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Chicago—Conductive keratoplasty (CK) may benefit a subset of patients who are experiencing complications from LASIK or PRK by improving corneal optics and vision, according to the results of a small, interventional case series reported at the American Academy of Ophthalmology annual meeting.
CK, which has been FDA-approved for the correction of hyperopia and presbyopia, uses radiofrequency energy to shape the cornea biomechanically via thermal collagen shrinkage. "We have found that CK is also useful as a rescue procedure when we think that further excimer laser surgery or flap manipulation is contraindicated," said Peter S. Hersh, MD, FACS, clinical professor and director, Cornea and Refractive Surgery, Institute of Ophthalmology and Visual Science, University of Medicine & Dentistry of New Jersey-New Jersey Medical School, Newark.
Dr. Hersh provided results of a retrospective, noncomparative, interventional case series in which 25 CK procedures were performed on 16 eyes of 15 patients who had complications from initial LASIK or PRK surgeries and in whom further laser surgery was contraindicated. Six eyes had CK twice, one eye three times, and one eye four times.
In the 25 procedures, the average number of CK spots used was 15, with a range of 4 to 26. Thirteen patients were male, and two were female; the mean age was 50.6 years. The mean follow-up was 143.1 days from the last CK treatment.
Visual acuity results
Results showed that the mean distance UCVA improved from 20/68 preoperatively to 20/37 postoperatively, while mean near UCVA improved from 20/102 to 20/39. The mean manifest refractive spherical equivalent (MRSE) improved from +1.09 to –0.15 D. Nine eyes showed improved UCVA, three eyes had no change, and four eyes worsened. One eye lost six lines of vision due to overcorrection.
The average BSCVA was 20/23 both before and after surgery; most eyes did not change, although one eye improved by one line and three eyes worsened by one line.
"Looking at astigmatism, there was somewhat greater than 50% improvement," Dr. Hersh said. The mean refractive cylinder before CK was 1.92 D, which improved to 0.88 D afterward. Nine of 15 patients had improvement of more than 0.5 D and 6 of 15 had no change.
Using CK off-label to treat LASIK and PRK complications has multiple goals: treating hyperopia, astigmatism, and irregular astigmatism. "This takes advantage of the fact that decreasing the collagen lamellae with CK spots will focally steepen a flat hemi-meridian by 1 D for every 23-μm decrease in corneal chord length of the cornea," Dr. Hersh said.
He recommended a conservative treatment plan for each patient consisting of preoperative planning and intraoperative assessment with keratometry and other techniques.
"It is important to plan surgery based on refraction, topography, as well as keratometry," he added. He explained that the treatment effect after both PRK and LASIK is approximately double that in previously untreated corneas, which requires adjustment of the recommended nomogram based on surgically untreated eyes.
Dr. Hersh also noted that CK spot application could be titrated until the desired correction is achieved, and additional treatment spots could be applied at a later date if further correction is needed. The implications of repeated treatments in the same area are not yet known, although the safety profile in this study was excellent, he added.
Results of Dr. Hersh's study were published in the November 2005 issue of Ophthalmology.