Moria OUP-SBK microkeratome制作LASIK角膜瓣特点及因素分析

目的 观察LASIK术中应用Moria One Use-Plus SBK板层角膜刀制作角膜瓣的特点及相关因素.方法 LASIK手术113例(226眼)预设角膜瓣厚度为100μm.术后1周使用美国Optovue公司的RTVue-100傅立叶域光学相干断层扫描仪(OCT)测量角膜瓣厚度,与预设角膜瓣厚度进行差异性分析,与术前等效球镜,角膜直径,角膜厚度,角膜中央最大K值等进行相关性分析.结果 实际角膜瓣平均厚度为( 106.37±3.72)μm.右眼角膜瓣平均厚度为(107.17±4.28) μm,左眼角膜瓣平均厚度为(105.58±2.89)μm,两组差异有统计学意义(t=2.429,P＜0.05).实际角膜瓣厚度与术前角膜中央最大K值呈正相关( RK=0.302,PK＜0.05),与术前等效球镜、角膜直径、角膜厚度均无明显相关性.结论 Moria One Use-Plus SBK板层角膜刀制作角膜瓣预测性好,厚度均匀,角膜瓣厚度与术前角膜屈光力呈正相关.     

Flap measurements with the Hansatome microkeratome

PURPOSE: To evaluate flap thickness, flap diameter, and hinge length during laser in situ keratomileusis (LASIK) and to correlate these measurements with preoperative keratometric power, central corneal thickness, and patient refraction, gender, and age. METHODS: In this prospective study of 50 eyes of 28 patients (mean age 31 +/- 6.6 yr; range, 24 to 43 yr) results of LASIK for myopia were analyzed (mean spherical equivalent refraction of -7.16 +/- 1.69 D; range, -2.75 to -13.50 D). Corneal flaps were created using the Hansatome microkeratome (Baush & Lomb Surgical) with a 160-microm plate and a 9.5-mm suction ring. Corneal thickness was evaluated using an ultrasonic 50-MHz pachymeter (Sonogage Corneo Gage Plus) and the mean keratometric power was measured with a Corneal Analysis System videokeratographic unit (EyeSys). Data were analyzed using t-test, Pearson product moment correlation coefficient, and Spearman's rho non-parametric correlation coefficients. RESULTS: Mean corneal flap thickness was 142.6 +/- 20.8 microm (range, 107 to 177 microm), mean flap diameter was 9.9 +/- 0.3 mm (range, 9.2 to 10.5 mm), and mean hinge length was 6.2 +/- 0.4 mm (range, 5.2 to 7 mm). Statistically significant correlations (P<.05) were found between mean keratometric power and flap hinge length, mean keratometric power and flap diameter, preoperative spherical equivalent refraction and flap diameter, corneal thickness and flap hinge length, as well as patient age and corneal thickness. CONCLUSIONS: The Hansatome microkeratome was an effective and safe instrument in the creation of corneal flaps for LASIK. Consideration of preoperative keratometric power and corneal thickness may help to reduce or avoid complications.     

Factors that affect corneal flap thickness with the Hansatome microkeratome

PURPOSE: To evaluate factors that influence corneal flap thickness with the Hansatome microkeratome. METHODS: One hundred thirty-two eyes of 70 patients underwent laser in situ keratomileusis (LASIK). Corneal flap thickness was measured by subtracting the intraoperative corneal bed pachymetry measurement from intraoperative total corneal pachymetry. Variables examined included plate thickness, ring size, blade use, temperature, humidity, barometric pressure, age, average keratometric power, and preoperative corneal thickness. RESULTS: Mean flap thickness using a 180-microm plate was 143 +/- 19 microm (range 61 to 207 microm). Mean flap thickness using a 160-microm plate was 119 +/- 20 microm (range 83 to 159 microm). The difference was statistically significant (P < .05). Mean flap thickness using a 180-microm plate and the same blade on the right and left eye was 151 +/- 21 microm (range 113 to 200 microm) and 137 +/- 21 microm (range 91 to 191 microm), respectively. The 14-microm difference was statistically significant (P < .001). There was a slight negative correlation of flap thickness with humidity. There was a positive correlation with preoperative corneal thickness (pachymetry). CONCLUSION: The Hansatome tended to cut thinner flaps than anticipated based on the plate used. Flaps cut on the first eye were thicker than the second eye using the same blade. Thicker corneas tended to lead to thicker flaps. There was no correlation between flap thickness and microkeratome ring size, temperature, barometric pressure, patient age, or average keratometric power.     

