Corneal Flap Thickness Research Articles

Factors affecting laser in situ keratomileusis flap thickness: Comparison of 2 microkeratome heads

To identify the potential factors affect that affect the thickness of corneal flaps created using 2 different microkeratome heads. Care-Vision Laser Centers, Tel-Aviv, Israel. Retrospective comparative study. The study included eyes in which bilateral laser in situ keratomileusis (LASIK) was performed from January 1, 2005, to December 31, 2012, using an SBK-90 microkeratome head (Group 1) or an M2-90 microkeratome head (Group 2). Inclusion criteria were at least 18 years of age, a stable refraction for 12 months, an intraocular pressure of less than 21 mm Hg, and no history of autoimmune disease, diabetes, ocular surgery, or eye disease. In addition, patients had to cease wearing contact lenses for 2 weeks (rigid lenses) or 4 days (soft lenses) before the preoperative evaluation and before surgery. The disposable blade was used in the right eye first and then reused in the left eye. The study evaluated 6242 eyes of 3121 patients with a mean age of 32.2 years ± 9.8 (SD). Group 1 comprised 2560 eyes (41%), and Group 2 comprised 3682 eyes (59%). The eyes in Group 1 had thinner flaps (P < .001). The right eyes had thicker flaps (P < .001). Flap thickness had a positive correlation with precutting central corneal thickness (CCT) and operating room humidity and a negative correlation with patient age, preoperative sphere and cylinder, and operating room temperature. Statistically significant differences were found in flap thickness between surgeons (P < .001). Larger suction rings created thicker flaps (P < .001). Stepwise regression models accounted for up to 28.1% of the variation in flap thickness. Factors that were significantly correlated with flap thickness included the precutting CCT, whether the right or the left eye, the microkeratome head used, the surgeon performing the procedure, and the preoperative sphere. These findings might help prevent post-LASIK corneal ectasia. No author has a financial or proprietary interest in any material or method mentioned.

Comparison of corneal flap thickness using a FS200 femtosecond laser and a moria SBK microkeratome.

To evaluate differences in flap thickness resulting from use of an Alcon Wavelight FS200 femtosecond laser and a MORIA SBK microkeratome when making a 110-µm-thick corneal flap and to identify the potential factors that affect corneal flap thickness. A prospective case study was performed on 120 eyes of 60 patients who were divided into two groups for LASIK, each group consisting of 60 eyes (30 patients). The corneal flaps were created using an Alcon Wavelight FS200 femtosecond laser or a MORIA SBK microkeratome. The central corneal flap thickness was calculated by subtraction pachymetry. Age, central corneal thickness (CCT), spherical equivalent refraction, mean keratometry, and corneal diameter were recorded preoperatively for analysis. Cutting of all flaps was easily performed without intraoperative complications. In the Alcon Wavelight FS200 femtosecond laser group, the mean right and left corneal flap thicknesses were 114.0±6.6 µm (range: 98-126) and 111.4±7.6 µm (range: 98-122), respectively. The difference (2.6±9.1 µm) in the corneal flap thickness between the right and left eyes was not significant (t=1.59, P=0.12). Stepwise regression analysis indicated that the resulting corneal flap thickness was unrelated to the patient's age, preoperative CCT, spherical equivalent refraction, mean keratometry, or corneal diameter. In the MORIA SBK microkeratome group, the mean right and left corneal flap thicknesses were 110.6±7.4 µm (range: 97-125 µm) and 108.2±6.1 µm (range: 78-123 µm), respectively. The difference in the corneal flap thickness between the right and left eyes (2.4±6.5µm) was not significant (t=2.039, P=0.0506). The corneal flap thickness was positively correlated with the preoperative CCT through stepwise regression analysis (r=0.297, P=0.021). The corneal flap thickness was not related to age, spherical equivalent refraction, mean keratometry, or corneal diameter. The corneal flap thickness was estimated using the following equation: Tflap=67.77+0.076 CCT (F=5.63, P=0.021). Both the Alcon Wavelight FS200 femtosecond laser and the MORIA SBK microkeratome produced 110-µm-thick corneal flaps. The central corneal flap thickness was positively correlated with the preoperative CCT in MORIA SBK microkeratome surgery.

