Comparison of excyclotorsion following graded inferior oblique recession for primary versus secondary inferior oblique overaction

AIM: To compare the changes in excyclotorsion after inferior oblique (IO) recession in patients with primary and secondary inferior oblique overaction (IOOA). METHODS: We retrospectively analyzed the data obtained from patients with IOOA who underwent graded IO recession. The patients were followed up for at least 3mo after surgery. Fundus photographs were taken pre- and postoperatively, and the sum of the angles of torsion in both eyes was used to analyze changes in excyclotorsion. Patients were divided into two groups: those diagnosed with primary IOOA were enrolled in the 1’IOOA group, and those diagnosed with secondary IOOA caused by superior oblique palsy (SOP) were enrolled in the 2’IOOA group. Excyclotorsion before and after surgery were compared between the two groups. RESULTS: A total of 78 patients were enrolled in this study: 34 eyes in the 1’IOOA group and 44 eyes in the 2’IOOA group. In the 78 patients, torsional angle significantly decreased from 15.31°±7.40° to 12.11°±6.53° after IO recession (P<0.001). Mean preoperative torsional angle was larger in the 2’IOOA group than in the 1’IOOA group (P=0.03). In both groups, excyclotorsion significantly decreased after IO recession (P=0.001 and P<0.001, respectively); however, there was no significant difference in the amounts of changes in excyclotorsion between the two groups. CONCLUSION: Excyclotorsion is significantly larger in secondary IOOA than in primary IOOA, and a significant decrease in the torsional angle occurs after IO recession in both types of IOOA.     

飞秒激光制瓣LASIK术中发生前房气泡51眼临床分析

目的 探讨飞秒激光制作角膜瓣导致前房气泡的原因.方法 回顾性病例对照研究.2009年7月至2010年6月接受飞秒激光制瓣的准分子激光原位角膜磨镶术(LASIK)患者1034例(2058眼),其中发生前房气泡的共48例(51眼)设为观察组,未发生前房气泡的2007眼为对照组,分析前房气泡发生的原因统计学处理采用成组t检验 结果 所有患者手术顺利,术后裸眼视力达到或超过术前矫正视力;观察组角膜直径较对照组小,差异有统计学意义(t=-9.21,P＜0.05);观察组角膜厚度、角膜曲率和Kappa角与对照组比较差异无统计学意义。结论 在瞳孔较大及精确的眼球眼踪系统下,飞秒激光制瓣时产生的前房气泡并不会对患者的术后视力产生影响;对于角膜直径较小的患者,应适当缩小角膜瓣直径,以避免前房气泡的发生.     

Subconjunctival gas bubble Formation during LASIK flap creation using femtosecond laser

PURPOSE: To report a patient who developed subconjunctival gas bubble formation during creation of a LASIK corneal flap with the IntraLase femtosecond laser. METHODS: Case report of a 19-year-old-man with compound myopic astigmatism and a normal preoperative evaluation who underwent bilateral simultaneous LASIK. RESULTS: The IntraLase FS15 was used to create an 8.8-mm diameter superior flap. Laser settings were 110-microm depth, 1.70-mJ bed and side-cut energy, 12-microm spot separation, 10-microm line separation, 70 degrees side-cut angle, 240-microm pocket start width, and 200-microm pocket start depth. The procedure was uneventful in the right eye whereas subconjunctival air bubbles were observed along the corneal limbus in the left eye (no bubbles were seen in the peripheral cornea). The patient was examined 30 minutes later, and the subconjunctival bubbles could still be observed. By the next day, the bubbles had disappeared completely. Postoperative uncorrected visual acuity was 20/20 in both eyes. CONCLUSIONS: Subconjuctival bubbles can be found after LASIK flap creation with a femtosecond laser.     

