Femtosecond Laser Flap Research Articles

Atomic force microscopy for the evaluation of corneal surface roughness after femtosecond laser flap creation and excimer ablation.

It is well known that the femtosecond laser lamellar cut induces some degree of surface roughness. Nevertheless, as in femtosecond laser-assisted LASIK (FS-LASIK), an excimer LASIK ablation is performed, and the post-ablation stromal bed should show some degree of smoothening. We decided to compare, using atomic force microscopy (AFM), the roughness of the corneal stromal bed, after a femtosecond lasers device flap was created with or without an excimer myopic ablation. Using 6 freshly enucleated porcine eyes, we created in every eye a flap using a femtosecond laser. Additionally, in 3 eyes, an excimer laser ablation to correct-3 diopters (D) was made. AFM imaging of the remaining corneal stroma was performed. Ten different square areas of 20μm x 20μm at the central area of the stroma of each corneal sample were studied. The roughness parameters used were the root-mean-square deviation from a perfectly flat surface. The RMS deviation was 360 ± 120nm in femtosecond laser only, and 110 ± 20nm in those cases where excimer is also involved (p < 0.0001). Our results show that the roughness of the surface treated with excimer is clearly lower than in the group with no excimer ablation; thus, the application of laser excimer after a flap created by femtosecond laser seems to soften the nano-irregularities created by this technique.

Effect of suction on the posterior segment after LASIK using Femtosecond Laser vs Microkeratome

Background: Creating a successful corneal flap is the first critical step during LASIK surgery. Two techniques are used to produce corneal flaps during LASIK surgery: a microkeratome or a femtosecond laser. Femtosecond laser has a significant impact on refractive surgery by enabling non-mechanical creation of corneal flaps during laser in situ keratomileusis (LASIK). During LASIK flap creation, intraocular pressure (IOP) increases to levels exceeding 65 mm Hg. Femtosecond laser flap creation exerts less extreme IOP fluctuations but requires more procedural time than when a microkeratome is used. This study was conducted upon 60 eyes of 38 patients to evaluate the effect of applied suction during LASIK procedures on the posterior segment of myopic eyes, whether the flap was created by Microkeratome or Femtosecond laser. The study subjects were equally divided into 2 groups: group F (30 eyes of 20 patients) underwent femtosecond laser-assisted LASIK surgery and group M (30 eyes of 18 patients) underwent microkeratome-assisted LASIK surgery using Moria M2 for the treatment of myopia. It was found that the central macular thickness and RNFL thickness were not changed significantly in both groups when measured 1 week after surgery. Regarding the incidence of PVD, there was a higher incidence in group F, it was detected in 8 eyes (26.7%) compared to group M, it was detected in 1 eye (3.3%). Conclusion: Slight localized changes of macular thickness and reduction of the RNFL thickness were caused by LASIK using the two major forms of flap creation, namely a microkeratome or a femtosecond laser. Regarding the incidence of PVD, it was found that femtosecond laser-assisted LASIK using Visumax femtosecond laser had a higher incidence than that after microkeratome-assisted LASIK with the Moria M2. So the surgery of LASIK is safe and efficient, but surgeons should choose effective and safe suction mode, shorten the suction time and exclude potential retinopathy and pre-existing glaucoma before surgery to improve the safety and efficacy of LASIK.

Optical Coherence Tomography-Guided Femtosecond LASIK in the Setting of Corneal Scarring.

