Correlation of Aging and Segmental Choroidal Thickness Measurement using Swept Source Optical Coherence Tomography in Healthy Eyes

Purpose

To assess and compare choroidal thickness changes related to aging, we determined whether changes are due to thinning of the choriocapillaris plus Sattler''s (CS) layer and/or the large vessel layer in healthy eyes using swept-source optical coherence tomography (SS-OCT) at a wavelength of 1,050-nm.

Methods

We studied 115 normal eyes of 115 healthy volunteers, all with refractive errors of less than -6 diopters. All 115 eyes underwent analysis of choroidal thickness at the fovea, the CS layer and the large choroidal vessel layer. In 68 of the 115 eyes, choroidal thickness was determined at five sites (the fovea, and superior, inferior, nasal, and temporal sites) using SS-OCT with an Early Treatment of Diabetic Retinopathy grid scan.

Results

Total choroidal thicknesses at each of the five sites were related to subject age (P<0.0001). The choroid was thinnest at the nasal site, followed by the temporal, inferior, superior and finally the subfoveal site itself. The total choroidal thickness at the nasal site was significantly less than those at the other four sites (p<0.05). The CS layer showed thinning which correlated with age (P<0.0001). The thickness of the choroidal large vessel layer also decreased with age (p = 0.02). Subfoveal choroidal thickness was calculated as follows: 443.89–2.98×age (μm) (P<0.0001).

Conclusion

Subfoveal choroidal thickness decreases by 2.98 μm each year. Total choroidal thickness diminishes with age. The CS and large vessel layers of the choroid at the subfovea showed significant decreases, though only the former correlated strongly with age.     

Enhanced Vitreous Imaging in Healthy Eyes Using Swept Source Optical Coherence Tomography

Purpose

To describe enhanced vitreous imaging for visualization of anatomic features and microstructures within the posterior vitreous and vitreoretinal interface in healthy eyes using swept-source optical coherence tomography (SS-OCT). The study hypothesis was that long-wavelength, high-speed, volumetric SS-OCT with software registration motion correction and vitreous window display or high-dynamic-range (HDR) display improves detection sensitivity of posterior vitreous and vitreoretinal features compared to standard OCT logarithmic scale display.

Design

Observational prospective cross-sectional study.

Methods

Multiple wide-field three-dimensional SS-OCT scans (500×500A-scans over 12×12 mm²) were obtained using a prototype instrument in 22 eyes of 22 healthy volunteers. A registration motion-correction algorithm was applied to compensate motion and generate a single volumetric dataset. Each volumetric dataset was displayed in three forms: (1) standard logarithmic scale display, enhanced vitreous imaging using (2) vitreous window display and (3) HDR display. Each dataset was reviewed independently by three readers to identify features of the posterior vitreous and vitreoretinal interface. Detection sensitivities for these features were measured for each display method.

Results

Features observed included the bursa premacularis (BPM), area of Martegiani, Cloquet''s/BPM septum, Bergmeister papilla, posterior cortical vitreous (hyaloid) detachment, papillomacular hyaloid detachment, hyaloid attachment to retinal vessel(s), and granular opacities within vitreous cortex, Cloquet''s canal, and BPM. The detection sensitivity for these features was 75.0% (95%CI: 67.8%–81.1%) using standard logarithmic scale display, 80.6% (95%CI: 73.8%–86.0%) using HDR display, and 91.9% (95%CI: 86.6%–95.2%) using vitreous window display.

Conclusions

SS-OCT provides non-invasive, volumetric and measurable in vivo visualization of the anatomic microstructural features of the posterior vitreous and vitreoretinal interface. The vitreous window display provides the highest sensitivity for posterior vitreous and vitreoretinal interface analysis when compared to HDR and standard OCT logarithmic scale display. Enhanced vitreous imaging with SS-OCT may help assess the natural history and treatment response in vitreoretinal interface diseases.     

