Comparison of the Levels of Transforming Growth Factor-ß1 in Tear Fluid in Patients with High Myopia after Transepithelial Photorefractive Keratectomy and Laser Subepithelial Keratomileusis (LASEK).

We compared the level of transforming growth factor-ß1 (TGF-ß1) in the tear fluid of 20 patients with high myopia who underwent transepithelial photorefractive keratectomy (T-PRK) in one eye and laser subepithelial keratomileusis (LASEK) in the contralateral eye. Tear fluid samples were collected with scaled microcapillary tubes before (day 0) and on days 1, 3, and 5 after surgery. The release of TGF-ß1 was determined by multiplying the concentration of TGF-ß1 by capillary tear fluid flow. Corneal haze was also evaluated in 1, 3, and 6 months after surgeries. The median TGF-ß1 release after T-PRK and LASEK differed significantly on days 1 and 3 (p<0.005) and on day 5 (p<0.05). The mean corneal haze score after T-PRK and LASEK also significantly differed in 1 month (p<0.005), but no significant differences in this parameter were revealed at later terms. Thus, the level of TGF-ß1 in the tear fluid after T-PRK was lower than after LASEK, which can be the cause of less pronounced corneal haze in 1 month after surgery.

[Influence of Different Ablation Frequencies on the Clinical Results of Photorefractive Keratectomy Using the Same Excimer Laser Platform: A Contralateral Eye Study]. / Einfluss unterschiedlicher Ablationsfrequenzen auf die klinischen Ergebnisse bei photorefraktiver Keratektomie unter Verwendung derselben Excimer-Laser-Plattform: Ein kontralateraler Vergleich.

Background The objective of this study was to evaluate postoperative clinical outcomes of photorefractive keratectomy (PRK) using different ablation frequencies. Patients and Methods In this prospective, contralateral eye study, 56 eyes of 28 patients with myopia or myopic astigmatism were included. PRK was performed using the MEL90 excimer laser system (Carl Zeiss Meditec, Germany). One eye of each patient was treated with a repetition rate of 250 Hz, while the other one was treated with a repetition rate of 500 Hz. The treatment pattern in the 250 Hz and 500 Hz group only differed in terms of ablation frequency; there was no difference in laser pulse energy, spot size or ablation profile. Postoperative follow-ups were at 3 and 7 days and 1, 3 and 6 months. The following parameters were assessed: Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), higher-order aberrations (HOAs), corneal re-epithelisation time and corneal haze. Results Ablation depth was proportional to laser pulse counts at both frequencies. At 6 months, 100.0% of the eyes in the 250 Hz group and 96.4% in the 500 Hz group had a UDVA of 0.00 logMAR or better; 100% of the eyes in both groups were within ± 1.00D of the attempted correction. All eyes had a postoperative CDVA of 0.00 logMAR or better. There was no difference between the groups in postoperative HOAs, corneal re-epithelisation time or corneal haze. Conclusions Photorefractive keratectomy with a repetition rate of 250 Hz and 500 Hz showed comparable efficacy, safety and predictability in the correction of myopia. There were no significant complications due to the high repetition rate, such as postsurgical corneal haze.

[Riboflavin photoprotection with cross-linking effect in photorefractive ablation of the cornea]. / Fotoprotektsiya riboflavinom s effektom krosslinkinga pri fotorefraktsionnoi ablyatsii rogovitsy.

