Optical coherence tomography (OCT) has revolutionized the clinical practice of ophthalmology. It is a noninvasive imaging technique that provides high-resolution, cross-sectional images of the ...retina, retinal nerve fiber layer and the optic nerve head. This review discusses the present applications of the commercially available spectral-domain OCT (SD-OCT) systems in the diagnosis and management of retinal diseases, with particular emphasis on choroidal imaging. Future directions of OCT technology and their potential clinical uses are discussed.
Analysis of the choroidal thickness in healthy eyes and disease states such as age-related macular degeneration, central serous chorioretinopathy, diabetic retinopathy and inherited retinal dystrophies has been successfully achieved using SD-OCT devices with software improvements. Future OCT innovations such as longer-wavelength OCT systems including the swept-source technology, along with Doppler OCT and en-face imaging, may improve the detection of subtle microstructural changes in chorioretinal diseases by improving imaging of the choroid.
Advances in OCT technology provide for better understanding of pathogenesis, improved monitoring of progression and assistance in quantifying response to treatment modalities in diseases of the posterior segment of the eye. Further improvements in both hardware and software technologies should further advance the clinician's ability to assess and manage chorioretinal diseases.
To describe the characteristics as well as the sensitivity and specificity of detection of choroidal neovascularization (CNV) on optical coherence tomography angiography (OCTA) using spectral-domain ...optical coherence tomography.
Observational, retrospective study.
Seventy-two eyes of 61 subjects (48 eyes of 43 subjects with CNV, 24 eyes of 18 subjects without CNV).
Patients imaged using the prototype AngioVue OCTA system (Optovue, Inc, Fremont, CA) between August 2014 and October 2014 at New England Eye Center were assessed. Patients in whom CNV was identified on OCTA were evaluated to define characteristics of CNV on OCTA: size using greatest linear dimension (small, <1 mm; medium, 1-2 mm; large, >2 mm), appearance (well-circumscribed, poorly circumscribed), and presence of subretinal and intraretinal fluid. Concurrently, an overlapping second cohort of patients who underwent same-day OCTA and fluorescein angiography (FA) for suspected CNV was evaluated to estimate sensitivity and specificity of OCTA in detecting CNV using FA as ground truth.
Choroidal neovascularization appearance, CNV size, and presence of subretinal and intraretinal fluid.
In 48 eyes, CNV was visualized on OCTA. Thirty-one eyes had CNV associated with neovascular age-related macular degeneration. Size of CNV was small in 23% (7/31), medium in 42% (13/31), and large in 35% (11/31). Poorly circumscribed vessels, subretinal fluid, and intraretinal fluid each were seen in 71% (22/31). Seven eyes had CNV associated with central serous chorioretinopathy. Size of CNV was small in 71% (5/7) and large in 29% (2/7). Seventy-one percent (5/7) had well-circumscribed vessels, 86% (6/7) had subretinal fluid, and 14% (1/7) had intraretinal fluid. Thirty eyes with OCTA and same-day FA were evaluated to determine sensitivity and specificity of CNV detection on OCTA. Sensitivity was 50% (4/8) and specificity was 91% (20/22).
Using OCTA allows the clinician to visualize CNV noninvasively and may provide a method for identifying and guiding treatment of CNV. The specificity of CNV detection on OCTA compared with FA seems to be high. Future studies with larger sample sizes are needed to elaborate better on the sensitivity and specificity of CNV detection and to illustrate clinical usefulness.
The body of knowledge of in vivo investigation of the choroid has been markedly enhanced by recent technological advances in optical coherence tomography (OCT). New insights elucidating the ...morphological features of the choriocapillaris and choroidal vasculature, in both physiological and pathological conditions, indicate that the choroid plays a pivotal role in many posterior segment diseases. In this article, a review of the histological characteristics of the choroid, which must be considered for the proper interpretation of in vivo imaging, is followed by a comprehensive discussion of fundamental principles of the current state-of-the-art in OCT, including cross-sectional OCT, en face OCT, and OCT angiography using both spectral domain OCT and swept source OCT technologies. A detailed review of the tomographic features of the choroid in the normal eye is followed by relevant findings in prevalent chorioretinal diseases, focusing on major causes of vision loss such as typical early and advanced age-related macular degeneration, polypoidal choroidal vasculopathy, central serous chorioretinopathy, pachychoroid spectrum disorders, diabetic choroidopathy, and myopia.
