helps to achieve patients’ desired visual outcomes.

Patient selection

OSN: Discuss the range of patients who can be treated with the latest-generation phaco systems.

Chu: I think the technological advancements in phaco systems have allowed surgeons to treat a wider variety of patients because the fluidics and the delivery of ultrasound energy are controlled. For example, when using older fluidics technology, it was difficult to prevent significant iris damage in patients with floppy iris syndrome. New phaco machines feature improved fluidic control, and now surgeons can complete cataract removal on a patient with floppy iris syndrome without any significant surgical maneuvers because the chamber environment is stable. At my practice, the WhiteStar Signature System (Advanced Medical Optics, Inc., [AMO]) has a low flow setting, which allows for the removal of cataracts with minimal disruption to the iris and minimal turbulence in the eye.

Comparing current phaco systems

OSN: Please compare and contrast different phaco platforms you have used.

Chu: Dual-pump technology and the ability to control the duty cycle of the ultrasound power allow surgeons more flexibility in the methods used to remove a cataract. Different densities of cataract can be removed more efficiently and safely using latest-generation phaco machines than with previous systems. New phaco machine technology was developed to help surgeons achieve quieter eyes, clearer corneas, and improved patient outcomes. I have experience using all of the platforms including the WhiteStar Signature System, the Infiniti Vision System (Alcon Laboratories, Inc.), and the Stellaris system (Bausch & Lomb). I currently prefer the WhiteStar Signature System because I think the fluidic control with chamber stability and the dual-pump system work well for my technique.

Packer: Surgeons’ selection of a phaco machine depends largely on individual technique and comfort levels with different technologies. In my experience, the WhiteStar Signature system with Fusion Fluidics and Ellips transversal ultrasound technology achieves a stable chamber because the fluidics technology steps down vacuum during occlusion to avoid surge (Figure 1). In addition, the variable WhiteStar ultrasound technology increases energy when the foot pedal is depressed, allowing surgeons to approach moderate or soft cataracts safely.

Grayson: The Millennium (Bausch & Lomb) is a venturi system, the Infiniti is a peristaltic system, and the WhiteStar Signature System has both a venturi pump and a peristaltic pump. Venturi pumps respond quickly with fast vacuum rise and release times, which increases efficiency but can also increase intraoperative complications at a higher rate. I think more surgeons prefer peristaltic systems over venturi systems. Latest-generation peristaltic pumps simulate venturi systems and I prefer the WhiteStar Signature System’s dual-pump system over others. With the WhiteStar Signature System, a venturi irrigation and aspiration (I&A) mode is available for efficient cortical aspiration.

Cutting ability and thermal dissipation are also important aspects of a phaco machine. WhiteStar technology, or the use of micropulse energy, has been the most important advance in decreasing the amount of phaco energy used during surgery. Reducing phaco energy decreases endothelial trauma and corneal thermal wound injury. Manufacturers of the OZil Torsional technology (Alcon Laboratories, Inc.) on the Infiniti System claim that it uses less phaco energy. However, when breaking up dense cataracts, traditional phaco energy is used and heat dissipation seems to be better on the Signature System than on the Infiniti System.

The third aspect of a phaco machine is chamber stability, which is maintained by computer-controlled fluidics. The Fusion Fluidics technology on the WhiteStar Signature system provides for a stable chamber, and in some ways it is better than the venturi on the Millennium. The Infiniti ranks in between the Millennium and the Signature in terms of chamber stability.

Having a dual-pump system with a combination of venturi and peristaltic pumps has been useful in all of my cases. —Y. Ralph Chu, MD

OSN: What are the advantages of venturi and peristaltic pumps? For which cataracts is each beneficial?

Chu: Having a dual-pump system with a combination of venturi and peristaltic pumps has been useful in all of my cases. The peristaltic pump provides optimal control of nuclear material and can reach high vacuum levels quickly and efficiently. On the other hand, venturi pumps work well when removing cortex and viscoelastic during surgery. Cortical cleanup is essential in delivering optimal visual outcomes in patients who receive a premium IOL because all premium IOLs are sensitive to small degrees of PCO.

Modulating ultrasound energy

OSN: How does transversal phaco compare with traditional longitudinal phaco?

Chu: Transversal ultrasound can be used to remove soft and moderate nuclei with less thermal buildup than a straight ultrasound technique. The combination of a variable duty cycle, such as WhiteStar technology, and transversal ultrasound provides surgeons with an efficient way to remove dense nuclei with minimal thermal damage and less ultrasound energy in the eye, resulting in quieter eyes on day 1.

Grayson: Currently, Alcon’s OZil Torsional system can be programmed to alternate between torsional and longitudinal phaco. AMO has introduced the Ellips system, which intermixes transversal and longitudinal on every stroke, creating an elliptical pattern for the phaco probe going through the nucleus. The advantage to this is that surgeons do not have to use an angled phaco tip. The OZil system, on the other hand, is designed to work primarily with an angled phaco tip. With the Ellips, surgeons can use a straight tip, allowing more maneuvering flexibility within the capsular bag while creating the same effect as the OZil system.

