Differences In Refractive Outcomes Research Articles

Association of refractive outcome with postoperative anterior chamber depth measured with 3 optical biometers.

This study evaluated the relationship between refractive outcomes and postoperative anterior chamber depth (ACD, measured from corneal epithelium to lens) measured by swept-source optical coherence tomography (SS-OCT), optical low-coherence reflectometry (OLCR), and Scheimpflug devices under the undilated pupil. Patients undergoing cataract phacoemulsification with intraocular lens (IOL) implantation in a hospital setting were enrolled. Postoperative ACD (postACD) was performed with an SS-OCT device, an OLCR device, and a Scheimpflug device at least 1month after cataract surgery. After adjusting the mean predicted error to 0, differences in refractive outcomes were calculated with the Olsen formula using actual postACD measured from 3 devices and predicted value. Overall, this comparative case study included 69 eyes of 69 patients, and postACD measurements were successfully taken using all 3 devices. The postACD measured with the SS-OCT, OLCR, and Scheimpflug devices was 4.59 ± 0.30, 4.50 ± 0.30, and 4.54 ± 0.32mm, respectively. Statistically significant differences in postACD were found among 3 devices (P < 0.001), with intraclass correlation coefficients (ICCs) and Bland-Altman showing good agreement. No significant difference in median absolute error was found with the Olsen formula using actual postACD obtained with 3 devices. Percentage prediction errors were within ± 0.50D in 65% (OLCR), 70% (Scheimpflug), and 67% (SS-OCT) calculated by actual postACD versus 64% by predicted value. Substantial agreement was found in postACD measurements obtained from the SS-OCT, OLCR, and Scheimpflug devices, with a trend toward comparable refractive outcomes in the Olsen formula. Meanwhile, postACD measurements may be potentially superior for the additional enhancement of refractive outcomes.

Refractive Outcomes of Intraocular Lenses with Different Haptic Designs Following Phacovitrectomy with Gas Tamponade

Purpose: To compare the refractive outcomes of closed C-loop and C-loop intraocular lenses (IOLs) following phacovitrectomy with gas tamponade.Methods: Medical records of 42 patients (43 eyes) who underwent phacovitrectomy with gas tamponade for idiopathic macular holes between January 2021 and June 2022 were retrospectively reviewed. Closed C-loop (26 eyes; Eyelike K-flex Aspheric&lt;sup&gt;®&lt;/sup&gt;, Koryo Eyetech, Seoul, Korea) and C-loop (17 eyes; Tecnis&lt;sup&gt;®&lt;/sup&gt; ZCB00, Johnson &amp; Johnson Vision, Santa Ana, CA, USA) IOLs were surgically implanted. The main outcome measures were postoperative prediction error and absolute error.Results: There was no significant difference in mean absolute error at 5 months postoperatively (0.34 ± 0.24 diopters [D] and 0.30 ± 0.25 D in the closed C-loop and C-loop IOL groups, respectively; &lt;i&gt;p&lt;/i&gt; = 0.502). The mean prediction error at 5 months postoperatively also showed no significant difference between the groups (-0.28 ± 0.30 D and -0.16 ± 0.36 D, respectively; &lt;i&gt;p&lt;/i&gt; = 0.242). Myopic shift was observed in both groups.Conclusions: There was no significant difference in refractive outcomes between closed C-loop IOLs and C-loop IOLs. A myopic shift was observed in both groups; this should be taken into consideration when calculating IOL power following phacovitrectomy with gas tamponade.

Axial length, vitreoretinal pathology, and anterior chamber depth can predict postoperative refractive outcomes in phacovitrectomy/silicone oil removal.