Purpose To examine choroidal thickness and area in healthy eyes using spectral-domain optical coherence tomography (SD-OCT). Design Retrospective, observational case series. Methods Thirty-four eyes ...(34 subjects), with no retinal or choroidal disease, underwent high-definition raster scanning using SD-OCT with frame enhancement software. Choroidal thickness was measured from the posterior edge of the retinal pigment epithelium to the choroid/sclera junction at 500-μm intervals up to 2500 μm temporal and nasal to the fovea. The central 1-mm area of the choroid was also measured, along with foveal thickness of the retina. All measurements were performed by 2 independent observers. Statistical analysis was used to correlate inter-observer findings, choroidal thickness and area measurements with age, and choroidal thickness with retinal foveal thickness. Results The 34 subjects had a mean age of 51.1 years. Reliable measurements of choroidal thickness were obtainable in 74% of eyes examined. Choroidal thickness and area measurements had strong inter-observer correlation (r = 0.92, P < .0001 and r = 0.93, P < .0001 respectively). Area had a moderate negative correlation with age (r = −0.62, P < .0001) that was comparable to the correlation between mean subfoveal choroidal thickness and age (r = −0.61, P < .0001). Retinal and choroidal thickness were found to be poorly correlated (r = −0.23, P = .18). Mean choroidal thickness showed a pattern of thinnest choroid nasally, thickening in the subfoveal region, and then thinning again temporally. Mean subfoveal choroidal thickness was found to be 272 μm (SD, ± 81 μm). Conclusions Choroidal thickness can be measured using SD-OCT high-definition raster scans in the majority of eyes. Choroidal thickness across the macula demonstrates a thin choroid nasally, thickest subfoveally, and again thinner temporally, and a trend toward decreasing choroidal thickness with age.
Binarization is a critical technique in optical coherence tomography angiography (OCTA) image analysis, but there is no consistency in the method used in published OCTA studies. This study assessed ...whether differences in OCTA binarization and brightness and contrast adjustments affect quantification measurements.
Prospective cross-sectional validity study.
This was a single-center study examining 21 eyes of 11 healthy individuals. All eyes were imaged using a swept-source OCTA (Zeiss), and quantitative measurements resulting from five binarization thresholding and five brightness/contrast adjustment methods were compared. All measurements were calculated for the superficial plexus and choriocapillaris (CC), as well as unaveraged and averaged en face OCTA images.
There were statistically significant differences between measurements from different binarization thresholding methods (P < 0.0001), as well as measurements from different histogram adjustments (P < 0.0001). The binarization thresholds yielded different measurements when combined with variable brightness/contrast adjustments. The method of analysis also affected the directionality of trends in imaging measurements between unaveraged and averaged CC images.
The method of OCTA image binarization thresholding and histogram adjustment significantly alters quantitative measurements and the directionality of trends. Results obtained from different OCTA binarization methods should be seen as valid only for that given method. This has significant consequences for clinical trials using OCTA measurements as outcome measurements. A consensus is needed across the research community for a consistent method for OCTA image quantification and greater attention paid to fully describing methods in published studies.
To analyze the morphologic features and vasculature of the choroid in healthy eyes using spectral-domain (SD) optical coherence tomography (OCT).
Cross-sectional retrospective review.
Forty-two ...healthy subjects (42 eyes) with no ocular disease who underwent high-definition scanning with Cirrus high-definition OCT (Carl Zeiss Meditec, Inc., Dublin, CA) at the New England Eye Center, Boston, Massachusetts, between November 2009 and September 2010.
The SD OCT images were evaluated for morphologic features of the choroid, including the shape of the choroid-scleral border, location of the thickest point of choroid, and regions of focal choroidal thinning. Total choroidal thickness and large choroidal vessel layer thickness were measured by 2 independent observers experienced in analyzing OCT images using the Cirrus linear measurement tool at the fovea, 750 μm nasal and temporal to the fovea. Custom software was used to calculate the ratio of choroidal stroma to the choroidal vessel lumen.
