Symposium: Maximizing Patient Outcomes with Advanced IOL Design

Critical elements; IOL success

Richard L. Lindstrom, MD: What are the critical elements that determine IOL success?

David J. Apple, MD: The most important element of a successful IOL is the lens design. The IOL must fit properly so that it is stable in the long term, with minimal potential for decentration in order for the patient to benefit. Stability was of minor importance 20 years ago but is now critical with the advent of modern specialized IOLs such as aspheric, phakic, multifocal, refractive, and telescopic IOLs.

Additionally, IOL design is a key factor in inhibiting posterior capsular opacification. PCO and proliferation of retained or rejuvenated lens epithelial cells can inhibit the positive function of modern IOLs.

Louis D. “Skip” Nichamin, MD: Optical design is important because clinicians want to provide patients with the best visual quality in terms of outcomes. Ophthalmologists are faced with an interesting dilemma with the rise in use of multifocal IOLs, since these lens designs may decrease distance vision quality and contrast sensitivity, a compromise ophthalmologists must consider when selecting an IOL.^1,2 Another important element of an IOL is the delivery system used to implant it.

Optical design is important because clinicians want to provide patients with the best visual quality in terms of outcomes. —Louis D. “Skip” Nichamin, MD

Lindstrom: Optical performance is critical. If the IOL does not provide the patient with a satisfactory optical outcome, then the IOL fails from the start. Next, I am influenced by the ease of insertion, including ease of loading the inserter, ease of inserting the IOL into the eye, and the size of the incision. Other factors that influence my decision include how the IOL centers in the capsular bag and the biocompatibility of the IOL.

Are there any criteria that were important in the past that are less important today?

Apple: Although it is still an important issue, biocompatibility is not as important today as in years past. Today, most of the materials comprising IOLs are compatible.

Nichamin: An IOL’s biomaterial is becoming less of a consideration because most modern biomaterials are equally compatible. Although rare, patients who have significant vitreoretinal pathology may benefit more from an acrylic material.³

Lindstrom: Choosing the correct IOL to meet a patient’s goals is imperative in IOL implantation. Advances in IOL design have given ophthalmologists multiple IOL choices. It is important to discuss visual goals with a patient before surgery, review the patient’s clinical history, and then choose an IOL accordingly.

What are your criteria for selecting an IOL?

Apple: I believe the top criterion when selecting an IOL for a patient is safety, which implies an IOL designed and manufactured for a proper fit. The three most important factors in IOL selection are biocompatibility, fit, and quality of the surgery.

Uday Devgan, MD, FACS: My first criterion when selecting an IOL is that it must provide good optical performance, because optical performance is the primary reason for the procedure. The selected IOL will determine the patient’s final results. Even if a surgeon performs a perfect cataract extraction, the patient’s visual quality is determined by the implanted IOL. The right IOL power, the right positioning of the IOL, and the right optic are all needed for successful cataract surgery. In addition, the IOL should be made of a material that is biocompatible, have a low instance of PCO, and, if possible, be implanted using the smallest incision possible.

It is critical that the ophthalmologist uses the correct IOL for each patient to find the perfect fit and limit postoperative complications. —David J. Apple, MD

Nichamin: Ophthalmologists should attempt to tailor the IOL to the individual patient based upon anatomy, ophthalmic factors, systemic conditions, and visual goals. There is no one ideal implant for all patients.

David R. Chow, MD, FRCSC: A recent issue is difficulty visualizing the peripheral retina in patients who have a diffractive or multifocal IOL, which is the main concern for retina surgeons.

Apple: An ophthalmologist could choose a generic IOL and implant it in any patient, but that practice may lead to problems. Some IOLs are not suitable for patients with ongoing inflammation, whereas others produce complications with PCO. It is critical that the ophthalmologist uses the correct IOL for each patient to find the perfect fit and limit postoperative complications.

Application of aspheric optics

Lindstrom: Three types of IOL designs that are commercially available are spherical, negative aspheric, and aberration-free aspheric IOLs. What are the differences between these designs?

Devgan: Traditional IOLs have positive spherical aberration, which means the curvature of the IOL is identical throughout. The optical power, however, is different at various points of the IOL. Spherical IOLs defocus peripheral light rays as compared with central light rays, resulting in a decrease in image quality because light rays are not focusing on the same point (Figure 1).

Zero aberration aspheric IOLs focus all light points, from the peripheral to the center, to the same point. The quality of the image is increased, and there is no distortion of the image, even if the IOL is decentered or tilts and regardless of pupil size.

