Effect of hinge width on corneal sensation and dry eye after laser in situ keratomileusis

PURPOSE: To investigate the effect of hinge width on corneal sensation and dry-eye syndrome after laser in situ keratomileusis (LASIK). Setting: TLC Laser Eye Center, Garden City, New York, USA. METHODS: Fifty-four patients at least 18 years of age had bilateral LASIK with a narrow nasal hinge microkeratome flap in 1 eye and a wider nasal hinge microkeratome flap in the other eye. In all eyes, the flaps were 160 microm in thickness with a diameter of 9.5 mm. Masked Cochet-Bonnet esthesiometry was performed in the central cornea preoperatively and at 1 week and 1, 3, and 6 months. Dry eye was evaluated at the same intervals by lissamine green corneal and conjunctival staining, Schirmer test with anesthesia, and tear-film breakup time. RESULTS: Corneal sensation was significantly reduced from preoperative levels through 6 months in the narrow-hinge group and through 3 months in the wider-hinge group (P< or =.002). The mean corneal sensation was greater in corneas with a wider hinge flap than in those with a narrow hinge flap at all postoperative examinations; the difference was significant at 1 and 3 months (P< or =.002). The loss of sensation was greatest at 1 week and improved at all subsequent examinations. Overall, dry-eye signs and symptoms were greatest immediately postoperatively and improved at subsequent intervals. CONCLUSIONS: Corneal sensation and dry-eye signs and symptoms improved at all intervals between 1 week and 6 months. The loss of corneal sensation and presence of dry-eye syndrome were greater in eyes with a narrow hinge flap than in eyes with a wider hinge flap.     

The incidence and risk factors for developing dry eye after myopic LASIK

PURPOSE: To determine the incidence of dry eye and its risk factors after myopic laser-assisted in situ keratomileusis (LASIK). DESIGN: Single-center, prospective randomized clinical trial of 35 adult patients, aged 24 to 54 years, with myopia undergoing LASIK. METHODS: setting and study population: Participants were randomized to undergo LASIK with a superior or a nasal hinge flap. They were evaluated at 1 week and 1, 3, and 6 months after surgery. intervention: Bilateral LASIK with either a superior-hinge Hansatome microkeratome (n = 17) or a nasal-hinge Amadeus microkeratome (n = 18). main outcome measures: The criterion for dry eye was a total corneal fluorescein staining score > or =3. Visual acuity, ocular surface parameters, and corneal sensitivity were also analyzed. Cox proportional-hazard regression was used to assess rate ratios (RRs) with 95% confidence intervals. RESULTS: The incidence of dry eye in the nasal- and superior-hinge group was eight (47.06%) of 17 and nine (52.94%) of 17 at 1 week, seven (38.89%) of 18 and seven (41.18%) of 17 at 1 month, four (25%) of 16 and three (17.65%) of 17 at 3 months, and two (12.50%) of 16 and six (35.29%) of 17 at 6 months, respectively. Dry eye was associated with level of preoperative myopia (RR 0.88/each diopter, P = .04), laser-calculated ablation depth (RR 1.01/microm, P = 0.01), and combined ablation depth and flap thickness (RR 1.01/microm, P = 0.01). CONCLUSIONS: Dry eye occurs commonly after LASIK surgery in patients with no history of dry eye. The risk of developing dry eye is correlated with the degree of preoperative myopia and the depth of laser treatment.     

