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.     

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.     

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.     

Laser in situ keratomileusis flap thickness using the Hansatome microkeratome with zero compression heads

PURPOSE: To evaluate predictability and possible factors affecting flap thickness in laser in situ keratomileusis (LASIK) using the Hansatome microkeratome (Bausch & Lomb Surgical) with zero compression heads. SETTING: Zentrum für Refraktive Chirurgie Münster, Münster, Germany. METHODS: A prospective nonrandomized comparative (self-controlled) trial analyzing flap thickness in 153 consecutive patients having LASIK using the Hansatome microkeratome with zero compression was conducted. Two hundred thirty-eight eyes that had uncomplicated primary LASIK (n = 237) or secondary LASIK (n = 1) by the same surgeon and same technique using 4 different microkeratomes of the same model were evaluated. Each keratome cut was performed with a new Accuglide (Bausch & Lomb) blade in a 160 microm (n = 89), 180 microm (n = 128), or 200 microm (n = 21) Hansatome zero compression head coupled to a 8.5 mm (n = 106) or 9.5 mm (n = 131) suction ring. Only Hansatome elements with the same serial numbers were combined. Ultrasound subtraction pachymetry was routinely used to determine intraoperative flap thickness. Flap thickness was correlated with microkeratome head dimension, suction ring size, preoperative keratometry obtained by Orbscan IIz (Bausch & Lomb), preoperative corneal thickness as obtained by ultrasound pachymetry, refractive error, and age. RESULTS: Measured intraoperative flap thickness was significantly different (P<.01) from predicted flap thickness. The mean flap thickness was 97 microm +/- 18 (SD) (range 65 to 163 microm), 111 +/- 20 microm (range 61 to 177 microm), and 131 +/- 20 microm (range 89 to 162 microm) for the 160 microm, the 180 microm, and 200 microm heads, respectively. There was a good correlation between microkeratome head and corneal flap thickness. However, there was a variability between devices. There was a low correlation between baseline ultrasound pachymetry at the time of surgery and corneal flap thickness (r = .26) and a small effect of ring size. There was no correlation with keratometry, refractive error, or age. CONCLUSIONS: There was a remarkable difference in the flap thickness of microkeratomes of the same make and model. This emphasizes the need to measure intraoperative flap thickness and to evaluate every microkeratome separately. Factors affecting flap thickness seem to be more device dependent than patient related; obtaining flap thickness in the first eye did not enable predictions of the flap thickness in the fellow eye.     

Zyoptix XP与Hansatome角膜板层刀制作角膜瓣特点比较

目的比较Zyoptix XP与Hansatome角膜板层刀制作角膜瓣的特点,为临床使用提供参考。方法50例（100眼）近视眼患者随机分成两组,每组25例（50眼）,分别用Zyoptix XP120刀头、8.5mm负压环与Hansatome角膜板层刀160刀头、8.5mm负压环制作角膜瓣。制瓣前后分别用超声角膜测厚仪测量角膜厚度,计算实际角膜瓣厚度。制瓣后分别测量角膜瓣横径、纵径和蒂的长度,进行成组的两两比较t检验以及相关性分析,评价两种角膜板层刀制瓣特点。结果Zyoptix XP与Hansatome两组患     

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.     

微型板层角膜刀与飞秒激光制作角膜瓣对患者视力及角膜瓣厚度的影响

目的：比较微型板层角膜刀与飞秒激光制作角膜瓣对患者视力及角膜瓣厚度的影响。

方法：将2014-06/2015-05期间本院收治的近视屈光手术治疗的患者120例240眼,根据术式不同分为A组(微型板层角膜刀组)60例120眼和B组(飞秒激光组)60例120眼,然后将两组患者治疗后不同时间的视力情况及角膜瓣厚度相关指标进行比较。

结果：治疗后不同时间两组的视力情况差异无统计学意义(均P>0.05),而治疗后不同时间B组的角膜瓣厚度相关指标均好于A组,差异有统计学意义(均P<0.05),两组治疗后的评估指标间差异均有统计学意义(均P<0.05)。

结论：飞秒激光制作角膜瓣对患者角膜瓣厚度的影响明显好于微型板层角膜刀,两种治疗方式对视力的影响差异不明显。     

Effect of microkeratome suction duration on corneal flap thickness and incision angle