Spherical vs. Aspheric Figure 1. Spherical IOLs defocus peripheral light rays, while aspheric IOLs equally focus all light rays. Source: Devgan U

Thierry Amzallag, MD: Spherical IOLs also create positive spherical aberration, which results in loss of contrast sensitivity. Agarwal and colleagues have shown that pseudophakic patients with spherical IOLs experience more spherical aberration and less contrast sensitivity than phakic patients of the same age (Figure 2).⁴

Negative aspheric IOLs are designed to reduce positive spherical aberration and, therefore, improve contrast sensitivity (Figure 3). These negative aspheric IOLs are designed to offset the positive spherical aberration of a typical cornea. However, some residual positive spherical aberration from the cornea has been shown to enhance depth of field, which is why IOLs that are aberration-neutral may produce better vision.

Spherical Aberration with Age Figure 2. Spherical aberration of the natural lens increases with age. Standard IOLs cause a dramatic change in spherical aberration. Source: Devgan U

Nichamin: Spherical aberration is arguably the most significant higher-order aberration that ophthalmologists face. Traditional IOL implants with a positive spherical aberration impart additional positive spherical aberration to a patient’s optical system because the cornea has a positive spherical aberration innately. I believe this is one of the reasons ophthalmologists encounter patients who have good surgical outcomes and excellent Snellen acuities but are unhappy with their quality of vision.

Aspheric IOL options include two IOLs that incorporate negative asphericity: the Tecnis (Advanced Medical Optics [AMO]), with -0.27 µm of spherical aberration, and the AcrySof IQ (Alcon), with -0.20 µm of spherical aberration. The negative asphericity design of the IOLs assumes all corneas have some amount of spherical aberration.

A third option is the aspherically neutral IOL design, incorporated into both the SofPort AO and the Akreos Adapt AO (Bausch & Lomb) IOLs. These IOL designs impart neither positive nor negative spherical aberration. Any IOL with either positive or negative spherical aberration may induce additional higher-order aberrations if the IOL decenters or is not aligned exactly with the visual axis. The SofPort AO and Akreos Adapt AO, with zero aberration, might fit the largest population of patients because the IOLs are not affected by decentration or tilt.⁵

Aberration-free IOLs improve the quality of an image that the retina receives and transmits to the brain. —Richard L. Lindstrom, MD

Lindstrom: Spherical aberration occurs when the power of the refracting curvature of the lens changes along the edge. As the power changes, light is not focused to a single point causing visual aberrations, most often seen as halos around lights.

Although spherical aberration reduces the quality of the image generated by a patient’s optical system, aspheric IOLs can be implanted to minimize or neutralize the spherical aberration in the eye. The aspheric IOL focuses all light rays to the same point, giving the patient increased visual quality and no distortion of the image, even if the IOL tilts or decenters.

Can you explain the differences between attempting to correct for an average aspheric lens and one that is aberration-free?

Nichamin: A substantial portion of the general population does not have an average amount of inherent positive corneal spherical aberration. When creating aspheric IOLs, designers had to decide how much negative spherical aberration and how much negative asphericity to incorporate, which is a challenging balance. Regardless of the decision, a number of patients will fall out of the curve, whereas an aberration neutral lens would not have that issue.

Spherical vs. Aspheric Figure 3. Comparison of photographs taken through a 22.0 D Aspheric IOL and a 22.0 D traditional IOL. The pupil size of the camera was 5 mm. Source: Devgan U

Devgan: Virtually any characteristic can be measured on a bell curve, from height to corneal curvature to amount of corneal spherical aberration. If you correct the average amount of spherical aberration for the average cornea, then that would correct the mean ±1 standard deviation of the population. What happens to the patients who fall out of that standard deviation? The patients who are not average will not be fully treated or will be over-treated by the IOL.

If you implant an IOL that has zero spherical aberration, the amount of the patient’s spherical aberration does not matter. The patient’s preoperative corneal spherical aberration is not going to change. The same cornea the patient has been used to looking through his or her entire life is going to have the same amount of spherical aberration after surgery.

Lindstrom: Aberration-free IOLs improve the quality of an image that the retina receives and transmits to the brain. Decentration or tilt that may occur postoperatively will not negatively affect patient outcomes. How important is this for ophthalmologists and patients?

