Femtosecond Laser Flap Creation Research Articles

Clinical analysis of real-time iris recognition guided LASIK with femtosecond laser flap creation for myopic astigmatism

To assess the safety, efficacy, stability and changes in cylindrical degree and axis after real-time iris recognition guided LASIK with femtosecond laser flap creation for the correction of myopic astigmatism. Retrospective case series. This observational case study comprised 136 patients (249 eyes) with myopic astigmatism in a 6-month trial. Patients were divided into 3 groups according to the pre-operative cylindrical degree: Group 1, -0.75 to -1.25 D, 106 eyes;Group 2, -1.50 to -2.25 D, 89 eyes and Group 3, -2.50 to -5.00 D, 54 eyes. They were also grouped by pre-operative astigmatism axis:Group A, with the rule astigmatism (WTRA), 156 eyes; Group B, against the rule astigmatism (ATRA), 64 eyes;Group C, oblique axis astigmatism, 29 eyes. After femtosecond laser flap created, real-time iris recognized excimer ablation was performed. The naked visual acuity, the best-corrected visual acuity, the degree and axis of astigmatism were analyzed and compared at 1, 3 and 6 months postoperatively. Static iris recognition detected that eye cyclotorsional misalignment was 2.37° ± 2.16°, dynamic iris recognition detected that the intraoperative cyclotorsional misalignment range was 0-4.3°. Six months after operation, the naked visual acuity was 0.5 or better in 100% cases. No eye lost ≥ 1 line of best spectacle-corrected visual acuity (BSCVA). Six months after operation, the naked vision of 227 eyes surpassed the BSCVA, and 87 eyes gained 1 line of BSCVA. The degree of astigmatism decreased from (-1.72 ± 0.77) D (pre-operation) to (-0.29 ± 0.25) D (post-operation). Six months after operation, WTRA from 157 eyes (pre-operation) decreased to 43 eyes (post-operation), ATRA from 63 eyes (pre-operation) decreased to 28 eyes (post-operation), oblique astigmatism increased from 29 eyes to 34 eyes and 144 eyes became non-astigmatism. The real-time iris recognition guided LASIK with femtosecond laser flap creation can compensate deviation from eye cyclotorsion, decrease iatrogenic astigmatism, and provides more precise treatment for the degree and axis of astigmatism .It is an effective and safe procedure for the treatment of myopic astigmatism.

Thin-flap laser in situ keratomileusis with femtosecond-laser technology

To evaluate the results of thin-flap laser in situ keratomileusis (LASIK) using a femtosecond-laser platform for flap creation. Institute of Vision and Optics, Faculty of Medicine, University of Crete, Heraklion, Greece. Prospective interventional case series. Patients had LASIK with the FS200 femtosecond laser for flap creation and the Allegretto Wave Eye-Q excimer laser. Flap thickness was set at 105 μm. All eyes were examined 1 month postoperatively. Flap thickness was assessed with anterior segment optical coherence tomography using the manual flap tool at 5 locations on a horizontal B scan. This study comprised 50 eyes of 25 patients (mean age 28 years ±5.72 [SD]); 42 eyes completed 6 months of follow-up. Preoperatively, the mean sphere was -3.61 ± 1.87 diopters (D) and the mean cylinder, -1.08 ± 1.23 D. Six months postoperatively, no eye lost lines of corrected distance visual acuity (CDVA), 29% gained 1 line, and 7% gained 2 lines. The mean spherical equivalent was -0.03 ± 0.42 D (range -0.88 to +0.88 D); 86% had an uncorrected distance visual acuity of 20/20 or better. The mean central flap thickness at 1 month was 102.98 ± 6.33 μm (range 91 to 114 μm). There were no intraoperative or postoperative complications. No significant complications occurred after treatment with this new femtosecond-laser platform in thin-flap LASIK. Clinical (visual and refractive) results were satisfactory in terms of safety, predictability, and stability.