PurposeTo report the outcomes of femtosecond-assisted laser in situ keratomileusis (LASIK) in patients with previous corneal scarring using optical coherence tomography (OCT) imaging to determine flap depths.MethodsThe charts of 11 eyes of 9 patients with previous off-visual axis corneal scarring that underwent femtosecond LASIK using OCT guidance for flap depth determination were retrospectively reviewed at a single private practice institution. The baseline characteristics, intraoperative findings and postoperative outcomes were analyzed.ResultsAll 11 eyes underwent femtosecond laser flap creation and LASIK without any significant intraoperative complications. Uncorrected visual acuity improved postoperatively (p<0.0001) and remained stable at 3 months follow-up. None of the subjects lost any lines of best spectacle corrected visual acuity or developed any flap complications during the postoperative period.ConclusionThe OCT-guided femtosecond laser technique described in this report can provide a safe and effective method to deliver LASIK in the setting of previous corneal scarring. Future investigations are required to further validate the findings in this study.

Retrieving an Incomplete Flap With a Femtosecond Laser in the Same Sitting

PURPOSE: To report a case of a 35-year-old woman who had an incomplete flap during laser in situ keratomileusis with the Amadeus II microkeratome (Amadeus; Ziemer Ophthalmic Systems AG) in the right eye. METHODS: There was an incomplete flap in the right eye due to electric failure of the microkeratome at the beginning of flap creation. The incomplete flap was retrieved using the femtosecond laser flap creation technique in the same sitting and excimer laser ablation was performed. RESULTS: Postoperative uncorrected distance visual acuity was 20/20 in both eyes. Postoperative aberration of both eyes was not significant and there was no associated glare or halos. The patient was satisfied with the result. CONCLUSIONS: There are several reports of incomplete flap retrieved using a microkeratome, but this is the first case report in which a femtosecond laser was used to complete the flap in the same sitting. [ Journal of Refractive Surgery Case Reports. 2021;1(1):e6–e9.]

Clinical outcome of femtosecond laser flap formation versus mechanical microkeratome in laser in situ keratomileusis for treatment of myopia

Purpose The aim of this study was to evaluate and to compare the thickness and morphology of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and mechanical microkeratome flaps using anterior segment optical coherence tomography (AS-OCT).Patients and methods This prospective, interventional, comparative clinical study was performed on 60 eyes of 30 patients. Flaps were created in 30 eyes using the WaveLight FS200 FS laser and in 30 eyes using the Moria M2 microkeratome. AS-OCT was used at 1 month postoperatively to evaluate the thickness of each flap at four points, which were 1 and 2 mm from the corneal vertex on the horizontal meridian.Results At the sixth month postoperatively, the uncorrected visual acuity was 0.98±0.10 in the FS-LASIK group and 0.98±0.11 in the microkeratome group, which denotes the efficacy of both procedures. No vision-threatening complications occurred in either group. The average flap thickness at 1 mm was 114.93±3.04 µm in the FS-LASIK group compared with 128.57±3.98 µm in the microkeratome group, with a statistically significant difference (P=0.000). The difference between the achieved and intended flap thickness at 1 mm (accuracy) was 4.93±3.04 µm in the FS-LASIK group compared with 18.57±3.98 µm in the microkeratome group, with a statistically significant difference (P=0.000). At 2 mm, the average flap thickness was 115.22±3.34 µm in the FS-LASIK group compared with 139.00±4.75 µm in the microkeratome group (P=0.000). The flap accuracy at 2 mm was 5.22±3.34 µm and 29.00±4.75 µm in the FS-LASIK group and the microkeratome group, respectively (P=0.000). Flap morphology showed a planar shape (uniform) in the FS-LASIK group and a meniscus shape in the microkeratome group.Conclusion Both FS-LASIK and microkeratome techniques were safe and efficient in correcting myopia and myopic astigmatism, achieving good visual outcome. AS-OCT showed that flaps created by the FS laser were more accurate and uniform than those created by the Moria M2 microkeratome.

Effect of flap homogeneity on higher-order aberrations induction after femtosecond LASIK for myopia.

