Surgical approaches to correct corneal astigmatism at time of cataract surgery: a mini-review

Among refractive errors,astigmatism is the most common optical aberration,where refraction changes in different meridians of the eye.It causes blurred vision at any distance and includes corneal,lenticular,and retinal astigmatism.Cataract surgery used to cause a progressive increase in the pre-exisiting corneal astigmatism because of creating a surgically induced astigmatism,for example,a large size surgery incision.The development of surgical techniques during last decades has made cataract surgery interchange to treat preoperative corneal astigmatism at time of surgery.Nowadays,three surgical approaches can be used.By placing a sutureless clear corneal incision on the steep meridian of the cornea,a preoperative corneal astigmatism less than 1.0 D can be corrected.Single or paired peripheral corneal relaxing incisions(PCRIs)provide 1.0-3.0 D corneal astigmatism correction.PCRIs are typically used for treating 1.0-1.5 D of regular corneal astigmatism,if more than 2.0 D,the risk of overcorrection and irregular astigmatism is increased.When toric intraocular lenses(IOLs)are unavailable in markets,PCRIs are still a reasonable option for patients with up to 3.0 D of pre-existing corneal astigmatism.Toric IOLs implantation can correct 1.0-4.5 D of corneal astigmatism.Several IOLs are approved to correct a high degree of corneal astigmatism with cylinder power up to 12.0 D.These approaches can be used alone or in combination.

Corneal stromal mesenchymal stem cells: reconstructing a bioactive cornea and repairing the corneal limbus and stromal microenvironment

Corneal stroma-derived mesenchymal stem cells(CS-MSCs) are mainly distributed in the anterior part of the corneal stroma near the corneal limbal stem cells(LSCs). CS-MSCs are stem cells with self-renewal and multidirectional differentiation potential. A large amount of data confirmed that CS-MSCs can be induced to differentiate into functional keratocytes in vitro, which is the motive force for maintaining corneal transparency and producing a normal corneal stroma. CS-MSCs are also an important component of the limbal microenvironment. Furthermore, they are of great significance in the reconstruction of ocular surface tissue and tissue engineering for active biocornea construction. In this paper, the localization and biological characteristics of CS-MSCs, the use of CS-MSCs to reconstruct a tissue-engineered active biocornea, and the repair of the limbal and matrix microenvironment by CS-MSCs are reviewed, and their application prospects are discussed.

Corneal neuromediator profiles following laser refractive surgery

Laser refractive surgery is one of the most commonly performed procedures worldwide.In laser refractive surgery,Femtosecond Laser in Situ Keratomileusis and Refractive Lenticule Extraction have emerged as promising alternatives to microkeratome Laser in Situ Keratomileusis and Photorefractive Keratectomy.Following laser refractive surgery,the corneal nerves,epithelial and stromal cells release neuromediators,including neurotrophins,neuropeptides and neurotransmitters.Notably,nerve growth factor,substance P,calcitonin gene-related peptide and various cytokines are important mediators of neurogenic inflammation and corneal nerve regeneration.Alterations in neuromediator profiles and ocular surface parameters following laser refractive surgery are attributed to the surgical techniques and the severity of tissue insult induced.In this review,we will discuss the(1)Functions of neuromediators and their physiological and clinical significance;(2)Changes in the neuromediators following various laser refractive surgeries;(3)Correlation between neuromediators,ocular surface health and corneal nerve status;and(4)Future directions,including the use of neuromediators as potential biomarkers for ocular surface health following laser refractive surgery,and as adjuncts to aid in corneal regeneration after laser refractive surgery.

Progress of corneal collagen cross-linking combined with refractive surgery

As a photochemical reaction that can stiffen the cornea,corneal collagen cross-linking(CXL) is the only promising method of preventing the progress of keratectasia,such as keratoconus and secondary ectasia following refractive surgery. The aim of CXL is to stabilize the underlying condition,with a small chance of visual improvement. Combining CXL with refractive surgery targeting both stabilization and reshaping of the corneal tissue for visual function improvement is a good treatment option. This review aims to provide a comprehensive and unbiased summary of the published research regarding combined CXL and refractive surgery,including measures and results,to help elucidate the future direction of CXL.