Measurement of Myopia and Normal Human Choroidal Thickness Using Spectral Domain Optical Coherence Tomography

Myopia is a common ophthalmic deficiency. The structure and function of choroid layer is assumed to be associated with myopia. In this study, a laboratory developed spectral domain optical coherence tomography scanning system is used to image human eyes. The axial resolution of the system is about 7 μm, and the acquisition rate is 100 kHz. Firstly, a cross-sectional image was acquired by averaging 100 images from imaging posterior segment of each eye. The choroid thickness was measured by 11 discrete points. The average thickness of normal human eyes was (0.296 ± 0.126) mm, whereas the average choroid thickness of myopic eyes was (0.220 ± 0.095) mm. Afterwards, the T test is used to calculate the data statistically. The analysis of the final result is based on the average thickness measured and the thickness of each measuring point. There was a significant difference in choroid thickness between myopia and normal eyes (P value < 0.01), which indicates that the choroid thickness of myopia was significantly thinner than that of normal eyes. Besides, there are findings that the choroidal thickness in nasal side is thinner than that in the fovea and temporal side in each eye. The choroidal thickness on temporal side in myopia eye has the most significant difference comparing with that in normal eye. The comprehensive evaluation of myopia and normal choroidal thickness using spectral domain optical coherence tomography may provide an important reference for the development of medical methods for diagnosis and treatment of myopia.     

A Simplified Method to Measure Choroidal Thickness Using Adaptive Compensation in Enhanced Depth Imaging Optical Coherence Tomography

Purpose

To evaluate a simplified method to measure choroidal thickness (CT) using commercially available enhanced depth imaging (EDI) spectral domain optical coherence tomography (SD-OCT).

Methods

We measured CT in 31 subjects without ocular diseases using Spectralis EDI SD-OCT. The choroid-scleral interface of the acquired images was first enhanced using a post-processing compensation algorithm. The enhanced images were then analysed using Photoshop. Two graders independently graded the images to assess inter-grader reliability. One grader re-graded the images after 2 weeks to determine intra-grader reliability. Statistical analysis was performed using intra-class correlation coefficient (ICC) and Bland-Altman plot analyses.

Results

Using adaptive compensation both the intra-grader reliability (ICC: 0.95 to 0.97) and inter-grader reliability (ICC: 0.93 to 0.97) were perfect for all five locations of CT. However, with the conventional technique of manual CT measurements using built-in callipers provided with the Heidelberg explorer software, the intra- (ICC: 0.87 to 0.94) and inter-grader reliability (ICC: 0.90 to 0.93) for all the measured locations is lower. Using adaptive compensation, the mean differences (95% limits of agreement) for intra- and inter-grader sub-foveal CT measurements were −1.3 (−3.33 to 30.8) µm and −1.2 (−36.6 to 34.2) µm, respectively.

Conclusions

The measurement of CT obtained from EDI SD-OCT using our simplified method was highly reliable and efficient. Our method is an easy and practical approach to improve the quality of choroidal images and the precision of CT measurement.     

Clinical Factors Associated with Lamina Cribrosa Thickness in Patients with Glaucoma,as Measured with Swept Source Optical Coherence Tomography

