Spectral- and time-domain optical coherence tomography measurements of macular thickness in normal eyes and in eyes with diabetic macular edema

Purpose

To report macular thickness values in normal eyes and eyes with diabetic macular edema (DME) using time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT), and to derive a conversion equation.

Methods

The index study was a prospective investigation conducted on 80 eyes from 40 normal subjects and 130 eyes from 118 patients with DME seen in our clinic. Retinal thickness values from the central 1 mm of the macula and surrounding four ETDRS subfields were acquired using TD-OCT (Stratus OCT) and SD-OCT (SPECTRALIS HRA+OCT). Measurements of the central (C) subfield from both devices were used to derive a conversion equation. The equation was used to predict SD-OCT values using measurements from TD-OCT. Agreement between predicted and actual SD-OCT measurements was assessed.

Results

In normal eyes, the mean difference between TD-OCT and SD-OCT measurements of the C subfield was 76 μm (CI₉₅=74 and 77, respectively). The conversion equation, y=1.029x+72.49, was derived. In eyes with DME, using the equation, SPECTRALIS-predicted values were 5% higher than actual measurements, with 95% of predicted values falling within 9% of the actual measurements. Relocating SD-OCT grids to match the location on TD-OCT resulted in predicted values falling within 7% of actual measurements.

Conclusions

The percent difference between actual thickness measurements from SPECTRALIS and predicted thickness measurements, using the conversion equation, was within reported limits of repeatability of Stratus in eyes with DME. Our equation may help correlate OCT values from both devices in standard care and clinical trials for DME.     

黄斑视网膜前膜光学相干断层扫描观察及与其他检查的对比

目的应用光学相干断层扫描（Optical Coherence Tomography,OCT）观察黄斑视网膜前膜的形态。方法应用光学相干断层扫描仪观察黄斑视网膜前膜的形态150例。海德堡视网膜断层扫描仪（Heidelberg Retina Tomography,HRT-Ⅱ）黄斑模块检查30例,部分眼作了荧光造影,部分眼做了玻璃体切除术和视网膜前膜剥离术,术前术后均做了OCT检查观察手术效果。同时用OCT测量前膜厚度及黄斑中心凹的厚度。结果1.150例中男性56例,女性94例.年龄27～85岁,平均（65.76±9.46）岁。右眼65例,左眼85例。视网膜前膜的形态有以下几种：①黄斑部视网膜增厚,表面有膜形成,牵拉视网膜形成皱褶。视网膜内形成大小不同的液腔。②视网膜表面可清晰看见膜的反射面,有的局限增厚呈块状突起于视网膜表面,视网膜受牵拉弥漫增厚。视网膜内囊腔形成。③黄斑中心凹形成假孔或板层孔,孔的边缘锐利,孔的底部尚有部分神经组织残留或孔的表面被膜掩盖。④因膜的牵拉视网膜内形成大的解离腔。⑤视网膜厚度没有明显变化,仅见视网膜表面不平呈锯齿样改变,中心凹曲线变平。2.150例检查了视网膜前膜的厚度,最厚的膜为269μm,最薄的膜为46μm。平均膜厚度为（84.40±41.42）μm。3.前膜黄斑中心增厚,150例检查了黄斑中心厚度,中心厚度范围为107～780μm。平均（341.08±137.15）μm。正常黄斑中心厚度为（155±28.21）μm。结论光学相干断层扫描技术是非侵入性,安全,可靠,是精确测量前膜厚度的一种好方法.可用来鉴别黄斑裂孔和假孔及黄斑水肿。作为术前预测手术效果和观察术后黄斑组织恢复情况的手段。通过OCT及HRT-Ⅱ对视网膜前膜的对比观察,发挥各自的优势,提高早期前膜的检出率。     

Discrimination between normal and glaucomatous eyes using Stratus optical coherence tomography in Taiwan Chinese subjects

