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LenSx®-Femto-LASIK, FEMTO LDV Z4®-Femto-LASIK und PRK: Vergleich refraktiver Ergebnisse und Komplikationsanalyse
Abstract
Background:
The aim of this study is to evaluate three refractive procedures: LenSx® (Alcon, Fort Worth, TX, USA) femto-laser in situ keratomileusis (LASIK), FEMTO LDV Z4® (Ziemer, Port, Switzerland) femto-LASIK, and photorefractive keratectomy (PRK) in terms of refractive outcome, perioperative complications, pain, and patient satisfaction.
Materials and methods:
Data of 168 eyes (myopic n = 84) were included in this retrospective study. Of these, 54 eyes (n = 27, 33.85 ± 7.64 years) were treated with LenSx® femto-LASIK, 60 eyes (n = 30, 35.03 ± 7.46 years) with FEMTO LDV Z4® femto-LASIK, and 54 eyes (n = 27, 33.24 ± 8.52 years) with PRK. Photoablation was induced by a MEL80 Excimerlaser (Zeiss, Oberkochen, Germany). The corrected (Vsc) and uncorrected (Vcc) distance subjective visual acuity, corneal topography (Pentacam® HR; Wetzlar, Germany), and objective astigmatism (ARK-760A Refractometer ; Nidek, Fremont, CA, USA) were measured preoperatively, and 1 day, 1 week, 1 month, and 3 months postoperatively. Subjective pain (verbal rating scale) and patient satisfaction were also recorded.
Results:
Subjective Vsc showed significantly better results in both femto-LASIK cohorts compared to PRK (p < 0.05) 1 day and 1 week postoperatively. There was no significant difference between the groups in terms of spherical equivalent and astigmatism 3 months postoperatively. The LenSx® femto-LASIK caused flap complications. The highest patient satisfaction results were shown in the LDV Z4® group, followed by the LenSx® and PRK cohorts (p = 0.072). LDV Z4® femto-LASIK showed the lowest pain score 1 day postoperatively (p < 0.001). There was no significant correlation between target refraction and preoperative corneal thickness and astigmatism.
Discussion:
Femtosecond laser-assisted LASIK is an effective procedure enabling rapid rehabilitation of visual acuity with low postoperative pain compared to PRK. There is no difference between the three techniques regarding refractive outcome after 3 months follow-up. LDV Z4® femto-LASIK can be recommended, if available, due to its low intraoperative complication rate and higher patient satisfaction compared to LenSx® femto-LASIK.
Purpose
The main aim of this study was to compare the efficacy, safety, and predictability of femtosecond laser-assisted in situ keratomileusis performed by two different laser suites in the treatment of myopia for up to 6 months.
Methods
In this two-site retrospective nonrandomized study, myopic eyes that underwent laser-assisted in situ keratomileusis using IntraLase FS 60 kHz formed group 1 and those using WaveLight FS200 femtosecond laser system formed group 2. Ablation was performed with Visx Star S4 IR and WaveLight EX500 Excimer lasers, respectively, in groups 1 and 2. Both groups were well matched for age, sex, and mean level of preoperative refractive spherical equivalent (MRSE). Uncorrected distance visual acuity, corrected distance visual acuity, and MRSE were evaluated preoperatively and at 1 week, 1 month, and 6 months after treatment.
Results
Fifty-six eyes of 28 patients were included in the study. At 6-month follow-up postop, 78.6% of eyes in group 1 and 92.8% of eyes in group 2 achieved an uncorrected distance visual acuity of 20/20 or better (P=0.252). 35.7% and 50% in group 1 and group 2, respectively, gained one line (P=0.179). No eye lost lines of corrected distance visual acuity. Twenty-five eyes in group 1 (92.7%) and 27 eyes in group 2 (96.3%) had MRSE within ±0.5 D in the 6-month follow-up (P>0.999). The mean efficacy index at 6 months was similar in group 1 and group 2 (mean 1.10±0.12 [standard deviation] vs 1.10±0.1) (P=0.799). The mean safety index was similar in group 1 and group 2 (mean 1.10±0.10 [standard deviation] vs 1.10±0.09) (P=0.407). Conclusion: The outcomes were excellent between the two laser suites. There were no significant differences at 6-month follow-up postop between the two laser systems.
PurposeTo assess the anterior chamber (AC) characteristics and its correlation to laser flare photometry immediately after femtosecond laser-assisted capsulotomy and photodisruption.Patients and methodsThe study included 97 cataract eyes (n=97, mean age 68.6 years) undergoing femtosecond laser-assisted cataract surgery (FLACS). Three cohorts were analysed relating to the flare photometry directly post femtosecond laser treatment (flare <100 n=28, 69.6±7 years; flare 100-249 n=47, 67.7±8 years; flare >249 photon counts per ms cohort n=22, 68.5±10 years). Flare photometry (KOWA FM-700), corneal topography (Oculus Pentacam, Germany: AC depth, volume, angle, pachymetry), axial length, pupil diameter, and endothelial cells were assessed before FLACS, immediately after femtosecond laser treatment and 1 day postoperative (LenSx Alcon, USA). Statistical data were analysed by SPSS v19.0, Inc.ResultsThe AC depth, AC volume, AC angle, central and thinnest corneal thickness showed a significant difference between flare <100 vs flare 100-249 10 min post femtosecond laser procedure (P=0.002, P=0.023, P=0.007, P=0.003, P=0.011, respectively). The AC depth, AC volume, and AC angle were significantly larger (P=0.001, P=0.007, P=0.003, respectively) in the flare <100 vs flare >249 cohort 10 min post femtosecond laser treatment.ConclusionsA flat AC, low AC volume, and a narrow AC angle were parameters associated with higher intraocular inflammation. These criteria could be used for patient selection in FLACS to reduce postoperative intraocular inflammation.Eye advance online publication, 27 May 2016; doi:10.1038/eye.2016.110.
