Photorefractive keratectomy. A 6-year follow-up study

Long-Term Outcomes of Refractive Surgery Performed During the Military

INTRODUCTION

To evaluate the long-term refractive results of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) performed by the military in a veteran population.

MATERIALS AND METHODS

Three Department of Veterans Affairs (VA) hospital sites (Puget Sound, Buffalo, and Washington D.C.) obtained IRB approval for this multi-center study. Comprehensive ophthalmologic assessment including refraction and keratometry were obtained at the time of the long-term VA examination and compared to the patients' postoperative military records.

RESULTS

Eighty patients (160 eyes) enrolled in this study. At the time of treatment, patients were 21-52 years of age. Long-term post-operative data was available from 4 to 17 years post-operatively. Fifteen percent of the treatment types were LASIK and 85% PRK. At the time of their military post-operative exam (range 3-14 months, mean 4 months), 82% of patients had uncorrected visual acuity (UCVA) of 20/20 or better, and their average manifest refraction was -0.08 D (SD ± 0.48 D). At the time of the long-term ophthalmological exam at the VA medical centers (range 4-11 years, mean of 8.2 years), 49% of patients had an UCVA of 20/20 or better and an average manifest refraction was -0.64 D (SD ± 0.69 D).

CONCLUSION

This is the first long-term study evaluating refractive surgery outcomes up to 17 years in a military population. Our study demonstrates safety after refractive surgery in the military with less than 0.1D increase in myopia per year and strong keratometric stability. Other changes in the eye may be the likely cause for this observed mild refractive shift.

Analysis of the Pathogenic Factors and Management of Dry Eye in Ocular Surface Disorders

The tear film represents the interface between the eye and the environment. The alteration of the delicate balance that regulates the secretion and distribution of the tear film determines the dry eye (DE) syndrome. Despite having a multifactorial origin, the main risk factors are female gender and advanced age. Likewise, morphological changes in several glands and in the chemical composition of their secretions, such as proteins, mucins, lipidics, aqueous tears, and salinity, are highly relevant factors that maintain a steady ocular surface. Another key factor of recurrence and onset of the disease is the presence of local and/or systemic inflammation that involves the ocular surface. DE syndrome is one of the most commonly encountered diseases in clinical practice, and many other causes related to daily life and the increase in average life expectancy will contribute to its onset. This review will consider the disorders of the ocular surface that give rise to such a widespread pathology. At the end, the most recent therapeutic options for the management of DE will be briefly discussed according to the specific underlying pathology.

Four-year Follow-up of the Changes in Anterior Segment After Phakic Collamer Lens Implantation

PURPOSE

To assess the changes and relationship in central vaulting, flare intensity, and crystalline lens thickness during a follow-up period of 4 years after implantable collamer lens (ICL) implantation in eyes with high myopia.

DESIGN

Retrospective observational study.

METHODS

Ninety-eight eyes of 50 patients were followed up with routine measurements of central vaulting, crystalline lens thickness, endothelial cell density, and aqueous flare postoperatively. Data were analyzed by repeated-measures analysis of variance. The relationship between the annual change in crystal lens thickness after surgery and age was evaluated by Pearson correlation coefficient and linear regression.

RESULTS

There was a continuous reduction in central vaulting and endothelial cell density as well as an increase in crystalline lens thickness in ICL eyes from 1 month onward to 5 years postoperatively (P < .001). Although the trend of variation during the individual visit period was accentuated, the variation turned out to be smaller between 12 and 36 months or 60 months postoperatively (P = .42, P = .65). Aqueous flare intensity increased significantly after surgery and returned to normal 1 year later. Additionally, a positive correlation between patient age and crystalline lens thickness (r = 0.617, P < .0001) was observed in eyes with ICL implantation.

CONCLUSIONS

The changes in central vaulting, endothelial cell density, and crystalline lens thickness are more prominent during the first year after ICL implantation, tending to be relatively stable afterwards. The anterior inflammation during the early postoperative period synchronizes with the sharp progression of crystalline lens changes within the first year.

Fifteen years follow-up of photorefractive keratectomy up to 10 D of myopia: outcomes and analysis of the refractive regression

PURPOSE

To evaluate outcomes of photorefractive keratectomy up to -10.00 D of myopia and -4.50 of astigmatism and to develop a predictive model for the refractive changes in the long term.

SETTING

Vissum Corporation and Miguel Hernandez University (Alicante, Spain).

DESIGN

Retrospective-prospective observational series of cases.

METHODS

This study included 33 eyes of 33 patients aged 46.79±7.04 years (range 40-57) operated with the VISX 20/20 excimer laser with optical zones of 6 mm. No mitomycin C was used in any of these cases. The minimum follow-up was 15 years. The main outcome measures were: uncorrected and corrected distance visual acuity, manifest refraction and corneal topography. Linear regression models were developed from the observed refractive changes over time.

RESULTS

Safety and efficacy indexes at 15 years were 1.18 and 0.83, respectively. No statistically significant differences were detected for any keratometric variable during the follow-up (p≥0.103). 15 years after the surgery 54.55% of the eyes were within ±1.00 D of spherical equivalent and 84.85% within ±2.00 D. The uncorrected distance visual acuity at 15 years was 20/25 or better in 60.6% of the eyes and 20/40 or better in 72.73% of the eyes. The correlation between the attempted and the achieved refractions was r=0.948 (p<0.001) at 1 year, and r=0.821 (p<0.001) at 15 years. No corneal ectasia was detected in any case during the follow-up.

CONCLUSIONS

Photorefractive keratectomy is a safe refractive procedure in the long term within the range of myopia currently considered suitable for its use, although its efficacy decreases with time, especially, in high myopia. The model developed predicts a myopic regression of 2.00 D at 15 years for an ablation depth of 130 µm.

Four-year visual outcomes after photorefractive keratectomy in pilots with low-moderate myopia

BACKGROUND

The photorefractive keratectomy (PRK) is approved for Air Force pilots in several nations. The occupational environments of pilots in the Air Force are unique, including extremely high altitude, low oxygen tension, high ultraviolet light exposure and high G-force load. The short-term efficacy and safety of PRK for pilots are documented. However, the study for long-term visual and refractive outcomes of PRK in pilots is limited.

OBJECTIVE

To investigate the long-term visual and refractive outcomes in a 4-year follow-up period after PRK in pilots with low to moderate myopia.

METHODS

Thirty-eight eyes of 20 subjects that underwent PRK and recruited to Air Force pilot were evaluated preoperatively and at 3, 6, 12, 24, and 48 months postoperatively.

RESULTS

The mean patient age was 21.42±0.75 years. The mean preoperative manifest refraction spherical equivalent (SE) was -1.51±1.15 diopters (D). At 4 years postoperatively, the mean SE was -0.29±0.51, 89.5% of eyes achieved 20/20 or better Snellen uncorrected visual acuity, 71.1% of eyes were within ±0.50 D of emmetropia. The refraction stabilised by 6 months and was maintained up to the 4-year follow-up stage.

CONCLUSIONS

PRK for pilots with low to moderate myopia is safe and effective in the long term. High-altitude environmental stress exposure has no effect on the refractive stability after PRK.

TRIAL REGISTRATION NUMBER

ROKAF-ASMC-2015-IRB-002.

Outcome of posterior chamber phakic intraocular lens procedure to correct myopia

PURPOSE

To assess the safety and efficacy of the implantable contact lens (ICL™) to treat myopia.

DESIGN

Clinical, retrospective, single center, non-randomized case series.

PARTICIPANTS

Sixty-nine eyes of 46 patients with myopia ranging from -3.00 to 25.00 D were included in this study.

INTERVENTION

Implantation of the ICL™.

MAIN OUTCOME MEASURES

Uncorrected Visual Acuity (UCVA), refraction, best spectacle corrected visual acuity (BSCVA), adverse events, operative and postoperative complications, subjective assessment and symptoms.

RESULTS

The mean follow-up was 12.35 ± 6.13 (SD) months (range, 6 months-32 months). At the last visit, 49.20% of eyes had 20/20 or better UCVA compared to preoperative 20/20 or better BSCVA of 31.9% of eyes; 69.23% of eyes had postoperative UCVA better than or equal to preoperative BSCVA. The mean manifest refractive cylinder was 1.93 ± 1.21 D at baseline and 1.00 ± 0.92 D postoperatively. The mean manifest refraction spherical equivalent (MRSE) was -11.70 ± 4.24 D preoperatively and -0.69 ± 1.13 D postoperatively. A total of 69.8% of eyes were within ±0.5 D of the predicted MRSE; 84.1% were within ±1.0 D, and 88.90% were within ±2.0 D. BSCVA of 20/20 or better was achieved in 64.6% of eyes postoperatively, compared to 31.9% preoperatively. Mean improvement in BSCVA was 1line. One eye (1.5%) lost ⩾2 lines of BSCVA at the last visit, whereas 20% of eyes improved by ⩾2 lines. A total of 56.92% of cases gained ⩾1 line of BSCVA and 4.62% of cases lost ⩾1 line. Four ICL lenses were removed without significant loss of BSCVA, and 2 eyes with clinically significant lens opacities were observed. Four eyes (5.8%) developed a pupillary block the first day postoperatively. One eye (1.4%) developed a hypotony and AC shallowing.