PurposeTo investigate the influence of various risk factors on thinning of the lamina cribrosa (LC), as measured with swept-source optical coherence tomography (SS-OCT; Topcon).MethodsThis retrospective study comprised 150 eyes of 150 patients: 22 normal subjects, 28 preperimetric glaucoma (PPG) patients, and 100 open-angle glaucoma patients. Average LC thickness was determined in a 3 x 3 mm cube scan of the optic disc, over which a 4 x 4 grid of 16 points was superimposed (interpoint distance: 175 μm), centered on the circular Bruch’s membrane opening. The borders of the LC were defined as the visible limits of the LC pores. The correlation of LC thickness with Humphrey field analyzer-measured mean deviation (MD; SITA standard 24–2), circumpapillary retinal nerve fiber layer thickness (cpRNFLT), the vertical cup-to-disc (C/D) ratio, and tissue mean blur rate (MBR) was determined with Spearman''s rank correlation coefficient. The relationship of LC thickness with age, axial length, intraocular pressure (IOP), MD, the vertical C/D ratio, central corneal thickness (CCT), and tissue MBR was determined with multiple regression analysis. Average LC thickness and the correlation between LC thickness and MD were compared in patients with the glaucomatous enlargement (GE) optic disc type and those with non-GE disc types, as classified with Nicolela’s method.ResultsWe found that average LC thickness in the 16 grid points was significantly associated with overall LC thickness (r = 0.77, P < 0.001). The measurement time for this area was 12.4 ± 2.4 minutes. Average LC thickness in this area had a correlation coefficient of 0.57 with cpRNFLT (P < 0.001) and 0.46 (P < 0.001) with MD. Average LC thickness differed significantly between the groups (normal: 268 ± 23 μm, PPG: 248 ± 13 μm, OAG: 233 ± 20 μm). Multiple regression analysis showed that MD (β = 0.29, P = 0.013), vertical C/D ratio (β = -0.25, P = 0.020) and tissue MBR (β = 0.20, P = 0.034) were independent variables significantly affecting LC thickness, but age, axial length, IOP, and CCT were not. LC thickness was significantly lower in the GE patients (233.9 ± 17.3 μm) than the non-GE patients (243.6 ± 19.5 μm, P = 0.040). The correlation coefficient between MD and LC thickness was 0.58 (P < 0.001) in the GE patients and 0.39 (P = 0.013) in the non-GE patients.ConclusionCupping formation and tissue blood flow were independently correlated to LC thinning. Glaucoma patients with the GE disc type, who predominantly have large cupping, had lower LC thickness even with similar glaucoma severity.     

Diagnostic Ability of Macular Ganglion Cell Inner Plexiform Layer Measurements in Glaucoma Using Swept Source and Spectral Domain Optical Coherence Tomography

PurposeTo evaluate the diagnostic ability of macular ganglion cell and inner plexiform layer measurements in glaucoma, obtained using swept source (SS) and spectral domain (SD) optical coherence tomography (OCT) and to compare to circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurements.MethodsThe study included 106 glaucomatous eyes of 80 subjects and 41 eyes of 22 healthy subjects from the Diagnostic Innovations in Glaucoma Study. Macular ganglion cell and inner plexiform layer (mGCIPL), macular ganglion cell complex (mGCC) and cpRNFL thickness were assessed using SS-OCT and SD-OCT, and area under the receiver operating characteristic curves (AUCs) were calculated to determine ability to differentiate glaucomatous and healthy eyes and between early glaucomatous and healthy eyes.ResultsMean (± standard deviation) mGCIPL and mGCC thickness were thinner in both healthy and glaucomatous eyes using SS-OCT compared to using SD-OCT. Fixed and proportional biases were detected between SS-OCT and SD-OCT measures. Diagnostic accuracy (AUCs) for differentiating between healthy and glaucomatous eyes for average and sectoral mGCIPL was similar in SS-OCT (0.65 to 0.81) and SD-OCT (0.63 to 0.83). AUCs for average cpRNFL acquired using SS-OCT and SD-OCT tended to be higher (0.83 and 0.85, respectively) than for average mGCC (0.82 and 0.78, respectively), and mGCIPL (0.73 and 0.75, respectively) but these differences did not consistently reach statistical significance. Minimum SD-OCT mGCIPL and mGCC thickness (unavailable in SS-OCT) had the highest AUC (0.86) among macular measurements.ConclusionAssessment of mGCIPL thickness using SS-OCT or SD-OCT is useful for detecting glaucomatous damage, but measurements are not interchangeable for patient management decisions. Diagnostic accuracies of mGCIPL and mGCC from both SS-OCT and SD-OCT were similar to that of cpRNFL for glaucoma detection.     

