SPS-115 Refractive Procedure Comparisons: PRK, LASIK | ASCRS
2020 ASCRS Virtual Annual Meeting

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Papers in this Session
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Clinical Comparison of Three Strategies in Topography-Guided LASIK to Correct Myopia and Myopic Astigmatism
Author
Zhang Jun, MD

Purpose
To assess clinical results of three planning strategies-ZZ vector-compensative refraction (ZZ VR), clinical refraction (CR) and topography modified refraction (TMR) in the myopia and myopic astigmatism correction using topography-guided LASIK.

Methods
This was a prospective study. Consecutive patients were enrolled between November 2018 and February 2019 for topography-guided LASIK. Subjects were randomly treated with ZZ VR, CR or TMR strategy in topography-guided LASIK. The theory of ZZ VR was to consider both manifest refraction and refraction affected by high order aberrations (HOAs), and apply vector analysis to finalize correction on astigmatic power and axis. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), sphere, cylinder and spherical equivalent (SE) were assessed preoperatively and 1 day, 1 month, 3 months and 6 months postoperatively.

Results
A total of 84 eyes in 43 patients were included. Among ZZ VR (n=35), TMR (n=24), and CR (n=25) strategies, cylinder at 6-month after surgery were -0.26±0.27 D, -0.61±0.32 D, and -0.38±0.22 D (P<0.001), respectively. For the comparison of cylinder between each two groups, there were significant differences at 1 day, 1 month and 3 months (all with P<0.05), and the differences between ZZ VR and CR were not significant at 2 weeks and 6 months after surgery (P=0.11 and P=0.16). UCVA at 6 months were -0.09±0.06, -0.05±0.06, and -0.08±0.05 (F=3.03, P=0.05), respectively, however, UCVA between TMR and the other two groups at the rest of follow-up visits were statistically significant (all P<0.05).

Conclusion
Compared to CR and TMR strategies, ZZ VR strategy offered superior outcomes in efficacy and predictability in topography-guided LASIK for myopia and myopic astigmatism correction.
Analysis of Astigmatic Programming for Optimal Results of Topography-Guided Treatment with an Excimer Laser
Authors
Doyle Stulting, MD, PhD, ABO
Daniel S. Durrie, MD
Richard Potvin, OD
Ronald R. Krueger, MD, MSE
Mark C. Lobanoff, MD, ABO
Manoj V. Motwani, MD
Timothy P. Lindquist, MD, ABO
Karl G. Stonecipher, MD, ABO
Steven H. Linn, OD

Methods
Data on 51 eyes undergoing topography-guided LASIK with the Wavelight Contoura excimer laser in which the preoperative refractive cylinder and the cylinder measured by the WaveLight® Topolyzer™ VARIO differed by 0.50D and/or 10 degrees were contributed by six surgeons at 5 clinical sites. Vector analysis of postoperative cylindrical refractive error and the actual laser programming strategy was used to calculate the cylindrical correction that would, theoretically, have completely eliminated postoperative refractive cylinder. This was compared to calculated results using the preoperative manifest refraction, the topographic cylinder, and the cylinder specified by Phorcides Analytic Engine.

Results
The poorest calculated outcomes were obtained with the manifest refraction and the best with the topographically measured refraction or with Phorcides.

Conclusion
Using the preoperative refractive cylinder as the basis for correction with the Contoura ablation profile does not produce as desirable theoretical, calculated refractive outcomes as does entry of the topographically-measured refraction or the cylinder selected by Phorcides.
Sub-Bowman Flap 85 Microns Laser in Situ Keratomileusis: Procedure and Visual Outcomes Study Results
Authors
Hung-Yuan B. Lin, MD
Ya-Jung Chuang, MD

Purpose
To report on visual results, patient reported outcomes, flap thickness precision in eyes undergoing elliptical thin-flap LASIK (sub-Bowman keratomileusis; SBK) with a temporally hinged ,120° side-cut angles.

Methods
A prospective pilot study to evaluate preoperative and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity (UCVA). Patients completed subjective questionnaires at each visit. Patients were evaluated before surgery and 1 day, 1 week, 2 weeks and 1 month after surgery. In all cases customized WaveLight® EX500 Excimer Laser followed thin flap creation by OCT guided FEMTO LDV Z8 (Ziemer Ophthalmic Systems Port, Switzerland). A pain questionnaire was conducted at 1 day, 2 day and 1 week postoperatively. Target flap thickness varied 85μm in 45 eyes, 90 μm in 7 eyes, and 100 μm in 10 eyes.

