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Wavefront technology will need to evolve to foster increased acceptance
The following topics were among those explored at the International Congress on Surface Ablation and SBK, held 1 day prior to ARVO.
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WESTON, Fla. — More sophisticated corneal and wavefront sensors represent the future of wavefront technology for laser vision correction and are essential to grow the uptake of that technology, Scott M. MacRae, MD, said here.
 Scott M. MacRae |
Speaking at the International Congress on Surface Ablation and SBK, conducted 1 day before the Association for Research in Vision and Ophthalmology meeting, Dr. MacRae said wavefront-guided ablation makes up 48% of the current U.S. market, but overall growth of the technology seems to have stagnated.
The lack of progress, he said, has to do with outdated wavefront sensors, slower wound healing with wavefront and the added time commitment necessary to perform procedures using this technology.
Ergonomically, Dr. MacRae said, use of wavefront technology can also be more difficult for surgeons. In addition, many clinicians view the outcomes with wavefront as only marginally better than those with conventional laser platforms and therefore cannot justify the expenditure.
“There are more sophisticated combinations coming down the line. … [With] the future of wavefront technology, we all kind of envisioned that topography would someday combine with whole-eye wavefront,” he said.
The combination of corneal topography and internal wavefront will enable physicians to account for aberrations in the cornea, lens and the entire eye. Furthermore, it will offer the integration of corneal shape data with whole-eye wavefront information, Dr. MacRae said.
Some of these items appeared originally as daily coverage from the meeting on OSNSuperSite.com. Look for more in-depth coverage of these and other topics in upcoming issues of Ocular Surgery News.
Understanding corneal biomechanics essential to refractive surgery safety
Patient-specific biomechanical measurement of the cornea will be a major component to helping surgeons perform safer and more predictable laser refractive surgery, according to a speaker.
William J. Dupps Jr., MD, PhD, discussed the nuances of clinical elastography and its implications for refractive surgery candidates.
“As we get better and better at measuring wavefront and corneal geometry, we are still going to run up against biological limitations and variabilities,” Dr. Dupps said. “So we want to learn as much as we can about individual patient properties.”
Dr. Dupps described an element-based whole-eye model that he and colleagues created, which they also presented in a poster at ARVO. The model was used to study how variations in corneal elasticity affect corneal optical response to IOP changes and myopic LASIK.
Using this model, the researchers determined that weak corneas displace maximally at the center, whereas stiff corneas display maximum displacement on the periphery.
“So in this case, we actually get steepening of the cornea that we’re not counting on if we treat the cornea as a piece of glass,” Dr. Dupps said.
Currently, the Ocular Response Analyzer (Reichert) is one of the best means that surgeons have at their disposal to measure the viscoelastic properties of the cornea. Other innovative approaches, including a device that sends seismic waves across corneal tissue to determine corneal stiffness, are advancing this area of study. The device, currently a prototype from PriaVision, is still a few years away from being commercially available, Dr. Dupps said.
“It is simple to use, but we do have some issues with contact artifact, and the cornea has to be fairly dry to use this tool. It has not gotten much traction clinically and has to be modified,” he said.
Aggressive approach needed for patients dissatisfied after IOL implantation
Understanding the best approaches to helping patients who are unhappy with their presbyopia-correcting IOLs after cataract surgery is essential to success, according to an ophthalmologist.
 Johnny L. Gayton |
Johnny L. Gayton, MD, discussed the challenges involved in tempering expectations of patients who said they want perfect or near-perfect vision after being implanted with a presbyopia-correcting IOL.
He also addressed the necessity of aggressively treating the most common complaints of patients postoperatively, namely dry eye, decreased vision due to cystoid macular edema and residual refractive error.
Dr. Gayton encouraged surgeons to recommend artificial tears, nutritional supplements and environmental changes — avoiding tobacco smoke or circulating air — to combat dry eye. He also suggested surface ablation as opposed to LASIK as a way to address residual refractive error after IOL implantation.
For patients with astigmatism who were poor candidates for limbal relaxing incisions, Dr. Gayton recommended toric IOLs. No matter which direction a surgeon chooses, the need for aggressive treatment and a straightforward approach is the key, he said.