Measurement and comparison of corneal flap thickness between Wavelight FS200 femtosecond laser and Moria 90 microkeratome LASIK by OCT

Background Lasein situ keratomileusi(LASIK) imainstream surgery forefractive correction,and femtosecond laseimuch often used to create thin corneal flap.The measuremenof OPTOVUE RTVue-100 OCto flap and stromal bed thicknesseofferuseful basifoLASIK.Ican be used in measuring the thicknesand shape of the corneal flap.Buthe study on the comparison of flap thicknesbetween WavelighFS200 femtosecond laseand MoriM2 microkeratome 90 μm-knife (Mori90 microkeratome) LASIK by OCilack.Objective The aim of thitrial wato compare the featureof corneal flapcreated by the WavelighFS200 femtosecond laseand Mori90 microkeratome.Methodpiloand prospective study wadesigned.Written informed consenwaobtained from each patienprioto LASIK.Sixty righeyeof 60 patientwith myopiomyopiastigmatism were enrolled in thiclinical trial.The patientwere randomized into the FS200 femtosecond lasegroup and Mori90 microkeratome group with matching demography.RTVue OCwaused to measure flap thicknesusing 10 settingon the 60 eye1 month afteoperation.The featureof the LASIK flapwere analyzed based on the measuring outcomes.ResultThe central flap thickneswa(112±3) μm and the mean flap thickneswa(112 ±3) μm in the FS200 femtosecond lasegroup,which wasignificanlowethan the central flap thicknesa(121±7) μm and the mean flap thicknesa(128±11) μm in the Mori90 microkeratome group respectively (P=0.031,0.030).Corneal flapin the FS200 femtosecond lasegroup showed flashape and thain the Mori90 microkeratome group wameniscushape.The central flap thickneswanoevidently differenfrom thaof peripheral thicknesin the FS200 femtosecond lasegroup (P =0.320).However,in the Mori90 microkeratome group,the central flap thickneswaobviously thinnethan thain the peripheral thicknes(P=0.038).The mean deviation between the actual and predicted flap thicknes(110 μm) wa(3±4)μm in the FS200 femtosecond lasegroup and (17±10) μm in the Mori90 microkeratome group,showing significandifference between them (P =0.009).ConclusionRTVue OCdeterminethathe shape of flapcreated by the FS200 femtosecond laseimore uniform and closeto the expected thicknesof 110 μm than the onecreated by the Mori90 microkeratome.OPTOVUE RTVue-100 OCiuseful tool to evaluate the flap shape and thicknesafteLASIK. Key words: Fourier-domain optical coherence tomography; Femtosecond laser; Cornea; Refractive surgery; Laser in situ keratomileusis; Flap thickness

Accuracy of LASIK Flap Thickness Obtained Using 2 Types of Moria M2 Single-use Head Microkeratome Measured Postoperatively by Optical Coherence Tomography

Background: To investigate the accuracy of corneal flap thickness (FT) and to examine the potential factors that can influence flap thickness obtained using Moria M2 microkeratomes with two kinds of single-use heads. Methods: A retrospective review of the records of 90 patients who had undergone LASIK between Jun 2011 and Jan 2012 at Tri-Service General Hospital was performed. Creation of corneal flap was achieved by automated Moria M2 microkeratome with two different types of single-use head (SU90 and SU130). The right eye was operated before the left eye in each patient, using the same blade. Additionally, the corneal flap thickness was measured in all cases using the Fourier-domain anterior segment optical coherence tomography (AS-OCT) one week later. Results: The mean central thickness of corneal flap was 114.26±4.49μm (Range, 106~127μm) in the SU 90 head and 146.98±3.62μm (Range, 140~157μm) in the SU130 head. The difference between the first and second eye operated was not significant. There were no free flaps, incomplete flaps or flaps with buttonholes in any of our cases. Conclusions: Moria M2 SU 90 and SU 130 produce accurate, reproducible, safe and cost-effective corneal flap. Thin flaps achieved by both single-use heads did not increase the rate of flap-related complications. Furthermore, AS-OCT is a noncontact, rapid, and repeatable tool for measuring corneal flap thickness and making morphological observations.