Subretinal Fluid in Eyes with Active Ocular Toxoplasmosis Observed Using Spectral Domain Optical Coherence Tomography

PurposeTo describe the clinical finding of subretinal fluid (SRF) in the posterior pole by spectral domain optical coherence tomography (SD-OCT) in eyes with active ocular toxoplasmosis (OT).DesignRetrospective case series.ParticipantsThirty-eight eyes from 39 patients with active OT.MethodsEyes with active OT which underwent SD-OCT were reviewed. SRFs in the posterior pole were further analyzed.ResultsSRF presented in 45.5% (or 15/33) of eyes with typical active OT and in 51.3% (or 20/39) of eyes with active OT. The mean maximum height and total volume of SRF were 161.0 (range: 23–478) µm and 0.47 (range: 0.005–4.12) mm3, respectively. For 12 eyes with SRF related to active retinal necrosis, SRF was observed with complete absorption after conventional anti-toxoplasmosis treatment. The mean duration for observation of SRF clearance was 33.8 (range: 7–84) days. The mean rate of SRF clearance was 0.0128 (range: 0.0002–0.0665) mm3/day.ConclusionsSRF (i.e., serous retinal detachment) is a common feature in patients with active OT when SD-OCT is performed. The majority of SRF was associated with retinal necrosis and reacted well to conventional therapy, regardless of total fluid volume. However, SRF accompanying with CME or CNV responded less favorably or remained refractory to conventional or combined intravitreal treatment, even when the SRF was small in size.     

基于光学相干层析成像技术的小鼠表皮厚度的无损测量及分析

光学相干层析成像技术(optical coherence tomography,OCT)在研究活体皮肤的表皮和真皮上层方面是一种很有潜力的手段.本文以小白鼠为研究对象,脱毛后,采用OCT系统对同一部位的小鼠皮肤在制作切片过程中(活体、离体、固定24 h后)进行成像跟踪,分别获得OCT强度图中第一强度峰到第一个波谷,以及第一、二强度峰之间的距离,比较两种结果和组织学的对应情况,并分析其原因,同时关注切片过程中各种物理、化学因素对皮肤各层厚度的影响,研究了OCT图像的各个反射峰与实际皮肤的结构之间联系.     

Analysis of Fundus Shape in Highly Myopic Eyes by Using Curvature Maps Constructed from Optical Coherence Tomography

Purpose

To evaluate fundus shape in highly myopic eyes using color maps created through optical coherence tomography (OCT) image analysis.

Methods

We retrospectively evaluated 182 highly myopic eyes from 113 patients. After obtaining 12 lines of 9-mm radial OCT scans with the fovea at the center, the Bruch’s membrane line was plotted and its curvature was measured at 1-µm intervals in each image, which was reflected as a color topography map. For the quantitative analysis of the eye shape, mean absolute curvature and variance of curvature were calculated.

Results

The color maps allowed staphyloma visualization as a ring of green color at the edge and as that of orange-red color at the bottom. Analyses of mean and variance of curvature revealed that eyes with myopic choroidal neovascularization tended to have relatively flat posterior poles with smooth surfaces, while eyes with chorioretinal atrophy exhibited a steep, curved shape with an undulated surface (P<0.001). Furthermore, eyes with staphylomas and those without clearly differed in terms of mean curvature and the variance of curvature: 98.4% of eyes with staphylomas had mean curvature ≥7.8×10⁻⁵ [1/µm] and variance of curvature ≥0.26×10⁻⁸ [1/µm].

Conclusions

We established a novel method to analyze posterior pole shape by using OCT images to construct curvature maps. Our quantitative analysis revealed that fundus shape is associated with myopic complications. These values were also effective in distinguishing eyes with staphylomas from those without. This tool for the quantitative evaluation of eye shape should facilitate future research of myopic complications.     

Profile and Determinants of Retinal Optical Intensity in Normal Eyes with Spectral Domain Optical Coherence Tomography

Purpose

To investigate the profile and determinants of retinal optical intensity in normal subjects using 3D spectral domain optical coherence tomography (SD OCT).

