Effect of topical 0.05% cyclosporine A on corneal endothelium in patients with dry eye disease

· AIM: To determine the effect of topical 0.05% cyclosporine A (CsA) on corneal endothelium in patients with dry eye disease. · METHODS: Observational, prospective, case series study. Fifty-five eyes of 29 consecutive patients (9 males and 20 females; median age: 66.8 years, interquartile range: 61 -73.2 years) with moderate -severe dry eye disease were evaluated. All patients were treated with topical 0.05% CsA ophthalmic emulsion twice a day in addition to lubricant eyedrops 5 times a day. The follow- up period was 12 months. Before treatment and at 3 and 12 months post -treatment central corneal specular microscopy was performed. The endothelial cell density (ECD), coefficient of variation of cell size (CoV), and percentage of hexagonal cells (Hex %) were analyzed. ·RESULTS: The median ECDs pre-treatment and at 3 and 12 months post-treatment were 2 352.5/mm 2 (inter- quartile range, 2 178 -2548.5), 2 364/mm 2 (interquartile range, 2 174.25 -2 657.5), and 2 366 cells/mm 2 (inter - quartile range, 2 174.75-2 539.75), respectively (P=0.927, one way ANOVA). The median CoVs pre-treatment and at 3 and 12 months post -treatment were 34.5 (interquartile range, 30 -37), 35 (interquartile range, 30 -38), and 34 (interquartile range, 30.75-38.25), respectively (P=0.7193, one way ANOVA). The median Hex % values pre - treatment and at 3 and 12 months post -treatment were 53 (interquartile range, 47 -58), 54 (interquartile range, 45.75 -59), and 50.5 (interquartile range, 45.75 -58), respectively (P=0.824, one way ANOVA). · CONCLUSION: Treatment of patients with dry eye disease for 12 months with topical 0.05% CsA does not seem to cause substantial changes on corneal endothelium.

Differences in energy and corneal endothelium between femtosecond laser-assisted and conventional cataract surgeries：prospective,intraindividual,randomized controlled trial

AIM： To compare intraoperative phacoemulsification parameters and its effect on the corneal endothelium of eyes undergoing femtosecond laser-assisted cataract surgery（FLACS） versus conventional phacoemulsification（CP） cataract surgery.METHODS： Two hundred eyes from one hundred patients were included in a prospective, non-blinded, randomized, controlled, intraindividual clinical study. One hundred eyes underwent FLACS while their one hundred fellow eyes underwent CP. All surgeries were performed using the Victus？ femtosecond laser platform and Infinity？ Vision System phacoemulsification machine. Primary outcome measure was endothelial cell density 6 mo after surgery. Secondary outcome measures included central corneal thickness（CCT）, average cell area, standard deviation, coefficient of variation and hexagonality before surgery and 6 mo after surgery and endothelial cell density loss during this period were also evaluated. Intraoperative efficiency parameters [cumulative dissipated energy（CDE）, total intraocular surgery time, total ultrasound time, total phacoemulsification time, total torsional energy time, total aspiration time, ultrasound energy, torsional amplitude and fluid required during surgery] were also collated. RESULTS： Data from these patients was not considered for analysis. Data from 92 patients were analysed. Postoperative endothelial cell density（cells/mm2） between groups（2211.88±392.49 CP; 2246.31±403.48 FLACS） was not statistically significant（P=0.869）. Total ultrasound time, torsional energy time, CDE and fluid requirements were significantly lower the FLACS group（P〈0.05）. Other parameters did not show statistically significant difference between FLACS and CP.CONCLUSION： FLACS displays significant improvements in phacoemulsification parameters in comparison to CP. There are no significant differences in corneal endothelium measures between FLACS and CP.

STUDY IN CYTOTOXICITY OF GENTAMYCIN TO CORNEAL EPITHELIUM AND ENDOTHELIUM IN TISSUE CULTURE

A study in cytotoxicity of gentamyein to tissue-cultured bovine corneal endothelial cells and rabbit corneal epithelial cells is reported. When the cultured cells reached confluence, they were exposed to tissue culture media containing gentamycin for 6 hours. We founl that 0.5% gentamycin caused significant damage to corneal epithelial cells---diffuse plasmolysis, with scattered cell necrosis and 5% loss.While corneal endothelial cells were exposed to 1.6 mg/ml gentamycin, extensive cell loss (approximate- ly 15%) was observed. The damaged cells recovered their normal morphology after 24 hours. When the concentration of gentamycin increased twice, serious damage to cells occured. The area of cell loss reached 40%, and the recovery of cellular morphology Was much slower. This study demonstrates that gentamycin potential cytotoxicity to corneal epithelium and endothelium, suggesting that gentamycin should be rationally used in the treatment of ocular diseases.