To evaluate the postoperative refractive prediction error (PE) and determine the factors that affect the refractive outcomes of combined pars plana vitrectomy (PPV) or silicone oil removal (SOR) with cataract surgery. The study is a retrospective, case-series study. Totally 301 eyes of 301 patients undergoing combined PPV/SOR with cataract surgery were enrolled. Eligible individuals were separated into four groups according to their preoperative diagnoses: silicone oil-filled eyes after PPV (group 1), epiretinal membrane (group 2), macular hole (group 3), and primary retinal detachment (RD; group 4). The variables affecting postoperative refractive outcomes were analyzed, including age, gender, preoperative best-corrected visual acuity (BCVA), axial length (AL), keratometry average, anterior chamber depth (ACD), intraocular tamponade, and vitreoretinal pathology. The outcome measurements include the mean refractive PE and the proportions of eyes with a PE within ±0.50 diopter (D) and ±1.00 D. For all patients, the mean PE was -0.04±1.17 D, and 50.17% of patients (eyes) had a PE within ±0.50 D. There was a significant difference in refractive outcomes among the four groups (P=0.028), with RD (group 4) showing the least favorable refractive outcome. In multivariate regression analysis, only AL, vitreoretinal pathology, and ACD were strongly associated with PE (all P<0.01). Univariate analysis revealed that longer eyes (AL>26 mm) and a deeper ACD were correlated with hyperopic PE, and shorter eyes (AL<26 mm) and a shallower ACD were correlated with myopic PE. RD patients have the least favorable refractive outcome. AL, vitreoretinal pathology, and ACD are strongly associated with PE in the combined surgery. These three factors affect refractive outcomes and thus can be used to predict a better postoperative refractive outcome in clinical practice.

Refractive outcomes in infants treated for retinopathy of prematurity

Background: Infants treated for retinopathy of prematurity (ROP) can develop visually significant refractive error. However, the degree of refractive error may differ between laser treatment and intravitreal anti-vascular endothelial growth factor (anti-VEGF) injection. We reviewed studies that investigated refractive error outcomes of treatment in premature infants with ROP.&#x0D; Methods: In this narrative review, a literature search was carried out in PubMed/MEDLINE from 01/01/2000 to 20/10/2022 without language restrictions, using the following keywords: “anti-VEGF,” “ROP” or “prematurity retinopathy,” and “laser.” We included comparative studies on refractive error outcomes of intravitreal anti-VEGF and laser treatments, a combination of both modalities simultaneously or sequentially, and two anti-VEGF agents.&#x0D; Results: The initial search yielded 164 records. We reviewed the titles and abstracts of the retrieved papers and the reference list of published systematic reviews and meta-analyses, meta-analyses, or reviews on our topic. Thirty-three records fulfilled our inclusion criteria, which included refractive outcomes in 4350 eyes of 2359 participants treated for ROP. Based on the reported refractive outcomes, we divided the studies into four categories: 1) those that revealed a higher rate of refractive error in the laser-treated eyes than in the anti-VEGF-treated eyes; 2) those that revealed no significant difference in refractive outcomes between the two treatment modalities; 3) those that revealed a higher rate of refractive error in the anti-VEGF-treated eyes or compared refractive outcomes between two anti-VEGF agents; and 4) those that reported refractive outcomes in the eyes that received combined simultaneous or sequential treatment with laser after initial anti-VEGF treatment. We also summarized the refractive outcomes of all included primary studies in each category.&#x0D; Conclusions: This study showed that the laser-treated eyes experienced more myopic shift. However, the refractive outcomes in premature infants of laser treatment, anti-VEGF treatment, and a combination of both modalities simultaneously or sequentially were often contradictory. This variability resulted from obvious differences in the sample size, different follow-up durations, or inhomogeneous study or treatment designs. Further well-designed prospective trials on refractive outcomes and the trend of changes in the refractive status over long-term follow-ups in the eyes treated with ROP are necessary to identify consensus results concerning real-world refractive outcomes of each treatment modality or simultaneous or sequential combination of both modalities, to suggest a safe and effective treatment option for eye care professionals.