Double intrastromal corneal ring segment implantation: a new approach for improved clinical outcomes in keratoconus patients

AIM:To evaluate the clinical outcomes after subsequent implantation of a new intrastromal corneal ring segment(ICRS)model followed by an additional short-arc ICRS implant in keratoconus patients.METHODS:This retrospective single-arm cohort study evaluated 25 eyes of 21 keratoconus patients implanted with the new ICRS followed by 140-arch length ICRS(140-ICRS)implantation.Uncorrected distance visual acuity(UDVA,logMAR),corrected distance visual acuity(CDVA,logMAR),sphere,astigmatism,keratometry,spherical equivalent(SE),and asphericity were compared preoperatively and postoperatively after both ICRS implantation.RESULTS:The average follow-up time after 140-ICRS implantation was 6.40±2.20mo.The mean preoperative UDVA improved from 1.27±0.14 preoperative to 0.52±0.26 after both ICRS implantation(P=0.03).The mean sphere value reduced from-5.34±2.74 preoperatively to-2.06±1.84 postoperatively(P<0.001)after the first ICRS implantation and decreased to-0.59±1.54 postoperatively(P<0.001)after 140-ICRS implantation.The mean preoperative astigmatism was-3.72±1.56 and improved to-2.82±1.08 after the first ICRS implantation,and following the 140-ICRS implantation,the mean astigmatism was-1.37±0.67(P=0.001).The SE and asphericity changes were statistically significant(P<0.001).The researchers did not find intraoperative or postoperative complications for both procedures.CONCLUSION:The combination of 2 different ICRSs can efficiently regularize the cornea,reduce the SE,and improve visual acuity in selected keratoconus patients.

The Limbal Niche and Its Role in Maintaining Corneal Regeneration

In recent years, stem cells have been a focal point in research designed to evaluate the efficacy of ophthalmologic therapies, specifically those for corneal conditions. The corneal epithelium is one of the few regions of the body that maintains itself using a residual stem cell population within the adjacent limbus. Stem cell movement has additionally captivated the minds of researchers due to its potential application in different body regions. The cornea is a viable model for varying methods to track stem cell migratory patterns, such as lineage tracing and live imaging from the limbus. These developments have the potential to pave the way for future therapies designed to ensure the continuous regeneration of the corneal epithelium following injury via the limbal stem cell niche. This literature review aims to analyze the various methods of imaging used to understand the limbal stem cell niche and possible future directions that might be useful to consider for the better treatment and prevention of disorders of the cornea and corneal epithelium. .

Observation of Long-term Efficacy of Corneal Limbal Conjunctival Autografts in Microscopy Treatments of Pterygium

Purpose: To compare the long-term efficacy of a corneal limbal conjunctival autograft combined with pterygium excision in the treatment of primary pterygium. Methods: This random control study included 63 patients (63 eyes) with primary pterygium. These were randomly divided into a group with corneal limbal conjunctival autograft combined with pterygium excision (group A) and a group with pterygium excision with exposed sclera (group B) and subjected to long-term follow up. The surgical outcomes were classified and evaluated (grade Ⅰ-Ⅳ). Several indexes were analyzed, including ocular surface irritation symptom,tear film stability, surgical complication, and recurrence rate. Results: The follow up ranged from 24 to 38 months, (26.9± 3.4) months on average. No recurrence was noted at 6 weeks postoperatively. At 6 months postoperatively, the recurrence rate of pterygium was 5.2% in group A and 8.0% in group B. At 1 year postoperatively, the recurrence rate in group A was 10.5% and 20.0% in group B. At the end of follow up, the recurrence rates were 13.1% in group A and 24.0% in group B. No statistical significance was found between two groups regarding the recurrence rates at each time point (P>0.05). After the follow up. (> 2 years),the severity of ocular surface conditions was significantly milder in patients in group A than in group B (P <0.01).No statistically significant differences were noted between the two groups at 6 weeks,6 months, and 1 year after surgery. No statistically significant differences were observed between the two groups regarding postoperative tear film break-up time. Fewer postoperative complications and milder ocular surface irritation symptoms occurred in patients in group A. Conclusion: Corneal limbal conjunctival autograft combined with pterygium excision yields sound long-term efficacy and a low recurrence rate and induces only mild damage on the ocular surface when used as a treatment for pterygium.

