LASIK Flap Creation With the Ziemer Femtosecond Laser in 787 ConsecutiveEyes

Comparison of early changes in tear film protein profiles after small incision lenticule extraction (SMILE) and femtosecond LASIK (FS-LASIK) surgery

BACKGROUND

Small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (LASIK) are widely used surgical methods to correct myopia with comparable efficacy, predictability, and safety. We examined and compared the early changes of tear protein profiles after SMILE and FS-LASIK surgery in order to find possible differences in the initial corneal healing process.

METHODS

SMILE operations for 26 eyes were made with Visumax femtosecond laser. In FS-LASIK surgery for 30 eyes, the flaps were made with Ziemer FEMTO LDV Z6 femtosecond laser and stromal ablation with Wavelight EX500 excimer laser. Tear samples were collected preoperatively, and 1.5 h and 1 month postoperatively using glass microcapillary tubes. Tear protein identification and quantification were performed with sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS).

RESULTS

Immediately (1.5 h) after we found differences in 89 proteins after SMILE and in 123 after FS-LASIK operation compared to preoperative protein levels. Of these differentially expressed proteins, 48 proteins were common for both surgery types. There were, however, quantitative differences between SMILE and FS-LASIK. Upregulated proteins were mostly connected to inflammatory response and migration of the cells connected to immune system. One month after the operation protein expressions levels were returned to baseline levels with both surgical methods.

CONCLUSIONS

Our study showed that immediate changes in protein profiles after SMILE and FS-LASIK surgeries and differences between the methods are connected to inflammatory process, and the protein levels quickly return to the baseline within 1 month. The differences in protein profiles between the methods are probably associated with the different size of the epithelial wound induced.

Characteristics of corneal high-order aberrations in adolescents with mild to moderate myopia

Background

This study investigated the characteristics of corneal higher-order aberrations (HOAs) of the anterior surface, posterior surface, and total cornea in adolescents with mild to moderate myopia.

Methods

A total of 183 patients with myopia (183 eyes) aged 8 to 18 years were enrolled in this study. The axial length (AL) of the eyes was measured by an IOL-Master, and corneal curvatures (K-values) and HOAs were measured by a Pentacam anterior segment diagnostic analyzer.

Results

Results of this study showed that the anterior, posterior and total corneal horizontal coma Z₃¹ were − 0.1249 ± 0.105 μm, 0.0009 ± 0.001 μm, and − 0.1331 ± 0.116 μm, respectively; the anterior, posterior and total corneal vertical coma Z₃^− 1 were − 0.0212 ± 0.164 μm, 0.0003 ± 0.043 μm, and − 0.0216 ± 0.168 μm, respectively; and spherical aberration (SA) Z₄⁰ values were 0.2244 ± 0.091 μm, 0.1437 ± 0.029 um, and 0.1889 ± 0.090 μm, respectively. Total corneal Z₃¹ was statistically correlated with posterior corneal astigmatism (K₂b − K₁b) (p = 0.038). Total corneal Z₃^− 1 was correlated with anterior corneal astigmatism (K₂f − K₁f) (p = 0.027). Anterior, posterior, and total corneal Z₄⁰ were correlated with anterior and posterior corneal curvature (K₁f, K₂f, K₁b, K₂b) (p = 0.001). Posterior corneal Z₄⁰b was also significantly correlated with AL.

Conclusions

In adolescents with mild to moderate myopia, the posterior corneal surface shape may play a compensatory role in the balance of corneal aberrations, and the posterior corneal SA tended to become less negative as the AL increased. The corneal coma may also play a compensatory role in posterior corneal surface astigmatism, which was valuable for the treatment for improving visual quality. This conclusion still needs to be verified.

Comparison of corneal flaps created by Wavelight FS200 and Intralase FS60 femtosecond lasers

AIM

To assess and compare the morphology of corneal flaps created by the Wavelight FS200 and Intralase FS60 femtosecond lasers in laser in situ keratomileusis (LASIK).

