ESCRS winter meeting addresses big questions in refractive surgery

Is super-vision possible? Are customized surface procedures better than LASIK? Do accommodative IOLs really move? Is clear lens exchange preferable to phakic IOL in highly myopic patients?

BARCELONA – As the collective experience with refractive surgery grows, new certainties emerge, but at the same time new doubts are raised. And doubt in science is a potent stimulus to new research.

This ongoing dialogue between statements and questions made the 2004 winter refractive surgery meeting of the European Society of Cataract and Refractive Surgeons, held here, lively and animated. Panels and audience members participated in passionate discussions on a range of issues. Some of the top controversies discussed at the meeting are highlighted in this article.

Super-vision not at hand

A symposium and many free papers on wavefront technology and wavefront-guided procedures demonstrated that the experience in this relatively new field is widening. The technology is increasingly becoming integrated into the daily practice of many refractive surgeons. The audience had the chance to compare results with different lasers and aberrometers and to be updated on the latest software available.

An opinion often repeated on the podium was that customized laser treatment produces better visual results than conventional treatment and allows tissue-sparing surgery. But the dream of routinely creating super-vision, which seemed close at hand when customized ablation was first developed, appears today more difficult to achieve, speakers said.

The achievement of super-vision was cited by the chairman of the symposium, Jorge L. Alió, MD, as “one of the main question marks raised by this technique at this moment.”

The success of customized ablation with LASIK is limited by the uncontrollable effects of flap behavior, speakers noted.

Corneal scanning with the Ultralink Artemis II high-frequency digital ultrasound system, presented by Dan Z. Reinstein, MD, demonstrated that the concept of a parallel interface is not achieved at the micron level, even with the most sophisticated keratome.

“The Artemis produces micronically precise three-dimensional maps of each layer of the cornea, so that we can see the effects of LASIK at all levels. Irregularities in the stromal bed and flap interface and differences in flap thickness between the center and the periphery are clearly visible in all cases. In addition, un-predictable epithelial changes can be seen in the more superficial layers, due to wound healing processes,” Dr. Reinstein said.

He pointed out that flap irregularities alter the biomechanical response of the cornea, inducing unwanted curvature changes and, consequently, lower-order aberrations.

“If we have no control of lower-order aberrations, we cannot even think of reducing other aberrations. Therefore, my answer to the question ‘is super-vision possible with the current microkeratome technology?’ is ‘no,’” he said.

Dr. Reinstein also raised the problem of the safety of enhancement procedures, which, he said, “are very tissue-intensive.” Analysis with the Artemis system revealed that in most cases the flap and corneal thickness are difficult to predict and that, consequently, residual thickness is often lower than intended, he said.

On the other hand, current ultrasound technologies are increasingly capable of producing highly reliable preoperative digital simulations of the effects of surgical procedures, which should in future increase the predictability of results, he said.

“If we could identify epithelial and mechanical changes before performing LASIK, there could be a better control of corneal shape, and this would have an impact on the induction of aberrations and on the achievement of super-vision. It is possible that current technologies might offer these possibilities,” Dr. Reinstein concluded.

Surface ablation

According to other speakers, customized surface-ablation treatments offer a better possibility of achieving optimal quality of vision because they are more predictable and do not induce the same degrees of aberrations as LASIK.

In a comparison of 40 myopic patients treated with customized laser epithelial keratomileusis (LASEK) or LASIK, Joseph Colin, MD, demonstrated that fewer higher-order aberrations were induced by LASEK. This was probably due to the hinge and interface effects of LASIK, Dr. Colin said.

The same opinion was shared by Vikentia Katsanevaki, MD, who said that, while the stromal flap inevitably alters the results of customized treatment, the epithelium tends to be “very forgiving.” According to Dr. Katsanevaki, LASEK provides epithelial protection to the ablated surface and avoids induced aberrations. She advocated the use of the LASEK variant epi-LASIK, described by Ioannis Pallikaris, MD, in which the epithelial flap is mechanically separated using a special device. This method, she pointed out, prevents potential damage from the alcohol solution that was used to perform the epithelial flap in Camellin’s original LASEK technique.