EXPERIMENTAL STUDY ON THE CORNEAL ENDOTHELIUM OF TRAUMATIC CATARACT

The cell morphology of corneal endothelium in 84 mice with experimental traumatic cataract was investigated with stained corneal buttons. In the experimental group, the boundaries between adjacent corneal endothelial cells were significantly distorted, some cell boundaries manifested degenerative changes that led to coalescence of the cells. The mean density and mean area of endothelial cells of the controls showed significant difference from those of the experimental group during the 12 weeks of observ...

Hammered silver appearance of the corneal endothelium in Fuchs uveitis syndrome:A case report

BACKGROUND Hammered silver appearance of the corneal endothelium is considered a characteristic change in iridocorneal-endothelial syndrome.Herein we report an interesting case of hammered silver appearance of the corneal endothelium in Fuchs uveitis syndrome(FUS).CASE SUMMARY A 49-year-old man with progressive vision loss in the right eye for one year was admitted to our hospital.The clinical manifestations of the patient’s right eye were mild conjunctival hyperemia,scattered stellate keratic precipitates on the corneal endothelium,normal depth anterior chamber,2+cellular reaction in the aqueous humor,diffuse iris depigmentation,absence of synechia,Koeppe nodules,opalescent lens,and vitreous opacity.FUS and a complicated cataract were diagnosed based on the typical clinical manifestations.The corneal endothelial changes were recorded in detail by slit-lamp examination,specular microscopy,and in vivo confocal microscopy before cataract extraction,revealing a hammered silver appearance of the corneal endothelium in the affected eye,a wide-band dark area,as well as irregular corneal endothelial protuberances and dark bodies of various sizes.Subsequently,the patient underwent phacoemulsification combined with intraocular lens implantation,and his postoperative visual acuity recovered to 1.0.CONCLUSION Hammered silver appearance of the corneal endothelium in FUS,which is considered a more serious manifestation of endothelial damage,is rare and may be caused by many irregular protrusions in the corneal endothelium.

Short term effects of small incision lenticule extraction surgery on corneal endothelium

AIM： To assess the effects of small incision lenticule extraction（SMILE） surgery on the corneal endothelium at1 d to 1mo postoperatively.·METHODS： A retrospective, observational study was conducted on 47 patients（47 eyes） who received SMILE surgery. Patients were grouped according to contact lens wear condition. The corneal endothelium was examined preoperatively and at 1d, 1wk and 1mo postoperatively.The corneal endothelium was analyzed for endothelial cell density（ECD）, percentage of hexagonal cells, and coefficient of variation（CV） of cell size.·RESULTS： There were no significant decrease in the ECD, percentage of hexagonal cells or increase in CV at1 d, 1wk and 1mo postoperatively（P 〉0.05）. However,there was a small increase of ECD by 2.88% in contact lens wearers（78.26±113.62 cell/mm2, P 〈0.05）.· CONCLUSION： SMILE has no significant adverse effects on the corneal ECD and morphology during 1mo follow-up time.

Evaluation of corneal endothelium after UVA/riboflavin cross-linking in thin keratoconic corneas

Dear Sir,UVA/riboflavin cross-linking （CXL） has been used clinically applied for the treatment of keratoconus and corneal edema via enhancement of corneal stiffness The safety of the corneal endothelium is of prime importance during CXL treatment. In clinical practice, a corneal thickness （CT） of 400um has traditionally been regarded as the minimum treatable thickness, thereby avoiding damage to the corneal endothelium Although CXL has been applied to thinner corneas, using a hypoosmotic solution onto cornea and inducing edema . CXL safety still needs further evaluation because of lower relative concentration of collagen in the hydrated stroma . This study aims to evaluate the changes of corneal endothelial density （ECD） in cases where the CT is 〈400 um before iatrogenic corneal swelling and CXL treatment.

