Optical coherence tomography enhanced depth imaging of chorioretinal folds in patients with orbital tumors

AIM:To characterize spectral-domain optical coherence tomography(SD-OCT)features of chorioretinal folds in orbital mass imaged using enhanced depth imaging(EDI).METHODS:Prospective observational case-control study was conducted in 20 eyes of 20 patients,the uninvolved eye served as a control.All the patients underwent clinical fundus photography,computed tomography,EDI SDOCT imaging before and after surgery.Two patients with cavernous hemangiomas underwent intratumoral injection of bleomycin A5;the remaining patients underwent tumor excision.Patients were followed 1 to 14mo following surgery(average follow up,5.8mo).RESULTS:Visual acuity prior to surgery ranged from 20/20 to 20/200.Following surgery,5 patients’visual acuity remained unchanged while the remaining 15 patients had a mean letter improvement of 10(range 4 to 26 letters).Photoreceptor inner/outer segment defects were found in 10 of 15 patients prior to surgery.Following surgical excision,photoreceptor inner/outer segment defects fully resolved in 8 of these 10 patients.CONCLUSION:Persistence of photoreceptor inner/outer segment defects caused by compression of the globe by an orbital mass can be associated with reduced visual prognosis.Our findings suggest that photoreceptor inner/outer segment defects on EDI SD-OCT could be an indicator for immediate surgical excision of an orbital mass causing choroidal compression.

Optical coherence tomography with or without enhanced depth imaging for peripapillary retinal nerve fiber layer and choroidal thickness

AIM：To assess peripapillary retinal nerve fiber layer（RNFL）and choroidal thickness obtained with enhanced depth imaging（EDI）mode compared with those obtained without EDI mode using Heidelberg Spectralis optical coherence tomography（OCT）.METHODS：Fifty eyes of 25 normal healthy subjects and32 eyes of 20 patients with different eye diseases were included in the study.All subjects underwent 3.4 mm diameter peripapillary circular OCT scan centered on the optic disc using both the conventional and the EDI OCT protocols.The visualization of RNFL and choroidoscleral junction was assessed using an ordinal scoring scale.The paired t-test,intraclass correlation coefficient（ICC）,95%limits of agreement（LoA）,and Bland and Altman plots were used to test the agreement of measurements.RESULTS：The visibility score of RNFL obtained with and without EDI was of no significant difference（P=0.532）,the visualization of choroidoscleral junction was better using EDI protocol than conventional protocol（P〈0.001）.Peripapillary RNFL thickness obtained with EDI was slightly thicker than that obtained without EDI（103.25±9.42μm vs 101.87±8.78μm,P=0.010）.The ICC of the two protocols was excellent with the value of 0.867 to 0.924,the 95%LoA of global RNFL thickness was between-10.0 to 7.4μm.Peripapillary choroidal thickness obtained with EDI was slightly thinner than that obtained without EDI（147.23±51.04μm vs 150.90±51.84μm,P〈0.001）.The ICC was also excellent with the value of 0.960 to 0.987,the 95%LoA of global choroidal thickness was between-12.5 to 19.8μm.CONCLUSION：Peripapillary circular OCT scan with or without EDI mode shows comparable results in the measurement of peripapillary RNFL and choroidal thickness.

Standardization of choroidal thickness measurements using enhanced depth imaging optical coherence tomography