Anterior chamber gas bubbles during femtosecond laser flap creation in LASIK: Video evidence of entry via trabecular meshwork

Femtosecond laser photodisruption of corneal stroma during laser in situ keratomileusis flap creation is accompanied by the formation of cavitation gas bubbles consisting of carbon dioxide and water vapor. Entry of these bubbles into the anterior chamber is an infrequent complication. We present video evidence that these bubbles enter via the trabecular meshwork. Neither author has a financial or proprietary interest in any material or method mentioned.

Corneal endothelial cell changes 5 years after laser in situ keratomileusis: Femtosecond laser versus mechanical microkeratome

To compare corneal endothelial cell density (ECD) and morphology between flap creation with a femtosecond laser and flap creation with a mechanical microkeratome 5 years after laser in situ keratomileusis (LASIK). Mayo Clinic, Rochester, Minnesota, USA. Prospective randomized masked paired-eye study. In this study of LASIK for myopia or myopic astigmatism, fellow eyes were randomized by ocular dominance to flap creation by a femtosecond laser or by a mechanical microkeratome. Central endothelial images were analyzed before and 3 years and 5 years after LASIK; endothelial cell variables were compared between treatments at each examination. Relationships between endothelial cell loss and contact lens wear, residual bed thickness, and preoperative refractive error were evaluated. There were no differences in the ECD, percentage of hexagonal cells, or coefficient of variation of cell area between treatments at any examination (all P = .99); the smallest detectable differences were 120 cells/mm(2), 5%, and 2%, respectively. The mean annual rate of corneal endothelial cell loss was -0.1% ± 1.2% (SD) and -0.1% ± 1.0% for the femtosecond laser and the mechanical microkeratome, respectively. Endothelial cell loss was not associated with contact lens wear, residual bed thickness, or preoperative refractive error. The energy delivered to the cornea during femtosecond laser flap creation did not affect the corneal endothelium 5 years after LASIK when compared with flap creation with a mechanical microkeratome. Corneas that have had either method of flap creation could be accepted as donor tissue for endothelial keratoplasty from the standpoint of endothelial health. No author has a financial or proprietary interest in any material or method mentioned.

Transitioning from mechanical microkeratome to femtosecond laser flap creation: Visual outcomes of an experienced and a novice LASIK surgeon

To compare the visual outcomes of the first 200 myopic laser in situ keratomileusis (LASIK) cases between a mechanical microkeratome expert surgeon and a fellowship-trained surgeon transitioning to the femtosecond laser. London Vision Clinic, London, United Kingdom. Comparative case series. This analysis comprised the first 200 consecutive myopic LASIK procedures using the Visumax femtosecond laser and the MEL 80 excimer laser for an expert surgeon (11,637 previous microkeratome LASIK procedures) and a fellowship-trained surgeon (observed 1057, performed 155 supervised LASIK procedures) following a standardized surgical technique. Inclusion criteria were preoperative spherical equivalent (SE) refraction up to -8.50 diopters (D), cylinder up to 3.50 D, and corrected distance visual acuity (CDVA) of 20/20 or better. Follow-up was 1 year. There were no statistically significant differences in outcome measures between surgeons. Preoperatively, the mean SE was -4.00 D ± 1.83 (SD) and -3.97 ± 1.98 D and the mean cylinder was 0.81 ± 0.67 D and 0.79 ± 0.66 D for the expert surgeon and fellowship-trained surgeon, respectively. Postoperatively, the SE was ±0.50 D in 79% and 74%, uncorrected distance visual acuity was 20/20 or better in 96% and 96%, and 1 line of CDVA was lost in 3.5% and 1.5% for the expert surgeon and fellowship-trained surgeon, respectively. Contrast sensitivity increased or was unchanged. A fellowship-training program based on a standardized surgical protocol resulted in statistically comparable outcomes between an expert surgeon and a fellowship-trained surgeon when newly transitioned to a femtosecond laser device.

