Eyeworld

49 EW FEATURE June 2017 • Rebirth of laser vision correction the use of a premium intraocular lens, such as a multifocal, extended depth of focus, or a toric IOL, may address visual rehabilitation better, despite the fact that this would be two procedures. I think that doing the cataract procedure first and then trying to normalize the cornea if the patient was symptomatic would be far more difficult," he said. Other options According to Dr. Donnenfeld, if pa- tients are not candidates for topog- raphy-guided PRK or wavefront ab- errometry, the cone can be flattened using phototherapeutic keratectomy with the excimer laser. "This flattens the cone and uses the epithelium to prevent ablation in the flatter areas, while the cones that have thinner epithelia over their surface ablate more rapidly. Very commonly, this can flatten the cone by up to 5 D. We have followed this procedure with a topographic ablation several months later," he said. Finally, for patients who are not candidates for excimer laser, corne- al inlays are helpful in improving cones. "We find this particularly helpful in patients with thin inferi- orly displaced cones, as with pellu- cid marginal degeneration. In sum- mary, there is a whole new world of technologies that allow the corneal surgeon to improve the vision in patients with irregular corneas to dramatically improve their quality of vision as well as their quality of life," Dr. Donnenfeld said. EW Reference 1. Kanellopoulos AJ. Comparison of sequen- tial vs same-day simultaneous collagen cross-linking and topography-guided PRK for treatment of keratoconus. J Refract Surg. 2009;25:S812–8. Editors' note: Drs. Donnenfeld and Kanellopoulos have financial interests with Alcon. Dr. Stein has no financial interests related to this article. Contact information Donnenfeld: ericdonnenfeld@gmail.com Kanellopoulos: ajkmd@mac.com Stein: raymondmstein@gmail.com Dr. Stein noted that this proce- dure can benefit patients of all ages, not just young ones with progres- sive disease. Older patients with stable corneas have the potential to discontinue rigid gas permeable lenses and return to soft contacts or glasses. A. John Kanellopoulos, MD, clinical professor of ophthalmology, New York University Medical School, and medical director, Laservision. gr Institute, Athens, Greece, said patients who have decentered ablations and irregular ablations resulting from refractive procedures with older laser technologies who complain of ghosting, halos, and difficulties with visual function are good candidates for treatment with topography-guided PRK. This procedure will enlarge optical zones and recenter optical zones on the cornea vertex, which is closer to the visual axis of the patient. "Topog- raphy-guided PRK does a great job of treating these patients. The pearl here is that topography-guided PRK addresses only the irregularity of the cornea in regard to the vertex, which we assume is the line of sight, and it may hide some refractive surprises postoperatively. Usually, enlarging optical zones or recen- tering optical zones will result in myopic shift as these treatments with topography resemble hyperopic treatments," Dr. Kanellopoulos said. Most of these issues can be pre- empted with a technique called to- pography neutralization, which may require two steps: (1) to optimize the cornea as a lenticular system and (2) to address potential myopic shift and more rarely a slight hyperopic shift, in a second, mainly spherical ablation. According to Dr. Stein, the amount of improvement in best corrected visual acuity after topogra- phy-guided PRK is dependent on the preoperative level of best corrected spectacle visual acuity. The greater the preoperative loss of acuity, the higher the potential for lines gained. "In general, the improvement is one to six lines of gain," he explained. There is a learning curve with this procedure. "Fortunately, this procedure has been performed outside the U.S. since 2003, and our group in particular has worked on topography-guided treatments ex- tensively, with more than 50 peer-re- viewed publications and hundreds of presentations in meetings over the past 15 years," Dr. Kanellopoulos said. "Our experience, along with that from other investigators around the world, can serve as a great introduction for clinicians getting involved with topography-guided treatments." In combination with crosslinking Patients with thin corneas that are ectatic should undergo corneal crosslinking, which has recently been approved by the U.S. Food and Drug Administration and has been used in Europe for more than 15 years. "Some surgeons perform crosslinking at the same time as the refractive procedure. I prefer to do them as separate procedures, sepa- rated by approximately 3 months or more," Dr. Donnenfeld said. "The reason for this is that there is improved epithelial healing and a more stable refractive error once the crosslinking has been stabilized." Dr. Stein prefers performing corneal crosslinking immediately after topography-guided PRK. "It is important to strengthen a cornea, especially if one removes tissue. Results are more predictable if the corneal crosslinking is done after and not before topography-guided PRK," he said. Dr. Kanellopoulos found in a landmark study that the combina- tion of topography-guided partial PRK and crosslinking appears to have a synergistic effect in the amount of corneal flattening and normalization. 1 It also results in less scarring. "Additionally, there is the fact that if a cornea has been crosslinked and a surface ablation is attempted after that, the ablation will remove the most biomechanically stable part of the stroma that has been reinforced with the crosslinking pro- cess. This may be counterintuitive in the long-term stability of those eyes, so we have since shifted our clinical and surgical paradigm into combin- ing two procedures in what has been known as the Athens protocol. This technique has been adopted by hun- dreds of surgeons internationally, and recently in the United States. It entails the customized topography- guided or wavefront-guided normal- ization of the very irregular cornea combined with corneal crosslink- ing," he explained. Dr. Kanellopoulos said that the improvement in vision is dramatic, but the postoperative recovery can be lengthier than with standard PRK. "Sometimes, 2 weeks may be required for the cornea to re-epithe- lialize and the surface to normalize. Most of these eyes achieve at least 20/40 best corrected visual acuity, which compares favorably to pene- trating keratoplasty. A larger percent- age of patients enjoy uncorrected visual acuities in the 20/20 to 20/25 range. However, I think it would be unwise to view the Athens protocol as a refractive procedure aiming for emmetropia. Topography-guided PRK should aim to normalize the cornea and address potential signif- icant anisometropia at a later time, either with a phakic intraocular lens or with a lens-based procedure, such as clear lens extraction or cataract surgery with a multifocal, toric, or extended depth of focus intraocu- lar lens. Since this technique has been introduced, it has become one third of my clinical practice and has reduced my cornea transplantation rate by 90%," he said. Treat irregular corneas before cataract surgery According to Dr. Kanellopoulos, many surgeons have previously used toric lenses in patients with irreg- ular corneas and have achieved a relatively good visual result. "I, nev- ertheless, think that in these cases, the optimal approach would be to first normalize the cornea and give that eye the ability to become the best possible lenticular system for a cataract procedure to come at a later time, perhaps 2 or 3 months later. At that time, intraocular lens calcula- tion would be far more accurate and

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