Purpose:
To assess the alterations of the anterior chamber conditions including laser flare photometry after femtosecond laser-assisted cataract surgery (FLACS) compared to the manual phacoemulsification.
Methods:
Data of n=70 FLACS (mean age 67.2 ± 8.9 years) and n=40 manual phacoemulsification (mean age 69.5 ± 9.6 years) were analyzed. The procedures were performed by LenSx Alcon, USA, and Alcon Infiniti Vision System, USA. The following parameters were recorded: laser flare photometry (Kowa FM 700, Japan), anterior chamber (AC) depth, AC volume, AC angle (Pentacam, Oculus Inc., Germany), lens density, pupil diameter, endothelial cell count and pachymetry. The analysis was performed preoperatively, immediately after femtosecond laser procedure and one day postoperatively.
Results:
Between FLACS and the phaco control group, there was a significant difference in the AC depth (p=0.023, 3.77 mm vs. 4.05 mm) one day postoperatively. The AC angle (p=0.016) showed a significant difference immediately after the femto laser treatment. The central and thinnest pachymetry and endothelial cell count did not show a significant difference between the two study cohorts (p=0.165, p=0.291, p=0.979). The phaco cohort (n=40) demonstrated a non-statistically significant difference in the flare photometry of 15.80 photons/ms one postoperative day compared to the FLACS group 26.62 photons/ms (p=0.322).
Conclusion:
In this study population, no evidence for an additive damage caused by the use of the femtosecond laser was demonstrated. Furthermore, no increase in the central and thinnest corneal thickness and no increased endothelial cell loss was demonstrated by the laser energy.
Purpose
The aim of this study was to review and meta-analyze whether there are differences between reported femtosecond (FS) lasers for laser-assisted in situ keratomileusis (LASIK) in terms of efficacy, predictability, and safety as primary outcomes and corneal flap thickness measurements and pre- and postoperative complications as secondary outcomes.
Methods
A comprehensive literature search of PubMed, Science Direct, Scopus, and Cochrane CENTRAL Trials Library databases was conducted to identify the relevant prospective randomized controlled trials of FS lasers for LASIK. Thirty-one articles describing a total of 5,404 eyes were included.
Results
Based on efficacy, IntraLase FS 10 and 30 kHz gave the best results. Based on predictability and safety, there were no differences between various FS lasers. FEMTO LDV and IntraLase FS 60 kHz produced the most accurate flap thicknesses. IntraLase and Wavelight SF200 had the fewest intraoperative complications. IntraLase, Visumax, and Wavelight FS200 had the most seldom postoperative complications.
Conclusion
There were dissimilarities between different FS lasers based on efficacy and intraoperative and postoperative complications. All FS lasers were predictable and safe for making corneal flaps in LASIK.
To compare small incision lenticule extraction (SMILE) versus LASIK for post-refractive dry eye disease.
Prospective, comparative, nonrandomized clinical study.
Thirty patients scheduled for bilateral myopic SMILE and 30 age-, sex-, and refraction-matched patients scheduled for bilateral myopic LASIK were enrolled and followed for 6 months after the surgery.
Complete evaluation of dry eye disease was performed at 1 and 6 months postoperatively, which included vision-related quality of life (Ocular Surface Disease Index [OSDI]), clinical examinations (tear film breakup time [TBUT], Schirmer I test, corneal staining), and tear osmolarity measurements, together with an overall severity score. Function and morphology of the corneal innervation were evaluated by corneal esthesiometry and subbasal nerve imaging using in vivo confocal microscopy (IVCM).
Overall analysis of dry eye disease and corneal innervation.
High incidence of mild to moderate dry eye disease was observed in both groups 1 month postoperatively, which remained significantly higher in the LASIK group than in the SMILE group 6 months after surgery (overall severity score [0-4]: 1.2±1.1 vs. 0.2±0.4, respectively, P < 0.01), leading to more frequent use of tear substitutes over the long term. Corneal sensitivity was better in SMILE than in LASIK eyes 1 month postoperatively (3.5±1.79 vs. 2.45±2.48, respectively, P < 0.01) and then recovered to statistically similar values at 6 months. Corneal nerve density, number of long fibers, and branchings as assessed by IVCM were significantly higher in the SMILE group compared with the LASIK group 1 and 6 months after surgery. Corneal sensitivity was negatively correlated with dry eye-related corneal damage (R² = 0.48, P < 0.01), and the long fiber nerve density was independently correlated with the OSDI score (R² = 0.50, P < 0.01) and the Schirmer test (R² = 0.21, P < 0.01) 6 months postoperatively.
The SMILE procedure has a less pronounced impact on the ocular surface and corneal innervation compared with LASIK, further reducing the incidence of dry eye disease and subsequent degradation in quality of life after refractive surgery.
Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
To evaluate longitudinal changes in corneal sensitivity, tear function, and corneal staining in patients who underwent laser in situ keratomileusis (LASIK) using two different femtosecond lasers.
In a prospective, randomized clinical trial, contralateral eyes of 45 patients underwent flap creation by either VisuMax or IntraLase™ femtosecond laser. Corneal sensitivity, tear break up time (TBUT), Schirmer's test, and corneal fluorescein staining were assessed preoperatively and at 1 week, 1 month, and 3 months postoperatively.