Clinicopathological Analysis of 39 Patients with Corneal Tumors

Purpose:Corneal tumors are rarely seen in clinical practice.There is a paucity of data on the incidence of various corneal tumors,their clinical and pathological features and surgical management,especially on large patient samples.Methods:The medical records of 39 patients with corneal tumors referred to Zhongshan Ophthalmic Center,Sun Yat-sen University,China from January 1,1996 to December 31,2002 were reviewed retrospectively.Results:Of the 39 cases with corneal tumors,31 were males and 8 were females.The right eye was affected in 24 cases and the left one in 15 cases.The mean age at diagnosis was 45.7 years,ranged from 3 to 88 years.Squamous cell carcinoma was the most common tumor in the cornea(18 cases,46.15%),followed by pigmented naevus.(12 cases,30.77%),papillary epithelioma(3 cases,7.69%),melanoma(1 case,2.56%),oncosis hyperplasia(1 case,2.56%),inverting papilloma.(1 case,2.56%),primary acquired melanosis(1 case,2.56%),amyloid degeneration(1 case,2.56%),inflammatory pseudotumor(1 case,2.56%).They arose most commonly in the limbal region.All tumors were unilaterally involved.Squamous cell carcinoma of the cornea usually appears as a whitish,rough,irregular lesion or a telangiectatic,gelatinous epibulbar mass.Nevus in the cornea generally becomes clinically apparent in the first or second decade of life and the lesion may enlarge or more deeply pigmented afterwards.The corneal tumors were completely excised microsurgically in 22 cases.Six cases were treated with surgical resection combined with amniotic membrane graft.Three cases with surgical excision plus transfer of conjunctival flap.Two cases with surgical excision plus lamellar keratoplasty.Two cases with surgical excision plus cryosurgery.Two cases with orbital exenteration.One case with enuleation.One case with incision biopsy and observation.Conclusion:Squamous cell carcinoma and nevus,the most common corneal tumors,accounted for 76.92% of all cases.The therapeutic outcomes depended upon early pathologic diagnosis and early surgical management.

Laser vision correction for patients with atypical topography of cornea, LASIK vs. PRK: A review

Purpose: To search evidence and determine whether PRK (Photo Refractive Keratectomy) or LASIK (Laser in Situ Keratomileusis) produce a better outcome of laser vision correction for patients with atypical topography of cornea. Setting: Electronic search of laser vision correction related studies on Cochrane Library, Medline and PubMed. Method: The search was conducted over Cochrane Library, Embase, PubMed and Medline using the key words of refractive laser surgery, PRK, LASIK, Atypical topography, cornea ectasia and Keratoconus from 1980 to 2012. Boolean operators were used to search in electronic data bases of related studies. The combining words used here were And, OR. Result: The best corrected vision decreased for those eyes with atypical topography that were treated with either PRK or LASIK. However, in the comparison of the outcomes of vision and ectasia, PRK outperformed LASIK. Conclusion: There is possible risk of developing corneal ectasia in those patients who desire laser vision correction with atypical topographic cornea. PRK may be a safer procedure when compare to LASIK for those patients.