AIM: To describe and evaluate a standardized protocol for measuring the choroidal thickness(Ch T) using enhanced depth imaging optical coherence tomography(EDI OCT).METHODS: Single 9 mm EDI OCT line scans across the fovea were used for this study. The protocol used in this study classified the EDI OCT images into four groups based on the appearance of the choroidal-scleral interface and suprachoroidal space. Two evaluation iterations of experiments were performed: first, the protocol was validated in a pilot study of 12 healthy eyes. Afterwards, the applicability of the protocol was tested in 82 eyes of patients with diabetes. Inter-observer and intra-observer agreements on image classifications were performed using Cohen’s kappa coefficient(κ). Intraclass correlation coefficient(ICC) and Bland-Altman’s methodology were used for the measurement of the Ch T.RESULTS: There was a moderate(κ=0.42) and perfect(κ =1) inter- and intra-observer agreements on image classifications from healthy eyes images and substantial(κ =0.66) and almost perfect(κ =0.86) agreements from diabetic eyes images. The proposed protocol showed excellent inter- and intra-observer agreements for the Ch T measurements on both, healthy eyes and diabetic eyes(ICC 】0.90 in all image categories). The Bland-Altman plot showed a relatively large Ch T measurement agreement in the scans that contained less visible choroidal outer boundary. CONCLUSION: A protocol to standardize Ch T measurements in EDI OCT images has been developed;the results obtained using this protocol show that the technique is accurate and reliable for routine clinical practice and research.

Peripapillary choroidal thickness in Chinese children using enhanced depth imaging optical coherence tomography

AIM：To evaluate the peripapillary choroidal thickness（PPCT） in Chinese children,and to analyze the influencing factors.METHODS： PPCT was measured with enhanced depth imaging optical coherence tomography（EDI-OCT） in 70children（53 myopes and 17 non-myopes） aged 7 to 18 y,with spherical equivalent refractive errors between 0.50and-5.87 diopters（D）.Peripapillary choroidal imaging was performed using circular scans of a diameter of 3.4 mm around the optic disc.PPCT was measured by EDI-OCT in six sectors： nasal（N）,superonasal（SN）,superotemporal（ST）,temporal（T）,inferotemporal（IT）and inferonasal（IN）,as well as global RNFL thickness（G）.RESULTS： The mean global PPCT was 165.49±33.76 μm.The temporal,inferonasal,inferotemporal PPCT were significantly thinner than the nasal,superonasal,superotemporal segments PPCT were significantly thinner in the myopic group at temporal,superotemporal and inferotemporal segments.The axial length was significantly associated with the average global（β=-0.419,P =0.014）,superonasal（β=-2.009,P=0.049） and inferonasal（β=-2.000,P=0.049） PPCT.The other factors（gender,age,SE） were not significantly associated with PPCT.CONCLUSION： PPCT was thinner in the myopic group at temporal,superotemporal and inferotemporal segments.The axial length was found to be negatively correlated to PPCT.We need more further studies about the relationship between PPCT and myopia.

Detecting early changes in choroidal vascularity and thickness using optical coherence tomography in patients with corneal crosslinking for keratoconus

AIM:To investigate changes in choroidal thickness and vascularity in keratoconus patients treated with corneal crosslinking.METHODS:This study evaluated 28 eyes of 22 patients with keratoconus who underwent corneal crosslinking.The choroidal thicknesses were evaluated on enhanced depth imaging optical coherence tomography at the preoperative and postoperative 3d,1,and 3mo.Choroidal thickness in the four cardinal quadrants and the fovea were evaluated.The choroidal vascularity index was also calculated.RESULTS:There was no significant difference in central choroidal thickness between the preoperative and postoperative 3d,1mo(P>0.05).There was a significant increase in the 3mo(P=0.034)and a significant decrease in the horizontal choroidal vascularity index on the postoperative 3d(P=0.014),there was no statistically significant change in vertical axes and other visits in horizontal sections(P>0.05).CONCLUSION:This study sheds light on choroidal changes in postoperative corneal crosslinking for keratoconus.While it suggests the procedure’s relative safety for submacular choroid,more extensive research is necessary to confirm these findings and their clinical significance.

IMAGE IMPROVEMENT IN THE WAVELET DOMAIN FOR OPTICAL COHERENCE TOMOGRAMS

In this paper,an image processing method for improving the quality of optical coherence tomography(OCT)images is proposed.Wavelet denoising based on context modeling and contrast enhancement by means of the contrast measure in the wavelet domain is carried out on the OCT images in succession.Three parameters are selected to assess the effectiveness of the method.It is shown from the results that the proposed method can not only enhance the contrast of images,but also improve signal-to-noise ratio.Compared with two other typical algorithms,it has the best visual effect.