Reproducibility of corneal flap thickness in laser in situ keratomileusis using the Hansatome microkeratome

PURPOSE: To evaluate the reproducibility of flap thickness during laser in situ keratomileusis (LASIK) and to analyze the effect of preoperative central corneal thickness and corneal keratometric power on flap thickness. SETTING: Department of Ophthalmology, Cerrahpasa Medical School, Istanbul, Turkey. METHODS: One hundred forty eyes with a mean preoperative pachymetry of 554.4 microm +/- 36.3 (SD) and a mean keratometry of 43.5 +/- 1.9 diopters had LASIK using the Hansatome automated microkeratome (Bausch & Lomb Surgical) and a 193 nm argon-fluoride excimer laser (Summit SVS Apex Plus). The 180 microm microkeratome plate was used in all procedures. Corneal thickness was measured with an ultrasonic pachymeter (Advent, Mentor O&O Inc.) before and during the flap procedure, and the difference was taken as flap thickness. The data were analyzed using a 1-tailed t test and Pearson correlation coefficient. RESULTS: The mean flap thickness was 120. 8 +/- 26.3 microm. There was a low correlation between baseline central corneal thickness and corneal flap thickness (P =.6, r = 0. 046). There was no correlation between preoperative keratometry and flap thickness (P =.01, r = 0.203). CONCLUSIONS: The Hansatome microkeratome does not always produce a corneal flap of the intended thickness. Factors other than keratometry and pachymetry must affect flap thickness.     

Optical low coherence reflectometry for noncontact measurements of flap thickness during laser in situ keratomileusis

OBJECTIVE: There is growing evidence that iatrogenic keratectasia after laser in situ keratomileusis (LASIK) for high corrections occurs more frequently than initially assumed, and that it may result from larger variation in flap thickness. DESIGN: Consecutive noncomparative case series PARTICIPANTS: Thirty-four patients who underwent LASIK for myopia and astigmatism (first treatment group) and 10 patients who received re-LASIK (retreatment group). METHODS: Central corneal thickness and thickness of the lamella during LASIK were determined by optical low coherence reflectometry (OLCR) and contact ultrasound pachymetry. MAIN OUTCOME MEASURES: Thickness of the flap and its standard deviation, as well as its correlation with age, sphere, cylinder, corneal thickness, intraocular pressure, and corneal refractive power (K-readings). RESULTS: The mean flap thickness of the first treatment group determined by OLCR was 130 +/- 29 microm; the 95 percentile was 169 microm and the 5 percentile was 86 microm. The flap thickness was not correlated with any of the investigated demographic or refractive parameters. The mean flap thickness of the retreatment group was 152 +/- 14 microm; the 95 percentile was 175 microm and the 5 percentile was 137 microm. Thus, the flap thickness of the retreatment group was significantly thicker compared with the first treatment group (P < 0.001). CONCLUSIONS: Optical low coherence reflectometry (OLCR) was shown to be an appropriate alternative to ultrasonic preoperative and intraoperative corneal pachymetry in laser assisted in situ keratomileusis. The lack of correlation between achieved flap thickness and preoperative clinical data, such as corneal thickness, corneal curvature, intraocular pressure, and refraction, emphasizes the importance of measuring flap thickness and corneal bed thickness during surgery.     