Devgan: Measurements of corneal spherical aberration are not taken before cataract surgery, and I believe most practices do not have the equipment to test corneal spherical aberration. Ophthalmologists need to implant an IOL that will increase visual performance without spherical aberration. The IOL should be appropriate for all patients. Aberration-free IOLs are appropriate for all patients, regardless of whether an ophthalmologist has not measured preoperative corneal spherical aberration.

Amzallag: Visual acuity, quality of vision in different light conditions, and comfort are important considerations for patients. An aberration-free IOL will offer good high- and low-contrast visual acuity, good photopic and mesopic contrast sensitivity and, combined with some residual corneal spherical aberration, may actually enhance depth of field. These factors will allow for comfort in most activities of daily living.

Figure 4. IOLs are classified in three categories. Figure 5. Current IOLs available in the United States are classified by three categories according to their level of spherical aberration. Source: Devgan U

Aspheric IOLs improve vision by reducing positive spherical aberration, which potentially provides patients with improved contrast sensitivity in mesopic and photopic conditions. Aspheric IOLs also provide better quality of vision, particularly in dim light conditions. In individual patients, however, pre-existing corneal spherical aberration and other high-order aberrations should be considered before selecting an aspheric IOL, particularly if the IOL is designed to introduce more spherical aberration or negative aberration in the patient’s eye (Figures 4, 5).

Aspheric optics; patient population

Lindstrom: How do you choose the appropriate IOL for each patient, and which patients are the best candidates for aspheric IOL implantation?

Amzallag: Most patients should benefit from aspheric lens implantation. Ophthalmologists have the ability to choose which type of aspheric lens is best for each patient, depending on pre-existing spherical aberration and total high-order aberrations. An aspheric, aberration-neutral IOL can be used in all patients because it does not interfere with a patient’s visual system. The aberration-neutral IOL can be used in patients who have undergone refractive surgery or who have capsular or zonular weaknesses, because this IOL has consistent power across the entire optic surface. Using an aspheric lens with negative spherical aberration requires knowing the amount of negative spherical aberration induced by the lens and subsequently selecting patients accordingly. It is crucial to avoid leaving a patient’s eye with negative spherical aberration.

Lindstrom: Although testing beyond Snellen acuity would provide ophthalmologists with a better understanding of the most appropriate IOL to implant in a patient, it would be unrealistic to perform contrast sensitivity tests at different frequencies on every patient. Which type of IOL provides the best quality of vision for the general population?

Devgan: Surgeons should talk to patients, find out their visual goals, and inform them that their vision will not return to the way it was during their twenties. Getting patients in the correct mindset helps to set realistic expectations. Patients with cataracts often have IOLs with positive spherical aberration. Implanting an IOL with zero spherical aberration, correcting a refractive error, and having a lens that is aberration free almost guarantees that a patient will have better visual function postoperatively than preoperatively.

Akreos Adapt AO IOL

Lindstrom: How is the Akreos Adapt AO IOL different from standard IOLs?

Amzallag: The Akreos Adapt AO IOL has square edges and a continuous 360º posterior barrier to prevent PCO. It has an aberration-free aspheric optic with a low refractive index offering optimal quality of vision. The IOL has four haptics and features three overall diameters that vary with the range of diopters for consistent stability in the myopic, emmetropic, and hyperopic capsular bags. The Akreos material is homogeneous, and the uniform nature of the co-polymer is free of microvacuoles and “glistenings” that are typically found in other acrylic lenses.

Nichamin: As an investigator in the current Akreos Adapt IOL U.S. clinical trials required by the FDA, my experience has shown that the design appears to provide superb centration and long-term stability within the capsular bag. The IOL has a moderate index of refraction, lower than hydrophobic acrylic IOLs, which, as we have noted, may decrease postoperative dysphotopsia.

Lindstrom: Describe the design of the Akreos Adapt AO IOL.

An aspheric, aberration-neutral IOL can be used in all patients because it does not interfere with a patient’s visual system. —Thierry Amzallag, MD

Amzallag: The Akreos Adapt AO model has a 6-mm biconvex optic with two aspheric surfaces and a steeper anterior surface. This optic profile, combined with the low refractive index acrylic material, minimizes lens-induced, postoperative dysphotopsia. The optic is aberration-neutral and offers consistent power from center to edge and therefore is suitable for all cataract patients, regardless of corneal shape, pupil size, or pupil or capsular bag centration.

The four haptics offer a superior angle of contact in the capsular bag, and each haptic absorbs forces of various intensities that are exerted under capsular bag contraction.

