PURPOSE To assess the impact of measurement error on cylinder treatment planning in corneal refractive surgery and to compare the reliability of two indices of cylinder change the Correction Index, based on the surgically induced astigmatism, and the Flattening Index, based on the flattening effect. METHODS Preoperative refractions and surgical outcomes were evaluated using a Monte Carlo simulation. https://www.selleckchem.com/products/atezolizumab.html Cylinder change was calculated using vector analysis. The initial distribution of cylinder magnitudes was matched to a population sample of 1,000 eyes prior to LASIK. Refraction measurement error was modeled both preoperatively and postoperatively, with a non-linear optimization solver optimizing treatment effect for each amount of preoperative cylinder. Model assumptions were subsequently tested against LASIK outcomes data. RESULTS The mean Flattening Index was approximately 1 for all levels of preoperative cylinder, whereas the Correction Index was significantly higher than 1 for cylinder treatments of 1.00 diopters (D) or less when preoperative and postoperative measurement errors were taken into consideration. Targeting undercorrection minimized postoperative cylinder compared with targeting full correction, with the optimal target dependent on the amount of random error in refraction measurement. It was optimal to partially treat 0.25 D of cylinder, even if the presumed level of measurement error was relatively high. CONCLUSIONS The Flattening Index outperforms the Correction Index when accounting for errors in preoperative and postoperative cylinder measurement, particularly when pre-operative cylinder is 1.00 D or less. Treatment nomograms should be adjusted to use the Flattening Index to assess cylinder change, and reporting guidelines should be updated to include the Flattening Index. [J Refract Surg. 2020;36(3)169-174.]. Copyright 2020, SLACK Incorporated.PURPOSE To compare wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in patients with myopia using objective and self-reported quality of vision outcomes. METHODS A total of 40 eyes from 20 participants were prospectively randomized to receive WFG or WFO PRK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). The primary outcome measured was uncorrected distance visual acuity (UDVA) at 12 months postoperatively. Secondary outcome measures included corrected distance visual acuity (CDVA), less than 5% and less than 25% contrast visual acuity, changes in higher order aberrations (HOAs), and self-reported quality of vision. Patients completed a validated, Rasch-tested, linear-scaled 30-item questionnaire assessing the quality of vision and visual symptoms preoperatively and at each visit. RESULTS There was no statistically significant difference (P > .05) between the WFG and WFO groups in the frequency of attaining a refractive error within ±0.25 diopters of emmetropia, achieving postoperative UDVA of 20/16 or better or 20/20 or better, losing one or two or more lines or maintaining their preoperative CDVA, or differences in UDVA, CDVA, low contrast acuity, or HOAs. None of the measured quality of vision parameters exhibited statistically significant differences between the groups preoperatively or at 12 months postoperatively (all P > .05). The WFG and WFO groups each showed significant improvement in multiple subjective measures compared to pretreatment values in the same eye. A total of 12.5% of patients preferred their WFG PRK eye, 31.25% preferred their WFO PRK eye, and 56.25% had no preference at 12 months postoperatively. CONCLUSIONS WFG and WFO PRK using the Alcon Wave-Light Allegretto Eye-Q 400-Hz excimer laser platform provide similar results and self-reported visual symptoms in myopic eyes at 12 months postoperatively. [J Refract Surg. 2020;36(3)160-168.]. Copyright 2020, SLACK Incorporated.PURPOSE To compare the safety, efficacy, and patient-reported quality of vision of small incision lenticule extraction (SMILE) and implantable Collamer lens (ICL) implantation for the treatment of high myopia. METHODS A database of 1,634 SMILE (Carl Zeiss Meditec AG, Jena, Germany) and 225 ICL implantation (STAAR Surgical, Monrovia, CA) procedures was screened for patients with a binocular preoperative manifest refraction spherical equivalent between -6.00 and -10.00 diopters (D) and plano target refraction. One-to-one matching was performed by preoperative manifest refraction spherical equivalent, age, and pupil size. All identified patients were then prospectively examined at their next regular postoperative follow-up visit and presented with the standardized and clinically validated Quality of Vision questionnaire to gauge patient-reported postoperative visual quality. RESULTS A total of 80 eyes (40 patients) were eligible for 11 matching. Mean postoperative follow-up was 27.8 ± 14.3 months in the SMILE gretter uncorrected distance visual acuity, fewer higher order aberrations, and better subjective quality of vision than SMILE. [J Refract Surg. 2020;36(3)150-159.]. Copyright 2020, SLACK Incorporated.PURPOSE To evaluate the effect of cyclotorsion compensation with an image-guided system (Callisto eye; Carl Zeiss Meditec AG, Jena, Germany) on the visual and refractive outcomes of small incision lenticule extraction (SMILE) surgery for astigmatism. METHODS The medical records of 124 right eyes of 124 patients with astigmatism of 0.75 diopters (D) or greater who underwent SMILE for myopic astigmatism were reviewed. Patients were treated with cyclotorsion compensated SMILE or standard SMILE. After the sitting position reference axis was registered with IOLMaster 700 (Carl Zeiss Meditec AG), these data were transferred to the Callisto eye system, which was connected to the operating VisuMax microscope (Carl Zeiss Meditec AG). Cyclotorsion was measured by activating the Z-align function and compensated for by repositioning the patient's body or tilting the head until the reference axis from the IOLMaster 700 (0-180) was parallel to a manually drawn reference axis on the screen (0-180) before docking. The visual and refractive results were studied preoperatively and postoperatively.