A Look to the Future

Where will the next paradigm shift occur in refractive surgery?

The last 20 years in ophthalmology have been highlighted by an astounding array of advances, particularly in refractive surgery: Incisional surgery gave way to laser surgery. Surface ablation was supplanted by LASIK, and now, more than half of U.S. refractive surgeons are performing all-laser LASIK. These advances translate to significant improvements in outcomes.

“Thanks to continuing improvements in algorithms, our ability to accurately correct refractive errors has improved considerably,” says Richard L. Lindstrom, MD, founder and attending surgeon of Minnesota Eye Consultants. “We can now program sphere and cylinder corrections in hundredths of a diopter, which is remarkable. The percentage of patients who achieve 20/20 visual acuity with one treatment is now in the 90% range, while enhancement rates have declined to just 2% to 3%.”

The next immediate challenge, Dr. Lindstrom says, is tackling higher-order aberrations (HOAs). “We're in an era of treating HOAs through Wavefront Optimized^® and wavefront-guided treatments, and we're beginning to correct coma, trefoil, tetrafoil and pentafoil. Although we're getting better at this, there's a good deal of room for improvement by way of enhancing our algorithms.”

Seeking the Ideal Ablation Profile

Wavefront Optimized^® and wavefront-guided ablation profiles are well-established in most practices, and studies of topography-guided ablations are ongoing, with investigators suggesting there are potential applications for highly aberrated eyes, including irregular astigmatism and keratoconus.¹

Theo Seiler, MD, PhD, and colleagues at the Institute for Refractive and Ophthalmologic Surgery in Zurich, Switzerland, have developed an algorithm to create individualized eye models.² Studies of this algorithm, sometimes called optical ray tracing, are under way at three centers in Europe.

“Dr. Seiler is factoring in topography, aberrometry and anterior chamber depth to create a more personalized ablation profile, which he feels will create the best ablation patterns,” explains Dr. Brint.

Shifting Paradigm Introduces New Frontier

According to Karl G. Stonecipher, MD, Greensboro, N.C., refractive surgery is poised for another paradigm shift. “We're looking at our patients' lifetime vision needs,” he says, “from the 21-year-old to the 85-year-old, with the goal of spectacle independence at all distances with a refractive procedure that is safe and predictable.”

Dr. Lindstrom concurs, noting lens-based refractive surgery will expand the range of correctable refractive errors in the pre-presbyopic population. “For myopia, we have a posterior chamber and an iris-supported anterior chamber phakic IOL, and pending FDA approval, an angle-supported anterior chamber phakic IOL. For hyperopia, we use both lasers and lenses for this type of treatment. If we use a lens, we will use a multifocal, accomodating IOL, or in some cases, an aspheric IOL, depending on the patient's visual goals.

“We're seeing good, reproducible refractive outcomes and improved safety profiles with implants,” Dr. Lindstrom says. “I believe within a decade or two, we'll have lens implants—perhaps adjustable IOLs to correct residual refractive error—that can more or less duplicate the kind of vision a 30-year-old emmetropic patient with 4, 5, 6 diopters of accommodative amplitude enjoys, which is as close to the best vision the human eye can generate. The only limitation will be the health of the retina. That is exciting.”

The new frontier for LASIK will be presbyopia correction. “We may recommend laser vision correction for our 20-year-old patients,” Dr. Stonecipher says, “but if a 40- to 50-year-old presents to us now, our presbyopic options are limited.”

That situation is changing, according to Dr. Lindstrom. “A tremendous amount of money is being invested in the treatment of presbyopia with the excimer laser and the femtosecond laser, alone or in combination with one or another corneal inlay,” he says. “We'll see these and other approaches for treating presbyopia come to fruition soon to address the needs of the 78 million baby boomers who are now presbyopic.”

Femto-cataract Surgery on the Horizon

Both Drs. Lindstrom and Stonecipher are eagerly awaiting a new femtosecond laser designed for use in cataract surgery. The first of these new lasers was installed in the United States in February 2010 in the office of Dr. Slade in Houston. According to Dr. Slade, the laser offers safety and accuracy advantages and has a high rate of patient acceptance.

Dr. Lindstrom notes, “Over the last 15 years or so, we have applied the femtosecond laser to corneal refractive surgery. Now, we'll be able to apply the femtosecond laser, which is an exquisite scalpel, to lens-based refractive surgery. I believe the femtosecond laser applied to cataract surgery will make it easier to do, safer and more reproducible. It will make a perfect capsulorhexis, and it will soften the nucleus. It will make lens-based refractive surgery much more successful with regard to safety and efficacy.”

Dr. Stonecipher agrees that the femtosecond laser will bring a new level of safety to cataract surgery. “The incisions will be where they should be,” he says. “The capsulorhexis will be well-defined without the potential complications of tears and abnormalities, and we'll be able to evacuate the lens more easily.

Reduced energy times also will improve safety. In addition, outcomes will improve because we'll be able to get a better effective lens position, and we'll be better able to predict IOL power.”

Breaking Down Barriers in Vision Correction

The surgeons we interviewed agree that laser-based refractive surgery of the cornea with the femtosecond and the excimer laser may soon give way to laser-based, lens-based refractive surgery. “Lasers will be combined with a variety of implants in the cornea and inside the eye that can basically correct any refractive errors,” Dr. Lindstrom says. “We're moving into an era when we can correct any refractive error at any age, then refine the outcomes with enhancements as needed.”