Apple: The Akreos Adapt AO has a 360º continuous square-edge barrier on the anterior and posterior sides of the IOL. I find that the aberration-free optic design is excellent and is a good stage design for other IOL platforms. Although most American ophthalmologists are familiar with the C-loop design, they will note the capabilities of the four closed loop haptics once the IOL is approved in the American market.

Lindstrom: What is the delivery method of the Akreos Adapt AO IOL, and is it user friendly?

Amzallag: The Akreos Adapt AO IOL is designed for implantation with the AI-28 single-use injector (Bausch & Lomb) (Figure 6) that requires a 2.8-mm clear corneal incision. The AI-28 injector is user friendly.

First, IOL loading is simple. The loading deck is wide and the IOL is loaded flat. The IOL unfolds smoothly, and the two leading haptics unfold directly in the capsular bag. Surgeons need to gently pump the plunger to free the trailing haptics and, using the plunger tip, place the trailing haptics in the capsular bag in one step. If the IOL is not fully implanted, than the trailing haptics can be placed by gently pushing the IOL downward using a non-toothed instrument. The hydrophilic, acrylic material is soft and will glide easily under the capsulorrhexis. The IOL centers immediately in the capsular bag; surgeons do not need to rotate the IOL to secure its position.

Ease of insertion Figure 6. The AI-28 singe-use injector (Bausch & Lomb). Source: Bausch & Lomb

Hydrophilic vs. Hydrophobic IOLs

Lindstrom: Are there any advantages to hydrophilic acrylic IOLs compared with hydrophobic IOLs?

Amzallag: Hydrophilic acrylic IOLs have been used in Europe for more than 10 years. European ophthalmologists have a thorough understanding coupled with many years of experience using hydrophilic material, which is highly biocompatible and subtle in the eye. Hydrophilic materials are less susceptible to biocontamination than are hydrophobic materials and have low propensity for inflammatory cell attachment, according to studies by Schild and colleagues, and by Ursell and colleagues.^6,7

Other advantages of hydrophilic material include its durability and flexibility. The material can be folded and compressed easily without damage and without fold marks sometimes observed with hydrophobic materials.

Apple: Another advantage of hydrophilic IOLs, and one that is critical to retinal surgeons, is that silicone oil does not adhere to the hydrophilic material, which is important for patients with present or potential retinal disease, diabetes, trauma, or any condition that would cause retinopathy. When used with silicone IOLs, silicone oil adheres to the IOL, and it becomes opaque, necessitating removal of the IOL. Hydrophilic IOLs have approximately 5% adherence to silicone oil.⁸

Another advantage of hydrophilic IOLs, and one that is critical to retinal surgeons, is that silicone oil does not adhere to the hydrophilic material. —David J. Apple, MD

Lindstrom: How does the water content of hydrophilic IOLs affect glare, external and internal reflections, and other unwanted visual phenomena compared with hydrophobic IOLs?

Nichamin: The index of refraction of some of the hydrophilic acrylics is lower than the index of refraction of the hydrophobic acrylics. Optical engineers have stated that the higher index of refraction of hydrophobic acrylic may lead to higher levels of dysphotopsia, such as internal and external reflections causing glare, halo and unwanted images.

Amzallag: A recent study conducted by Shambhu and colleagues compared the Akreos Adapt AO and Acrysof IOLs in 157 patients. The study found severe glare symptoms in 13% of the patients for the AcrySof IOLs compared with 4.6% of the hydrophilic Akreos IOLs. Absence of glare was reported by 28% of the Akreos patients and by 18% of the Acrysof patients.⁹

