Importance of 3-D image reconstruction of spectraldomain OCT on outcome of grid laser photocoagulation for diffuse diabetic macular edema

AIM:To present the outcome of modified grid laser photocoagulation(GLP)in diffuse diabetic macular edema(DDME)in eyes without extrafoveal and/or vitreofoveal traction.METHODS:Inclusion criteria for the retrospective study were DDME eyes of patients with typeⅡdiabetes mellitus that had≥4 months of follow-up following GLP.Only one eye per patient was analyzed.Using 3-D spectral-domain optical coherence tomography(3-D SDOCT),eyes that had either extrafoveal or vitreofoveal traction,or had been previously treated by an intravitreal medication(s)were excluded.Treated DDME eyes were divided into 4 groups:A)"Classic"DDME that involved the central macula;B)edema did not involve the macular center;C)eyes associated with central epiretinal membrane(ERM);D)DDME that was associated with macular capillary dropout≥2 disc-diameter(DD).RESULTS:GLP outcome in 35 DDME eyes after 4-24(mean,13.1±6.9)months was as follows:Group A)18eyes with"classic"DDME.Following one or 2(mean,1.2)GLP treatments,best-corrected visual acuity(BCVA)improved by 1-2 Snellen lines in 44.4%(8/18)of eyes,and worsened by 1 line in 11.1%(2/18).Central macular thickness(CMT)improved by 7%-49%(mean,26.6%)in77.8%(14/18)of eyes.Causes of CMT worsening(n=4)were commonly explainable,predominantly(n=3)associated with emergence of extrafoveal traction,5-9months post-GLP.Group B)GLP(s)in DDME that did not involve the macular center(n=6)resulted in improved BCVA by 1-2 lines in 2 eyes.However,the central macula became involved in the edema process after the GLP in 3(50%)eyes,associated with an emergence of extrafoveal traction in one of these eyes 4months following the GLP.Group C)GLP failed in all 5eyes associated with central ERM.Group D)GLP was of partial benefit in 2 of 6 treated eyes with macular capillary dropout≥2DD.CONCLUSION:Eyes with DDME that involved the macular center were found to achieve favourable outcomes after GLP(s)during mid-term follow-up,unless complicated pre-GLP or post-GLP by vltreoretinal interface abnormalities,often extrafoveal traction or ERM,or by capillary dropout≥2DD.Prospective studies with larger cohorts are required.

基于全量程的复谱频域OCT系统

为了改善经典谱频域光学层析成像(OCT)技术,提高层析图像的分辨率,实现全量程的有效探测深度,采用了3种改进方法,相移谱频域OCT、相移差分谱频域OCT和复谱频域OCT,对测试样品三层盖波片进行成像实验.实验结果表明,相移谱频域OCT和相移差分谱频域OCT虽然可以消除图像的混叠,提高图像的分辨率,但是它们的有效探测深度小于全量程的一半.复谱频域OCT不仅可以消除图像的混叠,提高图像的分辨率,而且可以实现全量程的有效深度探测.

Microperimetry and spectral domain optical coherence tomography in myelinated retinal nerve fibers

Dear Sir,I write to present the correlation between microperimetric （MP） values and the density of myelinated retinal nerve fibers （MNFs） in optical coherence tomography （OCT） imaging.

Iterative sparse reconstruction of spectral domain OCT signal

We propose and study an iterative sparse reconstruction for Fourier domain optical coherence tomography （FD OCT） image by solving a constrained optimization problem that minimizes L-1 norm. Our method takes the spectral shape of the OCT light source into consideration in the iterative image reconstruction procedure that allows deconvolution of the axial point spread function from the blurred image during reconstruction rather than after reconstruction. By minimizing the L-1 norm, the axial resolution and the signal to noise ratio of image can both be enhanced. The effectiveness of our method is validated using numerical simulation and experiment.