PURPOSE: To determine the effect of suction duration on corneal flap thickness and incision angle of the cut margin created by a microkeratome in a porcine eye. METHODS: Thirty porcine eyes were randomly assigned to three groups according to different suction duration: group 1 (10 sec), group 2 (35 sec), and group 3 (60 sec). The Hansatome microkeratome with a #160 plate and 8.5-mm-diameter suction ring was used to create a corneal flap with a diameter of 8.5 millimeters. Corneal flap thickness was measured by automated ultrasonic pachymetry, and the incision angle was assessed by measuring the angle of a sagittal section of the cornea using image analysis software. RESULTS: Mean corneal flap thickness in groups 1 (10 sec), 2 (35 sec), and 3 (60 sec) was 87.8 +/- 22.0 microm, 116.0 +/- 7.0 microm, and 127.2 +/- 16.8 microm, respectively. There was a statistically significant difference between groups 1 (10 sec) and 2 (35 sec) (P=.005) and groups 1 and 3 (P=.004). The mean incision angle in groups 1, 2, and 3 was 34.8 +/- 9.0 degrees, 44.4 +/- 16.1 degrees, and 48.24 +/- 15.3 degrees, respectively. A statistically significant difference was found between groups 1 (10 sec) and 2 (35 sec) (P=.044) and groups 1 (10 sec) and 3 (60 sec) (P<.001). CONCLUSION: In laser in situ keratomileusis in porcine eyes, an increase in suction duration resulted in a thicker flap and greater incision angle.     

Lower intraoperative flap complication rate with the Hansatome microkeratome compared to the Automated Corneal Shaper

PURPOSE: The purpose of this study was to retrospectively compare the incidence of intraoperative flap complications, such as partial flaps, donut-shaped flaps, central corneal cuts, and complete caps with the Hansatome and Automated Corneal Shaper (ACS) microkeratomes. METHODS: All laser in situ keratomileusis (LASIK) procedures performed by a single surgeon with the Hansatome or Automated Corneal Shaper in which intraocular pressure was verified with a pneumotonometer were reviewed. RESULTS: A total of 90 eyes had LASIK with the ACS microkeratome. Six of the ACS eyes (6.7%) had intraoperative flap complications (4 partial flaps, 1 donut-shaped flap, 0 central corneal cuts, 1 complete cap). Partial flaps and donut-shaped flaps were replaced without laser application and the procedure repeated 2 to 3 months later. Two of these eyes lost 2 lines and one lost 1 line of spectacle-corrected visual acuity at 6 months after repeat LASIK. The eye with the donut-shaped flap was treated with transepithelial photorefractive keratectomy (PRK) and had no change in spectacle-corrected visual acuity at 6 months after PRK. The eye with the complete cap had no change in spectacle-corrected visual acuity after laser ablation. Five hundred ninety-eight (598) eyes had LASIK with the Hansatome microkeratome. Two of the Hansatome eyes (0.3%) had a flap complication (1 partial flap and 1 donut-shaped flap). The first eye retained spectacle-corrected visual acuity at 6 months after repeat LASIK. The second eye had transepithelial PRK to eliminate the donut shaped flap with no loss of spectacle-corrected visual acuity at 6 months after surgery. The difference in flap complications between the two procedures was statistically significant (P < .01). There were no flap displacements following surgery in either group. CONCLUSION: Intraoperative flap complications are less likely to occur with the Hansatome microkeratome than with the ACS microkeratome.     

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

AIM: 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). METHODS: 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. RESULTS: 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). CONCLUSION: In LASIK in porcine eyes, an increase in suction duration resulted in a thicker and greater flap.     

LASIK术中负压吸引时间对猪角膜瓣厚度和直径的影响

目的:探讨准分子激光原位角膜磨镶术(LASIK)术中负压吸引时间对角膜瓣厚度和直径的影响。方法:根据负压吸引时间的不同将60只猪眼随机分为3组:组1(10s)、组2(20s)和组3(30s),使用法国产MoriaM2型角膜板层刀分别吸引角膜10s,20s和30s后切削角膜瓣,利用角膜超声测厚仪测量角膜瓣厚度,应用镀铬游标卡尺测量角膜瓣直径。结果:组1、2和3角膜瓣厚度分别为146.05±13.46,157.35±18.95和169.25±21.02μm,各组间比较有显著性差异(P=0.001)。各组的平均角膜瓣直径分别为8.63±0·19mm(组1,10s),8.89±0.24mm(组2,20s)和9.06±0·18mm(组3,30s)。各组间比较有显著性差异(P<0·01)。结论:LASIK术中随着负压吸引时间的延长,角膜瓣厚度和直径均增加。     

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.     

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.     

