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.     

LASIK flap characteristics using the Moria M2 microkeratome with the 90-microm single use head

PURPOSE: To evaluate the accuracy and consistency of corneal flap thickness, horizontal diameter, and hinge size with the Moria M2 90-microm single use head. METHODS: Fifty-two myopic patients (104 eyes), mean age 32.6 years, underwent bilateral LASIK with a superior hinged flap using the Moria M2 microkeratome (90-microm single use head). Prospective evaluation included flap thickness (subtraction method), diameter, hinge size, interface particles, intraoperative complications, and visual recovery. RESULTS: The mean preoperative spherical equivalent refraction was -5.72 +/- 2.59 diopters (D) (range: -2.88 to -10.75 D) and -5.84 +/- 2.73 D (range: -3.13 to -9.38 D) for right and left eyes, respectively. The mean preoperative central corneal thickness was 548 +/- 24 microm and 547 +/- 25 microm for right and left eyes, respectively. The mean preoperative steepest K was 44.12 +/- 1.28 D and 44.41 +/- 1.27 D for right and left eyes, respectively. Corneal diameter (white-to-white) was 12 +/- 0.4 mm and 11.9 +/- 0.4 mm for right and left eyes, respectively. The mean postoperative flap thickness was 109 +/- 18 microm (range: 67 to 152 microm) and 103 +/- 15 microm (range: 65 to 151 microm) for right and left eyes, respectively. The mean postoperative flap diameter was 9.4 +/- 0.3 mm (expected mean according to the nomogram given by the company was 9.5 mm). The mean postoperative hinge chord was 4.4 +/- 0.4 mm (expected mean 4.2 mm). No interface particles were detected on slit-lamp examination. CONCLUSIONS: The Moria M2 90-microm single use head is safe with reasonable predictability for LASIK flap creation.     

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.     

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.     

Comparison of flap thickness reproducibility using microkeratomes with a second motor for advancement

PURPOSE: To compare flap thickness and reproducibility of four different types of microkeratomes during LASIK. DESIGN: Retrospective, nonrandomized, comparative case series. PARTICIPANTS: Four hundred ninety consecutive eyes underwent LASIK and were evaluated by measuring the central flap thickness by subtractive pachymetry. METHODS: All flaps were created using the Bausch & Lomb (Miami, FL) Hansatome 180 head, the Alcon (Fort Worth, TX) Summit Krumeich Barraquer Microkeratome 160 head, the Moria (Antony, France) Carriazo Barraquer (CB) 130 head, or the Moria M2 110 head. RESULTS: The flap thickness measurements differed according to the microkeratome used and were 131+/-28 microm in 41 eyes (8.4%) with the Bausch & Lomb Hansatome 180 head, 162+/-21 microm in 127 eyes (25.9%) with the Alcon Summit Krumeich Barraquer Microkeratome (SKBM) 160 head, 157+/-40 microm in 65 eyes (13.3%) with the Moria CB 130 head, and 134+/-23 microm in 257 eyes (52.4%) with the Moria M2 110 head. The central flap thickness with the SKBM and Moria M2 was statistically significantly more reproducible than with the Moria CB (P< 0.0005). There is no correlation between flap thickness reproducibility and age, corneal thickness, or corneal keratometric values. However, considering all the microkeratomes, female gender had statistically significantly more variability than male gender (P<0.02). CONCLUSIONS: Based on these results, the greatest predictability of flap thickness was seen with the SKBM and Moria M2 microkeratomes, which both use a second motor for advancement. The greatest variability, noted with the Moria CB, was likely due to the manual translation feature and places further importance on the safety of the second motor and automation when performing LASIK.     

Corneal flap thickness in laser in situ keratomileusis using the Moria M2 microkeratome