Qualitative assessment of the choroidal morphologic features, quantitative analysis of choroidal vasculature, and use of novel automated software to determine the ratio of choroidal stromal area to the area of choroidal vessel lumen.
The 42 subjects had a mean age of 51.6 years. All subjects (100%) had a so-called bowl or convex shape to the choroid-sclera junction, and the thickest point of the choroid was under the fovea in 88.0% of the subjects. The mean choroidal thickness was 256.8 ± 75.8 μm, mean thickness of the large choroidal vessel layer was 204.3 ± 65.9 μm, and that of the medium choroidal vessel layer-choriocapillaris layer was 52.9 ± 20.6 μm beneath the fovea. The ratio of large choroidal vessel layer thickness to the total choroidal thickness beneath the fovea was 0.7 ± 0.06. The software-generated ratio of choroidal stromal area to the choroidal vessel lumen area was 0.27 ± 0.08, suggesting that choroidal vessel lumen forms a greater proportion of the choroid than the choroidal stroma in healthy eyes.
This is the first study to describe the morphologic features and vasculature of the choroid in healthy eyes from 1-line raster scans obtained using SD OCT. The method described holds promise and has immediate clinical usefulness in recognizing subtle changes in choroidal morphologic features and the role of choroidal angiopathy in various disease states that, in the future, may inform new treatment methods.
Proprietary or commercial disclosure may be found after the references.
Diabetic retinopathy (DR) is characterized by microaneurysms, capillary nonperfusion, and ischemia within the retina, ultimately leading to neovascularization and/or macular edema. Evidence suggests ...that choroidal angiopathy may coexist with retinal vascular damage. Recent advances in spectral-domain optical coherence tomography (SD-OCT) permit an efficient visualization of the choroid.
To analyze the morphological features and vascular layers of the choroid in patients with DR using SD-OCT.
A cross-sectional retrospective review identified patients with DR and healthy (control) subjects who underwent 1-line raster scanning from February 1, 2010, through June 30, 2012. Patients were classified into the following 3 groups: nonproliferative DR without macular edema (9 eyes), proliferative DR without macular edema (PDR) (10 eyes), and diabetic macular edema (DME) (14 eyes). Two independent raters experienced in analyzing OCT images evaluated the morphological features and vasculature of the choroid.
New England Eye Center.
Thirty-three eyes of 33 patients with DR and 24 eyes of 24 controls.
Diabetic retinopathy.
Choroidal morphological features and vasculature analysis.
The choroidoscleral interface had an irregular contour in 8 of 9 eyes with nonproliferative DR (89%), 9 of 10 eyes with PDR (90%), and 13 of 14 eyes with DME (93%) compared with 0 of 24 controls. The thickest point of the choroid was displaced from under the fovea, and focal choroidal thinning was observed in eyes with DR. Mean subfoveal choroidal thickness and mean subfoveal medium choroidal vessel layer and choriocapillaris layer thickness were significantly reduced in eyes with PDR (P < .05) and DME (P < .05) compared with controls.
Choroidal morphological features are altered in patients with moderate to severe DR. The subfoveal choroidal thickness and the subfoveal medium choroidal vessel layer and choriocapillaris layer thicknesses are significantly reduced in patients with PDR and DME. To our knowledge, this is the first study to analyze the morphological features and vasculature of the choroid in DR using SD-OCT. These findings may be clinically useful in predicting the progression of DR.