“Get everybody on the same sheet of music, have everybody working together and accurately evaluate unhappy patients … [and] you’ll have a lot of happy premium lens patients, and you’ll be very successful,” Dr. Gayton said.
Femtosecond can be effective for enhancing LASIK results
Enhancements after LASIK may be effectively performed using the IntraLase femtosecond laser (Advanced Medical Optics) to create new flaps if certain guidelines are followed, according to a presenter.
William W. Culbertson, MD, advised precise planning in determining the practicality of using the femtosecond laser to enhance visual acuity in LASIK patients.
“I try to determine the location of the previous flap edge. Then I estimate the shape and diameter of the previous flap,” Dr. Culbertson said.
He uses a radial keratotomy marker to help him determine what his clearances are between the radial side cuts and to attempt to discern the position and width of the previous hinge.
“The most difficult thing is to estimate the depth of the previous flap,” he said.
The advantages of femtosecond laser-assisted enhancement after previous LASIK include the ability to create a vertical side cut, which reduces the risk of epithelial ingrowth, and predictability as far as diameter and depth are concerned, Dr. Culbertson said.
“I like to have these patients have the overnight recovery of vision that LASIK patients get, as compared to surface ablation. But you have to be very careful that you only use this technique in patients that it is suitable for,” he said.
Awareness of anatomy, environmental factors aids in treating postoperative dry eye
Environmental factors and isolation techniques can have dramatic effects on dry eye symptoms after refractive surgery, according to one ophthalmologist.
Richard W. Yee, MD, also spoke about the importance of understanding the anatomy of the ocular surface, particularly the blink response, when faced with dry eye complications after refractive procedures.
“When you think about every blink that happens, 11,000 times per day, if you just imagine that this ocular surface is not protected during that blink interval … then over time that cycle repeats itself and you have a compromised epithelium that is desiccated-prone,” Dr. Yee said. “And particularly during that early wound healing component, [when] the epithelium is not quite normal during that first month after surface ablation, you’ll get haze.”
Additionally, Dr. Yee stressed the importance of limiting potentially damaging environmental effects after surgery. These effects include high winds and extended computer usage. According to Dr. Yee, the majority of patients who return to him complaining of postoperative haze are those who stare at a computer monitor for long periods of time.
“So when you do your wavefront measurements, you have to make sure you’re taking this component of the environment out of the situation. Otherwise, that desiccated-prone epithelium will continue to desiccate and change. So you need to start thinking about isolation techniques for those who are predisposed,” he said.
Understanding patient goals key in enhancing presbyopic IOL outcomes
Understanding patient expectations, managing early physical complications and knowing when enhancement is appropriate are all important keys for the enhancement of presbyopic IOL outcomes with refractive surgery, Terrence P. O’Brien, MD, said.
 Terrence P. O’Brien |
Dr. O’Brien spoke of the importance of explaining to patients what results they should expect after undergoing a refractive procedure to enhance their IOLs.
It is also critical to know when to proceed with or delay an enhancement.
“One thing, when you are seeing patients [during] the postoperative period, realize that you don’t want to jump into any new treatment to try to help satisfy the old treatment too quickly because there may be a need to allow time for adaptation to the new optical system, and neuroadaptation does take significant time,” Dr. O’Brien said.
Managing a patient’s physical conditions is the first priority, according to Dr. O’Brien, who noted that before performing any enhancement the posterior capsule should be examined to make sure that no opacification has occurred. An optical coherence tomography image should also be taken to check for cystoid macular edema, and most importantly, the patient should be checked for cylinder and residual refractive error.
“Cylinder and residual refractive error [are] probably the leading cause, in my experience, of what is making these patients unhappy despite otherwise successful surgeries,” he said.
If patient goals are managed, physical issues are addressed and the timing of a surgical intervention is appropriate, Dr. O’Brien said the likelihood of a positive outcome occurring is greatly improved.
“These are some of the challenges we face in the refractive IOL era, and I think laser vision correction is a great tool. In particular, advanced surface ablation is preferred to try to prevent adding other problems with flap complications,” he said.
A note from the editors:
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