PURPOSE: To determine the predictability of flap thickness in laser in situ keratomileusis (LASIK) using the Moria M2 microkeratome and identify factors that may be related to variations in flap thickness. SETTING: Laser Vision Correction Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, USA. METHODS: Charts of 208 patients having same-day bilateral LASIK using the Moria M2 microkeratome were reviewed. Intraoperative pachymetry was performed routinely. The right eye was always treated first. The same suction ring, stop, microkeratome head (110 microm or 130 microm), and blade were used in fellow eyes. Subtraction pachymetry was used to calculate flap thickness. Other collected data included age, keratometry, corneal diameter, and preoperative spherical equivalent (SE). RESULTS: With the 110 microm head and slow translation velocity in both eyes, the mean flap thickness was 151.6 microm +/- 24.0 (SD) and 148.5 +/- 24.3 microm in the right and left eyes, respectively. With the 110 microm head and fast translation velocity in both eyes, the mean thickness was 136.2 +/- 25.5 microm and 132.8 +/- 23.5 microm, respectively. With the 130 microm head and fast translation velocity, the mean flap thickness was 145.8 +/- 25.4 microm and 139.9 +/- 25.5 microm, respectively. Flaps were thinner with fast translation velocity, the 110 microm head, and presumably duller blades used in the left eyes. There was a weak but statistically significant inverse correlation between flap thickness and age and between flap thickness and SE. A stronger correlation was found in flap thickness between right and left eyes. CONCLUSIONS: Flap thickness with the Moria M2 microkeratome was variable. Fast translation velocity, a used (presumably duller) blade, and the 110 microm head produced thinner flaps. Given the potential variation in flap thickness (SD 23.5 to 25.5 microm), intraoperative pachymetry might be an adjunctive measure to prevent residual stromal beds that are thinner than planned, especially in patients with high myopia and/or thin corneas.     

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.     

Very high-frequency digital ultrasound measurement of the LASIK flap thickness profile using the IntraLase femtosecond laser and M2 and Carriazo-Pendular microkeratomes

PURPOSE: To evaluate the corneal aberrometric outcomes and corneal flap thickness profile after LASIK using three different devices for lamellar keratotomy: Moria M2 microkeratome, SCHWIND Carriazo-Pendular microkeratome, and IntraLase femtosecond laser. METHODS: Sixty-six myopic eyes of 33 patients who underwent LASIK with the SCHWIND ESIRIS excimer laser were enrolled in this study. Lamellar keratotomy was performed using three different devices that were assigned randomly to each patient: the Moria M2 microkeratome, SCHWIND Carriazo-Pendular microkeratome, and IntraLase femtosecond laser. The intended flap depth was 110 microm in all cases. Flap thickness profile, corneal aberrations, contrast sensitivity, and refractive outcomes were evaluated. RESULTS: Mean central flap thickness was 117.50 +/- 7.80, 118.08 +/- 8.34, and 115.95 +/- 6.22 microm for the M2, Carriazo-Pendular, and IntraLase systems, respectively. No significant differences were found among the groups. Nasal thicknesses were significantly larger for the M2 flaps compared to IntraLase (P < .05) and Carriazo-Pendular flaps (P = .046 only at 3-mm position). Temporal thicknesses were larger for the M2 flaps, although only differences between M2 and Carriazo-Pendular flaps reached statistical significance. Larger superior and inferior thicknesses were also observed for M2 flaps, although no statistically significant differences were found. Regarding corneal aberrometry, no statistically significant differences were observed in coma-like (P = .138) and spherical-like root-mean-square (P = .300). CONCLUSIONS: The M2, Carriazo-Pendular, and IntraLase systems create flaps of predictable thickness during lamellar keratotomy in LASIK. Additionally, the Carriazo-Pendular and IntraLase devices create flaps with a planar profile.     

Precision of flap measurements for laser in situ keratomileusis in 4428 eyes

PURPOSE: To determine the factor(s) that influence the dimensions and predictability of the LASIK corneal flap with the Automated Corneal Shaper (ACS) or the Summit Krumeich Barraquer microkeratome (SKBM). METHODS: We performed a retrospective, comparative interventional case study of 4,428 eyes. Flap dimensions were measured using subtraction ultrasonic pachymetry during LASIK with one of two microkeratomes. RESULTS: Mean preoperative corneal thickness for all eyes was 555 +/- 35 microm. Corneal curvature and refractive astigmatism were inversely related to preoperative corneal thickness (P<.001). With an attempted flap thickness of 160 microm, the ACS flap thickness averaged 119.8 +/- 22.9 microm; SKBM flaps averaged 160.9 +/- 24.1 microm (P<.001). The coefficient of variation for central pachymetry compared to flap thickness was 6.4% vs. 22.1%. Flap thickness at enhancement was 10 to 17 microm thicker than at primary surgery. An increase in flap thickness was associated with thicker preoperative pachymetry (P<.001) and younger age for both instruments (P<.001) whereas increasing flap thickness was related to flatter preoperative mean keratometry for the ACS (P<.001) and steeper mean keratometry for the SKBM (P=.005). Less preoperative hyperopia or more myopia was related to an increase in flap thickness only for the SKBM (P<.001). CONCLUSIONS: Flap thickness varies significantly depending on the microkeratome used. Factors that influence flap thickness are primarily corneal thickness, patient age, preoperative keratometry, preoperative refraction including astigmatism, and corneal diameter. By understanding the factors that affect flap thickness, one can select a microkeratome system to allow maximum refractive correction while minimizing the risk of ectasia.     