Numerical Optimization of Sensitivity in Fourier Domain Optical Coherence Tomography

The details of crosssectional images based on Fourier domain optical coherence tomography play an important role that is limited to nonuniform sampling,spectral dispersion,inverse discrete Fourier transform(IDFT),and noise.In this section,we propose a method for emphasizing axial details to the greatest extent possible.After removing spectral dispersion,uniform discretization in the wavenumber domain is performed based on two interferograms via a specified offset in depth,with no spectrum calibration.The sampling number in IDFT is optimized to improve axial sensitivity up to 1.62 dB.The proposed process has the advantage of being based on numerical computation rather than hardware calibration,which benefits cost,accuracy,and efficiency.

谱域光学相干层析系统深度扩展技术研究

对谱域光学相干层析系统(SD-OCT)进行成像深度扩展,能清晰地探测到更深层次的样品信息。提出结合去除复共轭镜像和焦平面叠加的方法来提高探测深度。首先通过光束偏移振镜中心,对样品添加载波频率,基于希尔伯特变换滤除负频信号,去除复共轭镜像,再对样品不同深度聚焦成像,实现聚焦平面的叠加,最终扩展成像深度。基于去复共轭成像系统测量不同样品的图像,验证了该方法的有效性和可靠性。针对透明片材料,系统有效成像范围扩大一倍,从1.97 mm达到3.94 mm,针对结肠组织,有效成像深度从0.51 mm扩展到0.65 mm。结果表明,深度扩展技术能够提升成像范围,同时也突破了焦深限制,样品深层结构信息也清晰可见。

计算增强光学相干层析成像技术研究进展

光学相干层析成像(Optical coherence tomography,OCT)作为一种重要的无损断层三维成像技术,应用场景广泛。不断发展的场景需求对OCT技术的性能提出了新的要求,包括分辨率提升、焦深解耦、像差校正及分辨率各向异性改善等。在过去的十几年内,一系列基于计算成像的方法被证明能有效实现上述性能提升。本文围绕上述OCT成像4个性能提升需求,总结综述了代表性的计算成像方法。分析对比了相应计算成像方法之间的优劣,并对未来发展趋势进行展望,旨在为计算成像方法在OCT领域的进一步研究与应用提供参考。

多尺度Retinex的光学相干层析图像增强研究

针对光衰减导致光学相干层析图像局部图像对比度下降的问题,提出了基于多尺度Retinex的光学相干层析图像增强方法。采用图像光照补偿的方法完成光学相干层析图像增强,选取多尺度Retinex算法在三个尺度条件下确定高斯滤波系数;利用高斯滤波系数对光学相干层析图像实施卷积处理,对灰度值结果实施加权平均处理,并采用分段线性平移与压缩方法对加权后灰度值实施映射,实验结果显示该方法可显著提升图像的颜色与对比度质量,有效解决了后向散射的问题,获取较好的光学相干层析增强效果。

深度学习在脉络膜分割中的应用研究进展

近年来,眼科作为高度依赖辅助成像的医学领域之一,一直处于深度学习算法应用的前沿。脉络膜的形态变化与眼底疾病的发生、发展以及治疗预后密切相关。光学相干断层扫描的快速发展极大地促进了对脉络膜形态和结构的精确分析。脉络膜分割及相关分析对于确定眼病的发病机制和治疗策略至关重要,然而,目前脉络膜主要依赖于繁琐、耗时和重复性低的人工手动分割。为了克服这些困难,近年来开发了用于脉络膜分割的深度学习方法,极大地提高了脉络膜分割的准确性和效率。本文旨在回顾不同眼病中脉络膜厚度的特征,探讨深度学习模型在测量脉络膜厚度中的最新应用及其优势,同时关注深度学习模型面临的挑战。