激光角膜上皮瓣下磨镶术和激光原位角膜磨镶术治疗中高度近视的对比研究

目的比较激光角膜瓣下磨镶术(LASEK)和激光原位角膜磨镶术(LASIK)治疗中高度近视的临床效果. 方法中高度近视患者198例(394只眼).其中LASEK手术治疗93例(184只眼), LASIK手术治疗105例(210只眼). 结果术后1天,LASIK 组28 %裸眼视力达到1.0,LASEK组无1例裸眼视力达到1.0.术后1周、1、3、6月裸眼视力大于或等于1.0者,两组比较差异无显著性 (P=0.36,P=0.58,P=0.44,P=0.64).角膜地形图分析平均角膜中央屈光力与周边屈光力的差异,LASEK组(0.69)明显小于LASIK组(2.62).结论 LASEK手术矫正中高度近视均有良好的治疗效果,是一种安全、有效、预测性好的屈光手术.     

Noncontact optical coherence tomography for measurement of corneal flap and residual stromal bed thickness after laser in situ keratomileusis

PURPOSE: Studies show significant variability in the thickness of laser in situ keratomileusis (LASIK) corneal flaps cut by various microkeratomes. Most studies of corneal flap thickness are based on contact ultrasonic pachymetry measurements taken during the surgical procedure. This study reports a technique to obtain reproducible corneal flap thickness and residual stromal bed thickness measurements using noncontact optical coherence tomography (OCT) following LASIK. METHODS: The corneal flap thicknesses of 26 eyes of 15 patients were measured following LASIK in which the flap was created using the Amadeus microkeratome: 160-microm head, 9.5-mm ring, 4.0-mm/s translation speed, 8000 oscillations/m, and full vacuum. Zeiss Humphrey OCT-2 line scans were performed on postoperative days 1 and 7. The raw data from three scans for each eye and day were exported to Microsoft Excel for processing, averaging, and analysis. RESULTS: The OCT corneal flap thickness and residual stromal bed thickness measurements correlated well with ultrasonic pachymetry measurements performed during surgery (R2 = .92). The OCT technique yielded reproducible results, as the variance for repeated scans was only 2.5% of the variance between eyes. In bilateral cases a single blade was used for both eyes. The mean flap thickness of 15 first eyes was significantly greater than that of the 10 second eyes: 181 +/- 31 microm vs. 143 +/- 41 microm (P < .01). A positive correlation was found between the preoperative pachymetry and corneal flap thickness. CONCLUSIONS: The OCT scan averaging technique is a reproducible, noncontact postoperative method for measuring corneal flap and residual stromal bed thicknesses following LASIK.     

Comparison of corneal flap thickness between primary eyes and fellow eyes using the Zyoptix XP microkeratome

PURPOSE: To evaluate corneal flap thickness created in myopic laser in situ keratomileusis (LASIK) using the Zyoptix XP 120 microkeratome (Bausch & Lomb). SETTING: University-based eye clinic. METHODS: Corneal thickness was measured preoperatively and intraoperatively after flap creation in 62 consecutive patients (124 eyes) who had LASIK for the correction of myopia. Corneal flap thickness was calculated by subtracting stromal bed thickness from total corneal thickness. In each patient, both corneas (right followed by left) were cut by 1 the same Zyoptix XP 120 microkeratome blade at the same session. RESULTS: The mean actual flap thickness was 115.34 microm +/- 16.34 (SD) in right eyes and 104.55 +/- 14.34 mum in left eyes. The mean actual flap thickness in right eyes was not statistically significantly different from the 120 microm proposed by the manufacturer (P = .142); however, the mean actual flap thickness in left eyes was statistically significantly different from the 120 microm (P<.001). The mean flap thickness in the second eye was also statistically significantly thinner than in the first eye (P<.001). CONCLUSIONS: The corneal flaps were thinner than expected when a Zyoptix XP 120 microkeratome was used in LASIK. Although the first cuts produced thinner flaps, this difference was not statistically significant. However, the second cuts produced significantly thinner flaps.     