Comparison of the corneal response to laser in situ keratomileusis with flap creation using the FS15 and FS30 femtosecond lasers: clinical and confocal microscopy findings

PURPOSE: To compare the response of the cornea to laser in situ keratomileusis (LASIK) with flap creation using the IntraLase FS15 or FS30 femtosecond laser (IntraLase Corp.). SETTING: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: Twenty-three patients (31 eyes) who had LASIK with flap creation using the FS15 or FS30 laser were assessed by clinical examination and confocal microscopy in a nonrandomized parallel treatment group comparative trial. Eight FS15 patients (15 eyes) were examined preoperatively and 3 months postoperatively, and 14 FS30 patients (15 eyes) were examined 3 months postoperatively. RESULTS: No patient in either group had clinically significant flap interface haze. One FS15 eye and 1 FS30 eye had significant keratocyte activation at the flap interface. The mean difference between the actual flap thickness and intended flap thickness was 16.8 microm +/- 11.1 (SD) and 13.9 +/- 7.1 microm in the FS15 group and FS30 group, respectively (P = .49). The mean measured interface reflectivity was 156.4 +/- 88.6 confocal backscatter units (CBU) and 104.8 +/- 91.2 CBU, respectively (P = .15). The mean density of interface particles was 21.4 +/- 14.8 particles/mm(2) in the FS15 group and 11.0 +/- 7.1 particles/mm(2) in the FS30 group (P<.05). CONCLUSIONS: Both the FS15 and FS30 lasers provided more reproducible flap thickness and fewer interface particles than previously observed using microkeratomes. The response of corneal keratocytes to intra-LASIK was reduced compared with previous results in which higher raster energies were used. Compared with the FS15, there was an apparent reduction in overall interface reflectivity and fewer interface particles with the FS30 laser.     

Anterior chamber gas bubble formation during femtosecond laser flap creation for LASIK

PURPOSE: To report anterior chamber gas bubble formation during corneal flap creation in a myopic patient who underwent LASIK using a femtosecond laser (IntraLase). METHODS: A 30-year-old man underwent customized wavefront-guided LASIK for myopia. The IntraLase FS15 was used to create the corneal flap. RESULTS: During flap creation, gas bubble formation was noted in the anterior chamber, in addition to cavitation bubbles under the flap. Flap creation was successful and myopic ablation was uneventful. One day postoperatively, the flap was well apposed, and no air bubbles were present in the anterior chamber. CONCLUSIONS: Gas bubbles in the anterior chamber can be an infrequent occurrence during the use of femtosecond laser for corneal flap creation. Although gas bubbles do not hinder flap creation, their presence may interfere with eye-tracking mechanisms.     

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.     

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.     

飞秒激光与微型角膜刀制瓣LASIK术后视觉质量比较

背景 准分子激光角膜原位磨镶术(LASIK)是目前矫正近视和近视散光的主要手术方式之一,研究表明飞秒激光制瓣LASIK的安全性、精确性及可预测性明显优于微型角膜刀制瓣LASIK,但飞秒激光制瓣LASIK对患者视觉质量的影响仍是关注的焦点. 目的 比较Intralase FS60飞秒激光和Moria M2微型角膜刀制瓣LASIK矫正屈光不正的临床疗效及术后视觉质量. 方法 采用前瞻性非随机临床对照研究方法,纳入2012年3-8月于首都医科大学附属北京同仁医院拟行LASIK治疗近视及近视散光并符合纳入标准的患者共102例204眼.根据自愿的原则将患者分为2个组,各组患者基线特征匹配.飞秒激光制瓣组50例100眼行飞秒激光制瓣的LASIK,微型角膜刀制瓣组52例104眼行微型角膜刀制瓣的LASIK.分别于术前及术后3个月、6个月和1年采用波前像差仪分析6 mm瞳孔下Zernike系数及高阶像差的均方根值,采用Optec 6500视功能测试仪测定暗视及暗视+眩光状态下1.5、3.0、6.0、12.0和18.0 c/d空间频率的对比敏感度(CS).结果 飞秒激光制瓣组术后3个月、6个月和1年裸眼视力达到及超过术前最佳矫正视力(BCVA)者分别占95.1％、94.2％和93.9％,微型角膜刀制瓣组分别为94.2％、93.8％和93.2％.术前、术后3个月和术后1年,飞秒激光制瓣组等效球镜度(SE)分别为(-6.37±2.12)、(-0.26±0.45)和(-0.45±0.51)D,微型角膜刀制瓣组分别为(-6.25±2.05)、(-0.44±0.64)和(-0.35±0.59)D,术后3个月和1年2个组间SE比较差异均无统计学意义(u=l.194、1.429,均P＞0.05).术后3个月、6个月及1年飞秒激光制瓣组总高阶像差(RMSh)及各项高阶像差均明显低于微型角膜刀制瓣组(均P＜0.05).术后3个月和6个月飞秒激光制瓣组术眼在暗视及暗视+眩光状态下各空间频率的LogCS值均明显优于微型角膜刀制瓣组,差异均有统计学意义(均P＜0.05).术后1年,2个组间术眼在暗视状态下1.5 c/d空间频率的LogCS差异无统计学意义(P＞0.05),而飞秒激光制瓣组术眼在暗视及暗视+眩光状态下12.0 c/d和18.0 c/d空间频率的LogCS值均明显优于微型角膜刀制瓣组,差异均有统计学意义(均P＜0.05). 结论 飞秒激光制瓣的LASIK术后产生的高阶像差低于微型角膜刀制瓣的LASIK,视觉质量优于微型角膜刀制瓣的LASIK.     

