EyeWorld India September 2017 Issue

September 2017 12 EWAP FEATURE Treating irregular corneas by Michelle Stephenson EyeWorld Contributing Writer AT A GLANCE r 1BUJFOUT XJUI JSSFHVMBS DPSOFBT BSF PGUFO MFGU XJUI TJHOJàDBOU WJTVBM EJTBCJMJUJFT BOE SFRVJSF HBT QFSNFBCMF DPOUBDU MFOTFT PS QFOFUSBUJOH LFSBUPQMBTUZ UP JNQSPWF UIFJS RVBMJUZ PG WJTJPO r 5PQPHSBQIZ HVJEFE MBTFS BCMBUJPOT B OFX UFDIOPMPHZ BQQSPWFE JO UIF 6 4 JO BSF VOJRVF JO UIBU UIFZ DPNCJOF NZPQJD BOE IZQFSPQJD BCMBUJPOT UP DSFBUF B NPSF SFHVMBS DPSOFBM TVSGBDF r 1BUJFOUT XJUI UIJO DPSOFBT UIBU BSF FDUBUJD TIPVME VOEFSHP DPSOFBM DSPTTMJOLJOH XIJDI IBT SFDFOUMZ CFFO BQQSPWFE CZ UIF 6 4 'PPE BOE %SVH "ENJOJTUSBUJPO BOE IBT CFFO VTFE JO &VSPQF GPS NPSF UIBO ZFBST r *G QBUJFOUT BSF OPU DBOEJEBUFT GPS UPQPHSBQIZ HVJEFE 13, PS XBWFGSPOU BCFSSPNFUSZ UIF DPOF DBO CF áBUUFOFE VTJOH QIPUPUIFSBQFVUJD LFSBUFDUPNZ XJUI UIF FYDJNFS MBTFS Several new technologies are allowing refractive surgeons to significantly improve these patients’ quality of vision K eratoconus is the most common cause of irregu- lar corneas. Other causes include ectasia, trauma, scarring, and previous procedures, such as radial keratotomy. These patients are often left with significant visual disabilities and require gas perme- able contact lenses or penetrating keratoplasty to improve their qual- ity of vision. “One of the greatest advances in refractive surgery has been the ability to treat irregular corneas,” said Eric Donnenfeld, MD , Rockville Centre, New York. “Now, thanks to the advent of several new technologies, refractive sur- geons are able to significantly im- prove many of these patients’ qual- ity of vision. Many times, these patients will no longer need to wear gas permeable lenses, but can wear soft contact lenses or glasses. On occasion, these patients can go spectacle-free.” For patients with mild cor- neal irregularities, Dr. Donnenfeld prefers performing wavefront aber- rometry treatment, which treats the entire visual system including the anterior cornea/posterior cor- nea and lens. “This can be for very mild cases of forme fruste kera- toconus and some other corneal irregularities,” he explained. New technologies are allow- ing surgeons to treat more severe irregularities. Topography-guided laser ablations A new technology approved in the U.S. in 2016 is topography-guided laser ablations. This is unique in that it combines myopic and hy- peropic ablations to create a more regular corneal surface. “With topographic ablations, we are able to treat more significantly irregu- lar corneas, such as more advanced keratoconus,” Dr. Donnenfeld said. “We have found that we can capture images with the Topoly- zer [Alcon, Fort Worth, Texas] in patients who have corneas as steep Figure 1. Topography-guided PRK and corneal crosslinking: Preoperative, postoperative, and difference map. The postop map shows significant reduction in the irregular astigmatism; the difference map shows 7.4 D of flattening over the cone and 5.9 D of steepening to the superior cornea; best corrected spectacle acuity improved from 20/80 to 20/25. Figure 2. Topography-guided PRK and corneal crosslinking: preoperative, postoperative, and difference map. Postop map shows normalization of the corneal contour; best corrected spectacle acuity improved from 20/50 to 20/25. Source (all): Raymond Stein, MD as 60 D. The key aspect of topo- graphic ablations is that they can not only flatten the steep areas of the cornea, but they also steepen the flat areas of the cornea so that we can improve patients by up to 10 D of corneal irregularity on a fairly routine basis.” Topography-guided PRK (rather than LASIK) is performed on these patients because they already have thinner corneas. “Mitomy- cin is used to prevent scarring, and patients are told that visual