UNLABELLED: Photorefractive ablation is inevitably accompanied by oxidative stress of the cornea and weakening of its biomechanical and photoprotective properties. AIM: To validate the expediency of riboflavin use in photorefractive ablation for photoprotection of the cornea and cross-linking. MATERIAL AND METHODS: The effects of riboflavin use in photorefractive ablation was first studied in a series of in vitro and in vivo experiments performed on 56 eyes of 28 rabbits, and then on 232 eyes of 142 patients with different degrees of myopia. Biomechanical testing of corneal samples was performed with Zwick/RoellВZ 2.5/TN1S tensile-testing machine. Transepithelial photorefractive keratectomy (TransPRK) and femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) were performed on Wavelight-Allegretto200, MEL-80, and WaveLight-EX500 excimer laser systems and also VisuMax and WaveLight-FS200 femtosecond lasers. For preliminary examinations, an appropriate set of diagnostic tools was used. RESULTS: In vivo experiments have proved that, in the absence of conservative therapy, riboflavin is able to produce both photoprotective and cross-linking effects to the cornea. Corneal syndrome was thus reduced and re-epithelialization after TransPRK accelerated. Biomechanical testing of corneal samples revealed an increase in tolerated load from 12.9±1.4 N to 18.3±1.2 N (p=0.0002) and tensile strength from 8.6±1.7 MPa to 12.4±1.7 MPa (p=0.007). Clinical studies conducted in a group of patients with mild to moderate myopia have also confirmed the photoprotective effect of riboflavin at months 1-12 after TransPRK. There were no significant differences in uncorrected visual acuity (ranged from 0.80±0.16 to 0.85±0.15) and corrected visual acuity at baseline (0.83±0.14). Evaluation of the optical and refractive effect achieved after Femto-LASIK with riboflavin photoprotection in the fellow eye has shown that this technique is not inferior to the traditional one as to its refractive accuracy, but provides better maintenance of biomechanical and photoprotective properties of the cornea. CONCLUSION: Photorefractive ablation of the cornea with preliminary saturation of the stroma with riboflavin solution ensures its photoprotection and provides an additional cross-linking effect.

Excimer laser surface ablation - a review.

Corneal surface laser ablation procedures for the correction of refractive error have enjoyed a resurgence of interest, especially in patients with a possible increased risk of complications after lamellar surgery. Improvements in the understanding of corneal biomechanical changes, the modulation of wound healing, laser technology including ablation profiles and different methods for epithelial removal have widened the scope for surface ablation. This article discusses photorefractive keratectomy, trans-epithelial photorefractive keratectomy, laser-assisted sub-epithelial keratomileusis and epithelial-laser-assisted in situ keratomileusis.

Epi-Bowman Blunt Keratectomy Versus Diluted EtOH Epithelial Removal in Myopic Photorefractive Keratectomy: A Prospective Contralateral Eye Study.

PURPOSE: To compare the outcomes and complications of Epi-Bowman blunt keratectomy (EBK) using a blunt epikeratome (Epi-Clear, Orca Surgical, Israel), with alcohol delamination of the corneal epithelium during photorefractive keratectomy (PRK) in contralateral eyes. METHODS: This prospective, randomized contralateral eye study included 44 eyes of 22 patients undergoing PRK for bilateral myopia or myopic astigmatism. In each patient, epithelial delimitation was performed using an Epi-Clear epikeratome EBK (EBK group) on 1 eye and diluted ethanol (EtOH) on the fellow eye (EtOH group). Postoperative pain, epithelial healing, epithelial profile, and visual outcome were compared between the 2 groups. RESULTS: The mean postoperative pain scores were 0.37 ± 0.25 for the EBK group and 0.82 ± 0.22 for the EtOH group (P = 0.043). The mean epithelial defect size at day 3 postoperatively was 1.61 ± 1.46 and 2.25 ± 1.69 mm, respectively (P = 0.034). The postoperative 3-month remaining mean spherical equivalent was 0.04 ± 0.49 diopters for the EBK group and 0.21 ± 0.26 D for the EtOH group (P = 0.520). There was no significant difference in UCVA and BCVA between the groups. CONCLUSIONS: Our data suggest that this novel EBK device and technique may minimize postoperative pain, accelerate re-epithelialization, and offer earlier visual recovery, compared with EtOH when used for myopic PRK.

[Excimer laser trabeculotomy: minimally invasive glaucoma surgery]. / Minimal-invasive Glaukomchirurgie: Excimer-Laser-Trabekulotomie.

Excimer laser trabeculotomy (ELT) is a minimally invasive method for reducing intraocular pressure. It can be performed as a stand-alone procedure or in combination with cataract surgery in just a few minutes. Laser spots are applied in the anterior chamber angle via an endoscopic camera or a gonio lens. In contrast to argon laser trabeculoplasty, shunts between the anterior chamber and Schlemm's canal are prepared by a photoablative laser, thus improving the outflow of aqueous humour. Best results can be expected in patients with moderately elevated intraocular pressure and cataract undergoing the combined procedure.

Advanced Surface Ablation With a New Software for the Reduction of Ablation Irregularities.

