Monitoring of central corneal thickness after phacoemulsification—comparison of statical and rotating Scheimpflug pachymetry, and spectral-domain OCT

INTRODUCTION

Different measuring techniques have also been investigated and compared

All authors underlined poor comparability between different techniques while the consistency and reliability were high.

(3) 强风化泥灰岩(T1d)③：褐黄色，泥质成分，风化裂隙发育，岩芯多呈碎块状夹土状，碎块状岩芯粒径一般为1～5 cm，干时可用手折断或捏碎，遇水易软化，为软岩，岩体基本质量等级为Ⅴ级，厚度0.9～6.9 m，分布不均匀。

The ultrasound energy needed to fragment the hard nucleus during cataract surgery strains the corneal epithelium

. A transient endothelial deterioration reduces the rate of intrastromal dehydration leading to an imbalance between influx of water from the anterior chamber into the corneal stroma and the active transportation of water into the anterior chamber by the corneal endothelium. This results in corneal swelling and thereby an increase in central corneal thickness (CCT)as an expression of endothelial decompensation. Extent and decrease of corneal swelling prove the endothelial recovery and compensation of its function

.

4.空气滤清器罩排尘孔堵塞后空气中尘粒排不出易堵塞下级滤网吸气减少功率下降甚至尘粒进入燃烧室加快气门缸套活塞等机件磨损。

Ultrasound pachymetry posed the gold standard for measuring the CCT for many years. Disadvantages of this method are poor reproducibility and dependency on the examiner in general

. On the other hand, sonography is a contact process, which can additionally affect the cornea which may be harmed by surgery already. Finally there is the toxicity of topical anaesthetic agents which are necessary for ultrasound pachymetry

.

“冰说”以韩同林、郭克毅为代表，他们认为，冰臼主要是由冰川融水(包括冰川压融水)携带大量冰碎屑、岩屑及冰川粉物质，沿冰川裂隙自上向下以滴水石穿的方式形成滚流水钻，对下伏基岩进行强烈的冲蚀和研磨作用下形成的。

Apart from ultrasound pachymetry a number of non-contacttechniques have been developed and established which are able to measure CCT

. The goal of this study was to evaluate the feasibility of different techniques to measure CCT in the perioperative course of uneventful cataract surgery using phacoemulsification.

Reliable and reproducible measurements which can be delegated to medical assistance personnel are desireable.The examination should be carried out quickly. For economic reasons the inclusion of corneal pachymetry into a multifunctional device is desireable. In this study modern noncontact-techniques for measuring the CCT were evaluated.Besides comparing three different devices, the feasibility of measurements was examined in a real-life-situation.

Economical aspects are becoming more and more important as many surgical units are performing 20, 30, 50 or even more cataract operations every day and postoperative care must be provided. This is an important issue as the resource “ophthalmologist/physician” is becoming scarce and sought after. So as many parts of the examination as possible have to be delegated to medical assistance personnel.

SUBJECTS AND METHODS

There were significant differences concerning repeated measures with both device and point of time (

-test).Significance with interaction in the last line points out that the profiles in the course of time were distinguishable for each device.

［本刊讯］上海市护理学会第九届优秀论文评选活动已于近日顺利结束。本届评选活动共收到来自上海各级医院、护理院校及部队医院等51家单位送评的近400篇护理论文，上海市护理学会学术专委会及有关专家经过初评、复评和终评后，最终评选出一等奖2篇、二等奖4篇、三等奖8篇、四等奖16篇及优胜奖30篇。具体奖项及获奖名单详见彩版插页。

All surgical procedures were performed by the same surgeon(Handzel DM) using topical or parabulbar anaesthesia and a divide-and-conquer-technique through a 2.8 mm main incision.A foldable 1-piece-intraocular lens (IOL) was implanted in the capsular bag in all cases. Postoperatively dexamethasone/gentamycin-ointment was applied. The same medication was prescribed as eye drops in a tapered regime for the following 4wk.All selected patients underwent a comprehensive ophthalmological examination (U1) within 4wk prior surgery. This included objective refraction, best corrected visual acuity, tonometry,anterior segment Scheimpflug imaging, optical coherence tomography (OCT) of the anterior segment and if needed the macula, slit lamp examination and fundoscopy. The CCT was readout after using statical Scheimpflug imaging (NIDEK NT 530-P) which takes place during tonometry, rotating(Sirius) Scheimpflug photography and anterior segment-OCT(Topcon-2000).

