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Wavefront technology effective for varied higher-order aberrations
Surgeons discussed indications for wavefront-guided and wavefront-optimized treatments and how wavefront-guided approaches can address complications after refractive surgery.
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Two wavefront ablation treatments offer good optical results for different sets of patients, according to two surgeons. In addition, a combined approach with topography- and wavefront-guided treatments may be the most effective way of addressing postoperative complications.
 Jack T. Holladay |
Wavefront-guided ablation and wavefront-optimized ablation offer distinct options for delivering LASIK to patients, largely based on the amount of higher-order aberrations present preoperatively, the experts said.
OSN Optics Section Editor Jack T. Holladay, MD, MSEE, FACS, and Theo Seiler, MD, PhD, discussed indications for wavefront-guided technology or wavefront-optimized technology for LASIK patients at Cataract and Refractive Surgery Subspecialty Day at the World Ophthalmology Congress.
Wavefront-guided ablation allows for a customized procedure, while wavefront-optimized ablation offers a standardized surgical option.
“The issues boil down to, in wavefront-optimized, the goal is not to reduce higher-order aberrations but maintain them. The treatment is based on sphere and cylinder,” Dr. Holladay said. “In wavefront-guided, the goal is clear, to try to reduce all higher-order aberrations, and the treatment is based on wavefront.”
 Marguerite B. McDonald |
Surgeons also discussed topography- and wavefront-guided approaches to treating aberrated corneas after refractive surgery in a debate at the meeting. OSN Refractive Surgery Section Member
Marguerite B. McDonald, MD, FACS, and Arthur Cheng, MRCS, FCOphth(HK), concluded that the existing methods are helpful, especially in concert, but that the technology does not yet offer the most effective treatment algorithm for postop corneal complications.
Wavefront-guided ablation
Dr. Holladay said he thinks wavefront-guided ablation offers the best optical results for most patients, who typically have medium- to high amounts of higher-order aberrations. The wavefront-guided technology is especially effective in patients with greater than 0.21 µm of higher-order aberrations, which is more than 73% of the population, he said.
He said studies have shown that lowering higher-order aberrations leads to better visual outcomes postop. Optical modeling analysis of refractive surgery has shown that the lower the higher-order aberrations in the optical system, the better the visual performance. Nearly all vision scientists and optical physicists agree that lowering higher-order aberrations assists in achieving the best visual results postop, he said.
“For me, it’s clear that we should try to reduce all higher-order aberrations to get the best ocular performance of the eye, not try to do one treatment to fit all,” Dr. Holladay said.
He and colleagues conducted a study of 102 eyes treated with IntraLase (Advanced Medical Optics) and wavefront-optimized (Wavelight) ablation and 109 eyes treated with IntraLase and wavefront-guided (AMO CustomVue) ablation. They found that results were significantly better for wavefront-guided over wavefront-optimized for all higher-order aberrations, most importantly spherical aberration, coma and trefoil.
There was a 30% better safety profile (either equal or better than preoperative higher-order aberrations) with wavefront-guided than wavefront-optimized, Dr. Holladay said.
“We also should note that those people with the lowest amount of higher-order aberrations had the least benefit. That simply means, if you don’t have higher-order aberrations, there’s not that much to treat when you do wavefront-guided,” Dr. Holladay said.
Wavefront-optimized ablation
Dr. Seiler said the primary goal of refractive surgery has always been to correct refractive error and not affect the eye’s optical performance. Altering the optical performance causes the visual cortex, which he called the “digital imaging part of our body,” to create “new hardware” in a process of neural restructuring. It alters vision, but not always to the benefit of the patient if the cortex does not adapt to the new optics. Selecting a wavefront technology is important based on this factor alone.
 Theo Seiler |
“The wavefront-optimized profile requires minimal neural processing postoperatively because we did not change anything in the optical performance,” Dr. Seiler said. “Eyes with poor performance, which means where they are greater than 0.3 µm, and high visual acuity may benefit from wavefront-guided treatment. That is the main indication. However, this subgroup makes only up to 5% in the normal refractive surgery practice.”
Wavefront-optimized profile corrects only for refractive error, Dr. Seiler said. The best candidates for wavefront-optimized ablation are patients with the appropriate profile for the technology, including those who do not have higher- order aberrations.
Dr. Seiler cited a comparative study that found that wavefront-guided was more effective than wavefront-optimized for numerous reasons, but only in patients with higher-order aberrations or previous wavefront error.