To assess the relevance of the homogeneity of femtosecond laser flap thickness regarding induction of higher-order aberrations (HOAs). Clínica Rementería & Clínica Novovisión, Madrid, Spain. Prospective observational study. Two hundred thirty-one patients underwent in situ keratomileusis using 5 different femtosecond lasers. The flap thicknesses were measured using anterior segment optical coherence tomography 3 months postoperatively. The same masked observer measured 6 symmetrical points nasally and temporally 1.0 mm, 2.0 mm, and 3.0 mm from the center of the flap in each case. HOAs induced in the cornea were measured using tomography. Positive and significant correlations were found between HOA induction and the flap thickness heterogeneity 3.0 mm from the center of the flap. Pearson correlation coefficients for the induction of HOAs were third-order 0.17112 (P = .0224), fourth-order 0.22474 (P = .0026), fifth-order 0.16449 (P = .0282), coma-like 0.17370 (P = .0204), and total HOAs 0.18182 (P = .0151). The amount of flap-thickness heterogeneity at 3.0 mm from the center of the flap created using femtosecond lasers was correlated with the magnitude of the HOAs induced.

Incidence and predisposing factors of anterior chamber gas bubbles during femtosecond laser flap creation.

To investigate the incidence and the predisposing factors of anterior chamber (AC) gas bubbles during femtosecond laser (FS) flap creation for laser in situ keratomileusis (LASIK). All patients who underwent FS-LASIK surgery at CMU LASIK Center between January 2013 and May 2016 were retrospective reviewed. Preoperative and intraoperative data including keratometry, white-to-white (WTW) corneal diameter, flap parameters (diameter, thickness, hinge position, and tunnel length) and pulse energy were reviewed and compared between incident group and control group. To determine the risk factors, univariate and multivariate conditional logistic regression were used; the eye was unit of analysis. The incidence of AC gas bubbles was 1.6% (22 out of 1378 eyes). The median WTW in the AC bubbles group was 11.5 mm (range 11.1-12.1), which was significantly different from the control group (11.7 mm, range 10.5-12.8, P=0.021). The result of the median WTW minus the flap diameter in the AC bubbles group was 2.5 mm (range 2.1-3.2), which was statistically different to the control group (2.7 mm, range 1.5-3.8, P=0.008). The logistic regression analysis showed that the result of the WTW minus the flap diameter in the AC bubbles group had an adjusted odds ratio of 0.204 (95%CI; 0.056-0.747, P=0.016). Development of AC gas bubbles during FS flap creation is not an uncommon event in Asian eyes which typically have a small WTW. The flap diameter when adjusted relatively to the WTW is a predisposing factor to the possibility of AC gas bubbles occurrence.

Quality of life and satisfaction among physicians after wavefront-optimized vs topography-guided laser vision correction.

To assess satisfaction, quality of life, occupational impact, and clinical outcomes of physicians who have undergone laser vision correction (LVC) using either wavefront-optimized (WFO) or topography-guided (TG) excimer laser ablation profile with femtosecond laser flap creation. Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. Retrospective survey study. A 12-question survey was sent to all physicians who underwent laser in situ keratomileusis or photorefractive keratectomy at the Cole Eye Institute between 2011 and 2018 on the WaveLight Allegretto Wave Eye-Q Laser (Alcon Laboratories, Inc.). Visual outcomes were obtained from patient charts. Two hundred thirty-five physicians (454 eyes) met the study's inclusion criteria, including 181 physicians (353 eyes) who underwent WFO LVC and 54 physicians (101 eyes) who underwent TG LVC. One hundred seventeen physicians (49.8%) responded to the survey and reported an overall satisfaction rate of 98.3% among all physicians receiving LVC with 96.6% reporting they would have the procedure again. Visual outcomes showed a high level of surgical predictability, efficacy, and safety among WFO and TG eyes, with a higher percentage of eyes that received TG ablation achieving 20/10 vision (22% vs 4%, P < .0001) and 20/15 vision (87% vs 69%, P < .01) when compared with WFO eyes. Physicians who had undergone LVC with either WFO or TG excimer laser ablation reported high satisfaction and quality-of-life improvements. Both groups achieved excellent visual outcomes, with a higher percentage of TG eyes achieving 20/10 and 20/15 vision.