Further examinations were performed on the first day postoperatively (U2), 3-6d postoperatively (U3), and 3-5wk postoperatively (U4). Besides a comprehensive postoperative clinical examination, CCT was measured at each visit.

An important aspect of this study was the comparability of the three devices under demanding–in this case perioperativecircumstances. Correlations of the results are given in Table 2.All bivariate correlations between the three devices were highly significant (

≤0.001) at (almost) every point of time. This implies good comparability of different devices at different points of time. An important exception can be seen with the Scheimpflug camera: the results of the Sirius device differed significantly from the other two devices at U2,compared to the OCT also with U3 (Tables 3 and 4).

The Scheimpflug camera Sirius (Fa. Costruzione Strumenti Oftalmici, Scandicci,Italy) is a new multifunctional device, which is also equipped with a Placido-system for corneal topography, infrared meibography, pupillography and tear film analysis.

A rotating Scheimpflug camera is acquiring 25 radial images of the cornea and the anterior chamber in 2-3s. The images are analysed and the results include tangential and sagittal curvature data for the anterior and posterior surface of the cornea, corneal refractive power, biometrical analysis of multiple structures of the anterior segment (anterior chamber volume, chamber angle

.), a calculation of the corneal wavefront and corneal pachymetry. The system is measuring 35 632 points on the anterior and 30 000 points on the posterior surface of the cornea during 5-6s. This data is calculated to a pachymetry map by version 1.0.5.72 of the Phoenix

software(Fa. Costruzione Strumenti Oftalmici, Scandicci, Italy).

他人的现在或许就是我们的明天，善待别人，其实就是善待自己。世间没有一个人是孤岛，我们无形中会跟许多人发生联系。你待人冷漠，别人遭受了伤害，说不定他日后也会变得冷血，当大家都自私自利，你遇了事也就无人相帮；你待人热情，别人得到了温暖，他内心也会变得温热，你遇上急难，别人也会自然而然地帮助你，我们出门在外就有了基本的安全感。

The OCT-2000 (OCT-2000, Topcon Europe Medical B.V., Capelle a/d IJssel, The Netherlands) is a multifunctional OCT for imaging the anterior and posterior segment of the eye. Scanning method for the cornea is a radial scan of 6 mm with a line resolution of 4096 pixel and an axial depth resolution of 5 µm.

All examinations were carried out by well-trained medical technicians according to themanufacturer’s advice. The patient was advised to focus on an indicator light and asked to blink prior image acquisition to assure an evenly spread tear film. If image quality was not satisfactory, unpreserved lubricant eye drops were applied and the examination repeated.

Statistical analysis was performed using IBM SPSS Statistics, Version 22. The statistical test used are given in the results section. All data was worked up identifying maximum, minimum, mean, standard deviation and variance.Correlations were investigated using Pearson’s correlation and checked by Bonferroni-correction.

Use of the devices perioperatively by medical assistance personnel under reallife circumstances in order to get useful and valid results;Correlations of CCT for every measurement (U1, U2, U3, U4)and between the different devices.

RESULTS

The results of 71 eyes were analyzed. CCT was measured at four different point of time. Some data could not be gathered due to different reasons all concerning the patients’cooperation. The amount of missing data did not differ significantly between the devices as will be explained in more detail below (Table 1).