PURPOSE: To compare visual outcomes and postoperative aberrations after surface ablation performed with a 750-Hz versus a 1,050-Hz excimer laser coupled with an ablation software designed to reduce corneal surface irregularity. METHODS: Retrospective comparative trial of myopic eyes that had refractive surgery consecutively treated with transepithelial advanced surface ablation with a 750-Hz excimer laser (750 group) versus a 1,050-Hz excimer laser coupled with the Smart Pulse Technology ablation software (SPT group). The SPT algorithm is a laser pulse technology software aimed at reducing surface irregularity of the stromal bed at the end of treatment. The authors evaluated the effect of this smoothing on final visual acuity. Patients were observed for 6 months. RESULTS: A total of 139 eyes in the 750 group and 40 eyes in the SPT group were evaluated. Epidemiological and preoperative refractive data of the two groups were comparable. Uncorrected distance visual acuity improved with time and was significantly better in the SPT group (-0.04 ± 0.61 logMAR for the SPT group vs 0.02 ± 0.78 logMAR for the 750 group) (P < .001). At 6 months, 55% versus 21% achieved 20/16 or better (P = .005) and 90% versus 65% achieved 20/20 or better (P = .019) visual acuity in the SPT and 750 groups, respectively. Corrected distance visual acuity improved with time and appeared to be influenced by group (P = .054), with better results in the SPT group. Coma and trefoil improved significantly with time in a similar manner in both groups. CONCLUSIONS: Surface ablation with the 1,050-Hz excimer laser and SPT software, aimed at reducing the final superficial stromal irregularity, led to improvement of 6-month uncorrected visual acuity. [J Refract Surg. 2017;33(2):89-95.].

Retrospective Analysis of the Post-Operative Changes in Higher-Order Aberrations: A Comparison of the WaveLight EX500 to the VISX S4 Laser in Refractive Surgery.

INTRODUCTION: In an attempt to maximize treatment outcomes, refractive surgery techniques are being directed toward customized ablations to correct not only lower-order aberrations but also higher-order aberrations specific to the individual eye. Measurement of the entirety of ocular aberrations is the most definitive means to establish the true effect of refractive surgery on image quality and visual performance. Whether or not there is a statistically significant difference in induced higher-order corneal aberrations between the VISX Star S4 (Abbott Medical Optics, Santa Ana, California) and the WaveLight EX500 (Alcon, Fort Worth, Texas) lasers was examined. METHODS: A retrospective analysis was performed to investigate the difference in root-mean-square (RMS) value of the higher-order corneal aberrations postoperatively between two currently available laser platforms, the VISX Star S4 and the WaveLight EX500 lasers. The RMS is a compilation of higher-order corneal aberrations. Data from 240 total eyes of active duty military or Department of Defense beneficiaries who completed photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) refractive surgery at the Wilford Hall Ambulatory Surgical Center Joint Warfighter Refractive Surgery Center were examined. Using SPSS statistics software (IBM Corp., Armonk, New York), the mean changes in RMS values between the two lasers and refractive surgery procedures were determined. A Student t test was performed to compare the RMS of the higher-order aberrations of the subjects' corneas from the lasers being studied. A regression analysis was performed to adjust for preoperative spherical equivalent. The study and a waiver of informed consent have been approved by the Clinical Research Division of the 59th Medical Wing Institutional Review Board (Protocol Number: 20150093H). RESULTS: The mean change in RMS value for PRK using the VISX laser was 0.00122, with a standard deviation of 0.02583. The mean change in RMS value for PRK using the WaveLight EX500 laser was 0.004323, with a standard deviation of 0.02916. The mean change in RMS value for LASIK using the VISX laser was 0.00841, with a standard deviation of 0.03011. The mean change in RMS value for LASIK using the WaveLight EX500 laser was 0.0174, with a standard deviation of 0.02417. When comparing the two lasers for PRK and LASIK procedures, the p values were 0.431 and 0.295, respectively. CONCLUSION: The results of this study suggest no statistically significant difference concerning induced higher-order aberrations between the two laser platforms for either LASIK or PRK. Overall, the VISX laser did have consistently lower induced higher-order aberrations postoperatively, but this did not reach statistical significance. It is likely the statistical significance of this study was hindered by the power, given the relatively small sample size. Additional limitations of the study include its design, being a retrospective analysis, and the generalizability of the study, as the Department of Defense population may be significantly different from the typical refractive surgery population in terms of overall health and preoperative refractive error. Further investigation of visual outcomes between the two laser platforms should be investigated before determining superiority in terms of visual image and quality postoperatively.

Automated visual axis alignment for refractive excimer laser ablation.

