EyeWorld Asia-Pacific June 2014 Issue

53 EWAP rEfrActivE June 2014 “If I can treat the tear film and clear up the epithelial staining, I would prefer doing PRK so there is less denervation of the surface. I follow these patients more closely.” Dr. Thompson also emphasizes that dry eye can negatively impact wavefront analysis. Keys to the surgical phase The surgical pearls that improve visual outcomes for both PRK and LASIK include maximizing tear film and being cognizant of the extent of patients’ higher order aberrations. When patients do not have visually significant higher order aberrations, Dr. Thompson is comfortable with wavefront-guided or wavefront-optimized excimer laser ablations. In cases of significant higher order aberrations, the first step is identifying a cause and ruling out possibilities such as dry eye- induced aberrations or lenticular or corneal issues. Dr. Thompson uses the Pentacam (Oculus, Arlington, Wash., U.S.) and the HD Analyzer (Visiometrics, Terrassa, Spain) to measure forward scatter and rule out subtle irregularities that would result in a poor visual outcome after laser vision correction. In the absence of such pathology, Dr. Thompson treats the aberrations with a wavefront-guided system. In cases of visually significant higher order aberrations induced by previous corneal laser procedures, the only effective treatment is wavefront-guided technology, he said. “When enhancing multifocal implants, if there is any reduction in contrast sensitivity, I look closely at the tear film and epithelium. If I am suspicious that the surface is playing a role, I am aggressive with tear film management and will use PRK as a way to both enhance the refractive error and smooth any potential unseen anterior membrane dystrophy for a pristine air/tear interface to help the ultimate visual outcome,” Dr. Thompson said. Surgical preferences Each procedure has its own limitations. Dr. Thompson sees fewer dry eye issues clinically with PRK. He also offers PRK for avoiding epithelium growth under a flap in LASIK procedures performed many years ago that now have a small refractive error they would like treated. But PRK enhancements can carry a haze risk. “Fortunately, one of the benefits that small spot, Gaussian- shaped scanning laser technology brought to laser vision correction was very smooth ablations compared to our broad beam cases in the beginning. This helped visual outcomes, but also lessened the amount of haze reactions we needed to deal with in PRK. This greatly expanded the range of quality PRK.” “Even though I have the epithelium growing under the flap risk from a LASIK from 10 years ago, I don’t have to worry about haze risk with these folks,” Dr. Thompson said. “But I do try to be very diligent about assessing anterior and posterior topography in all cases to minimize the risk of ectasia.” When treating residual refractive error following refractive lens implantations, PRK is often preferred for low corrections. “I include patients in this decision, of course, and if they have a sharp refractive endpoint and all my LASIK check points are satisfied, I am comfortable delivering LASIK for them,” he said. “But if I am concerned at all that the epithelial status is limiting image quality, I will use PRK as my enhancer.” Dr. Thompson concluded, “As you can see, I am a big fan of both PRK and LASIK. Each situation deserves a well-balanced, decisionmaking approach to recommend PRK and/or LASIK. Whether the patient is best suited for a conventional treatment of sphere and cylinder or a custom wavefront-guided or optimized treatment, the approach to delivering the energy on the stromal surface or under a flap deserves careful consideration.” EWAP Editors’ note: Dr. Thompson has financial interests with Abbott Medical Optics (Santa Ana, Calif., U.S.), Alcon (Fort Worth, Texas, U.S.), and WaveTec Vision (Aliso Viejo, Calif., U.S.). reference 1. Katz et al. LASIK versus photorefractive keratectomy for high myopic (> 3 diopter) astigmatism. J Refract Surg. 2013 Dec;29(12):824-31. contact information thompson : vance.thompson@vancethompsonvision.com PRK - from 51 Index to Advertisers Carl Zeiss Meditec Page 13, 46 www.meditec.zeiss.com Cornea Society Page 34, 35 www.corneaday.org/ Haag-Streit AG Page 25 www.haag-streit.com Moria Page 44, 49 www.moria-surgical.com OCULUS Optikgeräte Page 58 www.oculus.de Rayner Intraocular Lenses Page 27 www.rayner.com/home Topcon Corporation Page 23 www.topcon.com.sg/ ASCRS Page 2, 18, 42 , 67 www.ascrs.org APACRS Pag e 5, 7, 30 , 63 , 66 , 68 www.apacrs.org