角膜瓣蒂部位置对LASIK术后角膜知觉和泪膜的影响

目的了解颞侧蒂角膜瓣对准分子激光原位角膜磨镶术(LASIK)后的角膜知觉和泪膜的影响。方法将双眼屈光度相近的近视患者194例的左右眼角膜瓣蒂部随机置于角膜上方或颞侧,随后进行常规LASIK手术。分别在术前、术后1d、1周、1月、3月及6月时询问干眼症状,检测中央角膜知觉、荧光素试验、虎红染色、泪膜破裂时间和Schirmer’sⅠ试验。结果干涩感:在术后1周和1月时,上方蒂组的干涩感明显严重于颞侧蒂组(P<0.01)。异物感:两组间在术后1d和1周时存在差异(P<0.05)。灼烧感:两组间在术后1周时存在差异(P=0.025)。荧光素试验:两组间在术后1周时存在差异(P=0.003)。泪膜破裂时间:在术后所有时间点组间均存在差异(P<0.01)。虎红染色:在术后1周时,上方蒂组的虎红着色点明显多于颞侧蒂组(P=0.002)。Schirmer’sⅠ试验:两组间在术后1d、1周和1月时(P<0.01)。中央角膜知觉:两组间在术后1d、1周、1月和3月时(P<0.01)。结论颞侧蒂角膜瓣可保持较高的角膜敏感度,部分缓解干眼症。     

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.     

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.     

Dry eye after LASIK for myopia: Incidence and risk factors

PURPOSE: Patients frequently experience dry eye symptoms after laser-assisted in situ keratomileusis (LASIK). The purpose of this study was to determine the incidence and risk factors of dry eye after myopic LASIK. METHODS: In this retrospective case series 190 eyes that underwent LASIK were examined for a dry eye syndrome. All patents were asymptomatic for dry eyes before surgery. Assessments included subjective complaints of dry eye, tear break-up time (TBUT), corneal staining, corneal sensitivity test, and Schirmer I test. All values were compared before and at 1 week and 1.3 and 6 months after surgery. RESULTS: For the 190 eyes, chronic dry eye persisting 6 months or more after LASIK was diagnosed in 20 percent of the eyes. Mean patient age was 31 +/- 8 years. The risk for chronic dry eye was significantly associated with higher attempted refractive correction, greater ablation depth, and female sex (p=0.001). Subjective score for dryness was increased after LASIK. The greatest change from preoperative levels for all parameters was noted at 1 week. There were obvious decreases in TBUT and Schirmer value at 1, 3, and 6 months postoperatively relative to preoperative level (p<0.05). The Schirmer I test result was higher at 1 day but without statistical significance (p>0.05), but lower at 1 week and 3 and 6 months (p<0.05) after LASIK. Corneal sensitivity was decreased at 1 month and 3 months, and returned to the preoperative level at 6 months after LASIK. There was a statistically significant effect of age, sex, and mean spherical equivalent refraction on corneal sensitivity (p<0.001). CONCLUSIONS: Patients undergoing LASIK for myopia develop dry eye with compromised tear function at least 6 months after surgery. Women and patients requiring higher refractive correction have an increased risk for developing dry eye.     

Biomechanical effects of femtosecond and microkeratome-based flap creation: prospective contralateral examination of two patients

PURPOSE: To examine flap morphology, corneal topography, and aberrometry after flap creation with a femtosecond laser in one eye and a mechanical microkeratome in the fellow eye. Comparative outcomes after subsequent refractive laser correction were also investigated. METHODS: Two patients (4 eyes) were enrolled in a clinical study in which LASIK flaps were created using the IntraLase laser set at 90 or 100 microm in one eye and the Moria M2 microkeratome with a 90-microm head in the fellow eye. Pre- and postoperative flap data at 1 day, 1 week, and 1 month were collected before lifting the flap to perform a customized laser ablation (Alcon LADARVision4000 CustomCornea System). Postoperative laser data were collected at 1 week, 1 month, 3 and 6 months, and 1 year. Visual acuity, pachymetry, high-frequency flap ultrasound profilometry (Artemis Ultralink), topography, aberrometry (LADARWave), and refraction were examined and compared between eyes. RESULTS: Postoperative flap comparisons showed a hyperopic refractive shift in all four eyes with a shift of up to 1.00 diopter (D) in the microkeratome eyes and < 0.50 D in the IntraLase eyes. Corneal topography difference maps showed peripheral steepening that was more pronounced in the microkeratome versus IntraLase eyes (2.00 D vs 0.50 to 1.00 D, respectively). Spherical aberration by wavefront variably increased by 50% to 100% in the microkeratome eyes and remained virtually unchanged in the IntraLase eyes. At 3-month postoperative laser treatment, visual acuity was 20/15 for both eyes in patient 1 and 20/15 in the right eye (IntraLase) and 20/25 in the left eye (microkeratome) in patient 2. Aberrometry revealed a two-fold greater level of higher order aberrations in microkeratome eyes than in IntraLase eyes throughout the postoperative laser period. CONCLUSIONS: Femtosecond laser and mechanical methods of flap creation lead to subtle biomechanically induced aberrations, which appear more prominent with the mechanical Moria M2 microkeratome in this small case study. Further study with a larger patient population is warranted to determine whether these differences are statistically significant.     