There were no statistical differences in any clinical outcome measure between the two femtosecond lasers (P > 0.05), although there was a trend towards slightly lower reductions for corneal sensitivity and TBUT in VisuMax-operated eyes. Overall, corneal sensitivity was significantly reduced at 1 week (P < 0.05), 1 month (P < 0 .001), and 3 months (P < 0.001) postoperatively. A significantly greater reduction of corneal sensitivity was noted in eyes with a myopic spherical equivalent of -6.00 diopters (D) to -11.25 D as compared with eyes that had a relatively lower level of myopia of less than -6.00 D (P < 0.001). TBUT and Schirmer's test values were significantly diminished at 1 week postoperatively (P < 0.04). Overall, corneal staining was significantly increased at 1 week postoperatively (P < 0.001). The level of myopia did not significantly affect postoperative changes in TBUT, Schirmer's test values, or corneal staining (P > 0.05).
This study showed that changes in corneal sensitivity, tear function, and corneal staining were statistically similar in LASIK using VisuMax and IntraLase femtosecond lasers for flap creation. However, the trend towards faster recovery of corneal sensitivity and TBUT observed in VisuMax-operated eyes may be attributable to improved technical specifications.
To evaluate the safety, efficacy, and predictability of IntraLase (Abbott Medical Optics) femtosecond laser-assisted compared to microkeratome-assisted myopic LASIK.
A comprehensive literature search of Cochrane Library, PubMed, and EMBASE was conducted to identify relevant trials comparing LASIK with IntraLase femtosecond laser to LASIK with microkeratomes for the correction of myopia. Meta-analyses were performed on the primary outcomes (loss of ≥2 lines of corrected distance visual acuity [CDVA], uncorrected distance visual acuity [UDVA] 20/20 or better, manifest refraction spherical equivalent [MRSE] within ±0.50 diopters [D], final refractive SE, and astigmatism), and secondary outcomes (flap thickness predictability, changes in higher order aberrations [HOAs], and complications).
Fifteen articles describing a total of 3679 eyes were identified. No significant differences were identified between the two groups in regards to a loss of ≥2 lines of CDVA (P=.44), patients achieving UDVA 20/20 or better (P=.24), final UDVA (P=.12), final mean refractive SE (P=.74), final astigmatism (P=.27), or changes in HOAs. The IntraLase group had more patients who were within ±0.50 D of target refraction (P=.05) compared to the microkeratome group, and flap thickness was more predictable in the IntraLase group (P<.0001). The microkeratome group had more epithelial defects (P=.04), whereas the IntraLase group had more cases of diffuse lamellar keratitis (P=.01).
According to the available data, LASIK with the IntraLase femtosecond laser offers no significant benefits over LASIK with microkeratomes in regards to safety and efficacy, but has potential advantages in predictability.
PURPOSE
To study the current practice styles and preferences of refractive surgeons in Germany.
METHODS
In February 2008, a seven-item questionnaire regarding the practice of refractive surgery was mailed to 282 members of the German Society of Intraocular Lens Implantation, Interventional, and Refractive Surgery (DGII) and the Commission of Refractive Surgery (KRC). Most questions were identical to our 2005 German refractive surgery survey. All data were analyzed in a masked fashion.
RESULTS
The response rate was 42.2%. The majority (68%) of respondents reported that they perform refractive surgery in laser centers (exclusively or partially) followed by general hospitals (19.4%) and universities (12.6%). Although LASIK was the predominant type of refractive surgery performed (80.6%), other refractive procedures included refractive lens exchange (60.2%), photorefractive keratectomy (47.6%), phakic intraocular lens implants (45.6%), laser-assisted subepithelial keratectomy (36.9%), epithelial laser in situ keratomileusis (15.5%), intracorneal rings (5.8%), and limbal relaxing incisions (2.9%). The volume of refractive surgery procedures and the preferred type of excimer laser systems, microkeratomes, and diagnostic devices varied at different institutions. Most respondents performed either wavefront-guided custom ablation or wavefront-optimized ablation (63.1%) compared with conventional excimer laser correction (36.9%).
CONCLUSIONS
Refractive surgery practice styles and preferences in Germany are comparable to trends in other European countries. Although LASIK is the most commonly performed refractive procedure, the numbers of various surface ablation techniques and refractive intraocular lens procedures are increasing. [J Refract Surg. 2010;26:202–208.]
Purpose
To analyze the effects of variations in femtosecond laser energy level on corneal stromal cell death and inflammatory cell influx following flap creation in a rabbit model.
Methods
Eighteen rabbits were stratified in three different groups according to level of energy applied for flap creation (six animals per group). Three different energy levels were chosen for both the lamellar and side cut: 2.7 µJ (high energy), 1.6 µJ (intermediate energy), and 0.5 µJ (low energy) with a 60 kHz, model II, femtosecond laser (IntraLase). The opposite eye of each rabbit served as a control. At the 24-hour time point after surgery, all rabbits were euthanized and the corneoscleral rims were analyzed for the levels of cell death and inflammatory cell influx with the terminal uridine deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and immunocytochemistry for monocyte marker CD11b, respectively.
Results
The high energy group (31.9±7.1 [standard error of mean (SEM) 2.9]) had significantly more TUNEL-positive cells in the central flap compared to the intermediate (22.2±1.9 [SEM 0.8], P=.004), low (17.9±4.0 [SEM 1.6], P⩽.001), and control eye (0.06±0.02 [SEM 0.009], P⩽.001) groups. The intermediate and low energy groups also had significantly more TUNEL-positive cells than the control groups (P⩽.001). The difference between the intermediate and low energy levels was not significant (P=.56). The mean for CD11b-positive cells/400× field at the flap edge was 26.1±29.3 (SEM 11.9), 5.8±4.1 (SEM 1.6), 1.6±4.1 (SEM 1.6), and 0.005±0.01 (SEM 0.005) for high energy, intermediate energy, low energy, and control groups, respectively. Only the intermediate energy group showed statistically more inflammatory cells than control eyes (P=.015), most likely due to variability between eyes.
