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

Long-term visual quality after small incision lenticule extraction (SMILE) and laser assisted subepithelial keratomileusis (LASEK) for low myopia

Background

Few studies have reported the visual outcomes of small-incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for myopia correction. This study aims to compare the visual quality and corneal wavefront aberrations after SMILE and LASEK for low-myopia correction.

Methods

In this prospective study, we included 29 eyes of 29 patients who received SMILE and 23 eyes of 23 patients who received LASEK between June 2018 and January 2019. The following measurements were assessed: uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, corneal wavefront aberrations, and subjective visual quality. All patients were followed up for two years.

Results

All procedures were uneventful. An efficacy index of 1.19 ± 0.17 was established in the SMILE group and 1.23 ± 0.20 in the LASEK group. No eyes lost more than two lines of CDVA. We found that 93% (27/29) of the treated eyes in the SMILE group and 91% (21/23) in the LASEK group had spherical equivalent (SE) within ± 0.25D. The increases in the total corneal spherical aberration and the corneal front spherical aberration were lower in the SMILE group than in the LASEK group (P < 0.01). In contrast, the increases in the total corneal vertical coma and the corneal front vertical coma in the SMILE group were greater than those in the LASEK group (P < 0.01).

Conclusion

Both SMILE and LASEK have good safety, stability, and patient-reported satisfaction for low myopia. SMILE induced less corneal spherical aberration but greater vertical coma than LASEK.

The use of topical nalbuphine in different concentrations to control pain after photorefractive keratectomy

PURPOSE

This is a randomized controlled study aiming to evaluate the safety and efficacy of two different concentrations of topical nalbuphine hydrochloride, when used to relieve pain in the first days following photorefractive keratectomy (PRK).

METHODS

This is a prospective double blinded randomized clinical trial that included 189 patients who had PRK for correction of low and moderate refractive errors. Patients were randomly assigned to three groups according to the eye drops given to relieve pain in the first three postoperative days; the first group received topical nalbuphine with a concentration of 2 mg/ml (Group A = 64 patients), the second group received topical nalbuphine in a concentration of 1 mg/ml (Group B = 69 patients) and the third group received topical artificial tears only (Group C = 56 patients).The patients were asked to rate their pain daily using a numeric rating scale and to record the number of drops instillation times/day. The time needed for complete epithelial healing, best-corrected visual acuity (BCVA) and spherical equivalent after three months were recorded in each group.

RESULTS

In the first three days, there was a statistically significant difference in pain score among the three groups with lower values in the two topical nalbuphine groups when compared with the control group receiving artificial tears. Moreover, the higher concentration group showed significantly lower pain score and less number of drops used /day in comparison with the lower concentration group.There were no statistically significant differences in epithelial healing time, BCVA and spherical equivalent after three months among the three groups.

CONCLUSION

The use of topical nalbuphine is effective in relieving pain in the first few days following PRK and this pain relief is not associated with any compromise regarding epithelial healing nor refractive outcome. The pain control with 2 mg/ml concentration is significantly higher than that with 1 mg/ml concentration of nalbuphine. Trial registration numberISRCTN21394752 https://doi.org/10.1186/ISRCTN21394752 The trial is retrospectively registered in ISRCTN registry at March 08, 2021.

Presbyopia and the aging eye: Existing refractive approaches and their potential impact on dry eye signs and symptoms

Every part of the human body is subject to aging, including the eye. An increased prevalence of dry eye disease with age is widely acknowledged. Aging threatens ocular surface homeostasis, altering the normal functioning of the lacrimal functional unit and potentially leading to signs and symptoms of dry eye. Additional age-related processes take place within the crystalline lens, leading to presbyopia and cataractogenesis. Correction strategies for presbyopia and cataracts may directly or indirectly challenge the ocular surface. Contact lenses disturb the normal structure of the tear film and can interact negatively with the ocular surface, further deteriorating an already unbalanced tear film in presbyopes, however, newer contact lens designs can overcome some of these issues. Moreover, cataract and corneal refractive surgeries sever corneal nerves and disrupt the corneal epithelium and ocular surface, which can influence surgical outcomes and aggravate dryness symptoms in older age groups. This review summarises the current understanding of how the invasive nature of contact lens wear and cataract and refractive surgery influence signs and symptoms of ocular dryness in an aging population.

Comparison of ReLEx SMILE and PRK in terms of visual and refractive outcomes for the correction of low myopia

PURPOSE

To compare the objective and subjective quality of vision after femtosecond laser-assisted small incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK) for low myopia.

METHODS

One hundred and twenty eyes from 60 patients (34 females, 26 males) undergoing bilateral correction of low myopia (≤-4 D SE) with either ReLEx SMILE or PRK were included. Visual acuity, contrast sensitivity and higher-order aberrations were recorded preoperatively and compared postoperatively. A quality of vision questionnaire was scored and analyzed 3 months postoperatively.

RESULTS

At 3 months, the SMILE group had significantly better uncorrected and corrected distant visual acuity (CDVA), compared to PRK group (p = 0.01). Post-op spherical equivalent (SE) was comparable in both groups (SMILE = -0.15 ± 0.19 D, PRK = -0.14 ± 0.23 D, p = 0.72). However, SE predictability was better in SMILE group with 97% eyes within ±0.05 D compared to 93% eyes in the PRK group. Total higher-order aberrations (HOAs) were significantly higher in PRK compared to the SMILE group (p = 0.022). The SMILE group demonstrated slightly better contrast sensitivity, which was significant at spatial frequency of 12 cpd (p = 0.03). Four eyes in the PRK group had loss of CDVA by one line due to mild haze.

CONCLUSIONS

Both SMILE and PRK were effective procedures for correction of low myopia. However, SMILE offered superior quality of vision and patient satisfaction due to better postoperative comfort and lower induction of aberrations at 3 months.

Laser-assisted subepithelial keratectomy (LASEK) versus photorefractive keratectomy (PRK) for correction of myopia

BACKGROUND

Myopia (near-sightedness or short-sightedness) is a condition in which the refractive power of the eye is greater than required. The most frequent complaint of people with myopia is blurred distance vision, which can be eliminated by conventional optical aids such as spectacles or contact lenses, or by refractive surgery procedures such as photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK). PRK uses laser to remove the corneal stroma. Similar to PRK, LASEK first creates an epithelial flap and then replaces it after ablating the corneal stroma. The relative benefits and harms of LASEK and PRK, as shown in different trials, warrant a systematic review.

