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Excellent outcomes can be obtained with topography-guided LASIK using Contoura Vision when the Phorcides Analytical Engine is used to program the WaveLight EX500 excimer laser. Purpose: To evaluate prospectively the clinical outcomes of topography-guided laser in situ keratomileusis (LASIK) surgery performed with Contoura Vision using the Wavelight excimer laser and planned with the Phorcides Analytical Engine. Setting: Four clinical practices in the U.S. Design: Prospective single-arm interventional study. Methods: 130 eyes of 65 patients with myopia or myopic astigmatism were enrolled in a prospective study of visual and refractive outcomes after treatment with Contoura Vision using the Wavelight EX500 excimer laser to achieve optimal distance vision. At 3 months postoperatively, uncorrected distance visual acuity (UDVA), manifest refraction, and corrected distance visual acuity (CDVA) were measured and compared with previously published studies. Results: At 3 months postoperatively, 100%, 89%, and 28% of eyes achieved UDVA of 20/20, 20/15, and 20/12.5 or better, respectively. 92% of eyes had postoperative UDVA equal to or better than their preoperative CDVA. Postoperative CDVA was equal to, 1 line better, or 2 lines better than the preoperative CDVA in 53%, 40%, and 6% of eyes, respectively. Only 1 eye lost 1 line of CDVA, and no eyes lost more than 1 line of CDVA. A statistically significant decrease was noted in subjective visual complaints, including glare, halos, difficulty driving at night, reading difficulty, starbursts, fluctuation in vision, and light sensitivity. Conclusions: The Phorcides Analytical Engine can be used to optimize visual outcomes for the correction of myopia and myopic astigmatism. [ABSTRACT FROM AUTHOR]

Purpose: To identify the laser programming strategy that will achieve optimal refractive outcomes of LASIK with a topography-guided laser for eyes with a disparity between cylinder measured by manifest refraction and cylinder measured by topography. Setting: Six surgeons at 5 clinical sites in the USA. Design: Retrospective data review. Methods: Preoperative, treatment, and postoperative data on 52 eyes that underwent topography-guided LASIK with the WaveLight EX500 Contoura® Vision excimer laser ablation profile in which the vectors representing the preoperative refractive cylinder and the cylinder measured by the WaveLight® Topolyzer™ VARIO Diagnostic Device (Vario cylinder) differed by >/= 0.50D and/or >/= 10 degrees of orientation were analyzed retrospectively. Data were contributed by six surgeons using the laser at 5 different 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 expected results using the preoperative manifest cylinder, the topographic cylinder, and the Phorcides Analytic Engine (Phorcides LLC, North Oaks MN; Phorcides). For analysis, subjects were stratified on the basis of the vector difference between Manifest and Topo cylinder (High, > 0.75 D; and Low, ≤ 0.75 D). Results: The poorest calculated theoretical outcomes were obtained with the manifest refraction (centroid: − 0.43, 0.22; mean calculated error vector: 0.56 ± 0.42 D; p=ns). Better outcomes were obtained with the topographically measured refraction (centroid: 0.37, 0.02; mean calculated error vector: 0.47 ± 0.33 D; p=ns). The best outcomes were obtained with Phorcides (centroid: − 0.15, 0.06; mean calculated error vector: 0.39 ± 0.28 D; p=ns). The mean error vector magnitude in the Phorcides Low group was significantly lower than for the Manifest and Topo Low groups (0.26 D vs 0.48 D and 0.33 D; p< 0.01). The mean error magnitude in the Phorcides High group was nearly 0.25 D lower than for the Manifest High group (0.48 D vs 0.70 D; p< 0.01), but was the same as for the Topo High group (0.48 D vs 0.48 D). Conclusion: Our study suggests that using the topographically measured cylinder or the cylinder selected by Phorcides will produce more desirable refractive outcomes than entry of the preoperative refractive cylinder as the basis for correction of myopia and myopic astigmatism with the WaveLight Contoura Vision excimer laser. [ABSTRACT FROM AUTHOR]

To study eyes with 20/10 uncorrected distance visual acuity (UDVA) 3 months and 12 months after topography-guided LASIK for myopia and myopic astigmatism, and to identify factors predictive of this excellent level of visual acuity. Nine practices in the USA. Prospective unmasked study of safety and effectiveness. The percentage of eyes with UDVA of 20/10 or better at 3 months and 12 months after topography-guided laser in situ keratomileusis (LASIK) with the Contoura Vision excimer laser in a U.S. Food and Drug Administration clinical trial was compared, and possible contributing factors were investigated. Preoperatively, only 1% of eyes had 20/10 corrected distance visual acuity (CDVA). Postoperatively, 7.0% of eyes had 20/10 or better UDVA at 3 months, and this number increased to 16% at 12 months (odds ratio, 2.48; 95% confidence interval, 1.33-4.61). The lower preoperative corneal astigmatism and postoperative refractive cylinder correlated with better postoperative UDVA and CDVA, respectively (P <.01 in all cases). The postoperative UDVA correlated with the postoperative CDVA (P <.01). The number of eyes with UDVA of 20/10 increases significantly between 3 months and 12 months after topography-guided LASIK and correlates with better postoperative CDVA. Eyes with lower preoperative corneal astigmatism are more likely to achieve 20/10 or better UDVA postoperatively. A significant improvement in the number of eyes with 20/10 or better from 3 months to 12 months after LASIK might be unique to topography-guided treatment. [ABSTRACT FROM AUTHOR]