METHODS

Four hundred eyes of 200 patients were enrolled in this study and divided into Wavelight FS200 groups (200 eyes) and Intralase FS60 groups (200 eyes). Fourier-domain optical coherence tomography (RTVue OCT) was used to measure the corneal flap thickness of 36 specified measurements on each flap one week after surgery. Results were used to analyze the regularity, uniformity and accuracy of the two types of LASIK flaps.

RESULTS

The mean thickness of corneal flap and central flap was 105.71±4.72 µm and 105.39±4.50 µm in Wavelight FS200 group and 109.78±11.42 µm and 109.15 ±11.59 µm in Intralase FS60 group, respectively. The flaps made with the Wavelight FS200 femtosecond laser were thinner than those created by the Intralase FS60 femtosecond laser (P=0.000). Corneal flaps in the 2 groups were uniform and regular, showing an almost planar configuration. But the Wavelight FS200 group has more predictability and uniformity of flap creation. The mean deviation between achieved and attempted flap thickness was smaller in the Wavelight FS200 group than that in the Intralase FS60 group, which were 5.18±3.71 µm and 8.68±7.42 µm respectively. The deviation of more than 20 µm was 0.2% measurements in Wavelight FS200 group and 8.29% measurements in Intralase FS60 group.

CONCLUSION

The morphologies of flaps created by Wavelight FS200 are more uniform and thinner than those created by Intralase FS60.

Complications of femtosecond-assisted laser in-situ keratomileusis flaps

Femtosecond-assisted laser in-situ keratomileusis flaps have revolutionized refractive surgery since their introduction. Although these lasers are exceedingly safe, complications still do occur. This review focuses specifically on examining the literature and evidence for flap complications during femtosecond-assisted laser in-situ keratomileusis as well as their management.

Laser-assisted in situ keratomileusis flap creation with the three-dimensional, transportable Ziemer FEMTO LDV model Z6 I femtosecond laser

PURPOSE

To present the outcomes of laser-assisted in situ keratomileusis (LASIK) operations performed with the new three-dimensional, transportable FEMTO LDV Z6 I femtosecond laser (Ziemer Ophthalmic Systems, Port, Switzerland) and the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG, Erlangen, Germany) in terms of accuracy, reproducibility and safety of flap creation.

METHODS

This is a retrospective study of 309 consecutive eyes of 160 patients treated with the FEMTO LDV Z6 I for corneal flap creation. The target flap thickness was 90 μm. The size of the suction ring varied from 9.5 to 10.0 mm and target flap diameter from 9.3 to 9.6 mm, respectively. The target hinge length was 4.0 mm.

RESULTS

The FEMTO LDV Z6 I produced the 90-μm targeted flaps very consistently (mean 90.1 ± 2.7 μm, range 78-100). Mean flap diameter with the 9.3-mm target flap diameter was 9.3 ± 0.1 mm (range 9.0-9.6) and with the 9.6-mm target flap diameter 9.6 ± 0.1 mm (range 9.0-9.8). Mean hinge length was 3.9 ± 0.1 mm (range 3.3-4.2). Minor complications were reported in 15 (5%) eyes, but none of them prevented refractive laser treatment. The most common complications were bubbles in the conjunctiva (n = 7, 2%) and an opaque bubble layer inside the flap margin (n = 6, 2%). None of the eyes lost two Snellen lines of corrected distance visual acuity during 1-month follow-up.

CONCLUSIONS

In the hands of an experienced surgeon, the transfer from the Classic FEMTO LDV to Z6 I was a safe and straight forward process yielding accurate and reproducible flaps.

Patient and surgeon experience during laser in situ keratomileusis using 2 femtosecond laser systems

PURPOSE

To describe the subjective experience of patients and surgeons during laser in situ keratomileusis (LASIK) using the Intralase 60 kHz or the Visumax 500 kHz femtosecond laser.

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Prospective randomized clinical study.