OBJECTIVES

The objective of this review is to compare LASEK versus PRK for correction of myopia by evaluating their efficacy and safety in terms of postoperative uncorrected visual acuity, residual refractive error, and associated complications.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision group Trials Register) (2015 Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2015), EMBASE (January 1980 to December 2015), Latin American and Caribbean Health Sciences (LILACS) (January 1982 to December 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (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 December 2015. We used the Science Citation Index and searched the reference lists of the included trials to identify relevant trials for this review.

SELECTION CRITERIA

We included in this review randomized controlled trials (RCTs) comparing LASEK versus PRK for correction of myopia. Trial participants were 18 years of age or older and had no co-existing ocular or systemic diseases that might affect refractive status or wound healing.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all reports and assessed the risk of bias of trials included in this review. We extracted data and summarized findings using risk ratios and mean differences. We used a random-effects model when we identified at least three trials, and we used a fixed-effect model when we found fewer than three trials.

MAIN RESULTS

We included 11 RCTs with a total of 428 participants 18 years of age or older with low to moderate myopia. These trials were conducted in the Czech Republic, Brazil, Italy, Iran, China, Korea, Mexico, Turkey, USA, and UK. Investigators of 10 out of 11 trials randomly assigned one eye of each participant to be treated with LASEK and the other with PRK, but did not perform paired-eye (matched) analysis. Because of differences in outcome measures and follow-up times among the included trials, few trials contributed data for many of the outcomes we analyzed for this review. Overall, we judged RCTs to be at unclear risk of bias due to poor reporting; however, because of imprecision, inconsistency, and potential reporting bias, we graded the quality of the evidence from very low to moderate for outcomes assessed in this review.The proportion of eyes with uncorrected visual acuity of 20/20 or better at 12-month follow-up was comparable in LASEK and PRK groups (risk ratio (RR) 0.98, 95% confidence interval (95% CI) 0.92 to 1.05). Although the 95% CI suggests little to no difference in effect between groups, we judged the quality of the evidence to be low because only one trial reported this outcome (102 eyes). At 12 months post treatment, data from two trials suggest no difference or a possibly small effect in favor of PRK over LASEK for the proportion of eyes achieving ± 0.50 D of target refraction (RR 0.93, 95% CI 00.84 to 1.03; 152 eyes; low-quality evidence). At 12 months post treatment, one trial reported that one of 51 eyes in the LASEK group lost one line or more best-spectacle corrected visual acuity compared with none of 51 eyes in the PRK group (RR 3.00, 95% CI 0.13 to 71.96; very low-quality evidence).Three trials reported adverse outcomes at 12 months of follow-up or longer. At 12 months post treatment, three trials reported corneal haze score; however, data were insufficient and were inconsistent among the trials, precluding meta-analysis. One trial reported little or no difference in corneal haze scores between groups; another trial reported that corneal haze scores were lower in the LASEK group than in the PRK group; and one trial did not report analyzable data to estimate a treatment effect. At 24 months post treatment, one trial reported a lower, but clinically unimportant, difference in corneal haze score for LASEK compared with PRK (MD -0.22, 95% CI -0.30 to -0.14; 184 eyes; low-quality evidence).

AUTHORS' CONCLUSIONS

Uncertainty surrounds differences in efficacy, accuracy, safety, and adverse effects between LASEK and PRK for eyes with low to moderate myopia. Future trials comparing LASEK versus PRK should follow reporting standards and follow correct analysis. Trial investigators should expand enrollment criteria to include participants with high myopia and should evaluate visual acuity, refraction, epithelial healing time, pain scores, and adverse events.

Long term results of no-alcohol laser epithelial keratomileusis and photorefractive keratectomy for myopia

AIM

To evaluate the long term clinical results of mechanical no-alcohol-assisted laser epithelial keratomileusis (LASEK) versus standard photorefractive keratectomy (PRK) for low-moderate myopia.

METHODS

Twenty-five eyes treated with LASEK and twenty-five eyes treated with PRK were evaluated with a mean follow-up duration of 60mo. Mechanical separation of the epithelium was performed with blunt spatula and without application of alcohol. Laser ablation was performed with the MEL-70 excimer laser. All patients were examined daily until epithelial closure; at 1, 3, 6, and 12mo, and every year subsequently. Main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, haze, efficacy and safety indexes.

RESULTS

Twenty-one eyes and 22 eyes completed follow-up of 60mo in LASEK and PRK group respectively. Manifest refraction at 60mo follow-up was -0.01 and 0.26 in LASEK and PRK group respectively. In the LASEK group mean UDVA and mean CDVA after 60mo were 20/22 and 20/20 respectively (P>0.01). In the PRK group mean UDVA and mean CDVA at 60mo follow-up were 20/20 and 20/20 after 60mo (P>0.01). The efficacy indexes were 0.87 and 0.95, and the safety indexes were 1.25 and 1.4 respectively for LASEK group and PRK group.

CONCLUSION

Both standard PRK and no-alcohol LASEK offer safe and effective correction of low-moderate myopia in the long term without any statistically significant difference between the two groups.

Four-year to seven-year outcomes of advanced surface ablation with excimer laser for high myopia

PURPOSE

We aimed to evaluate and compare outcomes after photorefractive keratectomy with cooling (cPRK) and laser-assisted subepithelial keratectomy (LASEK) for high myopia.

METHODS

This was a retrospective, single-masked follow-up study of patients treated for myopia between 2007 and 2009 with cPRK or LASEK, using a high-frequency flying-spot excimer laser with eye-tracker (MEL80; Carl Zeiss, Jena, Germany). One eye of each patient was randomly chosen for analysis. Re-treated eyes were excluded.

RESULTS

Forty-six cPRK patients and 35 LASEK patients were included. Spherical equivalent averaged -7.69 ± 1.47 diopters (D) in cPRK eyes and -7.98 ± 2.06 D in LASEK eyes (p = 0.31) before surgery. The average follow-up time was 4.6 years in cPRK patients and 6.0 years in LASEK patients (p < 0.05). At final follow-up, no cPRK eyes and one LASEK eye (p = 0.46) had lost two lines of corrected distance visual acuity (CDVA). No eyes had significant haze at final follow-up, although trace haze was found in four cPRK eyes and six LASEK eyes (p = 0.44). However, at 6 weeks after surgery, zero cPRK eyes and nine LASEK eyes (p < 0.05) had significant haze. At final follow-up, 63 % of cPRK eyes and 35 % of LASEK eyes (p = 0.17) were within ±1.0 D of intended refraction. Finally, 100 % of cPRK patients and 92 % of LASEK patients (p = 0.87) were satisfied or very satisfied with the surgery at final follow-up.

CONCLUSION

cPRK and LASEK seemed safe and with high patient satisfaction 4 to 7 years after surgery for high myopia. However, cPRK was more effective than LASEK in reducing initial significant corneal haze.