急性原发性闭角型青光眼首次发作后1年内视盘周围脉络膜厚度的变化

目的:探讨急性原发性闭角型青光眼(APACG)首次发作后1a内视盘周围脉络膜厚度(pCT)的变化规律。方法:前瞻性队列研究。选取2015-10/2019-09于石家庄市人民医院眼科诊治的APACG患者31例(发作眼组31眼,对侧临床前期眼组31眼),正常对照组30例30眼,三组均在APACG发作期,术后1wk,1、3、6mo,1a测量pCT。结果:发作眼组pCT在术后1wk时比发作期增厚,之后1a内持续变薄(P<0.05)。发作眼组pCT较其余两组:在发作期,术后1wk时增厚,1a时变薄(P<0.05)。发作眼组发作期平均pCT与高眼压持续时间正相关,与前房深度负相关(P<0.05)。结论:首次发作的APACG患者,pCT在发作期和术后1wk弥漫增厚,1mo恢复正常,1a时变薄。发作期平均pCT与高眼压持续时间正相关,脉络膜厚度在APACG的发作中可能有重要作用。

脉络膜厚度和血管密度与糖尿病视网膜病变严重程度的相关性

目的探讨脉络膜厚度和血管密度与糖尿病视网膜病变(DR)严重程度的相关性。方法回顾性病例研究。选择2018年8月至2021年8月入我院收治2型糖尿病共96例(192只眼),根据国际临床糖尿病视网膜病变(DR)分为非DR患者24只眼、非增生期DR患者133只眼和增生期非DR患者35只眼,其中非增生期又分为轻度40只眼、中度57只眼和重度36只眼。采用频域相干光层析深度增强成像术(EDI-OCT)定量检测黄斑中心凹视网膜和脉络膜厚度、视网膜和脉络膜血管密度、脉络膜总面积和血管区面积,并计算血管指数。结果视网膜厚度和血管密度比较发现,非增生期和增生期患眼明显低于正常眼(P<0.05),非增生期与增生期、非增生期不同分级间比较,差异无统计学意义(P>0.05)。脉络膜厚度、血管密度和血管指数比较发现,非增生期患眼明显低于正常眼,增生期明显低于非增生期(P<0.05),并且非增生期中度患眼明显低于轻度,重度明显低于中度(P<0.05);但是各组间脉络膜总面积和血管区面积比较差异无统计学意义(P>0.05)。结论EDI-OCT定量检测黄斑中心凹脉络膜厚度、血管密度和血管指数对于评估DR患眼的严重程度有较好的准确性和应用价值。

基于图像像素点分析的EDI-OCT测量脉络膜厚度研究

目的使用增强型深度成像OCT(EDI-OCT)以基于图像像素点的方式实现脉络膜厚度的测量。方法通过EDI-OCT获得50名受试者的脉络膜图像,利用OCT软件自动识别脉络膜前界,通过软件工具描绘脉络膜后界。在黄斑中心凹及其两侧每隔500μm共设7个特殊点,手工测量各点处脉络膜厚度。两研究者用自建程序根据像素点及比例尺计算脉络膜厚度,分析两研究者的相关系数,并对比两种方法的测量结果。结果水平方向脉络膜:受试者在基于像素点的新方法测量的7点平均脉络膜厚度(m7)为(248.98±81.48)μm,手工测量的m7为(244.06±81.09)μm,两者差值为4.92μm,水平方向的所有像素点平均脉络膜厚度(m)为(249.48±76.61)μm。垂直方向脉络膜新方法测量的m7为(259.96±72.47)μm,手工测量的m7为(256.40±71.81)μm,两者差值为3.57μm垂直方向的m为(260.47±77.01)μm。两位研究者之间的ICC值为0.991,其95%可信区间为0.986~0.994。两种方法测量的所有特殊位置的脉络膜厚度差异均无统计学意义(均P>0.05),各个位置的测量差值在2.54~8.03μm。结论本研究方法测量脉络膜厚度的准确性及可重复性高,可通过SD-OCT实现测量更易应用于临床和研究。