Reproducibility of the thickness of Lasik corneal flaps made by IntraLase FS 60 laser femtosecond (IntraLase, AMO USA) measured by OCT spectral domain (Heidelberg, Germany)

AbstractPurpose The objective of this study was to appreciate the reproducibility of the thickness of Lasik corneal flaps made by the IntraLase FS60 laser femtosecond (IntraLase, AMO USA).Methods It was a retrospective, randomized, double‐blind study.Twenty eight eyes were included in the study. Every flap was program to measure 120 µm. The flaps were measured by Spectral Domain OCT (Heidelberg), one month after surgery in five points on a horizontal line through the center of the pupil (center, 1mm and 2 mm from the center pupil in nasal and temporal) The scheduled and the obtained thicknesses were compared in each point.Results Double reading by two different doctors showed no significant difference in the thickness flap measurements (p&lt;0.3). Average obtained thickness was 6, 84 µm greater than desired thickness (standard deviation of 7, 27 µm), (p&lt;0, 01). The average thickness flap was significantly greater: nasal 2mm: 128µm +/‐7µm, nasal 1mm: 124.4µm+/‐6µm, central: 127.7µm+/‐8µm, temporal 1mm: 125.9µm +/‐7µm, temporal 2mm: 128.2µm +/‐8 µm (p&lt;0.01).Conclusion We have shown in this study that the cutting of a corneal stromal flap during a LASIK procedure is significant thicker with the IntraLase FS60, but the standard deviation is low.

Uniformity of the thickness of LASIK corneal flaps made by IntraLase FS 60 laser femtosecond (IntraLase, AMO USA) measured by OCT spectral domain (Heidelberg, Germany)

AbstractPurpose The objective of this study was to appreciate the uniformity of the thickness of Lasik corneal flaps made by The IntraLase FS60 laser femtosecond (IntraLase, AMO USA).Methods It was a retrospective, randomized, double‐blind study.Twenty eight eyes were included in the study. Every flap was programmed to measure 120 µm. The flaps were measured by Spectral Domain OCT (Heidelberg), one month after surgery in five points on a horizontal line through the center of the pupil (center, 1mm and 2 mm from the center pupil in nasal and temporal) The scheduled and the obtained thicknesses were compared in each point.Results Double reading by two different doctors showed no significant difference in the thickness flap measurements (p&lt;0.3). There was no significant difference between the thickness in each point of the flap and the center of the flap.Conclusion We have shown in this study that the cutting of a corneal stromal flap with the IntraLase FS 60 laser femtosecond during a LASIK procedure realize uniform flap.

Prospective Contralateral Eye Study to Compare 80- and 120- μ m Flap LASIK Using the VisuMax Femtosecond Laser

To compare visual outcomes and flap stability of LASIK with ultrathin 80- and 120-μm flaps created with a VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for moderate to high myopia and to evaluate the effect of corneal flap thickness on outcomes. In a prospective contralateral eye study, 36 consecutive patients (72 eyes) underwent bilateral LASIK for myopia ranging from -2.00 to -10.00 diopters using the VisuMax femtosecond laser and MEL-80 excimer laser (Carl Zeiss Meditec). One eye of each patient was randomized to have the 80-μm flap and the other to the 120-μm flap created with 200-kHz VisuMax femtosecond laser. Preoperative and postoperative tests included visual acuity, manifest refraction, contrast sensitivity, and flap thickness measured by anterior segment optical coherence tomography. Main outcomes and complications were checked at postoperative 1 week and 1, 3, and 6 months. There were no differences in visual outcome, residual refractive error, or contrast sensitivity between groups during follow-up, except for better uncorrected visual acuity at postoperative 1 day in the 120-μm group. Mean standard deviations of measured flap thickness during follow-up ranged from 3.16 to 3.80 μm in both groups. Opaque bubble layer, a unique complication in femtosecond LASIK, was more frequent in the 80-μm group (7 of 36: 19%) than in the 120-μm flap group (3 of 36: 8%) without a statistically significant difference (P = .301) and was related to thicker central cornea and steeper keratometric value, although it did not influence clinical results. Comparison of the intended versus achieved correction showed no significant differences between groups. LASIK using the VisuMax femtosecond laser supplied good clinical results and flap reproducibility in both the 80- and 120-μm flap groups. Patients with relatively thin cornea may benefit from 80-μm flap LASIK.

