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Er: YAG laser treatment for presbyopia introduced at ESCRS Winter meeting
At the Winter Refractive Surgery meeting of the European Society of Cataract and Refractive Surgeons, the focus was on technological advances.
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MONTE CARLO, Monaco — A treatment for presbyopia using Er:YAG laser energy is showing promise, according to an investigator speaking here.
Laser applications peripheral to the cornea decompress selected zones of the sclera with the aim of restoring scleral elasticity and recovering the biomechanical movements of accommodation, speakers said.
Results of the treatment were presented at the European Society of Cataract and Refractive Surgeons Winter Refractive Surgery meeting.
“LaserACE decompression decreases scleral rigidity and tissue restriction in three physiological critical junction areas, from approximately 2 mm behind the limbus to the ora serrata,” said Anne Marie Hipsley, PT, PSF, director of research and technology at ACE Vision, the company that makes the Er:YAG laser device.
“By releasing these points, the muscles can slide more freely underneath, and the accommodative function can be restored,” she said. “In addition, a series of other functional subsequent downstream effects are obtained, like improving the uveal flow, improving the nutritional standards of the eye and decreasing the IOP.”
Decompression is obtained by transscleral ablation performed in the four quadrants of the globe, approximately 0.5 mm behind the posterior limbus, using a 600-µm laser tip, she said.
“The surgeon performs a series of nine puncture spots in each quadrant, in a diamond pattern of approximately 4.5-mm-by-4.5 mm, according to the size of the eye. The ablation goes right down from the conjunctiva to the uvea, popping into the superciliary space,” said John Blaylock, MD, a clinical investigator.
Results at 4 years postoperative are encouraging, he added.
“We are restoring the accommodating response,” Dr. Blaylock said. “Patients maintain stable distance vision and have an average gain of 1.43 D of near vision, with a surprising range of 1 D to 8 D. More than 90% of patients don’t wear spectacles at all after the treatment.”
Post-LASIK ectasia risk factors difficult to identify
R. Doyle Stulting, MD, said that there are currently 114 reported cases of post-LASIK corneal ectasia in the literature with a number of identified risk factors: low preoperative pachymetry, low residual stromal thickness, low residual stromal bed, high myopia and form fruste keratoconus. However, a recent survey found that ectasia can develop after LASIK and more rarely after PRK even without recognized preoperative topographic abnormalities, Dr. Stulting said.
“We are currently investigating the potential causes of this phenomenon,” he said. “One of them may be the chronic trauma produced by eye rubbing. Other causes could be related to the flap, due to unrecognized deep microkeratome cuts and to unrecognized biomechanical and anatomical abnormalities. We understand form fruste keratoconus, but there may be more subtle underlying corneal changes which we are unable to detect with the current means of investigation,” Dr. Stulting said.
| Michael C. Knorz, MD, discusses technical aspects of presbyopia correction with the VISX Star S4 during a live surgery session. Image: Mullin DW, OSN |
Dr. Stulting concluded that, in the future, identifying more risk factors will allow surgeons to recognize more eyes at risk for ectasia. He admitted that at the present time, absolute cut offs for the safe performance of LASIK cannot be identified.
Iris registration yields better LASIK results than manual alignment
Iris registration software for wavefront-guided LASIK results in less cylinder and higher quality vision postoperatively than manual alignment of the eye, according to a multicenter study.
Gustavo Tamayo, MD, said a retro-spective multicenter study revealed significantly better postop visual acuity in eyes treated with iris registration than in a manual registration group.
The study compared 285 eyes treated with wavefront-guided ablation with iris registration and 280 eyes that were treated with standard wavefront-guided LASIK.
According to Dr. Tamayo, eyes treated with iris registration had 50% less postop cylinder than eyes treated with manual registration.
“The study results also showed a significant improvement in postop visual acuity,” Dr. Tamayo said.
Ultrathin cornea ‘remarkably stable’ after PTK retreatment
Thin corneas after phototherapeutic keratectomy — even those with residual stromal thickness below the typical safety range of 250 µm to 300 µm — showed a “remarkable refractive stability and are probably less likely to develop ectatic disease,” according to several speakers.