A case of epithelial ingrowth with corneal melting after LASIK with femtosecond laser flap creation

A case of epithelial ingrowth with corneal melting after LASIK with femtosecond laser flap creation

Effects of femtosecond and excimer lasers on implanted KAMRA corneal inlay in animal models

To evaluate the effect of femtosecond laser and excimer laser on an intracorneal inlay (KAMRA®) implanted in animal models. Femtosecond laser was used to create corneal intrastromal pockets at 250μm depth in five porcine eyes. Four intact KAMRA inlays, examined by slit-lamp biomicroscopy and light microscopy, were implanted in the pocket of four eyes. A standard LASIK flap was created above each implanted inlay in the four eyes using a femtosecond laser with flap thicknesses of 150μm, 130μm, 110μm and 90μm. In the fifth porcine eye, a LASIK flap was created using femtosecond laser at 110μm depth, and a fifth inlay was then implanted in the 250μm pocket. Excimer laser ablation was performed under the flap targeting a -3.00 refraction. The inlay was then explanted, examined and reimplanted in the same pocket followed by a second similar excimer laser ablation. Significant burn, shrinkage and distortion of microholes were noted in all the first four inlays following the femtosecond laser flap creation at all the various flap thicknesses. The damage was noted to be more prominent as the distance between the flap and inlay decreased. No apparent effect was noted on the fifth inlay following repeated excimer laser ablations. Unlike excimer laser, femtosecond laser appears to be hazardous and damaging to the intracorneal KAMRA inlay when applied above it.

Clinical Outcomes of Laser In Situ Keratomileusis (LASIK) Using Microkeratome and Laser Femtosecond Flap in Myopic Patients

Background: This study aimed to compare postoperative visual acuity and complications between flap LASIK creation using microkeratome and femtosecond laser. Method: This is a retrospective observational study. Data were collected from medical record, patient with microkeratome and femtosecond laser flap creations with best corrected visual acuity 6/6 preoperatively.Uncorrected postoperative visual acuity at 1 day, 1 week and 1 month, also complications were recorded. Result: The microkeratome and femtosecond laser group comprised of 130 and 184 eyes respectively. Visual acuity at 1 day follow up were 99.23% ≥6/12 in microkeratome group and 96.20% ≥6/12 in femtosecond laser group (P=0.19), at 1 week follow up were 99.23% ≥6/12 in microkeratome group and 97.82% ≥6/12 in femtosecond laser group (P=0.36) and 1 month follow up were 99.23% ≥6/12 in microkeratome group and 98.37% ≥6/12 in femtosecond laser group (P=0.60). There were significant differences in intraoperative (P=0.00) and postoperative (P=0.04) complications between two groups. Conclusion: There was no significant difference in visual acuity between LASIK flap creation using microkeratome and femtosecond laser at 1day, 1 week and 1month follow up. There were significant differences in intra and postoperative complications between two groups. Keywords: LASIK, microkeratome, femtosecond laser

Changes in ocular biomechanics after femtosecond laser creation of a laser in situ keratomileusis flap