Comparisons of morphologic characteristics between thin-flap LASIK and SBK.

To compare the morphologic characteristics between thin-flap laser in situ keratomileusis (LASIK) and Sub-Bowman keratomileusis (SBK), and to evaluate the uniformity of flap and to explore the correlative factors of corneal flap thickness. A prospective, randomized, comparative clinical study was performed in Department of Ophthalmology, West Hospital of China, Chengdu, Sichuan Province, China. Totally 59 patients 114 eyes underwent LASIK or SBK to correct myopia, 29 patients 57 eyes underwent SBK, 30 patients 57 eyes underwent LASIK. Anterior optical coherence tomography(OCT) was used to measure corneal flap thickness in all the patients 1 week after surgeries, 16 positions were set to be measured in each eye. Comparisons of flap thickness in each group and between 2 groups were evaluated. Correlative factors of flap thickness were evaluated. Coefficient of variation (CV, s/×%) in SBK group were lesser than that in LASIK group, t test showed there was significant statistical difference between 2 groups(P=0.000). Comparisons of the difference of 2 paired positions(temporal-nasal; superior-inferior) showed there were no significant differences in each group, but between 2 groups, there were statistical significance of value of difference (D-value) of superior and inferior positions between SBK and LASIK group(P=0.036). Linear regression analysis of correlative factors of flap thickness showed there were no statistic significances related to central corneal thickness(CCT)(P=0.060, t=1.921) and corneal curvature(P=0.083, t=1.766). SBK is better than LASIK in creating much uniform corneal flap. There was no evidence showing correlations between flap thickness and CCT or corneal curvature.

Predictability of the corneal flap creation with the femtosecond laser in LASIK

To observe the predictability of corneal flap creation with the FEMTO LDV femtosecond laser and analyze preliminarily the factors correlating to the thickness and diameter of the flap . It was a study of serial cases. 260 eyes of 130 consecutive patients were treated with the FEMTO LDV. The eyes were assigned to two groups according to intended flap thickness, 110 µm (208 eyes) and 90 µm (52 eyes). Intended flap diameter varied from 8.5 to 9.5 mm. Difference analysis of flap diameter and intended diameter as well as flap thickness and intended thickness were made. The data was analyzed with SPSS to sum up a multiple stepwise regression formula that could express their quantitative relationship. The 90 µm flap group had a average flap thickness of (95.12 ± 7.65) µm, while for the 110 µm group the average flap thickness was (104.81 ± 3.09) µm. The difference between right and left eyes was not statistically significant (t(110 µm) = -1.223, t(90 µm) = -1.343, P > 0.05). Corneal flap thickness was inversely correlated with flap diameter (r(110 µm) = -0.143, r(90 µm) = -0.315, P < 0.05), but was not related to preoperative patient age, corneal thickness, keratometric value K or intraocular pressure (r(110 µm) = -0.160, 0.054, -0.011, -0.363; r(90 µm) = 0.024, 0.074, -0.212, -0.434, all P > 0.05). Corneal flap diameter was positively correlated with preoperative corneal keratometric value K and thickness (P < 0.001, P < 0.05). Multiple stepwise regression analysis showed flap diameter was an influencing factor for flap thickness. Preoperative corneal keratometric value K and thickness were influencing factors for flap diameter. The LASIK flap creation with the FEMTO LDV laser has relatively good predictability. Flap diameter is an influencing factor for flap thickness.

