EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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36 EW FEATURE February 2011 Refractive challenges and innovations August 2012 Managing post-keratoplasty vision by Vanessa Caceres EyeWorld Contributing Writer AT A GLANCE • Refractive surgery after keratoplasty has a number of challenges, including astigmatism, stability of the refractive error, possible rejection, and difficulty cutting the flap • Refractive options include PRK with MMC, LASIK, phakic IOLs, and AK • Use of a femtosecond laser can assist with refractive treatment, particularly for laser-assisted AK • Future treatment options will include more frequent use of the laser, corneal crosslinking prior to surgery, and further development of phakic IOLs Seasoned surgeons share old and new refractive techniques R efractive surgery in post- keratoplasty patients has a host of challenges asso- ciated with it. However, with the right techniques and tools, it does not have to be as difficult as you might initially think. First, let's talk about the chal- lenges. "Cutting a flap is more challeng- ing because of the donor-host interface," said John Berdahl, M.D., Sioux Falls, S.D. "This may be one of the few situations where a microker- atome is preferred. Using a double pass with a femtosecond laser can also be performed." Astigmatism is also a challenge, said John Kanellopoulos, M.D., associate clinical professor of oph- thalmology, New York University, New York, and director of Laser Vision, GR Institute, Athens, Greece. "It appears that the astigmatism hurdle is persistent, even in an era where femtosecond lasers have held some promise to reduce post- penetrating keratoplasty [PK] astigmatism," he said. In some cases, particularly with keratoconus, high astigmatism can be associated with a partial wound dehiscence, increasing the curvature at the graft-host interface, Dr. Kanellopoulos said. "This challenge needs to be identified by the clini- cian because obviously refractive surgery in these specific cases would not necessarily help in visual rehabilitation and may even worsen the situation," he said. Use of anterior segment optical coherence tomography (OCT) or Scheimpflug imagery can help sur- geons better evaluate the graft-host interface, Dr. Kanellopoulos said. Rejection, re-epithelialization, and cataract formation inducing the refractive error are other challenges associated with a prior keratoplasty, Dr. Berdahl said. Surgical approaches Surgeons have a few options in their arsenal to treat post-keratoplasty patients. "The magic potion for us has been PRK with mitomycin-C [MMC]," said Richard L. Lindstrom, M.D., adjunct professor emeritus, ophthalmology depart- ment, University of Minnesota, Min- On the left, an intraoperative image on the LenSx. The red circle points to the 6 o'clock ink marking placed on the slit lamp just prior to surgery. This technology gives the option to rotate the AK axis until it meets the marking, avoiding cyclorotation errors. The Pentacam comparison on the right shows the pre-op high cylinder (left), the post-op cylinder following the femtosecond AKs (middle), and the difference (right). These topographies are from the same case shown on the left intraoperative image. It is noteworthy that the difference map is identical to the pre-op, underlining the accuracy of this approach This is an intraoperative LenSx image demonstrating the final adjustment of AK depth guided by the intraoperative OCT image obtained On the left, intraoperative image shows preparing two AK femtosecond incisions. On the right, the same case seen a few minutes later by slit lamp The precision of axis of the AKs performed in the top image are evaluated. The cobalt blue illuminated image on the left highlights the fluorescein-stained incision gutters. The slit is rotated in the middle image to match the axis of the incisions. On the right image, the exact axis is noted on the slit lamp goniometer to match the planned steep axis of 153 degrees Source (all): A. John Kanellopoulos, M.D.