Comparison of Laser in situ Keratomileusis and Photorefractive Keratectomy to Correct Myopia from -1.25 to -6.00 Diopters

[Regression and ablation profiles in corneal refractive surgery]

Regression after corneal refractive surgery is a complex phenomenon which seems inevitable. The choice of surgical technique has very little influence on regression for low myopia or myopic astigmatism. However, LASIK and SMILE are the two techniques of choice in the correction of high myopia. LASIK is also better for the correction of hyperopia, hyperopic astigmatism and mixed astigmatism. Intraoperatively, the choice of a wide optical zone and adherence to a thick residual stromal bed provide stability. Regression may also be reduced by modulating anti-inflammatory therapy, treating dry eye, and using mitomycin C in PKR. In all cases, obtaining keratometry during patient follow-up helps to identify the cause of the regression. The objective of this review is to synthesize recent data from the literature on regression in refractive surgery as a function of the ablation profiles used.

Femtosecond laser assisted in situ keratomileusis (FS-LASIK) yields better results than transepithelial photorefractive keratectomy (Trans-PRK) for correction of low to moderate grade myopia

INTRODUCTION

The purpose of this study was to compare the outcomes of transepithelial photorefractive keratectomy (Trans-PRK) with femtosecond laser assisted in situ keratomileusis (FS-LASIK) for the correction of low to moderate myopia.

METHODS

A retrospective cohort study design was used. The study group included patients with myopia less than -6.0 D, with or without concomitant astigmatism under 2.0 D, who were treated with FS-LASIK or Trans-PRK in 2013 through 2014. Background, clinical and outcome data were collected from the patient files. A comparison between eyes treated with FS-LASIK or Trans-PRK was performed.

RESULTS

The Trans-PRK group was comprised of 1793 eyes and the FS-LASIK group of 666 eyes. Mean ± SD spherical equivalent (SE) refraction prior to surgery was -3.43 ± 1.27 D in the Trans-PRK group and -3.18 ± 1.34 D in the FS-LASIK group (p < 0.001). Efficacy index values were 0.95 ± 0.14 in the Trans-PRK group and 0.98 ± 0.12 in the FS-LASIK group (p < 0.001), and corresponding safety index values were 0.96 ± 0.13 and 0.99 ± 0.12 (p < 0.001). Distance from target refraction was 0.45 ± 0.42 D in Trans-PRK group and 0.43 ± 0.38 D in the FS-LASIK group (p = 0.537); 71.6% and 74.2% of eyes were within ±0.5 D of attempted correction, respectively (p = 0.193).

CONCLUSIONS

Both Trans-PRK and FS-LASIK demonstrated excellent results, mostly comparable with the current literature. FS-LASIK achieved better results than Trans-PRK surgery in the efficacy and safety parameters.

How accurate is an LCD screen version of the Pelli-Robson test?

PURPOSE

To evaluate the accuracy and repeatability of a computer-generated Pelli-Robson test displayed on liquid crystal display (LCD) systems compared to a standard Pelli-Robson chart.

METHODS

Two different randomized crossover experiments were carried out for two different LCD systems for 32 subjects: 6 females and 10 males (40.5 ± 13.0 years) and 9 females and 7 males (27.8 ± 12.2 years), respectively, in the first and second experiment. Two repeated measurements were taken with the printed Pelli-Robson test and with the LCDs at 1 and 3 m. To test LCD reliability, measurements were repeated after 1 week.

RESULTS

In Experiment 1, contrast sensitivity (CS) measured with LCD1 resulted significantly higher than Pelli-Robson both at 1 and at 3 m of about 0.20 log 1/C in both eyes (p < 0.01). Bland-Altman plots showed a proportional bias for LCD1 measures. LCD1 measurements showed reasonable repeatability: ICC was 0.83 and 0.65 at 1 and 3 m, respectively. In Experiment 2, CS measured with LCD2 resulted significantly lower than Pelli-Robson both at 1 and at 3 m of about 0.10 log 1/C in both eyes (p < 0.01). Bland-Altman plots did not show any proportional bias for LCD2 measures. LCD2 measurements showed sufficient repeatability: ICC resulted 0.51 and 0.65 at 1 and 3 m, respectively.

CONCLUSIONS

Computer-generated versions of Pelli-Robson test, displayed on LCD systems, do not provide accurate results compared to classic Pelli-Robson printed version. Clinicians should consider that Pelli-Robson computer-generated versions could be non-interchangeable to the printed version.

Comparison of laser in situ ketatomileusis and photorefractive keratectomy for myopia using a mixed-effects model

Purpose

To compare the results of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for myopia using a mixed-effects model.

Methods

This comparative retrospective study was conducted in 1,127 eyes of 579 patients after LASIK and 270 eyes of 144 patients after PRK who had two or more postoperative follow-ups after 3 months. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refractive spherical equivalent (MRSE), percentage of eyes within ± 0.5 diopters (D) and ± 1.0 D of targeted refraction, and central corneal thickness were compared between PRK and LASIK groups using a mixed-effects model.

Results

Compared with the LASIK group, UCVA in the PRK group was significantly worse in the initial year but was significantly better after 4 years. The average BSCVA was not significantly different between the LASIK and PRK groups after 4 years. The average gain of BSCVA in the PRK group was significantly larger than that of the LASIK group after 2 years. MRSE in the LASIK and PRK groups showed a gradual myopic shift until 6 years after surgery. After 6 years, MRSE in the PRK group remained stable whereas MRSE in the LASIK group continued a myopic shift. The percentages of eyes within ± 0.5 D or ± 1.0 D in the LASIK group were significantly higher than those in the PRK group at 3 months but were significantly lower than those in the PRK group at 10 years.

Conclusions

PRK for myopia shows better efficacy than LASIK for myopia after 4 years.

Corneal Aberrations, Contrast Sensitivity, and Light Distortion in Orthokeratology Patients: 1-Year Results

Purpose. To evaluate the corneal higher-order aberrations (HOA), contrast sensitivity function (CSF), and light distortion (LD) in patients undergoing orthokeratology (OK). Methods. Twenty healthy subjects (mean age: 21.40 ± 8 years) with mean spherical equivalent refractive error M = −2.19 ± 0.97 D were evaluated at 1 day, 1 month, and 1 year after starting OK treatment. Monocular LD, photopic monocular CSF, and corneal HOA for 6 mm pupil size were measured. Results. LD showed an increase after the first night (p < 0.05) and recovery to baseline after 1 month, remaining stable after 1 year (p > 0.05). Spherical-like, coma-like, and secondary astigmatism HOA RMS increased significantly (p ≤ 0.022) from baseline to 1-month visit, remaining unchanged over the follow-up. Contrast sensitivity for medium frequencies (3.0, 4.24, and 6.00 cpd) was significantly correlated with LD parameters at baseline (r ≤ −0.529, p < 0.001). However, after 1 year of treatment, this correlation was only statistically significant for 12 cpd spatial frequency (r ≤ −0.565, p < 0.001). Spherical-like RMS for 6 mm pupil size correlated with irregularity of the LD (r = −0.420, p < 0.05) at the 1-year visit. Conclusion. LD experienced by OK patients recovers after one month of treatment and remains stable in the long term while optical aberrations remain significantly higher than baseline.

Postoperative ocular higher-order aberrations and contrast sensitivity: femtosecond lenticule extraction versus pseudo small-incision lenticule extraction

PURPOSE

To evaluate and compare changes in contrast sensitivity and ocular higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEx) and pseudo small-incision lenticule extraction (SMILE).

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Retrospective case series.

METHOD

Patients had femtosecond lenticule extraction (Group 1) or pseudo small-incision lenticule extraction (Group 2) between March 2010 and December 2011. The main outcome measures were manifest refraction, HOAs, and contrast sensitivity 1, 3, 6, and 12 months postoperatively.

