Analogs of microgravity: the function of Schlemm's canal, intraocular pressure and autonomic nervous during the head-down tilt test in healthy subjects

AIM:To evaluate the ocular outcomes and to elucidate possible mechanisms underlying intraocular pressure(IOP)change following the head-down tilt(HDT)test.METHODS:The study included 21 participants at the Department of Ophthalmology of Tongji Hospital.Subjects received the test of I-care tonometry,enhanced depth imaging optical coherence tomography and heart rate variability(HRV)analysis before and after 15 min HDT test.The lumen area of Schlemm’s canal(SCAR),IOP,HRV were calculated.RESULTS:IOP increased significantly after 20°head down position from 14.0±3.0 to 17.0±3.3 mm Hg(P<0.001).SCAR decreased from 13449.0±5454.9μm^(2) at sitting condition to 9576.6±4130.9μm^(2) post 15 min HDT test.High frequency(HF)indices increased significantly from 1462±865 Hz at baseline to 2128±824 Hz.Heart rate(HR)decreased significantly from 76±11.48 to 70±11.52 bpm after the HDT.The linear regression analysis showed that the difference of HF and SCAR significantly correlated with each other during the HDT(R^(2)=20%,P=0.04).CONCLUSION:These outcomes perform the first evidence of the activation of autonomic nervous system of HDT may cause the collapse of Schlemm’s canal lumen,which in turn leading to the increased IOP.

Changes in Schlemm’s canal,trabecular meshwork,and relevant parameters in the early stage after SMILE of myopia patients

AIM:To observe the changes in Schlemm’s canal(SC),trabecular meshwork(TM),and anterior chamber relevant parameters after small incision lenticule extraction(SMILE) of myopia patients.METHODS:A total of 58 eyes from 30 patients who underwent SMILE were divided into a low and moderate myopia group(group A,32 eyes) and a high myopia group(group B,26 eyes).The diameter and area of the SC,the width and thickness of TM obtained by CIRRUS HD-OCT5000,and the related anterior chamber parameters obtained by Pentacam anterior segment analysis system,accommodation amplitude(AMP) were observed pre-and postoperatively.The preoperative intraocular pressure(IOP) and postoperative correction of intraocular pressure(IOPcc) were measured.RESULTS:The diameter and area of the SC in the two groups were significantly increased postoperatively(all P<0.01).The TM width of the patients in the two groups were increased at 1mo after surgery(both P<0.01),but the TM thickness did not change(P>0.05).The corneal curvature,central anterior chamber depth,and anterior chamber volume decreased after SMILE surgery(all P<0.01).There was a weak negative correlation between the SC area change and AMP change in group A(r=-0.362,P<0.01).The postoperative IOP decreased after correction by Shah formula(P<0.05).CONCLUSION:SC and TM in myopia patients change in the early postoperative stage of SMILE and the IOP is decline.

原发性开角型青光Schlemm管和集液管的病理形态学研究

目的研究原发性开角型青光眼(primary open-angle glaucoma,POAG)中集液管和Schlemm管的组织病理学特征,以探讨影响房水外流的阻力因素。方法选取经临床确诊的POAG病人20例(30眼)和经筛选的正常尸眼30只,采用透射电镜技术对房角组织进行超微结构形态学分析。结果实验组30眼中有27眼的集液管在Schlemm管外壁开口处存在电子致密物沉积,呈指纹状。电子致密物的数目与杯盘比(C/D)有正的直线相关关系(r=0.66,P<0.001);与年龄、术前眼压及视野缺损程度均无直线相关关系(r=0.03,P>0.50;r=-0.24,0.20<P<0.50;r=0.30,0.10<P<0.20)。在对照组30个标本的集液管在Schlemm管外壁开口处中均未观察到任何电子致密物等导致狭窄的因素。结论Schlemm管外壁尤其是集液管在Schlemm管外壁开口处的病变可能是形成POAG房水外流阻力的重要因素。

