Effect of varying microkeratome parameters on laser in situ keratomileusis interface surfaces.

PURPOSE: To evaluate the effect of altering microkeratome parameters (oscillation rates and head-advance speeds) and repeated blade use on human and porcine laser in situ keratomileusis interface surface quality and to evaluate correlations between human and porcine interface surface quality. SETTING: Emory Vision, Atlanta, Georgia, USA. METHODS: Corneal flaps were created in porcine eyes and human cadaver eyes with an Amadeus I microkeratome using varying head-advance speeds and oscillation rates. Microkeratome blades were used once in 18 porcine eyes, twice in 18 human eyes (simulating clinical use), and 5 times in 15 porcine eyes. The interface surface was imaged with electron microscopy, with overall bed quality and surface smoothness graded from 1 to 5 (smoothest to roughest) by 5 masked corneal specialists using the same grading criteria for porcine eyes and human eyes. RESULTS: Neither oscillation rates nor head-advance speeds consistently influenced bed smoothness in any group. There were no differences in bed quality between first cuts and second cuts in human eyes or between porcine eyes with multiple blade use. Porcine eyes had statistically significantly smoother stromal beds than human eyes (P<.01); there was no correlation between porcine eye scores and human eye scores (r = -0.1). CONCLUSIONS: Neither alterations in microkeratome parameters nor repeated blade use consistently influenced stromal bed quality in human or porcine eyes. No subjective correlation existed between stromal bed qualities of porcine corneas and human corneas; therefore, future studies evaluating corneal stromal bed quality should be performed in human corneas only.

Higher-order aberrations after wavefront-optimized photorefractive keratectomy and laser in situ keratomileusis.

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.

Outcomes of wavefront-optimized surface ablation.

PURPOSE: To compare early visual outcomes after wavefront-optimized advanced surface ablation (ASA) with those after wavefront-optimized LASIK. DESIGN: Retrospective comparative series. PARTICIPANTS: One hundred thirty-six eyes undergoing ASA and 136 preoperative refraction-matched eyes undergoing LASIK from June 2004 through October 2005. METHODS: Database review of preoperative characteristics, including patient age, gender, refraction, and central corneal pachymetry; perioperative information, including type of surgery, flap thickness (for LASIK cases), ablation depth, and residual stromal bed thickness; and postoperative information, including uncorrected visual acuity (UCVA) at 1 day, 1 week, 2 weeks, and 3 months, refraction at 3 months, and complications. All ASA patients had topical mitomycin C applied intraoperatively. MAIN OUTCOMES MEASURES: Postoperative UCVA, best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE) refraction, speed of visual recovery, and postoperative complications. RESULTS: Surface ablation patients were younger (35.4 years vs. 39.8 years, P = 0.0002) and had thinner corneas (514 microm vs. 549 microm, P<0.0001) preoperatively. Average UCVA was significantly better after LASIK at 1 day (20/26.8 vs. 20/50.4, P<0.0001) and 2 weeks (20/24.4 vs. 20/33.3, P = 0.0002) postoperatively. However, by 3 months postoperatively, UCVA was better after ASA (20/20.8 vs. 20/22.7, P = 0.05), and 81.5% of patients achieved 20/20 or better UCVA after ASA, compared with 70.5% after LASIK (P = 0.05). More ASA eyes had postoperative UCVA that achieved or surpassed preoperative BSCVA than LASIK eyes (66% vs. 41.6%, P<0.0001). There were 53 patients who underwent bilateral simultaneous ASA. By 1 week, 87.5% had 20/40 or better UCVA in at least one eye and 62.5% had 20/40 or better UCVA in both eyes. By 2 weeks, 86.8% had 20/40 or better UCVA in one eye and 82.6% had 20/40 or better UCVA in both eyes. CONCLUSION: Initial visual recovery is more rapid after LASIK; however, by 3 months postoperatively UCVA and SE refractions were better after ASA. Advanced surface ablation is an effective alternative to LASIK, and based on early visual recovery, bilateral simultaneous surface ablation is a reasonable alternative to sequential surgery for the majority of patients.