Conclusions
Higher energy levels trigger greater cell death when the femtosecond laser is used to create corneal flaps. Greater corneal inflammatory cell infiltration is observed with higher femtosecond laser energy levels. [J Refract Surg. 2009;25:869–874.]
BACKGROUND: We investigated the role of laser pulse width in determining fluence thresholds and efficiency for corneal photodisruption.
METHODS: A laser system that delivers a wide range of pulse energies and pulse widths was used to produce ablations at pulse widths from 100 femtoseconds (fs) to 7 nanoseconds (ns). The laserinduced breakdown fluence threshold at each pulse width was determined by monitoring individual plasma emissions. Using multiple shots, the photodisruption threshold and cutting depth at each pulse width were determined histologically.
RESULTS: Corneal breakdown thresholds decreased at a faster rate from 7 ns to approximately 10 picoseconds (ps), compared to further reductions in pulse width below 10 ps, where little variation was seen. Breakdown for pulse widths below 10 ps showed little intershot variability, resulting in highly reproducible fluence thresholds. Corneal tissue examined histologically showed similar fluence dependency.
CONCLUSIONS: Corneal tissue photodisruption thresholds demonstrate pulse width dependence. At pulse widths less than 10 ps and with fluences near the breakdown threshold, ablations are maximally precise and efficient. These findings suggest optimal laser parameters for corneal surgery. [J Refract Surg 1997;13:653-6581
PURPOSE: To describe a new technique for excimer laser corneal surgery: laser epithelial keratomileusis (LASEK).
METHODS: We report 76 eyes with spherical equivalent refractive myopia ranging from -8.00 to -22.00 D (mean -11.00 ± 3.00 D). Using ethanol applied over an 8.5-mm-diameter area for 20 seconds, the epithelium was detached and photorefractive keratectomy (PRK) was performed. The epithelium was reapplied to the ocular surface and covered with a therapeutic soft contact lens. Treatments were carried out with the Nidek EC-5000 excimer laser.
RESULTS: At a mean of 803 days after LASEK, mean spherical equivalent refraction was -1.80 ± 2.40 D (range -9.27 to +2.00 D). Stability was reached in approximately 60 days. Fifty-nine percent of the epithelial flaps were easy to detach intact during surgery and 62.7% of patients reported no postoperative pain. Eighty-four percent of eyes had the therapeutic bandage lens removed by the fourth postoperative day. Twelve percent of eyes had incomplete epithelial flap removal. Epithelium can fall off the cornea during the healing phase. No significant subepithelial haze was seen in 95% of eyes.
CONCLUSION: With LASEK, it may be possible to treat a larger diameter ablation zone in thinner corneas without the problems of a LASDX stromal flap and with less postoperative pain than PRK, with minimal subepithelial haze. [J Refract Surg 2003;19:666-670]
To evaluate the changes in spontaneous and stimulus-evoked nerve impulse activity of corneal polymodal and mechanonociceptor sensory fibers of the cornea after photorefractive keratectomy (PRK).
A central corneal ablation 6 mm in diameter and 70 microm in depth was performed with an excimer laser in both eyes of three anesthetized cats, after removal of the corneal epithelium. Single nerve fiber activity was recorded in these animals 12 to 48 hours after surgery. Activity in corneal nerve fibers with receptive fields (RFs) within and/or close to the wound, as well as with RFs far from the lesioned area, was studied. Incidence and frequency of spontaneous discharges and nerve impulse firing responses to mechanical (Cochet-Bonet esthesiometer) and chemical (CO(2) gas pulses) stimuli were studied.
The incidence of nociceptor fibers exhibiting ongoing activity (15/35 vs. 1/9) and the frequency of their spontaneous firing (0.25 +/- 0.09 impulses [imp]/s versus 0.08 +/- 0.08 imp/s) was higher in fibers with RFs within and/or bordering the wounded area than in those with RFs far away from the wound. Mechanical responsiveness of fibers with RFs within or nearby the ablated area was often reduced. In these fibers, CO(2) pulses evoked a lower-frequency impulse discharge (0.9 +/- 0.2 imp/s inside, 2.3 +/- 0.7 imp/s outside the wound). CO(2)-evoked discharges recorded from fibers innervating the intact wound border were similar to those recorded in corneal fibers of intact cats.
The spontaneous impulse activity and the abnormal responsiveness shown by a part of the corneal nerve fibers innervating the injured cornea are presumably the neurophysiological substrate of the pain sensations experienced by human patients hours after PRK surgery.
Purpose
To report on four different commercially available femtosecond laser systems used in refractive surgery.
Methods
Four systems were analyzed: Ziemer DaVinci system, Zeiss VisuMax, IntraLase FS laser, and 20/10 Perfect Vision FEMTEC.
Results
The DaVinci system attracts attention with its concept of low laser pulse energy and flexible mirror arm as a beam delivery. The low pulse energy makes it compact and robust, because only an oscillator as a laser source is required. Another important feature of the low energy pulses is the reduced bubble formation during the cutting process. The smaller the bubbles, the more precise the cut can be positioned. However, the compact setup limits the system in its flexibility in cutting geometry. The VisuMax also uses the new generation of femtosecond technology, which should make it more immune to environmental and temperature changes. However, it is a bulky system, and the patient has to be moved to the excimer laser system after the flap is created. The IntraLase is the laser with the most clinical experience by far, which should be an important issue in terms of safety and technical support. On the other hand, it uses older femtosecond laser technology. This technology is sensitive to changes in temperature or humidity, which can be an important factor if the surgical environment is not air conditioned. The 20/10 Perfect Vision FEMTEC system is comparable with the IntraLase with respect to its technical parameters. However, no data are available about the amount of clinical experience.