METHODS

In myopic patients, LASIK was performed with the corneal flap created using the 60 kHz laser in 1 eye and the 500 kHz laser in the contralateral eye. Postoperatively, patients completed a standardized validated questionnaire about their subjective intraoperative experiences (eg, light perception, pain, fear). Surgeons reported their intraoperative experiences and preferences.

RESULTS

Loss of light perception occurred in 50.0% of 60 kHz laser cases and 0% of 500 kHz laser cases during docking and in 63.0% and 0% of cases, respectively, during laser flap creation (P < .0001). The mean pain score with the 60 kHz laser was significantly higher during docking (P < .0001) but not during laser flap cutting (P = .006). Subconjunctival hemorrhage occurred in 67.4% of eyes with the 60 kHz laser and in 2.2% of eyes with the 500 kHz laser (P < .0001). The 500 kHz laser was preferred by 78.3% of patients, while 21.7% preferred the 60 kHz laser (P < .0001). The surgeons preferred the 60 kHz laser in 50.0% of cases and the 500 kHz laser in 8.7% (P < .0001); 41.3% had no preference.

CONCLUSIONS

Patients preferred surgery with the 500 kHz laser with no loss of light perception, less pain, less fear, and less subconjunctival hemorrhage. Surgeons preferred the 60 kHz laser.

Flap characteristics, predictability, and safety of the Ziemer FEMTO LDV femtosecond laser with the disposable suction ring for LASIK

AIMS

The outcomes of laser-assisted in situ keratomileusis (LASIK) operations performed with the Classic FEMTO LDV femtosecond laser using the plastic single-use suction ring (Ziemer Ophthalmic Systems) and the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG) are presented in terms of accuracy, predictability, and safety of the operation.

METHODS

A FEMTO LDV plastic suction ring was used for flap creation in 342 eyes of 179 patients. The intended flap thickness was 90 μm. The size of the suction ring varied from 9.0 to 10.0 mm. Flap dimensions were measured and correlated to preoperative characteristics.

RESULTS

Mean flap thickness was very constant, 89.6 ± 2.0 μm (range 84-97). In 163 bilateral operations, the second flap was 1.1 μm thinner than the one cut first (P<0.0001). Mean flap diameter was 9.4 ± 0.2 mm (range 8.1-9.9). Mean hinge length was 3.9 ± 0.2 mm (range 3.0-4.2). In hyperopic eyes, flap thickness correlated negatively with keratometric power K1 and flap diameter. In hyperopic eyes, flap diameter correlated positively with spherical equivalent refraction and with keratometric power K1 as well as hinge length both in myopic and hyperopic eyes. Complications were reported in 12 (3.5%) eyes. Complications were very mild and none of them prevented further refractive laser treatment. Two Snellen lines of corrected distance visual acuity were lost in one (0.3%) eye.

CONCLUSION

The FEMTO LDV plastic single-use suction rings yielded accurate and reproducible flaps and were safe for the creation of thin corneal flaps.

Comparison of Ziemer FEMTO LDV "Classic" and "Crystal Line" femtosecond laser flap quality by Fourier-domain optical coherence tomography

AIM

To compare the regularity and accuracy of laser in situ keratomileusis (LASIK) flaps created by the Ziemer FEMTO LDV "Classic" (Ziemer "Classic") and Ziemer FEMTO LDV Crystal Line femtosecond laser (Ziemer Crystal Line).

METHODS

Fourier-domain optical coherence tomography (RTVue OCT) was used to measure the morphology of 200 LASIK flaps of 100 consecutive patients created with the Ziemer Classic (100 flaps) or the Ziemer Crystal Line (100 flaps) at one week postoperatively. Flap thickness was evaluated at 36 specified measurement points on each flap. For all procedures with both lasers, the nominal flap thickness was 110µm.