“Epi-LASIK prevents the fibrotic activation of fibroblasts and preserves an intact basement membrane, thus preserving the viability of the epithelial tissue. Healing processes take place in a fast, natural and nontraumatic way, without causing morphological alterations to the cornea and, consequently, aberrations,” Dr. Katsanevaki said.

Another point of view on the question of how to achieve optimization of visual quality was offered by Dr. Alió, who hypothesized that super-vision might be provided more reliably by phakic IOLs than by laser surgery.

“Phakic IOLs are perfectly controllable, can be designed with exactly the aspheric profile that you want, can be customized and don’t cause unpredictable biomechanical changes. In addition, they aren’t there forever, and you can change them according to progressive age-related modifications of the total aberrations of the eye,” Dr. Alió pointed out.

Refractive IOLs

The sessions on refractive IOLs highlighted the advances in visual quality in these technologies. While studies of well-known products such as the Ophtec Artisan phakic IOL and the OII Phakic 6 continue to confirm their efficacy, lenses more recently introduced are also gaining popularity.

Among these is the anterior chamber phakic I-Care IOL from Corneal, which is showing good anatomic and visual results, speakers said. In 23 eyes implanted with this lens, Roberto Bellucci, MD, and Simonetta Morselli, MD, measured corneal and total aberrations. They concluded that “the optical quality achieved with the I-Care is comparable with that of pseudophakic eyes. In other words, it is slightly less than in a virgin eye, but definitely suitable for a phakic IOL.” Because of the IOL’s minimally traumatic design and material, they added, the lens fits well in the eye without producing anatomic alterations. Complications such as angle erosion, pupil distortion, cataract, uveitis or inflammation, which have been reported with other anterior chamber lens designs, were never seen with the I-Care, they said.

“In the last 5 cases, we didn’t even perform iridotomy, but this didn’t cause any problem thanks to the vaulting of the lens,” Dr. Morselli pointed out.

Francesco Carones, MD, said the advanced technology of intraocular implants for the aphakic eye – whether following cataract surgery or clear lens extraction – is a sign of how cataract surgery is rapidly merging with refractive surgery.

“Patients have high demands and expectations regarding this kind of surgery, and we do have the technology to give them not only a plano refraction at distance, but also a correction of pre-existing or induced presbyopia,” he said.

Dr. Carones presented his preliminary results with the pseudoaccommodative Alcon AcrySof Restor IOL, a new variation on the multifocal diffractive IOL. The Alcon lens has a large 6-mm apodized optic with a central 3.5-mm diffractive portion.

“Within this 3.5-mm zone there is a series of concentric rings with gradual decrease in step height for smooth transitions between distance, intermediate and near focal points and reduction of glare and halos,” Dr. Carones said. He described a study in which the visual outcome in all eyes was 20/25 or better at distance and J2 or better at near, with slightly lower performance (J4 or better) in intermediate vision.

Accommodative IOLs

Among accommodative IOLs, the HumanOptics 1CU and the eyeonics (formerly C&C Vision) CrystaLens dominate the European market.

A new lens based on similar principles of reproducing accommodative movement, the Kellan K3500 (Lenstec), was discussed by Deepak K. Chitkara, MD. The lens is made of a biocompatible hydrophilic acrylic material. It has a large optic and is injectable through a small incision, Dr. Chitkara said. The surgeon said he has implanted it in 42 eyes of 28 patients, mostly hyperopic, following clear lens extraction.

“The lens is showing high predictability and stability of results,” Dr. Chitkara said. “Nearly 40% of the patients gained 1 or more lines, and all of them had binocular near vision of J3 or better, which is excellent useful near vision on top of very good distance vision.”

