The Accuracy of Flap Thickness and Diameter in LASIK Using a Femtosecond Laser.

Purpose: To evaluate the resultant thickness of the WaveLight FS200 (Alcon Vision, LLC) created LASIK flap compared to intended thickness at the surgical visit, using the WaveLight EX500 (Alcon Vision, LLC) pachymeter and the resultant flap diameter compared to intended diameter. Methods: This single arm, prospective, single surgeon study assessed the accuracy of the intended flap thickness and diameter, after successful bilateral LASIK surgery. The WaveLight FS200 femtosecond laser was used to create all flaps with an intended thickness of 120 µm. Flap thickness was calculated by subtracting the stromal bed thickness after flap lift from the preoperative corneal thickness using the WaveLight EX500 on-board optical pachymeter. Flap diameter was determined using digital analysis. Results: A total of 58 subjects (116 eyes) completed the study. The calculated mean flap thickness was 120.6 ± 9.0 µm (range 102 to 143 µm) using the EX500 pre- and post-flap pachymetry measurements. There was no statistically significant difference between the planned and achieved flap thickness (p > 0.05). The mean difference in flap diameter between planned and actual was 0.02 ± 0.05 mm. Corneal thickness measured by Pentacam at up to 2 months preoperatively versus EX500 just prior to surgery was similar, with EX500 measuring 2 µm less on average than the Pentacam. Conclusion: The results suggest that the WaveLight FS200 laser is reliable for LASIK flap thickness and diameter and accurately created flaps at the intended thickness and the intended diameter.

Clinical and refractive outcomes after topography-guided refractive surgery planned using Phorcides surgery planning software.

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.

Clinical outcomes after topography-guided LASIK: comparing results based on a new topography analysis algorithm with those based on manifest refraction.

PURPOSE: To compare short-term refractive and visual acuity outcomes after topography-guided laser in situ keratomileusis (LASIK) planned with a new topography analysis system to those based on the manifest refraction. SETTING: Four clinical sites in the United States. DESIGN: Double-arm, nonmasked, nonrandomized retrospective chart review. METHODS: This was a retrospective study of postoperative refraction and visual acuity at least 2 months after uneventful LASIK using the Contoura Vision algorithm on the WaveLight Topolyzer VARIO laser. One arm comprised eyes treated using the manifest refraction (manifest), while the other included eyes treated with an ablation profile determined by the Phorcides Analytic Engine (analytic). RESULTS: Clinical results from a matched group of 317 manifest eyes and 323 analytic eyes were available for analysis. Residual refractive results, both sphere and cylinder, were similar between groups. However, significantly more eyes had 20/16 or better (-0.1 logarithm of the minimum angle of resolution) uncorrected distance visual acuity (UDVA) (62.5% analytic, 41.3% manifest) and corrected distance visual acuity (CDVA) (77.1% analytic, 51.4% manifest) in the analytic group. All eyes but 1 had a CDVA of 20/20 or better postoperatively. The number of patients with a UDVA better than their preoperative CDVA was significantly higher in the analytic group (36.5%) relative to the manifest group (23.0%). No eye in either group lost more than 1 line of CDVA; significantly more eyes in the analytic group (42.7%) gained 1 or more lines of CDVA relative to the manifest group (30.3%). CONCLUSIONS: Using the Phorcides Analytic Engine for topography-guided surgery planning increased the likelihood of 20/16 UDVA and CDVA relative to using the manifest refraction.

Incidence of corneal epithelial defects with the standard and zero-compression hansatome microkeratomes.

PURPOSE: To evaluate the incidence of epithelial defects in patients who have had laser in situ keratomileusis (LASIK) surgery with the standard compression Hansatome microkeratome head in comparison to the modified (zero-compression) Hansatome microkeratome head (Bausch & Lomb, Rochester, NY). METHODS: This study was a retrospective review of 404 consecutive patients who had LASIK surgery on both eyes between January 2002 and June 2002. The standard compression microkeratome head was used in 216 (53%) cases and the zero-compression microkeratome head was used in 188 (47%) cases. Epithelial defects were categorized as loose epithelium, or a break in the epithelium, within the area of the flap. An adverse outcome for a patient was defined as having an epithelial defect in at least one eye. Odds ratios were estimated using logistic regression. RESULTS: When the standard compression microkeratome head was used, 19 (8.8%) patients had an epithelial defect in at least 1 eye. When the zero-compression microkeratome head was used, 5 (2.7%) patients had an epithelial defect in at least 1 eye. Logistic regression comparing the risk of epithelial defect in either eye with the standard compression head versus the zero-compression head resulted in an age-adjusted odds ratio of 0.2 (95% confidence interval, 0.07 to 0.58, P < .05). CONCLUSIONS: These findings provide evidence that LASIK surgery with a zero-compression head reduces the risk of epithelial defect compared to the standard compression head of the Hansatome microkeratome.

Outcomes of custom laser in situ keratomileusis: dilated wavescans versus undilated wavescans.

PURPOSE: To evaluate refractive outcomes of custom laser in situ keratomileusis (LASIK) based on undilated and pharmacologically dilated wavefront aberrometry with the Visx laser system. SETTING: Clinical refractive practice, St. Louis, Missouri, USA. DESIGN: Comparative case series. METHODS: Eyes that had LASIK using dilated wavescans (study group) were evaluated for the reason for use of dilated scans; age; preoperative refractive error; preoperative root mean square (RMS), coma, trefoil, and spherical aberration values; postoperative uncorrected distance visual acuity (UDVA); postoperative refractive error; percentage of iris-registration capture; and enhancement rate. The study group was compared with a control group that had LASIK using undilated wavescans. RESULTS: The study group comprised 52 eyes (31 patients) and the control group, 104 eyes (55 patients). At 1 month, the mean postoperative UDVA was 20/21 in the study group and 20/22 in the control group and at 3 months, 20/22 and 20/20, respectively. At 1 month, the mean postoperative spherical equivalent (SE) was +0.07 diopter (D) ± 0.49 (SD) in the study group and +0.14 ± 0.30 D in the control group and at 3 months, -0.01 ± 0.44 D and +0.02 ± 0.23 D, respectively; there was no statistically significant difference between groups at either timepoint. There was no statistically significant difference in preoperative RMS or postoperative coma, trefoil, or spherical aberration between the groups. Although the study group had a slightly higher enhancement rate, the difference was not statistically significant. CONCLUSION: Compared with custom LASIK based on undilated wavescans, use of dilated wavescans for custom LASIK resulted in comparable postoperative outcomes. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.