I‐LASIK retreatment of residual refractive errors after microkeratome and femtosecond assisted LASIK

AbstractPurpose To evaluate the efficacy and safety of femtosecond‐assisted sub‐bowman keratomileusis (I‐LASIK) retreatment for residual refractive errors after either I‐LASIK or microkeratome assisted LASIK.Methods We performed i‐lasik retreatment in 14 eyes of 10 patients (mean age 37) for residual myopic and astigmatic refractive errors after previous both i‐lasik and lasik procedures. All patients had stable residual refractive errors for at least 2 years. I‐lasik was performed in all cases with AMO's IntraLase™ FS and STAR S4 IR™ Excimer Laser System, corneal flap thickness was 100µm and hinge position was 90 degrees with reverse 120° side cut. The optical zone of the ablation was from 6.5 to 7 mm, transition zone from 8 to 9 mm.Results Controls were made at 1day, 1 and 3 months. Anterior segment OCT and corneal confocal microscopy were performed in every case. No flap decentration was observed in any case, we had 2 cases of epithelial ingrowth, 4 cases of dry eye, no cases of corneal ectasia and no retinal complications. All spherical equivalent results were within 0.50 diopters.Conclusion In our experience I‐lasik procedure demonstrated itself to be safe and effective also in patients with residual refractive errors from previous i‐lasik and lasik treatments.

Analysis of Microkeratome Thin Flap Architecture Using Fourier-domain Optical Coherence Tomography

To assess the corneal architecture and reproducibility of LASIK flap thickness created by the Amadeus II mechanical microkeratome (Ziemer Ophthalmic Systems AG) using Fourier-domain optical coherence tomography (OCT; Optovue Inc). Anterior segment Fourier-domain OCT was used to analyze the morphology of 58 LASIK flaps from 30 patients created with the Amadeus II microkeratome 140-μm head and ML7090CLB blades (Med-Logics Inc) at 2 weeks postoperatively. Flap thickness was assessed at 10 points across the central 6 mm of the cornea (horizontal and vertical meridians). Postoperative central corneal flap thickness measured by Fourier-domain OCT was compared with intraoperative ultrasound pachymetry measurements. No significant difference was noted between central flap thickness measured by intraoperative pachymetry (107.2 ± 14 μm) and postoperative OCT (111.7 ± 11 μm; P=.07, correlation coefficient=0.86). Fourier-domain OCT measurements demonstrated functionally planar flap architecture (standard deviation [SD] of thickness across the flap=4.9 μm, SD range across the flap=2 to 9 μm) for the microkeratome flaps. The Amadeus II microkeratome with Med-Logics blades created thin, reproducible, functionally planar flaps as measured by Fourier-domain OCT. Central flap thickness measured by intraoperative ultrasound pachymetry was equivalent to that measured 2 weeks postoperatively by OCT.

Comparison of the Predictability, Uniformity and Stability of a Laser in Situ Keratomileusis Corneal Flap Created with a VisuMax Femtosecond Laser or a Moria Microkeratome

This prospective study compared the predictability, uniformity and stability of laser in situ keratomileusis corneal flap thickness created by a femtosecond laser or a classic microkeratome. Twenty-five femtosecond laser (VisuMax, Carl Zeiss Meditec) flaps and 38 microkeratome (Moria M3) flaps were measured using anterior segment optical coherence tomography at 1 week, 1 month and 6 months postoperatively. Flap thickness at seven points on each of the four meridians was calculated. At 6 months, VisuMax flaps showed better prediction than Moria flaps for central flap thickness. The standard deviation within individual flaps was smaller for VisuMax flaps and their index of symmetry was better. The mean thicknesses among the four eccentricities in the VisuMax flaps were the same, while Moria flaps were thicker at the 3-mm radius compared with the centre. The VisuMax femtosecond laser created corneal flaps with better predictability and uniformity, and similar reproducibility and stability, compared with the microkeratome.