Background We differentiated between normal and glaucomatous eyes in the Taiwan Chinese population based solely on the quantitative assessment of summary data reports from Stratus optical coherence tomography (OCT) by comparing their area under the receiver operating characteristic (ROC) curve.Methods One randomly selected eye from each of the 62 patients with early glaucomatous damage (mean deviation –2.8 ± 1.8 dB) and from each of the 62 age- and sex-matched normal individuals were included in the study. Measurements of glaucoma variables (retinal nerve fiber layer thickness and optic nerve head analysis results) were obtained by Stratus OCT. Twenty-one OCT parameters were included in a linear discriminant analysis (LDA) using forward selection and backward elimination to determine the best combination of parameters for discriminating between glaucomatous and healthy eyes based on ROC curve area.Results The average RNFL thickness was the best individual parameter for differentiating between normal eyes and glaucomatous eyes (ROC curve area 0.793). The maximum area under the ROC curve of six input parameters (average RNFL thickness; 10, 11, and 12 oclock segment thicknesses; cup area; and vertical integrated rim area) generated by the forward selection method was 0.881. Whereas the maximum area under the ROC curve of 15 input parameters (average RNFL thickness; 1, 3, 4, 6, 8–10, 12 oclock segment thicknesses; vertical integrated rim area; horizontal integrated rim area; disc area; cup to disc area ratio; cup to disc horizontal ratio; and cup to disc vertical ratio) generated by backward elimination method was 0.929.Conclusions The performance of individual parameters obtained from Stratus OCT is fairly reliable for differentiating the early glaucomatous eyes from normal eyes. However, the discriminant power increases when LDA with forward selection and backward elimination methods is applied.     

Comparison of choroidal vessel thickness in children and adult eyes by enhanced-depth imaging optical coherence tomography imaging

AIM: To evaluate choroidal thickness, medium choroidal vessel thickness (MCVT) and large choroidal vessel thickness (LCVT) in normal children and adult subjects. METHODS: Manual measurements of subfoveal choroidal thickness (SFCT), MCVT and LCVT at subfoveal and 750 μm nasal and temporal to fovea locations were completed on enhanced-depth imaging optical coherence tomography (EDI-OCT) scans of normal children and adult subjects. RESULTS: Fifty adult and fifty-seven child subjects were included in the study (including 80 adult and 103 child eyes). Mean (±SD) SFCT of adult and children eyes in the study was 309.3±95.7 μm and 279.3±50.4 μm respectively. SFCT and subfoveal MCVT in adult eyes were significantly more than children (P=0.01 and P≤0.0001 respectively). CONCLUSION: There is choroidal thickening with associated thickening of medium choroidal vessels in adults, suggesting that there is alteration in choroidal vasculature with ageing.     

新型SS-OCT与Scheimpflug眼前节分析仪测量年龄相关性白内障患者角膜屈光力及散光的一致性

目的：探讨年龄相关性白内障患者应用新型扫频源光学相干断层扫描仪(SS-OCT)与Scheimpflug眼前节分析仪测量角膜屈光力、角膜散光的Bland-Altman分析。

方法：选取2021-01/12我院收治的年龄相关性白内障患者177例282眼。分别采用SS-OCT与Scheimpflug眼前节分析仪测量角膜前表面、后表面、全角膜的陡峭轴屈光力(Ks)、平坦轴屈光力(Kf)、平均角膜屈光力(Km)、角膜散光、散光轴向。所有参数进行配对样本t检验、组内重复性检验、Pearson相关性和Bland-Altman一致性分析。

结果：SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面屈光力Ks、Kf、Km均无差异(P>0.05)。Scheimpflug眼前节分析仪测量的角膜后表面以及全角膜屈光力Ks、Kf、Km均大于SS-OCT测量值(P<0.05)。SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面、角膜后表面以及全角膜的散光度数和轴向均无差异(P>0.05)。所有参数的组内相关系数(ICC)均大于0.88,提示组内重复性较好。SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面、角膜后表面以及全角膜的Ks、Kf、Km、散光度数和轴向均呈正相关(P<0.05)。Bland-Altman一致性分析显示,SS-OCT与Scheimpflug眼前节分析仪测量的角膜前表面、角膜后表面以及全角膜的Ks、Kf、Km、散光度数和轴向的一致性较好(P<0.05)。