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.     

Effect of hinge position on corneal sensation and dry eye after laser in situ keratomileusis using a femtosecond laser

PURPOSE: To determine whether hinge position has an effect on corneal sensation and dry-eye symptoms after myopic laser in situ keratomileusis (LASIK) performed with the IntraLase femtosecond laser (IntraLase Corp.). SETTING: University-based academic practice, Ann Arbor, Michigan, USA. METHODS: Sixty-six consecutive eyes of 33 patients were prospectively evaluated in a randomized contralateral-eye study to compare the difference between superior-hinge and temporal-hinge locations after bilateral myopic LASIK with the IntraLase femtosecond laser. Central Cochet-Bonnet esthesiometry, the Ocular Surface Disease Index (OSDI) questionnaire, Schirmer test with anesthesia, tear breakup time (TBUT), corneal fluorescein, and conjunctival lissamine green staining were evaluated preoperatively as well as 1 week and 1, 3, 6, and 12 months after surgery. RESULTS: Corneal sensation was reduced with both superior-hinged and temporal-hinged LASIK flaps 1 week and 1, 3, 6, and 12 months after surgery (P<.0001). There was no difference in corneal sensation between superior-hinged and temporal-hinged flaps at any time point. The OSDI score was increased in 22.6% of patients at 1 week and 21.9% at 1 month (P<.00001), and corneal fluorescein staining was increased in 18% at 1 week. There were no differences in the OSDI, Schirmer with anesthesia, TBUT, corneal fluorescein, or conjunctival lissamine green staining when preoperative values and hinge location were compared. CONCLUSIONS: Mild dry-eye disease was present early after myopic LASIK with the IntraLase laser. Hinge position had no effect on central corneal sensation or dry-eye disease.     

角膜瓣蒂位置对LASIK术后干眼症发生率影响随机对照研究的Meta分析

背景干眼症是准分子激光角膜原位磨镶术（LASIK）术后早期最常见的并发症。有研究提出术后干眼症的发生率与术中角膜瓣蒂的位置有关,然而也有研究认为两者关系不大。目的系统评价LASIK术中鼻／颞侧蒂和上方蒂角膜瓣对术后干眼症发生率的影响。方法采用严密设计的检索策略并选择关联检索词对1990--2011年已发表的有关比较LASIK术中不同位置角膜瓣蒂术后干眼症发生情况的随机对照研究进行检索,检索的数据库包括Medline、Embase、Cochrane图书馆和中国期刊全文数据库（CNKI）,由2名研究者独立提取资料,对符合纳入标准的文献进行Meta分析。Meta分析中纳入的关联结局指标包括术后1周及3、6、12个月时泪膜破裂时间（BUT）、SchirmerⅠ试验及角膜敏感性。采用RevMan5．0统计学软件进行统计分析,并按照Jadad量表对检索文献的证据等级进行评价。若纳入的各项研究无异质性（即P≥0．1,异质性检验,2〈50％）,采用固定效应模型进行分析,反之则采用随机效应模型。结果共检索到符合纳入标准的相关随机对照临床试验10篇,其中3篇未分别给出术后各组结局指标的详细资料,故予以排除,有7篇随机对照研究符合条件纳入,共331例652眼。纳入的文献经Jadad评分均为3分以上,其中5篇文献530眼对BUT进行评价,7篇文献652眼进行SchirmerI试验,4篇文献320眼对术后角膜知觉进行了评价,文献之间均无明显异质性（,〈50％）。Meta分析显示术后第1周上方蒂组的BUT明显短于鼻／颞侧蒂组,差异有统计学意义（WMD=-0．42,95％CI：-0．79～-0．06,P=0．020）,而在术后3个月和6～12个月2个组差异均无统计学意义（P〉0．05）。术后3个月鼻／颞侧蒂组角膜敏感性明显高于上方蒂组,差异有统计学意义（WMD=-0．62,95％CI：-1．09～-0．19,P=0．005）,而在术后1周和6～12个月2个组比较差异无统计学意义（P〉0．05）。2个组SchirmerⅠ试验结果在术后各时间点差异均无统计学意义（P〉0．05）。结论LASIK术中保留鼻侧或颞侧角膜瓣蒂能一定程度地缓解术后干眼症的发生和严重程度,今后还需要更多高质量、大样本的随机对照研究来证明二者之间的联系。     