The writers' reference results they have obtained suggesting that astigmatism measured by manifest refraction is superior to topographically measured astigmatism for surgical planning. This statement is the first sentence of a paragraph that explains how Phorcides calculates lenticular astigmatism. Reply: Clinical and refractive outcomes after topography-guided refractive surgery planned using Phorcides surgery planning software. [Extracted from the article]

Purpose: To analyze the changes in higher-order aberrations (HOAs) that occur after wavefront-optimized photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Setting: Emory Eye Center and Emory Vision, Atlanta, Georgia, USA. Methods: This retrospective analysis comprised eyes that had PRK or LASIK from June 2004 through October 2005. Postoperative outcome measures included 3-month uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction spherical equivalent (MRSE), changes in the root mean square (RMS) and grouped coefficient HOAs (microns) measured with a corneal analyzer, and subjective assessment of visual aberrations. Results: One hundred consecutive eyes of 54 patients had PRK, and 100 contemporaneous consecutive eyes of 71 patients had LASIK. The PRK and LASIK populations were similar in general demographics, preoperative HOAs, and postoperative UCVA and BSCVA. The mean MRSE was slightly hyperopic after PRK (mean +0.11 diopters [D]) and slightly myopic after LASIK (mean −0.19 D) (P<.0001). There were no statistically significant changes in RMS or grouped coefficient HOA values after PRK or LASIK, nor were there significant differences in postoperative RMS or grouped coefficient HOA values between PRK and LASIK. One percent of PRK and LASIK patients reported a subjective increase in postoperative visual aberrations; 5% reported a subjective improvement postoperatively. Conclusions: Wavefront-optimized excimer laser surgery did not induce significant HOAs after PRK or LASIK. The 2 techniques were equally efficacious and had equivalent postoperative HOA profiles. [Copyright &y& Elsevier]

Purpose: To evaluate the histopathology and ultrastructure of corneas developing ectasia after LASIK or photorefractive keratectomy (PRK). Design: Retrospective case series. Participants: Thirteen specimens from 12 patients undergoing corneal transplantation for progressive ectasia after LASIK (12 specimens) or PRK (1 specimen) were obtained for histopathologic and ultrastructural evaluation. Methods: All 13 ectatic corneas were submitted in formalin for light microscopy. Nine specimens were bisected, and the second half was placed in 2.5% glutaraldehyde for transmission electron microscopy (TEM). Main Outcome Measures: Corneal histopathology, ultrastructure, and pathophysiology. Results: Light microscopy of the post-LASIK specimens showed corneal epithelial hypoplasia and occasional foci of epithelial hyperplasia, Bowman''s layer breaks, a normal stromal thickness of the LASIK flap, a normal thickness of the hypocellular primitive stromal scar, a thinned residual stromal bed (RSB), and larger than normal artifacteous interlamellar clefts in the RSB of the ectatic region. The post-PRK specimen showed similar findings with the addition of a thinned hypercellular fibrotic stromal scar. TEM showed thinning of the collagen lamellae and loss of lamellar number in the RSB of post-LASIK ectasia corneas or throughout the entire corneal stromal bed in the post-PRK ectasia cornea, with the posterior aspect of the corneal stroma being most affected. Conclusions: Histopathologic and ultrastructural studies suggest that interlamellar and interfibrillar biomechanical slippage occurs when the cornea becomes ectatic after LASIK or PRK in the postoperative stress-bearing regions of the corneal stroma. This 2-phase chronic biomechanical failure process is similar to that seen in keratoconus. Composite sciences classify this chronic biomechanical failure process as interfiber fracture. Financial Disclosure(s): The authors have no proprietary or commercial interest in any materials discussed in this article. [Copyright &y& Elsevier]

Purpose: To analyze the epidemiologic features of ectasia after excimer laser corneal refractive surgery, to identify risk factors for its development, and to devise a screening strategy to minimize its occurrence. Design: Retrospective comparative and case–control study. Participants: All cases of ectasia after excimer laser corneal refractive surgery published in the English language with adequate information available through December 2005, unpublished cases seeking treatment at the authors’ institution from 1998 through 2005, and a contemporaneous control group who underwent uneventful LASIK and experienced a normal postoperative course. Methods: Evaluation of preoperative characteristics, including patient age, gender, spherical equivalent refraction, pachymetry, and topographic patterns; perioperative characteristics, including type of surgery performed, flap thickness, ablation depth, and residual stromal bed (RSB) thickness; and postoperative characteristics including time to onset of ectasia. Main Outcome Measures: Development of postoperative corneal ectasia. Results: There were 171 ectasia cases, including 158 published cases and 13 unpublished cases evaluated at the authors’ institution. Ectasia occurred after LASIK in 164 cases (95.9%) and after photorefractive keratectomy (PRK) in 7 cases (4.1%). Compared with controls, more ectasia cases had abnormal preoperative topographies (35.7% vs. 0%; P<1.0×10−15), were significantly younger (34.4 vs. 40.0 years; P<1.0×10−7), were more myopic (−8.53 vs. −5.09 diopters; P<1.0×10−7), had thinner corneas before surgery (521.0 vs. 546.5 μm; P<1.0×10−7), and had less RSB thickness (256.3 vs. 317.3 μm; P<1.0×10−10). Based on subgroup logistic regression analysis, abnormal topography was the most significant factor that discriminated cases from controls, followed by RSB thickness, age, and preoperative corneal thickness, in that order. A risk factor stratification scale was created, taking all recognized risk factors into account in a weighted fashion. This model had a specificity of 91% and a sensitivity of 96% in this series. Conclusions: A quantitative method can be used to identify eyes at risk for developing ectasia after LASIK that, if validated, represents a significant improvement over current screening strategies. [Copyright &y& Elsevier]