Effects of differenta mitomycin C concentrations on laser-assisted subepithelial keratectomy

The aim of the present study was to determine the effect of different concentrations of mitomycin C (MMC) administered intraoperatively during laser-assisted subepithelial keratectomy (LASEK) surgery. A total of 261 patients (496 eyes) were randomly divided into two groups: 0.04% MMC treatment group consisting of 133 patients (245 eyes) and the 0.02% MMC treatment group consisting of 128 patients (251 eyes). The MMC solutions were dropped intraoperatively onto the ablation region and the duration was dependent on the preoperative refractive power of the patient’s cornea: ≤−3.00 diopters (D), 30 sec; between −3.25 D and −6.00 D, 60 sec; between −6.25 D and −9.00 D, 90 sec and ≥−9.25 D, 110 sec. Postoperative observations included haze formation, visual acuity, changes in refractive power, corneal endothelial cell density and incidence of complications. The one year postoperative incidence of haze differed significantly between the groups (P<0.05). The one week and one year comparisons of postoperative visual acuity also differed significantly between the groups (P<0.05). Postoperative changes in corneal refractive power at one, six and 12 months following surgery significantly differed between the groups (P<0.05). No statistically significant difference was identified between the density of corneal endothelial cells prior to surgery and the density at one, six and 12 months following surgery (P>0.05). Thus, the intraoperative application of 0.04% MMC solution effectively inhibited haze formation and markedly improved the efficacy of LASEK surgery, when compared with that of 0.02% MMC.

One-step transepithelial topography-guided ablation in the treatment of myopic astigmatism

PURPOSE

To evaluate one-step topography-guided transepithelial ablation in the treatment of low to moderate myopic astigmatism using a 1KHz excimer laser.

METHODS

Retrospective study of 117 consecutive eyes available for evaluation 12 months after surgery. Pre- and post-operative visual and refractive data as well as post-operative pain and haze were analyzed. A novel technique integrating custom refractive- and epithelial- ablation in a single uninterrupted procedure was used.

RESULTS

The mean pre-operative spherical equivalent (SE) and the mean cylinder were: -3.22 diopters (D) ±1.54 (SD) (range -0.63 to -7.25 D) and -0.77 D ±0.65 (range 0 to -4.50 D), respectively. At 12 months after surgery: no eyes lost ≥2 lines of corrected distant visual acuity (CDVA). Safety and efficacy indexes were 1.27 and 1.09, respectively. Uncorrected distant visual acuity (UDVA) was ≥20/20 in 96.6% of the eyes. Manifest refraction spherical equivalent was within ±0.5 D of the desired refraction in 93.2% of the eyes. Average root mean square (RMS) wavefront error measured at central 6 mm, increased from 0.38 pre-operatively to 0.47 µm post-operatively. Refractive stability was achieved and sustained 1 month after surgery. No visually significant haze was registered during the observation period. Post-operative pain was reported in 4.5% of patients.

CONCLUSIONS

One-step transepithelial topography-guided treatment for low to moderate myopia and astigmatism performed with a 1 KHz laser, provided safe, effective, predictable and stable results with low pain and no visually significant haze.

Efficacy, predictability, and safety of laser-assisted subepithelial keratectomy for the treatment of myopia and myopic astigmatism

Purpose:

The purpose was to report the refractive and visual outcomes of laser-assisted subepithelial keratectomy (LASEK) for the treatment of myopia.

Materials and Methods:

A retrospective, noncomparative consecutive case series of 173 of 91 patients who had undergone LASEK is presented. Primary outcome variables included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, epithelialization time, pain, haze, and complications.

Results:

Preoperatively, the mean spherical equivalent (SE) was –3.71 ± 1.63 D (range, –0.875 D to 8.25 D), and the mean LogMAR BSCVA was –0.0374 ± 0.0767 D (range, –0.47 D to 0.00 D). On the final visit, the mean SE was –0.05 ± 0.335 D (range, –1.63 D to 1.00 D), the mean LogMAR UCVA was 0.04674 ± 0.0771 D (range, –0.3010 D to 0.1249 D) and the mean LogMAR BSCVA was –0.0164 ± 0.0497 (range –0.3010 to 0.124). All eyes achieved vision of 20/40 or better, and 83.2% of the eyes achieved a vision of 20/25 or better. One 64 (94.94%) and all the eyes were within ± 0.50 D and ± 1.00 D of the attempted correction respectively. Complete epithelialization occurred in 4.70 ± 2.09 days (range, 2-10 days). At the final visit, 79.7% of eyes had a clear cornea. Grade 1 haze developed in 17.34% of the eyes, grade 2 haze developed in 2.89% of eyes developed; no eyes developed grade 3 or 4 haze.

Conclusions:

LASEK is a safe, effective, and predictable method for the treatment of myopia and myopic astigmatism.

Transport of topical anesthetics in vitamin E loaded silicone hydrogel contact lenses

Transport of surface active anesthetic drugs through silicone hydrogel contact lenses containing nanosized vitamin E aggregates is explored for achieving extended anesthetics delivery. Commercial silicone hydrogel contact lenses release most ophthalmic drugs including local anesthetics for only a few hours, which is not adequate. Here we focus on creating dispersion of highly hydrophobic vitamin E aggregates in the lenses as barriers for drug diffusion for increasing the release durations. This approach has been shown previously to be successful in extending the release durations for some common hydrophilic ophthalmic drugs. The topical anesthetic drugs considered here (lidocaine, bupivacaine, and tetracaine) are hydrophilic at physiologic pH due to the charge, and so these cannot partition into the vitamin E barriers. However, these surface active drug molecules adsorb on the surface of the vitamin E barriers and diffuse along the surface, leading to only a small decrease in the effective diffusivity compared to non-surface-active hydrophilic drugs. The drug adsorption can be described by the Langmuir isotherm, and measurements of surface coverage of the drugs on the vitamin E provide an estimate of the available surface area of vitamin E, which can then be utilized to estimate the size of the aggregates. A diffusion controlled transport model that includes surface diffusion along the vitamin E aggregates and diffusion in the gel fit the transport data well. In conclusion, the vitamin E loaded silicone contact lens can provide continuous anesthetics release for about 1-7 days, depending on the method of drug loading in the lenses, and thus could be very useful for postoperative pain control after corneal surgery such as the photorefractive keratectomy (PRK) procedure for vision correction.

Laser-assisted subepithelial keratectomy and photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism in adults

PURPOSE

To evaluate whether laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) achieve effective targeted correction and the extent of post-treatment corneal haze after corneal transplantation.

SETTING

Nonhospital surgical facility, Calgary, Alberta, Canada.

DESIGN

Evidence-based manuscript.