Internal anterior chamber diameter using optical coherence tomography compared with white-to-white distances using automated measurements

PURPOSE: To compare internal horizontal anterior chamber (AC) diameter determined by optical coherence tomography (OCT) and horizontal corneal diameter (white-to-white [WTW]) using automated measurements. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. METHODS: Internal AC diameter and WTW distance was measured in 52 eyes of 26 patients using the Visante OCT (Carl Zeiss Meditec), IOLMaster (Carl Zeiss Meditec), and Orbscan IIz topography system (Bausch & Lomb). Statistical evaluation was performed using the Bland-Altman method and regression analysis for comparison of measurement techniques. The Kruskal-Wallis test was used to measure the repeatability of each device. RESULTS: The mean internal AC diameter was 12.45 mm +/- 0.53 (SD) with OCT; the mean WTW distance was 12.17 +/- 0.45 mm with the IOLMaster and 11.84 +/- 0.41 mm with the Orbscan IIz. A positive regression was determined for AC diameter and both WTW measurements. Measurement values varied little between both WTW measurement systems (R(2) = 0.9384). CONCLUSIONS: Anterior chamber measurement using optical coherence tomography (Visante OCT) was easy to handle and showed good repeatability. The internal horizontal diameter of the AC was larger than the horizontal corneal diameter determined by automated WTW measurements (IOLMaster, Orbscan IIz). Optical coherence tomography with the Visante OCT allows direct measurement of the AC width.     

Performance of the Hansatome microsuction ring for laser in situ keratomileusis in eyes with narrow palpebral apertures

PURPOSE: To evaluate the performance of a new microsuction ring during laser in situ keratomileusis (LASIK) in eyes with narrow palpebral apertures. SETTING: Singapore National Eye Centre, Singapore, Republic of Singapore. METHODS: Laser in situ keratomileusis was performed sequentially in both eyes of 33 Chinese patients. A randomization table was used to determine the control and test eyes. A standard suction ring (20.3 mm diameter) was used in control eyes, and a microsuction ring (19.0 mm diameter) was used in test eyes. Corneal flaps were created using the Hansatome microkeratome (Baush & Lomb). The following ring performance parameters were evaluated: flap diameter deviation (actual minus nominal flap diameter), ease of suction ring application, adequacy of suction, and overall microkeratome performance. Parameters 2 to 4 were rated by the surgeons using a subjective 1 to 100 scale. RESULTS: The mean flap diameter deviation was 0.45 mm in the control eyes and 0.22 mm in the study eyes; the mean difference was 0.23 mm (95% confidence interval, 0.39-0.07) (P<.001). For ease of application, the mean score of the microsuction ring was 100 and of the standard suction ring, 89.9. For adequacy of suction, the mean score of the microsuction ring was 99.7 and of the standard suction ring score, 98.2 (P = .13). The mean overall microkeratome performance score using the microsuction ring was 99.4 and using the standard suction ring, 94.6 (P = .011). CONCLUSION: The Hansatome microsuction ring was easy to apply during LASIK in eyes with narrow palpebral apertures, and there appeared to be no compromise of ring performance and safety.     