To evaluate ocular biomechanical parameters with the Corvis ST, a noncontact tonometer combined with an ultra-high-speed Scheimpflug camera, before and after creation of a femtosecond laser-created laser in situ keratomileusis (LASIK) flap. Private practice, Siena, Italy. Prospective consecutive study. Right eyes of patients having LASIK were assessed with the dynamic Scheimpflug camera before and after femtosecond laser (LDV Z4) flap creation but before mechanical flap lifting. Twenty-eight eyes of 28 patients were evaluated. Before flap creation, the mean values on the dynamic Scheimpflug camera were intraocular pressure (IOP), 15.04 mm Hg ± 3.99 (SD); central pachymetry, 550.8 ± 101.0 μm; applanation 1 length, 1.721 ± 0.134 mm; applanation 2 length, 1.674 ± 0.287 mm; applanation 1 velocity, 0.126 ± 0.031 m/s; and deflection amplitude, 1.039 ± 0.141 mm. After flap creation, the mean values were IOP, 16.10 ± 3.11 mm Hg (95% confidence interval [CI], 0.44-1.78; P < .05); central pachymetry, 561.8 ± 35.9 μm (95% CI, -28.9 to 50.9; P = .21); applanation 1 length, 1.789 ± 0.1492 mm (95% CI, 0.003-0.134; P < .05); applanation 2 length, 1.759 ± 0.259 mm (95% CI, -0.005 to 0.173; P = .08); applanation 1 velocity, 0.136 ± 0.022 m/s (95% CI, 0.001-0.017; P < .05); and deflection amplitude, 1.029 ± 0.151 mm (95% CI: -0.043 to 0.025; P = .34). The dynamic Scheimpflug camera showed changes in biomechanical properties after femtosecond creation of a LASIK flap as indicated by an increased applanation 1 length and applanation 1 velocity. No author has a financial or proprietary interest in any material or method mentioned.

Long-Term Outcomes of Post-Penetrating Keratoplasty Astigmatic Keratotomy Performed Using 30 kHz Femtosecond Laser Flap Mode Software vs 150 kHz Femtosecond Laser Enabled Astigmatic Keratotomy Software

Purpose: To assess the long-term outcomes of astigmatic keratotomy (AK) performed with two different techniques in patients with post-penetrating keratoplasty (post-PK) residual astigmatism. Methods: This retrospective comparative case series was performed at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA. Patients who underwent post-PK AK performed using either 30 kHz femtosecond laser flap mode software (IntraLase/AMO, Irvine, CA)-Group 1-or using 150 kHz femtosecond laser enabled AK software (IntraLase/AMO, Irvine, CA)-Group 2-to create two anterior arcuate corneal incisions were included in this study. Preoperative and long-term postoperative follow-up data, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and spherical equivalence (SE) were analyzed. Results: In group 1 (n=5), the difference in pre- and post-operative UDVA (0.97 ± 0.29 LogMAR to 0.68 ± 0.40 LogMAR, p=0.13), CDVA (0.28 ± 0.27 LogMAR to 0.47 ± 0.48 LogMAR, p=1), SE (-2.0 ± 3.0 diopters (D) to -1.8 ± 1.8 D, p=0.88) were not statistically significant, although UDVA and SE showed clinical improvement. In group 2 (n=6), the difference in pre- and post-operative UDVA (1.20 ± 0.14 LogMAR to 0.82 ± 0.62 LogMAR, p=0.19), CDVA (0.58 ± 0.32 LogMAR to 0.34 ± 0.31 LogMAR, p=0.25), SE (-2.3 ± 4.7 D to -2.9 ± 4.4 D, p=0.25) were not statistically significant. There was no statistical difference regarding postoperative UDVA (p=0.85), CDVA (p=0.93), SE (p=0.51) and surgically induced astigmatism (p=0.13) between the 2 groups. Conclusion: AK performed with both techniques is a safe procedure to correct post-PK residual astigmatism. Both techniques yielded comparable results.

One-Year Outcomes of Femtosecond Laser-Assisted LASIK Following Previous Radial Keratotomy

To report the 1-year outcomes of LASIK in patients with previous radial keratotomy using a novel femtosecond laser platform. The charts of 27 eyes of 18 patients who underwent femtosecond laser-assisted LASIK with the WaveLight FS200 laser (Alcon Laboratories, Inc., Fort Worth, TX) for consecutive hyperopia following previous radial keratotomy were retrospectively reviewed at a single private practice location. The preoperative characteristics, intraoperative details, and postoperative results were evaluated. All 27 eyes had successful femtosecond laser flap creation without significant intraoperative or postoperative complications. Uncorrected visual acuity significantly improved postoperatively to 0.13 ± 0.13 logMAR at 12 months of follow-up (P < .0001). Postoperative spherical equivalent averaged 0.11 ± 0.53 diopters. None of the patients lost any lines of corrected distance visual acuity during the postoperative period. The femtosecond laser technique described by this study resulted in a safe and effective way to deliver LASIK following previous radial keratotomy. Future investigations are needed to further validate the outcomes of this study.