RESULTS

Fifty-two consecutive patients (102 eyes) were recruited, 21 patients (42 eyes) in Group 1 and the 31 patients (60 eyes) in Group 2. The uncorrected and corrected distance visual acuities were significantly better in Group 2 than in Group 1 at 12 months (P = .032). There was no significant increase in 3rd- or 4th-order aberrations at 1 year and no significant difference between the 2 groups preoperatively or postoperatively. At 1 year, there was a significant increase in mesopic contrast sensitivity in Group 2 at 1.5 cycles per degree (cpd) (P = .008) that was not found in Group 1, and photopic contrast sensitivity at 6.0 cpd was higher in Group 2 (P = .027).

CONCLUSIONS

These results indicate that refractive lenticule extraction is safe and effective with no significant induction of HOAs or deterioration in contrast sensitivity at 1 year. Induction of HOAs was not significantly different between both variants of refractive lenticule extraction. However, there was significant improvement in photopic contrast sensitivity after pseudo small-incision lenticule extraction, which persisted through 1 year.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

To compare the effectiveness and safety of LASIK and PRK for correction of myopia by examining post-treatment uncorrected visual acuity, refractive outcome, loss of best spectacle-corrected visual acuity, pain scores, flap complications in LASIK, subepithelial haze, adverse events, quality of life indices and higher order aberrations.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 11), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2012), EMBASE (January 1980 to November 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to November 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 November 2012. We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing LASIK and PRK for the correction of any degree of myopia.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We summarised data using the odds ratio and mean difference. We combined odds ratios using a random-effects model after testing for heterogeneity.

MAIN RESULTS

We included 13 trials (1135 participants, 1923 eyes) in this review. Nine of these trials randomised eyes to treatment, two trials randomised people to treatment and treated both eyes, and two trials randomised people to treatment and treated one eye. None of the paired trials reported an appropriate paired analysis. We considered the overall quality of evidence to be low for most outcomes because of the risk of bias in the included trials. There was evidence that LASIK gives a faster visual recovery than PRK and is a less painful technique. Results at one year after surgery were comparable: most analyses favoured LASIK but they were not statistically significant.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery and is a less painful technique than PRK. The two techniques appear to give similar outcomes one year after surgery. Further trials using contemporary techniques are required to determine whether LASIK and PRK as currently practised are equally safe. Randomising eyes to treatment is an efficient design, but only if analysed properly. In future trials, more efforts could be made to mask the assessment of outcome.

One year follow-up of contrast sensitivity following conventional laser in situ keratomileusis and laser epithelial keratomileusis

PURPOSE

To determine the effect of conventional laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) for myopia on contrast sensitivity (CS) using the Pelli-Robson and Vector Vision CSV-1000E CS tests.

METHODS

A prospective, comparative study was conducted on 36 eyes of 36 patients with myopia undergoing LASIK (18 eyes) and LASEK (18 eyes). Surgery was performed using the Technolas 217z laser (Bausch & Lomb). CS was recorded preoperatively and at 3, 6 and 12 months postoperatively.

RESULTS

No statistically significant difference was found in LogMAR uncorrected visual acuity post-LASIK (-0.02 ± 0.16) and LASEK (-0.04 ± 0.14). Using the Pelli-Robson, CS was significantly lower in the LASIK group 3 and 6 months postoperatively. No significant postoperative reduction in CS was observed in either treatment group. Using the CSV-1000E test, CS was significantly reduced post-LASIK at 3 (p = 0.05) and 6 (p = 0.05) cycles/degree under photopic conditions. No significant postoperative change occurred in the LASEK group under photopic or scotopic conditions. There was no significant difference in postoperative CS between the LASIK and LASEK groups at 3, 6, 12 or 18 cycles/degree using the CSV-1000E test.

CONCLUSION

One year postoperatively, there was no difference in CS between both treatment groups using the Pelli-Robson and CSV-1000E tests. CS was reduced postoperatively in the LASIK group at the lower spatial frequencies under photopic conditions. No postoperative change was detected in CS following LASIK or LASEK using the Pelli-Robson test.

Intraoperative flap complications in laser in situ keratomileusis with two types of microkeratomes

PURPOSE

To determine the incidence and types of intraoperative flap complications in laser in situ keratomileusis (LASIK) encountered with the Hansatome microkeratome and the Moria microkeratome.

METHODS

In this retrospective case series, all patients with intraoperative flap complications who were treated between June 1999 and July 2008 at the Eye Consultants Center in Riyadh, Saudi Arabia, were identified and reviewed.

RESULTS

Of the 4352 subjects who underwent bilateral primary LASIK procedure, intraoperative microkeratome complications were detected in 89 eyes of 83 patients. The overall incidence of flap complications was 89/8704 (1.00%): incomplete flaps occurred in 53 eyes (0.60%), followed by buttonhole flaps in 17 eyes (0.19%), free complete flaps in 10 eyes (0.11%), free partial flaps in 6 eyes (0.07%), sluffed epithelium in 2 eyes (0.023%), and a splitted flap (vertical flap cut) in 1 eye (0.01%). The incidence rates of intraoperative flap complications with the Hansatome microkeratome and the Moria microkeratome were 1.21% (41/3378) and 0.90% (48/5326), respectively (P = 0.19). There was a statistically significant difference between the two microkeratomes with regard to the incidence of buttonhole flaps: 0.33% (11/3378) for the Hansatome microkeratome versus 0.11% (6/5326) for the Moria microkeratome (P = 0.04).

CONCLUSION

Generally, the incidence rates of intraoperative flap complications with the Hansatome microkeratome and the Moria microkeratome were similar. However, buttonhole flaps occurred more often with the Hansatome microkeratome (a type of microkeratome that produces larger flaps). The commonest complication encountered was the incomplete flap, followed by the buttonhole flap and free flap.

Clinical outcomes of photoastigmatic refractive keratectomy for the correction of residual refractive errors following cataract surgery

PURPOSE

To assess the clinical outcomes of photoastigmatic refractive keratectomy (PARK) for the correction of residual refractive errors after cataract surgery.

METHODS

This study evaluated 88 eyes of 66 consecutive patients with mean spherical equivalent refraction of -3.16±1.71 diopters (D) who underwent PARK to correct refractive errors after phacoemulsification with intraocular lens (IOL) implantation. Patient age at the time of surgery was 65.2±12.7 years. Safety, efficacy, predictability, stability, and adverse events of the surgery were assessed 1, 3, 6, and 12 months postoperatively.

RESULTS

At 1 year postoperatively, uncorrected distance visual acuity and corrected distance visual acuity were 0.08±0.16 logMAR (Snellen 20/25) and -0.08±0.11 logMAR (Snellen 20/16), respectively. Safety and efficacy indices were 1.08±0.25 and 0.76±0.28, respectively. At 1 year, 68% of eyes were within ±0.50 D and 88% were within ±1.00 D of targeted correction. Manifest refraction changes of -0.06±1.06 D occurred from 1 week to 1 year. No vision-threatening complications occurred during the observation period.

CONCLUSIONS

Photoastigmatic refractive keratectomy is safe and moderately effective in the correction of residual refractive errors in pseudophakic eyes, suggesting its viability as a surgical option for the treatment of such eyes.

Changes in contrast sensitivity function and ocular higher order aberration by conventional myopic photorefractive keratectomy

PURPOSE

To evaluate the relation between induced changes in ocular higher order aberrations and changes in the contrast sensitivity function in patients undergoing excimer laser photorefractive keratectomy (PRK).

METHODS

Myopic PRK using excimer laser was performed in 31 patients (56 eyes). The preoperative refractive error was -6.2 +/- 2.9 diopters. Before and 1 month after surgery, we measured the ocular higher order aberrations for a 4-mm pupil, and three indices of contrast sensitivity function. From the data collected, the area under the log contrast sensitivity function (AULCSF) was calculated.

RESULTS

PRK significantly reduced AULCSF (P = 0.004), low-contrast visual acuity (P = 0.004), and letter-contrast sensitivity (P = 0.013). Coma-like (P < 0.001) and spherical-like (P < 0.001) aberrations were significantly increased by surgery. The change in AULCSF by surgery significantly correlated with the change in coma-like (r = -0.468, P < 0.001) and spherical-like (r = -0.291, P = 0.033) aberrations. The change in low-contrast visual acuity by PRK significantly correlated with the change in coma-like aberration (r = 0.599, P < 0.007), but not with change in spherical-like aberrations (r = 0.136, P = 0.326). There were significant correlations between changes in letter-contrast sensitivity and changes in coma-like (r = -0.450, P < 0.001) and spherical-like (r = -0.255, P = 0.048) aberrations.