RESULTS

The mean flap thickness of the Ziemer Crystal Line group (102.49±2.68µm) was thinner than that of the Ziemer Classic group (107.65±5.09µm) (P<0.01). Average thickness of all flaps was uniform within 4µm at all measurement points. The flaps in the Ziemer Crystal Line group were more regular than those in the Ziemer Classic group when measured from the center to the periphery. The maximum deviation from the nominal 110µm of 36 measurements was 8µm in the Ziemer Classic group, while in the Ziemer Crystal Line group it was 9µm. Within the 3 600 measurements on the 100 eyes, differences greater than 20µm were observed 0.14% in the Ziemer Classic group, and 0.04% in the Ziemer Crystal Line group.

CONCLUSION

The flaps created with the Ziemer FEMTO LDV Crystal Line femtosecond laser are more uniform and thinner than those created by the Ziemer FEMTO LDV Classic femtosecond laser.

Femtosecond lasers for LASIK flap creation: a report by the American Academy of Ophthalmology

OBJECTIVE

To review the published literature to assess the safety, efficacy, and predictability of femtosecond lasers for the creation of corneal flaps for LASIK; to assess the reported outcomes of LASIK when femtosecond lasers are used to create corneal flaps; and to compare the differences in outcomes between femtosecond lasers and mechanical microkeratomes.

METHODS

Literature searches of the PubMed and Cochrane Library databases were last conducted on October 12, 2011, without language or date limitations. The searches retrieved a total of 636 references. Of these, panel members selected 58 articles that they considered to be of high or medium clinical relevance, and the panel methodologist rated each article according to the strength of evidence. Four studies were rated as level I evidence, 14 studies were rated as level II evidence, and the remaining studies were rated as level III evidence.

RESULTS

The majority of published studies evaluated a single laser platform. Flap reproducibility varied by device and the generation of the device. Standard deviations in flap thicknesses ranged from 4 to 18.4 μm. Visual acuities and complications reported with LASIK flaps created using femtosecond lasers are within Food and Drug Administration safety and efficacy limits. Of all complications, diffuse lamellar keratitis is the most common after surgery but is generally mild and self-limited. Corneal sensation was reported to normalize by 1 year after surgery. Unique complications of femtosecond lasers included transient light-sensitivity syndrome, rainbow glare, opaque bubble layer, epithelial breakthrough of gas bubbles, and gas bubbles within the anterior chamber.

CONCLUSIONS

Available evidence (levels I and II) indicates that femtosecond lasers are efficacious devices for creating LASIK flaps, with accompanying good visual results. Overall, femtosecond lasers were found to be as good as or better than mechanical microkeratomes for creating LASIK flaps. There are unique complications that can occur with femtosecond lasers, and long-term follow-up is needed to evaluate the technology fully.

Laser in situ keratomileusis enhancements with the Ziemer FEMTO LDV femtosecond laser following previous LASIK treatments

BACKGROUND

The aim of this paper is to present the accuracy, predictability, and safety outcomes of LASIK enhancements performed with the FEMTO LDV femtosecond laser (Ziemer Ophthalmic Systems, Port, Switzerland) and the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG, Erlangen, Germany), following previous LASIK treatments.

METHODS

FEMTO LDV was used for flap creation in 85 previously LASIK-treated eyes of 62 patients. The intended flap thickness was 90 μm in 81 eyes and 140 μm in 4 eyes. The size of the suction ring was 9.0 mm in 72 eyes and 9.5 mm in 13 eyes. Flap dimensions were measured and correlated to preoperative characteristics.

RESULTS

With the intended flap thickness of 90 μm in previously LASIK-treated eyes, the actual flap thickness was 90.2 ± 6.6 μm (range 80-122), and the flap diameter was 9.2 ± 0.2 mm (range 8.7-9.9). The mean hinge length was 4.0 ± 0.2 mm (range 3.0-4.8). Flap thickness correlated positively with patient age and hinge length. Complications were reported in 12 eyes (14.1 %). Most of the complications were very mild, and none of them prevented further refractive laser treatment. One eye lost two Snellen lines of best spectacle-corrected visual acuity.

CONCLUSIONS

Femtosecond LASIK enhancement is warranted only in rare cases. Surgical experience is needed and special caution must be practiced. For cases of a primary free cap, femtosecond LASIK is not recommended.