CONCLUSION

Implantation of ICL for the correction of myopia was a safe procedure with good visual and refractive results from the early postoperative period to 1 year. Long-term follow-up is required to confirm the long-term safety of this implant.

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.

Photorefractive keratectomy and butterfly laser epithelial keratomileusis: a prospective, contralateral study

PURPOSE

To evaluate results of two surface excimer laser refractive surgery techniques--photorefractive keratectomy (PRK) and butterfly laser epithelial keratomileusis (butterfly LASEK).

METHODS

A prospective, randomized, double-masked study of 51 patients (102 eyes) who underwent laser refractive surgery. One eye of each patient was randomized to be operated with PRK and the fellow eye with butterfly LASEK. Patients were followed for 1 year.

RESULTS

No significant difference between groups for distance uncorrected visual acuity (UCVA) (P = .559) was noted. At 1 year, 98% (50 eyes) in the PRK group and 96.1% (49 eyes) in the butterfly LASEK group reached UCVA of 20/20. Predictability, efficacy, safety, and stability were not statistically significant between groups. Safety index was 1.0 for PRK and 0.996 for butterfly LASEK. One eye in the butterfly LASEK group lost one line of best-spectacle corrected visual acuity. At 12 months, 94.1% (48 eyes) and 86.3% (44 eyes) in the PRK and butterfly LASEK groups (P = .188), respectively, had a spherical equivalent refraction of +/- 0.50 diopters. Slight haze was observed in both groups. A statistical difference in haze between the groups was observed only in the first postoperative month, with higher intensity in the butterfly LASEK group (0.18 +/- 0.39) compared to the PRK group (0.08+/- 0.21) (P = .04).

CONCLUSIONS

Butterfly LASEK had similar predictability, efficacy, safety, stability, and haze incidence to PRK for the treatment of low to moderate myopia. However, on the second postoperative day, PRK showed better UCVA than butterfly LASEK.

Ten-year follow-up of photorefractive keratectomy for myopia of less than -6 diopters

PURPOSE

To evaluate the long-term outcomes of excimer laser myopic photorefractive keratectomy (PRK) for myopia of less than -6 diopters (D).

DESIGN

Long-term (10-year) follow-up retrospective, interventional case series.

METHODS

The study included 225 eyes of 138 myopic patients with spherical equivalent (SE) between 0 and -6 D treated with myopic PRK at the Instituto Oftalmológico de Alicante, Alicante, Spain, using the VISX 20/20 excimer laser (Santa Clara, California, USA). The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications.

RESULTS

At 10 years, 169 (75%) of 225 eyes were within +/- 1.00 D and 207 (92%) were within +/- 2.00 D. Ninety-five (42%) eyes underwent retreatments because of overcorrection, regression, or both. The mean SE slightly decreased (myopic regression) with a mean magnitude of -0.10 +/- 1.08 D over 10 years (-0.01 +/- 0.11 D per year). Forty-one (58%) of 225 eyes demonstrated increase in best spectacle-corrected visual acuity after 10 years. Only one eye lost eight lines because of significant cataract, and two eyes lost vision (one lost seven lines and the other lost four lines) because of posterior segment-related complications. The mean corneal haze score gradually decreased from 0.22 +/- 0.39 at three months to 0.01 +/- 0.09 at 10 years.

CONCLUSIONS

Photorefractive keratectomy for myopia of less than -6 D is a safe and effective procedure in the long-term.

Ten-year follow-up of photorefractive keratectomy for myopia of more than -6 diopters

PURPOSE

To evaluate the long-term outcomes of excimer laser myopic photorefractive keratectomy (PRK) for myopia higher than -6 diopters (D).

DESIGN

A long-term (10-year) follow-up retrospective, interventional case series.

METHODS

The study included 267 eyes of 191 patients with myopia with spherical equivalent (SE) of more than -6 D treated with myopic PRK at the Instituto Oftalmológico de Alicante, Alicante, Spain, using the VISX 20/20 excimer laser (Santa Clara, California, USA). All patients were evaluated three months, one year, two years, five years, and 10 years after surgery. The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications.

RESULTS

At 10 years, 156 (58%) of 267 eyes were within +/- 1.00 D and 209 (78%) were within +/- 2.00 D. One hundred and twenty-four eyes (46.4%) underwent retreatments because of overcorrection, regression, or both. The mean SE decreased (myopic regression) in eyes that did not undergo retreatment, with a mean magnitude of -1.33 +/- 2.0 D over 10 years (-1.13 +/- 0.20 D per year). One hundred and twenty-one (48.3%) of 267 eyes demonstrated increase in best spectacle-corrected visual acuity, and only eight eyes lost lines of vision because of cataract and posterior segment-related complications. The mean corneal haze score decreased gradually from 0.48 +/- 0.69 at three months to 0.09 +/- 0.33 at 10 years.

CONCLUSIONS

PRK for myopia of more than -6 D is a safe and effective procedure in the long-term.

Improvement of Visual Acuity Following Refractive Surgery for Myopia and Myopic Anisometropia

PURPOSE

To test the hypothesis that anisometropic adults without significant amblyopia suffer from mild visual impairment probably due to aniseikonia, which might be improved by corneal refractive surgery.

METHODS

Fifty-seven patients presenting with myopic anisometropia > or = 3.25 diopters (D) and 174 myopic controls appropriate for refractive surgery were included. Photorefractive keratectomy (PRK) or LASIK was performed on 57 anisometropic eyes. As 43 of the 174 myopic control patients had bilateral surgery, PRK or LASIK was performed on 217 myopic control eyes. Best spectacle-corrected visual acuity (BSCVA), refraction, and refractive correction were measured preoperatively and at 1, 3, 5 to 7, 8 to 13, and 25 months following surgery.

RESULTS

Preoperative mean spherical equivalent was -7.20 +/- 2.40 D for anisometropic patients and -6.40 +/- 1.90 D for myopic patients. At 8 to 13 months postoperatively, when 23 (40%) anisometropic eyes and 94 (43%) myopic eyes were examined, the mean spherical equivalent refractions were -0.80 +/- 1.60 D and -0.30 +/- 0.60 D, respectively. Preoperatively, the mean BSCVA on a logMAR scale was -0.0143 +/- 0.0572 (Snellen 0.98 +/- 0.12) in the anisometropic group and 0.0136 +/- 0.0361 (Snellen 1.04 +/- 0.09) in the control group (P = .001). Eight to 13 months postoperatively, these values were 0.0076 +/- 0.0659 (Snellen 1.03 +/- 0.15) and 0.0495 +/- 0.0692 (Snellen 1.13 +/- 0.18) and this difference remained statistically significant (P = .012). For the myopic patients, the improvement in BSCVA reached almost maximum at 3 months, and this improvement was found to be highly significant 3 months after surgery (P = .001). The improvement in BSCVA was significantly slower for anisometropic patients and became statistically significant only after 8 to 13 months postoperatively (P = .041).

CONCLUSIONS

Anisometropia reduces visual acuity in the more myopic eye and can be at least partially reversed by refractive correction. The slower improvement in BSCVA for anisometropic patients suggests plastic changes in the visual cortex following refractive surgery.

Laser Epithelial Keratomileusis for the Correction of Hyperopia Using a 7.0-mm Optical Zone With the Schwind ESIRIS Laser

PURPOSE

To investigate the efficacy of laser epithelial keratomileusis (LASEK) for the correction of hyperopia using a 7.0-mm optical zone and a 9.0-mm total ablation zone diameter with the Schwind ESIRIS flying-spot laser.

METHODS

Forty-seven patients (70 eyes) were treated with a mean preoperative spherical equivalent refraction of +2.32 diopters (D) (range: 0 to +5.00 D). All eyes underwent LASEK using 15% alcohol with a 20-second application.