Schlemm管手术发展史

Schlemm管是围绕在前房角一周的房水流出管道,由若干小腔隙相互吻合而成,内壁仅有一层内皮细胞与小梁网相隔,外壁发出25~35条集液管与巩膜内静脉丛、睫状前静脉相通。由于Schlemm管是房水流出的必经通道,其房水排出通畅可维持正常的眼内压。若Schlemm管出现狭窄、塌陷、闭合等结构或功能的异常,房水流出受阻,可致眼压升高、青光眼发生。Schlemm管手术是指一类经Schlemm管增加房水引流通畅性的手术方式总称。随着临床对青光眼机制认识的不断加深,Schlemm管手术在不断创新,从传统到微创、从外路到内路。

Modified viscocanalostomy in the Chinese population with open angle glaucoma: a 10-year follow-up results

AIM: To study the long-term efficacy and safety of modified viscocanalostomy in Chinese people with open angle glaucoma(OAG).METHODS: This retrospective study included a total of 100 eyes from 100 Chinese patients with medically uncontrolled OAG. All the patients underwent modified viscocanalostomy with injection of viscoelastic material in the surgically created ostia of Schlemm's canal(SC). The modifications included peeling of the inner wall of SC and the juxtacanalicular meshwork, use of mitomycin C, and loosely suturing the superficial scleral flap. Intraocular pressure(IOP), visual acuity, number of medications, laser goniopuncture data and complications were recorded. The definition of complete(qualified) success was an IOP equal to or lower than 21, 18, 16 mm Hg without(with or without) anti-glaucoma medications. RESULTS: The mean IOP was 33.5±9.9 mm Hg before surgery, 15.2±3.6 mm Hg(mean IOP reduction of 51%) at 5 y after surgery, and 15.6±2.8 mm Hg(mean IOP reduction of 49.9%) at 10 y after surgery(P<0.001). The number of anti-glaucoma medications dropped from 2.39±0.5 preoperatively to 0.47±0.8 at 5 y and 0.67±0.8 at 10 y postoperatively(P<0.001). The follow-up period was 104.5±37.0 mo. The qualified success rate for an IOP of 21, 18 or 16 mm Hg or less was 84% [95% confidence interval(CI): 0.80-0.88], 73%(95%CI: 0.68-0.78), and 59%(95%CI: 0.52-0.66) after 5 y, and 80%(95%CI: 0.76-0.84), 69%(95%CI: 0.64-0.74), 51%(95%CI: 0.44-0.58) after 10 y, respectively. There was a relationship between age, preoperative IOP and success rate(P<0.01, P<0.05). A total of 31 eyes(31.3%)in 31 patients underwent laser goniopuncture, decreasing the IOP from 22.9±4.3 mm Hg to 16.3±2.5 mm Hg(P<0.01). Neither blebitis nor endophthalmitis occurred.CONCLUSION: Modified viscocanalostomy could be performed to lower IOP, decrease multiple anti-glaucoma drops use as well. It's a safe procedure with less complications over 10 y in Chinese individuals with OAG.

Schlemm管引流联合复合式小梁切除术治疗外伤性青光眼

目的探讨Schlemm管引流联合复合式小梁切除术治疗外伤性青光眼的可行性和疗效评价。方法对23例(23眼)因眼外伤房角后退继发开角型青光眼患者施行Schlemm管引流联合复合式小梁切除术,术后观察眼压、矫正视力、前房情况、术后并发症和滤过泡的形态等。术后随访6～24个月,平均(14.46±9.16)月。结果术后1 d、1周、1月、3月、6月、12月平均眼压分别为(8.7±3.19)mmHg、(9.14±4.62)mmHg、(13.62±3.10)mmHg、(13.77±4.11)mmHg、(14.55±6.02)mmHg、(15.98±5.12)mmHg。与术前平均眼压(31.73±8.66)mmHg比较差异均具有统计学意义(P均<0.05)。最末次随访平均眼压(16.41±4.25)mmHg,与术前平均眼压比较,差异具有统计学意义(t=13.547,P=0.000)。术后21眼眼压控制在正常范围,手术成功率91.30%。15眼(65.22%)形成功能性滤过泡,6只眼(26.09%)为非功能滤过泡,但眼压正常范围内。术后并发症主要是早期前房出血。结论Schlemm管引流联合复合式小梁切除术治疗外伤性青光眼安全有效,并发症少,具有良好临床应用前景。

Abnormal Systemic and Ocular Responses to the Valsalva Manoeuvre in Primary Open-Angle Glaucoma:A Case for Autonomic Failure?

