IOLs, customized ablation highlight ASCRS

SAN FRANCISCO, U.S.A. — Accommodative IOLs and customized ablation were two of the main topics of interest at this year’s American Society of Cataract and Refractive Surgery meeting.

One study of particular interest, conducted by Tobias Neuhann, MD, found that accommodative IOLs “still work,” even at 2 years postop.

Other IOL technologies for both cataract and refractive surgery — including phakic IOLs, ultrathin designs and light-adjustable materials — also attracted much attention. In addition, capsular tension rings for complicated cataract cases drew considerable interest.

Attendance was up slightly over the 2002 meeting, despite the conflict in Iraq and fears regarding severe acute respiratory syndrome (SARS). ASCRS officials estimated that registration for medical personnel was nearly 6,200.

Following are some other highlights of the meeting. Many of these items appeared previously on OSNSuperSite.com as part of our daily coverage from the meeting. Note that this article is not meant to be an all-inclusive representation of the ASCRS meeting, but rather a sampling of some of the interesting presentations. Look for more in-depth coverage of these and other presentations at ASCRS in upcoming issues of Ocular Surgery News.

Survey: IOL complications

The reasons for explantation of foldable IOLs vary according to lens type, according to an annual survey. Improvements in manufacturing processes and the use of careful surgical techniques could help avoid the most common causes of IOL explantation, the survey’s presenter said.

Nick Mamalis, MD, discussed the results of the 2002 ASCRS/European Society of Cataract and Refractive Surgeons annual survey of foldable IOLs requiring explantation or secondary intervention.

Survey respondents filled out a form for each IOL they explanted. Preoperative data was collected, as well as the type of IOL removed and the reason for its removal.

According to the survey results, hydrophilic acrylic IOLs continued to be removed because of significant postoperative calcification. Three-piece silicone IOLs, three-piece acrylic IOLs and one-piece acrylic IOLs were most commonly removed due to incorrect power calculations. Dislocation and decentration were the most common complications leading to removal of one-piece silicone IOLs.

Although glare or visual disturbances were seen less frequently as reasons for removal, multifocal silicone IOLs were most commonly explanted for those reasons.

Pallikaris, Kelman honored

The wealth of information that is known about human vision pales in comparison to what has yet to be learned, said a surgeon honored during the Innovator’s Session.

Ioannis G. Pallikaris, MD, PhD, struck a humble chord as he delivered the Charles D. Kelman Innovator’s Lecture. This is the first year the Innovator’s Lecture has been named for the ophthalmologist who invented phacoemulsification.

Dr. Pallikaris said it is hard to pinpoint the optimal refractive target, so achieving perfection is an elusive goal for ophthalmologists.

“We probably don’t know what the optimal refractive target is because it is a ‘moving target,’” he said. “The ocular refractive state is not static … and our receptors mosaic is always changing.”

A realistic goal for ophthalmologists, Dr. Pallikaris said, is to “accept optical imperfections, because this represents the essence of human vision.”

Dr. Pallikaris, of the University of Crete, is the developer of a technique similar to laser epithelial keratomileusis (LASEK), which he dubbed “epi-LASIK,” from the Greek root “epi,” meaning superficial. In Dr. Pallikaris’ technique, mechanical separation of the corneal epithelium is accomplished without the use of alcohol.

Dr. Pallikaris said his objective in creating the technique was to find a way to avoid using alcohol during LASEK, because histologic studies have shown that alcohol can affect the integrity of the epithelial basement membrane. The epi-LASIK technique helps maintain a healthier cornea during and after the procedure, he said.

Dr. Kelman was on hand to introduce the lecture that now bears his name. His speech avoided conventional ophthalmologic topics. Instead, he spoke about the characteristics of an innovator.

Innovation has little to do with intelligence, he said, and everything to do with creativity and the ability to listen to the inner muse.

“The creative act is as close as we can get to the divine,” Dr. Kelman said.

He urged ophthalmologists to be open to working with young practitioners who may not exactly fit the mold, but who exhibit a creative spark.

“How many potential Einsteins or Edisons of ophthalmology have been summarily rejected, we’ll never know,” Dr. Kelman said.

Incoming ASCRS president

Also in the opening session, Stephen S. Lane, MD, was introduced as the incoming president of ASCRS. During his induction address, Dr. Lane noted that organized medicine and the health care delivery system face numerous challenges, and that the U.S. government has an important role to play in health care.

Dr. Lane accepted his presidential medal from the outgoing ASCRS president, Marguerite B. McDonald, MD.

Accommodative IOLs at 2 years

Patient motivation is a key factor in the success of accommodative IOLs, according to a surgeon who has been implanting the lenses for more than 2 years.