RESULTS

An intact epithelial flap was obtained in 66 (94%) eyes. In 70 eyes at 12 months, the mean spherical equivalent refraction was +0.09 D (range: -0.75 to +1.00 D) with all (100%) eyes within +/- 1.00 D of the intended correction and 60 (86%) eyes within +/- 0.50 D. In 40 eyes with 24-month follow-up, the refractive correction remained stable after 6 months. Hyperopic cylindrical corrections were attempted in 49 eyes (range: +0.25 to +5.00 D) with vector analysis demonstrating a mean 102% correction at 12 to 24 months. In 60 non-amblyopic eyes, uncorrected visual acuity was > or = 20/20 in 47 (78%) eyes. Thirty-three (47%) eyes gained 1 to 2 lines of Snellen decimal equivalent best spectacle-corrected visual acuity, 30 (43%) eyes showed no change, and 7 (10%) eyes lost 1 line. Eight (11%) eyes at 12 to 24 months had grade +/- 1 of paracentral corneal haze and 57 (81%) had no haze. At 12 months (n = 70), the safety index was 1.06 with an efficacy index of 0.95. Analysis of higher order wavefront aberrations showed no significant changes in root-mean-square values post-operatively, except for a significant reduction of fourth order spherical aberration (P < .05).

CONCLUSIONS

Laser epithelial keratomileusis for hyperopia up to +5.00 D using a 7.0-mm optical zone with the Schwind ESIRIS laser provides excellent refractive and visual outcomes with minimal complications. In eyes followed for 24 months, the refractive correction remained stable after 6 months.

Cellular effects of mitomycin-C on human corneas after photorefractive keratectomy

PURPOSE

To investigate the effects of mitomycin-C (MMC) on epithelial and keratocyte cell kinetics after photorefractive keratectomy (PRK) using an in vitro human cornea model.

SETTING

Department of Academic Ophthalmology, Rayne Institute, St. Thomas' Hospital, London, United Kingdom.

METHODS

Twenty-four human eye-bank corneas were placed in a specially designed acrylic corneal holder and cultured using the air-interface organ culture technique for up to 4 weeks. The corneas were divided into 3 groups. Group 1 consisted of 8 human corneas that had -9.00 diopter (D) myopic PRK without MMC application. Group 2 consisted of 8 corneas that had -9.00 D PRK with MMC (0.2 microg/mL) application for 1 minute on the stromal surface after ablation. Group 3 consisted of 8 corneas that had -9.00 D PRK with 2-minute exposure to MMC (0.2 microg/mL). Temporal events in epithelial and keratocyte cell kinetics were evaluated using digital imaging, confocal microscopy, and light microscopy.

RESULTS

Epithelial latency was significantly delayed with MMC application in Groups 2 and 3 (P<.001). Epithelial migration was delayed in Group 3 (2-minute exposure) compared to migration in Group 2 (P<.04), with a consequent delay in epithelial closure (P<.001). Group 3 corneas had poorly differentiated epithelium that was significantly thinner than in Groups 1 and 2 (P<.0001). A significant delay in keratocyte regeneration occurred after MMC application (P<.0005). At 4 weeks, the anterior stromal cell density was significantly lower in Group 3 than Group 2 (P<.001). There were no significant differences in the mid- and posterior stromal keratocyte density between the groups.

CONCLUSIONS

Results suggest that epithelial healing after MMC is characterized by prolonged latency and decreased migration rate dependent on exposure time. Mitomycin C application did not result in increased loss of keratocytes, but it significantly delayed keratocyte repopulation in the anterior stroma. The use of MMC 0.2 microg/mL for 1 minute resulted in optimum modulation of healing characterized by reduced keratocyte activation with normal epithelial differentiation.

Twelve-year Follow-up of Photorefractive Keratectomy for Low to Moderate Myopia

PURPOSE

To evaluate long-term safety and stability in a group of myopic patients who underwent photorefractive keratectomy (PRK) > or =12 years ago.

METHODS

Myopic PRK was performed on 120 eyes of 80 patients using the Summit UV200 excimer laser with a 5-mm ablation zone. Of the original group, most of whom were followed for > or =2 years (mean 2.6 +/- 1.7 years), 34 patients (58 eyes) returned at 12 years (mean 12.7 +/- 0.79 years) and had refractive stability, refractive predictability, best spectacle-corrected visual acuity (BSCVA), corneal haze, and subjective patient symptoms, such as glare/halos, recorded.

RESULTS

Preoperative mean refractive spherical equivalent (MRSE) ranged from -1.75 to -7.25 diopters (D) and astigmatism from 0.00 to 1.50 D. All eyes underwent a change in manifest refraction over 12 years. At 2 years, MRSE was -0.27 +/- 0.55 D and at 12 years was -0.58 +/- 0.72 D. In 87.9% of eyes, the level of preoperative BSCVA was maintained or improved, whereas 34.5% of eyes gained one line, and 12.1% lost one line of BSCVA. Uncorrected visual acuity > or = 20/20 was noted in 67% of eyes, whereas 62.1% were within +/- 0.50 D of emmetropia. Trace haze was noted in 17.2% of eyes at 12 years. One patient had a rhegmatogenous retinal detachment, but this was unlikely due to the PRK procedure. With respect to the small optical zone, 14 (41.1%) patients had night visual problems, particularly halos, which were severe in 2.7%. All patients questioned stated they would have the procedure done again.

CONCLUSIONS

Photorefractive keratectomy with the Summit UV200 excimer laser effectively reduced myopia and showed good refractive stability from year 2 to 12 with good patient satisfaction.

Effects of ablation diameter on long-term refractive stability and corneal transparency after photorefractive keratectomy

OBJECTIVE

To evaluate the effects of ablation diameter on long-term refractive stability and corneal transparency after photorefractive keratectomy (PRK).

DESIGN

Long-term, prospective, follow-up study.

PARTICIPANTS

One hundred twenty-three eyes treated between 1990 and 1993 at one institution as part of a number of ethical committee-approved clinical studies underwent long-term follow-up at 10 to 12 years after PRK.

INTERVENTION

Photorefractive keratectomy was performed using the Summit Technology UV 200 and OmniMed Excimer lasers with either 4.0-mm (n = 36), 5.0-mm (n = 47), or 6.0-mm (n = 40) optical zones and either -3.0-diopters (D) or -6.0-D myopic spherical corrections, based on the original Munnerlyn algorithms.

MAIN OUTCOME MEASURES

Refractive stability, refractive predictability, best spectacle-corrected visual acuity, and corneal haze.

RESULTS

Refractive outcome at 1 and 10 to 12 years of follow-up was better with 6.0-mm treatments, especially for -6.0-D corrections (P>0.001). The early hyperopic shift was significantly reduced with 6.0-mm zones, with less regression between 1 and 6 months, compared with 5.0- and 4.00-mm PRK, especially for -6.0-D corrections (P<0.001). The postoperative refraction remained stable between 1 and 10 to 12 years in all groups. Objective measurements of haze were less with 6.0-mm compared with 4.0- and 5.0-mm treatments (P<0.001). Night vision problems were significantly less with 6.0-mm PRK (P<0.01). There was no evidence of progressive hyperopic shift, corneal ectasia, or late onset of corneal haze in any of the eyes during the follow-up period.

CONCLUSIONS

Refractive stability was maintained between 1 year and 10 to 12 years after PRK with 4.0-, 5.0-, and 6.0-mm optical zones. A significant linear trend was observed in terms of refractive predictability, early hyperopic shift, regression, corneal transparency, and night haloes with better outcomes in PRK with a larger ablation zone. None of the eyes had sight-threatening complications such as ectasia or late-onset corneal haze during the follow-up.

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.

Laser Subepithelial Keratomileusis for the Correction of High Myopia With the Schwind ESIRIS Scanning Spot Laser

PURPOSE

To investigate the efficacy of laser subepithelial keratomileusis (LASEK) for the correction of high myopia with the Schwind ESIRIS scanning spot laser (Schwind eye-tech-solutions Gmbh & Co, Kleinostheim, Germany).

METHODS

Fifty-one patients (76 eyes) were treated with a mean preoperative spherical equivalent refraction of -7.55 diopters (D) (range: -6.0 to -10.75 D). All eyes received a LASEK technique using 15% alcohol with a 20-second application.

RESULTS

An intact epithelial flap was obtained in 73 (96%) eyes. At 1 week, uncorrected visual acuity (UCVA) was > or =20/30 in 53 (70%) eyes and > or =20/60 in all eyes. At 6 months (n=76), the mean SE was +0.08 D (range: -1.00 to +1.875 D) with 73 (96%) eyes within +/-1.0 D of the intended correction and 60 (79%) eyes within +/-0.5 D. At 12 months (n=46), the mean SE was -0.07 D (range: -1.375 to +2.0 D) with 44 (96%) eyes within +/-1.0 D of the intended correction and 37 (80%) eyes within +/-0.5 D. Myopic cylindrical corrections were attempted in 68 eyes (range: -0.25 to -4.25 D) with vector analysis demonstrating a mean 85% correction. At last follow-up, UCVA was > or =20/20 in 47 (62%) eyes, > or =20/25 in 63 (83%) eyes, and > or =20/40 in 75 (99%) eyes. Three (4%) eyes gained two lines of Snellen decimal equivalent best spectacle-corrected visual acuity compared to preoperative levels, 68 (89%) eyes showed no change or gained one line, and 5 (7%) eyes lost one line. None lost more than one line. Only 2 (3%) eyes at 6 to 12 months had more than +1 axial corneal haze and 50 (66%) showed no evidence of haze on slit-lamp examination.