Objective This study aimed to examine the association of primary open-angle glaucoma(POAG)with autonomic dysfunction by assessing the differences in systemic and ocular responses to an autonomic provocation test,the Valsalva manoeuvre(VM),between POAG patients and normal subjects.Methods Forty POAG and forty control subjects were subjected to the VM.Systemic and ocular parameters were measured at baseline,phase 2,and phase 4 of the VM(VM2 and VM4),where VM2 and VM4 are sympathetic and parasympathetic nervous activation states,respectively.Heart rate variability was used to assess the autonomic nervous activity,among which the high-frequency component(HF)and the low-frequency(LF)/HF ratio were used as indices of parasympathetic and sympathetic activation,respectively.Results POAG patients demonstrated higher sympathetic activation(LF/HF ratio median:2.17 vs.1.53,P=0.000)than controls at baseline and exhibited attenuated sympathetic and parasympathetic responses(a smaller change in LF/HF and HF values)during the VM than controls.During VM,the intraocular pressure(IOP),mean blood pressure(MAP),mean ocular perfusion pressure(MOPP),and the Schlemm’s canal area(SCAR)increased from baseline to VM2 and then decreased from VM2 to VM4 in both the POAG and control groups(all P<0.05).However,when we compared the changes above,the fluctuations in IOP,MAP,and MOPP were more pronounced in POAG than in controls(all P<0.05),while the changes in amplitudes of SCAR were smaller in POAG(P<0.05).Furthermore,from VM2 to VM4,the choroid thickness(ChT)in the POAG group was significantly decreased,while it was unchanged in normal subjects(P=0.258).A regression analysis showed a significant correlation of the baseline LF/HF with IOP change values(ΔIOP)from baseline to VM2 in POAG(R^(2)=0.147,P=0.014).Conclusion Patients with POAG showed more pronounced fluctuations in IOP,MAP,MOPP and ChT during the VM than controls.These reactions could be associated with autonomic dysfunction in POAG.

Morphological changes in Schlemm's canal in treated and newly diagnosed untreated glaucomatous eyes

A custom built 1310 nm center wavelength swept source optical coherence tomography instrument was used to measure morphological changes in treated and newly diagnosed untreated glaucomatous human Schlemm’s canal(SC).Thirty-seven primary open-angle glaucoma patients were divided into two groups depending on the patients having been treated or not.The statistical results showed that there were significant differences between the treated and untreated groups’SC areas(treated,7935.6875±680.003μm2;untreated,3890.71875±871.49844μm2;P<0.001),the circumferences(treated,580.37891±44.96529μm;untreated,381.9026±41.22123μm;P<0.001),and the long diameters(treated,272.87806±25.7254μm;untreated,185.24047±19.72786μm;P<0.001).We hypothesize that,after drug treatment,the SC will expand and the morphometric values especially the areas will become larger,thus helping to reduce intraocular pressure.

Ab externo canaloplasty results and efficacy: a retrospective cohort study with a 12-month follow-up