METHODS

This study evaluated visual acuity, refractive error correction, and potential complications after LASEK or PRK to eliminate refractive error differences after penetrating keratoplasty in adults. A Nidek EC-5000 or Technolas 217 excimer laser was used in all treatments.

RESULTS

At last follow-up (mean 20.50 months post laser), the mean spherical equivalent (SE) decreased from -2.71 diopters (D) ± 4.17 (SD) to -0.54 ± 3.28 D in the LASEK group and from -4.87 ± 3.90 D to -1.82 ± 3.34 D in the PRK group. The mean preoperative uncorrected distance visual acuity (UDVA) was 1.63 ± 0.53 and 1.45 ± 0.64, respectively, and the mean postoperative UDVA, 0.83 ± 0.54 and 0.90 ± 0.55, respectively. The improvement in SE and UDVA was statistically significant in both groups (P < .01). The mean haze (0 to 3 scale) at the last follow-up was 0.46 ± 0.708 in the LASEK group and 0.58 ± 0.776 in the PRK group.

CONCLUSIONS

The UDVA improved and refractive errors were effectively reduced after LASEK or PRK in eyes with previous PKP. There was no significant difference in the change in SE, UDVA, or corrected distance visual acuity between LASEK and PRK. Some patients had evidence of corneal haze, although the difference between the groups was not significant.

Meta-analysis: clinical outcomes of laser-assisted subepithelial keratectomy and photorefractive keratectomy in myopia

PURPOSE

To examine possible differences in clinical outcomes between laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for myopia.

DESIGN

Systematic review and meta-analysis.

PARTICIPANTS

Patients from previously reported randomized controlled trials (RCTs) and comparative studies of LASEK and PRK with clinical outcomes.

METHODS

A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify RCTs and comparative studies comparing LASEK and PRK for myopia.

MAIN OUTCOME MEASURES

Primary outcome parameters included uncorrected visual acuity (UCVA) of 20/20 or better, manifest refractive spherical equivalent (SE) within ± 0.50 diopters (D), final refractive SE, and final UCVA of 20/40 or worse. Secondary outcome parameters included healing time of corneal epithelium, postoperative pain, and corneal haze.

RESULTS

Twelve studies were identified and used for comparing PRK (499 eyes) with LASEK (512 eyes) for myopia. There were no significant differences in odds ratio (OR), weighted mean difference (WMD), and standardized mean difference (SMD) in the primary and secondary outcome measures. The final mean refractive SE (WMD, 0.00; 95% confidence interval [CI], -0.08 to 0.07; P = 0.95), manifest refractive SE within ± 0.50 D of the target (OR, 0.90; 95% CI, 0.63-1.29; P = 0.56), patients achieving UCVA of 20/20 or better (OR, 0.86; 95% CI, 0.61-1.20; P = 0.37), final UCVA of 20/40 or worse (OR, 1.26; 95% CI, 0.63-2.51; P = 0.52), re-epithelialization time (WMD, 0.08; 95% CI, -0.44 to 0.59; P = 0.77), and postoperative pain (SMD, 0.26; 95% CI, -0.20 to 0.72; P = 0.27) were analyzed. However, LASEK-treated eyes showed less corneal haze at 1 month after surgery (WMD, 0.25; 95% CI, 0.10-0.39; P = 0.0007) and 3 months after surgery (WMD, 0.14; 95% CI, 0.01-0.26; P = 0.03) compared with PRK. No statistically significant difference was observed between the 2 groups at 6 months after surgery (WMD, 0.14; 95% CI, -0.02 to 0.30; P = 0.08).

CONCLUSIONS

In this meta-analysis, LASEK-treated eyes had no significant benefits over PRK-treated ones with regard to clinical outcomes. Less corneal haze was observed in LASEK-treated eyes at 1 to 3 months after surgery.

Histological evaluation of mechanical epithelial separation in epithelial laser in situ keratomileusis

PURPOSE

To evaluate the effect of mechanical epithelial separation with an epikeratome on the histologic ultrastructure of epithelial flaps and stromal beds from human corneas.

SETTING

Departments of Ophthalmology, Osaka University Medical School, Osaka, and Tohoku University School of Medicine, Sendai, and Institute of Advanced Biomedical Engineering and Science and Medical Research Institute, Tokyo Women's Medical University, Tokyo, Japan.

METHODS

Eye-bank eyes were deepithelialized using an Epi-K epikeratome. Epithelial flaps and stromal beds were assessed by light and electron microscopy. Immunofluorescence staining for types IV and VII collagens, integrins alpha(6) and beta(4), and laminin 5 was also performed.

RESULTS

Four eyes were evaluated. On scanning electron microscopy, the cleavage planes of epithelial flaps and stromal beds were relatively smooth. On transmission electron microscopy, epithelial flaps were separated partially within the lamina fibroreticularis and partially within the lamina lucida. Immunofluorescence showed positive staining for type VII collagen and discontinuous staining for type IV collagen in stromal beds. Discontinuous linear staining for types IV and VII collagens was observed in epithelial flaps. Staining for integrins alpha(6) and beta(4) was positive in some regions and discontinuous in other regions of epithelial flaps. In stromal beds, integrins alpha(6) and beta(4) had a patchy expression pattern. Staining for laminin 5 was intermittently positive along the basal side of epithelial flaps and stromal beds.

CONCLUSIONS

Epithelial flaps created with an epikeratome were mechanically separated partly within the lamina fibroreticularis and partly within the lamina lucida. Stromal beds had relatively smooth surfaces with no obvious trauma to Bowman layer.

Comparison of early postoperative clinical outcomes of photorefractive keratectomy and lamellar epithelial debridement

PURPOSE

To compare early postoperative clinical outcomes of photorefractive keratectomy (PRK) and lamellar epithelial debridement (LED).

SETTING

Department of Ophthalmology, Kangbuk Samsung Hospital, Seoul, Korea.

METHODS

This prospective study was of patients randomly assigned to have PRK or LED. In the LED group, an epithelial flap was created using an Amadeus II epikeratome. Postoperative follow-up was at 1, 3, and 7 days and 1, 3, and 6 months. The outcome parameters were uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), higher-order aberrations (HOAs), epithelial healing time, and corneal haze.

RESULTS

The study comprised 39 patients (76 eyes). The mean preoperative spherical equivalent (SE) was -3.96 diopters (D) +/- 1.24 (SD) in the PRK group and -4.06 +/- 1.39 D in the LED group. Postoperative UCVA was significantly better in the LED group 1 day postoperatively. The UCVA was 20/20 or better in 14.6% in the PRK group and 42.9% in the LED group (P = .006); 20/25 or better in 41.5% and 82.9%, respectively (P = .000); and 20/40 or better in 80.5% and 100%, respectively (P = .006). On subsequent follow-up visits, the UCVA was comparable between groups. No eye lost lines of BCVA at 3 months. There was no difference between groups in postoperative SE refraction, HOAs, or corneal haze.