Methods

A total of 231 eyes from 231 healthy subjects ranging in age from 18 to 80 years were included and underwent a 3D OCT scan. Forty-four eyes were randomly chosen to be scanned by two operators for reproducibility analysis. Distribution of optical intensity of each layer and regions specified by the Early Treatment of Diabetic Retinopathy Study (ETDRS) were investigated by analyzing the OCT raw data with our automatic graph-based algorithm. Univariate and multivariate analyses were performed between retinal optical intensity and sex, age, height, weight, spherical equivalent (SE), axial length, image quality, disc area and rim/disc area ratio (R/D area ratio).

Results

For optical intensity measurements, the intraclass correlation coefficient of each layer ranged from 0.815 to 0.941, indicating good reproducibility. Optical intensity was lowest in the central area of retinal nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer and photoreceptor layer, except for the retinal pigment epithelium (RPE). Optical intensity was positively correlated with image quality in all retinal layers (0.553<β<0.851, p<0.01), and negatively correlated with age in most retinal layers (-0.362<β<-0.179, p<0.01), except for the RPE (β = 0.456, p<0.01), outer nuclear layer and photoreceptor layer (p>0.05). There was no relationship between retinal optical intensity and sex, height, weight, SE, axial length, disc area and R/D area ratio.

Conclusions

There was a specific pattern of distribution of retinal optical intensity in different regions. The optical intensity was affected by image quality and age. Image quality can be used as a reference for normalization. The effect of age needs to be taken into consideration when using OCT for diagnosis.     

Noninvasive,In Vivo Assessment of Mouse Retinal Structure Using Optical Coherence Tomography

Background

Optical coherence tomography (OCT) is a novel method of retinal in vivo imaging. In this study, we assessed the potential of OCT to yield histology-analogue sections in mouse models of retinal degeneration.

Methodology/Principal Findings

We achieved to adapt a commercial 3^rd generation OCT system to obtain and quantify high-resolution morphological sections of the mouse retina which so far required in vitro histology. OCT and histology were compared in models with developmental defects, light damage, and inherited retinal degenerations. In conditional knockout mice deficient in retinal retinoblastoma protein Rb, the gradient of Cre expression from center to periphery, leading to a gradual reduction of retinal thickness, was clearly visible and well topographically quantifiable. In Nrl knockout mice, the layer involvement in the formation of rosette-like structures was similarly clear as in histology. OCT examination of focal light damage, well demarcated by the autofluorescence pattern, revealed a practically complete loss of photoreceptors with preservation of inner retinal layers, but also more subtle changes like edema formation. In Crb1 knockout mice (a model for Leber''s congenital amaurosis), retinal vessels slipping through the outer nuclear layer towards the retinal pigment epithelium (RPE) due to the lack of adhesion in the subapical region of the photoreceptor inner segments could be well identified.

Conclusions/Significance

We found that with the OCT we were able to detect and analyze a wide range of mouse retinal pathology, and the results compared well to histological sections. In addition, the technique allows to follow individual animals over time, thereby reducing the numbers of study animals needed, and to assess dynamic processes like edema formation. The results clearly indicate that OCT has the potential to revolutionize the future design of respective short- and long-term studies, as well as the preclinical assessment of therapeutic strategies.     

A Pilot Study of Morphometric Analysis of Choroidal Vasculature In Vivo,Using En Face Optical Coherence Tomography

Purpose

To study the ability of volumetric spectral domain optical coherence tomography (SD-OCT) to perform quantitative measurement of the choroidal vasculature in vivo.

Methods

Choroidal vascular density and vessel size were quantified using en face choroidal scans from various depths below the retinal pigment epithelium (RPE) in 58 eyes of 58 patients with either epiretinal membranes (ERM), early age-related macular degeneration (AMD), or reticular pseudo-drusen (RPD). For each patient, we used the macular volume scan (6×6 mm cube) for vessel quantification, while high-definition (HD) cross-section raster scans were used to qualitatively assess vascularity of the choroidal sub-layers, and measure choroidal thickness.