PURPOSE: To describe the use of new laser alignment and delivery software in the NIDEK Advanced Vision Excimer laser platform (NAVEX) that allows centration based on surgeon specification. METHODS: Descriptive article with a case report. RESULTS: The software allows specification via numeric entry of the exact placement of the laser tapered to the position of the visual axis or the line of sight. CONCLUSIONS: The ability to specify the exact location of the laser ablation based on pupil position is fundamental in patients undergoing custom ablation and those with eccentric fixation. A conservative treatment strategy is recommended for initial experience with this alignment software.

Alcon LADARWave customcornea retreatments.

PURPOSE: To present our experience performing wavefront-guided ablations for the treatment of residual refractive error following previous refractive surgery. METHODS: Four different cases are presented-1) primary wavefront-guided LASIK; 2) wavefront-guided lift-flap LASIK retreatment; 3) wavefront-guided photorefractive keratectomy (PRK) retreatment; and 4) wavefront-guided PRK over radial keratotomy retreatment. All procedures were performed with the Alcon CustomCornea laser platform. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and wavefront analysis (6.5-mm pupil) were performed preoperatively and 3 months after CustomCornea retreatment. The Alcon LADARWave device was used for wavefront measurements. RESULTS: Total lower order and higher order aberrations were decreased following wavefront-guided retreatment, resulting in improved quality of vision. The maximum target offset (+ 0.75 diopters) can be used to prevent an overcorrection of defocus (myopia) when treating a significant amount of spherical aberration. CONCLUSIONS: Wavefront-guided ablation was an effective treatment for residual lower and higher order aberrations following previous refractive surgery. Custom ablation treatment algorithms need to be developed specifically for retreatment procedures.

Optimized prolate ablations with the NIDEK CXII excimer laser.

PURPOSE: To describe a novel excimer laser ablation algorithm, termed optimized prolate ablation (OPA), that uses both topography and ocular aberrometry and maintains or improves the natural corneal shape postoperatively. METHODS: A descriptive article outlining the theory behind this OPA algorithm. RESULTS: The theoretical changes to the ablation algorithm described in this article will produce a prolate cornea postoperatively. CONCLUSIONS: OPA treated eyes will have equal or better visual quality than preoperatively because age-related changes from lenticular spherical aberration are measured and treated.

[LASIK using a scanning spot excimer laser for the treatment of myopia and myopic astigmatism 3-Jahresergebnisse]. / Laser-in-situ-Keratomileusis mittels Scanning-Spot-Excimerablation zur Korrektur von Myopie und myopem Astigmatismus 3-Jahresergebnisse.

PURPOSE: The correction of refractive errors using laser in situ keratomileusis (LASIK) has become the primary refractive procedure worldwide. The purpose of this study was to evaluate LASIK within a retrospective cohort. PATIENTS AND METHODS: The mean preoperative spherical equivalent for the 34 consecutively treated eyes was -6.67+/-2.69 D. The LASIK operations were performed by a Hansatome microkeratome (Bausch and Lomb) and a scanning spot excimer laser (Technolas Keracor 217, Bausch and Lomb). For pre- and postoperative analysis the Datagraph med software (Version 2.7) was used. RESULTS: None of the treated eyes lost 2 or more lines of best-corrected visual acuity (BCVA). At the 36-month examination the spherical equivalent had changed to -0.47 D (mean increase of myopia: 0.13 D). No long-term complications were found in the study period. CONCLUSION: LASIK with superior hinge and scanning spot excimer ablation is an effective treatment for the correction of myopia and myopic astigmatism in the refractive range described above.

Gaussian broad-beam excimer laser: clinical and experimental results.

PURPOSE: To evaluate the mid-term (1-3 years) results of the Gaussian broad-beam excimer laser Delivery System (DS) after single treatment for the correction of myopia. To study the corneal surface with scanning electron microscopy (SEM) after excimer laser ablation using a flying spot delivery system (Bausch & Lomb) and a Gaussian Delivery System (GDS) (InPro). METHODS: The 1035 consecutive eyes studied were split in four groups with respect to the treated myopia, expressed in spherical equivalent: low myopia up to -3.00 D (183 eyes), moderate myopia from -3.25 D to -6.00 D (540 eyes), high myopia from -6.25 D to -10.00 D (210 eyes) and very high myopia from -10.25 D to -20.00 D (102 eyes). Four post-mortem eyes of two donors were treated using the flying spot DS on one eye and the GDS on the other eye. RESULTS: We achieved postoperative spheriqual equivalent within +/- 1 D of emmetropia in respectively 99.1%, 98.9%, 83% and 21% of the eyes of group 1, 2, 3 and 4. UCVA was 10/10 or better in respectively 65%, 51% and 19% of group 1, 2 and 3. UCVA was 5/10 or better in respectively 86% and 75% of group 3 and 4. The defocus equivalent refraction was 1.0 or less in respectively 98%, 93%, 62%, and 7% of the four groups. On SEM, the corneal surface presented a smooth and polished profile for the GDS. CONCLUSIONS: The Gaussian Delivery System gives comparable results to the flying spot laser system for surface laser ablation in myopic eyes up to -10 D. Advantages of this system are: smooth ablation surface, short treatment time, low haze rate, high reliability and easy maintenance of the device due to the optical DS. It is an interesting alternative for the more complex mechanical DS.