角巩膜缘与角膜切口超声乳化术治疗老年白内障疗效对比

目的 对比角巩膜缘与角膜切口超声乳化术治疗老年白内障的临床疗效。方法 随机将80例老年白内障患者分为2组。2组均行超声乳化术,对照组采用角膜切口,观察组采用角巩膜缘切口。比较2组上皮修复时间、切口修复时间、裸眼视力、最佳矫正视力(BCVA)、角膜散光度、手术源性角膜散光度、泪囊破裂时间(BUT)、角膜荧光素染色评分(FLCs)、泪液分泌试验(SIt)水平以及术后并发症发生率。结果 观察组上皮修复、切口修复时间均早于对照组(P<0.05);观察组术后1周、2周、4周时裸眼视力、BCVA水平以及BUT、Sit水平均高于对照组(P<0.05);观察组术后1周、2周、4周时角膜散光度、手术源性角膜散光度以及FLCs水平水平均低于对照组(P<0.05);2组术后并发症发生率(18%与12%)差异无统计学意义(P>0.05)。结论 角巩膜缘切口超声乳化术治疗老年白内障临床疗效较好,患者术后角膜散光度较低,且视力、泪膜功能稳定性恢复较好。

角膜屈光术后角膜上皮重塑及其影响因素

角膜上皮作为重要的屈光介质,参与了屈光术后角膜修复的过程,现有的角膜屈光术后均表现为角膜上皮重塑,过度的角膜上皮重塑影响了角膜屈光手术的矫正效果。文章一方面总结了角膜上皮重塑在屈光手术中的应用,另一方面更加全面地探究了围手术期角膜屈光术后上皮重塑的影响因素,以期提高角膜屈光手术的安全性、有效性、可预测性和稳定性。

An interferometric ex vivo study of corneal biomechanics under physiologically representative loading,highlighting the role of the limbus in pressure compensation

Background:The mechanical properties of the cornea are complex and regionally variable.This paper uses an original method to investigate the biomechanics of the cornea in response to hydrostatic loading over the typical physiological range of intraocular pressure(IOP)fluctuations thereby increasing understanding of clinically relevant corneal biomechanical properties and their contributions to the refractive properties of the cornea.Methods:Displacement speckle pattern interferometry(DSPl)was used to measure the total surface displacement of 40 porcine and 6 human corneal-scleral specimens in response to pressure variations up to 1 mmHg from a baseline of 16.5 mmHg.All specimens were mounted in a modified artificial anterior chamber(AAC)and loaded hydrostatically.Areas of high strain in response to loading were identified by comparing the displacements across different regions.Results:The nature of the response of the corneal surface to loading demonstrated high regional topographic variation.Mechanical properties were shown to be asymmetrical,and deformation of the limbal and pre-limbal regions dominated these responses respectively with over 90%(nasal-temporal)and 60%(superior-inferior)of the total maximum displacement occurring in these regions indicating high strain.In contrast,the curvature of the central cornea remained relatively unchanged merely translating in position.Conclusions:The limbal and pre-limbal regions of the cornea appear to be fundamental to the absorption of small pressure fluctuations facilitating the curvature of the central cornea to remain relatively unchanged.The differential mechanical properties of this region could have important implications for the application of corneal surgery and corneal crosslinking,warranting further investigation.

An interferometric ex vivo study of corneal biomechanics under physiologically representative loading,highlighting the role of the limbus in pressure compensation

Background:The mechanical properties of the cornea are complex and regionally variable.This paper uses an original method to investigate the biomechanics of the cornea in response to hydrostatic loading over the typical physiological range of intra-ocular pressure(IOP)fluctuations thereby increasing understanding of clinically relevant corneal biomechanical properties and their contributions to the refractive properties of the cornea.Methods:Displacement speckle pattern interferometry(DSPI)was used to measure the total surface displacement of 40 porcine and 6 human corneal-scleral specimens in response to pressure variations up to 1 mmHg from a baseline of 16.5 mmHg.All specimens were mounted in a modified artificial anterior chamber(AAC)and loaded hydrostatically.Areas of high strain in response to loading were identified by comparing the displacements across different regions.Results:The nature of the response of the corneal surface to loading demonstrated high regional topographic variation.Mechanical properties were shown to be asymmetrical,and deformation of the limbal and pre-limbal regions dominated these responses respectively with over 90%(N-T)and 60%(S-I)of the total maximum displacement occurring in these regions indicating high-strain.In contrast,the curvature of the central cornea remained relatively unchanged merely translating in position.Conclusions:The limbal and pre-limbal regions of the cornea appear to be fundamental to the absorption of small pressure fluctuations facilitating the curvature of the central cornea to remain relatively unchanged.The differential mechanical properties of this region could have important implications for the application of corneal surgery and corneal crosslinking,warranting further investigation.

