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Objective This report presents the results of a randomized clinical trial of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). Design A randomized, prospective, multicenter clinical trial. Participants A total of 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. The mean preoperative manifest refraction spherical equivalent was −9.23 diopters (D) in the PRK group and −9.30 D in the LASIK group. Intervention All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure using the Summit Apex excimer laser. Attempted corrections ranged from 6.00 to 15.00 D. Main outcome measures Data on uncorrected and spectacle-corrected visual acuity, predictability, and stability of refraction, corneal haze, and flap complications were analyzed. Patients were observed for up to 6 months. Results One day after surgery, 0 (0.0%) and 3 (4.5%) eyes in the PRK group saw 20/20 and 20/40 or better uncorrected, respectively, while 7 (10%) and 48 (68.6%) eyes in the LASIK group saw 20/20 and 20/40 or better, respectively. At 6 months after PRK, 13 (19.1%) and 45 (66.2%) eyes saw 20/20 and 20/40 or better, respectively, while after LASIK, 16 (26.2%) and 34 (55.7%) eyes saw 20/20 and 20/40 or better, respectively (odds ratio = 0.56 for likelihood of uncorrected visual acuity Conclusions Although improvement in uncorrected visual acuity is more rapid in LASIK than in PRK, efficacy outcomes in the longer term generally are similar between the two procedures. There is a greater tendency toward undercorrection in LASIK eyes using the specific laser and nomogram in this study, but the scatter in achieved versus attempted correction is similar, suggesting little difference in the accuracy of the two procedures. A suggestion of decreased propensity for loss of spectacle-corrected visual acuity in LASIK eyes requires further investigation.

Objective: The purpose of the study is to determine safety and efficacy outcomes of excimer laser photorefractive keratectomy (PRK) for the treatment of mild-to-moderate myopia. Design: A prospective, multicenter, phase III clinical trial. Participants: A total of 701 eyes of 701 patients were entered in the study; 612 eyes were examined at 2 years after surgery. Intervention: Intervention was photorefractive keratectomy using the Summit ExciMed UV200LA excimer laser (Summit Technology, Inc., Waltham, MA). The treatment zone diameter used was 4.5 mm in 251 eyes (35.8%) and 5 mm in 450 eyes (64.2%). Attempted corrections ranged from 1.50 to 6.00 diopters (D). Main Outcome Measures: Predictability and stability of refraction, uncorrected and spectacle-corrected visual acuity, refractive and keratometric astigmatism, corneal haze, contrast sensitivity, subjective reported problems of glare and halo, and patient satisfaction were the parameters measured. Results: At 2 years, 407 (66.5%) eyes achieved 20/20 or better uncorrected visual acuity and 564 (92.5%) eyes achieved 20/40 or better visual acuity. Three hundred thirty-six (54.9%) eyes were within 0.5 D and 476 (77.8%) eyes were within 1.0 D of attempted correction. Stability of refraction improved with time; 86.8% of eyes were stable within 1.0 D from 6 to 12 months, 94% were stable from 12 to 18 months, and 96.3% were stable from 18 to 24 months. There was no evidence of progressive or late myopic or hyperopic refractive shifts. One hundred fourteen (18.6%) eyes gained 2 or more lines of spectacle-corrected visual acuity, whereas 42 (6.9%) eyes lost 2 or more lines; however, of the latter, 32 (76.2%) had spectacle-corrected visual acuity of 20/25 or better and 39 (92.9%) eyes had 20/40 or better. Four hundred forty-two (72.2%) corneas were clear, 138 (22.5%) showed trace haze, 20 (3.3%) mild haze, 9 (1.5%) moderate haze, and 3 (0.5%) marked haze. On patient questionnaires, 87 (29.7%) patients reported worsening of glare from preoperative baseline; 133 (50.1 %) reported worsening of halo symptoms from baseline. Conclusions: Photorefractive keratectomy appears effective for myopic corrections of −1.50 to −6.00 D. Uncorrected visual acuity is maximized in most eyes by 3 months, although some patients require between 6 months and 1 year to attain their best postoperative uncorrected visual acuity and some may require from 1 to 2 years for stabilization of refraction. Refraction stabilizes progressively without evidence of late myopic or hyperopic refractive shifts. Optical sequelae of glare and halo occur in some patients treated with a 4.5- or 5-mm treatment zone.