Refractive Outcomes in Fuchs' Endothelial Corneal Dystrophy: Conventional and Femtosecond Laser-Assisted Cataract Surgery.

PurposeTo investigate the refractive outcomes of eyes with Fuchs’ endothelial corneal dystrophy (FECD) following phacoemulsification.MethodsThis is a retrospective chart review of patients with FECD who underwent phacoemulsification. Manifest refraction at the early postoperative period (1–6 weeks) and late postoperative period (3–12 months) was collected. The spherical equivalent (SE) and variance of SE from target in diopters (D) were analyzed.ResultsA total of 219 eyes from 175 FECD patients (73 FLACS, 146 conventional phacoemulsification) were included. In the early postoperative period, when comparing variance from intended target, 62% (n=126) had a SE variance of ≤0.5 D, 22% (n=44) >0.5 D and ≤1 D, and 17% (n=34) >1 D. In the late postoperative period, 62% (n=85) had a SE variance of ≤0.5 D, 19% (n=26) >0.5 D and ≤1 D, and 20% (n=27) >1 D. There was no difference in the variance of SE comparing FLACS versus conventional phacoemulsification in either the early postoperative period (p=0.78) or the late postoperative period (p=0.29).ConclusionPatients with mild-to-moderate FECD had favorable refractive outcomes with phacoemulsification. There was no difference in refractive outcomes in eyes with FECD between the group that underwent FLACS versus the group that underwent conventional phacoemulsification.

Comparison of a trifocal intraocular lens with a +3.0 D bifocal IOL: Results of a prospective randomized clinical trial

To compare visual outcomes in patients with cataract surgery and bilateral implantation of a trifocal or bifocal intraocular lens (IOL). University Eye Clinic Maastricht, the Netherlands. Prospective randomized clinical trial. Eyes with cataract and less than 1.0 diopter (D) of corneal astigmatism were randomized to receive bilateral implantation of Finevision Micro F trifocal IOLs or Acrysof IQ Restor +3.0 bifocal IOLs. Outcome measures were monocular and binocular uncorrected distance (UDVA), uncorrected intermediate (UIVA), and uncorrected near (UNVA) visual acuities; refractive outcomes; binocular defocus curve; contrast sensitivity; reading speed; patient satisfaction; and spectacle independence. Six months postoperatively, the mean binocular UDVA, UIVA, and UNVA in 56 eyes of 28 patients were 0.01 logMAR ± 0.11 (SD), 0.32 ± 0.15 logMAR, and 0.15 ± 0.13 logMAR in the trifocal group (n = 15) and 0.00 ± 0.09 logMAR, 0.28 ± 0.08 logMAR, and 0.12 ± 0.08 logMAR in the bifocal group (n = 13), respectively. The trifocal group showed a more continuous defocus curve and better results at -1.0 D of defocus (P < .01). The mean mesopic contrast sensitivity was higher in the bifocal group (P = .02). Complete spectacle independence was reported by 80% of trifocal patients and 50% of bifocal patients. There were no significant differences in refractive outcomes, reading speed, or patient satisfaction. This study showed noninferiority of visual outcomes with the trifocal IOL compared with the bifocal IOL, although the defocus curve was better at an intermediate distance with the trifocal IOL. Dr. Bauer received study grants from Alcon Laboratories, Inc., Carl Zeiss Meditec AG, and Physiol S.A. and a lecture fee from Alcon Surgical, Inc. Dr. Nuijts is a consultant to Alcon Surgical, Inc., Théa Pharma GmbH, and ASICO LLC; he has received study grants from Acufocus, Inc., Alcon Surgical, Inc., Carl Zeiss Meditec AG, Ophtec BV, and Physiol S.A. No other author has a financial or proprietary interest in any material or method mentioned.