Evolution of IOL design improves patient outcomes Joel Pynson, MD Over the past few decades, IOL materials, shapes, and sizes have evolved significantly, affecting outcomes such as IOL stability and posterior capsular opacification. In fact, pioneers such as Barrett, who developed the Iogel IOL (Alcon) in the 1980s, and Galand, who has worked extensively with IOL designs using hydrophilic acrylic material, taught ophthalmologists that IOL stability in the capsular bag is of utmost importance.1-4 Pioneers such as Barrett and Galand taught ophthalmologists that IOL stability in the capsular bag is of utmost importance. —Joel Pynson, MD Surgical techniques for implanting IOLs also evolved. Today’s techniques are different from those used in the late 1990s, when acrylic material was first developed for IOLs, and in the late 1980s. The most significant change is the capsular opening technique. In the past, the opening was simple to make by using a needle to open the anterior capsule. The technique was not perfect, though, and a significant amount of lens decentration would result. In the early 1980s, however, two surgeons, Gimbel and Neuhann, developed capsulorrhexis, a procedure in which a circular opening in the anterior capsule is made.5 Capsulorrhexis was a revolution in cataract surgery. Before, surgeons were unsure if IOLs placed in the capsular bag would remain in the bag in the weeks after surgery. Because of this uncertainty, IOLs were designed to be large enough to have one haptic remain outside the bag and one haptic remain inside the bag. With capsulorrhexis, however, an IOL implanted in the capsular bag remains stable and does not move out of the bag. Today, all surgeons perform capsulorrhexis, which has, in turn, revolutionized IOL design. Improving stability: Material vs. shape When the Akreos acrylic material (Bausch & Lomb) was developed in France in 1996 to 1997, the main goal was to increase stability. The majority of IOLs made with hydrophilic acrylic material were one-piece IOLs; haptics were not added to the material as with three-piece IOLs. One-piece designs, however, regardless of material, were considered unstable, although the instability may have been caused by surgical technique rather than by IOL design. Akreos IOL Figure. The four-haptic design of the Akreaos Adapt IOL provides significant IOL stability 6 Source: Bausch & Lomb The first lens developed using the Akreos material was the Akreos Disc. The significant stability improvements of the Akreos Disc led designers to believe the issues with stability were resolved. The increased bulk of the lens, however, required large incisions. The results of Akreos Disc implantation showed that stability was based on design, not on lens material. In 2000, the Akreos Adapt was released with a slimmer design, making it capable of passing through a 3.2-mm incision, which was the standard at the time. The Akreos Adapt is available in three diameter sizes, depending on the optic power of the lens, with larger-diameter IOLs indicated for patients with myopia and smaller-diameter IOLs for patients with hyperopia. The design of the Akreos Adapt was a one-piece IOL with four haptics (Figure), providing significant IOL stability. Studies show that the average decentration of the Akreos Adapt IOL, regardless of lens power, is approximately 0.1 mm, compared with three-piece IOLs, which average 0.3 mm to 0.5 mm of decentration.6 Although the Akreos Adapt IOL demonstrated increased stability and decreased decentration, the IOL’s posterior capsular opacification rate was higher than that of some other IOLs, because a space between the haptics and the optic allowed cells to migrate to the optic.7 Four percent of patients required YAG laser treatment at 1 year compared with 1% to 2% of patients implanted with some of the best IOLs of the time. In 2005, the Akreos Adapt AO IOL was launched. The Akreos Adapt AO improved on the design of the Akreos Adapt by incorporating a 360º barrier on the posterior face of the optic, blocking cells that attempt to migrate from the haptics or the periphery of the bag to the optic in the center of the bag. In addition, the optic was altered from spherical to aspheric. The optic design of the Akreos Adapt AO is a 6-mm, biconvex optic with four acrylic haptics, and the anterior surface is steep to avoid glare and halos. The Akreos Adapt AO has an aberration-free optic that does not interfere with current aberration of the eye. Advantages of evolved design The Akreos Adapt AO IOL provides many advantages over traditional IOL designs. In my experience, the four-haptic design provides better stability than the two-haptic designs of C-loop IOLs. Centration and optic quality of the Akreos Adapt AO are both excellent. Other advantages include low PCO rate and ease of insertion; rotation is not required when implanting the IOL. In my experience, the four-haptic design provides better stability than the two-haptic designs of C-loop IOLs. —Joel Pynson, MD Another feature of the Akreos Adapt AO IOL is the ability of the haptics to remain stable through bag compression after surgery. In most patients, the size of the capsular bag at the time the surgeon is ready to insert the IOL is around 10.5 mm. Some weeks postoperatively, the capsular bag compresses to around 9.5 mm, and most IOL designs remain centered. The Akreos Adapt AO IOL designs, however, will remain centered when a capsular bag compresses to 8.5 mm. This ability to remain centered is a result of the haptic design of Akreos Adapt AO IOLs. With four closed-loop optics, a 360º barrier, and an aspheric optic, the evolving design of the Akreos IOL offers top of the art design for modern cataract surgery. References Barrett GD, Beasley H, Lorenzetti OJ, Rosenthal A. Multicenter trial of an intraocular hydrogel lens implant. J Cataract Refract Surg. 1987;13:621-626. Barrett GD. A new hydrogel intraocular lens design. J Cataract Refract Surg. 1994;20:18-25. Galand A, Van Oye R, Budo C, Goes F, Foets B. Results of implantation in the capsular bag. A short term review of 1,588 cases. Trans Ophthalmol Soc U K. 1985;104:563-566. Van Oye R, Budo C, Galand A, Foets B, Goes F. Two-year postoperative results of Galand lens implantation. J Cataract Refract Surg. 1986;12:135-139. Gimbel HV, Neuhann T. Development, advantages, and methods of the continuous circular capsulorhexis technique. J Cataract Refract Surg. 1990;16:31-37. Mutlu FM, Erdurman C, Sobaci G, Bayraktar MZ. Comparison of tilt and decentration of 1-piece and 3-piece hydrophobic acrylic intraocular lenses. J Cataract Refractive Surg; 2005;31:343-347. Stachs O, Bochert A, Beck R, Stave J, Guthoff R. Preventive effect on posterior capsule opacification of different IOL designs using a standardized test. Paper presented at: XXII Congress of The European Society of Cataract and Refractive Surgeons; September 2004; Paris, France. Joel Pynson, MD, is director of design engineering at Bausch & Lomb, Toulouse, France.