Femtosecond laser and microkeratome corneal flaps: comparison of stromal wound healing and inflammation

PURPOSE: To examine early postoperative wound healing in rabbit corneas that had LASIK flaps formed with three different models (15 KHz, 30 KhZ, and 60 KHz) of a femtosecond laser compared with flaps formed with a microkeratome. METHODS: Thirty-nine rabbit eyes were randomized to receive either no surgery or corneal flaps formed with one of the lasers or the microkeratome. Sixteen eyes also had lamellar cuts with no side cuts with the 30 KHz laser. Animals were sacrificed and corneas processed as frozen sections or fixed for transmission electron microscopy. Frozen sections were evaluated with the TUNEL assay to detect apoptosis, immunocytochemistry for Ki67 to detect cell mitosis, and immunocytochemistry for CD11b to detect mononuclear cells. RESULTS: Rabbit corneas that had flaps formed with the 15 KHz laser had significantly more stromal cell death, greater stromal cell proliferation, and greater monocyte influx in the central and peripheral comea at 24 hours after surgery than corneas that had flaps formed with the 30 KHz or 60 KHz laser or the microkeratome. Results of the 60 KHz laser and microkeratome were not significantly different for any of the parameters at 24 hours, except for mitotic stromal cells at the flap margin. Transmission electron microscopy revealed that the primary mode of stromal cell death at 24 hours after laser ablation was necrosis. CONCLUSIONS: Stromal cell necrosis associated with femtosecond laser flap formation likely contributes to greater inflammation after LASIK performed with the femtosecond laser, especially with higher energy levels that result in greater keratocyte cell death.     

The effect of hinge position and depth plate on the rate of recovery of corneal sensation following LASIK

PURPOSE: To evaluate and compare the effect of hinge position and flap thickness on recovery rate of corneal sensation after (LASIK). DESIGN: Prospective, randomized clinical study. METHODS: Forty eyes of 40 patients underwent LASIK to correct myopia ranging from -1.00 to -2.50 diopters. Corneal sensitivity was measured preoperatively and each month after surgery until recovery to preoperative level. The nasal-hinged ACS microkeratome (NH) with depth plates of 130 and 160 microm and the superior-hinged Hansatome microkeratome (SH) with depth plates of 160 and 180 microm were used for corneal flap creation. The eyes were divided into four groups according to the hinge position and depth plate (DP): group 1, NH and 130 microm DP; group 2, NH and 160 microm DP; group 3, SH and 160 microm DP; group 4, SH and 180 microm DP. RESULTS: Corneal sensitivity returned to preoperative level after 3.7 (+/- 0.4), 4.4 (+/- 0.6), 5.4 (+/- 0.8), and 5.8 (+/- 0.9) months, respectively, in groups 1, 2, 3, and 4. Statistically significant differences were found between groups 1 and 2, but not between groups 3 and 4. Corneal sensitivity gradually returned to preoperative levels in all groups. Sensitivity of the hinge area was higher than other areas at every time point. CONCLUSIONS: The results suggest that after LASIK, hinge position and flap thickness seem to be important factors in the rate of return of corneal sensitivity. A thin flap with a nasally placed hinge is associated with the most rapid recovery of corneal sensitivity.     