Results
The mean preoperative spherical refraction was diopters -4.8 D and the mean cylinder was -0.73 D for all eyes. At one day UCVA of 20/20 or better achieved in 44 eyes. Standardized flap parameters were programmed for each procedure. Intra-operative OCT (Ziemer Z8 LDV) for flap visualization. Heidelberg Optical Coherence Tomography used to measure the post-operative flap thickness. Achieved flap thickness were measured to be very close to intended flap thickness in all cases. All values within 95% confidence limit. All patients were highly satisfied with the procedure. No adverse events reported. No intra- or postoperative complications reported.

Conclusion
Thin-flap LASIK created by FEMTO LDV Z8 is considered to offer advantages of both surface and flap technique with biomechanical stability, painless and leading to earlier visual recovery. The additional customization of the OCT guidance can help the surgeon to visualize the epithelium and plan targeted Sub-bowman flaps of 80-90 µm effectively.
Novel Technique (NT) Combining: Topo, Wavefront, Interferometry from a Single Diagnostic Device: Outcomes in Customized-Ablation LASIK.
Author
A. John Kanellopoulos, MD, ABO

Purpose
To evaluate the safety and efficacy of a novel LASIK technique

Methods
This prospective, consecutive eye study included 60 eyes of 30 patients: each eye was treated with the NT that combined automated calculations from a novel, single diagnostic device and software calculated treatment refraction. The 3-month peri-operative visual performance and refractive data were evaluated.

Results
Mean values: UDVA: 20/16; CDVA: 20/13.5; 1 line of vision gained: 55.6%; 2 lines of vision gained: 31.5%. Residual astigmatism over -0.50D: 0%;

Conclusion
Multidiscipline-guided customized NT appears safe and very effective in myopic LASIK, while using a single diagnostic device.
A Retrospective Analysis of Dry Eye Interventions during the First Postoperative Year of Patients Undergoing LASIK Versus PRK
Authors
Pamela B. Ribeiro
Samir A. Melki, MD, PhD
Jason E. Brenner, MD
Alisha A. Ho

Purpose
The most common postoperative complication of laser vision correction is keratoconjunctivitis sicca, or dry eye. Inconsistencies in the literature make it unclear whether LASIK or PRK results in higher rates of dry eye. We explored the proportion of dry eye interventions during the first postoperative year to evaluate the incidence of dry eye.

Methods
Performing a retrospective chart review of all LVC patients between 2009-2019 at a private Boston ophthalmology clinic, the proportion of patients that required postoperative dry eye interventions within the first 12 months following surgery was quantified. All patients outside these parameters were excluded otherwise there was no additional inclusion criterion. At this clinic, a dry eye intervention was defined as either punctal plug insertion and/or prescription medication (Xiidra or Restasis) use. The total number of eyes operated on was 11,175 LASIK eyes from 5,920 individuals, 1,549 LASEK eyes from 880 individuals, and 2,006 PRK eyes from 1,165 individuals.

Results
Comparing the proportion of LASIK dry eye interventions to the proportion of PRK/LASEK dry eye interventions via a 2-sample z-test at an alpha level of significance of 0.05, yielded z = 5.7 and a p-value= <0.0001 at a 95% CI (0.0102 - 0.0208) (Sergeant, 2018).

Conclusion
Our results suggest a greater incidence of postoperative dry eye interventions for PRK/LASEK patients compared to LASIK patients in the 12 months following LVC surgery. This study should help surgeons in deciding which LVC surgery to recommend in order to reduce postoperative dry eye incidence and improve overall patient quality of life.
With-the-Rule (WR) Vs. Against-the-Rule (AR) Vs. Oblique Cylinder (OC): Which Do Better after LASIK Using the Clinical Refraction, and How?
Authors
Costas H. Karabatsas, MD, PhD
A. John Kanellopoulos, MD, ABO

Methods
200 myopic wavefront optimised LASIK cases were retrospectively evaluated for: UDVA, CDVA, Refractive error (RE), topography, tomography. Use of pre-op data available were used to also generate virtual topography-guided LASIK (tgL) plan with topography-modified refraction (TMR) for the cylinder amount and axis adjustment, and correlated to the actual residual refractive and topographic data available. Comparison between the 3 groups was made.

Results
In consecutive myopic LASIK the relative distribution of naïve astigmatism was: WR:171 (85.5%), AR: 10 (0.5%), OC: 19 (0.95%). Overall post-LASIK data for all 3 groups: UDVA: 20/22, CDVA 20/20, RE in Diopters: -0.35 sphere and -0.75 Cylinder. Breakdown for each group was: Residual refractive error of over -0.25 Diopters: WR: 76%, OC: 15%, AR: 9%. When speculating the use of TMR at that time: It would have reduced the residual refractive cylinder in WR more than the AR and then more than the OC group, that appeared to perform best in this regard with WFO LASIK and the clinical refraction used at the time.