谱域OCT技术在非球面镜面型测量中的应用

大多数光学系统都会用到光学透镜,球面镜、非球面镜在光学系统中的合理运用可使系统的成像深度更大,成像分辨率更高。同时对光学透镜的生产和检测提出了更高的技术要求。传统非球面镜检测方法一般是容易对镜面造成损坏的接触式测量以及测量时间长、检测口径有限的轮廓仪检测法。为此,文章提出一种基于谱域OCT技术的非接触式测量方法,解决了OCT在扫描高透光的非球面透镜时,透镜表面不规则散射光导致难以成像的问题,可以快速高效地对非球面透镜进行扫描成像,通过对采集到的图像数据进行面型拟合,进而计算出非球面镜的面型参数,包括非球面半径和非球面系数,为非球面镜的检测提供一种准确高效、无镜面损伤风险的技术支持。

Comment on “The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography”

Dear Editor,We have read and reviewed the article entitled＂The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography＂by Zhao et al^（[1]）with great interest.

光学相干层析系统噪音分析(Ⅱ)——时域OCT和频域OCT

本文作为前文《光学相干层析系统噪音分析(I)》的后续,对时域OCT和频域OCT的噪音和灵敏度进行了详细的分析和计算,证明与时域OCT系统不同,频域OCT系统的信噪比与光源带宽和纵向扫描深度无关,频域OCT系统可以在高速率图像采集的情况下仍然保持探测系统的大动态范围.

频域OCT的光学相移器的标定

提出了一种对频域光学相干层析(OCT)系统中压电陶瓷相移器进行标定的方法。该标定法是在用干涉条纹跟踪法初步标定的基础上,用差分光谱法进行精确标定来实现的,可将标定精度提高约6%。在差分频域OCT系统中进行了实验验证,表明该方法能够将频域OCT图像的信噪比提高约10%。

Systematic review of macular ganglion cell complex analysis using spectral domain optical coherence tomography for glaucoma assessment

AIM: To review the use of spectral domain optical coherence tomography(SD-OCT) for macular retinal ganglion cells(RGC) and ganglion cell complex(GCC) measurement in glaucoma assessment, specifically for early detection and detection of disease progression. METHODS: A systematic review was performed by searching Pub Med, Medline, and Web of Science for articles published in English through July 2014 describing the various macular SD-OCT scanning strategies developed for glaucoma assessment. The review focused on papers evaluating the use of macular RGC/GCC SDOCT to detect early glaucoma and its progression. The search included keywords corresponding to the index test(macular ganglion cell/RGC/GCC/Spectral domain OCT), the target condition(glaucoma), and diagnostic performance. The RGC/GCC SD-OCT scanning strategies used to assess glaucoma of most commonly used SD-OCT instruments were described and compared. These included the Cirrus high definition-OCT(Carl Zeiss Meditec, Inc., Dublin, CA, United States), RTVue(Optovue, Inc., Fremont, CA, United States), Spectralis(Heidelberg Engineering, Heidelberg, Germany) and the 3D OCT 2000(Topcon Corporation, Tokyo, Japan). Studies focusing on the ability of RGC/GCC SD-OCT to detect early glaucomatous damage and on the correlation between glaucomatous progression and RGC/GCC measurement by SD-OCT were reviewed.RESULTS: According to the literature, macular RGC/GCC SD-OCT has high diagnostic power of preperimetric glaucoma, reliable discrimination ability to differentiate between healthy eyes and glaucomatous eyes, with good correlation with visual filed damage. The current data suggests that it may serve as a sensitive detection tool for glaucomatous structural progression even with mild functional progression as the rate of change of RGC/GCC thickness was found to be significantly higher in progressing than in stable eyes. Glaucoma assessment with RGC/GCC SD-OCT was comparable with and sometimes better than circumpapillary retinal nerve fiber layer thickness measurement.CONCLUSION: An increasing body of evidence supports using macular RGC/GCC thickness as an indicator for early glaucoma. This might be a useful tool for monitoring disease progression.