CONCLUSIONS

PRK significantly increases ocular higher order aberrations, which compromise contrast sensitivity function after surgery.

LASEK and Photorefractive Keratectomy for Myopia: Clinical and Confocal Microscopy Comparison

PURPOSE

To compare postoperative visual acuity and corneal morphology after laser epithelial keratomileusis (LASEK) versus photorefractive keratectomy (PRK) in the correction of low to moderate myopia.

METHODS

In a double-blind, randomized clinical trial, 50 myopic patients (mean: -4.5 +/- 1.35 diopters) were randomized to receive LASEK in one eye and PRK in the fellow eye. No mitomycin C eye drops were used in this study. Patients were observed daily for 4 days, then at 1 month and every 3 months up to 1 year. Uncorrected and best-corrected visual acuity (UCVA and BSCVA), manifest refraction, corneal epithelium healing time, postoperative pain, and corneal haze were evaluated. Corneal wound healing was quantified with corneal confocal microscopy.

RESULTS

Refractive error, UCVA, and BSCVA were not statistically different between eyes treated with LASEK and PRK. Corneal epithelium healing time was 2.52 +/- 0.99 days in the eyes treated with PRK and 2.29 +/- 0.52 days in the eyes treated with LASEK (P=.22). The postoperative pain score was 2.17 +/- 0.87 in the eyes treated with PRK and 2.62 +/- 0.60 (P=.02) in the eyes treated with LASEK. Corneal confocal microscopy showed fewer stromal activated keratocytes and less extracellular matrix deposition in the eyes treated with LASEK than in the eyes treated with PRK at 1 month postoperatively (P=.003).

CONCLUSIONS

LASEK is an effective and safe procedure for low to moderate myopia, but it seems more painful until full corneal reepithelization. In the early postoperative period, the corneal wound healing process is significantly less intense in eyes treated with LASEK than in eyes treated with PRK. The role of LASEK in corneal wound healing modulation remains controversial.

One-Year Clinical Results after Epi-LASIK for Myopia

PURPOSE

To evaluate the clinical results of epi-LASIK for the treatment of low to moderate myopia and myopic astigmatism.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Two hundred thirty-four eyes of 138 patients underwent epi-LASIK for the correction of low to moderate myopia. Mean preoperative spherical equivalent ranged from -1.0 to -7.25 diopters (D) (-3.74+/-1.46, mean+/-standard deviation [SD]) and baseline logarithm of the minimum angle of resolution (logMAR) best spectacle-corrected visual acuity (BSCVA) from 0.10 to -0.18 (mean+/-SD, 0.00+/-0.06).

METHODS

All enrolled eyes underwent epi-LASIK using the Centurion SES epikeratome (Norwood Abbey EyeCare, Victoria, Australia) and the Allegretto (Wavelight Laser Technologie AG, Erlangen, Germany) laser platform. The enrolled patients were followed up daily until the epithelial healing was complete as well as at the 1-, 3-, 6-, and 12-month postoperative intervals.

MAIN OUTCOME MEASURES

The main parameters assessed were subjective evaluation of postoperative pain, uncorrected visual acuity (UCVA) and BSCVA, manifest refraction, haze grade, and contrast sensitivity of the operated eyes.

RESULTS

The mean epithelial healing time was 4.70+/-0.87 days (range, 3-7 days), with mean logMAR UCVA on the day of reepithelization of 0.26+/-0.14 (range, 0.7-0.0). One year after the treatment, the spherical equivalent of the treated eyes (n = 222) ranged from -1.25 to +0.625 D (mean+/-SD, -0.18+/-0.6 D), with 80.33% of the eyes within 0.5 D (96.72% within 1 D) of the attempted correction. At the same interval, 86% of the eyes had clear corneas and 14% clinically insignificant (trace) haze, whereas 60% of the eyes had a line gain of 1 or more lines of BSCVA. Mean logMAR contrast sensitivity of the treated eyes at 4 different spatial frequencies was improved or remained unchanged throughout the follow-up period.

CONCLUSIONS

One-year visual and refractive results after epi-LASIK suggest that it is a safe and efficient method for the correction of low to moderate myopia and myopic astigmatism.

Confocal Microscopy Changes in Epithelial and Stromal Thickness up to 7 Years After LASIK and Photorefractive Keratectomy for Myopia

PURPOSE

To determine the long-term changes in epithelial, stromal, and corneal thickness after LASIK and photorefractive keratectomy (PRK).

METHODS

In two prospective observational case series, 11 patients (16 eyes) received LASIK and 12 patients (18 eyes) received PRK to correct myopia or myopic astigmatism. None of the corneas had retreatment procedures. Corneas were examined using confocal microscopy before and at 1 month, and at 1, 2, 3, 5, and 7 years after surgery. Central thicknesses were measured from reflected light intensity profiles recorded by confocal microscopy. Postoperative epithelial thickness was compared to preoperative, and postoperative stromal and corneal thicknesses were compared to thickness at 1 month after surgery.

RESULTS

In LASIK, epithelial thickness at 1 month (51 +/- 4 microm, n = 11) was greater than before surgery (41 +/- 4 microm, n = 16; P < .001) and remained thicker through 7 years (52 +/- 6 microm, n = 13; P < .001). Stromal and corneal thickness did not change between 1 month and 7 years after LASIK. After PRK, corneal thickness at 1 year (464 +/- 44 microm, n = 17) was greater than at 1 month (442 +/- 39 microm, n = 15; P = .001) and remained thicker at 7 years after PRK (471 +/- 45 microm, n = 17; P > .001).

CONCLUSIONS

The early increase in central epithelial thickness after myopic LASIK persists for at least 7 years and is probably the result of epithelial hyperplasia. Central corneal thickness increases during the first year after PRK and remains stable thereafter up to 7 years.

Evidence for Superior Efficacy and Safety of LASIK over Photorefractive Keratectomy for Correction of Myopia

PURPOSE

To examine possible differences in efficacy and safety between LASIK and photorefractive keratectomy (PRK) for correction of myopia.

DESIGN

Meta-analysis/systematic review.

PARTICIPANTS

Patient data from previously reported prospective randomized controlled trials (PRCTs) and a systematic review of prospective case series in the Food and Drug Administration (FDA) clinical trials database.

METHODS

A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify PRCTs comparing LASIK and PRK for correction of myopia. A meta-analysis was performed on the results of PRCTs. In parallel, a systematic review of prospective data from FDA case series of LASIK and PRK for correction of myopia was undertaken.

MAIN OUTCOME MEASURES

Key efficacy outcomes (uncorrected visual acuity [UCVA] > or = 20/20, +/-0.50 diopters [D] of the target mean refractive spherical equivalent) and safety outcomes (loss of > or =2 lines of best spectacle-corrected visual acuity [BSCVA], final BSCVA > or = 20/40, and final BSCVA < 20/25 where preoperative BSCVA was > or =20/20).

RESULTS

Seven PRCTs were identified comparing PRK (683 eyes) and LASIK (403 eyes) for correction of myopia. More LASIK patients achieved UCVA > or = 20/20 at 6 months (odds ratio, random effects model [95% confidence interval], 1.72 [1.14-2.58]; P = 0.009) and 12 months (1.78 [1.15-2.75], P = 0.01). Loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.69 [1.01-7.18], P = 0.05). Data from 14 LASIK (7810 eyes) and 10 PRK (4414 eyes) FDA laser approval case series showed that more LASIK patients achieved UCVA of 20/20 or better at 12 months (1.15 [1.03-1.29], P = 0.01), significantly more LASIK patients were within +/-0.50 D of target refraction at 6 months (1.38 [1.26-1.50], P<0.00001) and 12 months (1.21 [1.08-1.36], P = 0.0009) after treatment, and loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.91 [2.22-3.83], P<0.00001).