Results

Of the 58 patients, more were female (66% versus 34% male), of whom 14 (24%) had ERM, 11 (19%) early AMD, and 33 (57%) RPD. Compared to intact choriocapillaris in all ERM (100%), none of the RPD and only 5/11 (45%) early AMD eyes had visible choriocapillaris on either cross section or C-scans (p-value<0.001). When comparing select regions from the most superficial C-scans, early AMD group had lowest vascular density and RPD had highest (p-value 0.04). Qualitative evaluation of C-scans from all three groups revealed a more granular appearance of the choriocapillaris in ERM versus increased stroma and larger vessels in the RPD eyes.

Conclusions

SD-OCT can be used to qualitatively and quantitatively assess choroidal vascularity in vivo. Our findings correlate to previously reported histopathologic studies. Lack of choriocapillaris on HD cross-sections or C-scans in all RPD and about half of early AMD eyes suggests earlier choroidal involvement in AMD and specifically, RPD.     

Vertical and Horizontal Corneal Epithelial Thickness Profile Using Ultra-High Resolution and Long Scan Depth Optical Coherence Tomography

Purpose

To determine the vertical and horizontal thickness profiles of the corneal epithelium in vivo using ultra-long scan depth and ultra-high resolution spectral domain optical coherence tomography (SD-OCT).

Methods

A SD-OCT was developed with an axial resolution of ∼3.3 µm in tissue and an extended scan depth. Forty-two eyes of 21 subjects were imaged twice. The entire horizontal and vertical corneal epithelial thickness profiles were evaluated. The coefficient of repeatability (CoR) and intraclass correlation (ICC) of the tests and interobserver variability were analyzed.

Results

The full width of the horizontal epithelium was detected, whereas part of the superior epithelium was not shown for the covered super eyelid. The mean central epithelial corneal thickness was 52.0±3.2 µm for the first measurement and 52.3±3.4 µm for the second measurement (P>.05). In the central zone (0–3.0 mm), the paracentral zones (3.0–6.0 mm) and the peripheral zones (6.0–10.0 mm), the mean epithelial thickness ranged from 51 to 53 µm, 52 to 57 µm, and 58 to 72 µm, respectively. There was no difference between the two tests at both meridians and in the right and left eyes (P>.05). The ICCs of the two tests ranged from 0.70 to 0.97 and the CoRs ranged from 2.5 µm to 7.8 µm from the center to the periphery, corresponding to 5.6% to 10.6% (CoR%). The ICCs of the two observers ranged from 0.72 to 0.93 and the CoRs ranged from 4.5 µm to 10.4 µm from the center to the periphery, corresponding to 8.7% to 15.2% (CoR%).

Conclusions

This study demonstrated good repeatability of ultra-high resolution and long scan depth SD-OCT to evaluate the entire thickness profiles of the corneal epithelium. The epithelial thickness increases from the center toward the limbus.     

Feasibility of the Assessment of Cholesterol Crystals in Human Macrophages Using Micro Optical Coherence Tomography

The presence of cholesterol crystals is a hallmark of atherosclerosis, but until recently, such crystals have been considered to be passive components of necrotic plaque cores. Recent studies have demonstrated that phagocytosis of cholesterol crystals by macrophages may actively precipitate plaque progression via an inflammatory pathway, emphasizing the need for methods to study the interaction between macrophages and crystalline cholesterol. In this study, we demonstrate the feasibility of detecting cholesterol in macrophages in situ using Micro-Optical Coherence Tomography (µOCT), an imaging modality we have recently developed with 1-µm resolution. Macrophages containing cholesterol crystals frequently demonstrated highly scattering constituents in their cytoplasm on µOCT imaging, and µOCT was able to evaluate cholesterol crystals in cultured macrophage cells. Our results suggest that µOCT may be useful for the detection and characterization of inflammatory activity associated with cholesterol crystals in the coronary artery.     