Conclusion
Standard Clinical refraction used in WFO LASIK may result in residual refractive cylinder more in with-the-rule candidates. Using TMR and topography-guided LASIK instead may offer improved outcomes through accurate cylinder correction.
Adjusting Cylinder and Sphere Treatment to Balance High Order Aberration Treatments in Topography-Guided LASIK
Authors
David A. Price
Francis W. Price Jr., MD

Purpose
To identify adjustments in manifest sphere and cylinder treatment to compensate effects of treating higher order aberrations (Zernicke Polynomials C6-C27) to optimize topography-guided LASIK outcomes. We hypothesize C11 and C13 (high order astigmatism) should affect cylinder treatment similar to C12 (spherical aberration) with spherical treatment.

Methods
Data from 500 eyes (out of a planned 1,000) which underwent topography-guided LASIK using the EX500 (Alcon, Fort Worth, TX) for C6-C27 was analyzed using regression analysis and non-linear optimization to assess whether programmed cylinder and spherical treatments should be adjusted to minimize post-operative refractive error at 1-month. Additionally, differences between manifest cylinder and Vario estimated cylinder at the axes of 0/90 and 45/135 degrees were compared against C7 and C8 (coma) as well as C11 and C13.

Results
C11 is associated with directional difference in manifest and Vario cylinder at 45/135 degrees (regression coefficient: 1.30 ± 0.27, P < 0.001). C13 is associated with directional difference in manifest and Vario cylinder at 0/90 degrees (0.98 ± 0.30, P = 0.001). C7 and C8 are not significantly associated with cylinder directional differences (P = 0.68, 0.31) nor absolute vector differences (P= 0.44, 0.28) at the axes of 45/135 and 0/90. In surgical nomogram optimization, no variables were significantly correlated with cylinder change at either 0/90 or 45/135 degrees. C12 was found to be significantly correlated with spherical change (-0.70 ± 0.32, P = 0.03).

Conclusion
Adjustments to cylinder treatment to compensate C11 and C13 may be helpful based on the significant association with the difference in Vario and manifest refraction. Data from surgical outcomes is not conclusive but may be complicated by surgical result variability and post-operative refraction error reducing correlations.
Comparison of Wavefront Guided LASIK Visual Outcomes between Two Different Aberrometers
Authors
Blake K. Williamson, MD
Lauren Lim, MD
Margaret Hubbell, MD, PhD

Purpose
To evaluate the visual outcomes after laser-assisted in situ keratomileusis (LASIK) surgery for the correction of myopia or myopic astigmatism using 2 different wavefront aberrometers: WaveScan (Abbott Medical Optics, Inc, Santa Ana, CA) versus iDesign (Johnson & Johnson Vision Care Inc, Jacksonville, FL).

Methods
This retrospective study analyzed 200 eyes from 100 patients who underwent wavefront-guided LASIK performed by 2 different surgeons for myopia and myopic astigmatism using the VisX S41R excimer laser. Wavefront data was derived from WaveScan (102 eyes) or iDesign (98 eyes), a new generation Hartman-Shack aberrometer. Charts were analyzed for pre-operative uncorrected distance visual acuity (UDVA) and refractive error (as determined by WaveScan or iDesign aberrometers), and UDVA on post-op day 1, post-op week 1, post-op week 2, post-op months 1, 2, 3, 4, 5, 6 and 12 if available. Visual acuities were converted and reported into logMAR format for statistical analysis.

Results
Preoperative spherical equivalents differed significantly between the WaveScan (-1.83 ± 0.04 D) and iDesign (-3.29 ± 0.16 D) groups with more myopic patients treated by iDesign. Similarly, preoperative UDVA differed significantly between groups with Wavescan -0.01±0.01 and iDesign -0.07±0.01 (logMAR). Final postoperative UDVA differed significantly with iDesign averaging -0.07± 0.01 and WaveScan -0.01 ± 0.01. A monocular UDVA of 20/10, 20/15, 20/20 and 20/25 was achieved in 5%, 30%, 85% and 97% of Wavescan-treated eyes respectively and achieved in 11%, 57%, 89% and 99% in iDesign-treated eyes respectively. All data reported as average ± standard error. All p-values mentioned above are <0.01.

Conclusion
Despite higher preoperative myopia in the iDesign group, more patients in the iDesign group achieved superior final UDVA than the WaveScan group. More than half of iDesign patients achieved 20/15 vision or better versus less than a third of WaveScan patients. Although “20/happy” was the previous goal, “Better than Perfect Vision” can be achieved.

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