CONCLUSIONS

LASIK appears to have efficacy and safety superior to those of PRK. However, the data examined are from studies conducted > or =5 years ago. It is therefore unclear how our findings relate to present-day methods and outcomes. Further trials comparing contemporary equipment and techniques are needed to reevaluate the relative merits of these procedures.

Efficacy of Measuring Visual Performance of LASIK Patients under Photopic and Mesopic Conditions

Introduction: The aim of the study was to compare the visual performance of LASIK eyes measured using high-contrast logMAR letter charts under bright (photopic) and dim (mesopic) conditions. Materials and Methods: A total of 46 subjects (35 ± 8 years of age) undergoing LASIK procedures were recruited for the study. The best spectacle-corrected visual acuity (BSCVA) of each subject was measured using the high-contrast ETDRS logMAR chart under photopic and mesopic conditions at 3 visits: preoperative (Pre), 1 month postoperative (Post1) and 3 months postoperative (Post3). The differences in logMAR scores for the right eyes only were analysed for the Pre-Post1 (n = 46), Pre-Post3 (n = 18) and Post1-Post3 (n = 16) comparisons. Results: The logMAR scores of subjects were worse at the 1-month postoperative visit than preoperatively, and improvement in visual performance was seen at the 3-month postoperative visit. These changes in visual performance became more evident under mesopic conditions. The means and standard errors of the differences in logMAR scores for the Pre-Post3 (0.097 ± 0.020) were slightly larger than those of the Pre-Post1 (-0.067 ± 0.019) and Post1-Post3 (0.031 ± 0.012) comparisons. Under mesopic conditions, the visual performance of the subjects was statistically significant for the 3 comparisons, but not under photopic conditions. Conclusion: High-contrast logMAR chart performed under mesopic conditions has the potential to replace visual acuity measured under photopic conditions in providing more reliable representation of postoperative visual outcomes of LASIK eyes. Eye doctors should consider performing this vision test routinely to gauge the success of LASIK surgery. Key words: Contrast sensitivity, logMAR chart, Visual acuity

Contrast sensitivity function and ocular higher-order wavefront aberrations in normal human eyes

PURPOSE

To investigate the relation between contrast sensitivity function and ocular higher-order wavefront aberrations in normal human eyes.

STUDY DESIGN

Prospective observational case series.

PARTICIPANTS

Three hundred seven eyes of 161 normal subjects, ranging in age from 15 to 60 years (30.9+/-8.0 [mean +/- standard deviation]).

METHODS

Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann-Shack wavefront analyzer. The root-mean-square of the third- and fourth-order Zernike coefficients was used to represent comalike and spherical-like aberrations, respectively. We measured contrast sensitivity, low-contrast visual acuity (VA), and letter contrast sensitivity. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. Pupil diameter in a photopic condition was recorded using a digital camera.

RESULTS

Multiple linear regression analysis revealed that comalike aberration (P = 0.002) was significantly associated with AULCSF, but spherical-like aberration (P = 0.200), age (P = 0.185), and photopic pupil diameter (P=0.252) were not. Comalike aberration showed a significant correlation with low-contrast VA (P<0.001), but spherical-like aberration (P = 0.293), age (P = 0.266), and pupil diameter (P = 0.756) did not. Comalike aberration was found to be significantly associated with letter contrast sensitivity (P<0.001), but spherical-like aberration (P=0.082), age (P = 0.370), and pupil diameter (P = 0.160) were not.

CONCLUSIONS

In normal human eyes, comalike aberration of the eye significantly influences contrast sensitivity function.

LASIK in Myopic Patients With Dermatological Keloids

PURPOSE

To evaluate the visual and refractive out come of LASIK in myopic patients with a known history of dermatological keloid scar.

METHODS

This retrospective case series included 10 eyes of 5 white patients with a known history of dermatological keloids. All patients had low to moderate myopia with no corneal or limbal keloid. All underwent uneventful bilateral LASIK. Postoperatively, visual outcomes, refractive outcomes, and complications were evaluated. Minimum 1-year follow-up was indicated for all patients in this study.

RESULTS

Mean preoperative uncorrected visual acuity (UCVA) was 20/320 and 1 year postoperative 20/20. Mean preoperative best spectacle-corrected visual acuity (BSCVA) was 20/25 and 1 year postoperative was 20/20. The mean preoperative spherical equivalent refraction was -5.00 +/- 2.6 diopters (D) and +0.1 +/- 0.2 D 1 year postoperative. The safety index was 1.02 and the efficacy index was 1.02. None of the included in this study underwent retreatment for correction of residual error or regression up to 1 year postoperatively. No sight-threatening complications were reported. No patient reported postoperative haze, severe dry eye syndrome, or flap-related problems.

CONCLUSIONS

LASIK is a safe, effective, and predictable technique for correcting low and moderate myopia in patients with dermatological keloids.

Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

The aim of this review was to compare the effectiveness and safety of PRK and LASIK for correction of myopia.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005) and LILACs (1982 to 3 November 2005). We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing PRK and LASIK for correction of any degree of myopia. We also included data on adverse events from prospective multicentre consecutive case series in the Food and Drugs Administration (FDA) trials database (http//www.fda.gov/cdrh/LASIK/lasers.htm).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Data were summarised using odds ratio and mean difference. Odds ratios were combined using a random-effects model after testing for heterogeneity.

MAIN RESULTS

This review included six randomised controlled trials involving a total of 417 eyes, of which 201 were treated with PRK and 216 with LASIK. We found that although LASIK gives a faster visual recovery than PRK, the effectiveness of these two procedures is comparable. We found some evidence that LASIK may be less likely than PRK to result in loss of best spectacle-corrected visual acuity.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery than PRK but the effectiveness of these two procedures is comparable. Further trials using contemporary techniques are required to determine whether LASIK and PRK are equally safe.

A Comparative Study for Mesopic Contrast Sensitivity Between Photorefractive Keratectomy and Laser In Situ Keratomileusis

BACKGROUND AND OBJECTIVE

To compare the effect on visual performance of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with mesopic contrast sensitivity.

PATIENTS AND METHODS

Postoperative visual performance for 40 eyes undergoing PRK and 40 eyes undergoing LASIK was compared with mesopic contrast sensitivity at 1, 3, and 6 months postoperatively. Eyes were divided into two groups (< -6.0 D and > -6.25 D). Mesopic contrast sensitivity was performed with the patient's best-corrected visual acuity of 20/20 or better under photopic conditions.

RESULTS

A significant decrease in mesopic contrast sensitivity from preoperative baseline was obtained at all spatial frequencies for the PRK and LASIK groups (P < .05). There was no statistically significant difference at 1 or 3 months postoperatively in both groups (P > .05). At 6 months postoperatively, LASIK significantly decreased mesopic contrast sensitivity more than PRK in myopia with a refractive error of less than -6.0 D, especially at the middle and high spatial frequencies of 6, 9, and 12 cycles per degree (P < .05). However, no statistically significant differences in mesopic contrast sensitivity between PRK and LASIK were found in myopia with a refractive error of greater than -6.25 D (P > .05).

CONCLUSIONS

In broad-beam excimer laser refractive surgery, PRK seemed to have a more significant effect on mesopic contrast sensitivity than LASIK for myopia with a refractive error of less than -6.0 D at 6 months postoperatively.

Étude prospective de la sensibilité au contraste et des effets visuels après LASIK

PURPOSE

To evaluate changes in visual effects (contrast sensitivity, halos, and glare) following laser in situ keratomilleusis (LASIK).

PATIENTS AND METHODS

In this prospective study, 72 eyes had LASIK to correct myopia. Contrast sensitivity was tested preoperatively, as well as 6 and 12 months postoperatively. The spatial frequencies tested were 3, 6, 12, and 18 cycles per degree (c/d). There were two groups: group 1 for myopia between -6 D (n=30) and -7.5 D and group 2 for myopia between -7.5 D and -10 D (n=25). There were 17 cases with loss of sight. For each visit, pupil diameter, halos, and glare were measured.