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.     

飞秒激光和角膜板层刀制瓣LASIK术后临床效果的比较

目的：观察飞秒激光和角膜板层刀制瓣准分子激光原位角膜磨镶术(LASIK)术后的临床疗效。

方法：对本院眼视光中心行飞秒激光和角膜板层刀制瓣LASIK术的近视患者各50例100眼在术后1、3、6mo做裸眼视力、残余屈光度、干眼症调查、高阶像差检查。

结果：两组的裸眼视力及残留屈光度在术后6mo内差异均无统计学意义(P>0.05); 干眼症状调查显示：术后1、3mo,两组比较差异均有统计学意义(P<0.05); 术后6mo两组比较,差异无统计学意义(P>0.05); 两组术后1、3、6mo高阶像差与术前对比均增大,差异有统计学意义(P<0.05),两组术后1mo水平彗差、垂直彗差及球差之间差异均无统计学意义(P>0.05); 两组术后3、6mo水平彗差、垂直彗差之间差异均无统计学意义(P>0.05),但飞秒激光制瓣LASIK术球差变化值小于角膜板层刀制瓣LASIK术,差异有统计学意义(P<0.05)。

结论：飞秒激光制瓣LASIK术是一种安全、有效、稳定的手术方式,干眼症发生率低,术后视觉质量更优于角膜板层刀制瓣LASIK。     

A comparative confocal microscopy analysis after LASIK with the IntraLase femtosecond laser vs Hansatome microkeratome

PURPOSE: To evaluate and compare confocal microscopy findings between a femtosecond laser and a mechanical microkeratome. METHODS: Eighteen eyes of nine patients underwent LASIK. Corneal flaps were created with the femtosecond laser in the right eyes and a mechanical microkeratome in the left eyes. The corneal flap interface was analyzed in all eyes with a confocal microscope at 1 week and 1 month postoperatively. RESULTS: All eyes showed small reflective particles at the corneal flap interface. The mean number of reflective particles was not statistically significantly different at 1 week (P = .078) and 1 month (P = .28) using a femtosecond laser and a mechanical microkeratome. CONCLUSIONS: Confocal microscopy findings at the corneal flap interface showed a similar number of particles using both systems.     

LASIK术后角膜知觉的变化及干眼的发生

目的：探讨准分子激光原位角膜磨镶术（LASIK）后角膜知觉的变化及其对干眼的影响与切削深度的关系。 方法：观察上方蒂做瓣的LASIK手术30例（60眼），观察指标包括患者术中切削深度及术前，术后1wk，lmo，3mo的角膜中央知觉、基础泪液分泌量、泪膜破裂时间（BUT）、角膜荧光素钠染色评分、干眼主觉症状评分。 结果：术后1wk，1mo角膜知觉敏感度与术前相比差异均非常显著（P〈0．01），术后3mo平与术前相比差异无统计学意义（P〉0．05）；术后1wk患者的主觉症状与术前相比无显著差异（P=0．079〉0．05），术后mo时差异显著（P=0．025〈0．05），术后3mo时差异极其显著（P=0．001〈0．01）；患者术后泪流量在术后1wk：1mo时明显低于术前（P〈0．01），直至术后3mo仍未恢复至术前水平（P〈0．01）；术后1wk，1mo，3mo泪膜破裂时间缩短，术后3mo时与术前相比差异显著（P〈0．01）；角膜荧光素钠染色评分方面，术后1mo时角膜上皮损伤最明显，术后3㈤时与术前仍有显著差异（P〈0．01）直线回归与相关分析结果，说明在两者之间存在直线相关的关系r=0．798，P〈0．01。 结论：LASIK术后角膜中央知觉明显下降并随时间延续而逐渐恢复，3mo时与术前无统计学差异；但是干眼的相关指标并未随之恢复至术前水平；术后角膜知觉的下降与术中切削深度间存在正相关。     

