Avedro Keraflex: Microwaves for Reshaping the Cornea
Posted Feb 26 2010 2:35pm
Last May, I read news that came out of the 2009 ASCRS Meeting about how John Marshall and his colleagues in London were using microwave energy to reshape the cornea. It turned out that the technology came from a new company, Avedro, started by an old friend David Muller, the former CEO of Summit Technology. (The May writeup was contained in my Journal posting entitled: The Rebirth of Thermal Keratoplasty )
As promised, I have been following developments announced by the company and would like to bring you up to date about what they are doing.
As reported in this news release from Avedro, in December, during the 5th International Congress of Corneal Cross Linking for Keratoconus held in Leipzig, Germany, the company announced that it had initiated a Keraflex KXL Clinical Trial for treating keratoconus.
Editors Note: For those of you unfamiliar with that term, it is a cone-shaped protrusion and/or distortion of the central cornea that typically begins in the teenage years or early 20s and afflicts millions of people around the world. It is a progressive condition, that sometimes can be treated/controlled with hard contact lenses, but also can lead to the need for corneal transplantation for some patients.
Initial treatment results from the first group of Keraflex KXL patients, treated by Prof. Omer Faruk Yilmaz, MD of Beyoglu Eye Research and Training Hospital in Istanbul, Turkey, were presented in Leipzig by Prof. John Marshall, PhD, FRCPath, FRCOphthal (Hon), Emeritus Professor of Ophthalmology King's College London; and Dr. Peter Hersh, Professor of Ophthalmology UMDNJ - New Jersey Medical School and Director, Cornea and Laser Eye Institute - CLEI Center for Keratoconus in New Jersey.
In their presentations, Drs. Marshall and Hersh reported significant corneal flattening and improved corneal smoothness and regularity in all keratoconus subjects.
Dr. Hersh remarked, "Keraflex KXL is a promising new technology to decrease the protruding cone of keratoconus and make the irregular cornea smoother. Our early experience shows improvements in the keratoconic cornea that we have not seen with past technologies. This should help improve vision in patients with keratoconus, a cornea problem that is difficult to correct, as well as improve contact lens wear and vision with glasses. We hope that Keraflex can help avoid cornea transplants in many patients who otherwise might have no other alternative."
Dr. Marshall added, "I am extremely excited by Avedro's technology. It has particularly important consequences for the treatment of keratoconus whereby not only can it flatten the cornea, it also has the potential for correcting associated refractive errors without any biomechanical weakening and most unexpectedly, it strengthens the cornea and should prevent or delay any further corneal distortion."
Commenting on the presentations, David Muller, PhD, President and CEO of Avedro said, "It was clear that the discerning conference attendees universally welcomed the new data and were equally excited about the promise of the technology for their keratoconus patients who are currently faced with limited refractive treatment options. While Keraflex KXL has been under clinical study for the correction of myopia since the beginning of the year, the data presented in Leipzig is from a separate keratoconus study that began in November. The visually debilitating nature of keratoconus and the lack of refractive correction alternatives for keratoconus patients have prompted the company to accelerate its efforts to make Keraflex KXL commercially available for treating keratoconus patients in Europe as soon as the company receives its CE Mark."
More recently, as reported by Ophthalmology Times Europe on February 17, 2010 (and reprinted with permission of the editor of OT Europe), John Marshall and David Muller, along with Margerite McDonald, MD provided an update on their clinical progress.
Procedure reshapes cornea using microwave technology
A procedure that uses microwaves to alter corneal refraction may be an alternative to LASIK in myopia patients.
A refractive procedure (Keraflex, Avedro) fifteen years in the making uses microwave technology to reshape the cornea. It is currently in initial clinical testing. The technique changes the corneal refraction without removing stromal tissue or creating a flap. The procedure may be promising for patients with low and moderate levels of myopia who are squeamish about undergoing a conventional refractive surgery procedure in which corneal tissue is removed.
The procedure focuses microwave energy that is applied in an annular pattern to the corneal mid-periphery. “Alteration of the collagen in this region of the cornea applies tensile stress to the central cornea, causing flattening and the reduction or elimination of myopia. The procedure is anticipated to broaden the surgical vision correction market by appealing to people with less severe myopia than those who typically opt for laser vision correction procedures such as LASIK,” according to David Muller, PhD, president and chief executive officer of Avedro.
Speaking to the potential market for this type of procedure, Dr Muller said that a survey about refractive vision correction for myopia polled 2,400 consumers for specific reasons for not undergoing a refractive procedure. The top three factors cited by this group for not undergoing LASIK were 66% who were: “Nervous about poor results,” 54% who did not like the idea of “cutting the eye,” and 45% cited just plain “fear.”
The focused energy used in the procedure, delivered in one pulse of less than 100μs, causes collagen shrinkage and corneal flattening , which does not permanently alter the cornea or require removal of corneal tissue. The procedure is performed under the control of a microprocessor during application of electrodes to the eye. The electrodes, which can vary in thickness and the degree by which they are separated on the corneal surface, are applied to the eye outside of the visual axis.
A coolant is delivered in micropulses to control the temperature of the cornea, after which the microwave energy is applied to the cooled corneal area. The collagen in the area treated with microwave energy shrinks, which results in predictable flattening of the central cornea.
“By balancing the microwave field intensity and cooling period, the peak temperature generated can be driven to predetermined depths within the corneal stroma, causing changes in the collagen without damage to the corneal epithelium,” said Dr John Marshall, FRCPath, FRCOphth (Hon), the Frost Professor of Ophthalmology and chairman, Department of Ophthalmology, Kings College, St Thomas’ Hospital, London and lead scientific advisor.
“Such modifications to collagen fibrils result in changes in the refractive properties of the cornea,” he added. “By varying the depth and diameter of the induced collagen variations, controlled refractive changes may be introduced of different signs and magnitude. Thus, refractive errors can be corrected without removing any tissue. In vitro experiments have been conducted in both animal and human eyes using a model system capable of preserving wound healing for 4 to 6 weeks postexposure.”
Histopathologic studies indicate that the induced treatment changes consist of altered collagen fibrils with modifications in the local geometry of the lamellae, Dr Marshall said. These areas of change undergo rapid wound healing in which the matrix assumes a normal appearance and the collagen retains its newly induced curvature. A transient superficial haze apparent immediately after exposure is lost within minutes after treatment. By varying the administered parameters a systematic change in refraction was achieved, he said.
Dr Marguerite McDonald, a member of the medical advisory board and clinical associate professor of ophthalmology, Department of Ophthalmology, New York University, New York and adjunct clinical professor of ophthalmology, Tulane University, New Orleans, commented on the procedure. “It is early in the game vis-a-vis the clinical trials which are being conducted outside the United States. Nevertheless, the results are encouraging,” she said. US clinical trials were expected to begin shortly.