Optimal parameters to improve the interface quality of the flap bed in femtosecond laser-assisted laser in situ keratomileusis

To analyze the interface quality of the anterior stroma after femtosecond laser flap creation using atomic force microscopy. IRCCS Fondazione G.B. Bietti, Rome, Italy. Experimental study. A 110 μm depth flap was created in 20 human corneal tissues using a femtosecond laser platform (Intralase iFS). Tissues were divided into 4 groups of various cutting parameters: pulse energy and spot separation of 0.75 μJ and 6 μm (Group 1), 0.65 μJ and 5 μm (Group 2), 0.55 μJ and 4 μm (Group 3), and 0.45 μJ and 4 μm (Group 4). Four additional tissue sections were cut using a motorized microkeratome (Hansatome). Atomic force microscopy (Autoprobe CP) analysis was performed on the stromal bed of each sample. The corneal tissues treated with higher pulse energies and wider spot separations (Groups 1 and 2) showed a rougher stromal bed interface (root mean square [RMS] rough = 0.23 μm ± 0.008 (SD) and 0.24 ± 0.009 μm, respectively) than tissues in Groups 3and 4 (RMS rough = 0.18 ± 0.006 μm and 0.18 ± 0.008 μm, respectively; P<.001, 1-way analysis of variance). The stromal surface quality of tissues treated with pulse energies of 0.55 μJ or lower and 4 μm spot separation compared favorably with that of tissues cut by the microkeratome (RMS rough = 0.17 ± 0.006 μm; P>.05, Tukey). The femtosecond stromal interface quality was improved with pulse energy lower and spot separations narrower than those currently used in the clinical setting. The flap interface smoothness created by the femtosecond laser was comparable to that created by the microkeratome. No author has a financial or proprietary interest in any material or method mentioned.

Relationship Between Patient Age and Refractive Index of the Corneal Stroma During Refractive Surgery Assisted by Femtosecond Laser Flap Creation

To measure the refractive index (RI) of the human corneal stroma in vivo using an objective Abbé refractometer (VCH-1) and to determine if RI of the stroma is related to age. VCH-1 was used to measure RI at the central anterior stroma immediately after lifting the flap in neophyte patients preselected for laser in situ keratomileusis. Surgical procedures continued as preplanned after measuring the RI, and in binocular cases, measurements were taken from the right eye only. Corneal flaps were created using a femtosecond laser system. Mean RI (±SD, range) and age (±SD, range) values were 1.373 (±0.006, 1.358-1.385) and 36.55 (±12.26, 18-74). A significant linear correlation was found between age and RI. Least squares regression lines equating RI with age (x, years) were of the form: RI = 1.36911 + 0.000096x (r = +0.195; n = 115; P = 0.037). Mean RI (± SD) in the 2 age groups separated by the median age (≤34 and ≥35) were 1.371 (±0.007; n = 57) and 1.374 (±0.005; n = 58). The difference was statistically significant (P = 0.018). RI of the anterior stroma in vivo tends to be increased in older patients when the corneal flap is created using a femtosecond laser device.

LASIK operations with the Ziemer FEMTO LDV femtosecond laser flap creation after previous photorefractive keratometry or laser-assisted sub-epithelial keratomileusis