Rising patient expectations

OSN: Have patient expectations changed, and how do new phaco technologies address these expectations?

Patients are having surgery earlier, even before developing cataracts, when they still have good corrected vision with glasses. —Mark Packer, MD, FACS

Packer: Patients are having surgery earlier, even before developing cataracts, when they still have good corrected vision with glasses. If they have early cataracts, they may have 20/20 vision, but also night vision, glare, or contrast problems, but in general, their demands will be very high. They may have 20/20 vision but are looking for increased contrast and clarity or freedom from wearing glasses. The goal for these surgeries is a stable chamber with no fluctuation, gentle technique, and the ability to completely clean the capsule and eliminate induced astigmatism with minimal trauma to the eye. The new generation of machines has addressed these changes by improving the fluidics. For example, the WhiteStar Signature system with Fusion Fluidics and Ellips transversal ultrasound technology allows for effective removal of the cataract through either two 1.4-mm microbiaxial incisions or a 2.2- to 2.4-mm microcoaxial incision.

Chu: Removing cataracts has become safer, and surgeons can improve their technique as they become more efficient without compromising safety. This leads to quieter eyes, good vision, and increased comfort after surgery. My patients experienced a “wow” factor in their vision during the FDA study¹ with the Tecnis 1-piece IOL. These patients had improved vision after receiving this monofocal IOL compared with the control group.

IOL selection

OSN: Which IOL do you currently use? Why?

Packer: For patients who do not mind wearing reading glasses, I suggest an aspheric IOL to maximize their image quality by matching the specific aspheric implant to the individual eye. The aberration- reducing technology in an aspheric IOL, such as the Tecnis 1-piece IOL (AMO), is an improvement over previous one-piece IOLs. As an additional service to my patients, I use corneal topography to measure the corneal spherical aberration and then select an aspheric IOL that most closely matches, resulting in a net zero total postoperative spherical aberration. I select the Tecnis 1-piece IOL for about two-thirds of my patients because it compensates for the population average spherical aberration. Approximately one-third of my patients receive the AcrySof IQ IOL (Alcon Laboratories, Inc.), and a small number receive the SofPort AO IOL (Bausch & Lomb). I use toric IOLs sparingly because I often perform limbal-relaxing incisions.

The aspheric design of the Tecnis maximizes potential acuity at night and at distances. —Douglas K. Grayson, MD, FACS

Mester: The majority of the 4,000 patients yearly who undergo phaco procedures in my ophthalmology department receive an aspheric IOL, such as the Tecnis 1-piece IOL or the AcrySof IQ IOL. I transitioned to aspheric IOLs with the introduction of the Tecnis. Personal investigations and results of many other studies confirmed the superiority of this design, particularly in terms of contrast sensitivity.² I use aberration-correcting IOLs because they provide optimal compensation of spherical aberration. IOLs without negative spherical aberration should be used only in eyes with extremely low corneal spherical aberration.

Grayson: I am currently using the Tecnis 1-piece IOL because I think the acrylic material is superior to that used in the AcrySof acrylic IOL. The material in the Tecnis stays clear. The aspheric design of the Tecnis maximizes potential acuity at night and at distances. I have been implanting Tecnis IOLs for 4 years, and I have not experienced any issues associated with late decentration.

Improving visual quality

OSN: What role does spherical aberration play in visual quality? How can spherical aberration be corrected?

Chu: During the natural aging process, a person’s lens changes over time and spherical aberration increases. Spherical aberration can be reduced at the time of surgery by implanting an IOL that counterbalances the spherical aberration of the cornea. By reducing spherical aberration to nearly zero, patients will see an improvement in the quality of vision, which is not only reading 20/20 vision, but also the ability to see in low-light conditions, at night, and in the fog (Figure 2).^3-5 Reducing spherical aberration improves contrast sensitivity, which is an important factor in functional vision.

The FDA clinical trials on the Tecnis showed that reducing the spherical aberration can result in an improvement in functional visual acuity in low-light conditions. ^5,6 In fact, reducing spherical aberration of the optical system to zero can improve night vision and break-reaction time in patients who received an IOL, which is critical because it translates to increased safety while driving.

Evolution of one-piece IOLs

OSN: Compare and contrast different one-piece IOLs. How have they evolved?

Mester: The Tecnis 1-piece and the AcrySof IQ are made with a hydrophobic acrylic material. They both have sharp-edged optics and a spherical aberration- correcting design. The AcrySof IQ has a textured edge, whereas the Tecnis 1-piece has a frosted optic edge to avoid edge glare, a three-point fixation in the capsular bag, and polished haptics. The AcrySof IQ has a blue-light filter, whereas the Tecnis does not. Both one-piece IOLs perform well, are easy to implant, have excellent centration, and result in low PCO rates.