Conclusions
Although the systems are based on the same principle of photodisruption in corneal tissue, differences exist regarding the concept of these devices.
[J Refract Surg. 2008;24:S102–S107.]
Purpose
To explain the basic science and clinical evidence that has led to the development of a new technique in corneal refractive surgery—sub-Bowman's keratomileusis (SBK).
Methods
A comprehensive review of the literature and report of a contralateral eye study of 50 patients (100 eyes) enrolled at 2 sites (25 patients per site) and randomized according to the dominant eye was conducted. All eyes underwent a wavefront-guided refractive correction using the Alcon LADARVision4000 System. In one eye, an 8.5-mm, ETOH-assisted photorefractive keratectomy (PRK) was performed. In the second eye, an 8.5-mm, 100-µm flap was attempted using a 60 kHz IntraLase FS femtosecond laser. Pre- and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity, corneal topography, wavefront aberrometry, retinal image quality, contrast sensitivity, and biomechanical response of the cornea. Patients completed subjective questionnaires at each follow-up.
Results
Clinical results demonstrate that SBK provides quicker visual recovery, although the data suggest that the 3- and 6-months results are similar in terms of visual outcomes. Reichert Ocular Response Analyzer results demonstrate that its impact on the cornea is similar to PRK.
Conclusions
This study indicates that SBK provides the visual recovery of a LASIK procedure with the Optical Response Analyzer results similar to PRK. [J Refract Surg. 2008;24:S77–S84.]
Purpose
To compare the postoperative clinical outcomes of single-step transepithelial photorefractive keratectomy (PRK) and femtosecond-assisted laser in situ keratomileusis (LASIK).
Setting
Bergman Clinics, Utrecht, the Netherlands.
Design
Retrospective case series.
Methods
The eyes of consecutive patients who had transepithelial PRK were retrospectively compared with the same number of case-matched eyes (based on the preoperative refractive components) treated with femtosecond-assisted LASIK. The clinical outcomes evaluated were predictability, refractive outcomes, and visual acuity. The Student t test and chi-square test were used for statistical analysis.
Results
The study compared 98 patients (196 eyes) who had transepithelial PRK with the outcomes in 196 case-matched eyes that had femtosecond-assisted LASIK. All patients completed the 1-year follow-up. At 1 year, 130 eyes (66%) in the transepithelial PRK group and 91 eyes (46%) in the femtosecond-assisted LASIK group achieved an uncorrected distance visual acuity of −0.1 logMAR or better (P < .005), 4 eyes (2%) in the transepithelial PRK and 2 eyes (1%) in the femtosecond-assisted LASIK group lost 2 lines of corrected distance visual acuity (P = .04), and 163 eyes (83%) in the transepithelial PRK and 167 eyes (85%) in the femtosecond-assisted LASIK group were within ±0.50 diopter (D) of emmetropia. The postoperative mean spherical equivalent was +0.11 D ± 0.56 (SD) for transepithelial PRK and −0.09 ± 0.46 D for femtosecond-assisted LASIK (P < .0001).
Conclusions
Transepithelial PRK outcomes 1 year postoperatively were equivalent to those of femtosecond-assisted LASIK. Transepithelial PRK was efficacious and safe; however, the procedure had a longer recovery time than the femtosecond-assisted LASIK.
Financial Disclosure
Mr. Ewering and Dr. Arba-Mosquera are employees of Schwind eye-tech-solutions GmbH and Co. KG. Dr. Luger has no financial or proprietary interest in any material or method mentioned.
Purpose:
To compare keratocyte activation, cellular morphologic changes and wound healing after SMILE and PRK procedures using transmission electron microscope (TEM).
Methods:
In this study, 22 New Zealand white rabbits (10- to 15-week old) were used. The right eyes of all animals underwent SMILE procedure and the left eyes underwent PRK procedure. Cornea samples taken 1 day and 1 week postoperatively were examined using TEM.
Results:
Using TEM 1 day after SMILE procedure, the organization of collagen fibers seemed to have been preserved without thermal alterations. Keratocyte activation was observed in the anterior stroma. Disrupted collagen arrangement and debris of cells are visible in the area of damage, and some phagocytic cells and a large number of secondary lysosomes are visible in those cells. At the perimeter zone of the interface, many coenocytes and collagen fragments could be found within the phagocytic cell. One week after SMILE procedure, potential lacuna could be discerned. A large part of the interface of the lenticule extracted had an appearance of clearly being adhered to some mucus secretions. One day after PRK procedure, an irregular epithelial surface was visible using TEM. Keratocytes had been activated and the rough endoplasmic reticulum in those cells had expanded. One week after PRK procedure, the epithelial surface still was irregular and keratinization of the epithelium was still visible in some areas. Corneal endothelium cells were mildly damaged and some vacuoles within the cytoplasm could be discerned. In the anterior stroma, some unhealthy activated keratocytes could still be observed. New collagen fibrils were found present near the activated keratocytes.
Conclusion:
Using TEM, keratocyte activation could still be observed after SMILE compared to after PRK procedure. Fewer cellular ultrastructural changes were seen after SMILE procedure. Unlike in PRK procedure, no damaged epithelium and endothelium were found after SMILE.