Late onset corneal ectasia after LASIK surgery

Purpose To report late onset corneal ectasia following myopic LASIK. Methods A retrospective cohort case series. Nineteen patients with late onset corneal ectasia following LASIK procedure were examined at The Eye Center, Riyadh, Saudi Arabia. Patients underwent LASIK for myopia with spherical equivalent ranging from −1.4 to −13.75 diopters. Age and gender, history of systemic or local diseases, and time of onset of corneal ectasia were recorded. Eye examination and corneal topographical analyses were done before and after LASIK surgery. Results Nineteen patients (29 eyes) with late onset corneal ectasia were identified from 1998 to 2008 in 13 male and six female patients. The mean follow-up period was 108 ± 23 months (range 72–144 months). No patient had pre-operative identifiable risk factors for corneal ectasia and the mean time of onset was 57 ± 24 months (range 24–120 months after LASIK). The pre-operative values included mean central pachymetry 553 ± 25 μm, mean keratometry reading of 42.9 ± 1.5 diopters, average oblique cylinder of 1.4 ± 1.2 diopters, posterior surface elevation of 26 ± 2.1 diopters, corneal flap thickness of 160 μm, mean spherical equivalent of −5.6 ± 3.6 diopters, and calculated residual corneal stromal bed thickness was 288 ± 35 μm. Three (5 eyes) patients developed ectasia after pregnancy. Three (4 eyes) patients developed corneal ectasia following severe adenoviral keratoconjunctivitis and had positive PCR for adenovirus type 8. Conclusions Corneal ectasia may develop many years after LASIK surgery and symptoms could go undetected for some time. Pregnancy and adenoviral keratoconjunctivitis occurred post-operatively in six patients.

Factors Influencing Corneal Flap Thickness in Laser In Situ Keratomileusis with a Femtosecond Laser

PurposeTo evaluate factors responsible for the variability between intended and achieved corneal-flap thickness during femtosecond laser-assisted laser in situ keratomileusis (LASIK).MethodsA prospective, nonrandomized, case study was performed on 35 eyes of 18 consecutive patients who underwent LASIK surgery using the 60 kHz femtosecond laser microkeratome. Eyes were assigned to three different thickness groups, with 110-, 120-, or 130-µm cut depths. Anterior segment optical coherence tomography was used to assess the morphology of 35 LASIK flaps at postoperative one week postoperatively. The flap thickness was assessed at seven measuring points across each flap. Patient age, preoperative spherical equivalent, manual keratometry, preoperative central pachymetry, and regional variability of the cornea were evaluated to determine where they influenced the achieved corneal flap thickness.ResultsCuttings of all flaps were easily performed without any intraoperative complications. Flap-thickness measurements had a mean of 115.21 ± 4.98 µm (intended thickness, 110 µm), 121.90 ± 5.79 µm (intended, 120 µm), and 134.38 ± 5.04 µm (intended, 130 µm), respectively. There was no significant difference between the 110-µm and 120-µm groups when compared with the 130-µm group (one-way analysis of variance test, p > 0.05). Patients' age, preoperative spherical equivalent, manual keratometry, and preoperative central pachymetry did not affect the achieved flap thickness (Pearson correlations test, p > 0.05). The reproducibility of flap thickness in the central 1.5-mm radius area was more accurate than that in the peripheral 3.0 to 4.0-mm radius area (paired samples t-test, p < 0.05).ConclusionsFemtosecond laser-assisted LASIK is likely to reproduce a reliable thickness of the corneal flap, which is independent of corneal shape factors or refractive status. Future studies should focus on variations in corneal biomechanical factors, which may also play an important role in determining flap thickness.