Influence of flap thickness on results of laser in situ keratomileusis for myopia

PURPOSE: To study whether flap thickness influences laser in situ keratomileusis (LASIK) results. METHODS: This comparative, non-randomized, retrospective study comprised 421 LASIK eyes (233 patients) with spherical equivalent refraction between -0.60 and -6.00 diopters (D). Laser in situ keratomileusis was performed with the Moria One manual microkeratome and the Chiron Technolas 217C laser. Depending on the flap thickness, the eyes were divided into three groups (group 1, flap thickness < or =100 microm; group 2, flap thickness > 100 microm and < 130 microm; and group 3, flap thickness > or = 130 pm). For each group uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, residual spherical equivalent refraction, and keratometric power (D) were measured 1 day, 1 week, 1 month, and 6 months after LASIK. Complications, retreatment, and correlation between flap thickness and preoperative corneal thickness and keratometric power were also analyzed. RESULTS: One month postoperatively, UCVA was > or = 20/20 in 76% (96 eyes), 56% (79 eyes), and 61% (93 eyes) of eyes in the three group, respectively (P = .015). One month postoperatively, UCVA was > or = 20/25 in 88% (111 eyes), 76% (108 eyes), and 76% (116 eyes) of eyes in the three groups, respectively (P = .015). Complication rate and retreatment rate were not statistically different among the groups. At 6-month follow-up, no statistically significant differences were noted in UCVA between the groups. Significant correlations between flap thickness and preoperative corneal thickness (P < .0001) and between flap thickness and preoperative keratometric power (P < .05) were found. CONCLUSION: Patients with flaps < or = 100 pm had better functional results at 1 month than those with thicker flaps. It may be important to perform LASIK with thin flaps to save corneal tissue in the stromal bed.     

Reproducibility of flap thickness with IntraLase FS and Moria LSK-1 and M2 microkeratomes

PURPOSE: To compare flap thickness reproducibility of the femtosecond laser and two mechanical microkeratomes. METHODS: Flap thickness for all eyes was measured as the difference between the preoperative (day of surgery) full corneal thickness and post-flap creation central stromal bed thickness using ultrasonic pachymetry. Flap thickness values produced by three different microkeratome systems were compared for accuracy and reproducibility. RESULTS: For 99 flaps created using the IntraLase FS laser with an intended thickness of 110 microm, the mean achieved thickness was 119 +/- 12 microm (range: 82 to 149 microm). In 100 eyes treated with the Moria LSK-1 microkeratome with an intended flap thickness of 160 microm, the mean achieved thickness was 130 +/- 19 microm (range: 71 to 186 microm). In 135 eyes treated with the Moria M2 microkeratome with an intended flap thickness of 130 microm, mean thickness was 142 +/- 24 microm (range: 84 to 203 microm). The standard deviation and range of corneal flap thickness created with the IntraLase FS laser was significantly smaller than either mechanical microkeratome (P < .0001). CONCLUSIONS: When compared to two commonly used mechanical microkeratomes, mean achieved flap thickness was more reproducible with the IntraLase FS laser, reducing the comparative risk of overly thick flaps.     