CONCLUSIONS

Lamellar epithelial debridement and PRK had comparable safety and efficacy in the surgical correction of low to moderate myopia. The UCVA was significantly better after LED than after PRK 1 day postoperatively and equivalent thereafter.

Comparison between three- and six-month postoperative refractive and visual results after laser epithelial keratomileusis with mitomycin C

PURPOSE

To compare the residual refraction and visual results between the three- and six-month postoperative visits to detect the optimal moment for enhancement after myopic laser epithelial keratomileusis (LASEK) with mitomycin C (MMC).

DESIGN

Nonrandomized, interventional, prospective study.

METHODS

One hundred and forty-one consecutive eyes that underwent LASEK with MMC to correct their myopia using the Esiris excimer laser (Schwind Eye Tech Solutions, Kleinostheim, Germany), and that showed three months postoperatively a residual defect or a suboptimal uncorrected visual acuity (UCVA) or best spectacle-corrected visual acuity (BSCVA) were included in the study. We compared the residual spherical refraction and cylinder, the UCVA, and the BSCVA between the three- and six-month postoperative examinations.

RESULTS

Preoperative spherical refraction was -5.2 +/- 2.90 diopters (D). Preoperative cylinder was -1.66 +/- 1.20 D. The residual sphere was +0.43 +/- 0.90 D three months and +0.21 +/- 0.90 D six months after surgery (P = .0001). The cylinder was -0.71 +/- 0.60 D and -0.67 +/- 0.60 D, respectively (P = .4). The UCVA was 0.75 +/- 0.2 and 0.81 +/- 0.2 (P = .0001) and the BSCVA was 0.94 +/- 0.1 and 1.01 +/- 0.1 (P = .0001), respectively. Those patients with a myopic defect (sphere or cylinder) three months postoperatively did not show any significant change in UCVA or refractive defect six months after surgery, while those with a hyperopic defect (sphere or cylinder) showed an improvement in UCVA and residual refraction six months postoperatively (P < .05).

CONCLUSIONS

Our results suggest that retreatment after myopic LASEK with MMC may be performed three months after surgery when the residual refraction is myopic, but it seems wise to wait at least six months after surgery when the residual refraction is hyperopic.

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.

Comparison of visual results between laser-assisted subepithelial keratectomy and epipolis laser in situ keratomileusis to correct myopia and myopic astigmatism

PURPOSE

To compare the visual results after laser-assisted subepithelial keratectomy (LASEK) and epipolis laser in situ keratomileusis (epi-LASIK) to correct myopia.

DESIGN

Retrospective, interventional, nonrandomized comparative study.

METHODS

Patients treated with LASEK to correct myopia < or = -9.00 diopters (D) were compared to age- and refraction-matched patients treated with epi-LASIK using the same excimer laser (Esiris; Schwind Eye Tech Solutions, Kleinostheim, Germany). The epithelial flap was replaced after the ablation in every case. The visual results after both procedures were compared at each postoperative visit (one day, one week, one and three months).

RESULTS

Ninety-four consecutive eyes were included in the study (47 in each group), matched for age and refraction. The preoperative spherical manifest refraction was -3.98 +/- 2.40 D in the LASEK group and -3.95 +/- 2.40 D in the epi-LASIK group (P = .9) (range -0.50 to -9.00 D). The uncorrected visual acuity (UCVA) one day postoperatively was 0.7 +/- 0.2 and 0.5 +/- 0.2 (P < .001), and one week after surgery it was 0.8 +/- 0.2 and 0.7 +/- 0.2, respectively (P = .1). The difference was again statistically significant one month after surgery (0.94 +/- 0.1 after LASEK, 0.82 +/- 0.1 after epi-LASIK, P < .001), but not three months postoperatively (1.06 +/- 0.21 and 1.03 +/- 0.18, respectively, P = .1). UCVA was > or =1.0 in 78.7% of LASEK eyes and 65.9% of epi-LASIK eyes three months after surgery. At that moment, the safety indices were 0.99 +/- 0.1 after LASEK and 0.93 +/- 0.1 after epi-LASIK (P = .04). The efficacy indices were 0.97 +/- 0.1 and 0.89 +/- 0.1, respectively (P = .01).

CONCLUSIONS

Our results suggest a faster visual rehabilitation and better safety and efficacy outcomes after LASEK compared to epi-LASIK with repositioning of the epithelial flap when correcting low to moderate myopia.

Oral gabapentin for the treatment of postoperative pain after photorefractive keratectomy

PURPOSE

To evaluate oral gabapentin for postoperative pain after photorefractive keratectomy (PRK).

DESIGN

Prospective, nonrandomized clinical trial.

METHODS

In additional to a standard regimen of topical antibiotics, topical steroids, and topical tetracaine as required, all PRK patients at our laser vision center were treated after surgery for pain for a two-month period with Percocet (oxycodone/acetaminophen) [Endo Pharmaceuticals; Chadds Ford, Pennsylvania, USA] 5 mg/325 mg as required for three days (control group). Patients completed a pain assessment survey using a faces pain scale (from zero through 6) on the evening of surgery and each subsequent morning and evening until postoperative day 3. A successive cohort of patients received Neurontin (gabapentin) [Pfizer, New York, New York, USA] 300 mg thrice daily (first dose administered two hours or more before the procedure) as an oral pain medication for three days, and the same survey data were collected.

RESULTS

Data were collected on 141 patients in each cohort. Successful pain management score (defined as faces zero through 2 on the scale) differences did not reach statistical significance between the two cohorts except on the morning of the second postoperative day, when gabapentin was superior. On all postoperative days, patients in the oxycodone/acetaminophen cohort used significantly less tetracaine eye drops as required. The percent of patients rating overall pain experience as better than expected was 35% and 36%, those rating pain experience as about what was expected was 50% and 49%, and those rating pain experience as worse than expected was 15% and 15% in the oxycodone/acetaminophen and gabapentin cohorts, respectively.

CONCLUSIONS

We found no difference in overall subjective pain management ratings between gabapentin and oxycodone/acetaminophen for postoperative PRK pain, although gabapentin was associated with significantly more frequent use of anesthetic eye drops as required.

