Thermokeratoplasty with cross-linking may be useful for treating keratoconus

The microwave energy flattens the cornea, and corneal collagen cross-linking maintains the ideal corneal shape, surgeon says.

Gustavo E. Tamayo

A nonincisional microwave-based treatment has yielded positive results in treating keratoconus and corneal ectasia, according to a proponent of the technology.

The Keraflex system (Avedro) involves the application of microwave energy to flatten the cornea. Simultaneous or delayed corneal collagen cross-linking reinforces corneal shape changes and prevents regression to the baseline corneal profile.

Combined thermokeratoplasty and corneal cross-linking may become the standard of care by virtue of being noninvasive, stable and reliable, Gustavo E. Tamayo, MD, OSN Latin America Edition Board Member, said in an email interview.

“This treatment will become one of the first options to treat keratoconus due to the fact it is not a procedure to resect tissue,” Dr. Tamayo said. “We need to demonstrate that the treatment is stable and no regression is seen over time, but the fact that we add cross-linking to the treatment makes the stabilization a very good possibility.”

Keraflex also has potential for treating myopia, especially in high-risk cases, Dr. Tamayo said.

“The Keraflex procedure will be another treatment option for myopia in the future, particularly for weak corneas or those prone to developing ectasia,” Dr. Tamayo said. “By nature, the Keraflex procedure does not jeopardize the biomechanics of the cornea.”

The Keraflex system is not available in the United States. It is being distributed in Europe, North and South America, Asia, Australia and New Zealand.

The Keraflex procedure comprises two steps: annular application of controlled microwave energy and collagen cross-linking. A suction ring is placed on the eye and a microwave application device is applied.

Keratoconus

To date, the Keraflex procedure has produced strong visual results and a high safety profile in treating severe keratoconus, Dr. Tamayo said.

“Because all cases were ready for transplant, all of them improved several lines of [uncorrected visual acuity and best corrected visual acuity], and therefore the procedure is very safe and effective in severe keratoconus,” he said.

Dr. Tamayo has used Keraflex to treat five cases of severe keratoconus since August 2011 but no cases of non-keratoconic myopia.

“The results were impressive, to say the least,” Dr. Tamayo said. “All cases were counting fingers before the treatment, with corneal curvatures more than 57 D. After the treatment, all five are 20/150 or better [uncorrected] and all curvatures are lower than 52 D. Remember, all cases were eyes ready for keratoplasty.”

Dr. Tamayo said Keraflex with cross-linking may be tailored to the requirements of individual patients.

“With more cases treated, a nomogram can be developed to get the desired corneal curvature for every case in terms of application time for the microwave and the cross-linking, as well as the exact time when the cross-linking should be applied after the treatment is performed,” he said.

Visual, topographic outcomes

During a symposium sponsored by Avedro during the American Academy of Ophthalmology meeting in Orlando, Fla., Dr. Tamayo outlined strong visual and topographic results obtained with the Keraflex procedure.

A patient with preoperative uncorrected visual acuity of counting fingers and Snellen best corrected visual acuity of 20/200 had postoperative uncorrected visual acuity of 20/100.

A second patient with preoperative UCVA of counting fingers and BCVA of 20/150 improved after surgery to UCVA of 20/150 and BCVA of 20/80.

A third patient with preoperative UCVA of 20/200 and BCVA of 20/50 had postoperative UCVA of 20/150 and BCVA of 20/50.

A fourth patient with mean preoperative UCVA of counting fingers and mean BCVA of 20/80 had postoperative UCVA of 20/200 and BCVA of 20/50, Dr. Tamayo said.

Topographic data from another case showed preoperative root-mean-square total higher-order aberrations of 1.686 µm, with 1.005 µm coma, 0.963 µm spherical aberration and 0.626 µm trefoil. The patient also had 5.463 D of astigmatism.

Postoperatively, the patient had root-mean-square total higher-order aberrations of 1.475 µm, with 1.108 µm coma, 0.133 µm spherical aberration and 0.808 µm trefoil. Postoperative astigmatism was 3.996 D.

The patient also had significantly diminished simulated keratometry values, corneal curvature and corneal elevation, Dr. Tamayo said. – by Matt Hasson

• Gustavo E. Tamayo, MD, can be reached at Bogotá Laser Refractive Institute, Calle 113 #7-45 Torre B, Suite 906, Bogotá, Colombia; 57-1-629-2860; fax: 57-1-629-2905; email: gtvotmy@telecorp.net.
• Disclosure: Dr. Tamayo is a consultant for Abbott Medical Optics, Presbia and Eyegenics.