“This is probably due to the more even distribution of forces that the smoothing effect of phototherapeutic keratectomy (PTK) treatment induces on the cornea. An elastic band that is thinner, but regular, is likely to be stronger than an elastic band with a larger diameter but a narrowing of the lumen at some point,” Paolo Vinciguerra, MD, said. “PTK smoothes the surface and therefore gives this extra strength to even very thin corneas. The limit of thickness reduction in retreatment can therefore be extended beyond commonly accepted values.”
Ultraviolet light exposure of more than 30 seconds during excimer-laser PTK may also cause some degree of collagen cross-linking that could add extra strength to the corneal tissue, added Fabrizio Camesasca, MD.
“In conclusion,” Dr. Camesasca said, “in retreatment with PTK, very low residual corneal thickness is compatible with long-term stability, and penetrating keratoplasty can be avoided in most cases.”
Wavefront patterns may help identify subclinical keratoconus
Specific alterations in the patterns of some higher-order aberrations may help clinicians detect subclinical keratoconus in patients desiring refractive surgery, one speaker suggested. Certain patterns of vertical coma and vertical prism seem to be predictive of subclinical keratoconus, according to Thomas Kohnen, MD.
“We analyzed the wavefront data of the contralateral clinically healthy eyes of recently diagnosed monolateral keratoconus patients and compared these data with control normal eyes,” Dr. Kohnen said. “All the eyes of the first group showed significant differences in the pattern of corneal first-surface aberrations.”
These results are preliminary, Dr. Kohnen stressed, and more data should be collected to assess the feasibility of wavefront analysis to discriminate eyes with subclinical keratoconus from normal eyes. Should these results be confirmed, this method could be useful in detecting subclinical keratoconus when selecting candidates for refractive surgery, he said.
Wavefront-guided epi-LASIK results favorable at 1 year postop
Wavefront-guided epi-LASIK results at 1 year postoperative show the procedure to be safe and effective for the correction of myopia and myopic astigmatism, according to one surgeon.
“One year clinical results after epi-LASIK had excellent refractive and visual results, suggesting that it is a safe and efficient method for the correction of low to moderate myopia and myopic astigmatism,” Vikentia Katsanevaki, MD, said.
Her study included 234 eyes of 138 patients who underwent epi-LASIK for the correction of low to moderate myopia. She reported on 222 eyes that reached the 1-year follow-up point. The procedures were performed using the Norwood EyeCare Centurion SES epikeratome and the WaveLight Allegretto Wave excimer laser system.
Attempted correction ranged from –1.75 D to –7.5 D. One year following treatment, 80% of eyes were within 0.5 D of attempted correction; 90% had clear corneas and 10% had insignificant corneal haze, Dr. Katsanevaki said. Also at 1 year, 60% of eyes had a one-line gain in visual acuity.
Intrastromal corneal ring has immune benefit, surgeon finds
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Image: Mullin DW, OSN |
Implanting an intrastromal corneal ring in patients who undergo corneal transplant might reduce the chance of immune reaction, according to the surgeon who designed the ring. Jörg Krumeich, MD, offered his observations about several cases in which he implanted the Krumeich intrastromal corneal ring, produced and distributed by Human Optics.
“I made and implanted these rings to reduce astigmatism, stabilize the wound and improve healing,” Dr. Krumeich said. “Quite unexpectedly however, I observed that for some reasons these patients had fewer immune reactions. We therefore investigated this aspect and confirmed that the intrastromal corneal ring possesses immune-suppressing properties.”
Dr. Krumeich described a multicenter study that compared patients undergoing corneal transplants with or without implantation of the ring. Results in 179 patients implanted with the ring showed a significantly lower rate of immune reaction (1%) compared with patients who were not implanted with the ring (6%), Dr. Krumeich said.
He added that the device “seems to stop the recurrence of immune reaction” in patients with a previous history of one or more transplant failures.
“In nine cases that I reoperated after several failures, only one had a new rejection, while the remaining cases are showing no sign of immune reaction over a follow up of 1 to 8 years,” Dr. Krumeich said.
According to Dr. Krumeich and other speakers involved in the discussion, the immune-suppressive effect may be connected with the properties of the material of which the ring is made, an alloy of titanium, molybdenum and cobalt. A study to find the cause of the immune-suppressive effect will soon be started, Dr. Krumeich said.
