When to perform AK

Arcuate keratotomy (AK) marker (60 degrees with gunsight); AK avoids coupling and therefore does not affect the spherical equivalent Source: David Jory, M.D.

Arcuate keratotomy (AK) could be a blessing for patients who continue to have astigmatism after LASIK. In one recent case study, a LASIK patient who underwent incorrect axis treatment subsequently received astigmatic keratotomy for astigmatic correction and benefitted dramatically. “For refractive surgeons familiar with AK, this tissue neutral surgical approach may be a first choice option to improve uncorrected visual acuity and reduce unwanted and disabling optical effects secondary to high astigmatism,” according to lead study author Roberto Pineda, M.D., Department of Cornea, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. The study was published online in October 2009 in Cornea. Dr. Pineda noted this is the first reported case of AK after LASIK, and he seemed pleased with the results. “Visual recovery is rapid and refractive changes are stable,” he reported.
In detail

The case involved a 52-year-old woman who initially underwent LASIK for myopic astigmatism in the left eye and symmetric bowtie on topography. “She was inadvertently treated for –1.50 –2.50 × 70 degrees, not axis 170,” Dr. Pineda reported. “On the first postoperative day, the uncorrected visual acuity was 20/400 and the best-corrected visual acuity was 20/20. Additionally, the patient experienced ghosting and blurring of distant objects. The refractive error was +2.25 –5.00 × 170 degrees.”
After three months, the refractive error stabilized to +1.75 –4.00 × 169 degrees. “After careful consideration, she proceeded with AK first as a tissue neutral procedure and to evaluate other options in the future,” Dr. Pineda reported.
The procedure included a pair of 60-degree arcuate incisions with a blade depth of 95% of the intraoperative pachymetry reading. These were performed at the 7-mm optical zone, centered on a 70-degree axis. “On the first postoperative day, the uncorrected visual acuity was 20/25, and there was a reduction of ghosting and visual blur,” Dr. Pineda reported. “The refractive error was +0.5 –1.0 × 165 degrees.”
The good results held, and at one year, she still had 20/25 uncorrected visual acuity. “Topography also showed the reduction of the astigmatism with residual with-the-rule astigmatism,” Dr. Pineda noted. In other words, AK was performed with much success here. “The majority of the residual astigmatism could be successfully corrected with the arcuate keratotomy itself dramatically improving the uncorrected visual acuity and maintaining the best spectacle-corrected visual acuity,” Dr. Pineda said. Of course, AK is not the only astigmatism-correcting option. Another procedure could have been used in this case, perhaps also with compelling results. “Another treatment option for this patient could have been photorefractive keratectomy on top of the LASIK flap,” Dr. Pineda noted. “It has the advantage of excimer laser precision and does not further compromise the residual bed thickness.”
Given that there is no standard treatment option for surgically correcting astigmatism, Dr. Pineda touched on some other possibilities, ruling some out while considering others. “[Conductive keratoplasty] has not been studied adequately as an option for myopic astigmatism and it may not be a suitable procedure,” Dr. Pineda wrote. Toric phakic IOLs could be a better option. “Recently, successful correction of high astigmatism as a complication of LASIK flap decentration was reported using toric phakic intraocular lenses,” Dr. Pineda said. AK itself is by no means perfect. “The mean reduction obtained with this procedure has been reported to be approximately 3.00 D and it is difficult to correct higher degrees with this procedure alone,” Dr. Pineda noted. “The risk of epithelial ingrowth also increases when AK is performed through a LASIK flap.”
On the other hand, if it fails, there should be no impact on best spectacle-corrected visual acuity, and other procedures may be tried, he reported. Christopher J. Rapuano, M.D., professor of ophthalmology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, and co-director, Cornea Service, Wills Eye Institute, Philadelphia, suggested that AK could be a good option after LASIK, but it depends on how much astigmatism is present. “If it’s pure astigmatism and the spherical equivalent is basically plano, then AK can be used,” Dr. Rapuano said. “If there’s also a lot of hyperopia or myopia associated with it, then a simple AK is not going to be enough.”
Dr. Rapuano said he would have concerns about performing AK in relation to the LASIK flap because it could upset it. “Performing it outside the edge of the LASIK flap is going to be safer than inside,” he said. “It may be OK, especially if you’re not too aggressive and perform it outside the LASIK flap. AK after IntraLase [Abbott Medical Optics, Santa Ana, Calif.] may be safer, but this has yet to be determined.”
Alternatives include performing repeat LASIK or surface ablation on top of the LASIK flap, he said.

Editors’ note: Dr. Pineda has no financial interests related to this study. Dr. Rapuano has no financial interests related to his comments.

Contact information

Pineda: roberto_pineda@meei.harvard.edu
Rapuano: 215-928-3180, cjrapuano@willseye.org