Background:The aim of this study is to review the outcomes of canaloplasty versus canaloplasty combined with phacoemulsification in a retrospective cohort study and to evaluate the efficacy of these methods in terms of intraocular pressure(IOP)lowering effect,postoperative complications and additional glaucoma surgery or reintroduction of medical therapy over a 12-month follow-up.Methods:In a retrospective cohort study,602 eyes with primary open angle glaucoma(POAG)were treated with canaloplasty or canaloplasty combined with phacoemulsification.The results were evaluated separately in two main groups;group A canaloplasty(262 eyes)and group B canaloplasty combined with phaco(322 eyes).Each group was then subdivided into three additional groups according to the severity of glaucoma.The criteria for successful treatment were evaluated between three IOP ranges;IOP≤16 mmHg,18 mmHg and 21 mmHg.Complete success was considered the percentage of eyes reaching target IOP with no medication and partial success with medication.Groups A and B subgroups were compared using the Kaplan Meier test.Mean IOP,reduction of antiglaucoma agents and additional IOP lowering methods were also evaluated.The follow-up time was 12 months.Statistical significance was set at p<0.05.Results:An incomplete intraoperative cannulation of Schlemm’s canal resulting in conversion to other glaucoma surgery occurred in 18 eyes(2.99%).In both of the main groups,postoperative hyphema,descemet membrane detachment and transient IOP rise were the most common postoperative complications.The mean IOP in group A and subgroups at 12 months was 13.26±4.5 mmHg,15.19±3.97 mmHg and 18.09±3.75 mmHg.Respectively in group B mean IOP was 14.51±4.69 mmHg,14.40±4.11 mmHg and 14.25±2.76 mmHg.Complete success was achieved in group A in 69.19,74.51 and 74.31%of eyes.In group B complete success was achieved in 81.60,77.33 and 83.33%of eyes respectively.Kaplan Meier between groups A and B was statistically significant for IOP≤16 mmHg and IOP≤21 mmHg(p=0.0041 and p=0.0312),but not for IOP≤18 mmHg(p=0.6935).Partial success for IOP≤16 mmHg was 95.23 and 92.26%,for IOP≤18 mmHg was 91.66 and 90.47%and for IOP≤21 mmHg,90.00 and 93.10%,in groups A and B respectively.Twenty-three eyes received additional surgery(3.93%),10 trabeculectomies and 2 cyclophotocoagulation in group A,and 9 trabeculectomies and 2 cyclophotocoagulation in group B.Conclusion:Canaloplasty and canaloplasty combined with phacoemulsification significantly lower the IOP and have a lower postoperative complication rate.Additional glaucoma surgery or medication following both procedures is necessary if target IOP is unsatisfactory.In this study,canaloplasty combined with phacoemulsification demonstrated superior success rate compared to canaloplasty alone.

Hydrus microstent implantation for surgical management of glaucoma: a review of design, efficacy and safety

With the advent of microinvasive glaucoma surgery(MIGS),the spectrum of modalities available to manage patients with this chronic and heterogeneous condition has broadened.Despite its novelty however,there has been a rapid evolution in the development of a multitude of devices,each targeting a structure along the aqueous drainage pathway.A growing body of evidence has demonstrated IOP and medication burden reduction,and a more favorable safety profile with MIGS procedures in contrast to traditional incisional surgeries.Among the array of MIGS,the Hydrus®Microstent(Ivantis,Inc.,Irvine,CA)is a recent FDA approved device,designed to bypass the trabecular meshwork and provide a scaffold for Schlemm’s canal.The objective of this article is to review the Hydrus from conception to clinical use,and present data on its efficacy and safety to date.The available literature has shown promise,however inherent to all novel devices,only longterm monitoring will ensure sustained IOP control and an acceptable safety profile.Surgical advancements in glaucoma have revolutionized the field,and continued research and development will establish these approaches in clinical treatment algorithms.

基于双光子共聚焦成像技术的小梁网通道原位成像研究

目的观察基于双光子共聚焦成像技术在不进行组织固定和染色的情况下获取大鼠小梁网外流通道微观结构图像的应用效果。设计实验研究。研究对象 SD大鼠6只。方法将6只大鼠随机分成两组(A组和B组),A组大鼠的完整眼球用于小梁网通道纵截面成像数据的获取;B组大鼠左眼球剖开用于小梁网通道横截面及眼球矢状面成像,右眼球为对照组。采用自行搭建的双光子共聚焦成像系统(激发波长950 nm、侧向分辨率0.3 μm、轴向分辨率1.5 μm),从前房角处进行成像,获取不同方位小梁网及其周围组织的微观结构信息。通过图像处理方法,定量分析Schlemm管截面直径随成像深度的变化情况。主要指标不同方位小梁网通道成像深度、小梁网微观结构特点及Schlemm管平均截面直径。结果基于双光子共聚焦成像技术分别获取到小梁网通道纵截面、横截面以及眼球矢状面的图像数据。不同深度的小梁网通道组织形态结构各异,深层小梁网纤维排列致密,形成的孔隙较小;浅层小梁网的纤维相互交错,形成的孔隙较大,利于房水流出。在角巩膜缘下方190~215 μm成像深度范围内,Schlemm管的平均截面直径在34~68 μm之间变化。结论双光子共聚焦成像可观察小梁网通道的微观结构,为进一步小梁网通道房水外流动力学研究奠定了基础。