AB086.Influence of the intraocular pressure on the expression of tight junctions in the corneal endothelium

Background:Cells are influenced by their environment.In vivo,the corneal endothelium is subjected to intraocular pressure(IOP).The purpose of this project was to evaluate in vitro,the effect of the IOP on the formation of tight junctions in the corneal endothelium.Methods:Cultivated corneal endothelial cells(P2-P3;n=6 populations)were seeded on devitalized on corneas(n=10 pairs).Native corneas and devitalized corneas were respectively used as positive(n=2 pairs)and negative controls(n=3 pairs).Corneas were placed in artificial anterior chambers and subjected to a hydrostatic pressure between 0.3 and 0.4 psi during 4-5 days.Unpressured control corneas were maintained in cell culture dishes.Pictures of the corneas were taken following the experiment to assess stromal transparency.Morphology,corneal thickness and distribution of ZO-1,n-cadherin,b-catenin,NaK ATPase pump and HCO3-cotransporter were evaluated by electron microscopy,histological staining and immunofluorescences.Results:Pressure treated corneas were more transparent than the controls.Thickness was accordingly reduced by 38.4%±4.9%for cultivated endothelium and 32.2%±2.7%for native endothelium.Negative controls change in transparency and thickness were marginal.Pressure treated cells showed none or at most marginal difference in morphology and expression of ZO-1,n-cadherin,b-catenin,NaK ATPase pump and HCO3-cotransporters and failed to recreate a phenotype similar to native corneas.Pressure however increased cortical localisation of the protein ZO-1 in both cultivated and native endothelium.Conclusions:These results suggest that anterior chamber hydrostatic pressure may enhance endothelial functionality by modulating the distribution of tight junction’s proteins.

The role of corneal endothelium in macular corneal dystrophy development and recurrence

Macular corneal dystrophy(MCD)is a progressive,bilateral stromal dystrophic disease that arises from mutations in carbohydrate sulfotransferase 6(CHST6).Corneal transplantation is the ultimate therapeutic solution for MCD patients.Unfortunately,postoperative recurrence remains a significant challenge.We conducted a retrospective review of a clinical cohort comprising 102 MCD patients with 124 eyes that underwent either penetrating keratoplasty(PKP)or deep anterior lamellar keratoplasty(DALK).Our results revealed that the recurrence rate was nearly three times higher in the DALK group(39.13%,9/23 eyes)compared with the PKP group(10.89%,11/101 eyes),suggesting that surgical replacement of the corneal endothelium for treating MCD is advisable to prevent postoperative recurrence.Our experimental data confirmed the robust m RNA and protein expression of CHST6 in human corneal endothelium and the rodent homolog CHST5 in mouse endothelium.Selective knockdown of wild-type Chst5 in mouse corneal endothelium(AC^(siChst5)),but not in the corneal stroma,induced experimental MCD with similar extracellular matrix synthesis impairments and corneal thinning as observed in MCD patients.Mice carrying Chst5 point mutation also recapitulated clinical phenotypes of MCD,along with corneal endothelial abnormalities.Intracameral injection of wild-type Chst5 rescued the corneal impairments in AC^(siChst5)mice and retarded the disease progression in Chst5 mutant mice.Overall,our study provides new mechanistic insights and therapeutic approaches for MCD treatment by highlighting the role of corneal endothelium in MCD development.

Covering corneal stromal lenticule for macular hole in pathological myopia

AIM:To evaluate the clinical effect of a new surgery technique(covering corneal stromal lenticule,CSL)for macular hole(MH)in pathological myopia.METHODS:This was a prospective non-randomized series case study.Fourteen eyes of 14 patients whose axial length were more than 29 mm and suffered from MH and macular hole retinal detachment(MHRD)were included in this study.All cases were treated with 25-gauge pars plana vitrectomy(PPV)with internal limiting membrane(ILM)peeling,covering CSL and C_(3)F_(8) gas tamponade.These cases were followed for 6mo,and the best-corrected visual acuity(BCVA),healing status of MH,the reattached rate of retinal detachment(RD),and reoperation rate were analyzed.RESULTS:All cases were successfully performed the surgery and the postoperative follow-up was completed.After surgery,MHs were healed in all 14 eyes(100%,14/14)after assessed by optical coherence tomography.The reattachment of retina was achieved in all 6 eyes(100%,6/6)with MHRD.BCVA was improved in 12 eyes(85.71%,12/14),and had no significant change in 2 eyes(14.29%,2/14).The overall mean BCVA was improved from 1.80±0.77 to 0.82±0.46 logMAR(F=10.46,P<0.01).No serious complications occurred in all cases.CONCLUSION:The new surgery technique(covering CSL)has high reattached rate of RD and high healing rate of MH in pathological myopia in the preliminary study.And it can effectively improve the visual function of patients.This new technique offers meaningful new ideas for treating refractory MH in pathological myopia.