成年高度近视患者脉络膜厚度及其相关影响因素分析

背景 高度近视的多种眼底并发症均与眼轴增长引起的眼球壁厚度改变有关,但成年人高度近视眼脉络膜厚度与眼轴长度的量化分析研究较少见. 目的 观察成年高度近视患者脉络膜厚度的改变,并分析脉络膜厚度与眼轴长度、年龄及屈光度的关系.方法 采用前瞻性队列研究方法,纳入2012年12月至2013年5月在武汉大学人民医院就诊的成年高度近视患者75例75眼作为高度近视组,纳入同期年龄和性别相匹配的健康志愿者70例70眼作为正常对照组.采用频域光学相干断层扫描（SD-OCT）的加强深度扫描（EDI）技术,以6 mm的扫描线对黄斑部进行0±176;扫描,测量黄斑中心凹下及由中心凹向鼻侧和颞侧2 500 μm的脉络膜厚度值,共测量11个子午线,每个子午线间隔500 μm,比较两个组间脉络膜厚度和眼轴长度的差异,分析脉络膜厚度与眼轴长度、年龄及屈光度的关系.结果 高度近视组受检眼中心凹下脉络膜厚度值和平均黄斑部脉络膜厚度值分别为（146±177;52） μm和（142±177;63） μm,正常对照组分别为（306±177;60） μm和（271 ±177;71） μm,两个组间差异均有统计学意义（t=-17.130,P=0.000;t=-15.890,P=0.000）.高度近视组颞侧脉络膜最厚,中心凹下厚度次之,鼻侧最薄,而正常对照组以中心凹旁脉络膜最厚,其次为颞侧,鼻侧最薄.高度近视组受检眼各检测点脉络膜均薄于正常对照组.高度近视组患者脉络膜厚度值与眼轴长度呈明显负相关（r=-0.580,P=0.000）,眼轴长度每增加l mm,脉络膜厚度值平均减少17.943 μm. 结论 SD-OCT检测显示,成年高度近视患者脉络膜厚度较健康人明显变薄,且与眼轴长度的变化关系密切,提示脉络膜的病理改变可能在高度近视眼并发症的发生过程中发挥作用.

视网膜脱离成功复位1年以上患眼低视力与黄斑区脉络膜厚度的关系

目的使用深部增强成像频域光学相干断层扫描(enhanced depth imaging spectral domain optical coherence tomography,EDI SD-OCT)观察孔源性视网膜脱离成功复位1 a以上低视力患眼黄斑中心凹下脉络膜厚度(subfoveal choroidal thickness,SFCT),分析其与低视力的关系。方法将南昌爱尔眼科医院2010年1月到2014年3月孔源性视网膜脱离成功复位术后1 a以上最佳矫正视力(best corrected visual acuity,BCVA)<0.3的患者72例(72眼)纳入研究。行双眼BCVA及EDI SD-OCT扫描SFCT检查。分析患眼与对侧健眼术后末次随访的BCVA与SFCT的相关性。结果患眼术后末次随访SD-OCT检查显示,72眼中,黄斑中心凹正常者3眼(4.2%);外层视网膜微结构异常者69眼(95.8%)。患眼术后末次随访BCVA,转换为5分记录视力为3.59±0.51,同期健眼为4.94±0.11;患眼术后末次随访SFCT为(164.47±62.95)μm,对侧健眼SFCT为(235.47±42.40)μm;患眼与对侧健眼术后末次随访BCVA、SFCT差异均有统计学意义(均为P<0.05)。患眼术后末次随访BCVA与SFCT有相关性(P<0.05)。患眼黄斑区外层视网膜微结构异常眼与正常眼的BCVA、SFCT差异均无统计学意义(均为P>0.05)。结论孔源性视网膜脱离成功复位术后1 a以上低视力眼的SFCT薄,且与BCVA存在相关性;其视力的恢复可能要晚于EDI SD-OCT下观察到的外层视网膜微结构的恢复。

应用多级维纳滤波的OCT图像除噪方法

设计了基于维纳滤波和对比度增强的OCT图像处理方法。对OCT图像的噪声进行了分析，通过多尺度维纳滤波器对图像进行滤波处理来去除噪声干扰，然后根据区域特性采用对比度增强方法提高图像对比度。实验结果表明：经该方法处理后图像的背景方差（BV）较原始图像降低了2～6倍，细节方差和背景方差之比（DV／BV）提高了2～5倍。该方法不仅有效地去除了OCT图像的噪声，而且视觉效果良好，是一种有效的图像后处理方法。