自体角膜缘干细胞移植与常规翼状胬肉切除术疗效比较

目的通过翼状胬肉单纯切除术及翼状胬肉切除加自体角膜缘干细胞移植术2种手术方式治疗翼状胬肉,比较其治愈及复发情况及角膜上皮修复时间,评价其疗效。方法将86例(88眼)翼状胬肉患者随机分为翼状胬肉单纯切除术组(A组)43例44眼及翼状胬肉切除加自体角膜缘干细胞移植术组(B组)43例44眼,组间比较采用χ2检验比较其疗效。结果A组10例10眼复发,B组仅有1例1眼复发,2组比较差异有统计学意义(P<0.05);A组角膜上皮修复时间平均为(5.15±0.92)d,B组角膜上皮修复时间平均为(3.36±0.82)d,2组比较差异有统计学意义(P<0.05)。结论翼状胬肉切除加自体角膜缘干细胞移植术可以降低复发率,缩短角膜上皮修复时间,是治疗翼状胬肉较为安全有效的方法。

不同类型青光眼患者手术前后角膜生物力学变化特征

目的比较不同类型青光眼患者角膜生物力学差异及其相关影响因素,探讨青光眼术后角膜生物力学的变化趋势。方法采用前瞻性病例对照研究。收集2017年1—7月天津市眼科医院收治的急性原发性闭角型青光眼(APACG)(缓解期或慢性期)患者61例61眼、慢性原发性闭角型青光眼(CPACG)患者94例94眼、原发性开角型青光眼(POAG)患者70例70眼和年龄相关性白内障(ARC)患者64例64眼。采用Corvis ST测量活体角膜的生物力学参数,分析并比较不同类型青光眼患者术前角膜生物力学参数差异以及青光眼手术后的变化,采用多重线性回归分析探讨年龄、矫正后眼压(IOPcc)、中央角膜厚度(CCT)、眼轴长度(AL)、平均角膜屈光力(K)与角膜生物力学参数的关系。结果与ARC组相比,术前CPACG组和POAG组第一压平速度(A1V)、第二压平时间(A2T)较小,差异均有统计学意义(均P<0.05);与ARC组和APACG组相比,术前CPACG组和POAG组第二压平速度(A2V)较大,差异均有统计学意义(均P<0.05)。A1V、A2T、角膜顶点改变的最大垂直距离(DA)及最大压陷时角膜表面未发生改变的两点距离(PD)与IOPcc均呈负相关(r=-0.494、-0.612、-0.652、-0.277,均P<0.05),A2V、第一压平时间(A1T)及最大压陷曲率半径(CCR)与IOPcc均呈正相关(r=0.508、0.960、0.249,均P<0.05);第一压平长度(A1L)及第二压平长度(A2L)与K均呈负相关(r=-0.323、-0.227,均P<0.05),A1V、A2T及DA与K均呈正相关(r=0.214、0.256、0.242,均P<0.05)。与术前相比,CPACG组术后1个月A1T、A2V减小,A1V、A2T、DA增大,差异均有统计学意义(均P<0.05);POAG组术后1个月A1T、A2V减小,A2T、DA增大,差异均有统计学意义(均P<0.05)。与术前相比,APACG组、ARC组术后1个月角膜生物力学指标差异无统计学意义(均P>0.05)。结论CPACG和POAG患眼角膜形变能力较差,青光眼手术后角膜形变能力逐渐恢复;APACG(缓解期或慢性期)由于眼压一过性升高,对角膜形变能力影响较小,手术前后无明显差异;角膜生物力学各参数受IOPcc和K值影响较大。