CONCLUSIONS

Laser subepithelial keratomileusis for myopia up to -11.00 D with the Schwind ESIRIS laser provides good refractive and visual outcomes, with acceptable visual recovery and minimal complications.

Response of the Cornea for up to Four Years After Photorefractive Keratectomy for Myopia

PURPOSE

To analyze the long-term corneal topographic changes 4 years after myopic photorefractive keratectomy (PRK).

METHODS

This study comprised 15 patients (30 eyes) who had PRK surgery with a scanning-spot excimer laser (Chiron Technolas 217C; Bausch & Lomb, Dornach, Germany) and were followed up to 4 years after surgery. The eyes were subdivided into three groups according to the preoperative spherical equivalent refraction. Corneal topographic maps were obtained for all eyes with a Placido disc topographer. Preoperative and follow-up topographical data were imported into a custom software program, which computed the average composite corneal maps and difference maps for each study group to quantify the anterior corneal changes following laser ablation. The software delineated three concentric zones of the corneal surface to characterize the regional corneal remodeling following the surgery.

RESULTS

A significant central corneal steepening (approximately 0.25 D, P < .001) was calculated between the 1- and 4-year postoperative maps in all study groups. A significant steepening (P < .001) of the corneal periphery was also noted for the lower myopic ablations whereas a peripheral flattening (P < .001) was observed for the deeper ablations between 1 and 4 years after surgery.

CONCLUSIONS

The anterior corneal surface was observed to remodel for up to 4 years after surface ablation, steepening a mean of approximately 0.25 D.

A return to primitive practice? Radial keratotomy revisited

Recently, a refractive surgeon was quoted in the national and professional press as proposing that radial keratotomy (RK) is to be preferred over laser procedures, such as photorefractive keratectomy (PRK) and laser assisted in situ keratomileusis (LASIK). The rationale for this public recommendation was that the RK procedure achieves better visual results and fewer complications than the laser procedures. Peer reviewed literature on these refractive procedures was surveyed to establish the validity of such a statement and it was found that current data do not support the notion that RK results in better visual outcomes than PRK and LASIK The true incidence of complications is difficult to establish. However, when the post procedure chronic effects are compared between RK, PRK and LA SIK, it becomes apparent that the post-RK patient pays the highest price, by a large margin, in visual quality impairment and corneal health. Although the visual acuity outcomes for low to moderate myopes, when corrected by any of the three refractive procedures considered here, are not dramatically different, we concluded that RK is not the preferred methodology because of its associated chronic visual and corneal health complications.

Pharmacological management of night vision disturbances after refractive surgery

PURPOSE

To evaluate the efficacy and safety of diluted aceclidine eyedrops in reducing night vision disturbances after refractive surgery.

SETTING

Department of Ophthalmology, Istituto Clinico Humanitas, Rozzano-Milano, Italy.

METHODS

This double-masked randomized clinical trial included 30 patients (60 eyes) with chronic night vision disturbance after refractive surgery. Patients were randomly allocated to receive (1) placebo, (2) aceclidine 0.016%, or (3) aceclidine 0.032%. Drugs were administered once or twice daily. Anterior segment, haze, uncorrected visual acuity, best corrected visual acuity, intraocular pressure, corneal maps, and scotopic pupil size were determined at baseline and at follow-up examinations (15 and 30 days after inclusion). Halos and double vision 4-step scales were built to determine subjective grading of night vision disturbance, and the root mean square (RMS) was calculated to determine objective changes in night vision disturbance.

RESULTS

The effect of diluted aceclidine started about 15 minutes after instillation and lasted for about 5 hours. No difference between the 2 dilutions could be found. Thirty-nine of 40 treated eyes showed a reduction in night vision disturbance. The mean reduction in halos and double vision grading was 1.42 +/- 0.5 (SD) and 1.14 +/- 0.4, respectively. A mean decrease in pupil size of 2.5 mm was measured. Thirty minutes after the instillation of diluted aceclidine, the topography-derived wavefront error showed a statistically significant reduction in RMS values (total, spherical, astigmatic, coma, and higher order), which was maintained for 5 hours. A transitory conjunctival hyperemia was the only side effect reported.

CONCLUSION

Diluted aceclidine seemed to be an effective and safe treatment for night vision disturbance following refractive surgery.

In vitro human corneal model to investigate stromal epithelial interactions following refractive surgery

PURPOSE

To develop an in vitro human corneal model to evaluate stromal epithelial interactions following corneal refractive surgical procedures.

SETTING

Department of Academic Ophthalmology, Rayne Institute, St. Thomas' Hospital, London, United Kingdom.

METHODS

Fifty-six human donor corneas procured from the eye bank were placed in a specially designed acrylic corneal holder and were cultured using the air-interface organ culture technique for up to 4 weeks. Corneal refractive surgical procedures such as a simple epithelial defect, 4 diopter (D) and 9 D photorefractive keratectomy (PRK), 4 D and 9 D laser-assisted subepithelial keratectomy (LASEK), and 9 D laser in situ keratomileusis (LASIK) were performed on the model. Temporal events in epithelial and keratocyte cell kinetics were evaluated using digital imaging, confocal microscopy, and light microscopy. Two-way analysis of variance and Student t tests were used to assess statistical significance.

RESULTS

Epithelial healing following PRK was completed by 92 hours +/- 10 (SD) at a rate of 0.58 +/- 0.45 mm2/hour. In LASEK, the epithelial flap was replaced by regenerating peripheral epithelium that showed significant delay in epithelial closure (120 +/- 5 hours) with prolonged latency (24 +/- 4 hours, P<.0001) in comparison with PRK. The magnitude of keratocyte loss corresponded to ablation depth, and keratocyte regeneration was dependent on epithelial closure. In comparison, LASIK corneas showed a lesser percentage of keratocyte loss with poor recovery of keratocyte density in the stromal flap. Epithelial viability and keratocyte density were well preserved in the in vitro human model as observed in control corneas for up to 4 weeks.

CONCLUSIONS

The temporal events in stromal epithelial interactions in the in vitro human model closely mimicked in vivo observations. The human model further avoided species-specific variations and provided a suitable test bed for evaluating newer algorithms and therapeutic regimens following refractive surgery.

Excimer laser photorefractive keratectomy for hyperopia: 7.5-year follow-up

PURPOSE

To report the results of a long-term prospective study to evaluate refractive stability and safety of hyperopic photorefractive keratectomy (H-PRK).

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

Twenty-one patients (49%) (40 eyes) of cohort of 43 patients who participated in 1 of the first clinical trials of H-PRK were assessed at a mean follow-up of 90.7 months (range 62 to 106 months). The H-PRK was performed using a Summit Technology Apex Plus Excimer laser (Summit Technology, Inc.). The mean preoperative spherical equivalent refraction (SEQ) was +4.70 diopters (D) (range +2.00 to +7.50 D). Patients were allocated to 1 of 4 treatment groups based on their preoperative refraction and received 1 of the following spherical corrections: +1.50 D, +3.00 D, +4.50 D, or +6.00 D.

RESULTS

At 7.5 years, the refractive correction remained stable with a mean difference in SEQ between 1 year and 7.5 years of +0.28 D. The mean manifest SEQ was +0.83 D (range +5.00 to -3.00 D). Sixty-seven percent of eyes having corrections of +1.50 D and +3.00 D were within +/-1.00 D of the predicted correction. Predictability was poorer with +4.50 D and +6.00 D corrections, with 40% of eyes within +/-1.00 D of that expected. An improvement in uncorrected near acuity was achieved in 35 eyes (87.5%), and 35 eyes (87.5%) showed an improvement in uncorrected distance acuity from preoperative levels. Best spectacle-corrected visual acuity (BSCVA) was unchanged or improved from preoperative values in 25 eyes (62.5%). Three eyes (8%) lost 2 lines of Snellen BSCVA, which in 2 cases was attributable to cataract formation. A peripheral ring of haze, 6.5 mm in diameter, appeared in most eyes. Its intensity was greatest at 6 months and then diminished with time. In 10 eyes (25%), remnants of the haze ring were evident at 7.5 years and subepithelial iron rings, 6.5 mm in diameter were evident in 26 eyes (70%). No patient complained of night-vision problems and no eye developed ectasia.

CONCLUSIONS

In H-PRK, refractive stability achieved at 1 year was maintained up to 7.5 years with no evidence of hyperopic shift, diurnal fluctuation, or late regression. Peripheral corneal haze decreased with time but was still evident in a number of eyes at the last follow-up visit.

5-year follow-up of LASIK for hyperopia

PURPOSE

To assess the long-term efficacy and stability of LASIK for hyperopia (+0.75 to +7.00 diopters [D]).