Factors predictive of LASIK flap thickness with the Hansatome zero compression microkeratome

PURPOSE: To determine the explanatory power of preoperative variables and comeal flap thickness in laser in situ keratomileusis (LASIK) using the Hansatome zero compression microkeratome (Bausch & Lomb, Rochester, NY). METHODS: A prospective, nonrandomized, comparative interventional case study was performed on 250 eyes of 129 consecutive patients who underwent LASIK surgery using the Hansatome zero compression microkeratome. A 160-microm or 180-microm microkeratome head and an 8.5- or 9.5-mm suction ring were used in the procedures. Preoperative measurements included refraction, spherical equivalent, keratometry, intraocular pressure, corneal white-to-white, anterior chamber depth, and corneal eccentricity. Corneal thickness was measured intraoperatively using ultrasonic pachymetry before and after flap creation, and the difference was taken as flap thickness. Flap diameter was measured with a corneal gauge. Data were analyzed using simple, multiple, stepwise linear and non-linear regression analyses and two-tailed t tests. RESULTS: The mean flap thickness was 124 +/- 17 microm with the nominal 160-microm head and 142 +/- 20 microm with the nominal 180-microm head. One third (33%) of the total variation in flap thickness could be accounted for by three preoperative variables: average corneal thickness, spherical equivalent refraction, and choice of 160- or 180-microm microkeratome head. A simple correlation of 0.114 was noted between corneal eccentricity and flap thickness, but this variable did not add significant explanatory power on multiple regression analysis. Linear regression analysis allowed determination of a flap thickness nomogram with a standard error of the estimate of 16.9 microm and a 95% confidence interval of +/- 33.1. CONCLUSIONS: Comeal thickness is the most systematic predictor of corneal flap thickness using the Hansatome microkeratome. Because three preoperative variables account for only 33% of the range in flap thickness, future studies should focus on variations in blade extension and corneal biomechanical factors, which may also play an important role in determining flap thickness.     

Moria M2 single use microkeratome head in 100 consecutive LASIK procedures

PURPOSE: To evaluate the safety and efficacy of the Moria M2 single use 130 microkeratome head in consecutive LASIK procedures for correction of myopia and myopic astigmatism. METHODS: One hundred eyes of 55 patients underwent LASIK in which the flaps were created with the Moria M2 microkeratome using the single use 130 head and excimer laser ablation was done with the Allegretto Wave-light laser. Flap parameters measured were: thickness, diameter, hinge length, and overall quality. Preoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, wavefront aberrations, and low contrast sensitivity were compared to postoperative values at 6-month follow-up. RESULTS: Mean flap thickness was 145 +/- 17.5 microm, mean flap diameter was 8.5 +/- 0.40 mm, and mean hinge cord length was 4.05 +/- 0.35 mm. At 6-month follow-up, UCVA improved from 20/200 (+/-0.24) to 20/18.5 (+/-0.12) and BSCVA improved from 20/20.5 (+/-0.18) to 20/17.5 (+/-0.11). CONCLUSIONS: The Moria M2 single use 130 microkeratome head appears to be safe and effective in performing LASIK procedures.     

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。     

准分子激光原位角膜磨镶术术前角膜厚度对术中角膜瓣厚度的影响

目的探讨准分子激光原位角膜磨镶术（laser in situ keratomileusis,LASIK）术前角膜厚度对术中角膜瓣厚度的影响。方法回顾性分析行双眼LASIK手术的患者150例（300眼）,按手术前角膜厚度分为四组：Ⅰ组36例,术前角膜厚度为（483.00±35.60）μm;Ⅱ组39例,术前角膜厚度为（516.00±36.33）μm;Ⅲ组36例,术前角膜厚度为（546.00±36.23）μm;Ⅳ组39例,术前角膜厚度为（579.00±37.30）μm。应用法国MoriaM2显微角膜刀制作角膜瓣,预期制作角膜瓣厚度160μm,每位患者用同一角膜刀制作双眼角膜瓣,手术顺序为先右眼后左眼。由MICKOPACH200P＋（SonomedInc.）超声测厚仪测量术前角膜厚度及术中激光切削前角膜瓣下基质厚度,角膜瓣厚度为术前角膜厚度减去术中激光切削前角膜瓣下基质厚度。对角膜瓣厚度进行统计学分析（方差分析和相关分析）。结果①角膜瓣厚度波动范围为79186μm,平均为（138.05±21.37）μm,角膜瓣厚度与术前角膜厚度呈正相关（r=0.710,P〈0.01）。②角膜瓣厚度与法 国Mo-riaM2显微角膜刀制作角膜瓣标识值（160μm）差异有显著的统计学意义（t=116.60,P〈0.01）,角膜瓣厚度比标识值薄。结论①角膜厚度影响角膜瓣厚度变化,两者呈正相关,手术前角膜越厚,角膜瓣越厚。②本研究所测得的角膜瓣厚度比预期值薄,角膜瓣厚度在一定范围内变化。     