As expected, an increase in CCT was noticed on the first postoperative day (U2). This increase was detected as statistically significant with all three devices. At U3 there was a tendency toward a decrease in CCT which was not statistically significant. At U4 CCT was measured within the range of preoperative results which was statistically significant(Figure 1).

The Nidek NT-530P is a combination of a non-contact tonometry and pachymetry.The camera is placed diagonally below the cornea, and then sections of cornea are reflected through the lens and projected on the camera. The anterior and posterior position of the cornea are reflected on different positions of the camera. The corneal thickness can be calculated by the distance between these. The result is given by a printout listing the measured values, an image is not available.

The study was approved by the Ethical Committee of the University of Bonn, Germany and conducted per the international ethical standards outlined by the Declaration of Helsinki. Informed consent was obtained from the patients.Totally 71 patients with sight-limiting cataract were included in this study. The patients’ age was 79.09±5.84y (54-89y), 30(42.2%) males, 41 (57.7%) females. Patients were selected after uneventful cataract surgery. Exclusion criteria were previous ocular surgery, corneal disease of any kind or incompliance to therapy or follow-up visits.

This was done by examination of untreated eyes (U1) and during the postoperative period (U2-U4). Beside the comparability of the devices, their use under difficult conditions, which can occur postoperatively (periocular swelling, corneal edema,folds of Descemet’s membrane

.) was an important outcome of this study.Comparing the three devices this study could show significant differences in results produced with the Sirius and the Topcon device (

=0.010) and between Sirius/Nidek (

<0.0005). There were no differences in the comparison of the Topcon and the Nidek device (

=0.056). The use of the Sirius camera resulted in fewer reliable results than with the other two devices used in this study. This has to be explained with the more complex acquisition process with the rotating camera, which can be made more difficult by conditions like lid swelling or corneal edema which are not that challenging with a frontal acquisition process as used by the Topcon and the Nidek device.

Device: significance for Sirius/Topcon (

=0.010) and Sirius/Nidek (

<0.0005). No difference for Topcon/Nidek (

=0.056)Point of time: significance for U1/U2, U1/U3, U2/U4, U3/U4 respectively, no significance for U1/U4 an U2/U3. This means CCT increases from U1 to U2, stays on this level until U3 and decreases on U4 to the level of U1 (Table 5).The estimate of covariance parameters is–apart from two exceptions–highly significant different from zero, another structure is not detectable. So, it will not be moved away from the assumption of an unstructured covariance matrix.

DISCUSSION

The strain on the corneal endothelium by a variety of mechanical and toxic influences which occur during cataractsurgery is one of the greatest risk factors for postoperative complications

.

Compromising of the corneal endothelium leads to a transitory reduction of its capability to dehydrate the corneal stroma,thus leading to a corneal edema. For this reason, it is important to monitor the rehabilitation of the endothelial capability of postoperative corneal dehydration. Postoperative swelling as well as the following corneal dehydration and the associated detumescence caused by the endothelium’s pump function could be shown significantly with all devices used.

The application of different devices and techniques for measuring the CCT have already been evaluated by numerous studies

. Most of these publications compared the results of measurements taken with the present gold standard, ultrasound pachymetry. Jin

and Jorge

demonstrated excellent accordance in measurements taken by a Scheimpflug camera with ultrasound pachymetry. Especially Jorge

underlined that a feasible compensation of the results remained not possible. Anterior segment OCT was also compared with ultrasound pachymetry when measuring CCT

. The feasibility of anterior segment OCT was shown but also with this device there was no interchangeability with results generated by ultrasound pachymetry, although correlations remained acceptable

.

Evaluations have been performed between different imaging techniques. Different authors have compared results of Scheimpflug imaging and anterior segment-OCT

.Most authors emphasize low comparability between different techniques whereas validity within every single technique is very high. Other authors have found correlations that would allow an interchange of results using different techniques

.The use of these devices postoperatively has not yet been described. Our study was to investigate the comparison of three different devices but for the first time also their practical application apart from study conditions with optimised circumstances.