DESIGN

Retrospective follow-up study of a previous phase III multicenter clinical trial (unpublished data).

PARTICIPANTS

Patients who had been treated for hyperopia (33 individuals, 47 eyes) attended follow-up 5 years after surgery. The preoperative mean spherical equivalent at the spectacle plane was +3.58 D (range, +0.75 to 7.00 D), and the attempted mean spherical correction at the corneal plane was +3.18 D (range, +1.00 to +6.00 D).

INTERVENTION

Treatments were performed using a Moria LSK One microkeratome and a Summit Technology SVS Apex Plus excimer laser fitted with an Axicon.

MAIN OUTCOME MEASURES

Manifest refraction, uncorrected visual acuity, best spectacle-corrected visual acuity, corneal transparency, complications, and patient satisfaction were recorded.

RESULTS

At 5 years, for treatments between +1.00 to +3.00 D, 71.0% of eyes were within +/-1.00 D of the intended correction, and for treatments between +3.5 to +6.0 D, 37.5% of eyes were within +/-1.00 D of intended correction. From 12 to 54 months after surgery for all patients, there was a hyperopic shift of +0.53 D (range, -0.13 to +3.13 D), with 51.1% of eyes experiencing an increase of +0.50 D or more and 27.7% of eyes showing a hyperopic shift of more than +1.00 D. This hyperopic shift was +0.67 D (range, 0 to +1.125 D) for patients younger than 40 years of age and +0.44 D (range, -1.33 to +1.50 D) for patients between 43 and 55 years of age.

CONCLUSIONS

LASIK was moderately effective for the correction of low degrees of hyperopia. However, there was regression throughout the 5-year follow-up that was greater than would be expected as a result of aging. Long-term stability of hyperopic LASIK refractive corrections, therefore, is uncertain.

A long-term study of photorefractive keratectomy; 12-year follow-up

OBJECTIVE

To evaluate long-term refractive stability of excimer laser myopic photorefractive keratectomy (PRK).

DESIGN

A long-term (12 years) prospective follow-up study.

PARTICIPANTS

Sixty-eight patients (56.6%) of the original cohort of 120 who participated in the first United Kingdom excimer laser clinical trial underwent detailed clinical assessment at 12 years after myopic PRK.

INTERVENTION

Myopic PRK was performed using the Summit Technology UV 200 excimer laser with a 4-mm ablation zone. Patients were allocated to 1 of 6 treatment groups based on their preoperative refraction. Each group received one of the following spherical corrections: -2, -3, -4, -5, -6, or -7 diopters (D). Patients in each group received an identical treatment, and therefore, emmetropia was not the primary aim.

MAIN OUTCOME MEASURES

Refractive stability, refractive predictability, best spectacle-corrected visual acuity (BSCVA), and corneal haze.

RESULTS

The postoperative refraction remained stable at 12 years, with no significant change in mean spherical equivalent refraction between 1, 6, and 12 years. Seventy-five percent of patients who underwent a -2-D correction and 65% of patients who received a -3-D correction were within 1 D of intended correction at 12 years. Fifty-seven percent of the -4-D group and 50% of the -5-D group were within 1 D, and this was further reduced to 25% and 22% in the -6-D and -7-D groups, respectively. Four percent had residual corneal haze, and 12% had persistent nighttime halos at 12 years. Dry eyes were encountered in 3% of patients, and none of the eyes developed corneal ectasia in the long term.

CONCLUSIONS

In myopic PRK, refractive stability achieved at 1 year was maintained up to 12 years with no evidence of hyperopic shift, diurnal fluctuation, or late regression in the long term. Corneal haze decreased with time, with complete recovery of BSCVA. Night halos remained a significant problem in a subset of patients due to the small ablation zone size.

Effect of exogenous keratinocyte growth factor on corneal epithelial migration after photorefractive keratectomy

PURPOSE

To investigate the effect of topical keratinocyte growth factor (KGF) on wound healing after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, Rayne Institute, St. Thomas' Hospital, London, United Kingdom, St. Erick's Eye Hospital, Stockholm, Sweden, and the University of Regensberg, Regensberg, Germany.

METHODS

In a placebo-controlled trial, 24 New Zealand white female rabbits were divided into 3 equal groups. Group 1 (n=8) had myopic PRK (6.0 diopters [D]) using the Technolas 217z laser (Bausch & Lomb). Group 2 and Group 3 had myopic LASIK (6.0 D) with a flap depth of 140 microm and 180 microm, respectively. Topical KGF (20 microg/mL) was administered to half the treated eyes in each group intraoperatively and postoperatively; the other half received placebo eyedrops. Epithelial closure, corneal haze, and keratocyte activation in the rabbit eyes were analyzed and compared with those in placebo-controlled eyes for 5 weeks postoperatively.

RESULTS

In Group 1, the mean reepithelialization after PRK was 0.10 mm2/h +/- 0.02 (SD) in the KGF group and 0.33 +/- 0.05 mm2/h in the control group (P=.001). There was no significant difference in the mean backscatter between the KGF eyes (154 +/- 45.95) and the control eyes (141 +/- 38.45) after PRK (P=.42). Histology revealed reduced epithelial cell layers in the KGF group and comparable keratocyte density as in the control group. In Groups 2 and 3, there was no significant difference in backscatter, epithelial layers, and keratocyte density between KGF and control eyes after LASIK.

CONCLUSIONS

Topical KGF (20 microg/mL) delayed reepithelialization after PRK. It had no effect on stromal wound healing in LASIK eyes with an intact epithelial barrier.

Eight-year Follow-up of Photorefractive Keratectomy for Myopia

PURPOSE

We evaluated 8-year results of excimer laser photorefractive keratectomy (PRK) for myopia in terms of stability and late complications.

METHODS

Ninety-two myopic eyes of 55 patients were treated with a single-step method using an Aesculap-Meditec MEL 60 excimer laser with a 5.0-mm ablation zone. Treated eyes were divided into three groups according to preoperative refraction: low myopes (< or = -6.00 D), medium myopes (-6.10 to -10.00 D), and high myopes (>-10.00 D).

RESULTS

Change in myopic regression stabilized in all myopia groups within 12 months, although a small myopic shift occurred up to 8 years after PRK. Mean change in refraction between 2 and 8 years was -0.42 +/- 0.48 D for low myopes, -0.37 +/- 0.34 D for medium myopes, and -0.41 +/- 0.50 D for high myopes. The percentage of eyes within +/- 1.00 D of emmetropia 8 years after PRK was 78.3% in the low myopia group, 68.8% in the medium myopia group, and 57.1% in the high myopia group. One eye lost 2 lines of best spectacle-corrected visual acuity due to irregular astigmatism. In 13.0% of eyes, a residual trace corneal haze was observed, which had no effect on visual acuity. Apart from the loss of 2 lines of BSCVA in one eye, there were no other late complications during the study period.

CONCLUSIONS

The mean change in refraction between 2 and 8 years was less than -0.50 D, regardless of preoperative refraction, and may be attributed to natural age-related refractive change. The appearance of residual corneal haze after 8 years correlated with the amount of myopic correction. PRK was a safe and stable surgical procedure in this group of patients.

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.

Risk factors for night vision complaints after LASIK for myopia

PURPOSE

To study the preoperative risk factors for night vision complaints (NVCs) after LASIK in a clinical setting.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Seven hundred ninety-five patients (1488 eyes) who underwent LASIK for myopia up to -9.75 diopters (D) (from January 1 to December 31, 1999).

SETTING

Private clinic.

METHODS

A complete preoperative examination was performed. Patients had bilateral LASIK surgery using the Nidek EC-5000 non-wavefront guided slit-scanning excimer laser and the Moria LSK One microkeratome. Patients were observed postoperatively for 12 months.

MAIN OUTCOME MEASURES

The reported NVCs for each eye were rated on a subjective scale based on functional visual comfort. Clinically important NVC odds ratios (ORs) were calculated.

RESULTS

Reports of NVCs decreased considerably from 25.6% at 1 month to 4.7% at 12 months postoperatively, at which time all patients reported similar NVCs in both eyes. Stratification of risk factors at 12 months postoperatively showed a 2.8-times increase in NVCs for initial myopia of >5 D, a 2.5-times increase for an optical zone of </=6.0 mm, and a 2.9-times increase for a postoperative spherical equivalent outside +/-0.5 D of emmetropia. The role of attempted spherical correction, age of the patient, and postoperative spherical equivalent had significant importance in logistic regression of the OR throughout the first postoperative year. In a stepwise logistic regression using 6- and 12-month data, attempted spherical correction and optical zone were the most predictive factors of NVCs (P<0.001). Pupil size at any month postoperatively was not statistically predictive of postoperative NVCs in any differential model involving it.