结论：新型SS-OCT与Scheimpflug眼前节分析仪测量的角膜屈光力、角膜散光参数具有高度一致性,可适用于年龄相关性白内障患者角膜屈光力及角膜散光的诊断。     

应用三维光学相干断层扫描仪对原发性开角型青光眼和正常眼脉络膜厚度的对比分析

目的　通过三维光学相干断层扫描仪比较原发性开角型青光眼（primary open-angle glaucoma,POAG）和正常眼的脉络膜厚度,并分析其影响因素,探讨脉络膜厚度与青光眼的关系。方法　选取140例（216眼）POAG患者作为青光眼组,67例（106眼）正常受试者作为正常组。采用日本Topcon公司生产的超景深广角眼底断层扫描仪对各组受试者脉络膜厚度进行检测。通过单变量和多变量回归分析受试者年龄、眼轴长度、角膜厚度、收缩压、舒张压、收缩期灌注压、舒张期灌注压、眼压以及视野缺损值等因素与脉络膜厚度的关系。结果　青光眼组受试者年龄、眼轴长度、收缩压、收缩期灌注压均高于正常组（均为P<0.05）;青光眼组受试者视野损害更严重,视野缺损值差异有统计学意义（P<0.001）;两组受试者角膜厚度、舒张压、眼压、舒张期灌注压差异均无统计学意义（均为P>0.05）;青光眼组受试者脉络膜厚度为（157.70±48.54）μm,正常组为（179.90±36.10）μm,差异有统计学意义（P<0.001）。对所有受试者脉络膜厚度与各因素进行单变量回归分析,结果提示脉络膜厚度与年龄、眼轴长度、是否青光眼均呈显著负相关（均为P<0.05）。在考虑年龄和眼轴长度等因素在内的多变量回归分析结果显示,当年龄和眼轴长度被矫正时,青光眼组与正常组之间的脉络膜厚度差异无统计学意义（P=0.216）,是否青光眼与脉络膜厚度之间无相关性。结论　脉络膜厚度与青光眼无明显相关性,年龄、眼轴长度与脉络膜厚度呈负相关,脉络膜厚度不能作为诊断POAG和病情评估的指标。     

Changes on optical coherence tomography angiography and fluorescein angiography in eyes with neovascular age-related macular degeneration

AIM: To evaluate the changes on optical coherence tomography angiography (OCTA) and fluorescein angiography (FA) and their correlation in neovascular age-related macular degeneration (nAMD) before and after intravitreal aflibercept injections (IAIs). METHODS: In 43 treatment-naïve patients with nAMD, choroidal neovascularization (CNV) in OCTA were morphologically and quantitatively analyzed before and after IAIs to determine whether they are correlated with leakage on FA or not. By combining CNV in OCTA and leakage in FA, lesions were characterized as three types: L+C+ (with both CNV and leakage), L-C+ (with CNV but without leakage), or L+C- lesion (with leakage outside CNV). RESULTS: Before IAI, while 27 eyes had L+C+ lesion only, 16 eyes had both L+C+ and L-C+ lesions simultaneously. Tiny capillaries and anastomosis in CNV were more developed in L+C+ lesion, at 86.0% and 58.1%, respectively, relative to 9.3% and 9.3% in L-C+ lesions (P<0.001). After IAIs in 33 eyes, tiny capillaries and anastomosis were decreased in the lesions with cessation of leakage on FA (P<0.001 and P=0.001, respectively). In quantitative analysis, neovascularization length and numbers of junctions and endpoints were also significantly decreased. CONCLUSION: Leakage on FA is associated with CNV morphology in OCTA and remained so after IAIs. Therefore, by carefully assessing the morphological and quantitative changes of CNV in OCTA before and after treatment, activity of nAMD is expected even though CNV on OCTA is not completely matched with fluorescein leakage.     