Direct spectral domain decomposition method for 2D incompressible Navier-Stokes equations

An efficient direct spectral domain decomposition method is developed coupled with Chebyshev spectral approximation for the solution of 2D, unsteady and in- compressible Navier-Stokes equations in complex geometries. In this numerical approach, the spatial domains of interest are decomposed into several non-overlapping rectangu- lar sub-domains. In each sub-domain, an improved projection scheme with second-order accuracy is used to deal with the coupling of velocity and pressure, and the Chebyshev collocation spectral method （CSM） is adopted to execute the spatial discretization. The influence matrix technique is employed to enforce the continuities of both variables and their normal derivatives between the adjacent sub-domains. The imposing of the Neu- mann boundary conditions to the Poisson equations of pressure and intermediate variable will result in the indeterminate solution. A new strategy of assuming the Dirichlet bound- ary conditions on interface and using the first-order normal derivatives as transmission conditions to keep the continuities of variables is proposed to overcome this trouble. Three test cases are used to verify the accuracy and efficiency, and the detailed comparison be- tween the numerical results and the available solutions is done. The results indicate that the present method is efficiency, stability, and accuracy.

Agreement of angle closure assessments between gonioscopy, anterior segment optical coherence tomography and spectral domain optical coherence tomography

AIM: To determine angle closure agreements between gonioscopy and anterior segment optical coherence tomography(AS-OCT), as well as gonioscopy and spectral domain OCT(SD-OCT). A secondary objective was to quantify inter-observer agreements of AS-OCT and SD-OCT assessments.METHODS: Seventeen consecutive subjects(33 eyes)were recruited from the study hospital’s Glaucoma clinic.Gonioscopy was performed by a glaucomatologist masked to OCT results. OCT images were read independently by 2 other glaucomatologists masked to gonioscopy findings as well as each other’s analyses of OCT images.RESULTS: Totally 84.8% and 45.5% of scleral spurs were visualized in AS-OCT and SD-OCT images respectively(P 【0.01). The agreement for angle closure between AS-OCT and gonioscopy was fair at k =0.31(95% confidence interval, CI: 0.03-0.59) and k =0.35(95%CI: 0.07-0.63) for reader 1 and 2 respectively. The agreement for angle closure between SD-OCT and gonioscopy was fair at k =0.21(95% CI: 0.07-0.49) and slight at k =0.17(95% CI: 0.08-0.42) for reader 1 and 2 respectively. The inter-reader agreement for angle closure in AS-OCT images was moderate at 0.51(95% CI: 0.13-0.88). The inter-reader agreement for angle closure in SD-OCT images was slight at 0.18(95% CI: 0.08-0.45).CONCLUSION: Significant proportion of scleral spurs were not visualised with SD-OCT imaging resulting in weaker inter-reader agreements. Identifying other angle landmarks in SD-OCT images will allow more consistent angle closure assessments. Gonioscopy and OCT imaging do not always agree in angle closure assessments but have their own advantages, and should be used together and not exclusively.

用线性补偿算法和CCD响应补偿来提高频谱OCT图像质量

在频谱光学相干析成像(频谱OCT)系统中普遍使用的CCD采样的数据是波长的函数。CCD对不同波长的信号具有不同的响应,而且图像重建进行的傅里叶逆变换所需要的数据是波数的函数,忽略这两个问题对频谱OCT成像质量的影响比较大。基于以上分析,提出了响应度补偿法和波长数据-波数数据转换线性补偿法,并对样品进行了实验验证。实验结果表明,该方法能够将OCT图像的信噪比(SNR)提高约30%,明显改善了图像质量。

Choroidal Analysis of Polypoidal Choroidal Vasculopathy by Spectral Domain Optical Coherence Tomography