To compare laser in situ keratomileusis (LASIK) outcomes between 2 femtosecond lasers for flap creation in the treatment of myopia up to 1 year.
University eye clinic.
Prospective randomized eye-to-eye study.
Consecutive myopic patients were treated with wavefront-guided LASIK. One eye had a flap created by the Intralase FS 60 kHz femtosecond laser, and the fellow eye was treated with the Intralase iFS 150 kHz femtosecond laser. Eyes were randomized according to ocular dominance. Evaluations included measurement of uncorrected distance visual acuity (UDVA), corrected distance visual acuity, contrast sensitivity and wavefront aberrometry.
The study enrolled 122 eyes of 61 patients. The mean preoperative spherical equivalent refraction was -4.62 diopters (D) ± 2.32 (SD) and -4.66 ± 2.30 D in the 150 kHz group and 60 kHz group, respectively. Patients preferred the 150 kHz laser to the 60 kHz laser intraoperatively (52.5% versus 26.2%) (P = .005). One week postoperatively, UDVA was 20/16 or better in 85.2% in the 150 kHz group and 70.5% in the 60 kHz group; the difference was statistically significant (P < .05). At 12 months, there were no significant differences in refractive outcomes or higher-order aberrations between the 2 groups.
Flap creation with the 150 kHz system and the 60 kHz system resulted in excellent LASIK outcomes. Intraoperatively, patients preferred the 150 kHz system, which yielded better UDVA in the early postoperative period. There were no significant differences at 1 year between the 2 laser systems.
Proprietary or commercial disclosures are listed after the references.
Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
Die moderne korneale Hornhautchirurgie zur Korrektur von Fehlsichtigkeiten erfordert eine präzise, zuverlässige und reproduzierbare Erzeugung von Hornhautlentikeln (Flaps). Die Verwendung von ultrakurzen Laserpulsen im Zeitbereich von wenigen 100 fs (10-13 s) bietet die Möglichkeit, okuläres Gewebe ohne thermischen Einfluss auf umliegende Gewebestrukturen zu schneiden. Über mechanisch-optische Adaption der Femtosekundenlaser an das Gewebe lassen sich heute sehr dünne Flaps mit einer mittleren Dicke von 100 µm und einer hohen Reproduzierbarkeit (Standardabweichung ca. 10 µm) erzeugen. Somit bieten Femtosekundenlaser bereits heute eine Alternative zu herkömmlichen mechanischen Mikrokeratomen. Bezüglich Sicherheit im klinischen Einsatz sind die Femtosekundenlaser und die mechanischen Mikrokeratome durchaus vergleichbar.
Background
The purpose of this study was to investigate the influence of different postoperative treatments on the wound healing reaction in the anterior stroma after PRK and in the interface area after LASIK.
Methods
Seventy-two corneal buttons of refractively treated rabbit eyes underwent different postoperative eyedrop regimens with antibiotics and/or steroids or additional UV-B irradiation. Morphological and immunohistological investigations were performed 6 months postoperatively by light and transmission electron microscopy.
Results
PRK eyes showed interdigitations between the epithelia and the anterior stroma. LASIK-treated eyes showed only minor changes between epithelia and stroma in the incisional region. Only a slight increase in deposits of fibrillar extracellular matrix components were detectable in the interface region.
Conclusions
The clinically important problem of haze after PRK is caused by the interdigitations between epithelia and anterior stroma. The delicate wound healing reactions in the interface region in LASIK eyes corresponded to the clinically visible minor changes in these corneas.
Purpose:
To compare the efficacy, predictability, and refractive outcomes of laser in situ keratomileusis (LASIK) using 2 femtosecond platforms for flap creation.
Setting:
Multisurgeon single center.
Design:
Clinical trial.
Methods:
Bilateral femtosecond LASIK was performed using the Wavelight Allegretto Eye-Q 400 Hz excimer laser system. The Visumax femtosecond platform (Group 1) was used to create the LASIK flap in 1 eye, while the Intralase femtosecond platform (Group 2) was used to create the LASIK flap in the contralateral eye. The preoperative, 1-month, and 3-month postoperative visual acuities, refraction, and contrast sensitivity in the 2 groups were compared.
Results:
The study enrolled 45 patients. Three months after femtosecond LASIK, 79.5% of eyes in Group 1 and 82.1% in Group 2 achieved an uncorrected distance visual acuity of 20/20 (P=.808). The mean efficacy index was 0.97 in Group 1 and 0.98 in Group 2 at 3 months (P=.735); 89.7% of eyes in Group 1 and 84.6% of eyes in Group 2 were within ± 0.50 diopter of emmetropia at 3 months (P=.498). No eye in either group lost more than 2 lines of corrected distance visual acuity. The mean safety index at 3 months was 1.11 in Group 1 and 1.10 in Group 2 (P=.570).
Conclusion:
The results of LASIK with both femtosecond lasers were similar, and both platforms produced efficacious and predictable LASIK outcomes.
Financial disclosure:
No author has a financial or proprietary interest in any material or method mentioned.
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.
To compare the safety and efficacy of wavefront-guided laser in situ keratomileusis (LASIK) vs photorefractive keratectomy (PRK) in a prospective randomized clinical trial.
A cohort of 68 eyes of 34 patients with -0.75 to -8.13 diopters (D) of myopia (spherical equivalent) were randomized to receive either wavefront-guided PRK or LASIK in the fellow eye using the VISX CustomVue laser. Patients were evaluated at 1 day, 1 week, and months 1, 3, 6, and 12.