A paper by George Baïkoff, MD, however, presented doubts concerning the mechanism of action of accommodative IOLs. Dr. Baïkoff presented objective measurement of the movements of the 1CU, the CrystaLens and the ThinOptX IOL that were obtained using optical coherence tomography of the anterior segment. He said measurements with a prototype anterior chamber OCT instrument showed that the actual forward shift of all these lenses ranged from a few microns to nothing, even after injection of pilocarpine.

“Since it has been proven that 1.5 D of accommodation requires 1 mm of forward movement of the lens, there should be no effect of these implants on near vision. And yet most of the patients are able to read J2 or better,” Dr. Baïkoff said.

In a discussion that followed, several comments were made concerning Dr. Baïkoff’s contradictory results.

“It might be possible that, in some cases, patients could see well also before the implantation, or that our measurements are not reliable. Or perhaps there is not such a direct correlation between lens movement and accommodation,” Dr. Chitkara suggested. “There might be some still unknown reason why patients see better with accommodative implants.”

Günther Grabner, MD, noted that there is a need for standard reading charts, scales and methods to measure near acuity.

“If we don’t make a serious effort in the direction of standardization, we cannot compare or even analyze correctly our results, and we are doing bad science,” Dr. Grabner said.

Dr. Alió added that reading speed rather than static reading of single characters should be assessed when evaluating near vision. The session ended with his statement that further research is needed to disclose other still unknown mechanisms behind accommodation and the functioning of accommodative implants.

Lamellar corneal surgery

Lamellar keratoplasty was a point of great interest in several symposia and individual presentations dedicated to the cornea, including an international course on Pathology and Corneal Surgery.

In corneal diseases in which the patient’s endothelium can be preserved, such as keratoconus, anterior corneal dystrophies and stromal scarring, deep anterior lamellar keratoplasty (DALK) offers an alternative to penetrating keratoplasty (PK), some speakers said.

“The recent improvements in surgical technique have broadened the indications of DALK, with the consequent indisputable advantages of preventing rejection-related problems and premature impoverishment of the endothelial cell density in young patients,” said Vincenzo Sarnicola, MD.

The technique was presented in its numerous variations, including the conventional, entirely manual technique; air- and hydro-dissection methods; and approaches using the Guided Trephine System and laser assistance.

Posterior lamellar keratoplasty (PLK) is, on the other hand, indicated in eyes with corneal endothelial disorders and a transparent surface. In a variation presented by Gerrit Melles, MD, the patient’s Descemet’s membrane is stripped, removed and replaced by a donor graft through a small 5-mm scleral incision.

“The small incision makes this technique safer and far less invasive than PK. Surgical time is also much shorter, and once you have mastered it, the procedure is not difficult at all,” Dr. Melles said.

Corneal ectatic diseases

Some good news about keratoconus was announced by Francois Malecaze, MD.

“It is reasonable to think that the keratoconus gene will soon be discovered,” he said. Dr. Malecaze is taking part in a multicenter research project that has recently localized a specific region in a chromosome containing a gene that he said is responsible for 70% of European familial keratoconus cases.

“Finding the gene for keratoconus will improve our diagnostic criteria and will lead to new therapeutic strategies aimed at slowing down the progression of the disease and avoiding corneal grafting,” he said.

Corneal ectasia following LASIK was discussed by Doyle Stulting, MD, in a presentation on the corneal complications of refractive surgery. He said major risk factors for post-LASIK corneal ectasia include forme fruste keratoconus, myopia of greater than 8 D and a residual stromal bed thickness of less than 250 µm. Multiple enhancements were also associated with the development of corneal ectasia, he said.

Dr. Stulting also discussed the most effective methods, old and new, for treating this complication.

“There are some relatively new treatments for ectasia today,” he said. “The use of Intacs (Addition Technology), first reported in 2000 by Joseph Colin, reduces the corneal curvature and absorbs some of the stress imparted to the cornea by IOP. The Ferrara Ring (Mediphacos) is another type of intracorneal ring segment of smaller diameter.”