The changes of posterior corneal surface and high-order aberrations after refractive surgery in moderate myopia

Purpose

To compare forward shift of posterior corneal surface and higher-order aberration (HOA) changes after LASIK, LASEK, and wavefront-guided LASEK surgery in moderate myopia

Methods

One hundred eighty four eyes undergoing LASIK, LASEK and wavefront-guided LASEK with VISX STAR S4 were included in this study. The posterior corneal elevation was measured with Orbscan before, 2 and 4 months after surgery. Changes of the elevation were assessed using the difference map generated from preoperative and postoperative elevation maps. The values of higher-order aberrations were evaluated preoperatively and 2 months postoperatively with Wavefront aberrometer.

Results

The posterior corneal surface displayed forward shift of 27.2±11.45 µm, 24.3±9.76 µm in LASIK group, 23.4±10.5 µm, 23.6±10.55 µm in LASEK group, 24.0±14.95 µm, 28.4±14.72 µm in wavefront-guided LASEK group at 2 months and 4 months, respectively. There were no statistically significant differences among those three groups, and between 2 and 4 months. The root mean score (RMS) of HOA was increased after LASIK and LASEK (p=0.000, p=0.000, respectively). The mean change of HOA-RMS was significantly smaller in wavefront-guided LASEK than LASIK or LASEK (p=0.000, p=0.000, respectively, Bonferroni-corrected).

Conclusions

The changes of posterior corneal surface forward shift showed no difference among LASIK, LASEK and wavefront-guided LASEK in moderate myopia. HOAs were significantly increased after LASIK and LASEK. The changes of HOAs were significant smaller in wavefront-guided LASEK than LASIK or LASEK.

Changes in higher order aberrations after wavefront-guided PRK for correction of low to moderate myopia and myopic astigmatism: two-year follow-up

PURPOSE

To assess efficacy, safety, and changes in higher order aberrations after wavefront-guided photorefractive keratectomy (PRK) in comparison with conventional PRK for low to moderate myopia with myopic astigmatism using a WASCA Workstation with the MEL 70 G-Scan excimer laser.

METHODS

A total of 126 myopic or myopic-astigmatic eyes of 112 patients were included in this retrospective study. Patients were divided into two groups: Group 1, the study group; and Group 2, the control group. Group 1 consisted of 78 eyes treated with wavefront-guided PRK. Group 2 consisted of 48 eyes treated with spherocylindrical conventional PRK.

RESULTS

Two years postoperatively, in Group 1, 5% of eyes achieved an uncorrected visual acuity (UCVA) of 0.05; 69% achieved a UCVA of 0.00; 18% of eyes experienced enhanced visual acuity of -0.18 and 8% of -0.30. In Group 2, 8% of eyes achieved a UCVA of 0.1; 25% achieved a UCVA of 0.05; and 67% achieved a UCVA of 0.00 according to logMAR calculation method. Total higher-order root-mean square increased by a factor 1.18 for Group 1 and 1.6 for Group 2. There was a significant increase of coma by a factor 1.74 in Group 2 and spherical aberration by a factor 2.09 in Group 1 and 3.56 in Group 2.

CONCLUSIONS

The data support the safety and effectiveness of the wavefront-guided PRK using a WASCA Workstation for correction of low to moderate refractive errors. This method reduced the number of higher order aberrations induced by excimer laser surgery and improved uncorrected and spectacle-corrected visual acuity when compared to conventional PRK.

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.

Learning curve of laser-assisted subepithelial keratectomy

PURPOSE

To study the effect of the learning curve of laser-assisted subepithelial keratectomy (LASEK) on the visual and refractive results.

METHODS

This retrospective study comprised 56 eyes that had LASEK for myopia. The eyes were among the first 143 that had LASEK by the same surgeon with the same excimer laser and same nomogram. The 56 eyes were separated into 2 groups. Group 1 included the first 28 eyes to have LASEK by the surgeon. Group 2 comprised the last 28 eyes in the series whose refractive error could be matched with that in Group 1. The outcomes in the 2 groups were compared.

RESULTS

The mean preoperative spherical refraction was -3.90 diopters (D) +/- 1.90 (SD) in Group 1 and -3.70 +/- 2.53 D in Group 2 (P = .2). There were no significant differences in preoperative cylinder or best spectacle-corrected visual acuity (BSCVA) between groups. The postoperative uncorrected visual acuity (UCVA) was significantly worse in Group 1 on 1 day and 7 days postoperatively (P = .02 and P = .03, respectively); there was no significant difference at 1 month and 3 months. The safety index (postoperative BSCVA/preoperative BSCVA) and efficacy index (postoperative UCVA/preoperative BSCVA) were better in Group 2, although the difference was not statistically significant. The spherical refraction 3 months postoperatively was +0.50 +/- 0.83 D in Group 1 and +0.10 +/- 0.27 D in Group 2 (P = .02); 75.00% of eyes and 96.42% of eyes, respectively, were within +/-0.50 D of the intended correction (P = .01). Seven percent of eyes in Group 1 and no eye in Group 2 lost 2 or more lines of BSCVA.

CONCLUSIONS

Results indicate that the outcomes of LASEK depend on surgeon experience. Thus, caution is advised when interpreting LASEK results without knowing the surgeon's level of experience.

LASEK Versus LASIK for the Correction of Moderate Myopia

PURPOSE

To compare the results of laser subepithelial keratomileusis (LASEK) and laser in situ keratomileusis (LASIK) for the correction of moderate myopia.

METHODS

We performed a retrospective, single-masked, interventional study of 80 consecutive eyes. Forty eyes that had undergone LASEK to correct myopia of -2.0 to -6.0 D were compared with age and refraction matched patients treated with LASIK. All eyes had been operated by the same experienced surgeon using the same laser (Technolas 217). Mitomycin C was not used in any patient.

RESULTS

Eighty eyes were reviewed (40 treated with LASEK, 40 treated with LASIK). The preoperative mean sphere was -3.8 D (range -2 to -6D) and mean cylinder was -0.7 D (range 0 to -2 D) in both groups. Postoperative uncorrected visual acuity was worse in LASEK eyes 1 and 7 days postoperatively (p = 0.0001), although the difference 7 days postoperatively (<one letter) was not clinically meaningful. No significant differences were noted 3 months postoperatively either in the uncorrected visual acuity, in the best-spectacle corrected visual acuity, or in the residual refractive error. Nine LASEK-treated eyes showed a postoperative refraction of +1 D or more. These cases had a higher preoperative sphere (-4.5 D) compared with the nonovercorrected LASEK-treated eyes (-3.5 D) (p = 0.03). One eye after LASEK and four eyes after LASIK needed retreatment (p > 0.05).

CONCLUSIONS

LASEK and LASIK seem to be similar in terms of safety and efficacy for the correction of moderate myopia. Nevertheless, a trend toward overcorrection was found in the LASEK group in correlation with a higher preoperative refractive error.

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.

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.