“The magnitude of accommodative power is greater if the patient is motivated to use it,” said Tobias Neuhann, MD. He described his long-term experience with the C&C Vision CrystaLens here.

“The question is, do these lenses still work at 2 years postop, and the answer is Yes,” he said.

Dr. Neuhann began implanting the C&C Vision lens in July 2000, and he now has 14 patients with more than 19 months’ follow-up. Accommodative amplitude in these patients ranges from about 1.5 D to 3 D at most recent follow-up, he said.

Initially, Dr. Neuhann said, patients tend to have a high degree of accommodation, but at 3 months the amplitude begins to decrease somewhat. He said when he first noted this phenomenon, he was disappointed and felt the accommodative IOL was failing. In response, Dr. Neuhann said he prescribed the standard 2.5 D spectacle add for these patients, and at 1 year their accommodative performance was relatively poor.

But he said he has since discovered that a smaller degree of spectacle add – or none at all – is enough for most of his accommodative IOL patients to see well at distance and near.

“If patients are motivated to use their accommodation, they will use it,” Dr. Neuhann said. “The add required for most patients to achieve Jaeger 1 is about 1 D to 1.5 D.”

Dr. Neuhann said that at 2 years, binocular near vision of J2 can be achieved by almost 100% of patients with their distance correction in place.

“Our results at 2 years are much better than at 1 year,” he said.

Sizing important for phakic IOLs

Great care must be taken in sizing phakic IOLs considering the length of time they will remain in patients’ eyes, said a surgeon with experience with several models of phakic IOL.

Very high frequency (VHF) ultrasound and optical coherence tomography measurements of angle-to-angle and sulcus-to-sulcus distances can provide a more precise estimate than do white-to-white measurements, said Carlo F. Lovisolo, MD.

“It is completely unacceptable to me that we size a lens without knowing the exact measurements, especially when the lens is to be in place for 40 to 50 years,” Dr. Lovisolo said.

In the future, Dr. Lovisolo said he hopes to see phakic IOLs customized to individual patients. While acknowledging that day may be a long way away, he said for now surgeons should not be relying on the white-to-white external measurement technique alone.

Dr. Lovisolo and associates conducted a study to assess the accuracy and predictability of different methods of choosing the overall length of anterior and posterior chamber phakic IOLs.

Four groups of patients were implanted with either angle-fixated lenses or STAAR posterior chamber ICLs. Two of the patient groups (20 eyes each) were sized using conventional sizing techniques based on external white-to-white measurements, including devices such as rulers, calipers and photographic techniques. The other two patient groups (30 eyes each) were implanted with the same types of lenses, but were sized based on information from newer technologies. These included VHF echography and optical coherence tomography.

The study found that the second two groups rated significantly higher in terms of vault predictability, and their complication rates were lower.

“It’s not just about sizing with expensive instrumentation, but in the future we should be moving toward ordering every phakic IOL on a customized basis to avoid complications down the line,” Dr. Lovisolo said.

Adjustable IOL

Technology used in customized ablation may be copied in IOLs to allow adjustment of the lens inside the eye, according to one presenter.

"Patients expect emmetropia and accommodation," said John Hunkeler, MD.

Dr. Hunkeler spoke about PowerVision's power-adjusting lens, now in U.S. development, which theoretically can be corrected for defocus error and higher-order aberrations using a pixilated actuator. Piston-driven actuators are individually adjusted, and the optical thickness of the lens is manipulated at multiple locations to adjust the local power of the lens surface.

The lens is irradiated by this pixilated actuator around its edge to correct for myopia or astigmatism, Dr. Hunkeler said. Because the lens has a layer of fluid cells in its center, the surgeon can potentially repeat the process as often as needed as the patient's eye changes.

"The whole process is repeatable," he said. "You can adjust the lens as frequently as you want."

Natural sunlight does not alter the lens, Dr. Hunkeler said during a question and answer session.

The lens will be entering animal studies in the near future, Dr. Hunkeler said.

Wavefront analysis of Tecnis

The Tecnis IOL seems to correct the spherical aberration in the eye’s optical system, according to a study using wavefront analysis.

Roberto Bellucci, MD, of Verona, Italy, described a study he performed comparing several types of IOL using the Topcon Wavefront Analyzer, which measures both wavefront characteristics and corneal topography simultaneously.

The 25 patients in the study were implanted in equal numbers with one of five types of IOL: the Tecnis, the 911 Edge or 812 C from Pharmacia, or the one-piece or three-piece AcrySof from Alcon.

Dr. Bellucci explained that the output of the Topcon device shows both corneal spherical aberration and the total spherical aberration of the eye’s optical system, so it is possible to calculate how much of the aberration is produced by the lens. He said total spherical aberration was reduced by the Tecnis and increased by all the other IOLs studied.