Clinical Performance

Lindstrom: How has the Akreos Adapt AO IOL performed in clinical trials?

Amzallag: A multicenter study was carried out in Sweden by Johansson and colleagues to compare the optical performance of the Akreos Adapt AO IOL and the Tecnis Z9000 IOL. In this bilateral implantation study on 80 patients, both IOLs performed similarly in terms of photopic and mesopic contrast sensitivity. As expected, more spherical aberration was found in eyes implanted with the Akreos Adapt AO IOL. This is primarily due to the spherical aberration that remains in the cornea, because of the aberration neutrality of the Akreos Adapt AO IOL. Because of this positive spherical aberration remaining in the eye, the mean depth of field was higher in eyes implanted with the Akreos Adapt AO IOL compared with the eyes implanted with the Tecnis IOL. When patients were asked to assess their surgery results in a double-masked interview, twice as many patients preferred the vision in the eyes implanted with the Akreos Adapt AO IOL. The Akreos Adapt AO IOL also had fewer reports of undesirable effects on sight in different light conditions and disorders such as dysphotopsia (Figure 7). ¹⁰

Bilateral implantation study: Double-masked questionnaire Figure 7. Survey results in a double-masked interview demonstrate that twice as many patients preferred the vision in the eyes implanted with the Akreos Adapt AO (Bausch & Lomb) IOL than a silicone aspheric aberrated IOL. The Akreos Adapt AO IOL also had fewer reports of dysphotopsia.10 Source: Bausch & Lomb

Nichamin: Results for the Akreos Adapt IOL in the initial trials in the United States have been excellent. The IOL has met or surpassed all historical FDA grid endpoints. The initial trials were performed in 14 sites in the United States, with 355 IOLs implanted.

In my own series, the mean BCVA was 20/24 after implanting the Akreos Adapt IOL, and uncorrected visual acuity was 20/38. Both results are better than the FDA grid. Adverse events related to the Akreos Adapt IOL were not reported by any of the trial sites. The overall performance has been excellent.

Lindstrom: How well does the Akreos Adapt AO IOL perform in regard to capsular stability?

Amzallag: In my experience, the Akreos Adapt AO IOL is extremely stable in the capsular bag. The IOL has been found to be an exceptional alternative in cases of posterior capsular rupture. With its four haptics, the Akreos Adapt AO IOL can be placed with two haptics under the capsulorrhexis and two haptics over the capsulorrhexis to achieve a combined bag and sulcus fixation.

Lindstrom: Plate haptic IOLs have a history of higher instances of decentration. The FDA grid on decentration has plate haptics at 1%. If more than 1% of IOLs decenter to the point where a secondary surgical intervention is necessary, such as rotating, removing, or exchanging the IOL, then the IOL would not rate well. The decentration rate of the early plate haptic IOLs was 2%, which bothered some surgeons who were accustomed to less than 1% with the three-piece IOLs.