翼状胬肉角膜缘干细胞移植与羊膜移植的比较

目的:对比观察翼状胬肉切除加自体角膜缘干细胞移植术(PECT)或加羊膜移植术这2种方法治疗翼状胬肉的效果。方法:翼状胬肉91例分为胬肉切除加自体角膜缘干细胞移植术24例,胬肉切除加羊膜移植术67例。术后随访3a,比较2组的恢复情况及复发倾向。结果:胬肉切除角膜缘加干细胞移植术后仅5例术眼有异物感或不适,无任何复发倾向。而羊膜移植术后有18例术眼有异物感或不适,15例眼睑轻度水肿及结膜充血水肿,且2例有复发倾向,无1例睑球粘连。结论:翼状胬肉切除加自体角膜缘干细胞移植术或加羊膜移植术均为治疗翼状胬肉的可靠方法,但以前者更佳。

正常角膜缘组织中与血管生成相关的生长因子及其受体的表达

目的探查正常人角膜缘组织里与血管生成相关的生长因子及其受体的分布。方法用冰冻切片和链亲合素过氧化物酶染色系统，选择一组兔抗人多克隆抗体，即：血管内皮生长因子（ＶＥＧＦ）、碱性成纤维细胞生长因子（ｂＦＧＦ）、血小板源性生长因子（ＰＤＧＦ－Ａ）和转化生长因子－β １（ＴＧＦ－β １）及其受体对１１例角膜移植供体材料的角膜缘组织进行了检查。结果ＶＥＧＦ，ｂＦＧＦ，ＰＤＧＦ－Ａ和ＴＧＦ－β １ ４种生长因子仅在１或２例标本中不表达外，在大部分标本中表达阳性。４种生长因子的受体在角膜缘上皮、基底膜、上皮下组织和角巩膜组织内阳性表达分别是：ＶＥＧＦ ９例、７例、１０例和８例；ｂＦＧＦ ８例、９例、９例和８例；ＰＤＧＦ ５例、４例、１０例和７例；ＴＧＦ－β １３例、０例、１１例和６例。结论在正常角膜缘组织中，存在ＶＥＧＦ，ｂＦＧＦ，ＰＤＧＦ－Ａ和ＴＧＦ－β １及其受体，可能在维持正常的角膜功能和调节角膜缘组织的生长和增殖中起着重要作用。

HLA匹配角膜缘干细胞联合羊膜移植修复翼状胬肉

背景:HLA匹配的角膜缘干细胞联合羊膜移植治疗翼状胬肉是眼科医生治疗的新理念,该方法治疗后并发症少、康复快、复发率低,尤其是能减少移植排斥反应等已被广泛接受。目的:探讨HLA匹配的角膜缘干细胞联合羊膜移植治疗翼状胬肉疗效。方法:选取2013年3月1日至2014年4月30日行HLA匹配的角膜缘干细胞联合羊膜移植治疗的翼状胬肉患者47例(47眼)作为试验组;回顾性分析2010年3月1日至2012年12月1日采用单纯翼状胬肉切除方法治疗的翼状胬肉患者40例(47眼)作为对照组,对两组患者治愈和复发情况进行比较。结果与结论:试验组47例,全部顺利完成治疗,无并发症,其中1例切口感染,特殊对症治疗后均已好转出院,全部患者均无移植排斥反应。试验组治愈45眼,复发2眼,复发率为4.3%。对照组47眼中治愈32眼,复发15眼,复发率31.9%。结果表明HLA匹配的角膜缘干细胞联合羊膜移植治疗翼状胬肉并发症少、复发率低,是治疗翼状胬肉一种行之有效的方法。