Objective Analyses of Tessellated Fundi and Significant Correlation between Degree of Tessellation and Choroidal Thickness in Healthy Eyes

A tessellated fundus is a common characteristic of myopic eyes and is an important clinical marker for the development of retinochoroidal changes. However, the exact cause and significance of tessellated fundi have not been definitively determined. We determined the degree of tessellation in fundi objectively in normal, non-pathological myopic eyes, and correlated the degree of tessellation and the choroidal thickness (CT) and axial length (AL). This was a prospective observational cross sectional study. The eyes were classified subjectively into three groups based on the degree of tessellation observed ophthalmoscopically. Digital color fundus photographs were assessed for the degree of tessellation by ImageJ, an image processing program. Three tessellated fundus indices (TFIs) were calculated and were compared to the three subjectively-determined groups. The subfoveal and nasal CTs were measured in the optical coherence tomographic images. The correlations between the TFIs and the CT were calculated. Additionally, the correlation between the TFIs and the AL was calculated. One hundred right eyes of 100 healthy volunteers (mean age 25.8±3.9 years) were studied. Ophthalmoscopically, 57 eyes were placed in the non-tessellated group, 27 eyes into the weakly tessellated group, and 16 eyes into the strongly tessellated group. There was a significant correlation between the subjective classifications and the TFI values (P<0.05, Kruskal-Wallis test). All of the TFIs were significantly associated with the subfoveal and nasal CT (R = −0.20 to −0.24, P<0.05). The TFIs were not significantly correlated with the ALs. In conclusion, the significant correlation between the subjective and objective classifications of the degree of tessellation indicates that TFIs can be used to classify the degree of tessellation. The results indicate that the differences in the CT account for the degree of tessellation.     

Central and Midperipheral Corneal Thickness Measured with Scheimpflug Imaging and Optical Coherence Tomography

Purpose

To compare corneal thickness measurements using Pentacam (Oculus, Germany), Sirius (CSO, Italy), Galilei (Ziemer, Switzerland), and RTVue-100 OCT (Optovue Inc., USA).

Methods

Sixty-six eyes of 66 healthy volunteers were enrolled. Three consecutive measurements were performed with each device. The mean value of the three measurements was used for subsequent analysis. Central corneal thickness (CCT), thinnest corneal thickness (TCT), and midperipheral corneal thickness (MPCT; measured at superior, inferior, nasal, and temporal locations with a distance of 1 mm (CT_2mm) or 2.5 mm (CT_5mm) from the corneal apex) were analyzed. Differences and agreement between measurements were assessed using the repeated-measures analysis of variance (ANOVA) and Bland-Altman analyses, respectively.

Results

Statistically significant differences (p<0.001) among the four devices were revealed in CCT, TCT and CT_2mmmeasurements. The CCT, TCT, and CT_2mm values were ranked from the thickest to the thinnest as follows: Galilei>Sirius>Pentacam>RTVue OCT. For these measurements, agreement between measurements by Sirius and Pentacam was good, whereas Galilei overestimated and RTVue underestimated corneal thickness compared to Sirius and Pentacam. As regards CT_5mm measurements, Pentacam provided the largest values, whereas RTVue OCT yielded the smallest values. Agreement of the CT_5mm measurements was good between the Pentacam, Sirius, moderate between Galilei and the other two Scheimpflug systems, and poor between the RTVue OCT and the remaining devices.

Conclusions

The Pentacam and Sirius can be used interchangeably for CCT measurements, while the Galilei and RTVue systematically over- and underestimate CCT, respectively. The three Scheimpflug cameras, but not the RTVue, may be used interchangeably for MPCT measurements.     