Purpose: This study was designed to measure the changes in the subfoveal choroidal thickness(SFCT) and choroidal maximal vessel diameter(MVD) of the affected and unaffected fellow eyes in patients with polypoidal choroidal vasculopathy(PCV) and compare them to healthy controls.Methods: In this cross-sectional observational clinical study,SFCT and MVD were measured in both eyes of 53 patients with unilateral PCV. PCV eyes were subgrouped into group A and unaffected fellow eyes into group B. All patients were diagnosed with PCV by fundus fluorescein angiography.(FFA)and indocyanine green angiography.(ICGA). Sixty age- and gender-matched healthy subjects were enrolled in the control group(group C).Results: No statistical difference was observed among groups in age and gender. Overall, SFCT was correlated with MVD in all subjects(P <0.001; correlation coefficient: 0.759). P values were < 0.001 with a correlation coefficient of 0.686,0.801, and 0.808 in groups A, B, and C, respectively. No statistical significance was noted in SFCT among groups A(266.45±99.51 μm),B(269.57 ± 105.10 μm),and C(243.83±99.68 μm)(P =0.335). However, the MVD in group A was(202.55±72.45 μm), significantly larger than that in group C(166.45 ±56.18 μm,P =0.008), while the MVD in group B(194.75±85.27 μm) was equally significantly greater than that in group C(166.45 ± 56.18 μm)(P=0.038).Conclusion: For both PCV patients and healthy subjects,SFCT was positively correlated with MVD. No statistical significance was noted in SFCT between PCV eyes and unaffected fellow / normal eyes. However, MVD was significantly larger in the PCV affected eyes than in unaffected fellow or normal control eyes, suggesting that MVD could be considered as a sensitive indicator to evaluate choroidal perfusion in PCV patients.

复谱频域OCT成像的研究

采用频域技术的OCT系统,深度扫描信息由背向散射光谱的傅立叶反变换获得,简化了轴向扫描过程,从而使快速OCT成像成为可能.为了实现复杂生物组织的OCT快速成像,消除谱频域OCT的"混叠"现象、重建样品的真实层析结构,本文引入了相移干涉技术,构建了一套满量程复谱频域OCT实验系统,并为系统设计了特殊的分束镜和移相器,为最终实现复杂生物组织的OCT快速成像提供了条件.

基于子谱分析的白光频域OCT

为了提高频域OCT系统轴向分辨率和信噪比,提出了一种采用白光光源的频域OCT系统,研究了所用的CCD相机的横向像素数、白光光源的光谱与系统轴向分辨率之间的关系,建立了一种基于子谱分析的白光频域OCT系统。通过选择所需的白光光源及其接收频段,既能保证最大探测深度和高轴向分辨率,又能提高信噪比。实验结果验证了所提出的光源的相干长度和系统及图像轴向分辨率测量方法,证明了白光频域OCT的可行性。

SD-OCT检测Nd∶YAG激光周边虹膜切除术后黄斑区视网膜厚度变化

目的:探讨Nd∶YAG激光周边虹膜切除术(LPI)对原发性闭角型青光眼(PACG)患者黄斑区视网膜厚度的影响。方法:前瞻性研究。选取2019-10/2021-10我院PACG患者30例30眼为PACG组,同期健康体检者20名20眼为正常对照组(随机选取一眼)。PACG组患者接受LPI治疗,术后随访1mo。两组受试者均行最佳矫正视力(BCVA)、眼压、角膜内皮细胞、IOL Master 500光学测量仪测量前房深度(ACD)及眼轴长度(AL)、频域光学相干断层扫描(SD-OCT)检查黄斑区视网膜厚度。比较两组受试者及PACG组患者LPI前后ACD、眼压、AL和黄斑区视网膜厚度,并行相关性分析。结果:PACG组患者术后1wk, 1mo ACD较术前变深(均P<0.05)。PACG组患者手术前后眼压和AL均无差异(均P>0.05)。PACG组患者术前黄斑中心区,内外环上方、颞侧、下方、鼻侧,共9个区域视网膜厚度分别为243.50±13.24、324.50±13.46、308.83±15.94、310.00±14.24、314.50±16.29、300.67±19.95、290.17±12.58、302.40±16.37、307.33±14.84μm,正常对照组相应部位分别为266.14±16.16、342.67±15.86、327.95±16.41、337.85±13.03、341.24±15.58、313.76±17.59、290.24±16.29、303.81±13.91、323.01±14.80μm,两组间中心区、内环上方、颞侧、下方、鼻侧比较均有差异(均P<0.05)。PACG组术后1wk黄斑区9个区域视网膜厚度分别与术前相比均增加,术后1mo接近术前水平,但手术前后各分区比较均无差异(均P>0.05)。结论:与正常受试者比较,PACG患者黄斑区视网膜厚度较薄。PACG患者LPI术后早期黄斑区视网膜可变厚。