Effect of mitomycin C on the corneal endothelial cells of Saudi patients with myopia after transepithelial photorefractive keratectomy:a two-armed cohort study

AIM:To study the effect of mitomycin C(MMC)applied during transepithelial photorefractive keratectomy(TPRK)on the corneal endothelium one week(W1)and three months(M3)after surgery and its determinants.METHODS:In this two-armed cohort study conducted in 2022,eyes treated with MMC during TPRK(group 1)were compared with eyes not treated with MMC(group 2).The corneal endothelial cell(EC)count,EC density(ECD;cells/mm2),average(μm2),standard deviation(μm2),coefficient of variation(CV%),ECmax,ECmin,and EC percentage of hexagonality were estimated at W1 and M3.The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables.RESULTS:Group 1 had 26 eyes,and group 2 had 78 eyes.All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2.The MMC usage was not a significant predictor of the change in ECD(P=0.644),change in CV(P=0.374),and change in the percentage of hexagonality of EC(P=0.164)at W1.However,the use of MMC was a significant predictor of changes in CV(P=0.014)and the change in the percentage of hexagonality of EC(P=0.039)at M3.The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices,postoperatively.CONCLUSION:The use of MMC doesn’t affect ECD,CV,and percentage of hexagonality at W1 if other surgical indices are considered.At M3 after operating myopic eyes by TPRK,MMC significantly influence the CV and percentage of hexagonality.The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.

Therapeutic efficiency of tissue-engineered human corneal endothelium transplants on rabbit primary corneal endotheliopathy

To evaluate the therapeutic efficiency of tissue-engineered human corneal endothelia (TE-HCEs) on rabbit primary corneal endotheliopathy (PCEP),TE-HCEs reconstructed with monoclonal human corneal endothelial cells (mcHCECs) and modified denuded amniotic membranes (mdAMs) were transplanted into PCEP models of New Zealand white rabbits using penetrating keratoplasty.The TE-HCEs were examined using diverse techniques including slit-lamp biomicroscopy observation and pachymeter and tonometer measurements in vivo,and fluorescent microscopy,alizarin red staining,paraffin sectioning,scanning and transmission electron microscopy observations in vitro.The corneas of transplanted eyes maintained transparency for as long as 200 d without obvious edema or immune rejection.The corneal thickness of transplanted eyes decreased gradually after transplanting,reaching almost the thickness of normal eyes after 156 d,while the TE-HCE non-transplanted eyes were turbid and showed obvious corneal edema.The polygonal corneal endothelial cells in the transplanted area originated from the TE-HCE transplant.An intact monolayer corneal endothelium had been reconstructed with the morphology,cell density and structure similar to those of normal rabbit corneal endothelium.In conclusion,the transplanted TE-HCE can reconstruct the integrality of corneal endothelium and restore corneal transparency and thickness in PCEP rabbits.The TE-HCE functions normally as an endothelial barrier and pump and promises to be an equivalent of HCE for clinical therapy of human PCEP.

Design of functional biomaterials as substrates for corneal endothelium tissue engineering

Corneal endothelium defects are one of the leading causes of blindness worldwide.The actual treatment is transplantation,which requires the use of human cadaveric donors,but it faces several problems,such as global shortage of donors.Therefore,new alternatives are being developed and,among them,cell therapy has gained interest in the last years due to its promising results in tissue regeneration.Nevertheless,the direct administration of cells may sometimes have limited success due to the immune response,hence requiring the combination with extracellular mimicking materials.In this review,we present different methods to obtain corneal endothelial cells from diverse cell sources such as pluripotent or multipotent stem cells.Moreover,we discuss different substrates in order to allow a correct implantation as a cell sheet and to promote an enhanced cell behavior.For this reason,natural or synthetic matrixes that mimic the native environment have been developed.These matrixes have been optimized in terms of their physicochemical properties,such as stiffness,topography,composition and transparency.To further enhance the matrixes properties,these can be tuned by incorporating certain molecules that can be delivered in a sustained manner in order to enhance biological behavior.Finally,we elucidate future directions for corneal endothelial regeneration,such as 3D printing,in order to obtain patient-specific substrates.

Comment on “Role of corneal collagen fibrils in corneal disorders and related pathological conditions”

Dear Editor,We read with interest the review article'Role of corneal collagen fibrils in corneal disorders and related pathological conditions'by Zhou et al(1)We would like to point out the mistake that is made in the parts of the article.