Corneal flap morphological analysis using anterior segment optical coherence tomography in laser in situ keratomileusis with femtosecond lasers versus mechanical microkeratome

AIM

To assess and compare the flap morphology using anterior segment optical coherence tomography (AS-OCT) in laser in situ keratomileusis (LASIK) with Femto LDV femtosecond lasers versus Hansatome mechanical Microkeratome.

METHODS

AS-OCT (Visante) was used to compare 1 month postoperatively the morphology of the flaps created with Femto LDV femtosecond lasers or Hansatome Microkeratome. The intended flap thickness was 110µm and 160µm respectively. The thickness of twenty-five points across each flap, which were 0mm, 1.5mm, 2.5mm, and 3.5mm to the corneal vertex on the horizontal, vertical, 45° and 135° meridian respectively, was evaluated.

RESULTS

One month postoperative, the central flap thickness in the Femto LDV group was 107.43±4.70µm, while 125.90±17.50µm in the Hansatome group. The difference between the actual and the expected flap thickness was 5.61±3.84µm and 31.52±12.27µm, respectively. The Hansatome group had presented a statistically significant result (P<0.001). Flap morphology showed a more regular planar shape in the Femto LDV group and a meniscus shape in the Hansatome group.

CONCLUSION

AS-OCT is a direct and fast procedure to assess the flap morphology. The morphology by AS-OCT showed that the flaps created with Femto LDV femtosecond laser were more accurate and regular than the flaps created with Hansatome microkeratome.

Cellular effects after laser in situ keratomileusis flap formation with femtosecond lasers: a review

PURPOSE

To provide an overview of the cellular effects of femtosecond laser in laser in situ keratomileusis flap formation.

METHODS

Literature review.

RESULTS

The IntraLase is the only femtosecond laser with sufficient histopathological and confocal studies to allow review of the cellular effects of laser application. Histopathological analyses have demonstrated that the energy per pulse and total energy delivered play important roles in the inflammatory reaction to the surgery. The IntraLase laser triggers cellular necrosis (death accompanied by the release of lysosomal enzymes and other components from membrane-bound intracellular compartments) in the corneal stroma surrounding the lamellar cut rather than apoptosis (gentler form of cell death in which most intracellular components remain confined to membrane-bound apoptotic bodies) that is predominant with the microkeratome. Necrosis is a more inflammatory form of cell death that attracts more inflammatory cells. This is likely why earlier femtosecond lasers, such as the 15-kHz IntraLase laser, which requires higher total energy delivery to cut a flap, are associated with more corneal inflammation and diffuse lamellar keratitis. The design of the 60-kHz IntraLase model allows for much lower energy delivery to cut the flap and, therefore, a substantial reduction in keratocyte necrosis to the point that the overall inflammatory response is not significantly different from the microkeratome. Histopathological analysis performed with the Femtec femtosecond laser noted little change in the corneal stromal structure. Confocal microcopy studies performed with the IntraLase laser showed keratocyte "activation" in the stroma and greater fibrotic scarring at the interface than that induced by a mechanical microkeratome.

CONCLUSIONS

The morphologic alterations in the corneal stroma produced by currently available models of the IntraLase laser are comparable to those produced by mechanical microkeratomes. Advances that have resulted in a reduction in the total amount of energy delivered by the laser when it cuts the flap have resulted in a decrease in the inflammatory response associated with femtosecond flap formation to the point that it is indistinguishable from the microkeratome at the cellular level. Further study of each of the femtosecond laser models, including the 150-kHz IntraLase laser, is needed to fully characterize the corneal response to these lasers.

Repeatability of intraoperative central corneal and residual stromal thickness measurement using a handheld ultrasound pachymeter

PURPOSE

To determine and compare the repeatability of intraoperative central corneal thickness (CCT) and residual stromal bed thickness measurements using a handheld ultrasound (US) pachymeter.

SETTING

London Vision Clinic, London, United Kingdom.