Follow up-tests (

-values after Bonferroni-correction) for the significant parameters device and point of time brought the following results:

A high preoperative endothelial cell count (ECC) does not guarantee an uncomplicated intra- and postoperative course and a low ECC does not make corneal complications not inevitable.Taking these conditions into account it is any case mandatory to monitor the postoperative course of the cornea. This can be done be measuring the increase and decrease of the CCT as a result of the endothelium’s ability to compensate its function.Preoperative measurements will be used as a reference.

对于未来中国家电行业形势的展望，来自全国家用电器工业信息中心的高级研究员苏亮先生分析，步入2019年，我国的家电行业会普遍出现增速放缓、且需要长期调整的态势，唯有抓住为数不多的机会点才能有所突破。苏亮表示，未来将会是一个全面围绕用户的时代，这就和“嘉电”的初衷不谋而合。

On the other hand, the Scheimpflug camera offers numerous additional information which can be of interest in a postoperative situation. All this information is available within a single successful image acquisition without additional loss of time.Depending on the particular situation this can be aspects as wound construction

, anterior chamber configuration

or the position of the implanted lens in the anterior chamber, the ciliary sulcus or the capsular bag

.

The advantage of measurements with the Nidek NT 530-P is without doubt the very fast course of image acquisition, which is generated during pre- and postoperative IOP-measurement nearly without delay. In contrast to that the imaging process with the OCT-2000 presents the most time-consuming procedure as an additional device has to be used.

Postoperative alterations of the cornea can aggravate difficulties of the measurements. High EPT as an indicator of a more complicated operation, which demands more ultrasound energy because of a harder nucleus or prolonged intraocular manipulation, is a common feature. But there are other postoperative changes affecting the quality of the image and so the result. These are corneal edema, Descemet’s folds, which can be seen after considerable intraocular manipulation or lid swelling due to perioperative medication or the lid speculum.

The variance in variability of valid data can be partly explained by the examination method. Kurten

compared the postoperative increase of CCT measured by sonography,Scheimpflug imaging and OCT. Kuerten

showed an increase in CCT to a considerable higher degree as in this study, the mean of CCT was distinctly above 600 µm,which was not reached by any technique in this study. This can be explained by a higher surgical stress leading to more endothelial decompensation or with different devices using the same technique in the two studies. This assumption is supported by the fact that the increase in CCT in the study by Kuerten

was greater when measured with the rotating Scheimpflug camera than with the OCT whereas in this study it was diametrically opposite. The study by Kuerten

used other devices (Pentacam, Fa. Oculus, Wetzlar, Germany and Spectralis OCT, Fa. Heidelberg Engineering, Heidelberg,Germany). Possibly there are considerable differences between devices of the same imaging technique from different manufacturers

.

The use of the devices in anterior segment diagnostics and especially in measuring CCT has already been evaluated extensively

. Most studies compared the results with the gold standard, ultrasound pachymetry.Various authors have found excellent correlations of CCT measured with Scheimpflug diagnostics and ultrasound pachymetry

. Similar results were found for OCT

.

The human cornea is composed of multiple layers.The external epithelium is situated on the Bowman’s membrane. The corneal stroma, consisting of collagen fibres,has the biggest share of the corneal thickness, followed by another basal membrane (Descemet’s membrane), which acts as a base for the endothelium, the barrier to the anterior chamber.Aqueous humour diffuses the corneal stroma from the anterior chamber. At the same time the endothelium dehydrates the cornea by pumping fluid from the cornea into the anterior chamber to maintain an equilibrium between both components and keep the cornea transparent. If the hydration of the cornea is increased, its symmetrical collagen network gets destroyed and the stroma appears oedematous and opaque. The loss of the corneal transparency leads to deteriorated visual acuity

.

Comparing the three devices in this study significant differences were highlighted between Sirius/Topcon (

=0.010)and between Sirius/Nidek (

<0.0005). No differences were seen when comparing Topcon/Nidek (

=0.056).