The Akreos Adapt AO IOL is designed with four closed-loop haptics so that the capsule will fold over the openings and seal the anterior and posterior capsule, creating, in effect, small spot-welds to hold the IOL in place. The closed-loop haptics are also designed to provide a comfortable, equatorial pressure on the capsular bag. When an ophthalmologist implants the IOL, the IOL auto-centers and the capsule contracts, which spot-welds the IOL in place. Decentration has been low with the Akreos Adapt AO, with reports of decentration occurring in 0.2% to 0.3% of patients. The Akreos Adapt AO is significantly different from the plate haptic silicone IOLs with which decentration occurred in 2% of patients.

How does the Akreos Adapt AO IOL compare with other IOLs in regard to difficulties with decentration?

Amzallag: A clinical study was performed by Davies to evaluate centration of the Akreos Adapt AO IOL using a photographic method. Decentration of the IOL was minimal, with a mean lateral movement of 0.048 mm (SD = 0.02) and no variation at 3 weeks, 3 months, 6 months, and 1 year.¹¹ The results compare favorably with the mean decentration reported on C-loop designs, which varies from 0.3 mm to 0.5 mm.

Lindstrom: How does the Akreos Adapt AO IOL perform in regard to PCO?

Amzallag: All Akreos IOLs have square edges, which are known to help minimize PCO. On the Akreos Adapt AO design, a 360º posterior barrier was added to reinforce its anti-PCO features and to prevent cell migration at the haptic and optic junction. Pfeifer has evaluated PCO with the Akreos Adapt AO IOL in 41 eyes, using retro-illumination pictures analyzed by an independent operator using EPCO 2000 software. EPCO scores at 1 year were extremely low, with 0.048 in the 6-mm optic area and 0.012 in the 3-mm central area. The results are comparable to those from the best performing hydrophobic acrylic IOLs (Figure 8).¹²

Akreos Advanced Optics Figure 8. EPCO scores of the Akreos Adapt AO (Bausch & Lomb) IOL from a study evaluating PCO were extremely low, according to a study on 41 eyes, with results comparable to the best performing hydrophobic acrylic IOLs.12 Source: Bausch & Lomb

Lindstrom: Are there any other potential postoperative problems ophthalmologists should anticipate?

Apple: Ophthalmologists should look for primary and secondary calcification after implanting any hydrophilic acrylic IOL. Primary calcification indicates an inherent problem with the IOL. To date, primary calcification has not been observed in the Akreos family of lenses and they have been on the market for more than 8 years in Europe and have been implanted in over one million eyes.

Secondary calcification can affect any IOL and indicates a pre-existing condition in the eye that caused a breakdown of the aqueous barrier and the subsequent development of calcium deposits on the IOL. Ophthalmologists must understand the differentiation between primary and secondary calcification.

Retinal protection

Lindstrom: Why is retinal protection an important component of good IOL design?

Nichamin: Retinal protection is a hotly debated topic among ophthalmologists. Age-related macular degeneration is the leading cause of blindness in developed countries, and many ophthalmologists believe parts of the UV spectrum may increase the chance of AMD later in life. Historically, IOL implants have incorporated UV-blocking agents. Some ophthalmologists now advocate incorporating blue light-blocking IOLs. As of yet, however, no substantive data support the need for blue light-blocking technology. The debate is in transition as ophthalmologists try to determine which portion of the light spectrum requires blocking.

Chow: The aphakic hazard curve is a phototoxicity risk curve created by Dr. Ham from his work on primates.¹³ In his model, he shined various wavelengths of UV and blue light into the eyes of primates for varying lengths of time and then evaluated for the presence of phototoxicity. His curve basically identifies that, as the eye is exposed to shorter and shorter wavelengths, these wavelengths carry an increasing risk of causing phototoxicity.

The Acrysof Natural (Alcon) and SofPort AO Violet Shield lens (Bausch & Lomb) are two new light-blocking IOLs. The Violet Shield technology IOL blocks the more dangerous forms of UV radiation, which are wavelengths below 400 nm. Yet, because the SofPort AO Violet Shield IOL has a transmission curve that rises steeply to allow 80% transmission of light by approximately 430 nm, it does not block out the higher wavelengths of blue light, which coincide with the scotopic response curve and may be useful for night vision and various other visual functions in addition to its role in regulation of the circadian system (Figure 9).

Retinal Sensitivity Figure 9. The SofPort AO Violet Shield IOL (Bausch & Lomb) does not block out the higher wavelengths of blue light, which coincide with the scotopic response curve and may be useful for night vision and various other visual functions in addition to its role in regulation of the circadian system. Source: Bausch & Lomb

Lindstrom: Night driving requires blue light perception, which is why patients have night myopia. The pupil is bigger as visual perception moves to the longer wavelengths and the shorter wavelengths become distorted. A patient implanted with blue light-blocking technology has a significant loss of quality mesopic function because the cones are more blue-light driven.