Blade source effect on laser in situ keratomileusis flap thickness with the Amadeus I microkeratome

PURPOSE: To determine the effect of different blades on laser in situ keratomileusis (LASIK) flap thickness created with the Amadeus I microkeratome (Ziemer Ophthalmic Systems). SETTING: Emory University Department of Ophthalmology and Emory Vision, Atlanta, Georgia, USA. METHODS: This retrospective nonrandomized comparative case study from January 2005 through June 2006 compared LASIK flap thickness created with blades from 2 manufacturers: the Surepass from Surgical Instrument Systems and distributed by AMO and the ML7090 CLB distributed by Med-Logics, Inc. Sex, preoperative corneal thickness, surgical-eye sequence, flap thickness and variance, and residual stromal bed were evaluated in each group. RESULTS: This study evaluated 424 eyes of 226 patients. Surepass blades were used in 238 eyes and ML7090 CLB blades in 186 eyes. There were no significant differences between the 2 blade groups in preoperative corneal thickness, sex, or cases with corneal thickness greater than 550 microm. Mean flap thickness and variance were significantly lower in the ML7090 CLB group than in the Surepass group (P<.0001). There were no significant differences in flap thickness in either group based on sex; however, in both groups, flap thickness was significantly lower in second eyes and in eyes with a preoperative thickness less than 550 microm (P<.001). CONCLUSIONS: The Amadeus I microkeratome created thinner, more consistent LASIK flaps with the ML7090 CLB blade than with the Surepass blade. Preoperative corneal thickness and eye sequence affected flap thickness, while sex did not.     

Thin flap laser in situ keratomileusis: analysis of contrast sensitivity, visual, and refractive outcomes

PURPOSE: To analyze refractive, visual, and contrast sensitivity outcomes of laser in situ keratomileusis (LASIK) performed under thin flaps (less than 100 microm), and compare them with those of conventional thicker flaps. SETTING: Clínica Baviera, Instituto Oftalmológico Europeo, Madrid, Spain. METHODS: This retrospective study comprised 280 consecutive eyes that had LASIK for myopia using the Moria LSK-One microkeratome and the Technolas 217C excimer laser. Efficacy, predictability, and contrast sensitivity indicators were compared between 3 groups of flap thickness: thin (<100 microm, n = 105), medium (100 to 129 microm, n = 122), and thick (>130 microm, n = 53). RESULTS: Refractive results were excellent and comparable between the 3 groups; however, visual outcomes-measured as efficacy, postoperative evolution of uncorrected visual acuity, and contrast sensitivity-test were significantly better in the thin flap group. Efficacy results were 92.9%, 91.0%, and 81.0% in the thin, medium, and thick flap groups, respectively (P < .05), and the rate of enhancements was 0%, 2.3%, and 5.6%, respectively. With regard to contrast sensitivity, changes between preoperative and postoperative values at month 3 of follow-up, the thin flap group achieved the preoperative levels at 3 spatial frequencies (3, 6, and 18 cycles per degree), while the thicker flap groups maintained lower than preoperative levels at more than 2 spatial frequencies. When comparing contrast sensitivity values between the 3 groups, the thin flap group also obtained the best results at lower spatial frequencies. CONCLUSIONS: Thin flap LASIK is a safe technique to correct myopic defects since it blends the advantages of surface and lamellar procedures (minimal debilitation of corneal biomechanical architecture with the rapid and comfortable visual recovery of lamellar approaches). Moreover, it achieves excellent refractive outcomes, a lower rate of enhancements, and a good visual performance with better contrast sensitivity test results.     