“At this stage we only have the observation, and not yet the cause of the phenomenon,” he said.
Femtosecond laser technology may set new standard for PK, surgeons say
Femtosecond laser technology may change the way corneal transplants are performed, according to several surgeons.
Gerd Auffarth, MD, said he has performed several cases of penetrating keratoplasty (PK) using the Femtec femtosecond laser system. Indications for the transplants included bullous keratopathy after cataract surgery, granular corneal dystrophy, Fuchs’ endothelial dystrophy and keratoconus, Dr. Auffarth said.
“The incision quality is very high, the cut is very clear, and the procedure is safer because the eye remains a closed system for a long time during surgery,” he said.
Mark Tomalla, MD, said the femtosecond technology could be used not only in transparent corneal tissue, but also with extreme precision in scarred tissue.
“We performed several penetrating keratoplasties in patients with completely clouded corneas and in corneas with various degrees of scarring. The rate of ablation remains the same, as the femtosecond light penetrates the opaque cornea just as efficiently,” Dr. Tomalla said.
“The use of the femtosecond laser sets a completely new standard in the performance of PK,” he added.
Femtosecond laser creates superior LASIK flaps
The IntraLase femtosecond laser greatly improves precision and predictability of LASIK flaps, according to several surgeons. Bojan Pajic, MD, presented the results of a clinical trial on 345 eyes in which flaps where created with the IntraLase. The flap thickness was measured by confocal corneal laser-scanning microscopy. Target thickness was 120 µ in all treated eyes.
“The achieved flap thickness after the treatment was 120.28 µm, with a standard deviation of ±3.64 and a range between 114 µm and 126 µm. These results are highly statistically significant,” Dr. Pajic said.
The preoperative corneal thickness and corneal curvature had no influence on the final outcome. No case of cup perforation or other complication was reported.
“Because of this very accurate intrastromal cutting, the femtosecond laser offers several advantages over current techniques not only in LASIK but also in lamellar keratoplasty and Intacs implantation,” Dr. Pajic added.
Other studies, like one presented by Jorge L Alió, MD, PhD demonstrated that LASIK flaps performed with the femtosecond laser minimize the effects on corneal biomechanics of flap relocation.
“Biomechanical changes are even more predictable than the changes observed after LASEK,” Dr. Alió said.
DALK vs. PKP
In the same way that phacoemulsification has rapidly outclassed all other methods of crystalline lens removal, deep anterior lamellar keratoplasty (DALK) is progressively taking the place of penetrating keratoplasty (PKP) in most cases of corneal transplant, said Vincenzo Sarnicola, MD.
Over the years, a number of different DALK techniques have been developed, from the ‘dry’ approach, which requires particularly sensitive, experienced hands where there is a higher risk of perforation, to the various methods of air and visco dissection.
Dr. Sarnicola uses all methods, but prefers the “Big Bubble” procedure.
“It is safe and effective, and allows you to perform the excision very deep at Descemet’s level,” he said.
In case of rupture of Descemet’s membrane, conversion to PKP is easy, but no longer necessary, he added.
“I’m not converting any more to PKP. I place the graft over the Descemet’s, suture it, fill the anterior chamber with air and remove the fluid between Descemet’s and stroma. If these maneuvers are performed correctly, the Descemet’s membrane will reattach to the stroma also in cases you would never expect,” Dr. Sarnicola said.
Reducing the number of PKP procedures, he pointed out, means “avoiding the risk of so many severe intraoperative complications and the high rejection rate that this procedure entails.”
Corneal graft rejection
Corneal graft rejection rates can be significantly lowered even in high-risk patients if a series of preoperative, intraoperative and postoperative measures are taken, according to Harminder Dua, MD.
“Preoperatively, the eye should be quieted with glue and steroids, and blood vessels occluded with argon laser or fine needle diathermy,” Dr. Dua said. The transplant should then be performed within a maximum of 3 months, he recommended. Intraoperatively, graft sizing is crucial.
