Eyeworld

While many ophthalmologists credit LASIK's popularity to the precision provided by the excimer laser, an alteration to the procedure allows surgeons to use only the femtosecond laser T he VisuMax femtosecond laser (Carl Zeiss Meditec, Dublin, Calif.) is being used to perform LASIK without the use of an excimer laser for ablation. Such a procedure offers several potential benefits, and surgeons are reporting good results so far. But some ophthalmologists are cautious about eliminating the excimer laser from the procedure because it offers more precision than the femtosec- ond laser does. "The reason LASIK is so popular is because the excimer laser is so ac- curate that every pulse treats 0.25 microns," said Ming Wang, M.D., Ph.D., clinical associate professor, University of Tennessee, Nashville. "Conversely, a femtosecond laser pulse treats 1-2 microns. Because the procedure eliminates the excimer laser, surgeons will be sacrificing the biggest feather in LASIK's cap—its high accuracy attributed to the ex- cimer laser." Excimer-less LASIK Donald T.H. Tan, F.R.C.Ophth., di- rector, Singapore National Eye Cen- tre, said he started performing ReLEx (refractive lens exchange) surgery in March 2010 and has performed 72 cases so far. ReLEx essentially in- volves using the femtosecond laser to incise an instrastromal refractive lenticule that is then removed. There are currently two forms of ReLEx surgery: FLEx (femtosecond lenticule extraction) and SMILE (small incision lenticule extraction). Dr. Tan said FLEx mimics LASIK in that a full flap is opened and the un- derlying lenticule is simply peeled away from the stromal bed. SMILE is a flapless procedure whereby a full flap is not performed but the lentic- ule is extracted through a superior pocket incision. Additionally, a vari- ant to SMILE is pseudoSMILE, which is a FLEx laser procedure but the flap is not fully opened, and the lentic- ule is extracted only from a superior pocket incision, like the SMILE pro- cedure. Dr. Tan said he and his col- leagues started with FLEx and per- formed 40 cases and have now switched to pseudoSMILE and done 32 cases. "To date, our clinical data sug- gests that both FLEx and pseudo- SMILE are highly effective and safe treatments and compare very well with conventional femtosecond LASIK procedures," Dr. Tan said. Advantages and drawbacks "There are certainly some potential advantages with ReLEx as compared to LASIK," Dr. Tan stated. In the SMILE and pseudoSMILE procedures, a major advantage is EW REFRACTIVE SURGERY February 2011 53 September 2011 by David Laber EyeWorld Contributing Editor Femtosecond laser-only refractive surgery could reduce costs, but with compromises continued on page 54 that no corneal flap is lifted; the cornea is therefore tectonically stronger and more stable, and the risk of flap dislocation from trauma should be much reduced, Dr. Tan said. The absence of a flap may also mean that flap distortion, aberra- tions, wrinkles, etc. are not possible. Dr. Tan pointed out that overall treatment time is shorter, as only one laser is used, especially if the femtosecond and excimer lasers are not co-located in one surgical room, as is often the case, so patients do not need to be transferred from one laser to another. Dr. Wang added that perhaps the most important advantage of these procedures is there is less side cut, which should result in less post- LASIK dry eye as well as less biome- chanical weakening of the cornea. "John Marshall [Ph.D., F.R.C.Ophth., London] and others have shown that it is the vertical cut, not the horizontal lamellar cut, in LASIK that contributes the most amount of biomechanical weakening in a LASIK procedure, predisposing to ectasia," Dr. Wang said. "This is be- cause a vertical cut cuts corneal col- lagen fibers." Another potential advantage of these methods is that the surgeon needs only to use a single platform and therefore this reduces costs for the surgeon and patient, said Colin C.K. Chan, M.D., Chatswood, Aus- tralia. However, this advantage under- scores the biggest drawback to these

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