Editor, Enhancement procedures may be needed after previous refractive surgery in the cases of under or over correction and regression. Enhancement procedures can be performed by photorefractive keratometry (PRK) or laser-assisted in situ keratomileusis (LASIK). LASIK is an attractive option for retreatment after previous surface ablations such as PRK or laser-assisted sub-epithelial keratomileusis (LASEK). Main reasons for choosing LASIK are a quick recovery and the absence of haze. Previously, in LASIK, corneal flaps have been recreated using various microkeratomes (Comaish et al. 2002; Pitkänen et al. 2010). In recent years, femtosecond lasers have emerged as alternatives to the traditional microkeratome-based LASIK. Femtosecond laser technology has some advantages, such as less variation in flap thickness and a more uniform flap thickness throughout the whole flap, compared to microkeratome-based flaps. However, reports published on reoperations performed with the femtosecond laser technology after previous refractive surgery are still scarce and limited to Intralase (Tran et al. 2008). This study presents the outcomes of the first 89 consecutive reoperated eyes of 71 patients, previously treated with PRK (87 eyes) or LASEK (two eyes), which now underwent LASIK flap creation with the FEMTO LDV (Ziemer Ophthalmic Systems, Port, Switzerland) femtosecond laser and excimer laser treatment with the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG, Erlangen, Germany). The patients were operated in the two Finnish Mehiläinen Hospitals, in Tampere and in Helsinki. In all the eyes operated, a superior hinge was used and the intended flap thickness was 90 μm. The diameter of the suction ring was chosen according to the preoperative keratometric K1 value measured before the primary operation. The study included 64 myopic eyes (residual spherical equivalent of refraction, SE, range −6.63 D to −0.25 D, mean SE −1.45 ± 1.01 D) and 25 hyperopic eyes (range SE +0.00 D to +2.88 D, mean SE +1.31 ± 0.91 D). Flap dimensions and the best-corrected visual acuities were measured and intra- and postoperative complications recorded. Mean flap thickness was 90.5 ± 5.4 μm (range, 74–104; Fig. 1) and mean flap diameter was 9.1 ± 0.2 mm (range, 8.8–9.7). Flap thickness was positively correlated with corneal thickness both in myopic (r = 0.33, P < 0.01) and in hyperopic previously surface-ablated eyes (r = 0.51, P < 0.01). The distribution of flap thickness in 89 previously surface-ablated eyes now reoperated with the FEMTO LDV using the intended flap thickness of 90 μm. Complications occurred in six eyes (5.9%). They all were observed in the previously PRK-treated eyes. Most of the complications were very mild, and none of them prevented further treatment with excimer laser. There were no changes in the Snellen lines of BSCVA in 73 eyes (94.8%), and one line was gained in four eyes (5.2%). The mean flap thickness in the previously surface-ablated eyes was equivalent to the one we obtained in our previous study evaluating 787 primary operations with the FEMTO LDV (Pietilä et al. 2010). In this study, flap thickness was affected by corneal thickness just as in our previous study (Pietilä et al. 2010). Although the reason for this positive correlation is unknown, it is, if anything, a clinically advantageous phenomenon. Corneal changes in the previously PRK- or LASEK-treated eyes are mainly ultrastructural (changes in keratocytes in anterior stroma, absence of Bowman’s membrane, subclinical haze in wound healing process). LASIK revision in these eyes poses potentially more risks, and the previously operated corneal tissue is likely to behave in a different way than in the primary LASIK procedure. It is, however, evident that LASIK revisions with the femtosecond technology can be safely performed in most of these cases. Although in general retreatment of previously operated eyes offers greater risks in refractive surgery, the FEMTO LDV femtosecond laser can be successfully used for corneal flap creation in previously surface-ablated eyes.