飞秒激光与常规刀片准分子激光术后角膜后表面高度早期变化的对照研究

背景 飞秒激光准分子激光角膜原位磨镶术（FS-LASIK）已广泛用于屈光不正的矫治,具有良好的安全性和可预测性,但缺乏术后角膜后表面高度动态变化的研究.了解FS-LASIK术后角膜后表面高度的动态变化对于预防医源性角膜膨隆具有重要意义. 目的 分析FS-LASIK术后早期角膜后表面高度的变化情况,并与前弹力层下准分子激光角膜磨镶术（SBK）、上皮刀辅助的准分子激光上皮瓣下角膜磨镶术（Epi-LASIK）术后情况进行比较.方法 采用前瞻性非随机对照研究设计.纳入2010年6-9月在天津市眼科医院行准分子激光角膜屈光手术的近视及近视散光患者72例144眼,分为FS-LASIK组23例46眼,SBK组28例56眼,Epi-LASIK组21例42眼.分别于术前及术后1d（Epi-LASIK组术后3d）、1周、1个月用Visante OMNI测量术眼角膜后表面水平子午线和垂直子午线上角膜顶点及距离角膜顶点1、2、3 mm共13个点的角膜后表面高度,采用重复测量的方差分析进行统计学分析. 结果 在FS-LASIK组,术前、术后1d、1周、1个月术眼角膜顶点方位角膜后表面高度分别为（2.03±0.78）、（2.26±0.96）、（2.16±0.85）和（2.06±0.89）μm；在距角膜顶点1 mm、2 mm区域,术眼的术后变化趋势与角膜顶点区域的变化相同；在距角膜顶点3 mm区域,上述4个时间点术眼的角膜后表面高度分别为（-4.64±1.68）、（-5.39±1.85）、（-4.73±1.71）和（-4.71±1.52） μm.在SBK组,术前及术后1d、1周、1个月角膜顶点区域角膜后表面高度分别为（1.44±0.63）、（1.74±0.75）、（1.66±0.69）和（1.53±0.71） μm；在距角膜顶点1 mm、2 mm区域,术眼术后角膜后表面高度变化趋势与角膜顶点区域一致；在距角膜顶点3 mm区域,上述4个时间点角膜后表面高度分别为（-5.09±1.76）、（-5.48±1.68）、（-5.27±1.81）和（-5.19±1.77）μm,术后发生了轻微后移.在Epi-LASIK组,术前,术后3d、1周、1个月在角膜顶点区角膜后表面高度分别为（2.47±0.73）、（1.55±1.43）、（1.55±1.37）和（2.37±1.06） μm,术后发生轻微后移；而在距角膜顶点1 mm、2 mm区域则与角膜顶点术后变化趋势不同,术后3d角膜后表面高度分别由术前的（1.55±0.51）μm、（-1.87±0.91）μm变为（1.92±0.91） μm、（0.24±1.35） μm,角膜发生轻微前移.在距角膜顶点3 mm区域,角膜后表面高度变化趋势与角膜顶点区相同.FS-LASIK组和SBK组术眼术后角膜后表面高度的变化较小,Epi-LASIK术后1d、1周时较术前变化较大.术后1d时,FS-LASIK相对于SBK变化较大.不同的手术方式及不同时间点角膜后表面高度的差异均无统计学意义（P＞0.05）.结论 FS-LASIK术后早期中央区和旁中央区的角膜后表面高度发生了微小的变化,但随时间的变化逐渐恢复至术前水平,与SBK、Epi-LASIK相比无明显差异.

近视眼角膜Q值的临床意义

目的:研究角膜的非球面参数Q值在不同程度近视眼中的分布情况。方法:53例106只近视眼,按照低、中、高度近视程度分为3组,用Astramax角膜分析仪测定角膜Q值并做统计学处理。结果:平均角膜Q值3组分别为-0.34±0.24,-0.21±0.24和-0.22±0.20。3组之间无统计学显著性差异(P=0.18)。结论:角膜非球面参数Q值与近视程度无关,个体间变异较大。准分子激光屈光手术中不应采用人群的角膜Q值平均值,而应当针对个体角膜的Q值进行修正,即所谓个性化治疗。