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Advances in refractive accuracy gain traction through technologic evolutions


A look at how crosslinking applications, topography-guided ablations, along with the introduction of the Symfony lens, dominated refractive surgery this past year.

Take Home:

A look at how crosslinking applications, topography-guided ablations, along with the introduction of the Symfony lens, dominated refractive surgery this past year.


By Lynda Charters; Reviewed by Peter S. Hersh, MD, and Eric D. Donnenfeld, MD

The emphasis this year was on crosslinking applications, topography guided-ablations, and introduction of the Symfony lens.


This past year saw advances made and increased research performed to expand the use of crosslinking in refractive surgery.

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“Collagen crosslinking (CXL) is continuing to evolve. There has been continued progress with the technology and we hope for FDA approval of crosslinking for treating keratoconus and corneal ectasia in the near future,” said Peter Hersh, MD, professor of ophthalmology at Rutgers New Jersey Medical School, Newark, and Director, Cornea and Laser Eye Institute-Hersh Vision Group, Teaneck, NJ.

 A New Drug Application was resubmitted by Avedro, of which he is medical monitor, in September for using CXL to treat keratoconus and corneal ectasia. A potential FDA decision is expected in March 2015, according to Dr. Hersh.

In Europe, new work is being conducted in topography-guided crosslinking techniques for keratoconus. The topography-guided crosslinking device can pattern the ultraviolet dose to the topography of the cone in these patients. The device (Avedro KXL II unit) has an eye-tracking mechanism by which it locks onto the eye.

“Besides changing the 2-dimensional shape of the incoming ultraviolet light, the unit also can pattern the dosing, i.e., it can administer a greater dose to the steeper areas of the cone and topographically follow it out from there,” Dr. Hersh explained.


The next step for topography-guided crosslinking is the treatment of refractive errors.

“Early studies are suggesting that we can use crosslinking to change the corneal curvature to correct myopia, hyperopia, and astigmatism in normal eyes. The early results in European studies refractively and topographically are very encouraging. This technology may be particularly useful both in enhancement procedures after cataract surgery to correct small amounts of residual refractive errors and potentially as a general refractive surgery tool,” Dr. Hersh said.

Combining LASIK and crosslinking is another surgical approach.

“This may be of particular use in patients with hyperopia,” he said and explained that the postoperative refractive error may not be stable over time in hyperopia and may account for regression over time especially in patients with greater degrees of hyperopia.

“Biomechanically, there may be progressive flattening of the cornea postoperatively. Using adjunctive crosslinking, by stabilizing the long-term corneal architecture, may improve the surgical predictability and stability after hyperopic procedures,” Dr. Hersh said.

Clinical trials may begin in the United States in 2015.

Topographic Guided Ablation

Another technology that is widely used in Europe and eagerly awaited in the United States is topographic-guided excimer laser ablations.


“I believe that the approval of topographic ablations in the United States will have a profound effect on our ability to treat patients with highly irregular corneas such as those seen in patients with keratoconus and postoperatively after refractive procedures,” said Eric Donnenfeld, MD, clinical professor of ophthalmology, New York University Medical Center; trustee, Dartmouth Medical School, and founding partner, Ophthalmic Consultants of Long Island, Rockville Centre, NY.

The technology is so promising, Dr. Donnenfeld said, that many of his patients have traveled to Europe to take advantage of the availability of the technology.

“Had it not been for this technology, many of these patients may have had to undergo corneal transplantation.  Topographic laser ablations with the Wavelight laser (Alcon) have been approved by the FDA and are hopefully going to be available early in 2015,” he pointed out.

SMILE Technique

Also in Europe, regarding LASIK, the Small Incision Lenticular Extraction (SMILE) technique (Carl Zeiss Meditec) is receiving a great deal of attention.

A femtosecond laser is used to carve out a lenticule inside the stroma, which then is removed through a small incision.

“The results with this technique are also very encouraging. The predictability and results are good. The potential advantages may be that there is better retention of the corneal biomechanical properties postoperatively,” Dr. Hersh suggested.

IOL launch

Dr. Donnenfeld pointed out that a very exciting event for him in 2014 was the launch of the premium extended depth of focus IOL, Symfony Lens (Abbott Medical Optics). The lens currently is widely used in Europe and is now in FDA clinical trials in the United States.


“This IOL allows patients to see at all distances without glare and halos. The intermediate vision is excellent, (and) the near vision is not as good as that achieved with a multifocal IOL and there is some loss of contrast sensitivity. However, these disadvantages are counteracted by the fact that there are no visual disruptions such as those caused by conventional multifocal IOLs.  Hopefully, this lens will be available to surgeons in the US in the near future,” he commented.


Eric D. Donnenfeld, MD

E: ericdonnenfeld@gmail.com

Dr. Donnenfeld is a consultant to Alcon and Abbott Medical Optics.


Peter S. Hersh, MD, and

E: phersh@vision-institute.com

Dr. Hersh is the medical monitor of Avedro.

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