Femtosecond Laser–assisted LASIK Improves Quality of Life

To investigate the quality of life (QOL) outcomes of femtosecond laser-assisted LASIK using the Quality of Life Impact of Refractive Correction (QIRC) questionnaire. Translation of the QIRC questionnaire from English to Greek followed standard international protocols. The questionnaire was completed by 190 individuals, aged 18 to 39 years with myopia (range: -0.75 to -8.50 diopters) and corrected distance visual acuity (CDVA) of logMAR 0.2 or better (Snellen equivalent 20/32) in the worse eye. Half of this sample underwent LASIK with femtosecond laser flap creation and ablation with the Visx Star S4 IR excimer laser (Abbott Medical Optics). The questionnaire was scored with Rasch analysis. Validity was tested by internal consistency reliability (Cronbach's α) and repeatability by intraclass correlation coefficient (ICC) and Bland-Altman limits of agreement, convergent validity was examined with inter-item correlations, and construct validity was evaluated by known groups comparison analysis. The total QIRC score improved with femtosecond laser-assisted LASIK from mean 38.9±5.7 preoperatively to 53.7±5.1 postoperatively (P<.001). Among the pre-treatment and control groups, QIRC score was greater for those wearing contact lenses than those wearing spectacles (P<.01). The Greek version of the QIRC had good internal consistency reliability. Inter-item correlations were all significant (P<.001), ranging from 0.32 to 0.79. Repeatability was high (Bland-Altman limits of agreement were -6.72 to +5.41 and ICC for the total score was 0.98). Femtosecond laser-assisted LASIK leads to marked improvements in refractive error-related quality of life. This study also provides evidence for the reliability and validity of the Greek version of the QIRC questionnaire.

Diffuse lamellar keratitis after laser in situ keratomileusis with femtosecond laser flap creation

To identify possible associations with the development of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with femtosecond laser flap creation. University-based academic practice, Ann Arbor, Michigan, USA. Case-control study. Myopic LASIK was performed between October 2006 and December 2010 using an Intralase 60 kHz femtosecond laser for flap creation. Preoperative clinical characteristics, treatment parameters, and intraoperative and postoperative complications were recorded. Statistical comparisons were made using t, chi-square, and Fisher exact tests and repeated-measures logistic regression to adjust for inter-eye dependency. The study enrolled 801 eyes (419 patients). Ninety-nine eyes (12.4%) of 70 patients developed DLK; most cases comprised mild flap interface inflammation and were treated with a routine postoperative antiinflammatory regimen. Twenty-two eyes (2.7%) required more than 1 week of antiinflammatory treatment. There was a statistically significant increase in the incidence of DLK with larger flap diameter (P=.0171), higher side-cut energy (P=.0037), and higher raster energy (P=.0033). Patients with DLK were less likely to achieve corrected distance visual acuity of 20/20 or better 1 day postoperatively (P=.0453). The difference in acuity was no longer present at 1 week. There were no significant associations between the incidence of DLK and preoperative refractive error, flap thickness, ablation depth, or other treatment parameters. Diffuse lamellar keratitis after LASIK with femtosecond laser flap creation tended to be mild with little effect on visual acuity. Higher energy level for flap creation and larger flap diameter were associated with an increased risk for DLK.

Comparaison entre le Lasik au laser femtoseconde et le Lasik au microkératome mécanique : prédictibilité des découpes, biomécanique cornéenne et aberrations optiques

To compare the predictability of flap thickness, high-order optic aberrations (HOAs), and biomechanical properties of cornea between patients treated by Lasik with mechanical microkeratome versus patients treated by FemtoLasik. Department of ophthalmology, Pellegrin University Hospital, Bordeaux, France. We conducted a retrospective study on 53 myopic patients who underwent Lasik with either mechanical microkeratome (MK group) or femtosecond laser (FS group). Refraction, central corneal thickness, high-order optic aberrations (HOAs), corneal hysteresis (CH), and corneal resistance factor (CRF), were analysed pre- and postoperatively in both groups. The central corneal thickness was measured with OCT-Visante(®) (Carl-Zeiss, Meditec), biomechanical parameters with ORA(®) (Reichert), and optical aberrations with the Wave Scan(®) (AMO) aberrometer. We included 44 eyes of 22 patients in the MK group and 62 eyes of 31 patients in the FS group. Preoperatively, the mean best-corrected visual acuity was 0.95 in both groups. In the MK group, the flap was significantly thicker than expected (162/130 μm), but in the FS group, there was no significant difference (117/120 μm). The biomechanical properties of the cornea were lower in both groups independently of the flap cutting technique. The HOAs increased after Lasik and were not influenced by the flap cutting technique. Neither mechanical microkeratome, nor femtosecond laser for flap creation, increases HOAs and the biomechanical changes of the cornea, according to ORA(®), significantly after Lasik.