傅立叶域光学相干断层扫描仪测量LASIK术后角膜参数的重复性和准确性

目的 研究RTVue傅立叶域光学相干断层扫描仪（FD-OCT）测量准分子激光原位角膜磨镶术（LASIK）后角膜参数的重复性与准确性。方法 前瞻性研究。接受LASIK手术者58例（58眼）,均选择右眼进行研究,术前及术后3个月行主觉验光。术前IOL Master测量角膜屈光力,术后3个月使用RTVue FD-OCT测量角膜中央3 mm直径范围内前表面曲率半径（Ranterior）、后表面曲率半径（Rposterior）、角膜后前表面曲率半径之比（Rposterior/Ranterior）、角膜中央厚度（CCT）、角膜总屈光力（Knet）、模拟角膜屈光力（SimK）、角膜前表面屈光力（Kanterior）、角膜后表面屈光力（Kposterior）,IOL Master获得的角膜屈光力（Km）,临床病史法计算LASIK术后角膜总屈光力（Kchm）。连续测量3次。采用变异系数（CV）、Cronbach′s Alpha系数及组内相关系数（ICC）评估重复性;Bonfferroni校正的多重比较分析SimK、Knet、Km与Kchm之间的差异;Pearson相关分析SimK、Knet、Km与Kchm之间的相关性;Bland-Altman分析SimK与Kchm,Knet与Kchm,Km与Kchm,SimK与Knet,SimK与Km一致性并计算95%一致性界限范围（LoA）。结果Ranterior、Rposterior、Rposterior/Ranterior、Kanterior、Kposterior、SimK、Knet和CCT分别为（8.560±0.292）mm、（6.525±0.159）mm、0.763±0.024、（43.98±1.48）D、（-6.13±0.15）D、（39.47±1.33）D、（37.93±1.42）D和（451.81±33.91）μm,各参数CV均小于1%,各参数Cronbach′s Alpha系数和ICC均大于0.9。SimK比Kchm大（0.434±0.433）D,Knet比Kchm小（1.112±0.471）D,Km比Kchm大（0.334±0.379）D,SimK比Knet大（1.546±0.162）D,差异均有统计学意义（P<0.01）;SimK比Km大（0.100±0.287）D,差异无统计学意义。Pearson相关分析,SimK、Knet、Km、Kchm相互间均具有密切的相关性（r均≥0.944,P<0.01）。Bland-Altman图分析SimK与Kchm,Knet与Kchm,Km与Kchm,SimK与Knet,SimK与Km差值的95%一致性区间分别为-0.41～1.28 D,-2.04～-1.11 D,-0.41～1.08 D,1.23～1.86 D,-0.46～0.66 D。结论 RTVue FD-OCT测量LASIK术后角膜曲率和中央角膜厚度具有良好的重复性;RTVue FD-OCT和IOL Master获得的LASIK术后模拟角膜屈光力比临床病史法获得的理论角膜总屈光力略大0.3～0.4 D;Knet可能是评估LASIK术后角膜屈光力的较准确方法,但用于LASIK术后人工晶状体屈光力的预测,还需进一步的临床研究。     

近视眼黄斑区视网膜色素上皮层厚度及形态与对比敏感度的联系

目的：探讨近视眼视网膜色素上皮层争神经纤维层厚度及其形态与对比敏感度值的联系。方法：21例近视眼病例，39眼做光学相干断层扫描（optical ezherene etomography，OCT），扫描测量并观察黄斑区的视网膜神经纤维层和色素层的厚度和形态；以F．A．C．T对比敏感度测试卡测量各个频率的对比敏感度值；采用Spearman等级相关分析法，分析对比敏感度与近视眼底萎缩弧以及视网膜色素上皮层、视网膜神经纤维层厚度之间的联系；比较不同视网膜色素上皮病变程度的近视眼病例的对比敏感度值。结果：在黄斑区视网膜色素上皮层平均厚度与高频（12、18cpd）对比敏感度值之间存在具有正相关，有显著性意义（r=0．452、0．437，P均〈0．001），而神经纤维层厚度与对比敏感度之间无相关（P均〉0．05）；视网膜色素上皮存在明显病理改变的眼球其对比敏感度功能显著降低（P均〈0．05）。结论：发生眼底病理性改变的近视眼，其对比敏感度降低的视网膜解剖基础是黄斑区视网膜色素上皮层发生病变。     

病理性近视黄斑劈裂光相干断层扫描图像分型及其对临床的指导意义

病理性近视黄斑劈裂光相干断层扫描(OCT)的类组织学分型可以分为单纯外层劈裂、外层和中层劈裂、外层和内层劈裂、多层劈裂4种情况.以彻底清除玻璃体后皮质及后部血管弓内的内界膜为重点的玻璃体视网手术是治疗病理性近视黄斑劈裂的主要选择.其中,单纯外层劈裂合并中心凹脱离者,手术后视功能改善较明显;而多层劈裂者视功能改善有限或不改善.合理剥除后皮质与内界膜起始点,应在未发生内层劈裂处.正确认识和了解病理性近视黄斑劈裂的OCT分型.对于选择玻璃体视网膜手术方式和判断治疗预后有积极意义.     