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。     

飞秒激光辅助LASIK制瓣术中发生前房气泡的影响因素和处理

目的:探讨飞秒激光辅助LASIK制瓣术中发生前房气泡的影响因素和处理方法.方法:飞秒激光辅助LASIK手术患者4859例9671眼,回顾性分析比较其中发生前房气泡眼的术前、术中及术后各参数.结果:患者51眼发生前房气泡,发生率为0.53%.术后1 mo裸眼视力(-0.076±0.09)与术前最佳矫正视力(-0.08±0.04)相比差异无统计学意义(t=-0.34,P=0.74).33眼(65%)不影响瞳孔跟踪,18眼(35%)在去红外跟踪模式下完成手术.跟踪组(31例33眼)术后1mo裸眼视力为-0.06±0.08,去跟踪组(18例18眼)术后1 mo裸眼视力为-0.11±0.09,两组相比差异无统计学意义(t=1.82,P=0.07).前房气泡在角膜缘9:00位发生率最高,其次为3:00位.其中47例双眼手术单眼发生前房气泡,发生前房气泡眼与其对侧眼各参数(术前等效球镜、角膜曲率、角膜直径、前房容积、前房深度、前房角度和术中飞秒激光能量等)差异均无明显统计学意义(P>0.05).结论:前房气泡是飞秒激光辅助LASIK手术中少见的并发症,会干扰准分子激光切削时的眼球跟踪,如术中妥善处理对术后早期视力无明显影响.发生前房气泡的直接或间接因素尚不清楚.     

Temporal hinge laser in situ keratomileusis: maximizing treatable stromal bed area

PURPOSE: To compare the treatable stromal bed area created by a temporal versus superior hinge laser in situ keratomileusis (LASIK) flap. SETTING: Assil Sinskey Eye Institute, Santa Monica, California, USA. METHODS: A randomized retrospective case review was performed of 2 subgroups (each with 12 eyes) of a cohort having LASIK for the correction of hyperopic astigmatism between August 2001 and March 2002. In 1 group, superior hinge LASIK was performed using the standard surgical technique for the 9.5 mm Hansatome suction ring. In the other group, the keratome was rotated 90 degrees such that a temporal hinge LASIK was performed with the 9.5 mm Hansatome suction ring. Corneal curvature (central mean keratometric value), flap diameter (arc length), and treatable stromal bed area were measured in each eye, and mean values were compared between the 2 groups. A treatable stromal bed area was defined as the circle centered over the entrance pupil, tangent to the hinge (devoid of hinge interference). RESULTS: The mean keratometry and mean flap diameter in the superior and temporal hinge groups measured 42.3 diopters (D) and 9.68 mm and 42.2 D and 9.69 mm, respectively. These differences were not significant (P=.882 for average keratometry and P=.943 for flap diameter). The mean treatable stromal bed area in the superior versus temporal hinge group measured 44.14 mm(2) and 62.25 mm(2), respectively. The difference between the 2 groups was highly significant (P<.0001). CONCLUSIONS: A large diameter, temporal hinge LASIK flap yielded a significantly greater area of treatable corneal stromal bed than a superior hinge flap. There are several clinical and theoretical advantages of optimizing stromal bed exposure for any given flap diameter.     

Visante OCT测量前房直径与IOL Master测量角膜水平直径的比较

目的分析比较应用Visante前段OCT测量的前房直径与应用IOL Master测量的角膜水平直径（白到白距离,white—to—white,WTW distance）之间的关系和差异。方法分别应用Visante OCT（Carl Zeiss Meditec）和IOL Master（Carl Zeiss Meditec）对42名患者（8d眼）进行前房直径和WTW的测量,分析比较这两者之间的差异和相关性。结果应用Visante OCT测量的前房直径为（12．11±0．33）mm,应用IOL Master测量的WTW值为（11．89±0．31）mm,两者之间的差异有非常显著的统计学意义（P〈0．01）。两者具有一定的相关性（r=0．82,P〈0．05）,前房直径比WTW长（0．21±0．19）mm,其差值95％可信区间为（-0．16mm,0．59mm）。结论应用IOL Master测量的角膜水平直径与Visante OCT测量的前房直径存在一定的差异,前段Visante OCT测量简易．数据图像更为直观,可靠性更好,在有晶状体眼人工晶状体植入等手术中具有更好的应用和指导价值。     