新型农村合作医疗制度是在2002年10月首次提出，并在2003年制订的《关于建立新型农村合作医疗的意见》中将政策进一步细化，它是指由政府组织、引导、支持，农民自愿参加，个人、集体和政府多方筹资，以大病统筹为主的农民医疗互助共济制度，采取个人缴费、集体扶持和政府资助的方式筹集资金。

Using the Scheimpflug device resulted in fewer reliable results compared to the other two devices.

This might be due to higher efforts when using this technique as the rotating camera takes more time and postoperative changes like lid swelling or corneal edema might be more disturbing than using a frontal position in image/measurement acquisition. On the other hand, multiple information can be gained using the Scheimpflug technique apart from CCT.Depending on the problem this can be wound construction

,anterior chamber configuration

or position of the implanted anterior or posterior chamber lens

. The advantage of using the Nidek NT 530-P is very fast data acquisition simultaneously to the obligate measurement of the intraocular pressure. In contrast to this the application of the Topcon OCT-2000 requires the use of an additional device and examination.Postoperative corneal swelling and the following reduction of CCT could be detected statistically significant with all three devices. The differences in the availability of reliable data can be explained by the examination technique.

回顾分析该院内分泌科在收治的2型糖尿病患者148例进行临床对比研究，采用随机数字表法将所有患者分为常规组与研究组，各74例。常规组74例患者，男 41例，女 33例，年龄 48～73岁，平均年龄（60.48±5.41）岁，病程 0.6～11 年，平均（5.81±1.02）年；研究组 74例患者，男43例，女31例，年龄47～78岁，平均年龄（62.53±6.05）岁，病程 0.8～12 年，平均（6.37±1.21）年，该次研究获该院伦理会批准实行，对比两组患者一般资料后差异无统计学意义（P＞0.05），治疗结果具有可比性。

Measurements were feasible at all points of time pre- and postoperatively to a satisfying amount. However, there were significant differences between the devices concerning the rate of reliable data.

网络空间主权理念下，网络恐怖主义这一非传统领域的安全威胁构成对本国主权的侵犯，对国家安全产生严重影响，才能迫使国家积极主动对外寻求合作防范网络恐怖主义的袭击。同时各国在行使网络空间主权时应秉承互相尊重的理念，防止借网络反恐之名干涉别国内政。明确网络空间主权，也使得各国打击网络恐怖主义有了明确的分工，有助于建立和平安全有序的网络格局。我国政府对网络主权非常重视，在《国家安全法》和《网络安全法》中均确立了“网络空间主权”的概念，表达了我国捍卫网络空间主权、积极开展国际合作的态度和立场。

In conclusion, three different, partly multifunctional devices with the capability of measuring the CCT were evaluated pre- and postoperatively in the course of routine cataract surgery. While feasibility and reliability of these techniques in measuring CCT have been looked into previously in numerous studies, this study explored measurements under more difficult circumstances like immediate postoperative examinations.

Measurements were successful for all points of time with all devices to a satisfying degree. However, there were differences between the three devices used in this study. The Sirius Scheimpflug camera stood out with a significantly lower degree of utilisable images.The already known phenomenon of postoperative corneal edema and swelling due to transient disturbance of the corneal endothelium could be proven with statistical significance with all three devices.

The analysed devices/techniques were altogether suitable for perioperative monitoring of the corneal thickness. The results are only comparable to a limited extent and not interchangeable during the course of postoperative recovery.The reasons for this can be found in different techniques of image acquisition but also in differences between devices with the same technique of different manufacturers.

This study shows that numerous devices are capable of measuring CCT perioperatively. The choice which device to choose has to be based on the information wanted to extract out of a single examination (

, relevance of corneal topography, interest in anterior chamber morphology or location of an implanted lens) but also effort and speed of a single examination.

ACKNOWLEDGEMENTS

Handzel DM, None; Meyer CH, None;Wegener A, None.

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