SEP 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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44 EW REFRACTIVE SURGERY September 2013 Refractive surgery for keratoconus by Maxine Lipner EyeWorld Senior Contributing Writer Considering options to normalize vision specify where the crosslinking light is distributed. T here was a time when refractive surgery for keratoconus patients was considered an absolute contraindication. Today, however, refractive techniques from lens exchange with phakic toric implants or toric lenses to the use of intracorneal ring segments are helping keratoconus patients to improve their vision. Even laser refractive surgery, which can be paired with collagen crosslinking or topographic-guided reshaping, is now being touted in some arenas. Historically, prior to surgical intervention, keratoconus patients were managed with toric or rigid gas permeable contact lenses to regularize their irregular astigmatism, according to Jimmy K. Lee, MD, director of refractive surgery, Montefiore Medical Center, University Hospital for Albert Einstein College of Medicine, Bronx, N.Y. ÒThere was nothing in between contact lens fitting, which is nonsurgical, and corneal transplantation for decades,Ó Dr. Lee said. That changed with the arrival of intracorneal ring segments (Addition Technology, Des Plaines, Ill.) about 10 years ago, which Dr. Lee describes as plastic segments embedded into the corneal stroma. ÒItÕs almost like having braces for the cornea, regularized to flatten the steepness of the cone and to regularize the cornea,Ó he said. With this technology, Dr. Lee noted, patients can have spectacular results, allowing them to get out of their contact lenses, or at least have better vision with their contact lenses. However, he added, one downside here is that predicting who will succeed with intracorneal ring segments isnÕt as well defined as with some other surgical techniques. One thing that has changed recently is the technique used to insert these ring segments, a method that Dr. Lee viewed as a bit crude. ÒThe surgeon would have to jam the circular blade through the tunnel, and you couldnÕt tell exactly where the depth was,Ó he said. Now, insertion of the ring segments can be done in tandem with the sophisticated femtosecond laser, he pointed out. ÒThe surgeon can tell the laser exactly the depth and dimensions of the tunnel Toric lens implantation Carl Zeiss Meditec AT Torbi in a keratonic eye with its shape improved by a single Ferrara intracorneal ring Source: Sheraz Daya, MD in the cornea to dictate where you want those segments to be,Ó he said. ÒThe accuracy of the intracorneal ring segments has been much greater in terms of placement.Ó This has translated into improved results. There has been a slew of data from five to seven years out that indicates long-term improvement of visual outcomes and in topographic status, Dr. Lee said. PRK for keratoconus Another refractive technology that is being used in conjunction with intracorneal ring segments is PRK. ÒIn the past, people have been very reluctant to touch or aggressively work on the cornea for keratoconic patients because the corneal tissue is unstable,Ó Dr. Lee said. The recent advent of crosslinking to strengthen the cornea and potentially halt keratoconus progression has helped to change this. ÒPeople have looked at combinations of crosslinking with these intracorneal ring segments or crosslinking plus or minus the PRK,Ó he said. ÒThe preliminary data seemed to show that it is very promising.Ó William B. Trattler, MD, director of cornea, Center for Excellence in Eye Care, Miami, likewise noted that crosslinking has had an impor- tant impact. ÒCrosslinking is a technology that stiffens the cornea and often improves corneal shape. Following crosslinking, patients are typically eligible for corneal reshaping procedures such as surface ablation,Ó Dr. Trattler said. In his practice, a small percentage of patients with keratoconus or post-LASIK ectasia who undergo crosslinking can end up with a relatively symmetrical corneal shape, allowing them to become eligible for surface ablation with technology available in the United States. This is because the excimer lasers in the U.S. provide symmetrical reshaping of the cornea. However, most patients still have significant asymmetry in their corneal shape, and their main option would be topography-guided surface ablation, which is available in Canada and Europe. Topographyguided surface ablation incorporates data from corneal topography into the treatment plan, allowing this technology to reshape corneas that are asymmetric, which is the typical case for keratoconus or post-LASIK ectasia patients. The goal, he explained, is to normalize the shape and improve the quality of vision. Meanwhile, Dr. Lee thinks that this sort of topographic approach may one day be extended to crosslinking with the ability to Toric lens implant surgery is another possibility of which practitioners are availing themselves, according to Sheraz Daya, MD, medical director, Centre for Sight, London. This can be done with phakic toric lenses such as the Artiflex (Ophtec, Groningen, the Netherlands), the Toric ICL (STAAR Surgical, Monrovia, California) or by refractive lens exchange using toric intraocular lenses. ÒIn patients who are older, if they have a whiff of a cataract or are around age 55, a refractive lens exchange with a toric implant is a good option,Ó Dr. Daya said. Indeed, in a study published in the December 2012 issue of the Journal of Refractive Surgery involving use of the AT Torbi 709 M toric lens (Carl Zeiss Meditec, Jena, Germany) in stable keratoconus patients undergoing refractive lens exchange or cataract surgery, investigators were able to offer patients a significant boost in unaided vision. ÒIn a nutshell, following the procedure, 75% had 20/40 uncorrected acuity or better, and with correction 83.3% had 20/40 vision or better,Ó Dr. Daya said. ÒTheir mean refractive astigmatism went down from 3 D to 0.7 D, which is quite significant.Ó Likewise, he added, keratoconus patients are typically myopic, and here after lens implantation the mean spherical equivalent went from Ð4.8 D to +0.30 D. However, Dr. Daya stressed, phakic IOLs or refractive lens exchange is not for all keratoconus patients. ÒThey have to have a history of good vision with their existing corneal shape,Ó he said. For those who canÕt see well enough with glasses but who are stable, it is still possible to use this method. ÒIf they canÕt see with glasses then we would consider putting in an intracorneal ring or two (preferably a small radius Ferrara) to alter the shape so that they can have better vision thatÕs respectable with glasses and then consider refractive lens exchange,Ó Dr. Daya said. When dealing with refractive lens exchange in keratoconus cases, Dr. Daya advises practitioners to gather as much background as they can. ÒItÕs like going into battle. You need as much information as possi-

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