What are the drawbacks to using blue light-blocking technology?

Chow: One interesting secondary side effect of blue-blocking IOLs is that the IOL will change the color of the endoillumination, which retina surgeons observe at the eyepieces while performing a vitrectomy. The IOLs that are filtering out light so that it does not reach the retina also filter out light that is coming back up to the microscope. The net effect is a shift in the chromatic appearance of our endoillumination light source toward yellow.

Lindstrom: Some alarming information has been reported recently suggesting some human core circadian rhythms, such as when we sleep and the natural cycles of human cells, are regulated in the base of the brain through cycles that are influenced by blue light. I am uncomfortable with influencing that physiology without a very good reason.

The Future of IOLs

Lindstrom: What is the future of IOL technology?

Amzallag: The future is the micro-incision aspheric IOLs that will offer the additional advantage of astigmatism-neutral cataract surgery. I also expect to see aspheric IOLs that will offer a better solution to correct presbyopia.

Devgan: Similar to how every IOL on the market has a UV coating, most IOLs now have squared edges to prevent PCO. The next wave is asphericity. In the near future, every IOL on the market will have an aspheric design of one type or another.

In the near future, every IOL on the market will have an aspheric design of one type or another. —Uday Devgan, MD, FACS

Apple: After 25 years in the industry, I believe the IOLs with a simple design outperform the IOLs with complex designs, because the simple designs can be used as a platform for other IOLs, including accommodative IOLs, refractive IOLs and aberration-preventing IOLs. It is also important that the platform has the potential to meet the future needs of micro-incision cataract surgery.

Chow: The ideal IOL for the retina specialist will be one that provides good anatomic and visual results as defined by my cataract surgery colleagues; provides clear undistorted global viewing of the peripheral and posterior retina, particularly in our surgical retina patient population; and blocks potentially damaging radiation to the retina without compromising visual function.

Nichamin: Ophthalmologists will continue to learn about higher-order aberrations and how they can best address them with the aspheric IOL design options available to them today. I believe ophthalmologists will continue to leverage this type of technology and ultimately move toward customized implants that will address a patient’s unique set of higher-order aberrations.

Lindstrom: The future of aspheric IOL design will be customization and material advances that enable micro-incision cataract surgery. Ophthalmologists who perform refractive surgery have the ability to measure a patient’s spherical aberration preoperatively, and can measure the entire eye. Soon, ophthalmologists will be able to measure just the cornea. If the natural lens is removed, all that is left is the corneal spherical aberration. Ophthalmologists can then use an IOL that will neutralize the spherical aberration. There will be a group of IOLs with various spherical aberrations ranging from –0.3 mm to 0.3 mm and these advanced material IOL’s will be implantable through sub-2 mm incisions allowing greater safety and better astigmatism control.

How do you think IOL technology will affect your practice in the future?

Amzallag: The distinction between cataract and refractive surgery will disappear. In the future, ophthalmologists will include more preoperative examinations such as aberrometry of patients with cataracts, and will have a more customized refractive approach.

The future of aspheric IOL design will be customization and material advances that enable micro-incision cataract surgery. —Richard L. Lindstrom, MD

Nichamin: Nearly all of my patients who receive a monofocal implant receive some type of aspheric IOL. In the future, I believe multifocal and accommodative designs will also incorporate aspheric optics.

Devgan: IOL technology already affects my practice. I no longer carry a consignment of IOLs that have positive spherical aberration. In my surgery center I use aspheric IOLs that have zero spherical aberration, and I use IOLs that have negative spherical aberration. I do not routinely carry IOLs that have positive spherical aberration; however, if I find that a patient will benefit from the positive spherical aberration IOL, then I will order it.

Lindstrom: Currently, I use a spherical IOL only when neutralizing a patient’s preoperative negative spherical aberration of the cornea is necessary. I believe every other patient should have an aspheric IOL implanted. The only exception is when a patient’s primary goal is to reduce dependence on glasses. In those patients, ophthalmologists must consider accommodating and multifocal IOLs. For the typical patient, however, there is no reason not to give the highest quality optical possible; an aspheric IOL.

I would like to thank the panel members for their comments, Ocular Surgery News for organizing this symposium, and Bausch & Lomb for providing its support.

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