Technical Note: Accounting for anatomical symmetry in the first-order optical character of left and right eyes

In quantitative analyses of the optical character of eyes (and related systems) it is sometimes necessary to deal with left and right eyes in the same context. In accounting for anatomical symmetry (mirror symmetry in the mid-sagittal plane) one treats a cylinder axis at 20 degrees , say, in a left eye as equivalent to an axis at 160 degrees in a right eye. But this is only one aspect of the linear optical character of an eye. The purpose of this note is to show how to account for anatomical symmetry in the linear optical character of eyes in general. In particular the note shows how to modify the optical properties of left (or right) eyes so that anatomical symmetry is accounted for in quantitative analyses in contexts in which both left and right eyes are involved.     

Comparing glaucomatous optic neuropathy in primary open angle and chronic primary angle closure glaucoma eyes by optical coherence tomography

PURPOSE: To comparatively evaluate the optic nerve head (ONH) using Optical Coherence Tomography (OCT) in normal subjects, primary open angle glaucoma (POAG) and chronic primary angle closure glaucoma (CPACG) patients. METHODS: A total of 138 normal eyes (138 subjects) and 139 glaucomatous eyes (139 patients), were evaluated in this cross-sectional observational study. The ONH was imaged on OCT using the optic disc scan. Disc area, cup area, rim area, vertical integrated rim area (VIRA), rim volume (horizontal integrated rim volume), average cup/disc ratio, horizontal and vertical cup/disc ratios, and cup volume were evaluated. Additionally, cup depth and slope of the temporal ONH were also measured. These ONH parameters were compared between normal subjects and eyes with early POAG and CPACG. Correlation of mean deviation and corrected pattern standard deviation on full threshold 30-2 perimetry, with measured ONH parameters was carried out amongst the two groups. RESULTS: There was a significant difference in disc area (2.38 +/- 0.5, 2.77 +/- 0.4, 2.62 +/- 0.4 mm(2), p < 0.01), cup area (0.88 +/- 0.6, 1.99 +/- 0.7, 1.60 +/- 0.7 mm(2), p < 0.01), rim area (1.48 +/- 0.4, 0.86 +/- 0.4, 0.96 +/- 0.4 mm(2), p < 0.01), VIRA (1.64 +/- 0.3, 1.23 +/- 0.3, 1.22 +/- 0.4 mm(2), p < 0.01), rim volume (0.34 +/- 0.2, 0.1 +/- 0.1, 0.15 +/- 0.1 mm(3), p < 0.01) and cup/disc ratio (0.36 +/- 0.2, 0.69 +/- 0.1, 0.63 +/- 0.2, p < 0.01) in normal vs POAG vs CPACG eyes respectively. A comparison of ONH parameters between early POAG and early CPACG showed a significant difference in the disc area (2.85 +/- 0.3, 2.57 +/- 0.4 mm(2), p = 0.03), cup area (2 +/- 0.5, 1.34 +/- 0.5 mm(2), p < 0.01), rim area (0.96 +/- 0.4, 1.21 +/- 0.5 mm(2), p = 0.009), rim volume (0.12 +/- 0.1, 0.18 +/- 0.1 mm(3), p < 0.01) and cup/disc ratio (0.67 +/- 0.1, 0.53 +/- 0.2, p < 0.01). The parameters with the highest area under the receiver operator characteristic (AROC) curves for differentiating normal and early POAG eyes were rim volume, 0.89, VIRA, 0.84, and rim area, 0.76. The AROC values (normal vs early CPACG eyes) were 0.75 for rim volume, 0.72 for VIRA, and 0.66 for rim area. CONCLUSION: OCT may serve as a useful diagnostic modality in distinguishing a normal optic disc from a glaucomatous one, even in the early stages of glaucoma. Rim volume, VIRA and rim area can be used to differentiate normal from early glaucoma (both early POAG and CPACG), and most efficiently early POAG eyes. CPACG eyes have smaller discs, a smaller cup, smaller cup/disc ratio, and a larger rim area when compared with eyes with POAG.     