Comparison of 2 femtosecond lasers for flap creation in myopic laser in situ keratomileusis: One-year results

To compare laser in situ keratomileusis (LASIK) outcomes between 2 femtosecond lasers for flap creation in the treatment of myopia up to 1 year. University eye clinic. Prospective randomized eye-to-eye study. Consecutive myopic patients were treated with wavefront-guided LASIK. One eye had a flap created by the Intralase FS 60 kHz femtosecond laser, and the fellow eye was treated with the Intralase iFS 150 kHz femtosecond laser. Eyes were randomized according to ocular dominance. Evaluations included measurement of uncorrected distance visual acuity (UDVA), corrected distance visual acuity, contrast sensitivity and wavefront aberrometry. The study enrolled 122 eyes of 61 patients. The mean preoperative spherical equivalent refraction was -4.62 diopters (D) ± 2.32 (SD) and -4.66 ± 2.30 D in the 150 kHz group and 60kHz group, respectively. Patients preferred the 150 kHz laser to the 60 kHz laser intraoperatively (52.5% versus 26.2%) (P = .005). One week postoperatively, UDVA was 20/16 or better in 85.2% in the 150 kHz group and 70.5% in the 60 kHz group; the difference was statistically significant (P<.05). At 12 months, there were no significant differences in refractive outcomes or higher-order aberrations between the 2 groups. Flap creation with the 150 kHz system and the 60 kHz system resulted in excellent LASIK outcomes. Intraoperatively, patients preferred the 150 kHz system, which yielded better UDVA in the early postoperative period. There were no significant differences at 1 year between the 2 laser systems. Proprietary or commercial disclosures are listed after the references.

Analysis of seasonal changes in residual refraction 1-year after corneal laser refractive surgery: a retrospective study

PurposeTo analyze the effect of seasonal changes in residual refraction 1-year after corneal refractive surgery using the SCHWIND AMARIS laser system. Methods5740 consecutive treatments have been retrospectively reviewed. For all eyes, aspheric treatments were planned with the Custom Ablation Manager software and the ablations were performed with the SCHWIND AMARIS system (SCHWIND eye-tech-solutions). Seasonal outcomes were evaluated in terms of residual refraction stratified per treatment month, as well as stratified per year season. Student's T test comparing stratified values with global ones was used for the statistical analysis. ResultsTreatments performed in April, June, August, September, and October showed relative undercorrections of the spherical equivalent (SE) (−0.09D), whereas treatments performed in January, February, and March showed relative overcorrections of the SE (+0.13D). Similarly, treatments performed in spring and summer showed relative undercorrections of the SE (−0.04D), whereas treatments performed in winter showed relative overcorrections of the SE (+0.10D). ConclusionsSeasonal differences in refractive outcomes were observed among a large scale population. The effect of these environmental variables on refractive outcomes warrants further evaluation.

The effect of 0.5% tropicamide/0.5% phenylephrine mixed eye drop in Chinese adults with myopia and its inter-eye difference in refractive outcomes

Objective:To evaluate the effect of 0.5% tropicamide/0.5% phenylephrine mixed eye drop and make the inter-eye comparison of refractive outcomes in Chinese adults with myopia.Methods:Refractive measurements were performed without cycloplegia and repeated 30 minutes later with 0.5% tropicamide/0.5% phenylephrine mixed eye drop (Mydrin-P) on 341 myopic adults. Vector analysis was used to analyze the data. Changes of spherical equivalent (M) and astigmatism for both J0 and J45 components between these two refractions were calculated as Error_M, Error_J0 and Error_J45. Inter-eye correlations were studied. The inter-eye difference after cycloplegics were described as Diff M, Diff J0 and Diff J45. The effect of anisometropia, age and the higher order aberrations (HOAs) on inter-eye differences toward the cycloplegic agent were analyzed.Results:Difference was found only for the Error_J45 component between the two eyes (p = 0.0040). Pearson correlation coefficients between the two eyes for Error_M, Error_J0, and Error_J45 were 0.3140 (p < 0.0001), 0.1464 (p = 0.0068), and 0.0099 (p = 0.8558), respectively. The inter-eye differences (Diff) in response to cycloplegic agent increased with the amount of anisometropia. The oldest group had the highest Diff M values. However, HOAs were found not to be related to the inter-eye differences.Conclusions:Accommodation was still relaxed by tropicamide/phenylephrine eye drops in myopic adults. The changes of refraction due to cycloplegia were not well correlated between the two eyes in myopic patients. Anisometropia and ocular dominance might be an important factor for the inter-eye difference.