Incidence of diffuse lamellar keratitis after LASIK with 15KHz, 30KHz, and 60KHz femtosecond laser flap creation

Incidence of diffuse lamellar keratitis after LASIK with 15KHz, 30KHz, and 60KHz femtosecond laser flap creation

Incidence of diffuse lamellar keratitis after LASIK with 15 KHz, 30 KHz, and 60 KHz femtosecond laser flap creation

To compare the incidence of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with flap creation using the 15 kHz (FS15), 30 kHz (FS30), or 60 kHz (FS60) femtosecond laser. University-based academic practice, Ann Arbor, Michigan, USA. Retrospective comparative case series. Consecutive myopic LASIK cases performed between January 1, 2005, and June 1, 2007, using the IntraLase FS15, FS30, or FS60 femtosecond laser for flap creation were reviewed. Preoperative clinical characteristics, treatment parameters, and intraoperative and postoperative complications were recorded. Statistical comparisons were made using repeated measures analysis, analysis of variance, chi-square, and Fisher exact tests. Five hundred twenty eyes of 274 patients were included in the study. One hundred seventy-six eyes (93 patients) were treated with the FS15 laser, 180 eyes (93 patients) with the FS30 laser, and 164 eyes (89 patients) with the FS60 laser. Seventeen eyes (10%) in the FS15 laser group, 24 eyes (13%) in the FS30 laser group, and 23 eyes (14%) in the FS60 laser group developed DLK. There was no statistically significant difference in the incidence of DLK between the 3 groups (P = .68). There was no significant difference in the incidence of DLK between the FS15, FS30, and FS60 groups.

Long-term comparison of corneal aberration changes after laser in situ keratomileusis: Mechanical microkeratome versus femtosecond laser flap creation

To compute and compare visual acuity, refractive outcomes, and anterior corneal aberration changes after myopic laser in situ keratomileusis (LASIK) with flap creation by a mechanical microkeratome and by a femtosecond laser. Private practice refractive surgery center, Valencia, Spain. Comparative case series. Patients were assigned to have LASIK flap creation with a mechanical microkeratome (Carriazo-Barraquer) or a femtosecond laser (IntraLase). The Visx S2 excimer laser was used for myopic ablation in all cases. Main outcome measures included uncorrected and corrected distance visual acuities and the defocus equivalent. Higher-order aberrations (HOAs) were computed from the anterior corneal surface measured with topography for 4.0 mm and 6.0 mm pupil diameters before and 48 months after surgery. The study evaluated 50 patients (98 eyes). The root mean square of HOAs increased postoperatively by a factor of approximately 1.9 in both groups and with both pupil diameters. There were no statistically significant differences between the 2 groups in the increase in anterior corneal aberrations, mean postoperative visual acuity, or residual refraction. All visual and optical performance metrics remained stable throughout the 4-year follow-up. There were no complications with flap creation and no postoperative complications. The increase in anterior corneal aberrations after myopic LASIK was similar after mechanical microkeratome and femtosecond laser flap creation. Visual acuity, refraction, and the optical quality of the cornea after LASIK remained stable through 4 years postoperatively in both groups.