Moria M290一次性微型板层角膜刀制作角膜瓣的临床研究

目的：探讨Moria M290一次性微型板层角膜刀制作角膜瓣的可预测性及其影响因素。方法共入选104例（208只眼）拟行准分子激光原位角膜磨镶术（LASIK）患者参加此研究。术中使用Moria M290一次性微型板层角膜刀制作角膜瓣,所有患者均使用全新刀头,先右眼制瓣,然后左眼制瓣。制瓣前及制瓣后均使用超声角膜测厚仪测量术眼中央角膜厚度,同时测量角膜瓣直径及蒂长。结果平均角膜瓣厚度为（113．26±12．12）μm,其中右眼平均角膜瓣厚度为（121．42±12．08）μm,左眼平均角膜瓣厚度为（107．24±12．24）μm,两者比较有显著统计学差异（P ＜0．01）。右眼平均角膜瓣直径（9．46±0．15）mm,平均蒂长（5．16±0．25）mm;左眼平均角膜瓣直径（9．39±0．19）mm,平均蒂长（5．09±0．24）mm,两者比较均无显著性差异（P ＝0．08和P ＝0．95）。角膜瓣厚度与患者年龄,术前屈光度,术前角膜曲率及角膜直径均无明显相关性（分别P ＝0．56,P ＝0．50,P ＝0．19,P ＝0.42）,与术前中央角膜厚度呈正相关性（r ＝0．448,P ＜0．01）。结论 Moria M290一次性微型板层角膜刀制作角膜瓣预测性良好,角膜瓣厚度与术前中央角膜厚度呈正相关性。     

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.     

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

AIM: 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.METHODS: 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.RESULTS: Cutting of all flaps was easily performed without intraoperative complications. In the Alcon Wavelight FS200 femtosecond lasergroup, 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).CONCLUSION: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.     

自动角膜板层刀制作的角膜瓣与中央角膜曲率的关系

目的 :探讨平均中央角膜曲率与制作的角膜瓣平均直径、角膜瓣蒂长度的关系。方法 :对 30 0例 6 0 0只眼近视患者术前用角膜地形图测量平均中央角膜曲率 ,其中平坦角膜组、中等角膜曲率组和陡峭角膜组各 2 0 0只眼。采用NidekMK 2 0 0 0型自动角膜板层刀 ,负压环选择 8.5mm角膜瓣直径 ,制作角膜瓣后测量角膜瓣平均直径和蒂长度。结果 :平坦角膜组、中等角膜曲率组和陡峭角膜组的角膜瓣平均直径分别为 (8.35± 0 .34)mm、(8.6 6± 0 .30 )mm和 (8.93±0 .33)mm ;蒂长度分别为 (4.76± 0 .5 0 )mm、(5 .4 1± 0 .5 4 )mm和 (5 .81± 0 .4 3)mm ,差异均有非常显著性 (P <0 .0 1)。结论 :平均中央角膜曲率越高 ,角膜瓣平均直径越大 ,角膜瓣蒂越长。角膜瓣直径小 ,提供的切削区小 ;角膜瓣蒂短 ,易发生游离角膜瓣。手术医生术前应注意中央角膜曲率与角膜瓣的关系 ,预防术中角膜瓣并发症的发生。自动角膜刀具有操作简单、方便、安全性高的优点。     

Flap dimensions created with the Hansatome microkeratome: correlation with Orbscan-derived anterior segment data

PURPOSE: To investigate the flap dimensions created by Hansatome microkeratome (Bausch & Lomb Surgical) and their correlation with anterior segment biometric data measured by the Orbscan II (Bausch & Lomb). SETTING: Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey. METHODS: Forty-four myopic eyes of 22 patients (mean age 29 years +/- 7 [SD]) that had laser in situ keratomileusis surgery using the Hansatome microkeratome were enrolled in the study. Intraoperative images taken from video recordings of procedures were analyzed with image analysis software to determine flap size and hinge size. White-to-white corneal diameter, corneal curvatures (K(max), K(min)), corneal thickness, and anterior chamber depth were deducted from Orbscan measurement. Correlation analyses between flap dimensions and Orbscan-derived anterior segment biometric data were done. RESULTS: The mean corneal flap diameter was 9.56 +/- 0.28 mm in the right eye and 9.62 +/- 0.28 mm in the left eye. There was no difference in flap size between the right and left eyes (P=.43). The mean hinge size was 4.98 +/- 0.37 mm in the right eye and 5.07 +/- 0.41 mm in the left eye. There was no difference in hinge size between the right and left eyes (P=.46). There was a significant correlation between flap size and preoperative corneal thickness (P<.001, r=0.487), but there was no correlation between flap size and corneal curvature (P=.40, r=-0.12), white-to-white corneal diameter (P=.11, r=0.47), or anterior chamber depth (P=.52, r=0.09). There was also no correlation between hinge size and preoperative anterior segment biometric data. CONCLUSION: The Hansatome microkeratome produced a flap whose diameter is close to the intended flap diameter, and preoperative corneal thickness seems to be the important factor in determining flap size.