Effect of scanning patterns on the results of femtosecond laser lenticule extraction refractive surgery

To report the clinical results of refractive lenticule extraction using a femtosecond laser and describe the effect of scanning patterns on the results. Private laser center, Vadodara, India. Prospective clinical study. The Visumax femtosecond laser system was used to perform lenticule extraction to treat refractive errors using 2 scanning trajectories. The laser was used to cut a refractive lenticule intrastromally to correct myopia or myopic astigmatism. The lenticule was then physically extracted from the stroma. In scanning pattern A, the laser scanned from the center out and the periphery in while the 2 surfaces of the lenticule were cut. In scan pattern B, the laser scanned from the periphery in and the center out. Outcome measures were corrected and uncorrected distance visual acuities and manifest refraction during a 6-month follow-up. Differences between the 2 scanning patterns were also analyzed. The study comprised 329 eyes of 173 patients. One week postoperatively, there were statistically significant differences in refractive outcomes (P=.03), safety (P<.01), and efficacy (P<.01), between the 2 scanning-pattern groups. At 6 months, there were no significant differences. Early visual recovery and refractive outcomes after femtosecond lenticule extraction were affected by the scanning trajectory of the laser. A trajectory that scanned from the periphery to the center and the center to the periphery to cut the 2 lenticule surfaces had a positive effect on visual recovery.

Comparison of LASIK with the OPDCAT or OATz Algorithm Using the NIDEK EC-5000CXII Excimer Laser

To compare refractive outcomes, higher order aberrations, visual quality, and patient satisfaction between aspheric and whole-eye wavefront aspheric LASIK algorithms. Two hundred seventy-four eyes of 152 patients undergoing LASIK for myopia and myopic astigmatism were divided into two groups: eyes that underwent treatment using either the OPD-guided customized aspheric treatment (OPDCAT) or optimized aspheric treatment zone (OATz). Both groups were subdivided into two groups based on preoperative manifest refraction spherical equivalent (MRSE) <or= 6.00 diopters (D) and eyes with MRSE >or = - 6.00 D. Both groups were additionally subdivided into eyes with preoperative ocular higher order aberrations <0.40 microm and eyes with higher order aberrations >or = 0.40 microm. A P value <.05 was considered statistically significant. At 3 months postoperatively, 88.3% (242/274) of eyes were available for follow-up. Postoperatively, 91.4% of eyes in the OPDCAT group and 90.6% of eyes in the OATz group were within 0.50 D. No difference in refractive outcomes and patient satisfaction among groups or subgroups was noted (P>.05). A significantly less change in asphericity (less oblate) was noted for the OPDCAT group (0.31 +/- 0.30) compared with the OATz group (0.51 +/- 0.35) (P<.05). A lower induction of aberrations in the OPDCAT group compared with the OATz group was noted ( P<.05). Mesopic contrast sensitivity was significantly higher for the OPDCAT groups and subgroups (P<.05). Refractive outcomes between groups or subgroups were equivalent. A significantly lower induction of higher order aberrations and less change in asphericity in the OPDCAT group was noted. The OPDCAT algorithm was more likely to maintain mesopic contrast sensitivity.