At 1 month, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), 5% and 25% contrast sensitivity, induction of higher-order aberrations (HOAs), and subjective symptoms of vision clarity, vision fluctuation, ghosting, and overall self-assessment of vision were worse (P<0.05) in the PRK group. By 3 months, these differences had resolved (P>0.05). At 1 year, mean spherical equivalent was reduced 94% to -0.27 ± 0.31 D in the LASIK group and reduced 96% to -0.17 ± 0.41 D in the PRK group. At 1 year, 91% of eyes were within ±0.50 D and 97 % were within ±1.0 D in the PRK group. At 1 year, 88% of eyes were within ±0.50 D and 97% were within ±1.0 D in the LASIK group. At 1 year, 97% of eyes in the PRK group and 94% of eyes in the LASIK group achieved an UCVA of 20/20 or better (P=0.72). Refractive stability was achieved in both PRK and LASIK groups after 1 month. There were no intraoperative or postoperative flap complications in the LASIK group. There were no instances of corneal haze in the PRK group.
Wavefront-guided LASIK and PRK are safe and effective at reducing myopia. At 1 month postoperatively, LASIK demonstrates an advantage over PRK in UCVA, BSCVA, low-contrast acuity, induction of total HOAs, and several subjective symptoms. At postoperative month 3, these differences between PRK and LASIK results had resolved.
To compare the course of intraocular pressure (IOP) during corneal flap preparation using four different femtosecond lasers in porcine globes.
Forty-eight (12 in each group) enucleated globes were successfully cannulated through the optic nerve. Intraocular pressure was measured continuously through the cannula during a normal lamellar flap creation (regular procedure) using four femtosecond lasers (IntraLase, Abbott Medical Optics; VisuMax, Carl Zeiss Meditec AG; Femtec, Technolas Perfect Vision; and Femto LDV, Ziemer Ophthalmic Systems AG). In an additional measurement (worst-case procedure), the patient interface was pressed against the globe with increasing force until the applanation maneuver was automatically aborted by those devices capable of doing so.
During the regular procedure, the maximum IOP reached was 135±16 mmHg when using the Intra-Lase, 65±20 mmHg with the VisuMax, 205±32 mmHg with the Femtec, and 184±28 mmHg with the Femto LDV. During the worst-case procedure, a maximum IOP of 260±53 mmHg was reached with the IntraLase, 105±13 mmHg with the VisuMax, and 248±51 mmHg with the Femtec.
There is considerable variation in IOP among the tested femtosecond lasers during a regular lamellar flap creation and during the worst-case procedure. The VisuMax femtosecond laser seems to cause the lowest IOP rise in both settings.
To compare visual outcomes between wavefront-guided photorefractive keratectomy (PRK) and wavefront-guided laser in situ keratomileusis (LASIK).
Academic center, Salt Lake City, Utah, USA.
In this randomized prospective study, myopic eyes were treated with wavefront-guided PRK and or wavefront-guided LASIK using a Visx Star S4 CustomVue platform with iris registration. Primary outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities and manifest refraction. Secondary outcome measures were higher-order aberrations (HOAs) and contrast sensitivity.
The PRK group comprised 101 eyes and the LASIK group, 102 eyes. At 6 months, the mean UDVA was -0.03 logMAR +/- 0.10 [SD] (20/19) and 0.07 +/- 0.09 logMAR (20/24), respectively (P = .544). In both groups, 75% eyes achieved a UDVA of 20/20 or better (P = .923); 77% of eyes in the PRK group and 88% in the LASIK group were within +/-0.50 diopter of emmetropia (P = .760). There was no statistically significant difference between groups in contrast sensitivity at 3, 6, 12, or 18 cycles per degree. The mean postoperative HOA root mean square was 0.45 +/- 0.13 mum in the PRK group and 0.59 +/- 0.22 mum in the LASIK group (P = .012), representing an increase factor of 1.22 and 1.74, respectively.
Wavefront-guided PRK and wavefront-guided LASIK had similar efficacy, predictability, safety, and contrast sensitivity; however, wavefront-guided PRK induced statistically fewer HOAs than wavefront-guided LASIK at 6 months.
No author has a financial or proprietary interest in any material or method mentioned.
For technical reasons, the rotating knives (microkeratomes) commonly used for flap creation in LASIK may induce cut complications such as buttonholes or incomplete flaps. Femtosecond (femto) lasers should reduce these risks because, compared with microceratomes, femtolasers work more precisely and individually, so the flap can be individualized according to the patient's eye condition. Therefore, surgery should be less of a strain to patients, vision should recover faster, and optical quality should be optimized.
In this study, 308 consecutive femtolaser cuts for myopic LASIK performed with the IntraLase FS60 between August 2006 and March 2008 were evaluated and compared with the approved key literature.
For all cuts, just three complications (incomplete ring cuts of about 20 degrees) occurred. All were completed with a diamond knife without any further problems. No other complications - including the typical microceratome-induced cut complications - were observed.
In this small series of 308 operations, femto-LASIK induced no major cut complications.
A new laser refractive procedure is being developed in a rabbit model. With a modified microkeratome, central corneal flaps were created. An ArF excimer laser was used to produce 3-mm-diameter circular ablations on the central part of the exposed stromal bed. One group of animals was sacrificed immediately postoperatively, and both the dissected and ablated areas were studied using scanning electron microscopy. A second group of animals was sacrificed 4 weeks postoperatively. In this group, the subsequent healing of the corneas was studied using light microscopy. At 3 days, the wounded stromal areas showed some degree of haze. Haze was progressively reduced over 1 month, but it could be still discerned biomicroscopically. A hemicircular opacification corresponding to the flap edges was also apparent on slit-lamp examination. Microscopic observation showed that the epithelium was normal, except at the flap margins, where it was thickened. An increased number of keratocytes was observed in the interface between the flap stroma and the ablated area. The procedure might induce stable corneal changes because of the preservation of the anterior layers of the cornea.