Comparison Between LASEK and LASIK for the Correction of Low Myopia

PURPOSE

To compare the refractive results of laser epithelial keratomileusis (LASEK) and laser in situ keratomileusis (LASIK) for the correction of low myopia.

METHODS

A prospective, interventional, non-randomized, observer-masked study was performed of patients with myopia of < or = -2.50 diopters (D) (cylinder < or = 1.50 D) who had undergone either LASEK or LASIK. Refractive analysis was performed by a masked observer preoperatively and 1 day, 1 week, and 1 and 3 months postoperatively.

RESULTS

Seventy-nine eyes that fulfilled the inclusion criteria in each group were included in the study. No statistically significant differences were noted in age, gender, or preoperative refractive error between groups. Postoperative uncorrected visual acuity (UCVA) was significantly lower in LASEK eyes 1 and 7 days postoperatively (P = .0001). At 1 and 3 months postoperatively, no significant differences were noted between the groups in UCVA (P = .07), but best spectacle-corrected visual acuity 3 months postoperatively was significantly better in LASEK eyes (P = .01). The refractive error was similar in both groups (P = .3).

CONCLUSIONS

Visual improvement after LASEK for low myopia is significantly slower than after LASIK. Visual outcomes at 3 months postoperatively were similar with both techniques for the correction of low myopia.

Early Postoperative Pain Following Epi-LASIK and Photorefractive Keratectomy: A Prospective, Comparative, Bilateral Study

PURPOSE

To compare postoperative pain associated with epi-LASIK versus photorefractive keratectomy (PRK).

METHODS

This prospective observer-masked randomized study included 40 eyes of 20 patients with myopia and astigmatism who received epi-LASIK (Moria Epi-K) in one eye and PRK in the contralateral eye. Corneal ablation was done using the NIDEK EC-5000 excimer laser. Patients were seen at days 1, 3, and 6 to rate their pain via three measuring tools: 1) a global subjective rating, 2) a 10-cm visual analog scale, and 3) an 11-point numeric scale of pain.

RESULTS

On postoperative day 1, 19 of 20 patients reported pain in both eyes. Using the global subjective rating scale, patients reported more pain for those eyes treated by PRK. Although clinically relevant, this difference was not statistically significant (P = .56). Based on the 11-point numeric scale of pain and visual analog scale, mean pain scores were similar for both groups. On day 3, using the global subjective rating scale, 11 of 12 patients who had pain reported more in the epi-LASIK treated eye (P = .0005). In addition, epi-LASIK eyes demonstrated higher mean pain scores based on the other two scales (visual analog scale, P = .045 and 11-point numeric scale of pain, P = .023). Only 6 patients reported minimal pain on day 6. It was more frequently reported and slightly more marked in epi-LASIK eyes, but did not reach statistical significance.

CONCLUSIONS

Epi-LASIK and PRK have similar pain on postoperative day 1, but epi-LASIK demonstrated statistically more pain than PRK on days 3 and 6.

Comparison of Laser Epithelial Keratomileusis With and Without the Use of Mitomycin C

PURPOSE

To analyze the results of prophylactic intraoperative use of mitomycin C (MMC) in laser epithelial keratomileusis (LASEK).

METHODS

A retrospective analysis of 30 LASEK cases that received MMC 0.02% intraoperatively (MMC group) was performed and compared to the results obtained in 28 LASEK cases not receiving MMC (no MMC group). Mitomycin C was placed in contact with the ablation zone for 75 seconds with an imbibed microsponge. Both groups received postoperative fluorometholone for 3 months. Preoperative spherical equivalent refraction was -5.72 +/- 2.82 diopters (D) in the MMC group and -5.81 +/- 2.74 D in the no MMC group. Best spectacle-corrected visual acuity was 0.88 +/- 0.12 in the MMC group and 0.88 +/- 0.13 in the no MMC group.

RESULTS

Spherical equivalent refraction at 6 months postoperatively was +0.11 +/- 0.13 D in the MMC group and +0.09 +/- 0.37 D in the no MMC group. Best spectacle-corrected visual acuity was 0.90 +/- 0.13 in the MMC group and 0.88 +/- 0.13 in the no MMC group. Uncorrected visual acuity (UCVA) > or = 20/40 was obtained in 93.3% of cases in the MMC group and in 89.3% of cases in the no MMC group; UCVA > or = 20/25 was achieved in 76.6% of cases in the MMC group and in 71.4% of cases in the no MMC group. Haze incidence for the MMC group was: trace: 0%, Grades I: 0%, II: 0%, III 0%, IV: 0%, and for the no MMC group: trace: 17.9%, Grades I: 3.6%, II: 0%, III: 0%, IV: 0%. A statistically significant difference (P<.001) was noted in haze intensity between the MMC group and no MMC group.

CONCLUSIONS

Prophylactic use of intraoperative MMC in LASEK significantly decreases haze incidence.

Ethanol Treatment Induces Significant Cell Death in Porcine Corneal Fibroblasts

PURPOSE

To explore the effect of ethanol treatment on corneal stromal cells.

METHODS

Primary porcine corneal fibroblasts from passages 3 to 5 were treated with ethanol at concentrations of 10%, 15%, 20%, and 50% for 30 seconds. A control group was treated with phosphate-buffered saline (PBS) for 30 seconds. Morphologic changes were documented with phase-contrast microscopy, and the growth curves were examined with a PicoGreen assay. Cellular viability was examined with an ethidium homodimer and calcein-AM stain, whereas cellular apoptosis and/or necrosis were analyzed by a YO-PRO-1 dye/propidium iodide apoptosis assay coupled with flow cytometry and further confirmed with a genomic DNA pattern assay. Cellular toxicity was examined with a lactate dehydrogenase (LDH) assay.

RESULTS

Significant cell rounding and detachment from the culture dish were noticed after 20% ethanol treatment of 30 seconds, despite that the cell morphology remained unchanged in the PBS and 10% and 15% ethanol groups. Twenty percent ethanol induced significant cellular toxicity, causing cell death as shown by ethidium homodimer and calcein-AM stain, YO-PRO-1 dye/propidium iodide apoptosis assay, and LDH assay, although 10% and 15% ethanol caused minimal changes to corneal fibroblasts. Cellular death was most significant 6 hours after the 20% ethanol treatment. The genomic DNA pattern revealed intact DNA in the control, 10% ethanol, and 15% ethanol groups at all times, whereas DNA smearing was noticed at 48 hours after the 20% ethanol treatment. However, none of the DNA examined revealed significant DNA laddering patterns of apoptosis. Fifty percent ethanol treatment of 30 seconds resulted in cell fixation and cell death.