RESULTS

Contrast sensitivity was better in group 1 than in group 2 (p<0.05) (for spatial frequencies of 3, 12, 18, c/d). In group 1, contrast sensitivity decreased 6 months postoperatively for all spatial frequencies (p<0.05); 12 months after surgery the changes were not significant. In group 2, changes were not significant. For halos and glare, pre- and postoperative percentages were not different. There was no correlation with pupil diameter.

CONCLUSIONS

After LASIK to correct myopia, there may be a persistent decrease in contrast sensitivity. Changes are only significant at 6 months postoperatively. Patients should be informed preoperatively of this possible decrease in functional vision.

LASIK in Patients with Rheumatic Diseases

PURPOSE

To investigate the safety of LASIK in patients with a known history of controlled rheumatic diseases.

DESIGN

Retrospective consecutive observational clinical study.

PARTICIPANTS

Forty-two eyes (22 patients) known to have had a history of rheumatic diseases underwent LASIK. All patients had a history of controlled rheumatic diseases, including rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, scleroderma, ankylosing spondylitis, psoriatic arthritis, inflammatory bowel disease, arthritis, or Behçet's disease.

METHODS

Assessments were made preoperatively and at 1, 3, and 6 months postoperatively and included visual acuity (VA), refraction, keratometric readings, slit-lamp biomicroscopy, and corneal topography. All the patients underwent LASIK. Postoperative treatment included a topical steroid-antibiotic combination.

MAIN OUTCOME MEASURES

Visual acuity, refraction, keratometric readings, and slit-lamp biomicroscopy findings at 1, 3, and 6 months postoperatively.

RESULTS

LASIK was performed uneventfully on all patients. The mean pre-LASIK spherical equivalent (SE) was -5.39+/-2.25, and the sixth month postoperative SE was -0.15+/-0.38 diopters (D) (P<0.001). Uncorrected VA 6 months after the LASIK procedure was 20/25. Enhancement procedures were performed in 6 of 42 eyes (14.3%) at variable times after the primary procedure. Postoperative follow-up showed development of a moderate degree of dry eye syndrome in 4 eyes (9.5%). Corneal haze, melting, flap, or interface complications were not observed in any of the study eyes.

CONCLUSIONS

In this small series, we found good outcomes when correcting refractive errors using LASIK in selected patients with controlled rheumatic diseases. In this series, a favorable postoperative visual outcome was obtained with no operative or postoperative vision-threatening complications.

Severe corneal epithelial sloughing during laser in situ keratomileusis as a presenting sign for silent epithelial basement membrane dystrophy

PURPOSE

To report the occurrence of large intraoperative epithelial sloughing during laser in situ keratomileusis (LASIK) as a first diagnostic sign for silent epithelial basement membrane dystrophy (EBMD).

SETTING

Refractive Surgery and Cornea Unit, Alicante Institute of Ophthalmology, Alicante, Spain.

METHODS

In this retrospective case series, the medical records of all patients with large corneal epithelial sloughing/defects during LASIK from January 1995 to December 2004 were reviewed. All patients who presented normal corneas before LASIK and EBMD changes after LASIK were included in this study. The surgical procedures and postoperative course were recorded. The follow-up period was 12 months for all patients.

RESULTS

Eleven eyes of 6 patients were included. The mean age was 35 years +/- 6.1 (SD). Mean preoperative uncorrected visual acuity (UCVA) was 20/500 (0.04 +/- 0.02); 12 months after surgery, mean UCVA increased to 20/27 (0.74 +/- 0.21). There was a significant decrease in best spectacle-corrected visual acuity 1 month after surgery. One year postoperatively, 10 of 11 eyes (91%) were within +/-1.00 diopter of emmetropia. Postoperatively, clinical manifestations of EBMD were observed in all eyes and complications were common. In the early postoperative period, diffuse lamellar keratitis was observed in 6 of 11 eyes (54.5%) and flap microfolds were noted in 2 of 11 (18.2%). One year after surgery, epithelial ingrowth was present in 8 of 11 eyes (72.7%) and flap melting was noted in 4 of 11 (36.4%).

CONCLUSION

Occurrence of large intraoperative epithelium sloughing/defects during LASIK might be a diagnostic sign for subclinical EBMD. These patients are predisposed to multiple postoperative complications. Because of the high risk for epithelial sloughing in the second eye, LASIK should not be performed.

Effect of a Yellow Filter on Contrast Sensitivity and Disability Glare After Laser in situ Keratomileusis Under Mesopic and Photopic Conditions

PURPOSE

To analyze the effect of a yellow filter on contrast sensitivity and disability glare under mesopic and photopic luminance conditions in laser in situ keratomileusis (LASIK) patients and control subjects.

METHODS

Contrast sensitivity with and without glare was determined in 27 patients who had undergone LASIK at least 1 year previously and in 30 control subjects. Tests were performed with and without a coated yellow filter (X-482 nm cut-off) using the Mesotest II or Mesoptometer II (Oculus, Wetzlar, Germany) under mesopic conditions, and the Contrast Glaretester 1000 (Takagi, Seiko Co Ltd, Nagano, Japan) under photopic conditions.

RESULTS

Under mesopic conditions, log contrast sensitivity without glare decreased by 0.14 log units in the LASIK group. When the yellow filter was used, this variable showed a significant increase of 0.04 log units and the proportion of patients able to discriminate the mesopic contrast limit of 1:5 rose from 70% to 78%. With glare, the yellow filter also improved contrast sensitivity in LASIK patients, but not significantly. Under photopic conditions, no statistical differences were observed between results obtained with and without the yellow filter in the LASIK group or between the LASIK and control group without glare.

CONCLUSIONS

Mesopic contrast sensitivity without glare was worse in LASIK patients and increased significantly with the yellow filter. The filter had no effect under photopic conditions. No disability glare differences were noted between the LASIK and control groups or between the LASIK without and with filter groups under mesopic and photopic conditions.

Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes

PURPOSE

To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.

DESIGN

Prospective, double-masked, randomized clinical trial.

PARTICIPANTS

Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.

METHODS

In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.

RESULTS

Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).

CONCLUSION

Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.

CHARACTERISTICS OF SIXTY MYOPIC EYES WITH PRE-LASER IN SITU KERATOMILEUSIS RETINAL EXAMINATION AND POST-LASER IN SITU KERATOMILEUSIS RETINAL LESIONS

PURPOSE

A survey of eyes with pre-laser in situ keratomileusis (LASIK) retinal examinations and characteristics of post-LASIK retinal breaks and retinal detachments (RDs).

METHODS

A survey of worldwide vitreoretinal surgeons (424 physicians). Surveyed information included demographics, best-corrected visual acuity, degree of myopia, pre- and post-LASIK retinal findings, follow-up time, and treatment outcome.

RESULTS

Sixty eyes with pre-LASIK retinal examinations developed post-LASIK retinal breaks and RDs. There was an average of 2.3 breaks per eye, yielding a total of 140 breaks in the 60 eyes. Forty eyes also had RDs besides the retinal breaks. Large percentages of eyes had substantial myopia (mean myopia, -9.5 +/- 5.8 diopters [D]) and complex vitreoretinal complications. Forty percent developed vitreoretinal complications within 6 months after LASIK. The 20 eyes that developed more extensive RDs (>3 clock hours) had a significantly higher mean myopia than did the 6 eyes that developed limited RD (< or = 3 clock hours) within 12 months after LASIK (-8.92 +/- 6.82 D versus -3.50 +/- 1.97 D, P = 0.03). There were significant statistical differences in distribution of retinal breaks and tears between the temporal and nasal quadrants (P < 0.001, P < 0.001, respectively, chi2, but not between the superior and inferior quadrants.

CONCLUSION

Distributions of retinal breaks in this study were comparable with results found in non-LASIK eyes in young myopes. Treatment for post-LASIK vitreoretinal complications was highly successful. The vulnerability of such highly myopic eyes for vitreoretinal complications warrants their close monitoring.

Decreased keratocyte death after laser-assisted subepithelial keratectomy and photorefractive keratectomy in rabbits

PURPOSE

To compare keratocyte loss in the corneal stroma after laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) in rabbits.

SETTING

Department of Ophthalmology, University of Essen, Essen, and the Institute of Anatomy, University of Bochum, Bochum, Germany.