Confocal Comparison of Corneal Nerve Regeneration and Keratocyte Reaction between FS-LASIK, OUP-SBK, and Conventional LASIK

Purpose. We compared the regeneration characteristics of injured corneal subbasal nerve fibers (CSNFs) and keratocyte reaction following LASIK with a femtosecond laser (FS-LASIK), One Use-Plus Sub-Bowman's keratomileusis (OUP-SBK), and M2 90 microkeratome to provide a more suitable treatment strategy. Methods. A total of 22 eyes that underwent FS-LASIK, 32 eyes that underwent OUP-SBK, and 26 eyes that underwent conventional LASIK were analyzed by confocal microscopy. Morphologic modifications of corneal architecture were evaluated postsurgically at 1, 3, and 6 months, and comparisons were made by ANOVA analysis. Results. The density of stromal keratocytes in the FS-LASIK group was higher than that of OUP-SBK and conventional LASIK groups at 1 month postsurgery (P < 0.05), while in the OUP-SBK group it was higher than that of the FS-LASIK and conventional LASIK groups at 3 months postsurgery (P < 0.05). Regeneration of CSNFs was detected in 90% of eyes in all three groups around 3 mm of the peripheral flap at 1 month postoperation. CSNFs in 6.3% of the eyes in the OUP-SBK group were even observed around the peripheral flap at 6 mm 3 months after surgery, CSNFs were found in 62.5% of eyes (conventional LASIK), 72% of eyes (OUP-SBK), and 64.3% of eyes (FS-LASIK) around 3 mm near the center of the flap. While at 6 months, CSNFs were found in 100% of the eyes in all three groups. Conclusions. Keratocyte reactions after FS-LASIK and OUP-SBK were a little more severe than that after conventional LASIK. The repairing velocity of subbasal nerve fibers in the OUP-SBK group was a little faster than that of the FS and conventional LASIK groups.     

Thin flap laser in situ keratomileusis: flap dimensions with the Moria LSK-One manual microkeratome using the 100-microm head

PURPOSE: To determine the predictability and consistency of corneal flap thickness, flap diameter, and hinge length with the modern 100 microm head of the Moria LSK-One manual microkeratome. SETTING: Private clinic, office-based practice. METHODS: Forty-two consecutive eyes with no previous surgery having thin flap laser in situ keratomileusis with the Moria LSK-One manual microkeratome had a new 100 microm (predicted flap thickness) head used for flap creation. Flap thickness was measured intraoperatively by subtraction ultrasound pachymetry (difference between central corneal thickness before flap cutting and residual stromal bed thickness after flap lifting). Vertical flap diameter and nasal hinge length were measured with calipers. RESULTS: Mean flap thickness was 107 microm +/- 14 (SD) (range 82 to 137 microm). Standard deviation for mean vertical flap diameter was +/-0.24 mm. The cord length of the nasal hinge was variable with a mean of 4.26 +/- 0.63 mm (range 3.12 to 5.75 mm) in length. Postoperatively, there were no slipped flaps, flap striae, diffuse lamellar keratitis, or epithelial defects; there was 1 epithelial slide. At 1 day, the visual acuity was 20/20 or better in 76% of eyes. CONCLUSIONS: The 100 microm head of the Moria LSK-One manual microkeratome cut a very predictable flap thickness and diameter but with variable length hinges. This flap thickness predictability was superior to that in other series with thicker intended flaps cut with mechanical microkeratomes and is comparable to that reported with the IntraLase FS femtosecond laser. Visual recovery was rapid, epithelial risks minimal, efficiency superior, and cost nominal relative to femtosecond laser technology.     