Laser in situ keratomileusis flap complications and complication rates using mechanical microkeratomes versus femtosecond laser: Retrospective review

Purpose: To compare the frequency and types of flap complications when a femtosecond laser versus a microkeratome is used in flap creation for laser in situ keratomileusis (LASIK).Methods: Retrospective review of private and published results of intraoperative and postoperative complications seen with mechanical microkeratomes and the femtosecond laser. The data from 13,721 consecutive mechanical microkeratome created flaps and 10,348 consecutive femtosecond laser created flaps for LASIK performed by one surgeon (KS) were analyzed for this study.Results: A lower rate of intraoperative complications (incomplete flap, buttonhole, free cap, thin/irregular flap) was seen in the femtosecond created flaps (0.019%) compared to the microkeratome created flaps in this study (0.095%, p<0.001) and large published studies (0.80%, p<0.001). Less postoperative complications (epithelial ingrowth, keratectasia) were also seen in the femtosecond group (0.03%) compared to the microkeratome group (0.14%, p=0.01). There were several complications seen that were unique to the femtosecond laser, including transient light sensitivity, anterior chamber bubbles and vertical gas breakthrough. Conclusions: Intraoperative and postoperative flap complications were significantly higher with mechanical microkeratomes compared to the femtosecond laser. Femtosecond laser flap creation resulted in some complications that were unique to this modality.Key Words: LASIK, Flap Complications, Microkeratome, Intralase, Femtosecond Laser

Research of bubbles created during femtosecond laser flap creation

The femtosecond laser is gaining po-pularity as a safe and effective alternative to the microkeratome for creating corneal flaps during LASIK. Femtosecond laser has advantage over microkeratome flap for creating corneal flap because it reduces or even avoids related complications of microkeratome flap. But it can create bubbles during femtosecond laser flap creation, and the bubbles can influence the corneal flap creation and the progress of operation. In this paper, influence factors of bubbles created during femtosecond laser flap creation and research progress were summarized and explore how to reduce the incidence of bubbles. Key words: Laser, femtosecond; Laser in situ keratomileusis (LASIK); Bubbles

Anterior chamber gas bubble emergence pattern during femtosecond LASIK-flap creation.

To characterise the emergence pattern of cavitation bubbles into the anterior chamber (AC) following femtosecond laser-assisted in situ keratomileusis (LASIK)-flap creation Retrospective review of patients undergoing femtosecond LASIK surgery at Boston Laser, a private refractive surgery practice in Boston, Massachusetts, between December 2008 and February 2014. Patient charts were reviewed to identify all cases with gas bubble migration into the AC. Surgical videos were examined and the location of bubble entry was recorded separately for right and left eyes. Five thousand one hundred and fifty-eight patients underwent femtosecond LASIK surgery. Air bubble migration into the AC, presumably via the Schlemm's canal and trabecular meshwork, occurred in 1% of cases. Patients with AC bubbles had an average age of 33±8 years with a measured LASIK flap thickness of 96±21 μm. The occurrence of gas bubbles impaired iris registration in 64% of cases. Gas bubbles appeared preferentially in the nasal or inferior quadrants for right (92% of cases) and left (100% of cases) eyes. This bubble emergence pattern is significantly different from that expected with a random distribution (p<0.0001) and did not seem associated with decentration of the femtosecond laser docking system. The migration of gas bubbles into the AC is a rare occurrence during femtosecond laser flap creation. The preferential emergence of gas bubbles into the nasal and inferior quadrants of the AC may indicate a distinctive anatomy of the nasal Schlemm's canal.