METHODS

Laser-assisted subepithelial keratectomy and PRK were performed in rabbits and studied 1, 3, 10, and 20 days after surgery. Excimer photoablation was done unilaterally with a 6.0 mm ablation zone and an 80 microm depth, equivalent to -6.0 diopters. Keratocyte death was analyzed using DNA fragmentation-detecting terminal deoxynucleotidyl transferase deoxy-UTR-nick end labeling (TUNEL) assay and transmission electron microscopy.

RESULTS

Numerous TUNEL-positive keratocytes occurred 1 day after PRK; the number decreased significantly after 3 days. After LASEK, significantly fewer TUNEL-positive keratocytes were noted at the early time points (P<.001 at 1 day; P< or =.05 at 3 days). At 10 days, the number of TUNEL-positive keratocytes decreased in both groups but remained significantly higher after PRK than after LASEK (P<.001). Twenty days after both procedures, no significant signs of keratocyte death were found in the corneal stroma. Transmission electron microscopy revealed few apoptotic keratocytes after LASEK. After PRK, apoptotic keratocytes, characterized by chromatin condensation, apoptotic bodies, and cell shrinkage, were scattered in the stroma. The ultrastructural findings confirmed the results obtained with the TUNEL assay.

CONCLUSIONS

Laser-assisted subepithelial keratectomy induced significantly less apoptotic keratocyte death than PRK and promoted wound healing in the acute phase after photoablation. This procedure may offer the possibility of treating higher myopia with a decreased risk for developing wound healing-related complications known to occur after PRK.

Update on laser subepithelial keratectomy (LASEK)

PURPOSE OF REVIEW

This study reviews current concepts in laser subepithelial keratectomy (LASEK), variations in LASEK techniques, the role of pharmacology in LASEK, and optimizing outcomes in LASEK.

RECENT FINDINGS

Recent studies continue to support the use of LASEK over that of LASIK in the correction of refractive error. In addition, the advent of pharmacological/biologic intervention, improved algorithms, and wavefront technology have expanded the armamentarium available to ophthalmologists in the maximization of LASEK outcomes.

SUMMARY

LASEK offers an excellent profile in terms of both final outcome (uncorrected visual acuity) and safety (best corrected visual acuity). Untoward effects of LASEK are readily prevented/treated with a variety of agents. Postoperative pain can be ameliorated using topical and oral analgesia. Infection can be most effectively addressed with the fourth generation of fluoroquinolones. Haze may be treated or prevented using numerous remedies namely autologous serum, steroids, ascorbic acid, mitomycin-c, and NSAIDS. Wavefront combined with LASEK rather than with LASIK may offer the best refractive outcome.

Glare sensitivity and optical side effects 1 year after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE

To compare the outcome of low-contrast visual acuity and glare sensitivity after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne, Switzerland.

METHODS

In this prospective study, patients selected PRK or LASIK after the advantages and disadvantages of both had been described. Snellen visual acuity and disability glare were measured with the Berkeley glare test preoperatively and 1 year postoperatively. At the 1-year follow-up, haze was graded and patients had to assess their quality of vision subjectively.

RESULTS

One-year follow-up of 58 patients in the PRK group and 64 patients in the LASIK group was achieved. In both groups, the mean uncorrected visual acuity was 20/32 (P =.63) and the mean best corrected visual acuity, 20/20 with no statistically significant difference (P =.20). There were no preoperative or postoperative differences between the 2 groups in low-contrast visual acuity under 4 glare conditions. At 1 year, LASIK eyes had significantly lower postoperative haze scores than PRK eyes (P =.0013). The number of eyes with visually moderate and disturbing halos or disturbances in night vision did not differ considerably between the groups (P =.88).

CONCLUSIONS

Efficacy outcomes were generally similar in the PRK and LASIK groups. Both achieved good objective and subjective results after treatment with a second-generation excimer laser.

Laser in situ keratomileusis for myopia and the contrast sensitivity function

PURPOSE

To characterize the clinical effects of laser in situ keratomileusis (LASIK) on the cornea and visual performance by the contrast sensitivity function (CSF).

SETTING

Clinique d'Ophtalmologie IRIS, Laval, Quebec, Canada.

METHODS

Thirty-four patients aged 18 to 50 years volunteered for this prospective study. All patients had bilateral LASIK to correct myopia between -1.00 and -6.75 diopters (D) and refractive astigmatism less than 2.50 D. The mean spherical equivalent (SE) refractive error in the 68 eyes was -3.93 D +/- 1.67 (SD). A Hansatome microkeratome (Bausch & Lomb) and a Technolas 217C excimer laser (Bausch & Lomb) driven by the PlanoScan program were used. The monocular CSF for spatial frequencies of 3, 6, 12, and 18 cycles per degree (cpd) for both day and night vision simulations were made with a CSV-1000E system (Vector Vision) before and 1 month and up to 9 months after LASIK. All patients wore their best spectacle correction for the baseline CSF.

RESULTS

The group (n = 68) averaged preoperative and postoperative CSFs did not differ at 1 month (analysis of variance [ANOVA], P>.05). In a subgroup of 11 eyes that had corneal microstriae, however, there was a significant reduction in the photopic and mesopic CSF at 6, 12, and 18 cpd (ANOVA, P<.05) despite normal Snellen visual acuities. The CSF normalized in 6 to 9 months as the microstriae became less visible.

CONCLUSIONS

Subtle central corneal microstriae after LASIK can reduce the baseline CSF at medium to high spatial frequencies even with 20/20 visual acuity. The CSF normalizes as the microstriae fade over time.

Detection of neutrophils in late-onset interface inflammation associated with flap injury after laser in situ keratomileusis

OBJECTIVE

To report a case with late-onset interface inflammation associated with traumatic flap injury at 7 months after laser in situ keratomileusis (LASIK) and to describe the type of infiltrating cells in the tears of the patient.

METHODS

Interventional case report. A 24-year-old male patient who underwent uneventful LASIK on both eyes received blunt trauma from the tip of a shoe in the left eye 7 months after surgery. The corneal flap of his left eye was lacerated across the pupillary area. Inflammatory cells were observed under the lacerated flap segment. Tear fluid was collected from his left eye 3 days after the injury and assessed by tear cytology. For controls, tears of 2 patients who underwent LASIK and developed no interface inflammation were collected the next day after their surgeries and examined.

RESULTS

Tear fluid of the patient with interface inflammation contained numerous neutrophils. Tears of control patients contained only a few epithelial cells and cell debris but no inflammatory cells. The inflammation was decreased by systemic and topical steroids. However, irregular astigmatism caused by stromal scarring remained, resulting in decreased best-corrected visual acuity.

CONCLUSIONS

Interface inflammation can be caused by late-onset flap injury. Neutrophils detected in the tears may reflect a major component of cells infiltrating the interface after LASIK.

Prospective, Paired Comparison of Laser in situ Keratomileusis and Laser Epithelial Keratomileusis for Myopia Less Than -6.00 Diopters

PURPOSE

To compare visual and refractive results, contrast sensitivity, and tear stability after laser in situ keratomileusis (LASIK) in one eye and laser epithelial keratomileusis (LASEK) in the fellow eye for low myopia.

METHODS

Patients diagnosed with low myopia, with a maximum difference of 1 D between their two eyes, were randomly assigned to receive LASEK on one eye and LASIK on the other eye. A total of 64 eyes of 32 patients with a mean age of 26.83 +/- 5.33 years were included in the study. Preoperative myopia ranged from -1.00 to -6.00 D. Follow-up was 6 to 12 months. Uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA), Schirmer test results, tear break-up time, corneal asphericity, corneal uniformity index, predicted corneal acuity, and contrast sensitivity values were compared with preoperative values. A Wilcoxon test was used for statistical comparisons and a P-value less than .05 was considered significant.

RESULTS

At 6 months after surgery, there was no statistically significant difference in UCVA, BSCVA, spherical and cylindrical refractive error, Schirmer test, or tear break-up time between groups. Contrast sensitivity values in the LASIK eyes were lower in comparison to preoperative values, but there was no change in the LASEK group.