1.8mm角膜微切口与3.0mm角膜切口同轴白内障超声乳化术对角膜内皮及术源性散光的对照观察

目的观察比较白内障超声乳化术1.8mm角膜切口与3.0mm角膜切口对角膜内皮和术源性散光的影响。方法根据不同术式将120例白内障患者随机分为1.8mm切口观察组与3.0mm切口对照组行预劈核超声乳化治疗,观察两组病例平均超声时间,平均超声能量,术前,第1d,1wk,1mo的视力、角膜散光变化、角膜内皮计数等情况。结果观察组和对照组有效超乳时间9.51±1.17,9.48±1.21及平均超乳能量(10.01±1.02)%(9.9±1.19)%比较差异均无统计学意义(P>0.05)。两组术前视力0.11±0.057,0.10±0.012比较无统计学差异(P>0.05),术后第1d两组视力0.376±0.071,0.319±0.14比较有统计学意义(P<0.05);术后1wk;1mo两组视力0.410±0.14,0.356±0.12,0.429±0.15,0.364±0.14比较有统计学意义(P<0.05)。平均角膜散光两组术前0.59±0.25,0.61±0.30比较无统计学意义(P>0.05),术后两组第1d(0.91±0.42,1.15±0.41),1wk(0.76±0.26,0.95±0.24)和1mo(0.66±0.23,0.74±0.25)比较有统计学差异(P<0.05)。角膜内皮计数两组术前2753.32±324.12,2645.36±321.45比较无统计学意义(P>0.05),术后第1d(2412.36±541.12,2397.62±204.21),1wk(2365.35±233.72,2351.36±248.63)和1mo(2298.37±251.89,2209.45±373.07),比较无统计学差异(P>0.05)。结论,1.8mm切口超声乳化术同传统3.0mm切口组比较,不导致超乳效率下降及更多的角膜内皮细胞的损伤,且术后医源性散光相较更小,术后视力更佳。

人工晶状体保护下超声乳化白内障吸除术疗效及安全性评价:一项随机对照临床研究

目的观察人工晶状体(IOL)保护下超声乳化手术(PHACO)对硬核白内障患者的治疗效果。方法采用随机对照临床研究方法,连续纳入2019年1月至2022年5月于延边大学附属医院收治的Emery分级Ⅳ~Ⅴ级的硬核白内障患者120例120眼,按照随机数字表法分为PHACO组、IOL保护PHACO组和囊外白内障摘除术(ECCE)组,分别行常规PHACO、IOL保护下的PHACO和ECCE,每组40例40眼。最终99例受试者完成随访,其中PHACO组30例30眼,IOL保护PHACO组35例35眼,ECCE组34例34眼。记录各组总手术时间、术中超声乳化时间、累计释放能量。术后随访3个月,检测并比较3个组患眼角膜内皮细胞密度(ECD)、角膜内皮细胞面积变异系数(CV)、角膜六角形内皮细胞比率(6A)、角膜散光值,不同等级裸眼远视力的眼数分布;记录术中和术后并发症发生情况。结果IOL保护PHACO组与PHACO组超声能量及超声时间比较差异均无统计学意义(P=0.691、0.982)。IOL保护PHACO组和PHACO组总手术时间分别为(38.81±2.73)和(36.45±3.45)min,明显短于ECCE组的(69.60±4.35)min,差异均有统计学意义(均P<0.001)。术前3个组患者年龄、性别、晶状体核硬度等基本资料比较,差异均无统计学意义(均P>0.05)。术后3个月,PHACO组和IOL保护PHACO组裸眼视力较高的人数较ECCE组高(P=0.006、0.007);IOL保护PHACO组的ECD和6A分别为(2155.57±177.88)/mm^(2)和(41.31±5.18)%,均显著高于PHACO组的(1912.64±224.11)/mm^(2)和(36.18±3.27)%,IOL保护PHACO组的CV为(50.34±5.90)%,低于PHACO组的(55.67±3.30)%,差异均有统计学意义(P=0.007、0.003、0.005)。术后1周和3个月,IOL保护PHACO组的角膜散光度数均显著低于ECCE组,且高于PHACO组,差异均有统计学意义(均P<0.05)。结论IOL保护下的PHACO相对常规PHACO可有效减少超声能量对角膜内皮的损伤,相对ECCE能明显缩短手术时间,减轻术后炎症反应,且并未明显增加术后角膜散光。IOL保护下的PHACO是硬核白内障患者一种有效的改良手术方式。