CONCLUSIONS

Attempted degree of spherical correction, age, optical zone, and postoperative spherical equivalent were major risk factors of NVCs throughout the first postoperative year, whereas pupil size was not. Future wavefront studies that characterize higher order aberrations might be helpful for understanding individual visual aberrations while predicting quality of vision.

Fourier analysis of induced irregular astigmatism

PURPOSE

To analyze corneal topographic data by Fourier analysis to determine differences in irregular astigmatism following spherical hyperopic correction by photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

Thirty-six eyes of 18 patients with moderate hyperopia had LASIK in 1 eye and PRK in the other eye. The flap was cut on a nasal hinge with a Moria LSK One microkeratome. The laser was a Summit SVS Apex Plus with an optical zone of 6.5 mm and a blending zone of 1.5 mm. Corneal topographic data were acquired with a TMS-1 topographer (Computed Anatomy Inc.) preoperatively and 1, 3, 6, and 12 months postoperatively. The ASCII files containing the dioptric power values were extracted and analyzed with custom-written software to extract the Fourier harmonics.

RESULTS

The irregular astigmatism increased in both groups postoperatively, peaking at 3 months and then decreasing over the next 9 months. There was no statistically significant difference between the 2 groups at any time point (P<.05). The change in the topographically derived equivalent sphere showed undercorrection in both groups at all time points. Regular astigmatism showed a marginal statistically significant increase in the LASIK group at 12 months (P =.049).

CONCLUSION

Irregular astigmatism, equivalent sphere, and regular astigmatism were not significantly different in the PRK and LASIK groups during the follow-up. Based on the corneal topography, the 2 procedures induced an equal amount of irregular astigmatism.

Six-year follow-up of laser in situ keratomileusis for moderate and extreme myopia using a first-generation excimer laser and microkeratome

PURPOSE

To evaluate objectively and subjectively the long-term outcome of laser in situ keratomileusis (LASIK) in patients with high and very high myopia.

SETTING

Department of Ophthalmology, Philipps University, Marburg, Germany.

METHODS

Thirty-three eyes of 19 patients were followed for a mean of 76 months (range 50 to 84 months) after primary LASIK using the Keratom I excimer laser (Schwind) and the ALK microkeratome (Chiron). Refraction, glare, pachymetry, corneal topography, and tear-film secretion and stability were measured. At the last examination, patients also answered a 14-item questionnaire.

RESULTS

Preoperatively, the mean spherical equivalent was -13.65 diopters (D). At 1 year, it was -0.25 D and after 6 years, -0.88 D. Fifteen percent of eyes lost > or =2 lines of best spectacle-corrected visual acuity (BSCVA), and 9% gained > or =2 Snellen lines. At the end of the study, 46% of eyes were within +/-1.0 D of the attempted corrected and 88% were within +/-3.0 D. There were 5 microkeratome-associated complications; 3 resulted in loss of BSCVA. The latest pachymetry showed a mean corneal thickness of 498.5 microm (range 396 to 552 microm). There were no cases of keratectasia. Seventy-five percent of patients noted an increase in their quality of life. Seventy-one percent were satisfied with their postoperative visual acuity; however, 75% noticed glare and halos at night.

CONCLUSIONS

Laser in situ keratomileusis correction of very high myopia did not cause keratectasia in the long term provided the corneal thickness was respected. A flap thickness setting of 130 microm with a first-generation microkeratome resulted in a high number of cut failures. Most patients were happy with the results despite a modest level of accuracy and glare.

Persistent Haze and Disorganization of Anterior Stromal Collagen Appear Unrelated Following Phototherapeutic Keratectomy

PURPOSE

The theoretical effects on corneal transparency induced by changes in collagen fibril packing following phototherapeutic keratectomy were compared to changes in objective measurements of haze.

METHODS

Phototherapeutic keratectomy was performed on the right eyes of four young rabbits; left eyes were used as controls. Postoperative slit-lamp measurements of haze were taken at regular intervals up to 19 months. Wounded stromas were studied by synchrotron x-ray diffraction to calculate the average interfibrillar spacing of the collagen fibrils. These data were combined with transmission electron microscope measurements, and the summation of scattered fields method was used to predict the transmission of visible light.

RESULTS

Objective measurements of haze were higher than the baseline control throughout the study. Electron micrographs of anterior stroma in 8-month-old wounds displayed irregularly spaced and poorly organized fibrils and x-ray diffraction indicated larger mean interfibrillar spacing compared to the controls. However, the predicted transmission of visible light through the anterior stromal scar tissue was not significantly different than normal.

CONCLUSIONS

Following phototherapeutic keratectomy, anterior corneal collagen fibrils were more widely spaced and unevenly organized than in the normal rabbit cornea. However, this did not cause a significant loss of transparency and was therefore unlikely to contribute to haze.

Cytotoxic and Mutagenic Action of 193-nm and 213-nm Laser Radiation

PURPOSE

To compare the cytotoxic and mutagenic effect of 213-nm and 193-nm laser radiation on cultured mammalian cells.

METHODS

Chinese hamster lung (V79) cells were exposed to 193-nm radiation from an argon fluorine excimer laser or 213-nm radiation from a 5th harmonic Nd:YAG laser. The cytotoxic action of the lasers was compared by determining the number of V79 cell colonies that formed 1 week after irradiating cells with different doses of 193-nm or 213-nm laser radiation or with continuous wave 254-nm radiation. The cytotoxic action of the lasers on primary cultures of human corneal fibroblasts was also compared. The mutagenic potential of the lasers was compared by measuring the number of ouabain or 6-Thioguanine(6TG)-resistant V79 mutants that formed after exposing V79 cells to 193-nm or 213-nm radiation.

RESULTS

The dose of 193-nm laser radiation that resulted in 37% survival (D37) of V79 cells was estimated to be 11.3 mJ/cm2 compared to 3.2 mJ/cm2 for 213-nm laser radiation and 1.2 mJ/cm2 for 254-nm UV radiation. The mean number of ouabain-induced mutants induced at the D37 for 193-nm, 213-nm, and 254-nm laser radiation were 28, 166, and 279 mutants/10(7) cells, respectively. Continuous wave 254-nm radiation induced 6TG-resistant colonies, but there was no significant induction of 6TG-resistant mutants by either laser.

CONCLUSIONS

Although the in vitro data presented herein may or may not be meaningful to humans, the 213-nm Nd:YAG laser was more cytotoxic and mutagenic than the 193-nm excimer laser on cultured mammalian cells but was less cytotoxic and mutagenic than 254-nm radiation.

Removal of INTACS for myopia

OBJECTIVE

To evaluate the safety and efficacy of the removal of INTACS.

DESIGN

Subgroup analysis from a nonrandomized comparative interventional trial.

PARTICIPANTS

Four hundred fifty-two patients with best spectacle-corrected visual acuity of 20/20 or better and myopia (1.0-3.5 diopters [D]) were enrolled in the U.S. Food and Drug Administration clinical trials of INTACS. Forty-six eyes among a total of 684 underwent INTACS removal.

INTERVENTION

INTACS removal.

METHODS

Safety and efficacy of INTACS removal was assessed by comparison of results from preoperative and 3-month postremoval visits. Safety was assessed by maintenance of preoperative best spectacle-corrected acuity and induction of astigmatism (measured by manifest refraction). Efficacy was assessed by comparison of mean spherical equivalent measured by both manifest and cycloplegic refraction, as well as percentage of eyes within +/- 0.5 D and +/- 1.0 D of baseline values. A subset of 27 patients completed a prospective questionnaire assessing the frequency of six visual symptoms (glare, halos, double vision, photophobia, night vision difficulties, and fluctuating vision).

MAIN OUTCOMES MEASURES

Best spectacle-corrected visual acuity, manifest refraction, and cycloplegic refraction.

RESULTS

Forty-one of 46 patients' eyes that had undergone INTACS removal had reached the 3-month postremoval visit. Of these eyes, 73% (30 of 41) had returned to within +/- 0.5 D and 97% (40 of 41) to within +/- 1.0 D of baseline spherical equivalent as measured by manifest refraction. With respect to astigmatism, 88% (36 of 41) had returned to within +/- 0.5 D and 100% (41 of 41) to within +/- 1.0 D of preoperative value. No patient had a loss of best spectacle-corrected acuity of more than 2 lines, with equal numbers of eyes having a loss or gain of 1 line (nine eyes) and 2 lines (one eye). For most eyes, INTACS removal was associated with a substantial reduction in the six types of visual symptoms; however, in some eyes (up to 15%) symptoms that had not been detected preoperatively were noted after INTACS removal.

CONCLUSIONS

INTACS removal was not associated with a loss (> 2 lines) of best spectacle-corrected visual acuity or induction (> 1 D) of astigmatism or myopia. INTACS removal was associated with a reversal to preoperative values in most cases.