A possible new treatment for the condition is collagen crosslinking with riboflavin followed by ultraviolet light exposure, Dr. Stulting said. “Regression in keratometry and spherical equivalent and improved visual acuity were reported after the treatment,” he said.

High refractive error: RLE

The risks and benefits of different treatment options for high refractive errors were considered in the concluding symposium of the meeting.

Concerning refractive lens exchange (RLE), Richard Packard, MD, said that the procedure is a viable option for selected cases.

“Thanks to the recent improvements in patient selection, preoperative examinations and treatment options, most complications have been addressed. However, retinal detachment remains a major concern in high myopic eyes and a loss of BCVA is still quite common in hyperopic patients,” Dr. Packard said. In extremely high myopia or hyperopia he recommended a cautious attitude and special attention to the surgical procedure, taking into account the particular anatomy of these long and short eyes.

High-quality methods for axial length measurement and IOL power calculation are also essential to the success of the procedure, said Wolfgang Haigis, MD. Results of a good surgical technique, he said, can be spoiled by errors in biometric measurement and IOL power calculation.

“Partial coherence interferometry biometry is the newest and most accurate method for measuring the length of eyes,” Dr. Haigis said. “As far as the formulas for IOL power calculation are concerned, we must remember that some are better for long eyes and others for short eyes. The Haigis formula is good for all eyes, and the Hoffer Q is an accurate formula for nanophthalmic eyes,” he suggested.

Paul Rosen, MD, presented a meta-analysis of papers on retinal detachment rates after various types of refractive surgery. He found an incidence of 0.05% to 0.3% following LASIK and 4.8% following phakic IOL implantation. The rate of retinal detachment after RLE in high myopic eyes was the highest, he said. Dr. Colin and others have reported a long term rate of retinal detachment as high as 8% after RLE in high myopes, Dr. Rosen noted.

“It is true, however, that a recurrent theme in these papers is the high proportion (up to 60% in Dr. Colin’s series) of Nd:YAG capsulotomy in these patients, which would suggest that the capsulotomy procedure dramatically increases the risk of retinal complications,” Dr. Rosen pointed out.

To surgeons who perform RLE he suggested a thorough preoperative examination of the retina and extensive use of laser retinal prophylaxis, even in asymptomatic patients with atrophic breaks.

High refractive error: Phakic IOLs

Phakic IOLs were another option discussed for high refractive errors.

Dr. Baïkoff said refractive IOLs are increasingly recognized as the best and safest option for high refractive errors. A key point of his presentation discussing the pros and cons of angle-supported lenses was the need for accurate IOL sizing, now obtainable with advanced technological instruments.

“The Artemis II (Ultralink) is the best, but it is a heavy, expensive machine. The Zeiss Anterior Chamber OCT is more easily handled and can provide dynamic preoperative simulation of how the implant will perform in the eye” he said. The Zeiss device he referred to is a prototype that is not yet commercially available.

Camille Budo, MD, presented long-term results with rigid and foldable iris-fixated phakic IOLs. Both the Artisan and the Artiflex from Ophtec are “highly predictable, safe and effective,” he said. “More than 15 years of follow up with the Artisan lens demonstrated a perfect stability of results, and patients are highly satisfied.”

Dr. Budo pointed out that complications and lack of success with these lenses are usually due to improper technique, not to the lens itself.

Finally, Tobias Neuhann, MD, gave an overview of posterior chamber phakic IOLs. He spoke in favor of their use, although he acknowledged that problems with cataract after implantation have not yet been entirely overcome.

One advantage of these lenses, he said, is that they better complement other refractive procedures that do not involve the lens, such as LASIK.

In a final discussion, the panel members aired their views on the choice between RLE and phakic IOLs as the best procedure to perform in cases of high refractive errors.

Most surgeons agreed that phakic IOLs are preferable while the patient still has accommodation.

“Presbyopia is the border,” said Dr. Rosen. Other surgeons, including Dr. Budo, said that lens refractive procedures should be limited to patients with cataract.