[A comparison between the eye trackers of laser cornea correction systems made by foreign manufacturers].

Photo refractive keratectomy (PRK) and laser Situ Keratomileusis (LASIK) have been used for over a decade and become popular in China. Principles and characteristics of eye trackers made by several famous foreign manufacturers are introduced in this paper and their developing direction in the future is pointed out too.

High-speed photorefractive keratectomy with femtosecond ultraviolet pulses.

Femtosecond near-infrared lasers are widely used for a number of ophthalmic procedures, with flap cutting in the laser-assisted in situ keratomileusis (LASIK) surgery being the most frequent one. At the same time, lasers of this type, equipped with harmonic generators, have been shown to deliver enough ultraviolet (UV) power for the second stage of the LASIK procedure, the stromal ablation. However, the speed of the ablation reported so far was well below the currently accepted standards. Our purpose was to perform high-speed photorefractive keratectomy (PRK) with femtosecond UV pulses in rabbits and to evaluate its predictability, reproducibility and healing response. The laser source delivered femtosecond 206 nm pulses with a repetition rate of 50 kHz and an average power of 400 mW. Transepithelial PRK was performed using two different ablation protocols, to a total depth of 110 and 150 µm. The surface temperature was monitored during ablation; haze dynamics and histological samples were evaluated to assess outcomes of the PRK procedure. For comparison, analogous excimer ablation was performed. Increase of the ablation speed up to 1.6 s/diopter for a 6 mm optical zone using femtosecond UV pulses did not significantly impact the healing process.

New Scheimpflug camera device in measuring corneal power changes after myopic laser refractive surgery.

PURPOSE: To assess the accuracy of a combined Scheimpflug camera-Placido disk device (Sirius, CSO, Italy) in evaluating corneal power changes after myopic photorefractive keratectomy (PRK). METHODS: Two hundred and thirty-seven eyes of 237 patients that underwent myopic PRK with a refractive error, measured as spherical equivalent, ranging from -10.75 D to -0.5D (mean -4.63 ± 2.21D), were enrolled in this study. Corneal power evaluation using Sirius were performed before, 1, 3 and 6 months after myopic PRK. Mean simulated keratometry (SimK) and mean pupil power (MPP) were measured. Correlations between changes in corneal power, measured with SimK and MPP, and variations in subjective refraction, calculated at corneal plane, were evaluated using Pearson test at every follow up; differences between preoperative and postoperative data were evaluated with the Student paired t-test. RESULTS: A good correlation has been detected between the variations in subjective refraction measured at corneal plane 1, 3 and 6 months after myopic PRK and both SimK (R(2) = 0.8463; R(2) = 0.8643; R(2) = 0.7102, respectively) and MPP (R(2) = 0.6622; R(2) = 0.5561; R(2) = 0.5522, respectively) but corneal power changes are statistically undervalued for both parameters (p < 0.001). CONCLUSIONS: Even if our data should be confirmed in further studies, SimK and MPP provided by this new device do not seem to accurately reflect the changes in corneal power after myopic PRK.

Retrospective Analysis Comparing the Preoperative and Postoperative "Q" Values for 2 Different Lasers in Refractive Surgery.