Corneal haze after photorefractive keratectomy for myopia: role of collagen IV mRNA typing as a predictor of haze

PURPOSE

To develop a test based on the individual expression of collagen type IV synthesis in corneal epithelial cells to identify patients who have the potential for significant corneal haze after myopic photorefractive keratectomy (PRK).

SETTING

Department of Ophthalmology and the Institute of Microbiology, University of Regensburg, Germany.

METHODS

The individual synthesis of collagen type IV alpha3 mRNA was quantitatively measured in corneal epithelial cells of 34 eye (34 patients) with myopia ranging from -1.5 to -10.0 diopters (D) by a polymerase chain reaction (PCR) test. The corneal epithelial cells were collected before the PRK procedure. Collagen type IV alpha3 mRNA levels were correlated to postoperative haze and regression at 12 months.

RESULTS

In all samples, collagen type IV alpha3 mRNA was detected; the mean was 1.47 (range 0.11 to 6.42). There was a correlation between haze and the amount of collagen type IV alpha3 mRNA; that is, eyes with haze had more collagen IV expression. In contrast, no correlation was observed between regression and the amount of collagen type IV alpha3 mRNA.

CONCLUSIONS

The results show that collagen type IV alpha3 is an important factor in the development of corneal haze after PRK. Based on a quantitative PCR test, the individual collagen IV mRNA concentration in corneal epithelial cells could be measured. Further development could establish a screening test by which eyes with pronounced synthesis of collagen IV could be identified as being at high risk for haze after PRK.

Laser-assisted subepithelial keratectomy versus photorefractive keratectomy for the correction of myopia. A prospective comparative study

PURPOSE

To compare the early postoperative visual rehabilitation after laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for the correction of myopia.

SETTING

CODET Aris Vision Institute, Tijuana, Mexico.

METHODS

This prospective study included 50 eyes of 25 patients with myopia who received LASEK in 1 eye and PRK in the contralateral eye. Excimer laser corneal ablation was done using the Nidek EC-5000 excimer laser. Patients were seen at 1 and 3 days, 1 week, and 1 month. Discomfort, subjective uncorrected visual acuity (UCVA), objective UCVA, best corrected visual acuity (BCVA), corneal clarity (haze), and time for corneal reepithelialization were analyzed.

RESULTS

Seventy-two percent and 80% of the LASEK eyes had more discomfort at 1 day and 3 days, respectively. Eighty percent and 96% of the PRK eyes had better subjective UCVA at 1 day and 3 days, respectively. Corneas were fully reepithelialized at a mean of 3.3 days +/- 0.5 (SD) and 3.6 +/- 0.5 days in the PRK and LASEK groups, respectively. At 1 month, the UCVA was similar in both groups; no eye had lost lines of BCVA or developed haze.

CONCLUSIONS

Both LASEK and PRK were effective and safe procedures in the surgical correction of myopia at the 1-month postoperative visit. Patients reported less discomfort and better visual acuity in their PRK eye during the early postoperative period. Patients should be informed that LASEK, whose acronym is similar to that of laser in situ keratomileusis, has a recovery speed that is similar to that of surface laser refractive procedures such as PRK.

Comparison of photorefractive keratectomy, astigmatic PRK, laser in situ keratomileusis, and astigmatic LASIK in the treatment of myopia

PURPOSE

To determine factors affecting refractive and visual outcomes in patients treated with astigmatic and spherical photorefractive keratectomy (A-PRK and PRK) and laser in situ keratomileusis (A-LASIK and LASIK).

SETTING

University referral refractive surgery clinic.

METHODS

Refractive and visual acuity results in 619 eyes of 388 consecutive patients having refractive surgery over a 2-year period by a single surgeon were retrospectively analyzed. Patients were divided into mild-to-moderate myopia (spherical equivalent [SE] less than -6.12 diopters [D]) and high myopia (SE -6.12 D or higher). Multivariate and logistic regression analyses were performed.

RESULTS

Refractive results in flap-based and PRK-based procedures were comparable in mild-to-moderate myopia patients but were significantly better in high-myopia patients having flap-based procedures. Refractive stability was greater in flap-based procedures than in PRK-based procedures. Elliptical ablations yielded a marked reduction in the astigmatic cylinder in patients having A-LASIK and A-PRK, while spherical PRK induced small amounts of with-the-rule astigmatism. Complications were uncommon in both groups, consisting primarily of epithelial ingrowth in flap-based procedures and haze in PRK-based procedures. Multivariate regression identified the preoperative SE as a significant determinant of PRK outcomes (with higher success for lower myopia) and intraocular pressure as a minor determinant of outcomes in PRK-based and flap-based procedures. Logistic regression suggested that only the preoperative SE was a significant factor in predicting the likelihood of poor outcomes in PRK patients.

CONCLUSIONS

Refractive outcomes were almost identical in patients having elliptical or spherical ablations with flap-based or PRK-based procedures. In eyes with mild-to-moderate myopia, there was little difference in refractive or visual outcomes between flap-based and PRK-based procedures; in eyes with high myopia, flap-based procedures offered more predictable refractive outcomes and better visual outcomes.

Implantable contact lens for high myopia

PURPOSE

To evaluate the efficacy, safety, and biocompatibility of a collagen polymer implantable contact lens (ICL) (Staar Collamer) as a posterior chamber phakic intraocular lens (IOL) to correct high myopia.

SETTING

Departments of Ophthalmology, Helsinki University Central Hospital, Helsinki, and Tampere University Hospital, Tampere, Finland.

METHODS

A Staar Collamer posterior chamber phakic IOL was implanted in 38 eyes of 22 patients with a mean age of 39 years (range 24 to 54 years). The mean preoperative myopia was -15.10 diopters (D) (range -7.75 to -29.00 D). Surgical implantation was performed through a 3.0 mm clear corneal sutureless incision using paraocular anesthesia. The patients were followed clinically up to 3 years. The mean follow-up was 13.6 months (range 6 to 24 months) for refractive data and 22.3 months (range 6 to 35 months) for complications. The possible inflammatory response to the ICL was measured using a laser flare meter in 12 eyes.

RESULTS

Postoperatively, all eyes had a significant increase in uncorrected visual acuity, allowing all but 3 patients (5 eyes) to manage most activities without spectacles. The mean spherical equivalent refraction at the last examination was -2.00 D +/- 2.48 (SD) (range +0.13 to -13.00 D), within +/-1.00 D of the targeted refraction in 31 eyes (81.6%) and within +/-0.50 D in 27 eyes (71.1%). In eyes in which the preoperative myopia was less than -18.00 D (n = 28), the achieved refraction was within +/-1.00 D of the intended refraction in 27 eyes (96.4%) and within +/-0.50 D in 24 eyes (85.7%). The refraction remained stable with a statistically insignificant change (P >.05) at each interval during the follow-up. The best corrected visual acuity (BCVA) improved by 1 or more lines in 23 of 32 eyes (71.9%) at 1 year. Two eyes (6.3%) lost 1 line of BCVA. Laser flare photometry showed normal aqueous flare values (11.71 +/- 6.61 photon counts/ms) in the 12 eyes measured at least 6 months after ICL implantation. Pupillary block glaucoma requiring surgical intervention occurred in 3 patients (7.9%). One patient (2.6%) developed cataract 1.5 years after ICL implantation; both ICLs were removed, and the refractive errors were corrected by lensectomy and implantation of low-power posterior chamber IOLs. One patient (2.6%) showed progression of dry macular degeneration at 17 months.

CONCLUSION

At 1 year, ICL implantation had good visual and refractive results with excellent biocompatibility. Long-term follow-up is required to confirm that significant complications do not occur in most patients over time.

Relationships between vitreoretinal and refractive surgery

OBJECTIVE

To describe retinal complications after posterior chamber phakic intraocular lens (PCPIOL) implantation and refractive surgery complications after scleral buckling surgery.

DESIGN

Retrospective, noncomparative, small case series.

PARTICIPANTS

Four patients in whom retinal detachment developed after PCPIOL implantation and two patients with previously placed encircling scleral buckles in whom corneal steepening developed after laser in situ keratomileusis (LASIK).

INTERVENTION

The four patients with retinal detachment after PCPIOL implantation underwent vitreoretinal surgery. One of the two patients in whom corneal steepening developed after LASIK underwent buckle removal.

MAIN OUTCOME MEASURES

The main parameters evaluated were vitreoretinal findings, corneal topography, and pachymetry.

RESULTS

Retinal attachment was achieved for all patients. Mean postoperative best-corrected visual acuity (BCVA) was 20/30. One patient lost one line of BCVA. One patient with corneal steepening achieved partial corneal flattening after buckle removal.

CONCLUSIONS

Vitreous base stimulation related to PCPIOL implantation and manipulation during LASIK may trigger retinal complications. Laser in situ keratomileusis in patients with previously placed scleral buckles may result in unexpected corneal steepening.