Correlation analysis and corneal flap thickness changes among Moria SBK,90 and 110 microkeratome in laser in situ keratomileusis

目的 探讨使用MORIA公司SBK、90、110刀头切削角膜瓣的厚度变化及相关影响因素.方法 收集行准分子激光角膜原位磨镶术(LASIK)治疗的近视患者90例180眼,按术中使用刀头的不同分为SBK、90、110刀头组,每组30例60眼,均先右眼后左眼施行手术.术中测量角膜床厚度,对3组间角膜瓣厚度的差异进行比较,对角膜瓣厚度与年龄、屈光度、角膜厚度、曲率、角膜横径的相关性进行分析.结果 3组患者和手术眼的基线资料特征比较差异无统计学意义(P＞0.05).SBK刀头组右眼和左眼的角膜瓣厚度分别为(97.50±11.39)μm和(96.73±10.45)μm,差异无统计学意义(P＞0.05).逐步回归分析证实,SBK刀头组角膜瓣厚度与术前角膜厚度呈正相关(r=0.490,P=0.000)、与角膜横径呈负相关(r=-0.520,P=0.001).在90刀头组中,患者右眼和左眼的角膜瓣厚度分别为(128.03±12.03)μm和(123.40±12.38)μm,差异有统计学意义(P＜0.01).角膜瓣厚度与术前角膜厚度呈正相关(r=0.430,P=0.000),与年龄呈负相关(r=-0.360,P=0.002).110刀头组患者右眼和左眼的角膜瓣厚度分别为(140.53±15.14)μm和(135.23±18.03)μm,差异有统计学意义(P＜0.01),角膜瓣厚度与术前角膜厚度呈正相关(r=0.710,P=0.000).结论 MORIA角膜刀切削的角膜瓣厚度与术前角膜厚度有关,SBK刀头切削的角膜瓣厚度变异最小而110刀头者最大,LASIK术中用SBK刀头和90刀头能制作超薄或较薄的角膜瓣.术中应测量角膜床厚度,及时调整治疗方案,避免术后产生继发性圆锥角膜。

Safety and efficacy of femtosecond LASIK with reverse side cut

Abstract Purpose Laser in situ keratomileusis has several advantages over photorefractive keratectomy when performed properly in appropriate eyes. These include faster visual recovery, less discomfort after surgery, and milder and more predictable wound healing with less risk for haze. Lamellar corneal flap formation is the critical step in successful LASIK surgery. In our study we used femtosecond lasik with 90° hinge and 100 µm thickness flap wi Methods We performed femtosecond lasik in 58 eyes of 30 patients (mean age 35 y.o.) with AMO's IntraLase™ FS and STAR S4 IR™ Excimer Laser System. Criteria for inclusion were spherical myopia of ‐2 to ‐8.00 D, hyperopia up to 5 D, astigmatism miopic/hyperopic up to 4.50 D; stable refraction for 2 years; a best‐spectacle corrected vision (BSCVA) of at least 20/25 in each eye. Corneal flap thickness was 100µm and hinge position was 90 degrees with reverse 120° side cut. The optical zone of the ablation was from 6.5 to 7 mm, transition zone from 8 to 9 mm. Results Controls were made at 1day, 1 and 3 months. No flap decentration was observed in any case, we had one case of epithelial sloughing and one slightly irregular flap border. Spherical equivalent was within +/‐ 0.50 D and the cylinder was 0.50 D or less in all patients. Only 5% of patients showed marked discomfort and avversion to light for several days. Conclusion Flap creation is probably the most important step during laser in situ keratomileusis (LASIK), and complications during it can affect the rest of the procedure and cause permanent visual loss. In our exeprience the use of 100µm thickness flap with oblique side cut demonstrated itself to be a safe procedure with a very low complications rate and good refractive results.

Effect of microkeratome suction duration on corneal flap thickness and diameter in pigs.