In Vivo Real-Time Intraocular Pressure Variations during LASIK Flap Creation

To monitor and compare in vivo real-time intraocular pressure (IOP) in rabbit eyes undergoing LASIK flap creation using microkeratome and femtosecond laser. Thirteen rabbit eyes in each group underwent LASIK flap creation using a microkeratome and a femtosecond laser. In vivo real-time IOP profile was measured using a 30-gauge needle with an IOP catheter sensor inserted into the anterior chamber from the limbus during surgery. In vivo real-time IOP monitoring was achieved in all cases, showing IOP variations during different phases of LASIK flap creation from docking of the instrument, start of surgery to the end of procedure, and monitoring the post-LASIK stabilization. IOP fluctuations were significantly lower in corneal flaps made with the femtosecond laser than with the microkeratome during globe suction (81.78+/-10.55 vs. 122.51+/-16.95 mm Hg), cutting (62.25+/-3.28 vs. 141.02+/-20.46 mm Hg), and suction (41.40+/-2.99 vs. 89.30+/-12.15). In contrast, femtosecond laser requires double the time (19+/-2 vs. 10+/-2 seconds for globe suction and 19+/-2 vs. 9+/-2 seconds for cutting) for completion of the procedure. The authors describe an accurate and reliable setup to measure and record in vivo real-time changes in IOP measurement from the anterior chamber during laser surgery. Femtosecond laser flap creation exerts less extreme IOP fluctuations with improved chamber stability but requires more procedure time than does microkeratome.

Efficacy, safety, and flap dimensions of a new femtosecond laser for laser in situ keratomileusis

To evaluate the clinical results of a preproduction femtosecond laser for flap creation in laser in situ keratomileusis (LASIK). Private practice, Brussels, Belgium. This study comprised myopic eyes with a plano target refraction and a target flap thickness of 110 microm. The LASIK flap was created with a Ziemer LDV femtosecond laser. Prospective evaluation included flap dimensions, intraoperative and postoperative complications, and visual outcomes. Sixty-three patients (111 eyes; mean age 37.2 years) were evaluated. Preoperatively, the mean corrected distance visual acuity (CDVA) was 1.34 (Snellen) and the mean manifest refraction spherical equivalent (MRSE), -4.91 diopters (D) +/- 2.45 (SD). Six months postoperatively, the mean CDVA was 1.33; the mean MRSE, -0.05 +/- 0.3 D; and the mean uncorrected distance visual acuity (UDVA), 1.27. The UDVA was 20/25 or better in 98.2% of eyes and 20/20 or better in 94.6% of eyes. The MRSE was within +/-0.50 D in 95.5% of eyes and within +/-1.00 D in 99.1% of eyes. The cylinder was 0.50 D or less in 99.1% of eyes. The mean flap thickness was 106.6 +/- 12.6 microm. The most frequent complications were epithelial sloughing (10.8%), a decentered cut (4.5%), flap adhesions (5.4%), a slightly irregular flap border (5.4%), and microstriae (5.4%); all were mild. Overall, the flap dimensions and refractive results were predictable and the complication rate was acceptable after LASIK using the new femtosecond laser for flap creation.

Control of Femtosecond Thin-flap LASIK Using OCT in Human Donor Eyes

Thin-flap keratomileusis is a procedure that minimizes LASIK flap thickness to preserve both the corneal epithelium and the maximum residual stroma. This study investigated the usefulness of optical coherence tomography (OCT) as a tool in guiding the femtosecond laser in the creation of a thin flap in human eyes in a non-randomized case series. In a private research laboratory, an in vitro investigation was performed on human autopsy eyes. Five human cadaver eyes, unsuitable for transplantation, underwent flap creation with a femtosecond laser. The laser procedure was controlled in real-time with an OCT system (Thorlabs HL AG) to ensure that the cut was placed just underneath Bowman's layer. The repetition rate of the femtosecond laser was 10 MHz with a single-pulse duration of <400 femtoseconds (pulse energy in the nJ range). As a control, all eyes underwent histological dissection and were examined using light microscopy. Video monitoring of the flap creation supported the feasibility of real-time OCT monitoring of the femtosecond laser flap creation process. A clear distinction of the corneal epithelium was possible in all eyes. Bowman's layer was not identified in all donor eyes at the given resolution of the OCT device used in this study. Light microscopy demonstrated flaps approximately 50-microm thick, confirming that the real-time monitoring assured a positioning of the cutting plane at minimum distance underneath Bowman's layer. This study of five human cadaver eyes shows that real-time OCT monitoring of the creation of thin-flaps in LASIK using a femtosecond laser is possible, thus ensuring that the flap is created at the desired depth.