Corneal stromal changes induced by myopic LASIK

PURPOSE. Despite the rapidly growing popularity of laser in situ keratomileusis (LASIK) in correction of myopia, the tissue responses have not been thoroughly investigated. The aim was to characterize morphologic changes induced by myopic LASIK in human corneal stroma. METHODS: Sixty-two myopic eyes were examined once at 3 days to 2 years after LASIK using in vivo confocal microscopy for measurement of flap thickness, keratocyte response zones, and objective grading of haze. RESULTS: Confocal microscopy revealed corneal flap interface particles in 100% of eyes and microfolds at the Bowman's layer in 96.8%. The flaps were thinner (112 +/- 25 microm) than intended (160 microm). The keratocyte activation in the stromal bed was greatest on the third postoperative day. Patients with increased interface reflectivity due to abnormal extracellular matrix or activated keratocytes at > or = 1 month (n = 9) had significantly thinner flaps than patients with normal interface reflectivity (n = 18; 114 +/- 12 versus 132 +/- 22 microm, P = 0.027). After 6 months the mean density of the most anterior layer of flap keratocytes was decreased. CONCLUSIONS: Keratocyte activation induced by LASIK was of short duration compared with that reported after photorefractive keratectomy. The flaps were thinner than expected, and microfolds and interface particles were common complications. The new findings such as increased interface reflectivity associated with thin flaps and the apparent loss of keratocytes in the most anterior flap 6 months to 2 years after surgery may have important clinical relevance.     

MORIA SBK、90、110刀头切削角膜瓣的厚度变化及相关因素分析

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。     

Partial flap during laser in situ keratomileusis: role of smaller diameter corneal flap of original thickness

PURPOSE: To report results of smaller diameter corneal flap of original thickness in the management of partial flap during laser in situ keratomileusis (LASIK). METHODS: Retrospective review of the case records of three patients (3 eyes) who had a partial corneal flap during LASIK. RESULTS: Retreatment was performed using an 8.5-mm-diameter corneal flap, which was smaller than the original partial flap of 9.5-mm diameter. The recut depth was maintained as the original cut depth of 160 microm. No intraoperative or postoperative complications were noted. At follow-up 4 weeks later, two patients had an uncorrected visual acuity of 20/20. One patient had uncorrected visual acuity of 20/40 that improved to preoperative best spectacle-corrected visual acuity of 20/30 with a correction of +0.50 -1.25 x 170 degrees. CONCLUSION: A smaller diameter corneal flap of original thickness can be used for retreatment of partial flap during LASIK. A thicker posterior stromal bed after laser ablation may be retained with this technique, compared to retreatment using a corneal flap of greater thickness.     

Reproducibility of LASIK flap thickness using the Hansatome microkeratome

PURPOSE: To evaluate the actual versus the expected thickness of laser in situ keratomileusis (LASIK) flaps and to determine the factors that affect flap thickness. SETTING: Centre For Sight, Queen Victoria Hospital, East Grinstead, United Kingdom. METHODS: A retrospective analysis of LASIK procedures in 757 consecutive eyes was done. The surgery was performed by a single surgeon using 2 Hansatome microkeratomes (Bausch & Lomb) with 160 microm and 180 microm heads. Patient age, preoperative manifest refraction, automated keratometry, preoperative central pachymetry, and intraoperative stromal pachymetry were evaluated to determine whether they influenced the actual flap thickness. RESULTS: Bilateral LASIK was performed in 343 patients (686 eyes). The 160 microm head was used in 641 eyes (84.6%) (Group 1) and the 180 microm head, in 116 eyes (15.4%) (Group 2). The mean preoperative manifest refraction spherical equivalent (SE) was -3.9 diopters (D) +/- 4.5 (SD) (range +7.4 to -25.0 D) in Group 1 and -4.4 +/- 3.7 D (range +7.1 to -12.9 D) in Group 2. The mean preoperative keratometry reading was 43.6 +/- 1.8 D (range 36.0 to 48.6 D) and 43.6 +/- 1.8 D (range 35.9 to 47.0 D), respectively; the mean preoperative central pachymetry was 543 +/- 35 microm (range 447 to 643 microm) and 548 +/- 31 microm (range 453 to 613 microm), respectively; and the mean flap thickness was 116.4 +/- 19.8 microm and 117.3 +/- 18.0 microm, respectively. The difference between the actual and the expected flap thickness in each group was statistically significant (P<.001). There was no significant difference in the actual flap thickness between the 2 Hansatomes. The preoperative SE and central pachymetry were the only factors that influenced the actual flap thickness (P<.05); thin flaps were more common with increasing myopia and increasing corneal thickness. CONCLUSIONS: Spherical equivalent and preoperative pachymetry were the principal factors that influenced flap thickness. Preoperative keratometry values and patient age did not influence the actual flap thickness.     