Correlation between optic nerve head parameters and retinal nerve fibre layer thickness measured by spectral-domain optical coherence tomography in myopic eyes

Background: To evaluate the correlation between optic nerve head parameters and retinal nerve fiber layer thickness measured by Cirrus HD spectral‐domain optical coherence tomography (Cirrus HD‐OCT; Carl Zeiss Meditec) in healthy myopic eyes. Design: Cross‐sectional study. Participants: One hundred and sixty‐one right eyes from 161 healthy young myopic subjects. Methods: Optic nerve head parameters and retinal nerve fiber layer thickness were measured with the Cirrus HD‐OCT. The distance between optic disc margin and scan circle (disc margin‐to‐scan distance) was measured on the Cirrus HD‐OCT en‐face optic nerve head image with aid of National Institutes of Health ImageJ image‐analysis software (developed by Wayne Rasbands, National Institutes of Health, Bethesda, MD). Main Outcome Measures: The correlations among optic nerve head parameters, retinal nerve fibre layer thickness and the disc margin‐to‐scan distance were evaluated with and without adjustment of the magnification effect. Results: Without correction of the magnification effect, the thicker average retinal nerve fiber layer was correlated with greater rim area and lower degree of myopia (P < 0.001). When the magnification effect was corrected, thicker average retinal nerve fibre layer was associated with greater disc area and greater rim area in univariate and multivariate analyses (P ≤ 0.028); however, degrees of myopia and the disc margin‐to‐scan distance were not significantly associated with average RNFL thickness (P ≥ 0.104). Conclusions: Thicker average retinal nerve fibre layer thickness was associated with greater rim and disc areas. Disc margin‐to‐scan distance was not significantly correlated with average retinal nerve fibre layer thickness in healthy myopic eyes.     

Three-dimensional choroidal vascularity index and choroidal thickness in fellow eyes of acute and chronic primary angle-closure using swept-source optical coherence tomography

AIM: To compare the three-dimensional choroidal vascularity index (CVI) and choroidal thickness between fellow eyes of acute primary angle-closure (F-APAC) and chronic primary angle-closure glaucoma (F-CPACG) and the eyes of normal controls. METHODS: This study included 37 patients with unilateral APAC, 37 with asymmetric CPACG without prior treatment, and 36 healthy participants. Using swept-source optical coherence tomography (SS-OCT), the macular and peripapillary choroidal thickness and three-dimensional CVI were measured and compared globally and sectorally. Pearson’s correlation analysis and multivariate regression models were used to evaluate choroidal thickness or CVI with related factors. RESULTS: The mean subfoveal CVIs were 0.35±0.10, 0.33±0.09, and 0.29±0.04, and the mean subfoveal choroidal thickness were 315.62±52.92, 306.22±59.29, and 262.69±45.55 μm in the F-APAC, F-CPACG, and normal groups, respectively. All macular sectors showed significantly higher CVIs and choroidal thickness in the F-APAC and F-CPACG eyes than in the normal eyes (P<0.05), while there were no significant differences between the F-APAC and F-CPACG eyes. In the peripapillary region, the mean overall CVIs were 0.21±0.08, 0.20±0.08, and 0.19±0.05, and the mean overall choroidal thickness were 180.45±54.18, 174.82±50.67, and 176.18±37.94 μm in the F-APAC, F-CPACG, and normal groups, respectively. There were no significant differences between any of the two groups in all peripapillary sectors. Younger age, shorter axial length, and the F-APAC or F-CPACG diagnosis were significantly associated with higher subfoveal CVI and thicker subfoveal choroidal thickness (P<0.05). CONCLUSION: The fellow eyes of unilateral APAC or asymmetric CPACG have higher macular CVI and choroidal thickness than those of the normal controls. Neither CVI nor choroidal thickness can distinguish between eyes predisposed to APAC or CPACG. A thicker choroid with a higher vascular volume may play a role in the pathogenesis of primary angle-closure glaucoma.     