CONCLUSIONS

Based on 6-month results, LASEK for low myopia was safe and effective with predictable results, offered early refractive stability, and may be considered an alternative for LASIK.

Five-Year Follow-Up of Photorefractive Keratectomy for Myopia

PURPOSE

To analyze long-term results of photorefractive keratectomy (PRK) for myopia and myopic astigmatism.

METHODS

This retrospective study included 15 eyes of 8 patients who were examined annually for 5 years after PRK. The Nidek EC-5000 laser with an ablation zone of 5.0 mm was used. Evaluations included spherical equivalent manifest refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal haze, and corneal astigmatism calculated by Fourier analysis of videokeratography data.

RESULTS

A tendency toward myopic regression was most evident within the first postoperative year, with manifest refraction changing from +0.80 +/- 1.62 D at 1 week to -0.45 +/- 0.70 D at 1 year postoperatively (P = .007). Regression continued after the second postoperative year. There was a statistically significant difference between manifest refraction at 2 years (-0.36 +/- 0.75 D) and 5 years (-1.11 +/- 1.12 D) (P = .002). Postoperative UCVA stabilized from 3 months up to 3 years, but slightly deteriorated at 4 years and thereafter due to the myopic refractive shift. BSCVA remained stable throughout the 5-year follow-up period. Several eyes developed mild corneal haze after surgery, but haze was minimal in the majority of patients by 1 year and continued to fade over time. The asymmetry component of the cornea significantly increased after surgery, with all postoperative values significantly higher than before PRK (P < .05). Higher order irregularity increased after surgery, with a statistically significant difference between preoperative and 1 year postoperative (P < .05), but values after 2 years were not different from preoperative baseline.

CONCLUSION

Fifteen eyes with a baseline refraction of -3.00 to -9.00 D had PRK with the Nidek EC-5000 laser and a 5-mm-diameter ablation zone. Myopic regression occurred in the first year, with continued mild regression of approximately -0.75 D between 2 and 5 years. Nevertheless, the results show the procedure was relatively safe and effective in this group.

Ocular Surface Management of Photorefractive Keratectomy and Laser in situ Keratomileusis

PURPOSE

To examine the effects of keratorefractive surgery and ocular surface management on goblet cell density, dry eye symptom incidence, and spherical equivalent refraction.

METHODS

We performed a retrospective analysis of four myopia groups: Untreated controls (n = 53); PRK (n = 51); LASIK without ocular surface management (n = 56); LASIK with ocular surface management (n = 140). Ocular surface management involved the routine use of non-preserved artificial tears and other lubricants before, during, and after surgery. Lid hygiene procedures, topical anti-inflammatory agents, and punctal plugs were used on indication. Assessments were conducted before and up to 12 months after surgery (right eyes only in patients with both eyes operated, and in the left or right eye in patients with one eye operated).

RESULTS

Surgery caused a significant reduction in goblet cell density, with the greatest reduction in the LASIK without ocular surface management group. No significant differences were detected in dry eye symptoms or spherical equivalent refraction between PRK and LASIK without ocular surface management. Ocular surface management significantly minimized LASIK-induced decreases in goblet cell density and was associated with significantly less myopic outcomes at months 1 to 3 and 6 to 9 after LASIK. After surgery (1 to 3 mo), dry eye symptoms were significantly lower in the LASIK with ocular surface management group. In all groups, significant inverse correlations existed between goblet cell density and dry eye symptoms.

CONCLUSIONS

Ocular surface management minimized the negative impact of LASIK on goblet cell density and reduced dry eye symptoms. Without ocular surface management, goblet cell density and dry eye symptoms after LASIK were similar to or worse than after PRK.

Laser in situ Keratomileusis for Correction of Induced Astigmatism From Cataract Surgery

PURPOSE

To evaluate the efficacy, predictability, stability, and safety of laser in situ keratomileusis (LASIK) to correct residual astigmatism after cataract surgery.

METHODS

LASIK was performed on 20 eyes of 20 patients with refractive myopic or mixed astigmatism (3.00 to 6.00 D) at least 1 year after extracapsular cataract extraction with posterior chamber intraocular lens implantation without complication. Each eye received bitoric LASIK with the Nidek EC-5000 excimer laser and the Automated Corneal Shaper microkeratome.

RESULTS

At 6 months after LASIK, mean refractive cylinder decreased from 4.64+/-0.63 D to 0.44+/-0.24 D (P<.001). Mean percent reduction of astigmatism was 90.4+/-5.0% (range 80% to 100%). Mean spherical equivalent refraction decreased from -2.19+/-0.88 D (range -1.00 to -3.88 D) to -0.32+/-0.34 D (range -1.25 to +0.38 D) (P<.001). Vector analysis showed that the mean amount of axis deviation was 0.7+/-1.2 degrees (range 0 degrees to 4.3 degrees) and the mean percent correction of preoperative astigmatism was 92.1+/-5.9% (range 85.6% to 108%). Eighty-five percent of all eyes had a mean spherical equivalent refraction and mean cylinder within +/-0.50 D of emmetropia. Change in spherical equivalent refraction and cylinder from 2 weeks to 6 months was < or = 0.50 D in 90% (18 eyes) and 95% (19 eyes), respectively. Spectacle-corrected visual acuity was not reduced in any eye. Diffuse lamellar keratitis occurred in three eyes (15%) after LASIK, and were treated successfully with eyedrops.

CONCLUSION

LASIK was an effective, predictable, stable, and safe procedure for correction of residual myopic or mixed astigmatism ranging from 3.00 to 6.00 D with a low spherical component after cataract surgery.

Contact lens fitting following unsuccessful refractive surgery

A retrospective review of case notes of consecutive patients referred to a contact lens clinic after unsuccessful refractive surgery was carried out to determine the success of contact lens fitting. The main outcome variables in determining success were visual improvement, contact lens tolerance, fitting characteristics and wearing time. Thirteen eyes were fitted with conventional rigid gas permeable (CRGP), 10 with soft and 19 with reverse geometry rigid gas permeable contact lenses (RVG). The mean spectacle visual acuity (VA) was 6/9 (20/30) [range: 6/24 (20/80) to 6/5 (20/15)] and the mean VA after contact lens fitting was 6/6 (20/20) [range: 6/18 (20/60) to 6/5 (20/15)]. Of the 42 eyes, the contact lens VA was better than spectacle acuity in 25 (59.5%) eyes, equal in 14 (33.3%) and worse in three (7.1%). A total of 33 (78.6%) eyes were still wearing their lenses at the last visit. Contact lenses can be a valuable method of managing poor VA after refractive surgery.

Slitlamp stretching of the corneal flap after laser in situ keratomileusis to reduce corneal striae

PURPOSE

To examine the efficacy of treating immediate postoperative corneal striae and poor flap alignment by stretching the corneal flap at the slitlamp with a cotton-tip applicator and compare the results using this technique with those using the conventional technique of refloating the flap with balanced salt solution (BSS(R)).

SETTING

TLC Laser Eye Center, Garden City, New York, USA.

METHODS

Charts of 7154 eyes having laser in situ keratomileusis (LASIK) were reviewed retrospectively. During the 11 months prior to January 1, 2000, 3516 eyes had LASIK. Patients with flap striae or a malpositioned flap at the immediate slitlamp evaluation were treated by refloating the flap (Group A). During the 11 months subsequent to January 1, 2000, 3638 eyes had LASIK. Patients with flap striae or a malpositioned flap at the immediate slitlamp evaluation were treated by flap stretching with a cotton-tip applicator (Group B). The number of eyes that required retreatment for flap striae was analyzed.

RESULTS

Twenty-nine eyes in Group A (0.82%) required retreatment for visually significant flap striae after day 1, and 11 eyes in Group B (0.30%) required retreatment. A loss of best corrected visual acuity occurred in 3 Group A eyes and 2 Group B eyes.

CONCLUSIONS

During the immediate postoperative period, stretching the flap with a cotton-tip applicator was a simple, safe, and effective technique for reducing visually significant flap striae. Unlike refloating the flap with BSS, flap stretching at the slitlamp does not require additional anesthesia, exposure time, or dehydration of the ocular surface.