CONCLUSION

Treatment with 20% ethanol for 30 seconds induced significant porcine corneal fibroblast cell death, whereas 10% and 15% ethanol treatment of 30 seconds caused minimal changes. We propose that, when applied for 30 seconds, 20% ethanol is the threshold level that causes cell death in cultured porcine corneal fibroblasts.

One-year Outcomes of a Bilateral Randomized Prospective Clinical Trial Comparing Laser Subepithelial Keratomileusis and Photorefractive Keratectomy

PURPOSE

To compare laser subepithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK) in different eyes of the same patients in terms of visual acuity, refractive error, and complications over 1 year.

METHODS

This prospective, randomized, double-masked study comprised 30 active-duty military personnel with myopia who underwent LASEK in one eye and PRK in the other eye.

RESULTS

Twenty-eight patients' results were available for 1-year follow-up. The primary outcome measures were visual acuity and refractive error. The mean visual acuity for the LASEK group was 1.56 and 1.67 for the PRK group (z = -0.18, P = .15). The mean spherical equivalent refraction for the LASEK group was -0.007 D and +0.124 D for the PRK group (t = 0.982, P = .40). No significant differences were noted in visual acuity or refractive error in the eyes that had LASEK versus the eyes that had PRK.

CONCLUSIONS

After 1-year follow-up, LASEK and PRK show similar levels of visual acuity and refractive error.

One-year Outcomes of Epi-LASIK for Myopia

PURPOSE

To evaluate the early clinical outcomes of epi-LASIK for myopia.

METHODS

This study comprised 302 eyes of 162 patients. Epi-LASIK was performed with an automatically rotational epikeratome (KM-5000D). Epithelial separation was achieved mechanically without the use of alcohol. After laser ablation, the epithelial sheet was repositioned and a therapeutic contact lens was applied to the cornea immediately for 3 to 5 days. Postoperative visual acuity, symptoms, epithelial sheet, contrast sensitivity, wavefront aberration, and haze formation were evaluated 3, 6, and 12 months postoperatively.

RESULTS

Of the 302 eyes, 72 eyes (42 patients) with a mean spherical equivalent refraction of -9.13 +/- 4.23 diopters (D) (range: -1.25 to -19.0 D) had > 1-year follow-up. One eye failed to make the epithelial sheet because of the narrow palpebral fissure. An integrated epithelial sheet with a diameter of 8 to 9 mm was made in 289 (95.7%) eyes, leaving a superior hinge of approximately 2 to 4 mm. In 1 eye, stromal tissue remained in the epithelial sheet. Free epithelial flaps were made in 12 (4%) eyes. Mild discomfort was reported by 150 patients (282 eyes, 93.4%). Twelve patients (20 eyes, 6.6%) reported moderate symptoms. At 1 day postoperatively, corneal epithelium was almost transparent or had mild focal edema in 288 (95.4%) eyes; moderate edema was reported in 14 (4.6%) eyes. At 1 year postoperatively, spherical equivalent refraction of 60 (83.3%) eyes was within +/- 1.0 D of attempted refraction. Grade 0.5 haze was found in 2 eyes; all other eyes had no haze. No eye lost any lines of best spectacle-corrected visual acuity (BSCVA), whereas 12 (16.7%) of 72 eyes gained one or two lines of BSCVA. Contrast sensitivity decreased 1 month postoperatively and was restored to preoperative levels in eyes with preoperative spherical equivalent refraction < -10.0 D. Higher order aberration increased significantly postoperatively.

CONCLUSIONS

Epi-LASIK is a safe and efficient method to correct myopia with the advantage that it has only mild symptoms and mild haze. A larger study with longer follow-up is needed to determine its long-term clinical outcomes.

Topography-guided customized laser-assisted subepithelial keratectomy for the treatment of postkeratoplasty astigmatism

PURPOSE

To assess topography-assisted corneal wavefront excimer laser surface ablation for the correction of ametropia and irregular astigmatism after keratoplasty.

SETTING

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

METHODS

In this pilot study, 15 patients (16 eyes) who were intolerant of spectacle and contact lens correction due to astigmatic anisometropia after keratoplasty (15 penetrating and 1 lamellar) had topography-assisted customized excimer laser treatments. Corneal topographic data using a Keratron Scout, Placido disk system allowed for preoperative analysis of wavefront anomalies of the anterior corneal surface from which a customized excimer laser correction of both lower-order aberrations (LOAs) and higher-order aberrations (HOAs) was prepared (ORK software) for treatment with a Schwind Esiris flying-spot laser. All eyes had laser-assisted subepithelial keratectomy (LASEK) using 15% alcohol with a 20-second to 30-second application. Four eyes received an application of mitomycin-C (MMC) 0.2 mg/mL for 1 minute after stromal ablation.

RESULTS

The mean preoperative spherical equivalent (SE) was -3.50 diopters (D) +/- 3.97 (SD) (range +1.625 to -9.25 D). The preoperative cylindrical error was -7.2 D (range -2.75 to -13.5 D). The programmed laser correction was -3.14 D (range +1.62 to -9 D) with a maximum attempted cylindrical correction of -7 D. Adherent LASEK epithelial flaps along suture lines and the graft-host junction were noted in 9 eyes (56%), although it was possible to obtain and replace a partial flap. A follow-up of 18 months was achieved in all eyes. At the final follow-up visit, the mean postoperative SE was -1.08 +/- 1.85 D (range +3 to -4.78 D) (P<.01, F<.01). Ten eyes (62.5%) were within +/-1 D of the intended correction. The mean postoperative cylindrical error was -2.72 D (range -0.5 to -6.5 D) (P<.001), with vector analysis demonstrating a mean 6.23 D correction. Analysis of HOAs using a 6.0 mm pupil size demonstrated a significant reduction of higher-order root mean square (RMS) (P<.002), trefoil (P<.005), and 4th-order spherical aberration (P<.02) at 18 months compared with preoperative values. Uncorrected visual acuity improved in all eyes (P<.0001). Best spectacle-corrected visual acuity was unchanged or improved in 13 eyes (81%) and worse in 2 eyes by 1 line; 1 eye lost 3 lines due to an increase in preexisting cataract. In eyes that did not receive MMC, corneal haze (grade II to IV) was encountered in 3 eyes (27%). One eye required phototherapeutic keratectomy with MMC application at 12 months. Of the 4 eyes treated with MMC, 1 had trace haze and 3 had no detectable haze. There were no reported cases of epithelial instability, ectasia, or graft rejection.

CONCLUSIONS

Topography-assisted customized LASEK was effective in the correction of postkeratoplasty astigmatism. A significant improvement of both LOAs and HOAs was obtained with good refractive stability for over 18 months. Iatrogenic haze typically occurred but appeared to be minimized with adjunctive use of intraoperative MMC.