Measured with both a 6-mm and a 4-mm pupil, the total spherical aberration in eyes with the Tecnis was zero, he said. The conclusion of the study was that the Tecnis corrects the spherical aberration present in the human cornea.

Dr. Bellucci acknowledged a financial interest in his subject matter. He was awarded Best Paper of Session by the moderator and panelists for his presentation.

Modified capsular tension ring

Adding extra eyelets to capsular tension rings may make the devices easier and safer to insert, according to a surgeon speaking here.

Jaime Zacharias, MD, described his experience with several prototypes of a modified capsular tension ring.

Standard capsular tension rings have eyelets at each end to facilitate manipulation with hooks and other instruments. Dr. Zacharias pointed out that these standard rings contact the capsular bag at a steep angle during insertion, putting pressure on the bag and increasing the potential for tears in the capsule and other complications.

To address this problem, he designed a ring with several additional eyelets at intervals around its circumference to allow compression of the ring into a tighter circle, thus avoiding the stress on the capsule.

He described three possible techniques for inserting the modified rings. In one, an instrument he called a "trinserter" is used to grasp two of the inner eyelets to compress the ring for insertion. In a second, a suture is passed through all the eyelets before the ring is inserted. The ring is compressed by tightening the suture, and then it is dialed into the capsule. In a third technique, a specially designed inserter, also in the prototype stage, is used to gently inject the ring into the capsule.

Dr. Zacharias noted that further refinement is needed, both for the ring itself and for the insertion techniques he described. He expressed hope that the modified rings will eventually make capsular tension ring insertion easier and safer.

Dr. Zacharias acknowledged a financial interest in the devices he described.

Shortcomings of wavefront

Until certain fundamental issues are resolved, wavefront customized ablation will not live up to heightened expectations, said refractive surgeon and optics expert Jack T. Holladay, MD.

Several inherent problems with the technique will for the time being prevent wavefront from becoming the laser technique of choice for most surgeons, Dr. Holladay said.

First, he said, wavefront-guided lasers have not compensated for oblique incidence of light on the cornea. The result of this is that the cornea becomes oblate, when it should be prolate, he said.

A second inherent problem he noted is that the wavefront-guided laser must be perfectly aligned or else the off-axis corrections will not work.

“When you correct lenticular aberrations on the cornea, it creates an ‘extreme’ on-axis system. (The laser) is not lined up for off-axis images,” he said.

Further, direct correction of the eye with wavefront “assumes the path through the crystalline lens is the same,” Dr. Holladay said. “Actually, the rays pass through different locations in the crystalline lens, introducing different aberrations.”

The flap created during LASIK can also induce its own series of aberrations, such as astigmatism and higher-order RMS error, he said.

Wavefront-guided correction is also limited by the characteristics of the tracking system used.

“You must have absolutely perfect fixation, which is not possible at this point,” he said.

Finally, Dr. Holladay said, contrast sensitivity should be the primary measure of visual performance, but it is impossible to gauge true contrast sensitivity after wavefront surgery because it always declines postoperatively.

“So far, custom ablation studies do not show improvement in (contrast sensitivity),” Dr. Holladay said.

Bimanual phaco with Infiniti

Bimanual cataract surgery with the Alcon Infiniti cataract system is safe and takes no longer than conventional phaco, according to one surgeon.

Richard B. Packard, MD, FRCS, spoke on his experience with the Infiniti system, which Alcon introduced at the meeting. Dr. Packard said he performed conventional phaco on 10 patients and bimanual phaco on 10 patients with the Infiniti system. Length of surgery was used as the outcome, he said. In both groups, surgery time was about 12.5 minutes.

He described one case of a hard cataract. During surgery with the Infiniti, Dr. Packard said the chamber remained stable, there was low energy dissipation, “and the wound remained pristine. This equipment is completely predictable.”

Dr. Packard is a consultant for Alcon.

Manipulator for soft IOLs

A manipulator for soft IOLs makes insertion faster, easier and “more precise,” according to one surgeon.

Herbert J. Nevyas, MD, presented his experience with this instrument, which consists of a “mildly enlarged” Sinskey hook with a heavily roughened surface. The inner aspect of the hook is concave and roughened. Dr. Nevyas said the instrument, made by Katena, rotates the lens by contact with the optic and retrieves, repositions and “hooks” the haptic from the anterior chamber.

He explained that this instrument rotates a soft IOL due to its increased friction with the surface of the optic. It also retrieves the haptic from the anterior chamber angle by increased traction on the haptic. Dr. Nevyas noted there is less likelihood of slippage due to contact of the haptic with the roughened concave inner hook.