Objective: The purpose of the study is to define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK) using a 6-mm beam diameter, investigate changes in patterns over time, and identify associations of topography patterns with clinical outcomes. Design: Multicenter, prospective cohort study. Participants: Ninety-eight eyes of 90 patients with myopia who had undergone PRK using the Summit Technology, Inc., excimer laser with a 6-mm beam diameter. Intervention: Computer-assisted videokeratography data were analyzed for eyes having undergone PRK. Topography patterns at 3, 6, and 12 months after surgery were classified and associations with clinical outcomes assessed. Main Outcomes Measured: Topography patterns after PRK were determined at 3, 6, and 12 months after surgery. Associations with preoperative characteristics of age and attempted correction, and postoperative outcomes of uncorrected and spectacle-corrected visual acuity, predictability, astigmatism, corneal haze, glare, halo, and patient satisfaction were analyzed. Results: At 1 year, 21.4% of corneas showed a homogeneous topography, 27.6% showed a toric-with-axis configuration, 10.2% showed a toric-against-axis configuration, 7.1% showed an irregularly irregular topography, 24.5% showed a keyhole/semicircular pattern, and 9.2% showed focal topographic variants. From 3 to 6 months, 40.1 % of maps changed; from 6 to 12 months, 53.1 % of maps changed, generally to optically smoother, regular patterns. Older age and higher attempted correction were associated with the development of more irregular patterns. The irregular groups showed worse predictability than did the regular groups and a tendency for slight overcorrection. The average reported glare/halo of 1.33 (scale = 0 to 5) in this study was less than in a previous study of the 4.5- to 5-mm treatment zone. However, of six patients expressing dissatisfaction with the results of surgery, three ranked their glare or halo at the maximum level. Conclusions: Topography patterns using a 6-mm beam diameter are identifiable, improve with time, and may affect clinical outcomes after photorefractive keratectomy (PRK). The keyhole/semicircular pattern is more prevalent with a 6 mm treatment zone than with smaller treatment zones. Although optical side effects of glare and halo appear to be reduced with the 6-mm treatment, a small number of patients still report substantial glare or halo after the procedure.

Purpose: To assess the influence of corneal surface microirregularities on objective and subjective visual performance after photorefractive keratectomy (PRK). Setting: Multicenter clinical trial. Methods: The alpha version of the Potential Corneal Acuity (PCA) computer program, currently under development, was used to qualitatively and quantitatively analyze the corneal surface of 176 eyes of 176 patients 1 year after PRK. Color maps of corneal surface irregularities were reviewed and quantitative values (PCA) predicting best spectacle-corrected visual acuity (BSCVA) as limited by the cornea were evaluated for associations with qualitative topography patterns, optical zone decentration, and clinical outcomes of BSCVA, uncorrected visual acuity (UCVA), subjective patient satisfaction, and a subjective glare/halo index. Results: Qualitatively, corneas after PRK were generally characterized by a ring of optical irregularity at the juncture of the ablation zone and untreated cornea. Standard corneal topography maps graded as irregular after PRK had a significantly higher PCA value than those graded as regular. There was a trend toward higher PCA values with greater optical zone decentration that was not statistically significant. Actual BSCVA was identical to that which the PCA value predicted in 32% of patients and was within one Snellen line in 71 %, within two lines in 89%, and within three lines in 94%. The correlation between the PCA and the glare/halo index and with subjective patient satisfaction was statistically significant. The relationship between PCA and UCVA was not significant. Conclusions: A ring of optical microirregularity of the corneal surface can appear at the juncture of the treated and untreated cornea after PRK, indicating that the optical zone edge might affect objective and subjective postoperative visual outcomes. Further understanding of corneal surface topography and refinement of the PCA program should help explain visual outcome after PRK.

Purpose: To define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK), assess changes in patterns, associations with clinical outcomes, and the accuracy of videokeratography in predicting results, and define quantitatively the optical zone contour. Methods: Computer-assisted videokeratography data obtained from 181 patients after PRK was analyzed. Topography patterns at two time points were characterized, and associations with clinical outcomes were tested. Power change predicted by topography was compared with refractive change, and cross-sectional power contours were analyzed. Results: Seven topography patterns were defined. At 1 year, 58.6% of corneas showed a homogeneous topography, 17.7% showed a toric-with-axis configuration, 2.8% showed a toric-against-axis configuration, 13.8% showed an irregularly irregular topography, 2.8% showed a keyhole/semicircular pattern, and 4.4% showed focal topographic variants. No central island patterns were found. Of the maps, 41 % changed over time. Uncorrected vision, predictability, and patient satisfaction were best in the homogeneous group. Astigmatism increased in the irregular and toric-against-axis groups and decreased in the toric-with-axis group. There was no relation of topography pattern to best-corrected vision or subjective glare/halo. Cross-sectional power profiles showed a homogeneous power change for the central 3 mm with a diminution in correction toward the periphery. The topography unit tended to overestimate refractive change for corrections of 5 diopters or less and underestimate the change for corrections greater than 5 diopters. Conclusions: Topography patterns after PRK are identifiable, time dependent, and may affect clinical outcomes. Understanding the actual corneal optical contour resulting from PRK may aid in improving both laser techniques and optical results in the future.

Immediate loss of light perception after direct optic nerve injury is usually irreversible. Our patient sustained presumed direct optic nerve injury because of a shotgun injury with loss of light perception, absent pupillary response, and absent visual-evoked potential. A small pupillary response was noted 12 days after injury, light perception returned by 15 days, and visual acuity was 20/100 at 4 months. A variety of pathophysiologic mechanisms may lead to visual loss after direct optic nerve injury. It is important to recognize that blindness is not always permanent in these cases despite the results of initial clinical and electrophysiologic testing.