DESIGN

Comparative evaluation of a diagnostic test or technology.

METHODS

This study comprised eyes that had laser in situ keratomileusis retreatment by flap lift in which handheld US pachymetry (Corneo-Gage Plus 50 MHz) had been performed intraoperatively. In each case, 5 consecutive measurements were obtained centrally immediately before and after the flap was lifted. The within-eye repeatability was calculated as the standard deviation of the 5 repeated measurements for the CCT measurements and the central residual stromal thickness (RST) measurements.

RESULTS

The study evaluated 134 eyes (79 patients). The mean CCT was 467 μm ± 40 (SD) (range 393 to 577 μm). The repeatability of CCT measurements was 6.83 μm, the coefficient of repeatability was 13.40 μm, and the coefficient of variation (CoV) was 1.46%. The mean central RST was 335 ± 46 μm (range 259 to 465 μm). The repeatability of central RST measurements was 4.91 μm, the coefficient of repeatability was 9.62 μm, and the CoV was 1.46%.

CONCLUSION

The repeatability of intraoperative handheld US pachymetry was similar between measurements of CCT and measurements of central RST; the CoV was 1.46% in both cases.

Laser in situ keratomileusis flap-thickness predictability with a pendular microkeratome

PURPOSE

To assess flap-thickness predictability with a pendular microkeratome (130 μm head).

SETTING

Eye Institute of Thrace, Democritus University of Thrace, Alexandroupolis, Greece.

DESIGN

Clinical trials.

METHODS

The study comprised 263 eyes (132 patients). Laser in situ keratomileusis was performed using the 130 μm head of the Carriazo pendular microkeratome; right eyes were treated first. Ultrasound pachymetry and topography were used for central corneal thickness (CCT) and keratometry (K) measurements. Evaluation included flap thickness, flap diameter, and flap shape.

RESULTS

The mean flap thickness was 125 μm ± 22 (SD) (range 74 to 187 μm) in right eyes and 112 ± 21 μm (range 61 to 190 μm) in left eyes. Flap thickness was significantly correlated with preoperative CCT (r = 0.271; P<.001) but not with K values or the manifest refraction spherical equivalent (P>.15). Right eyes had thicker flaps than left eyes (P<.001); both were significantly below the 130 μm head thickness (mean flap thickness 119.2 ± 22.8 μm; P<.001). The mean achieved flap diameter was 9.2 mm using the 9.0 ring and 9.8 mm using the 10.0 mm ring. Flap-thickness stabilization and convergence between right eyes and left eyes occurred after 100 consecutive flap cuts.

CONCLUSIONS

Flap-thickness predictability was influenced by preoperative CCT only. All cuts were significantly thinner than the head thickness regardless of the suction ring size. Second surgical eyes had thinner flaps, possibly from blade deterioration from the first cut. Approximately 100 flaps were required as a learning curve.

Case report: the correction of a high magnitude of astigmatism with laser-assisted in situ keratomileusis

BACKGROUND

Laser-assisted in situ keratomileusis (LASIK) has undergone several evolutions since it was first approved by the U.S. Food and Drug Administration. Currently, excimer lasers are approved by the U.S. Food and Drug Administration to treat refractive errors with a standard ablation profile, a wavefront-optimized ablation profile, or a wavefront-guided ablation profile. Wavefront-optimized ablation profiles provide a simple method to precompensate for the expected fourth-order spherical aberration and higher-order astigmatism in the average eye.

CASE REPORT

We report a case of a 39-year-old white man, with a high magnitude of mixed astigmatism in the right and left eyes, who was seeking refractive surgical options because he was unable to tolerate contact lenses. The patient underwent bilateral wavefront-optimized LASIK to correct his high degree of astigmatism. Wavefront-guided ablation, as in this patient, can not always be performed because the parameters are not within the allowable treatment profile. Four months after the primary LASIK treatment, the patient underwent a bilateral wavefront-optimized LASIK enhancement for residual astigmatism.