Latrogenic keratectasia following laser in situ keratomileusis

PURPOSE: To evaluate keratectasia after laser in situ keratomileusis (LASIK) for high myopia. METHODS: A 49-year-old male patient with myopia of -23.50 D in both eyes underwent LASIK with a Summit Technology Apex Plus excimer laser. A Moria manually-guided MDSC microkeratome was used. Preoperative corneal topography in both eyes did not reveal underlying or fruste form of keratoconus. Four months after LASIK, a progressive keratectasia occurred in right eye and after 12 months, in left eye. Corneal transplantation was performed in both eyes. RESULTS: Histological and ultrastructural examinations were performed on one corneal button. The analysis showed regular stromal morphology and cellularity, with no sign of inflammation. The morphometric analysis showed an overall thickness of 334 microm, with a flap of 262 microm and a stromal residual bed of 72 microm, in the center of the button. CONCLUSION: A LASIK corneal flap made with a planned 120-microm plate turned out histologically to be approximately 260 microm thick, in an eye with a refractive correction of -23.50 D. The excessive flap thickness and excessive ablation produced progressive keratectasia requiring a penetrating keratoplasty.     

准分子激光原位角膜磨镶术中不全角膜瓣后角膜地形图的改变

目的探讨准分子激光原位角膜磨镶术(laser insitu keratomileusis,LASIK)中不全角膜瓣后角膜地形图的变化规律。方法回顾性研究17眼采用hansatome角膜板层刀行LASIK手术的患者,因术中不全角膜瓣而未发射激光的发生情况及不全角膜瓣后Orbscan角膜地形图、视力及屈光度的改变。结果术中不全角膜瓣的发生率为0.29%。不全角膜瓣切削前后视力、屈光度及角膜前后表面曲率均无明显改变(P>0.05)。结论LASIK术中不全角膜瓣的发生不会引起角膜地形图的改变,再次行LASIK并不影响疗效。     

Dry eye after LASIK: Comparison of outcomes for Asian and Caucasian eyes

Background : Dry eye is a common complication of LASIK surgery. Our clinical impression was that post‐LASIK dry eye was more problematic for our Asian patients. The aim of this study was to determine if dry eye after LASIK is more prevalent, more sustained and more severe in Asian eyes compared with Caucasian eyes. Methods : This study was based on a retrospective analysis of a clinical database. Data (n = 932 eyes, 932 patients) was collected before and after (week 2 and months 1, 3 and 6) LASIK surgery. Patients were defined as Asian if both parents were of East Asian ethic origin. Assessments included dry eye symptoms, ocular surface staining, tear volume, tear secretion, tear film stability and corneal sensation. Results : Asian eyes had greater ocular surface staining, poorer tear film stability and lower tear volume before LASIK and at all times after LASIK. Dry eye symptoms occurring ‘often or constantly’ were more prevalent at all time points after LASIK in Asian eyes. Chronic dry eye persisting six months or more after LASIK was diagnosed in 28 per cent of Asian eyes and 5 per cent of Caucasian eyes (p < 0.001). Asian patients with chronic dry eye were predominantly female, reported dry eye symptoms, had greater ocular surface staining and lower tear secretion, stability and volume before surgery. After LASIK, Asian eyes had a slower return to pre‐operative values for ocular surface staining, tear volume and corneal sensation. Discussion : The risk of chronic dry eye after LASIK was significantly higher in Asian eyes. Contributing factors could include racial differences in eyelid and orbital anatomy, tear film parameters and blinking dynamics and higher attempted refractive corrections in Asian eyes.     

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.