Packer: IOL optic technology and one-piece platform designs have continued to improve. Advancements in aspheric optics first led to the development of the three-piece Tecnis IOL. The AcrySof IQ IOL was developed soon after. The AcrySof IQ does not correct for as many aberrations as the Tecnis, but it was considered easier to use because of its one-piece design.⁷ Now, the Tecnis optic technology is available in an easy-to-use one-piece platform that includes design enhancements such as the Tri-Fix three-point fixation and the Pro-Tec 360° edge design. Both of these one-piece IOL platforms can be placed in the eye through a 2.2-mm incision. However, in my experience, the Tecnis 1-piece corrects for more aberrations and appears to unfold faster than the AcrySof IQ.

Chu: A concern about previous generations of one-piece IOLs was whether they could remain stable in the capsular bag for predictable stable refractions and whether they could minimize PCO. I think the new generation of one-piece IOLs address those concerns. Until now, one-piece IOLs had no effective feature to prevent PCO at the haptic/optic junction. With the new generation of one-piece IOLs, the posterior barrier extends across the haptic/optic junction to create a 360· square edge posteriorly to minimize PCO. The Tecnis 1-piece IOL has a new edge designed to minimize dysphotopsias and aberration after surgery.

OSN: Which patients are good candidates for a one-piece IOL?

Packer: The introduction of the one-piece IOL has greatly changed my practice. While three-piece IOLs still have a role, they have been relegated to sulcus fixation or suture fixation, which occurs in only 1% to 2% of cases in which there is a tear in the posterior capsule. When I have an intact capsule, I can use the Tecnis 1-piece IOL with confidence.

Grayson: A patient receiving a one-piece IOL should have an intact symmetrical capsulorrhexis and no compromised zonules. Three-piece IOLs tend to be stiffer and can be placed in the sulcus or in the capsular bag in an area of zonule dehiscence because it will be more stable. Three-piece IOLs are better for patients with pseudoexfoliation and zonule elasticity because the IOL can give the capsular bag more stability.

OSN: Have you seen any change in posterior capsular opacification (PCO) rates? If so, have any technologies played a part in that change? How do you think the combination of efficient lens extraction, cortical clean up, and an IOL that prevents cell migration impact your PCO rates?

Mester: PCO rates have decreased over the past several years. The key factor in PCO prevention is a truncated IOL optic edge (Figure 3). One clinical investigation has proven that a sharp optic edge is more important than the IOL material in the prevention of PCO.^8,9 The latest generation of IOLs has a sharp edge around the entire optic, avoiding weak points at the haptics. The Tecnis 1-piece IOL has a three-point fixation design with anterior placement of the haptic to improve the contact between the posterior surface of the optic and the capsular bag.

Packer: PCO rates are higher in eyes implanted with the AcrySof IQ IOL because epithelial cells can grow across the posterior haptic/optic junction.¹⁰ It takes approximately 2 to 5 years for PCO to develop. This may be less of an issue with the new-generation one-piece IOLs because the square edge is consistent across the haptic/optic junction. For example, the Tecnis 1-piece IOL includes the Pro-Tec 360· edge design, which includes an uninterrupted 360° square-edge designed to prevent less epithelial cell migration onto the optic.

References

1. Chu YR. Visual Acuity Results with the Tecnis 1-piece IOL. Paper presented at: European Society of Cataract and Refractive Surgery Annual Meeting; September 2008; Berlin, Germany.
2. Mester U, Dillinger P, Anterist N. Impact of a modified optic design on visual function: clinical comparative study. J Cataract Refract Surg. 2003;29(4):652-660.
3. Holladay JT, Piers PA, Koranyi G, van der Mooren M, Norrby NE. A new intraocular lens design to reduce spherical aberration of pseudophakic eyes. J Refract Surg. 2002;18(6):683-691.
4. Piers PA, Manzanera S, Prieto PM, Gorceix N, Artal P. Use of adaptive optics to determine the optimal ocular spherical aberration. J Cataract Refract Surg. 2007;33(10):1721-1726.
5. Packer M, Fine IH, Hoffman RS, Piers PA. Improved functional vision with a modified prolate intraocular lens. J Cataract Refract Surg. 2004;30(5):986-992.
6. TECNIS 1-piece Foldable Posterior Chamber Intraocular Lens [package insert]. Advanced Medical Optics, Inc.
7. IOL Design: Nixon D. Updating the One-Piece Lens Design. Paper presented at: ASCRS Annual Meeting 2008; April 2008; EyeWorld Corporate Mornings; Chicago, IL.
8. Mester U, Fabian E, Gerl R, et al. Posterior capsule opacification after implantation of CeeOn Edge 911A, PhacoFlex SI-40NB, and AcrySof MA60BM lenses: one-year results of an intraindividual comparison multicenter study. J Cataract Refract Surg. 2004;30(5):978-985.
9. Kohnen T, Fabian E, Gerl R, et al. Optic edge design as long-term factor for posterior capsular opacification rates. Ophthalmology. 2008;115(8):1308-1314, 1314.
10. Dewey S. Posterior capsule opacification. Curr Opin Ophthalmol. 2006;17(1):45-53.