角膜内皮移植研究热点分析及未来研究方向预测

目的了解角膜内皮移植(EK)近年的文献分布规律和研究热点。方法以Web of Science核心合集中的科学引文扩展索引和社会科学引文索引为数据源,提取2011—2021年以EK为主题的文献,对以EK为主题、文献类型为论著的年文献量、文献发表量前10的作者和期刊、引用频次前10位的论文及其主要观点进行统计,并将文献数据导入VOSviewer软件,对EK相关领域文献的核心作者及关键词进行可视化分析。结果共检索出文献1454篇。2011—2021年,文献发表量的逐年累积量呈线性增长,美国是发表EK相关文献最多的国家,Melles GRJ的论文发表量和论文被引数均占据第1位,文献发表总量排名第1的期刊为Cornea。目前,EK的研究方向主要集中于多种术式术后效果的比较和相关并发症的处理。关键词分析显示,其被分为5个聚类,其中聚类1是关于EK术后视觉质量的评价;聚类2是术后并发症和移植失败高风险因素的分析;聚类3是以角膜后弹力层内皮移植(DMEK)为中心的适应证和手术技巧的研究;聚类4是植片相关问题,如植片制备、内皮细胞损失、术后植片脱位的处理等;聚类5主要是角膜移植术式的变化趋势。出现频次最多的关键词是DMEK,共559次,说明目前DMEK是EK相关研究领域的重点。2017年以来,"DMEK"、"previous trabeculectomy"、"graft preparation"、"stability"、"safety"、"air"等关键词出现频次增加,可见有青光眼手术史的病例处理、手术的安全性和稳定性、大气泡法制备植片是近几年来的研究热点。结论植片制备技巧、复杂病例处理、角膜内皮疾病患者青光眼的治疗方法、大气泡法制备植片的长期术后效果评估可能成为今后EK研究发展的方向。

Profile of biological characterizations and clinical application of corneal stem/progenitor cells

Corneal stem/progenitor cells are typical adult stem/progenitor cells.The human cornea covers the front of the eyeball,which protects the eye from the outside environment while allowing vision.The location and function demand the cornea to maintain its transparency and to continuously renew its epithelial surface by replacing injured or aged cells through a rapid turnover process in which corneal stem/progenitor cells play an important role.Corneal stem/progenitor cells include mainly corneal epithelial stem cells,corneal endothelial cell progenitors and corneal stromal stem cells.Since the discovery of corneal epithelial stem cells(also known as limbal stem cells)in 1971,an increasing number of markers for corneal stem/progenitor cells have been proposed,but there is no consensus regarding the definitive markers for them.Therefore,the identification,isolation and cultivation of these cells remain challenging without a unified approach.In this review,we systematically introduce the profile of biological characterizations,such as anatomy,characteristics,isolation,cultivation and molecular markers,and clinical applications of the three categories of corneal stem/progenitor cells.

Corneal stem cells and tissue engineering: Current advances and future perspectives

Major advances are currently being made in regenerative medicine for cornea. Stem cell-based therapies represent a novel strategy that may substitute conventional corneal transplantation, albeit there aremany challenges ahead given the singularities of each cellular layer of the cornea. This review recapitulates the current data on corneal epithelial stem cells, corneal stromal stem cells and corneal endothelial cell progenitors. Corneal limbal autografts containing epithelial stem cells have been transplanted in humans for more than 20 years with great successful rates, and researchers now focus on ex vivo cultures and other cell lineages to transplant to the ocular surface. A small population of cells in the corneal endothelium was recently reported to have self-renewal capacity, although they do not proliferate in vivo. Two main obstacles have hindered endothelial cell transplantation to date: culture protocols and cell delivery methods to the posterior cornea in vivo. Human corneal stromal stem cells have been identified shortly after the recognition of precursors of endothelial cells. Stromal stem cells may have the potential to provide a direct cell-based therapeutic approach when injected to corneal scars. Furthermore, they exhibit the ability to deposit organized connective tissue in vitro and may be useful in corneal stroma engineering in the future. Recent advances and future perspectives in the field are discussed.

The Study on Improved Cryopreservation Technique of The Ultrastructure of Corneal Endothelial Cells

The traditional corneal cryopreservation technique was improved. We carried out an experimental study that rabbit corneas were cryop-reserved by using polyvinylpyrolidone (PVP) as cryoprotective agent and dimethlsulfoxide (DMSO) as the control. The endothelia of cryopreserved corneas were evaluated by scanning and transmission electron microscopy and vital staining. The study shows that PVP is an excellent extracellular cryoprotective agent and has the characteristic of low toxicity or no toxicity to co...