Comparison of anterior chamber depth measurements taken with the Pentacam, Orbscan IIz and IOLMaster in myopic and emmetropic eyes

This study determined to assess the degree of agreement between anterior chamber depth (ACD) measurements obtained using three different devices and to analyse the relationship between ACD and spherical equivalent (SE) refraction. In this cross-sectional study, 42 eyes of 42 patients with a mean SE of - 4.69 +/- 4.61 D (range 0.00 D to - 14.88 D) were analysed. Measurements of ACD between the corneal epithelium and the anterior surface of the crystalline lens, obtained using the Pentacam, Orbscan IIz and IOLMaster, were compared. The relationships between SE and ACD measurements obtained with different devices were also investigated. The results were analysed using Bland-Altman analyses, single-sample t-test and Pearson's correlation test. Orbscan ACD measurements were an average of 0.05 mm less than Pentacam measurements (p = 0.01). IOLMaster measurements were an average of 0.06 mm less than Orbscan measurements (p < 0.001). None of the ACD values measured by any of the devices were correlated with increasing SE (p > 0.05 for all). There was a weak positive correlation between SE and the difference in ACD measurements with Pentacam and Orbscan (p = 0.04); however, the differences between Pentacam and IOLMaster ACD measurements and Orbscan and IOLMaster ACD measurements seemed to be independent of SE (p = 0.17 and p = 0.54, respectively). The ACD in clinically normal eyes is measured differently by various non-ultrasonic devices. However, the observed mean error between these modalities is too small to create any noticeable difference in refractive outcome. No significant relationship was found between SE and ACD measurements obtained by Pentacam, Orbscan or IOLMaster.

Optical biometry in combined phacovitrectomy

To assess the accuracy of intraocular lens (IOL) power calculation using optical biometry in patients having combined phacovitrectomy for macular hole and macular pucker. Sunderland Eye Infirmary, North East England, United Kingdom. This single-surgeon retrospective case series review comprised eyes having combined narrow-gauge phacovitrectomy for macular hole or macular pucker. Intraocular lens power was calculated using the results of optical biometry and the Haigis formula. Achieved and planned refraction were compared to calculate the mean postoperative refractive prediction error (ME) and the mean absolute postoperative prediction error (MAE) and the percentage of eyes with an achieved refraction within +/-0.50 diopter (D) and +/-1.00 D of the planned refraction. The results were compared with those in a series of 42 eyes that had phacoemulsification after previous vitrectomy surgery and a series of 60 nonvitrectomized eyes that had uneventful phacoemulsification. Of the of 59 having combined phacovitrectomy, 39 had macular hole and 20 had macular pucker. There was no statistically significant difference in refractive outcomes between the phacovitrectomy group (ME -0.02, MAE 0.39) and the sequential phacoemulsification group (ME -0.10, MAE 0.38) (P = .82). There was a statistically significant difference between the phacovitrectomy group and the phacoemulsification-only group (ME 0.08, MAE 0.26) (P<.001). The use of optical noncontact biometry with the Haigis formula achieved a high degree of accuracy of IOL power estimation in patients having phacovitrectomy. There was no tendency toward a myopic shift, as has been reported using ultrasound axial length measurement.