Corneal flap measurements in laser in situ keratomileusis using the Moria M2 automated microkeratome

PURPOSE: To evaluate accuracy and predictability and factors that influence the dimensions of the laser in situ keratomileusis (LASIK) corneal flap created with the Moria M2 automated microkeratome (Moria SA, Antony, France). METHODS: The flap thickness of 454 eyes of 243 consecutive patients was measured using subtraction ultrasonic pachymetry during LASIK with the Moria M2 microkeratome head 130 designed to create a 160-microm-thick flap. Flap dimensions were evaluated and measurements were correlated with preoperative parameters. A stepwise regression analysis was used to determine the factors that influenced actual flap thickness. RESULTS: The preoperative spherical equivalent refraction of the 454 eyes ranged from -12.125 diopters (D) to +6.25 D. Patient age ranged from 18 to 57 years (mean age: 31.3 +/- 8.8 years). Mean preoperative keratometric power K1 was 44.31 +/- 1.59 D and K2 was 43.32 +/- 1.54 D. Mean preoperative central comeal thickness was 552.4 +/- 32.5 microm (range: 466 to 665 microm). With an attempted thickness of 160 microm, the Moria M2 flap thickness ranged from 77 to 209 microm (mean: 153.3 +/- 19.0 microm). Mean horizontal flap diameter was 9.2 +/- 0.2 mm and mean hinge length 4.6 +/- 0.3 mm. Increasing flap thickness was found to correlate with increasing preoperative comeal thickness, younger patient age, and flatter preoperative keratometric power K1. CONCLUSIONS: Although the standard deviation of the flap thickness was relatively small, remarkable individual variation was noted. Therefore, the intraoperative calculation of the remaining stromal bed is recommended. Furthermore, the consideration of central corneal thickness, patient age, and preoperative keratometry are helpful parameters to avoid too deep ablation.     

Accuracy and precision of the amadeus microkeratome in producing LASIK flaps

PURPOSE: To evaluate the accuracy and precision of corneal flap thickness following laser in situ keratomileusis (LASIK) performed using the 140-, 160-, and 180-microm heads for the Amadeus microkeratome (AMO, Irvine, CA). SETTING: The study took place at the Cullen Eye Institute, Baylor College of Medicine, Houston. METHODS: In this prospective study, using the Amadeus microkeratome, LASIK flaps were cut in 51 right eyes and 50 left eyes with the 140-microm head, 25 right eyes and 25 left eyes with the 160-microm head, and five right eyes and one left eye with the 180-microm head. The same microkeratome blade was used for bilateral cases with the right eyes always undergoing surgery first. Eyes were grouped by order of blade use for statistical analysis. The effect of preoperative corneal thickness, keratometry values, blade oscillation and translation speeds, and blade reuse on flap thickness was evaluated. RESULTS: Mean flap thicknesses were 153 +/- 18 (range 97-187 microm) OD and 134 +/- 25 microm (range 79-174 microm) OS for the 140-microm head; 182 +/- 26 microm (range 105-220 microm) OD and 163 +/- 29 microm (range 105-216 microm) OS for the 160-microm head; and 235 +/- 24 microm (range 198-258 microm) for the 180-microm head. Flap thickness was significantly thicker for the first eyes cut (right eyes) and was positively correlated with increasing corneal thickness in both eyes. For the first eyes cut, flap thickness was also significantly thicker than the labeled thickness specified by the manufacturer. CONCLUSIONS: With the Amadeus microkeratome, LASIK flap thickness correlated with central corneal thickness for the 140-microm head. Reuse of the microkeratome blades produced significantly thinner LASIK flaps on second eyes cut.     