Laser Epithelial Keratomileusis: Outcome of Initial Cases Performed by an Experienced Surgeon

PURPOSE

To evaluate refractive outcome and objective clinical data, and determine efficacy, predictability, and safety of laser epithelial keratomileusis (LASEK) for myopic treatments.

METHODS

We performed a retrospective non-comparative single-surgeon case series on the first 20 LASEK procedures (Alcon LADARVision 4000 laser). Mean patient age was 41.2 years (range 21 to 60 yr): 13 men and 7 women. Mean preoperative spherical equivalent refraction was -6.47+/-2.78 D. Corneal haze, uncorrected and spectacle-corrected visual acuity and manifest refraction were evaluated.

RESULTS

Of 20 eyes studied, 3 were corrected for monovision. In the non-monovision group, 20/40 or better visual acuity was achieved in 94% (16 eyes) at 1 month, 100% (13 eyes) at 3 months, and 91% (10 eyes) at 6 months after LASEK; 20/20 or better was achieved in 12% (2 eyes) at 1 month, 46% (6 eyes) at 3 months, and 45% (5 eyes) at 6 months. Corneal haze at 1 month was grade 0.5 in 35% (7 eyes), 1 in 20% (4 eyes) and 2 in 10% (2 eyes). At 3 months, 62% (12 eyes) had grade 0.5 and 31% (6 eyes) had grade 1. At 6 months, 58% (12 eyes) had grade 0.5, 25% (5 eyes) had grade 1, and 8% (2 eyes) had grade 2.

CONCLUSIONS

LASEK is a challenging procedure. Creating the epithelial flap is not simple and may have contributed to the high haze incidence in our study.

Mesopic Contrast Sensitivity Function After Laser in situ Keratomileusis

PURPOSE

To evaluate contrast sensitivity under mesopic conditions in patients who have undergone uncomplicated bilateral laser in situ keratomileusis (LASIK) for myopia.

METHODS

Best-corrected monocular contrast sensitivity was measured with the Stereo Optical F.A.C.T. chart at 1.5, 3, 6, 12, and 18 c/deg in 20 patients (20 left eyes) before and after bilateral LASIK (with the Nidek EC-5000 excimer laser and the Automated Corneal Shaper). Mean preoperative refractive error was -6.40 +/- 1.28 D (range -4.00 to -8.00 D) and postoperative mean refractive error was -0.41 +/- 0.45 D (range -0.75 to +0.50 D). Contrast sensitivity function was measured before and 6 months after surgery using four different chart luminances: 85, 5, 2.5, and 0.1 cd/m2, the first being a photopic level and the rest mesopic. Log contrast sensitivity values at each spatial frequency were used for statistical analysis and normalized values for graphical representation.

RESULTS

Contrast sensitivity of postoperative LASIK eyes did not differ from preoperative values at a photopic level (85 cd/m2). However, under mesopic conditions (5 cd/m2 or less) a statistically significant reduction (P<.01) in contrast sensitivity was found at high spatial frequencies (12 and 18 c/deg), although no significant contrast sensitivity differences were observed at low and middle spatial frequencies (P>.01 for 1.5, 3 and 6 c/deg).

CONCLUSIONS

LASIK induced significant reductions in contrast sensitivity under mesopic conditions only at high spatial frequencies, even though the photopic contrast sensitivity function was normal.

Laser-assisted subepithelial keratectomy for myopia: two-year follow-up

PURPOSE

To assess and compare the clinical results (efficacy, safety, stability, and postoperative pain or discomfort) of laser-assisted subepithelial keratectomy (LASEK) and conventional photorefractive keratectomy (PRK) for the correction of low to moderate myopia.

SETTING

Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic.

METHODS

A prospective comparative study was performed in 184 eyes of 92 patients who had surface excimer ablation for the correction of myopia. The preoperative mean spherical equivalent (MSE) was -4.65 diopters (D) +/- 3.14 (SD) (range -1.75 to -7.50 D). In each patient, LASEK was performed in 1 eye and PRK in the fellow eye by the same surgeon. The first eye treated and the surgical method used in the first eye were randomized. Both procedures were performed with the Nidek EC-5000 excimer laser using the same parameters and nomogram. The postoperative pain level, visual recovery, complications (haze), uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and refractive outcome were evaluated and compared. All eyes completed a 24-month follow-up.

RESULTS

The postoperative MSE was -0.18 +/- 0.53 D in the PRK eyes and -0.33 +/- 0.46 D in the LASEK eyes. At 1 week, the mean UCVA was 0.64 +/- 0.21 and 0.87 +/- 0.23, respectively. No LASEK eye lost a line of BSCVA. There were no statistically significant differences between PRK and LASEK eyes in the safety and efficacy indices at 2 years. The mean pain level was significantly lower on days 1 to 3 in the LASEK eyes (P <.05). The mean corneal haze level was lower in the LASEK eyes (0.21) than in the PRK eyes (0.43) (P <.05). Seventy-nine patients preferred LASEK to PRK.

CONCLUSIONS

Laser-assisted subepithelial keratectomy provided significantly quicker visual recovery, eliminated post-PRK pain, and reduced the haze level in eyes with low to moderate myopia compared with conventional PRK. It provided good visual and refractive outcomes. There were no serious complications.

Intrastromal corneal ring implantation for the correction of myopia: 12-month follow-up

PURPOSE

To evaluate the efficacy, predictability, and stability of refraction obtained after intrastromal corneal ring segment (ICRS) implantation for low to moderate myopia.

SETTING

Single-center clinical practice.

METHODS

In this prospective 2-surgeon study, 9 patients (15 eyes) with low to moderate myopia were recruited to receive ICRS implants.

RESULTS

At 1 day, 10 of the 15 eyes had an uncorrected visual acuity (UCVA) of 20/40 or better. At 12 months, all eyes had this UCVA and 66.6% had 20/25 or better. The mean manifest refraction stabilized after the first week at <-0.5 diopter (D). At 12 months, all eyes were within +/-1.0 D of the intended manifest refraction; 67% were within +/-0.5 D. Sixty percent of eyes had no change from the preoperative best corrected visual acuity; 13.3% improved by 1 line, and 26.6% lost 1 line. The postoperative complications included lamellar channel deposits (n = 12), ICRS dislocation (n = 2), corneal infiltrates (n = 2), bleeding in the positioning ring hole (n = 1), 0.3 mm segment decentration (n = 1), and prolonged wound healing (n = 1).

CONCLUSIONS

Intrastromal corneal ring segment implantation for the correction of low to moderate myopia afforded good visual recovery and efficacy similar to that with laser in situ keratomileusis and superior to that with photorefractive keratectomy. However, light or blunt trauma and insufficient hygiene can have serious consequences and there is the potential for induced astigmatism. Corneal infiltrates can occur and must be treated immediately. The ring implantation technique is demanding. Advantages of ICRS implantation include rapid and stable visual recovery as well as reversibility.

Night vision disturbances after corneal refractive surgery

A certain percentage of patients complain of "glare" at night after undergoing a refractive surgical procedure. When patients speak of glare they are, technically, describing a decrease in quality of vision secondary to glare disability, decreased contrast sensitivity, and image degradations, or more succinctly, "night vision disturbances." The definitions, differences, and methods of measurement of such vision disturbances after refractive surgery are described in our article. In most cases of corneal refractive surgery, there is a significant increase in vision disturbances immediately following the procedure. The majority of patients improve between 6 months to 1 year post-surgery. The relation between pupil size and the optical clear zone are most important in minimizing these disturbances in RK. In PRK and LASIK, pupil size and the ablation diameter size and location are the major factors involved. Treatment options for disabling glare are also discussed. With the exponential increase of patients having refractive surgery, the increase of patients complaining of scotopic or mesopic vision disturbances may become a major public health issue in the near future. Currently, however, there are no gold-standard clinical tests available to measure glare disability, contrast sensitivity, or image degradations. Standardization is essential for objective measurement and follow-up to further our understanding of the effects of these surgeries on the optical system and thus, hopefully, allow for modification of our techniques to decrease or eliminate post-refractive vision disturbances.