Purpose To understand the relationship between choroidal thickness and various disease factors in patients with age-related macular degeneration (AMD) using spectral-domain optical coherence ...tomography. Design Cross-sectional, retrospective analysis. Methods Fifty-seven eyes of 47 patients with wet and dry AMD seen between November 2009 and January 2010 at the New England Eye Center, Boston, Massachusetts, were analyzed. Choroidal thickness was measured by 2 independent observers at 11 sites with high-definition horizontal 1-line raster scans through the foveal center. A retrospective chart review was performed to obtain data concerning duration of disease, number of intravitreal anti–vascular endothelial growth factor injections, visual acuity, lens status, and concomitant retinal pathologic features. The Pearson correlation and Student t test were used for statistical analysis for assessment of choroidal thickness changes in wet and dry AMD. Results The choroid in eyes with wet and dry AMD demonstrated a wide range of thicknesses above and below the normal mean (range, 77.5 to 399.5 μm; standard deviation SD, 90.2). Nearly one third (33.3%) of the eyes with AMD measured less than 1 SD below the mean. Eyes with wet AMD demonstrated a mean subfoveal choroidal thickness of 194.6 μm (SD, 88.4; n = 40) compared with 213.4 μm (SD, 92.2; n = 17) in the dry AMD group. The choroidal thickness in eyes with dry AMD was correlated inversely with age ( r = −0.703; P = .002); however, analysis of the number of intravitreal anti–vascular endothelial growth factor injections, number of years of disease, and visual acuity failed to demonstrate any significant correlations with choroidal thickness. Conclusions This study demonstrated that choroidal thickness can be measured by spectral-domain optical coherence tomography and that variable choroidal thickness exists among patients with the clinical diagnosis of wet and dry AMD. However, it is unclear at this time why in some eyes, choroidal thickness either increases or decreases with the disease. Further studies need to be carried out to understand the significance of choroidal thickness with respect to visual function and disease progression over time.
Optical coherence tomography angiography (OCTA) is a new, non-invasive imaging technique that generates volumetric angiography images in a matter of seconds. This is a nascent technology with a ...potential wide applicability for retinal vascular disease. At present, level 1 evidence of the technology's clinical applications doesn't exist. In this paper, we introduce the technology, review the available English language publications regarding OCTA, and compare it with the current angiographic gold standards, fluorescein angiography (FA) and indocyanine green angiography (ICGA). Finally we summarize its potential application to retinal vascular diseases. OCTA is quick and non-invasive, and provides volumetric data with the clinical capability of specifically localizing and delineating pathology along with the ability to show both structural and blood flow information in tandem. Its current limitations include a relatively small field of view, inability to show leakage, and proclivity for image artifact due to patient movement/blinking. Published studies hint at OCTA's potential efficacy in the evaluation of common ophthalmologic diseases such age related macular degeneration (AMD), diabetic retinopathy, artery and vein occlusions, and glaucoma. OCTA can detect changes in choroidal blood vessel flow and can elucidate the presence of choroidal neovascularization (CNV) in a variety of conditions but especially in AMD. It provides a highly detailed view of the retinal vasculature, which allows for accurate delineation of the foveal avascular zone (FAZ) in diabetic eyes and detection of subtle microvascular abnormalities in diabetic and vascular occlusive eyes. Optic disc perfusion in glaucomatous eyes is notable as well on OCTA. Further studies are needed to more definitively determine OCTA's utility in the clinical setting and to establish if this technology may offer a non-invasive option of visualizing the retinal vasculature in detail.
We demonstrate in vivo choriocapillaris and choroidal microvasculature imaging in normal human subjects using optical coherence tomography (OCT). An ultrahigh speed swept source OCT prototype at 1060 ...nm wavelengths with a 400 kHz A-scan rate is developed for three-dimensional ultrahigh speed imaging of the posterior eye. OCT angiography is used to image three-dimensional vascular structure without the need for exogenous fluorophores by detecting erythrocyte motion contrast between OCT intensity cross-sectional images acquired rapidly and repeatedly from the same location on the retina. En face OCT angiograms of the choriocapillaris and choroidal vasculature are visualized by acquiring cross-sectional OCT angiograms volumetrically via raster scanning and segmenting the three-dimensional angiographic data at multiple depths below the retinal pigment epithelium (RPE). Fine microvasculature of the choriocapillaris, as well as tightly packed networks of feeding arterioles and draining venules, can be visualized at different en face depths. Panoramic ultra-wide field stitched OCT angiograms of the choriocapillaris spanning ∼32 mm on the retina show distinct vascular structures at different fundus locations. Isolated smaller fields at the central fovea and ∼6 mm nasal to the fovea at the depths of the choriocapillaris and Sattler's layer show vasculature structures consistent with established architectural morphology from histological and electron micrograph corrosion casting studies. Choriocapillaris imaging was performed in eight healthy volunteers with OCT angiograms successfully acquired from all subjects. These results demonstrate the feasibility of ultrahigh speed OCT for in vivo dye-free choriocapillaris and choroidal vasculature imaging, in addition to conventional structural imaging.
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