Corneal flap thickness in laser in situ keratomileusis using the summit Krumeich-Barraquer microkeratome

PURPOSE: To evaluate the thickness of corneal flaps created by the Summit Krumeich-Barraquer microkeratome (SKBM) (Alcon Surgical) and identify factors that may influence flap thickness. SETTING: SSK Ankara Eye Hospital, Ankara, Turkey. METHODS: Seventy-eight eyes of 50 patients who had laser in situ keratomileusis with the Asclepion-Meditec MEL 70 G-Scan excimer laser and the SKBM were prospectively evaluated. Preoperatively, the central corneal thickness, keratometry, visual acuity, and manifest refraction were measured. The microkeratome with the suction ring designed to create 160 microm thick and 9.0 to 9.5 mm diameter flaps was used in all eyes. Stromal bed thickness was measured with the Pachette ultrasonic pachymeter (DGH Technology, Inc.) after the flap was lifted. Flap thickness was calculated by subtracting the central stromal bed thickness from the preoperative central corneal thickness. RESULTS: The mean preoperative central corneal thickness was 546.7 microm +/- 31.9 (SD), the mean manifest refraction spherical equivalent was -6.8 +/- 3.4 diopters (D), and the mean corneal refractive power was 42.9 +/- 1.5 D. The mean corneal flap thickness created by the microkeratome was 154.9 +/- 19.3 microm (range 101 to 202 microm). There was no correlation between corneal flap thickness and the degree of myopia (P =.151) or the corneal refractive power (P =.257). There was a linear relationship between flap thickness and the preoperative central corneal thickness (P =.000). A posterior corneal stroma thicker than 250 microm was preserved in 87 eyes (98.9%). CONCLUSIONS: The SKBM produced corneal flaps that were consistently close to the intended thickness. Corneal flap thickness did not appear to be influenced by the degree of myopia or the corneal refractive power; however, there was a linear relationship between flap thickness and the preoperative central corneal thickness.     

Ultrasound evaluation of flap thickness, ablation depth, and corneal edema after laser in situ keratomileusis

PURPOSE: The aim of our study was to evaluate the predictability of flap thickness and changes in flap edema over time after laser in situ keratomileusis (LASIK). METHODS: LASIK was carried out in 30 eyes. The corneal flap was created with a Moria CB manual microkeratome with a flap thickness of 130 microm. Photoablation was performed with the Zeiss-Meditec MEL 70(G-Scan) flying spot excimer laser. Ultrasound pachymetric measurements were performed with the Humphrey Model 855 pachymeter. RESULTS: Preoperative mean corneal thickness was 568.43 +/- 34.6 microm. After LASIK, mean flap thickness was 133 +/- 26.4 microm. After excimer laser treatment, mean central corneal thickness decreased to a mean 392.4 +/- 37.4 microm. Five minutes after repositioning the flap, mean central corneal thickness was 572.1 +/- 43.4 microm. On the first postoperative day, it decreased to a mean 501.6 +/- 46.6 microm followed by additional decreases: mean 487.4 microm on day 5, 481.8 microm after 1 month, and 479.6 microm at 6 months. The actual photoablation depth was 10 microm less than the predicted depth (paired sample t-test, no statistically significant difference, P = .018). A significant linear correlation was found (Pearson, R =.725, P = .001) between predicted and measured photoablation depth. CONCLUSIONS: Corneal flap thickness had greater variability than expected. After flap creation, stromal and flap edema occurred, but decreased during the first five postoperative days and stabilized thereafter.     