IntraLase FS60和Femto LDV飞秒激光制作角膜瓣的特点

目的 探讨应用IntraLase FS60飞秒激光和Femto LDV飞秒激光制作的准分子激光原位角膜蘑镶术（LASIK）角膜瓣的特点.方法 前瞻性对照研究.拟行LASIK手术的近视患者60例（120眼）,根据角膜瓣制作方法不同分为两组,IntraLase FS60飞秒激光和Femto LDV飞秒激光组,每组各30例（60眼）.两组均制作预计110 μm厚度的角膜瓣.术前所有患者均进行常规检查并记录相关资料,包括年龄、屈光度、角膜曲率、角膜厚度等.术后1周,应用眼前节光学相干断层扫描仪（Visante OCT）分别测量每个角膜上0°、45°、90°和135°四条经线所在截面上特定5个点的角膜瓣厚度,并对每个角膜瓣上20个测量点的瓣厚度进行对比分析.采用独立样本t检验、单因素方差分析对相关数据进行统计学处理,分析角膜瓣的重现性、规整性和精确性.结果 角膜瓣重现性：术后1周,IntraLase FS60组和Femto LDV组中央区角膜瓣厚度均值分别为（111.2±3.3）μm和（108.1±3.0）μm,全角膜瓣厚度为（110.8±2.3）μm和（109.0±2.2）μm,变异范围为（22.0±6.6）μm和（23.7±5.8）μm,两组差异均无统计学意义（P均＞0.05）.角膜瓣均一性和规整性：两组角膜瓣厚度的均值均匀分散在预计值110 μm周围,差异均无统计学意义.IntraLase FS60组中央、旁中央、周边区域的角膜瓣厚度差异无统计学意义（F=1.213,P=0.300）;Femto LDV组中央和周边区域角膜瓣厚度差异存在统计学意义（F=3.925,P=0.021）,其他区域角膜瓣厚度差异无统计学意义.两组中各自双眼鼻侧和颞侧角膜瓣厚度对比,组间差异均无统计学意义.角膜上四条经线所在截面的平均角膜瓣厚度差异也无明显统计学意义.角膜瓣精确性：角膜上每个对应点的角膜瓣厚度与预计值110 μm差值的最大均值,IntraLase FS60组为6.2μm,Femto LDV组为6.7 μm.两组中与预计值差值≤5 μm的测量点,IntraLase FS60组有694个（占57.83%）,Femto LDV组有646个（占53.83%）,差异无统计学意义.结论 应用飞秒激光制作LASIK角膜瓣,具有较好的重现性和较高的精确性,角膜瓣形态均一、规整.IntraLase FS60飞秒激光和Femto LDV飞秒激光制作的角膜瓣形态特点相似.     

Randomized prospective clinical study comparing induced aberrations with IntraLase and Hansatome flap creation in fellow eyes: potential impact on wavefront-guided laser in situ keratomileusis

PURPOSE: To measure and compare the changes in objective wavefront aberration and subjective manifest refraction after laser in situ keratomileusis (LASIK) flap creation with a mechanical microkeratome and a femtosecond laser. SETTING: Private practice refractive surgery center, Irvine, California, USA. METHODS: This randomized prospective study comprised 9 patients (18 eyes) treated with a 2-step LASIK procedure: lamellar keratectomy with a Hansatome microkeratome (Bausch & Lomb) or the IntraLase femtosecond laser in fellow eyes followed by non-wavefront-guided (standard) excimer laser treatment with the Technolas 217A (Bausch & Lomb) excimer laser 10 weeks later. Fellow eyes were matched to within 0.75 diopter (D) sphere and 0.50 D cylinder. Patients were followed for 3 months after excimer laser treatment. Preoperative and post-flap creation wavefront aberrometry using a Hartmann-Shack aberrometer and manifest refraction were compared between the 2 groups. The same tests were performed 3 months after excimer laser ablation. RESULTS: Statistically significant changes were seen in defocus wavefront aberrations after Hansatome (P=.004) and IntraLase (P=.008) flap creation. A hyperopic shift in manifest refraction was noted in the Hansatome group after the creation of the corneal flap (P=.04); no statistically significant changes in manifest refraction were seen in the IntraLase group. Statistically significant changes in total higher-order aberrations (HOAs) (trefoil and quadrafoil Zernike terms) were seen after flap creation in the Hansatome group (P=.02). No significant changes in HOAs were noted after flap creation in the IntraLase group. After the flap was relifted and standard excimer laser ablation was performed, a statistically significant increase in coma occurred in the Hansatome group (P=.008). Standard refractive outcomes in the 2 groups were similar. CONCLUSIONS: The creation of the LASIK flap alone can modify the eye's optical characteristics in low-order aberrations and HOAs. A significant increase in HOAs was seen in the Hansatome group but not in the IntraLase group. This may have significant clinical implications in wavefront-guided LASIK treatments, which are based on measurements made before flap creation.     