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 with the Moria M2 single-use head 90 microkeratome

PURPOSE: To analyse the accuracy of corneal flap thickness created in laser-assisted in situ keratomileusis (LASIK) using the Moria Model 2 (M2) single-use head 90 microkeratome. METHODS: The corneal thickness of 300 (266 myopic and 34 hyperopic) eyes of 150 patients was measured by ultrasonic pachymetry preoperationally and intraoperationally after flap cut. The Moria M2 single-use head 90, intended to create a flap with a thickness of 120 microm, was used in all eyes. The right eye was always operated first and the left eye second, using the same blade. RESULTS: Mean corneal flap thickness was 115.4 microm (standard deviation [SD] 12.5) in the two eyes, 115.7 microm (SD 12.4, range 73-147 microm) in right eyes and 115.1 microm (SD 12.6, range 74-144 microm) in left eyes. Mean horizontal flap diameter was 9.1 mm (SD 0.2) and mean hinge length 4.1 mm (SD 0.1). There were no free flaps, incomplete flaps or flaps with buttonholes in the study. Occasional iron particles were observed in three (1.0%) eyes. CONCLUSIONS: As with most microkeratomes, the single-use head 90 microkeratome cut thinner flaps than were intended. The range of the cuts was relatively wide. However, thin flaps did not increase the rate of flap-related complications. The difference between the first and second eyes was not significant.     

Errors of residual stromal thickness estimation in LASIK.

BACKGROUND AND OBJECTIVE: To investigate inaccuracy and variability in residual stromal thickness estimation in LASIK by pachymetry and measurements of corneal thickness, flap thickness, and ablation depth. PATIENTS AND METHODS: In 73 eyes of 37 patients, preoperative and postoperative corneal thicknesses were obtained with slit-scanning elevation topography and the ultrasound pachymeter. LASIK was performed and corneal flaps were created with a microkeratome. Flap thickness and ablation depth (expected and achieved) were calculated. Residual stromal thickness estimation error was analyzed. RESULTS: The mean preoperative corneal thicknesses were 559.58 +/- 23.47 and 554.92 +/- 29.95 microm for the ultrasound pachymeter and slit-scanning elevation topography, respectively. Measurement differences ranged from -36 to 30 microm. With the pachymeter, calculated mean flap thickness was 139.58 +/- 17.59 microm. With this device, predicted ablation depth differed from achieved depth by 20% or more in approximately one-third (30.14%) of treated patients; ablation differences ranged from 10.0% to 19.99% in 37% of patients and 1.00% to 9.99% in 31.5% of patients. CONCLUSION: Imprecision of microkeratome cuts, preoperative corneal pachymetry, and laser ablation depth have a significant impact on the inaccuracy of residual stromal thickness prediction. Especially in patients with borderline corneal thickness, intraoperative pachymetry measurements and a residual stromal thickness higher than the safety margin of 250 microm are recommended to minimize iatrogenic ectasia.     

Reproducibility of corneal flap thickness in LASIK.

BACKGROUND: The purpose of the microkeratome in laser assisted in situ keratomileusis (LASIK) is to create a corneal flap of desired thickness, thus exposing the stroma. The accuracy and repeatability of intended flap thickness with the current microkeratome system has not been documented. The purpose of this study was to determine the precision and consistency of creating a corneal flap thickness of 160 microns with the Moria LSK-One microkeratome (distributed by Microtech, Inc., Doylestown, PA). PATIENTS AND METHODS: The records of 93 eyes from 67 patients who underwent LASIK were reviewed. The central corneal thickness was measured at baseline. The microkeratome using a "130" footplate was used to create an intended flap 160 microns thick, and the corneal thickness was then remeasured. RESULTS: The mean flap thickness for both eyes combined was 159 microns (S.D. = 28). There was no significant correlation between pre-flap corneal thickness or average K and the corneal flap thickness. CONCLUSION: This study provides evidence that the Moria LSK-One microkeratome creates reproducible LASIK flaps consistently near the intended 160 microns corneal flap thickness. This knowledge enables the surgeon to make a corneal flap with great confidence in the thickness of the excision. In addition, this study provides a clinical, in vivo model for testing corneal flap 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.