Morphologic Characteristics of Choroid in the Major Choroidal Thickening Diseases,Studied by Optical Coherence Tomography

We investigated morphologic features of choroid in the choroidal thickening diseases, including central serous chorioretinopathy (CSC), polypoidal choroidal vasculopathy (PCV), and Vogt-Koyanagi-Harada disease (VKH), by a novel tomographic classification system of the choroid. This cross-sectional study involved 30 patients with active CSC, 30 patients with active PCV, and 27 patients with active VKH, and 30 normal controls. Utilizing enhanced depth imaging optical coherence tomography, we classified the morphology of the choroid into five categories: 1) Standard (S), 2) Dilated outer layer and Attenuated inner layer (DA), 3) Darkened (D), 4) Marbled (M), and 5) Pauci-Vascular (PV) types. Additional tomographic characteristics of the choroid such as choroidal vascular dilation, convolution, scleral invisibility, and choroidal hyper- or hypo-thickening were identified as well. The distribution of five choroidal tomographic morphology and additional tomographic characteristics in each group were analyzed. The DA type was observed in the CSC group more frequently than in the normal control group (53.3% vs 3.3%, P < 0.001). Additional tomographic characteristics, such as choroidal vascular dilation (76.7%), and choroidal hyper-thickening (36.7%), were more prevalent in the CSC group than in the control group. The PCV group showed higher prevalence of DA type (33.3% vs. 3.3%, P = 0.006) than the control group. The VKH group showed a significantly higher frequency of the D type (63.0%), convolution (40.7%), and scleral invisibility (70.4%) than controls (0% for all three findings). In conclusion, CSC and PCV shared common morphologic characteristics of choroid, including dilated outer vascular layer and focally attenuated innermost layer. Dense hypo-reflectivity and convolution of choroid were the specific tomographic markers for acute VKH. A new tomographic classification system of choroid may provide discrimination ability and insight into major pachychoroidopathies.     

基于光学相干层析成像技术的皮肤组织非消融性光热损伤过程

使用OCT技术观察活体小鼠皮肤组织在非消融性激光作用后光热损伤及其修复过程,得出皮肤组织在此过程中形态卜的变化规律.利用OCT散射模型得出皮肤在激光作用前后光学参数中衰减系数的变化,根据所获得的光学参数的变化量来判断热损伤程度,并分析引起散射参数变化的原因,作为临床上无损的判断光热作用下皮肤内部损伤情况的依据.结果表明OCT是一种很有潜力的活体监测光热损伤及其修复过程的工具.     

Repeatability of Foveal Measurements Using Spectralis Optical Coherence Tomography Segmentation Software

Purpose

To investigate repeatability and reproducibility of thickness of eight individual retinal layers at axial and lateral foveal locations, as well as foveal width, measured from Spectralis spectral domain optical coherence tomography (SD-OCT) scans using newly available retinal layer segmentation software.

Methods

High-resolution SD-OCT scans were acquired for 40 eyes of 40 young healthy volunteers. Two scans were obtained in a single visit for each participant. Using new Spectralis segmentation software, two investigators independently obtained thickness of each of eight individual retinal layers at 0°, 2° and 5° eccentricities nasal and temporal to foveal centre, as well as foveal width measurements. Bland-Altman Coefficient of Repeatability (CoR) was calculated for inter-investigator and inter-scan agreement of all retinal measurements. Spearman''s ρ indicated correlation of manually located central retinal thickness (RT₀) with automated minimum foveal thickness (MFT) measurements. In addition, we investigated nasal-temporal symmetry of individual retinal layer thickness within the foveal pit.

Results

Inter-scan CoR values ranged from 3.1μm for axial retinal nerve fibre layer thickness to 15.0μm for the ganglion cell layer at 5° eccentricity. Mean foveal width was 2550μm ± 322μm with a CoR of 13μm for inter-investigator and 40μm for inter-scan agreement. Correlation of RT₀ and MFT was very good (ρ = 0.97, P < 0.0005). There were no significant differences in thickness of any individual retinal layers at 2° nasal compared to temporal to fovea (P > 0.05); however this symmetry could not be found at 5° eccentricity.

Conclusions

We demonstrate excellent repeatability and reproducibility of each of eight individual retinal layer thickness measurements within the fovea as well as foveal width using Spectralis SD-OCT segmentation software in a young, healthy cohort. Thickness of all individual retinal layers were symmetrical at 2°, but not at 5° eccentricity away from the fovea.