脉络膜厚度在糖尿病视网膜病变诊疗中的重要价值

糖尿病视网膜病变是糖尿病导致的视网膜微血管损害所引起的一系列典型病变,严重影响工作人群视力及生活质量。频域光相干断层扫描技术的发展为阐述糖尿病眼底疾病的发病机制提供了新途径。本文将针对频域光相干断层扫描测量的脉络膜厚度与糖尿病视网膜病变诊疗关系最新研究进行综述。

青少年高度近视眼的脉络膜厚度改变

目的比较青少年高度近视眼与正常眼的脉络膜厚度的差异,分析脉络膜厚度变化与青少年高度近视的关系。方法选取2014年2月至2014年8月在我院眼视光中心就诊和体检的青少年62例111眼,年龄为13~17（14.34±2.74）岁。分为高度近视组32例57眼,正常对照组30例54眼,高度近视组屈光度（-6.85±1.14）D,眼轴（26.31±1.13）mm。正常对照组屈光度（-0.37±0.85）D,眼轴（23.91±0.64）mm。两组间的屈光度、眼轴差异均有统计学意义（P〈0.001）。采用频域光学相干断层扫描的加强深度扫描技术对黄斑部进行0°扫描,测量黄斑中心凹下及由中心凹向鼻侧和颞侧3000μm的脉络膜厚度值,共测量13个子午线,每个子午线间隔500μm,比较两组间脉络膜厚度、屈光度和眼轴,分析脉络膜厚度变化与青少年高度近视的关系。结果青少年高度近视组受检眼黄斑中心凹下脉络膜厚度值和黄斑部脉络膜平均厚度值分别为（220.4±49.6）μm和（209.9±62.8）μm,正常对照组分别为（347.4±63.6）μm和（295.1±71.2）μm,两组间差异均有统计学意义（t=-17.220,P=0.000;t=-16.180,P=0.000）。青少年高度近视组颞侧脉络膜最厚,中心凹下厚度次之,鼻侧最薄;而正常对照组以黄斑中心凹区域脉络膜最厚,其次为颞侧,鼻侧最薄。高度近视组受检眼各检测点脉络膜均薄于正常对照组。两组脉络膜厚度的差异黄斑中心凹区域较黄斑周边区域明显（P〈0.001）。结论青少年高度近视患者脉络膜厚度较青少年正常眼明显变薄,以黄斑中心凹区域的差异显著。提示脉络膜的厚度改变可能在青少年高度近视眼的发生过程中发挥作用。

青少年屈光不正人群中脉络膜厚度的研究

目的 研究青少年屈光不正患者的脉络膜厚度的特点及其与屈光度、眼轴长度等因素的相关性。方法 随机对在屈光门诊完成验光的5∽18岁屈光不正青少年进行了脉络膜厚度和眼轴长度的测量。最终51例102眼患者纳入研究。使用海德堡频域OCT的增强深度成像模式对每眼进行经黄斑中心凹水平方向线性扫描。分别测量该扫描线上5个位点的脉络膜厚度。应用IOL master测量眼轴长度。结果 51例患者年龄为（10.04±2.78）岁,屈光度为（-1.61±1.82）D,眼轴长度为（24.14±1.14）mm。扫描线上脉络膜厚度由颞侧向鼻侧逐渐变薄。屈光度与眼轴长度呈显著负相关（R2=0.562）,各位点的脉络膜厚度均与屈光度呈显著正相关（P〈0.01）,与眼轴长度则呈显著负相关（P〈0.05）,中心凹鼻侧1 mm处相关性最高。中心凹下的脉络膜厚度与年龄呈显著负相关。结论 后极部脉络膜厚度的改变可能在屈光度及眼轴长度改变相关的病理生理变化中起到重要的作用。