CONCLUSION

This case focuses on the utilization of a wavefront-optimized LASIK treatment profile to eliminate a high magnitude of astigmatic refractive error without inducing higher-order aberrations. Wavefront-guided treatments are not required in most cases but should be considered if the magnitude of preoperative root-mean-square higher-order aberrations is greater than 0.35 μm. Wavefront-optimized aspheric corneal ablations attempt to avoid reducing the prolate eccentricity of the average cornea, and optimized treatments have shown improved visual outcomes compared with conventional LASIK treatments. A thorough knowledge of refractive surgery is important for any treating eye care practitioner to provide patients with the full range of options to correct all types of refractive errors.

Femtosecond laser in-situ keratomileusis flap configurations

PURPOSE OF REVIEW

The corneal flap laser in-situ keratomileusis (LASIK) is among the most important determinants in the successful outcome of the surgery. Femtosecond lasers have evolved over the last decade to all but replace the mechanical microkeratome as the preferred method to create these flaps. With improvements in femtosecond laser technology, there has been a reduction in the time taken for the cut and the quality of the stromal bed has improved. Improved predictability has led surgeons to explore the possibility of thin flap LASIK.

RECENT FINDINGS

Corneal flaps created with the femtosecond laser have been shown to be more predictable in depth and have a more desirable planar morphology. Corneal flaps created by the femtosecond laser can be customized according to depth, profile, morphology, and side-cut configuration. Changes in the angulation of the side cut, to reduce the incidence of epithelial ingrowth, have not been corroborated by clinical evidence as yet. Thin flap LASIK, also referred to as sub-Bowman's keratomileusis, has the advantage of preserving more stroma and potentially reducing the incidence of corneal ectasia but seems to be associated with an increased incidence of interface haze.

SUMMARY

This review examines the advantages of creating a flap with the femtosecond laser and the various configurations of these flaps. It also explores the advantages of varying the thickness and profile of femtosecond flaps.

Corneal flap assessment with Rondo microkeratome in laser in situ keratomileusis

PURPOSE

To assess the accuracy of flap thickness in laser in situ keratomileusis (LASIK) with Rondo, Wavelight AG microkeratome and to examine factors that can influence flap thickness (FT).

SETTING

The study took place at the Laser & Ophthalmos Eye Clinic, Thessaloniki, Greece.

MATERIAL AND METHODS

Three hundred and sixty eyes from 180 patients underwent LASIK with Rondo microkeratome. Three surgeons (A, B and C) performed all surgeries with no previous experience of Rondo microkeratome. All patients were treated with the 130 μm plate. Central corneal thickness (CCT) and stromal bed thickness were measured by Scheimpflug and ultrasound pachymetry. Right eye (OD) was treated first.

RESULTS

Mean FT for OD: 120 ± 19 μm (range 69-158 μm); for left eye (OS): 106 ± 17 μm (range 70-147 μm). Flaps in OD were significantly thicker than in OS (p < 0.001). FT was significantly correlated to the keratometric reading (K): r = 0.121; p = 0.02. No correlation was found between FT and CCT or between FT and the attempted refractive correction (SE) (p > 0.14). Mean FT was significantly lower than the manufacturer's 130 μm specification (Mean FT = 113 ± 19 μm; p < 0.001). FT between surgeons A, B and C was significantly different (analysis of variance between surgeons; p < 0.001). Scheimpflug and ultrasound CCT measurements were significantly correlated (r = 0.921; p < 0.001) with ultrasound measuring an average 4.5 μm higher than Scheimpflug (CCT (Oculyzer) = 553.96 ± 27 μm; CCT (Ultrasound) = 558.45 ± 28 μm). Mean flap diameter was 9.2 ± 0.2 mm.

CONCLUSIONS

FT with Rondo microkeratome was significantly influenced by the mean preoperative K reading. First treated eye was significantly thicker than the fellow left eye, while both were significantly lower than the recommended 130 μm thickness. Gaining basic experience of Rondo microkeratome required an average of 90 flaps/surgeon.