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L . Espandar, MD ; M. D. Mifflin, MD; M. Moshirfar MD, FACS John A. Moran Eye Center,

Prospective comparison of visual outcomes after wavefront-guided PRK versus wavefront-guided LASIK. L . Espandar, MD ; M. D. Mifflin, MD; M. Moshirfar MD, FACS John A. Moran Eye Center, University of Utah, SLC, UT

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L . Espandar, MD ; M. D. Mifflin, MD; M. Moshirfar MD, FACS John A. Moran Eye Center,

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  1. Prospective comparison of visual outcomes after wavefront-guided PRK versus wavefront-guided LASIK L. Espandar, MD; M. D. Mifflin, MD; M. Moshirfar MD, FACS John A. Moran Eye Center, University of Utah, SLC, UT No author has any financial or proprietary interest in any materials or methods mentioned. This project was supported in part by an unrestricted educational grant from Allergan Inc., Irvine, CA., to the Department of Ophthalmology and Visual Sciences at the University of Utah, John A. Moran Eye Center, Salt Lake City, UT.

  2. PURPOSE • To prospectively compare the visual outcomes (e.g. UCVA, BSCVA, and HOA) between wavefront-guided PRK and LASIK using the VISX Star S4 CustomVue™ with Iris Registration platform.

  3. Background • High Order Aberrations (HOA) correlate poorly with refraction and visual acuity.1-6 • Total HOAs are significantly increased by PRK and LASIK.1-3 • Wavefront-guided PRK and LASIK have overall better visual outcomes than conventional platform.1,7,8 • There are few studies directly compared wavefront-guided PRK to LASIK. 1,4 • To the best of our knowledge, our study is the first study to compare wavefront-guided PRK and LASIK using VISX platform with Iris Registration technology.

  4. METHODS • Fifty two patients (104 eyes) with mean sphere of -4.78±2.03 D and mean cylinder of 0.96±0.779 underwent wavefront-guided PRK with the VISX Star S4 CustomVue™ IR platform. • Epithelial removel was done with 20% ethanol in 8.5 mm fixation well for 35 seconds and using an epithelial micro-ho scraper, then custom ablation was performed, if stromal ablation ≥65 µm (n=10), mitomycin 0.02% was applied for 20 seconds. • Fifty two patients (104 eyes) with mean sphere of -4.77±2.22 D and mean cylinder of 1±0.798 underwent wavefront-guided LASIK with the VISX Star S4 CustomVue™ IR platform. • Lamellar flap created with IntraLase™femtosecond laser at 60 kHz in a raster pattern with a bed energy of 1.15 µJ, pulse separation of 8x8, side cut energy of 2 µJ, thickness of 110µm, superior hinge, a hinge angle of 50°, a side cut angle of 70°, and diameter of 8.7-9 mm • Laser ablation was performed using v 5.10 Fourier software of VISX Star S4 CustomVue™ per protocol. • All eyes received VISX WaveScan™ aberrometry v3.67 Fourier preoperatively, without pharmacological intervention, under mesopic condition with pupil diameter ≥ 6 mm.

  5. RESULTS • At 6 months, the mean values for the logarithm of the minimum angle of resolution (logMAR) of UCVA were -0.03 ± 0.10 (20/19) in the wavefront-guided PRK group and 0.07 ±0.09 (20/24) in the wavefront-guided LASIK group (p=0.544). Figure 1 • Seventy-five percent of eyes in both groups achieved UCVA ≥ 20/20 (p=0.923). Figure 2 • Ninety percent of eyes in the wavefront-guided PRK group and 91% in the wavefront-guided LASIK group were within ±0.5 D of emmetropia (p=0.760). Figure 3 • Mean postoperative higher order aberration (HOA) root mean square (RMS) in the wavefront-guided PRK group was 0.45 ± 0.13 µm, and was 0.59 ± 0.22 µm (p=0.012) in the LASIK group, representing factor increases of 1.29 and 1.84 respectively. Figure 4

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  10. CONCLUSIONS • Wavefront-guided PRK and wavefront-guided LASIK were found to have similar efficacy, safety and predictability. • This study demonstrated that wavefront-guided PRK induced less HOA than wavefront-guided LASIK at 6 months.

  11. REFERENCES • 1. Zhang J, Zhou Y, Wang N et al. Comparison of visual performance between conventional LASIK and wavefront-guided LASIK with iris-registration. Chin Med J. 2008;121:137.42 • 2. Chalita MR, Chavala S, Xu M et al. Wavefront analysis in post-LASIK eyes and its correlation with visual symptoms, refraction, and topography. Ophthalmology. 2004;111:447.53 • 3. Waheed S, Chalita MR, Xu M et al. Flap-induced and laser-induced ocular aberrations in a two-step LASIK procedure. J Refract Surg. 2005;21:346.52 • 4. Sharma M, Wachler BS, Chan CC. Higher-order aberrations and relative risk of symptoms after LASIK. J Refract Surg. 2007;23:252.6 • 5. Yamane N, Miyata K, Samejima T, et al. Ocular higher-end order aberrations and contrast sensitivity after conventional laser in situ keratamileusis. Invest Ophthalmol Vis Sci. 2004;45:3986.90 • 6. Wang Y, Zhao K, HE J, et al. Ocular higher-order aberrations features analysis after corneal refractive surgery. Chin Med J. 2007;120:269.73 • 7.Wigledowska-Promienska D, Zawojska I. Changes in higher order aberrations after wavefront- guided PRK for correction of low to moderate myopia and myopic astigmatism: two-year follow up. Eur J Ophthalmol. 2007;17:507.14 • 8. Srinivasan S, Drake A, Herzig S. Photorefractive keratectomy with 0.02% mitomycin C for treatment of residual refractive errors after LASIK. J Refract Surg. 2008;24:S64.7

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