Measurement of corneal curvature change after mechanical laser in situ keratomileusis flap creation and femtosecond laser flap creation

PURPOSE: To compare the change in corneal curvature from the predicted surgical radius (sculpted in the corneal stroma) and the measured postoperative radius of the first surface of the cornea after laser in situ keratomileusis (LASIK) for myopia correction using 2 methods of flap creation: mechanical microkeratome and femtosecond laser. SETTING: Vissum-Instituto Oftalmológico de Alicante, Alicante, Spain. METHODS: This retrospective consecutive nonrandomized comparative interventional case series included 85 eyes with myopia or myopic astigmatism treated using the Esiris excimer laser (Schwind). Patients were divided into 2 groups. One group had LASIK with an M2 microkeratome (Moria) (mechanical LASIK group) and the other, with a femtosecond laser (IntraLase FS, IntraLase Corp.) (femtosecond LASIK group). The relationship between the postsurgical corneal radius and the predicted sculpted radius as well as the mean value of the percentage change in the curvature radius were analyzed to obtain the effect on the refractive defect in each group. RESULTS: There were 44 eyes in the mechanical LASIK group and 41 eyes in the femtosecond LASIK group. A high correlation was found between the final corneal radius and the predicted sculpted radius in both groups (r(2) = 0.85). The mean percentage change in the curvature radius was -3.6% in the mechanical LASIK group and -1.6% in the femtosecond LASIK group (P<.001). The mean estimated refractive change was 1.2 diopters (D) and 0.8 D, respectively. CONCLUSIONS: The refractive change in corneal curvature, which related to the biomechanical response of the corneal surface after the flap cut and repositioning, was lower after femtosecond laser LASIK than after LASIK performed using a mechanical microkeratome. Estimations of refractive change induced by this response should be taken into account in surgery design.     

Corneal diameter measurements by corneal topography and angle-to-angle measurements by optical coherence tomography: evaluation of equivalence

PURPOSE: To determine the equivalence of corneal white-to-white (WTW) diameter and anterior segment angle-to-angle (ATA) measurements. SETTING: Vissum Instituto Oftalmologico de Alicante, Alicante, Spain. METHODS: Thirty eyes of 19 patients ranging in age from 20 to 51 years old with no previous ocular surgeries were included in this study. In all cases, the horizontal WTW diameter was measured with a tool provided by the CSO corneal topography system (Costruzione Strumenti Oftalmici) and the horizontal ATA was measured using an optical coherence tomography (OCT) system (Visante, Carl Zeiss Meditec AG). All measurements were repeated 3 times to evaluate intrasession repeatability. The correlation between WTW and ATA measurements was studied, and the interchangeability of the 2 parameters was assessed using the Bland and Altman method. RESULTS: The mean corneal WTW diameter was 12.25 mm +/- 0.49 (SD) (range 11.34 to 13.16 mm), and the mean ATA distance was 11.76 +/- 0.52 mm (range 10.03 to 12.92 mm). The difference between the 2 parameters was statistically significant (P<.01). A weak, although statistically significant, positive correlation (r = 0.39; P = .03) and a nonpredictive linear model were found. The Bland and Altman analysis showed large limits of agreement between WTW and ATA measurements that are clinically relevant (limits of agreement, -1.59 mm and 0.61 mm). The intrasession repeatability scores for the WTW and ATA measurements were good. CONCLUSIONS: The WTW and ATA distance measurements were not equivalent and thus are not interchangeable. There was no linear model for an accurate prediction of the ATA from the WTW.