The excimer laser, which produces light in the far-ultraviolet portion of the spectrum, allows precise removal of corneal tissue through a photochemical laser-tissue interaction. This interaction is not thermal and does not involve optical breakdown; rather, it directly breaks organic molecular bonds without tissue heating. We used this process of ablative photodecomposition to remove corneal tissue in a series freshly enucleated cow eyes. Applying the far-ultraviolet light in short intense pulses permitted us to control the depth of the incision with great precision. We found that 1 joule/cm2 ablates corneal tissue to a depth of 1 micron. Adjacent tissue suffered no thermal damage and the stromal lamellae adjacent to the incision showed no evidence of disorganization.
To compare effectiveness, safety, and stability of excimer laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for low-to-moderate myopia.
Prospective, randomized, bilateral study.
Thirty-three patients with a manifest refraction of -2.50 to -8.00 diopters (D) participated.
For each patient, one eye received LASIK and the other received PRK. The first eye treated, and surgical method in the first eye, were randomized. Both eyes were treated by the same surgeon during the same operative session with a Summit Omnimed I laser (6-mm-diameter ablation) and a Chiron Automated Corneal Shaper. Follow-up was 90% at 1 and 2 years.
At baseline, mean (+/-standard deviation) spherical equivalent manifest refraction was -4.80 +/- 1.60 D in LASIK-treated eyes and -4.70 +/- 1.50 D in PRK-treated eyes. At 1 day after surgery, 81% of patients (21 eyes) reported no pain in the LASIK-treated eye, whereas no patient (0%) reported being pain-free in the PRK-treated eye. At 3 to 4 days after surgery, 18 (80%) LASIK-treated eyes either improved or remained within 1 line of baseline spectacle-corrected visual acuity; only 10 (45%) PRK-treated eyes achieved this result. At 2 years after surgery, 18 (61%) LASIK- and 10 (36%) PRK-treated eyes achieved an uncorrected visual acuity of 20/20 or better, with no statistically significant difference in refractive outcome between the two techniques. Quantitative videokeratography showed more regularity after LASIK. Complications were similar in the two groups. Patients preferred LASIK by a margin of 2 to 1 at 1 year but showed no preference at 2 years.
Using a 6-mm-diameter single-pass, large area ablation and an automated microkeratome to treat myopia of -2.50 to -8.00 D with 1.00 D or less astigmatism in 1994, the authors used LASIK to produce a higher percentage of eyes with an uncorrected visual acuity of 20/20 or better, more regular postoperative corneal topography, less postoperative pain, and more rapid recovery of baseline spectacle-corrected visual acuity than PRK. Both LASIK and PRK achieved successful correction of low-to-moderate myopia at 1 and 2 years after surgery.
To compare the effectiveness, safety, and stability of laser epithelial keratomileusis (LASEK), a modified photorefractive keratectomy (PRK) technique, with those of conventional PRK for low to moderate myopia.
Department of Ophthalmology, Yonsei University School of Medicine, Seoul, Korea.
In this prospective study, 27 patients with a manifest refraction of -3.00 to -6.50 diopters were treated and followed for 3 months. In each case, PRK was performed in 1 eye and LASEK in the other eye. The first eye treated and the surgical method used in the first eye were randomized. Postoperative pain, epithelial healing time, uncorrected visual acuity (UCVA), manifest refraction, corneal haze, and surgical preference were examined in PRK- and LASEK-treated eyes.
During the 3 month follow-up, there were no significant between-eye differences in epithelial healing time, UCVA, or refractive error. However, LASEK-treated eyes had lower postoperative pain scores (P =.047) and corneal haze scores (1 month; P =.02) than PRK-treated eyes. Seventeen patients (63%) preferred the LASEK procedure.
Laser epithelial keratomileusis safely and effectively treated eyes with low to moderate myopia. It reduced the incidence of significant postoperative pain and corneal haze and may prevent the flap- and interface-related problems of laser in situ keratomileusis.
The purpose of this study was to investigate the influence of different postoperative treatments on the wound healing reaction in the anterior stroma after PRK and in the interface area after LASIK.
Seventy-two corneal buttons of refractively treated rabbit eyes underwent different postoperative eyedrop regimens with antibiotics and/or steroids or additional UV-B irradiation. Morphological and immunohistological investigations were performed 6 months postoperatively by light and transmission electron microscopy.
PRK eyes showed interdigitations between the epithelia and the anterior stroma. LASIK-treated eyes showed only minor changes between epithelia and stroma in the incisional region. Only a slight increase in deposits of fibrillar extracellular matrix components were detectable in the interface region.
The clinically important problem of haze after PRK is caused by the interdigitations between epithelia and anterior stroma. The delicate wound healing reactions in the interface region in LASIK eyes corresponded to the clinically visible minor changes in these corneas.
Laser in situ keratomileusis
- I G Pallikaris
- M E Papatzanaki
- E Z Stathi
- IG Pallikaris
Retrospektive Studie zum Einfluss der Hornhautdicke auf die Zielgenauigkeit der wellenfrontoptimierten Femto-LASIK
- J Stabel
- S Münster
- J Heymanns
- Febrer Bowen
Photodisruption in the human cornea as a function of laser pulse width
- R M Kurtz
- X Liu
- V M Elner
- RM Kurtz
Intraocular pressure during corneal flap preparation: comparison among four femtosecond lasers in porcine eyes
- J M Vetter
- M P Holzer
- C Teping
- JM Vetter