Macular and retinal nerve fiber layer thickness changes after small-incision lenticule extraction and femto-LASIK

Introduction Femtosecond laser flap creation exerts less intraocular pressure (IOP) fluctuation but requires more procedural time compared with microkeratome flap creation. This IOP elevation during suction may affect the macular and retinal nerve fiber layer thickness that can be assessed with optical coherence tomography. Purpose The aim of this study was to compare the influence of the transient elevation of IOP during suction on the macular and retinal nerve fiber layer thickness after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in-situ keratomileusis (femto-LASIK). Patients and methods A total of 80 and 75 eyes that received SMILE and femto-LASIK procedures for myopia and myopic astigmatism, respectively, were enrolled in this study. Spectral-domain optical coherence tomography was used to measure macular and peripapillary retinal nerve fiber layer thickness preoperatively, at 1 week, and 1, 3, and 6 months postoperatively. Results The study included 155 eyes. In both the SMILE group and the femto-LASIK group, the mean foveal, parafoveal, and perifoveal retinal thickness did not change significantly from the preoperative to any postoperative timepoint (P > 0.05). The mean foveal retinal thickness was significantly greater in the femto-LASIK group than in the SMILE group (P 0.05). The differences in the retinal nerve fiber layer between the SMILE group and the femto-LASIK group were not statistically significant at any follow-up visit (P > 0.05). Conclusion Both SMILE and femto-LASIK procedures had no significant effects on the macular and retinal nerve fiber layer thickness postoperatively.

Femtosecond Laser Flap Creation for Laser In Situ Keratomileusis in the Setting of Previous Radial Keratotomy.

The aim of the study was to report the outcomes of laser in situ keratomileusis (LASIK) in subjects with previous radial keratotomy (RK) using a novel femtosecond laser setting on a proprietary femtosecond laser platform. This was a retrospective, consecutive chart review of patients at a single private practice institution. The medical records of 16 eyes of 8 subjects who underwent femtosecond-assisted LASIK for consecutive hyperopia after RK were retrospectively reviewed. The preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed. All 16 eyes had successful femtosecond laser flap creation without significant intraoperative or postoperative complications. Uncorrected visual acuity significantly improved postoperatively (P = 0.0142) and remained stable through the final follow-up interval at 9 to 12 months postoperatively. None of the subjects lost any lines of best spectacle-corrected visual acuity in the postoperative period. The novel femtosecond laser technique described in this study can provide a safe and effective method for patients undergoing LASIK after previous RK. Future investigations are required to further validate the findings reported in this study.

Incidence and Outcomes of Anterior Chamber Gas Bubble during Femtosecond Flap Creation for Laser-Assisted In Situ Keratomileusis.

Purpose. To report the incidence and outcomes of anterior chamber gas bubble formation during femtosecond laser flap creation for laser-assisted in situ keratomileusis (LASIK). Methods. The charts of 2,886 consecutive eyes that underwent femtosecond LASIK from May 2011 through August 2014 were retrospectively reviewed. The incidence, preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed in subjects developing anterior chamber gas bubble formation during the procedure. Results. A total of 4 cases (0.14%) developed anterior chamber gas bubble formation during femtosecond laser flap creation. In all four cases, the excimer laser was unable to successfully track the pupil immediately following the anterior chamber bubble formation, temporarily postponing the completion of the procedure. There was an ethnicity predilection of anterior chamber gas formation toward Asians (p = 0.0055). An uncorrected visual acuity of 20/20 was ultimately achieved in all four cases without further complications. Conclusions. Anterior chamber gas bubble formation during femtosecond laser flap creation for LASIK is an uncommon event that typically results in a delay in treatment completion; nevertheless, it does influence final positive visual outcome.