The specific architecture of the anterior stroma accounts for maintenance of corneal curvature

AIM

To analyse the human corneal stroma in extreme hydration to discover if its structure is responsible for corneal stability.

METHODS

Corneas in several hydration states were used: postmortem control corneas (PM; n=3), corneas left for 1 day in phosphate buffered saline (PBS; n=4), and corneas left for 1 day (n=4), 2 days (n=4), 3 days (n=2), and 4 days (n=4) in deionised water. All corneas were fixed under standardised conditions and processed for light and electron microscopy. In addition, two fresh corneas from the operating theatre were studied which were processed 6 months after storage in sodium cacodylate buffer.

RESULTS

After 1 day in deionised water maximal stromal swelling was reached which did not change up to 4 days. The stroma of deionised water corneas (1400 microm) was much thicker than that of PBS corneas (650 microm) and PM corneas (450 microm). Deionised water treatment led to disappearance of all keratocytes leaving only remnants of nuclei and large interlamellar spaces. In these specimens the distance between the collagen fibres had increased significantly, but the diameter of the collagen fibres did not seem to be affected. A remarkable observation was that the most anterior part of the stroma (100-120 microm) in all deionised water specimens and those stored for 6 months in buffer was not swollen, indicating that the tightly interwoven anterior lamellae are resistant to extreme non-physiological hydration states.

CONCLUSIONS

The rigidity of the most anterior part of the corneal stroma in extreme hydration states points to an important role in maintenance of corneal curvature. Since a large part of this rigid anterior part of the stroma is either removed (PRK) or intersected (LASIK), it is possible that in the long run patients who underwent refractive surgery may be confronted with optical problems.

Long-term results of multizone photorefractive keratectomy for myopia of -6.0 to -10.0 diopters

PURPOSE

To evaluate the 4 year refractive outcome of multizone photorefractive keratectomy (PRK) in eyes with high myopia.

SETTING

++SSK Okmeydani Education Hospital, Eye Clinic, Türkiye Hospital, Okmeydani, Istanbul.

METHODS

Three ablation zones were used in 92 eyes of 48 patients whose refractive errors were between -6.0 and -10.0 diopters (D) (mean spherical equivalent -7.42 D +/- 1.25 [SD]). The zones were between 4.5 and 6.0 mm based on the thickness of the cornea and the refractive correction. After the epithelium healed, dexamethasone was applied 4 times a day during the first postoperative week and then fluorometholone was applied 4 times a day for a minimum of 4 weeks. If hyperopia was found post-PRK, the steroid dose was gradually tapered. The patients were examined 1 and 3 days postoperatively, 1, 2, and 4 weeks, every 3 months for the first year, and then every 6 months.

RESULTS

All patients were overcorrected in the first postoperative week. At 2 and 3 weeks, the mean manifest refraction was closer to emmetropia. At 6 months, the refraction was stable. The mean spherical equivalent was -0.10 D at the end of the first year, and stabilization continued for 4 years. After the third month, the haze regressed gradually without requiring treatment. In 1 patient, herpes simplex keratitis developed and healed in a short time with topical antiviral therapy. Nineteen eyes regressed more than -1.0 D, 4 eyes were overcorrected, 4 eyes had central islands (at 6 months), and 2 eyes were undercorrected. Two eyes were retreated for regression; 1 eye was retreated for undercorrection and 1 eye, for central island. An uncorrected visual acuity of 20/40 or better was achieved in 79.2% of eyes, and 73.9% were within +/-1. 0 D of the intended correction.

CONCLUSION

++Photorefractive keratectomy was effective in treating high myopia between -6.0 and -10.0 D. The induced refractive changes stabilized between 6 and 9 months. In most patients, no significant regression was found after this period.

Theoretical analysis of ablation depths and profiles in laser in situ keratomileusis for compound hyperopic and mixed astigmatism

PURPOSE

To compare the theoretical ablation depths and profiles of 4 treatment strategies for compound hyperopic and mixed astigmatism.

SETTING

Theoretical analysis.

METHODS

Corneal contour drawings of theoretical corneal ablation profiles during laser in situ keratomileusis (LASIK) and photoastigmatic refractive keratectomy were made. The depths of tissue ablation in 4 treatment strategies for compound hyperopic astigmatism (Groups 1 to 4) and for mixed astigmatism (Groups 5 to 8) were compared: (1) combined hyperopic spherical and myopic cylindrical treatments (Groups 1 and 5); (2) combined spherical and hyperopic cylindrical treatments (Groups 2 and 6); (3) combined cylindrical treatments (Groups 3 and 7); (4) combined cross-cylinder and spherical equivalent treatments (Groups 4 and 8).

RESULTS

In compound hyperopic astigmatism, the 4 approaches resulted in identical final curvatures, but the ablation depths were greatest in Group 1 (combined hyperopic spherical and myopic cylindrical treatments). The smallest amount of ablation occurred in Group 2 (combined hyperopic spherical and hyperopic cylindrical treatments) and Group 3 (combined hyperopic cylindrical treatments), which had similar tissue ablation patterns. In mixed astigmatism, the greatest ablation depth was in Group 5, followed by Group 8, and Groups 6 and 7. The tissue ablation depths and profiles were similar in Groups 6 and 7.

CONCLUSION

The treatment approaches in Groups 2, 3, 6, and 7 (which avoided the use of minus cylinder) resulted in the smallest degree of stromal ablation. Patients with compound hyperopic or mixed astigmatism may benefit from reduced ablation depths by deferring treatment until hyperopic cylindrical and/or combined cylindrical treatments are available.

Diurnal stability of refraction after implantation with intracorneal ring segments

PURPOSE

To investigate diurnal changes in visual acuity and refraction in myopic eyes implanted with intracorneal ring segments (ICRS).

SETTING

University of California San Diego Shiley Eye Center, La Jolla, California, and Emory University Vision Correction Center, Atlanta, Georgia, USA.

METHODS

This prospective study involved 2 groups of patients who had ICRS (Intacs) implantation and a follow-up of at least 6 months. The first group included 102 eyes of 51 bilaterally treated patients; the second group, 32 eyes of 16 unilaterally treated patients. Examinations including visual acuity, manifest refraction, and videokeratography were done in the morning and evening at least 9 hours apart on a single day. Refractive changes were analyzed by power vectors; multivariate statistics were used to determine the significance of change in any component of the spectacle prescription.

RESULTS

In the bilateral treatment group, 97 eyes (95%) were within 1 line of spectacle-corrected visual acuity from morning to evening. The mean change in manifest refraction was -0.14 +0.08 x 4 and in spherical equivalent, -0.10 diopters (D) (sigma = 0.3; range -0.750 to +0.875 D). Ninety-six eyes (94%) had a change in refraction within 0.50 D of spherical equivalent. There was no significant change in corneal power (P =.20). In the unilateral treatment group, there was no significant difference between treated and untreated eyes in changes in spectacle-corrected visual acuity, manifest refraction, or corneal power and toricity (P.05).

CONCLUSION

No clinically significant diurnal variation in visual acuity or manifest refraction was observed after ICRS implantation or in untreated paired eyes. Moreover, the data suggest less diurnal change in visual acuity and refraction after ICRS implantation.

Surgical outcomes of photorefractive keratectomy and laser in situ keratomileusis by inexperienced surgeons

PURPOSE

To investigate the results of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) procedures performed by novice ophthalmologists and compare the results with those of experienced refractive surgeons.

SETTING

Doheny Eye Institute, University of Southern California, Los Angeles, and Department of Ophthalmology, University of California, Irvine, California, USA.

METHODS

In this retrospective case series, data were examined from the first PRK procedures by 33 consecutive ophthalmologists and the first LASIK procedures by 19 consecutive ophthalmologists. Preoperative and postoperative uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), as well as intraoperative and early postoperative complications, were recorded.

RESULTS

In the PRK group, 33.3% of eyes achieved a UCVA of 20/20 and 87.8%, 20/40 or better; 54.5% were within +/-0.5 diopter (D) of emmetropia and 87.8%, within +/-1.0 D. Two eyes with a preoperative spherical equivalent of greater than -11.0 D lost 2 lines of BSCVA. If eyes with low myopia (</= -6.5 D) only were included, 40.7% achieved a UCVA of 20/20 and 96.3%, 20/40 or better. In the LASIK group, 52.6% achieved a UCVA of 20/20 and 84. 2%, 20/40 or better; 78.9% were within +/-0.5 D of emmetropia and 89. 5%, +/-1.0 D. No eye in the LASIK group lost 2 or more lines of BSCVA.

CONCLUSIONS

Photorefractive keratectomy and LASIK are reasonably safe procedures that can be learned quickly by ophthalmic surgeons. Our data suggest that results achieved by beginning surgeons are comparable to those reported by experienced surgeons.