Author’s reply

Drs. Gimbel, van Westenbrugge, and Penno make important points with regard to the clinical implications of our paper. As we did stress, our study was theoretical. Not withstanding this design, however, we did find a correlation in refractive outcome between the two eyes of an individual patient. This suggests that the first eye result may be applied to improve the outcome of the second eye in some patients. Such a correlation has been supported by other investigators (Nguyen LH, et al. Invest Ophthalmol Vis Sci 2000[Suppl]:41, S687). This finding implies the need for clinical studies specifically directed at this issue if we want to definitively answer the question, but does not address the clinical significance of such a between-eye correlation. Other factors, including general safety of bilateral procedures found in current clinical studies, anisometropia between surgery, and patient dissatisfaction with needing two operative sessions, may mitigate any advantage gained.Analysis in those clinical studies to date that show no difference in refractive outcomes between simultaneous and sequential LASIK, although well designed and executed, are population based and are not specifically designed to look at individual patients in whom this between-eye correlation may be clinically important. Rather, clinical trials specifically addressing the potential difference between simultaneous and sequential treatments with regard to the predictive ability of the first eye on second eye refractive outcome are necessary to uncover or dispel any actual clinical significance of our findings. In the absence of such further study, careful clinical judgment should be used in the decision to perform simultaneous or sequential surgery on an individual patient. Drs. Gimbel, van Westenbrugge, and Penno make important points with regard to the clinical implications of our paper. As we did stress, our study was theoretical. Not withstanding this design, however, we did find a correlation in refractive outcome between the two eyes of an individual patient. This suggests that the first eye result may be applied to improve the outcome of the second eye in some patients. Such a correlation has been supported by other investigators (Nguyen LH, et al. Invest Ophthalmol Vis Sci 2000[Suppl]:41, S687). This finding implies the need for clinical studies specifically directed at this issue if we want to definitively answer the question, but does not address the clinical significance of such a between-eye correlation. Other factors, including general safety of bilateral procedures found in current clinical studies, anisometropia between surgery, and patient dissatisfaction with needing two operative sessions, may mitigate any advantage gained. Analysis in those clinical studies to date that show no difference in refractive outcomes between simultaneous and sequential LASIK, although well designed and executed, are population based and are not specifically designed to look at individual patients in whom this between-eye correlation may be clinically important. Rather, clinical trials specifically addressing the potential difference between simultaneous and sequential treatments with regard to the predictive ability of the first eye on second eye refractive outcome are necessary to uncover or dispel any actual clinical significance of our findings. In the absence of such further study, careful clinical judgment should be used in the decision to perform simultaneous or sequential surgery on an individual patient.

Randomized bilateral comparison of excimer laser in situ keratomileusis and photorefractive keratectomy for 2.50 to 8.00 diopters of myopia

ObjectiveTo compare effectiveness, safety, and stability of excimer laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for low-to-moderate myopia. DesignProspective, randomized, bilateral study. ParticipantsThirty-three patients with a manifest refraction of −2.50 to −8.00 diopters (D) participated. InterventionFor each patient, one eye received LASIK and the other received PRK. The first eye treated, and surgical method in the first eye, were randomized. Both eyes were treated by the same surgeon during the same operative session with a Summit Omnimed I laser (6-mm-diameter ablation) and a Chiron Automated Corneal Shaper. Follow-up was 90% at 1 and 2 years. ResultsAt baseline, mean (±standard deviation) spherical equivalent manifest refraction was −4.80 ± 1.60 D in LASIK-treated eyes and −4.70 ± 1.50 D in PRK-treated eyes. At 1 day after surgery, 81% of patients (21 eyes) reported no pain in the LASIK-treated eye, whereas no patient (0%) reported being pain-free in the PRK-treated eye. At 3 to 4 days after surgery, 18 (80%) LASIK-treated eyes either improved or remained within 1 line of baseline spectacle-corrected visual acuity; only 10 (45%) PRK-treated eyes achieved this result. At 2 years after surgery, 18 (61%) LASIK- and 10 (36%) PRK-treated eyes achieved an uncorrected visual acuity of 20/20 or better, with no statistically significant difference in refractive outcome between the two techniques. Quantitative videokeratography showed more regularity after LASIK. Complications were similar in the two groups. Patients preferred LASIK by a margin of 2 to 1 at 1 year but showed no preference at 2 years. ConclusionsUsing a 6-mm-diameter single-pass, large area ablation and an automated microkeratome to treat myopia of −2.50 to −8.00 D with 1.00 D or less astigmatism in 1994, the authors used LASIK to produce a higher percentage of eyes with an uncorrected visual acuity of 20/20 or better, more regular postoperative corneal topography, less postoperative pain, and more rapid recovery of baseline spectacle-corrected visual acuity than PRK. Both LASIK and PRK achieved successful correction of low-to-moderate myopia at 1 and 2 years after surgery.