To determine the effect of suction duration on thickness and diameter of corneal flap created by microkeratome in porcine eyes in laser in situ keratomileusis (LASIK). SIXTY PORCINE EYES WERE RANDOMLY ASSIGNED TO THREE GROUPS ACCORDING TO DIFFERENT SUCTION DURATIONS: group 1 (10 seconds), group 2 (20 seconds), and group 3 (30 seconds). A Moria M2 microkeratome (Moria, France) with a 160µm head was used to create a corneal flap. Corneal flap thickness was measured by automated ultrasonic pachymetry, and the flap diameter was measured by a vernier caliper. The flap thickness of group 1, group 2 and group 3 was (146.05±13.46)µm, (157.35±18.95)µm and (169.25±21.02)µm, respectively. There was a statistically significant difference among three groups (P=0.001). The mean flap diameter in groups 1, 2 and 3 was(8.63±0.19)mm, (8.89±0.24)mm and (9.06±0.18)mm, respectively. A statisti-cally significant difference was found among groups (P<0.01). In LASIK in porcine eyes, an increase in suction duration resulted in a thicker and greater flap.

Anterior Segment Optical Coherence Tomography Measurement of Flap Thickness After Myopic LASIK Using the Moria One Use-Plus Microkeratome

To analyze the accuracy and consistency of corneal flap thickness created in myopic LASIK using the Moria One Use-Plus microkeratome compared with the Moria M2 Single Use 90-microm microkeratome. Bilateral LASIK was performed in 68 myopic patients. Flaps were created using the One Use-Plus microkeratome in 82 eyes (41 patients) and the M2 90-microm microkeratome in 54 eyes (27 patients). Flap complications and visual outcomes were evaluated. Horizontal "High Res. Corneal" scan pattern of anterior segment optical coherence tomography (AS-OCT) was applied to measure flap thickness at five locations (0, +/-2, and +/-3.5 mm from the corneal vertex) on the first postoperative day. No significant differences were noted in flap complications and visual outcomes between groups. The central flap thickness was dramatically thinner in the One Use-Plus group (114.7+/-10.1 microm and 109.4+/-11.0 microm for right and left eyes, respectively) than in the M2 group (155.6+/-14.8 microm and 151.6+/-12.5 microm for right and left eyes, respectively) (P<.001). The One Use-Plus did not show a markedly better uniformity than the M2; the variation was mainly observed in the periphery. Multiple linear regression showed that for the One Use-Plus, the steeper the preoperative keratometry, the thicker the flap thickness, and for the M2, the thicker the preoperative pachymetry, the thicker the flap (P<.1). The One Use-Plus and M2 microkeratomes have similar safety and efficacy. The flap created by the One Use-Plus was much thinner than the flap created with the M2; however, the One Use-Plus can not realize a fully planar-shaped flap.

Changes in Ocular Response Analyzer Parameters After LASIK

To investigate changes in Ocular Response Analyzer parameters after myopic LASIK. Thirty myopic patients (60 eyes) undergoing bilateral LASIK were studied prospectively. Corneal hysteresis, corneal resistance factor, Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) measurements were obtained with the Ocular Response Analyzer before and after LASIK. Central corneal thickness and corneal flap thickness were also measured with optical coherence tomography. Compared with preoperative baseline values, corneal hysteresis, corneal resistance factor, IOPg, IOPcc, and central corneal thickness decreased postoperatively (P<.01). Corneal hysteresis (CH), corneal resistance factor (CRF), IOPg, IOPcc, and central corneal thickness (CCT) increased between 10 days and 3 months (post-hoc, P<.05). (The differences between the preoperative values and those at 3 months postoperatively are denoted by Delta.) The correlation of the ablation depth was stronger for DeltaCRF (r=0.457) than for DeltaCH (r=0.271). DeltaCH was negatively correlated to flap thickness (r=-0.361) and the ratio of flap thickness to preoperative central corneal thickness (r=-0.442) whereas DeltaCRF was not. DeltaCH was positively correlated with DeltaIOPcc, and DeltaCRF was positively correlated with DeltaIOPg. DeltaIOPg was positively correlated with DeltaCCT whereas DeltaIOPcc was not. Corneal biomechanical properties measured by corneal hysteresis and corneal resistance factor were decreased at 10 days after LASIK. Minimal recovery (approximately 10% of the changes) was achieved by 3 months. The changes in biomechanical properties may affect IOP measurement.

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.