三维频域OCT在鉴别诊断黄斑裂孔中的分析应用

目的:三维频域OCT鉴别黄斑全层裂孔,板层裂孔,假性黄斑裂孔。方法:对53例58眼临床直接或间接眼底镜及三面镜检查疑似或诊断为黄斑裂孔者进行3D频域OCT及2D-OCT,或FFA鉴别分析。结果:本组病例使用3D频域OCT的诊断符合率为100%。结论:三维频域OCT可直观的显示黄斑裂孔的三维结构,对不同类别黄斑裂孔视网膜神经纤维层,感光细胞层,视网膜色素上皮层厚度进行更准确的测量,全面直观的观察不同类别黄斑裂孔的病变层次和病理形态学变化,极大地提高了诊断鉴别的准确性和工作效率。

频域OCT测量正常学龄期儿童黄斑区视网膜厚度

目的应用频域OCT测量正常学龄期儿童的黄斑区视网膜厚度。方法选取6~12岁儿童108人,以最佳矫正远视力≥1.0、最佳矫正近视力Jr1、球镜屈光度范围(-1.00^+1.00 D)、柱镜屈光度范围(-1.00^+1.00 D)为纳入标准,最终选取213眼。应用Cirrus HD-OCT的200×200扫描模式和512×218扫描模式对受试者双眼黄斑区视网膜进行检查,测量黄斑中心视网膜厚度(central subfield thickness,CST)、黄斑区视网膜容积(macular volume,MV)、黄斑区平均视网膜厚度(average macular thickness,AMT)及九分区模式视网膜厚度。结果两种扫描模式下黄斑区视网膜厚度值差异均无统计学意义(均为P>0.05)。左右眼差异无统计学意义(均为P>0.05)。男童CST(240.68±16.57)μm厚于女童(234.51±18.65)μm(P=0.040),且男童内环各分区视网膜厚度均厚于女童(均为P<0.05)。结论本研究应用HD-OCT测量正常儿童AMT,为确定国人学龄期儿童AMT正常值及疾病诊断提供参考,提示临床注意性别差异。

Oct-4/Sox-2协同调控下游基因表达的分子机制

Oct-4属POU家族蛋白,是一类在动物早期胚胎发育过程中起重要作用的转录因子,参与维持细胞的全能性及未分化状态。Oct-4蛋白的主要结构特征为具有POU家族特有的保守结构域(POUS)和POU同源异型结构域(POUHD),这两个结构域可与DNA上特定区域形成双向结合,进而对基因转录进行调控。Sox-2是另一种转录因子,其HMG结构域可结合在DNA的特定序列上,并可通过与Oct-4的POUs结构域之间的蛋白质-蛋白质相互作用形成POU/HMG/DNA三元复合体以调控下游靶基因的表达。文章就POU家族成员Oct-4和HMG-box家族成员Sox-2在动物早期胚胎发育中调控部分下游基因表达的分子机制进行了概述。

在CSOCT系统中抑制线性相移误差的校正算法

从理论上详细分析了经典相移算法对线性相移误差的敏感度,用频域和空域两种分析方法对定步长算法抑制线性相移误差的能力进行了分析。建立了含有线性相移误差复频域OCT空域分析法的仿真模型,并对测试样品进行了实验。实验结果表明,五帧相移算法对真实层析结构影响小,对镜像尾迹有完全的抑制作用,能够真正地实现100%的全量程的有效探测。