Comparison of the IntraLase femtosecond laser and mechanical keratomes for laser in situ keratomileusis

PURPOSE: To compare laser in situ keratomileusis (LASIK) results obtained with the femtosecond laser (IntraLase Corp.) to those obtained using 2 popular mechanical microkeratomes. SETTING: Private practice, Greensboro, North Carolina, USA. METHODS: This retrospective analysis compared LASIK outcomes with the femtosecond laser to those with the Carriazo-Barraquer (CB) microkeratome (Moria, Inc.) and the Hansatome microkeratome (Bausch & Lomb, Inc.). The 3 groups were matched for enrollment criteria and were operated on under similar conditions by the same surgeon. RESULTS: There were 106 eyes in the IntraLase group, 126 eyes in the CB group, and 143 eyes in the Hansatome group. One day postoperatively, the uncorrected visual acuity (UCVA) results in the 3 groups were similar; at 3 months, the UCVA and the best spectacle-corrected visual acuity results were not significantly different. A manifest spheroequivalent of +/-0.50 diopter (D) was achieved in 91% of eyes in the IntraLase group, 73% of eyes in the CB group, and 74% of eyes in the Hansatome group (P<.01). IntraLase flaps were significantly thinner (P<.01) and varied less in thickness (P<.01) than flaps created with the other devices. The mean flap thickness was 114 microm +/- 14 (SD) with the IntraLase programmed for a 130 microm depth, 153 +/- 26 microm with the CB using a 130 microm plate, and 156 +/- 29 microm with the Hansatome using a 180 microm plate. Loose epithelium was encountered in 9.6% of eyes in the CB group and 7.7% of eyes in the Hansatome group but in no eye in the IntraLase group (P =.001). Surgically induced astigmatism in sphere corrections was significantly less with the IntraLase than with the other devices (P<.01). CONCLUSIONS: The IntraLase demonstrated more predictable flap thickness, better astigmatic neutrality, and decreased epithelial injury than 2 popular mechanical microkeratomes.     

Confocal microscopy changes in epithelial and stromal thickness up to 7 years after LASIK and photorefractive keratectomy for myopia

PURPOSE: To determine the long-term changes in epithelial, stromal, and corneal thickness after LASIK and photorefractive keratectomy (PRK). METHODS: In two prospective observational case series, 11 patients (16 eyes) received LASIK and 12 patients (18 eyes) received PRK to correct myopia or myopic astigmatism. None of the corneas had retreatment procedures. Corneas were examined using confocal microscopy before and at 1 month, and at 1, 2, 3, 5, and 7 years after surgery. Central thicknesses were measured from reflected light intensity profiles recorded by confocal microscopy. Postoperative epithelial thickness was compared to preoperative, and postoperative stromal and corneal thicknesses were compared to thickness at 1 month after surgery. RESULTS: In LASIK, epithelial thickness at 1 month (51 +/- 4 microm, n = 11) was greater than before surgery (41 +/- 4 microm, n = 16; P < .001) and remained thicker through 7 years (52 +/- 6 microm, n = 13; P < .001). Stromal and corneal thickness did not change between 1 month and 7 years after LASIK. After PRK, corneal thickness at 1 year (464 +/- 44 microm, n = 17) was greater than at 1 month (442 +/- 39 microm, n = 15; P = .001) and remained thicker at 7 years after PRK (471 +/- 45 microm, n = 17; P > .001). CONCLUSIONS: The early increase in central epithelial thickness after myopic LASIK persists for at least 7 years and is probably the result of epithelial hyperplasia. Central corneal thickness increases during the first year after PRK and remains stable thereafter up to 7 years.