“The general rule is the smaller the graft the better. Interrupted sutures are better, as you can manage them more easily in case of localized rupture. Intravenous prednisolone is then injected,” he said. Amniotic membrane patching, although not demonstrated, seems to lower the chance of rejection. “Postoperatively, monitor IOP, use topical steroids for 18 months to 2 years and Acyclovir for at least 1 year. All of this, in addition to a specific protocol of immunosuppression, significantly improves graft survival in patients at high risk of rejection,” Dr. Dua pointed out.
Regrafting alternative
The Boston Keratoprosthesis (K-Pro) is a valid alternative to regrafting, according to Sadeer Hannush, MD, who showed the audience the latest improvements of this implant.
“It has been proved that patients who receive second or third transplant have a very high chance of graft rejection in the short period. Therefore, rather than embarking in an endless series of predictable failures, we should start considering placing a keratoprosthesis after the second graft has been rejected in spite of immune suppression therapy,” he said.
Over the years, the K-Pro has undergone “enormous improvement,” he pointed out.
“We are now using a healthy donor corneal button sandwiched between two plates. Fenestrations in the posterior plate allow nutrition of the cornea, decreasing the chance of corneal melt,” Dr. Hannush said.
A group of 17 centers have implanted 141 type-1 K-Pros. After 33 months, the retention rate is near 100%, and all patients have achieved their macular visual potential. Dr. Hannush noted that the use of this prosthesis necessarily require lifelong treatment with antibiotics.
After more than 30 years, the osteo-odonto keratoprosthesis is still a viable method of recovering useful vision in patients with severe ocular surface diseases.
Wavefront presbyopia-correcting profile developed
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Image: Mullin DW, OSN |
A laser ablation profile based on the modification of the polynomium Z 4.0 (spherical aberration) effectively addresses presbyopia with no loss in quantity and quality of vision and no induced diffractive phenomena. This treatment creates a new aspheric corneal profile that increases the depth of focus and recovers about 2 D of near acuity in the presbyopic eye.
“The key point is spherical aberration,” said Franco Bartoli, MD, who developed this method some years ago. In previous studies he demonstrated that spherical aberration is zero or slightly negative in the non-accommodating eye, while during accommodation the center of the anterior surface of the lens vaults forward and induces positive spherical aberration. Dynamic wavefront analysis was able to quantify both accommodation and induced spherical aberration.
As an obvious consequence, it was found that in presbyopic eyes, the loss of accommodation produces a loss of the ability to induce spherical aberration.
Based on these discoveries, Dr. Bartoli, in collaboration with Carl Zeiss Meditec, developed new software for wavefront-guided ablation. The treatment was aimed at inducing a certain amount of spherical aberration to compensate for the loss of accommodation in presbyopic eyes. This software was first used with the WASCA aberrometer and Mel 70 excimer laser, and has now been modified and updated to the CRS Master and the Mel 80. A study involving several centers in Europe has produced positive results in 339 presbyopic eyes treated with this method.
“We have now developed a software that simulates the corneal treatment on contact lenses. It will soon be possible to have this done for every single patient, who will have the chance to try the visual outcomes of corneal surgery for a few days before the operation,” Dr. Bartoli pointed out.
LASIK retreatment
Surface treatment after LASIK is still a controversial option, as emerged from a discussion during the final session of the meeting. Dan Epstein, MD, said there is only one peer-reviewed publication on PRK after LASIK, showing that a large percentage of eyes developed severe haze and regression 6 months after the treatment.
“Other anecdotal reports reach variable conclusions,” he said.
He noted, however, that epithelial thickness after LASIK is so unpredictable, and the standard deviation of microkeratome cuts so high that the chances of perforating the flap when doing PRK are every time “much greater than we would expect.”
His personal take-home message to the audience was “please, stay away from doing PRK after LASIK.”
While some of the colleagues agreed, others said they had good results with PRK after LASIK for many years, thanks also to the use of mitomycin C.
The use of mitomycin C was also a topic for discussion, and Emanuel Rosen, FRCOphth, said “although the immediate benefits of the medication are clear, we still don’t know the long term effects of it.”
For Your Information:
- David W. Mullin is Managing Editor of OSN Europe/Asia-Pacific Edition.
- Michela Cimberle is an OSN Correspondent based in Treviso, Italy, who covers all aspects of ophthalmology. She focuses geographically on Europe.