“At the highest, at the 0.3 µm and greater, the wavefront-guided treatment is doing a better job than the wavefront-optimized [in the study],” Dr. Seiler said. “However, in all the rest, at the 6-mm pupil, 0.3 µm wavefront-optimized is doing the same job, which, by the way, is 95% of that patient group, and there were no significant differences.”
Treating refractive complications
After LASIK surgery, regardless of which wavefront treatment is used, complications can occur. If this happens, either wavefront- or topography-guided approaches can be effective in treating such issues, according to Dr. Cheng and Dr. McDonald. They discussed the best approach to treating highly aberrated eyes at the WOC.
They agreed that the best way to decrease aberrations is to assess not only the cornea, but the entire optical system. In addition, they agreed that improvements in existing technology could assist treatment.
“Too often, our most desperate patients are ‘uncapturable’ with current technology,” Dr. McDonald said. “They need evaluation of the optics of the entire eye, not just the cornea.”
Dr. McDonald said the best approach could be a combined method that takes advantage of both wavefront- and topography-guided approaches. However, topography-guided customized ablations alone do not seem as effective as high-resolution wavefront-guided ablations in both normal and complicated cases because topography-guided ablations provide good results only in eyes with aberrations limited only to the cornea. But most eyes do not have perfect internal optics, she said.
“Only a small percentage is not capturable with new technology and is therefore in need of topography-driven ablations,” she said. “Wavefront-driven ablation provides accurate correction of the eye’s entire optical vision. This is especially important for treating our highly aberrated patients, including those few who accessed refractive technology many years ago and who now have lenticular changes as well as corneal aberrations.”
She outlined the ideal wavefront device for highly aberrated eyes as having high-resolution, high-dynamic range, a wide field of view that captures at least 8.5-mm pupils, auto-centration and dependence upon Fourier algorithms for generation of the ablation pattern. This aberrometer would be combined, in one unit, with an autorefractor, a kerotometer, a pupillometer and a topographer.
The prototype for this device exists, she said. AMO has designed the iDesign aberrometer, which has higher resolution, a higher dynamic range and increased data, as well as an autorefractor, a keratometer, a pupilometer, and a topographer.
“With the high resolution and high dynamic range of this new aberrometer, we get five times the current standard of 241 data points over a 7-mm pupil. The greater dynamic range allows us to measure –16 D to +12 D of sphere, up to 8 D of cylinder and up to 8 µm root mean square of higher-order aberrations. This provides a much more accurate representation of the wavefront,” she said.
Dr. Cheng said the topography-guided approach alone is a viable option when treating patients with corneal complications after LASIK.
“The thing about topography is we need to go back to basics,” Dr. Cheng said. “The golden rule in medicine is to treat the underlying cause, and if you look at a sequence of events of what actually happens in patients before LASIK procedures, they started with well-balanced optics. Patients will have myopia, hyperopia or astigmatism, but the patients with spectacles or contact lenses are generally quite happy with the quality of their vision. The lower-order aberrations are much more than higher-order aberrations.”
After LASIK, higher-order aberrations can increase significantly with flap or laser complications, Dr. Cheng said. Treatments for such complications should be focused on the cornea, which is where they typically occur. Scarring can also cause inconsistent and unreliable results.
The topography-guided approach does not have two limitations associated with the wavefront-guided approach: resolution and the relatively large deviation of the projected ray of light from the reference position in aberrated eyes, Dr. Cheng said. It also offers good corneal wavefront data.
However, topography-guided does not provide information about the intraocular structure, rendering it more effective when combined with wavefront, he said.
“Both wavefront and topography are complementary, and we have the best options for our patients with both,” he said.
For more information:
- Arthur Cheng, MRCS, FCOphth(HK), can be reached at Guy Hugh Chan Refractive Surgery Center, Hong Kong Sanatorium Hospital, 2 Village Road, Happy Valley, Hong Kong; 852-2572-0211; e-mail: drarthurcheng@gmail.com.
- Jack T. Holladay, MD, MSEE, FACS, is a clinical professor of ophthalmology at Baylor College of Medicine. He can be reached at Holladay LASIK Institute, Bellaire Triangle Building, 6802 Mapleridge, Suite 200, Bellaire, TX 77401; 713-668-7337; e-mail: holladay@docholladay.com.
- Marguerite B. McDonald, MD, FACS, can be reached at OCLI, 266 Merrick Road, Lynbrook, NY 11563; 504-232-3641; e-mail: margueritemcdmd@aol.com.
- Theo Seiler, MD, PhD, can be reached at Augenklinik Nordtrakt II, Frauenklinikstrasse 24, CH-8091 Zurich, Switzerland; 44-1-2554900; e-mail: info@iroc.ch.
- Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.