Intraoperative flap re-cut after vertical gas breakthrough during femtosecond laser keratectomy

We describe the management of intraoperative vertical gas breakthrough (VGB) during femtosecond laser flap creation in 3 patients. All eyes were immediately re-cut using 2 different microkeratomes, and the laser in situ keratomileusis treatments were completed on the same day. There were no postoperative complications. Corneal abrasion might predispose to VGB. Management of VGB is effective using microkeratomes. Caution is advised during placement of the suction ring and in eyes with preexisting corneal abrasion or loose epithelium if femtosecond laser keratectomy is used. The approach in terms of direction of the microkeratome re-cut is fundamental to the safety and successful re-cut with a microkeratome.

Dry eyes and corneal sensation after laser in situ keratomileusis with femtosecond laser flap creation: Effect of hinge position, hinge angle, and flap thickness

To determine whether corneal sensation and dry-eye signs and symptoms after myopic laser in situ keratomileusis (LASIK) surgery with a femtosecond laser are affected by varying hinge position, hinge angle, or flap thickness. University-based academic practice, Ann Arbor, Michigan, USA. This prospective randomized contralateral-eye study evaluated eyes after bilateral myopic LASIK with a femtosecond laser (IntraLase). Superior and temporal hinge positions, 45-degree and 90-degree hinge angles, and 100 microm and 130 microm corneal flap thicknesses were compared. Postoperative follow-up at 1 week and 1, 3, 6, and 12 months included central Cochet-Bonnet esthesiometry, the Ocular Surface Disease Index questionnaire, a Schirmer test with anesthesia, tear breakup time (TBUT), corneal fluorescein staining, and conjunctival lissamine green staining. The study evaluated 190 consecutive eyes (95 patients). Corneal sensation was reduced at all postoperative visits, with improvement over 12 months (P<.001). There was no difference in corneal sensation between the different hinge positions, angles, or flap thicknesses at any time point. The overall ocular surface disease index score was increased at 1 week, 1 month, and 3 months (P<.0001, P<.0001, and P = .046, respectively). The percentage of patients with a TBUT longer than 10 seconds was significantly lower at 1 week and 1 month (P<.0001). Dry-eye syndrome after myopic LASIK with a femtosecond laser was mild and improved after 3 months. Corneal flap hinge position, hinge angle, and thickness had no effect on corneal sensation or dry-eye syndrome.

Complications of LASIK Flaps Made by the IntraLase 15- and 30-kHz Femtosecond Lasers

To describe complications associated with femtosecond laser-assisted flap creation in LASIK surgery. The management and visual outcomes of femtosecond laser complications related to flap creation in LASIK patients are also described. All eyes that underwent LASIK with the IntraLase femtosecond laser from September 2003 to June 2006 at a university-based refractive center were included in this retrospective, noncomparative, interventional case series and IntraLase-related LASIK complications are described. All flaps were made with the 15- and 30-kHz IntraLase femtosecond laser. Included in the study were 4772 eyes, of which 44 (0.92%) eyes had direct or indirect complications due to flap creation. Thirty-two eyes had indirect complications (diffuse lamellar keratitis [DLK] and transient light sensitivity)--20 (0.42%) eyes developed DLK (stage 1 to 2) and 12 (0.25%) eyes had transient light sensitivity syndrome. Twelve (0.25%) eyes had direct femtosecond laser flap-related complications--8 (0.17%) eyes had premature breakthrough of gas through the epithelium within the flap margins, 3 (0.06%) eyes had incomplete flaps due to suction loss, and 1 (0.02%) eye had irregular flap due to previous corneal scar. Less than 1% of eyes had direct or indirect complications due to femtosecond laser flap creation. Laser in situ keratomileusis complications specifically related to the IntraLase femtosecond laser did not cause loss of best spectacle-corrected visual acuity in any eyes.