PURPOSE: To compare the presurgical and postsurgical corneal asphericity, or "Q value," between VISX Wavefront-guided treatment and Allegretto Wave Wavefront-optimized treatment in photorefractive keratectomy for the correction of myopia. METHODS: This is a retrospective database analysis performed at the Joint Warfighter Refractive Surgery Center, Lackland Air Force Base, TX. All data were accessed through the Institutional Review Board-approved Joint Warfighter Refractive Surgery Center database. Fifty-one patient records (102 eyes) were reviewed to determine the change in the Q value after photorefractive keratectomy for the correction of myopia. RESULTS: The average change in the Q value per diopter of treatment sphere over the entire study population was 0.12 (±0.04) for Allegretto and 0.14 (±0.04) for VISX (P = 0.004). There was no statistical difference among the preoperative and postoperative best-corrected visual acuities (BCVAs), low-contrast BCVA (BCVA 5%), or quality of vision complaints between both platforms. CONCLUSIONS: Low to moderate myopic correction with the Allegretto laser was associated with a smaller change in the Q value per diopter of treatment and therefore more closely maintained the original prolate shape of the cornea when compared with VISX. No difference in the postoperative visual outcome between both groups was detected.

Investigation of corneal ablation efficiency using ultraviolet 213-nm solid state laser pulses.

PURPOSE: To determine the threshold and efficiency of corneal ablation for various values of laser fluence at the ultraviolet wave length of 213 nm. METHODS: A commercial Q-switched Nd:YAG laser was used to produce the fifth harmonic wavelength of 213 nm. Ablation trials were carried out on porcine corneas. Slit ablations of dimensions 0.5 x 2.5 mm were performed using seven values of laser fluence to obtain the most efficient fluence for ablation. The morphology of each ablation was obtained using a computer-automated confocal profiling system. These profiles were then analyzed to determine the ablation depth for the range of fluence values used. RESULTS: A fluence in the region of 200 mJ/cm2 was found to be the most efficient for ablation. The efficiency in this region was approximately 0.35 mm3/J, and the ablation rate was found to be 0.6 microm/pulse. The ablation threshold was found to occur at a fluence of 50 mJ/cm2. In the region of highest efficiency, the peak varied slightly in the fluence range between 150 and 250 mJ/cm2. CONCLUSIONS: This study confirms that the corneal ablation properties at 213 nm are comparable with those at the 193-nm excimer laser wavelength. Increased pulse energy was obtained for the fifth harmonic of Nd:YAG lasers at 213 nm through the use of new nonlinear optical crystals to perform the frequency conversion. A solid state laser is feasible to replace the excimer gas laser for performing refractive surgery procedures. For the first time, the increased energy at 213 nm allows large-beam ablations to be performed at this wavelength.

Sclerotic scattering illumination during phototherapeutic keratectomy for better visualization of corneal opacities.

PURPOSE: To report on a simple method to obtain a better view of corneal opacities during excimer laser phototherapeutic keratectomy (PTK). DESIGN: An interventional case report. METHODS: Phototherapeutic keratectomy was performed under sclerotic scattering illumination with a vitrectomy-endoilluminator at the limbus. RESULTS: During conventional PTK with diffuse illumination, the intraoperative observations of corneal opacities are not as good as that with a slit lamp. Conversely, subtle corneal opacities can be easily seen with sclerotic scattering illumination even under a surgical microscope. CONCLUSIONS: The use of sclerotic scattering illumination during PTK is valuable, because it provides a better view of opacified tissues and avoids excessive ablation.

Comparative study of ablation profiles of six different excimer lasers.

PURPOSE: To compare the morphological features of photorefractive ablations produced by six different excimer lasers. METHODS: A spherocylindrical photoablation (-2.00 -2.00 x 90 degrees; 6-mm optical zone) was performed on regular fluence plates with six excimer lasers: Bausch & Lomb Technolas 217C, Schwind Esiris, Kera Technology Isobeam D200, Ladarvision 4000, Zeiss Meditec MEL 70 G-Scan, and Visx Star S3. Morphometric analysis of the fluence plates provided superficial measurements of the ablated areas. RESULTS: Two areas were identified visually: a central area with a complete ablation of the metallic surface layer and a surrounding area with a partial ablation. The dimensions of the ablated areas were highly variable in the lasers tested. The major differences appeared in the total ablated area (ranging from 38.55 mm2 [Schwind] to 81.94 mm2 [Bausch & Lomb] and in the peripheral to total area ratio (ranging from 36.95% [Schwind] to 59.51% [Ladarvision]). CONCLUSION: Large differences appeared in the superficial dimensions and contours of the ablations produced by different excimer lasers for the treatment tested in this study. It remains unknown how these different ablation patterns induce the same optical correction, but we assume that the depth of the ablation compensates for the differences in the surface extension of the ablated areas.