Repeatability in and interchangeability between the macular and the fast macular thickness map protocols: a study on normal eyes with Stratus optical coherence tomography

Purpose: To collect a normal material and to compare the macular and the fast macular thickness map protocols regarding normal values and repeatability. Methods: Sixty‐seven individuals underwent three repeated scans with the macular thickness protocol; 45 of them also had three scans with the fast thickness protocol in Stratus optical coherence tomography (OCT). The maps were divided into nine ETDRS fields, where thickness values were presented. The repeatability was calculated as intraclass correlation coefficient (ICC), coefficient of variance (CV) and coefficient of repeatability (CR). For comparison between the two protocols, limits of agreement were determined according to Bland–Altman. Results: Normal values for the two protocols were very close. Repeatability was high. ICC for all areas was 0.92–0.98. CV was less than 1% and CR was 6–8 μm for both protocols, with the exception of the fovea in the fast protocol (where CV was 1.44% and CR 12.4 μm). Limits of agreement between the two protocols were less than 10 μm as a rule. Conclusion: Normal values for the protocols are equal and they both have excellent repeatability. The fast macular map is a good alternative with the possible exception of the fovea, where variation is twice that of the macular thickness map.     

Microstructural morphology and visual acuity outcome in eyes with epiretinal membrane before, during, and after membrane peeling in intraoperative optical coherence tomography assisted macular surgery

AIM: To measure the difference of intraoperative central macular thickness (CMT) before, during, and after membrane peeling and investigate the influence of intraoperative macular stretching on postoperative best corrected visual acuity (BCVA) outcome and postoperative CMT development. METHODS: A total of 59 eyes of 59 patients who underwent vitreoretinal surgery for epiretinal membrane was analyzed. Videos with intraoperative optical coherence tomography (OCT) were recorded. Difference of intraoperative CMT before, during, and after peeling was measured. Pre- and postoperatively obtained BCVA and spectral-domain OCT images were analyzed. RESULTS: Mean age of the patients was 70±8.13y (range 46-86y). Mean baseline BCVA was 0.49±0.27 logMAR (range 0.1-1.3). Three and six months postoperatively the mean BCVA was 0.36±0.25 (P=0.01 vs baseline) and 0.38±0.35 (P=0.08 vs baseline) logMAR respectively. Mean stretch of the macula during surgery was 29% from baseline (range 2%-159%). Intraoperative findings of macular stretching did not correlate with visual acuity outcome within 6mo after surgery (r=-0.06, P=0.72). However, extent of macular stretching during surgery significantly correlated with less reduction of CMT at the fovea centralis (r=-0.43, P<0.01) and 1 mm nasal and temporal from the fovea (r=-0.37, P=0.02 and r=-0.50, P<0.01 respectively) 3mo postoperatively. CONCLUSION: The extent of retinal stretching during membrane peeling may predict the development of postoperative central retinal thickness, though there is no correlation with visual acuity development within the first 6mo postoperatively.     

Repeatability, interocular correlation and agreement of optic nerve head vessel density in healthy eyes: a swept-source optical coherence tomographic angiography study

AIM: To assess the repeatability, interocular correlation, and agreement of quantitative swept-source optical coherence tomography angiography (OCTA) optic nerve head (ONH) parameters in healthy subjects. METHODS: Thirty-three healthy subjects were enrolled. The ONH of both eyes were imaged four times by a swept-source-OCTA using a 3 mm ×3 mm scanning protocol. Images of the radial peripapillary capillary were analyzed by a customized Matlab program, and the vessel density, fractal dimension, and vessel diameter index were measured. The repeatability of the four scans was determined by the intraclass correlation coefficient (ICC). The most well-centered optic disc from the four repeated scans was then selected for the interocular correlation and agreement analysis using the Pearson correlation coefficient, ICC and Bland-Altman plots. RESULTS: All swept-source-OCTA ONH parameters exhibited certain repeatability, with ICC>0.760 and coefficient of variation (CoV)≤7.301%. The obvious interocular correlation was observed for papillary vessel density (ICC=0.857), vessel diameter index (ICC=0.857) and fractal dimension (ICC=0.906), while circumpapillary vessel density exhibited moderate interocular correlation (ICC=0.687). Bland-Altman plots revealed an agreement range of -5.26% to 6.21% for circumpapillary vessel density. CONCLUSION: OCTA ONH parameters demonstrate good repeatability in healthy subjects. The interocular correlations of papillary vessel density, fractal dimension and vessel diameter index are high, but the correlation for circumpapillary vessel density is moderate.