Quantitative shadow compensated optical coherence tomography of choroidal vasculature

Conventionally rendered optical coherence tomography (OCT) images of the posterior segment contain shadows which influence the visualization of deep structures such as the choroid. The purpose of this study was to determine whether OCT shadow compensation (SC) alters the appearance of the choroid and the apparent choroidal vascularity index (CVI), an OCT-derived estimated ratio of luminal to total choroidal volume. All scans were shadow compensated using a previously published algorithm, binarized using a novel validated algorithm and extracted binarized choroid to estimate CVI. On 27 raw swept-source OCT volume-scans of healthy subjects, the effect of SC on CVI was established both qualitatively and quantitatively. In shadow compensated scans, the choroid was visualized with greater brightness than the neurosensory retina and the masking of deep tissues by retinal blood vessels was greatly reduced. Among study subjects, significant mean difference in CVI of -0.13 was observed between raw and shadow compensated scans. Conventionally acquired OCT underestimates both choroidal reflectivity and calculated CVI. Quantitative analysis based on subjective grading demonstrated that SC increased the contrast between stromal and luminal regions and are in agreement with true tissue regions. This study is warranted to determine the effects of SC on CVI in diseased eyes

Amplitude-scan classification using artificial neural networks

Optical coherence tomography (OCT) images semi-transparent tissues noninvasively. Relying on backscatter and interferometry to calculate spatial relationships, OCT shares similarities with other pulse-echo modalities. There is considerable interest in using machine learning techniques for automated image classifcation, particularly among ophthalmologists who rely heavily on diagnostic OCT.Artifcial neural networks (ANN) consist of interconnected nodes and can be employed as classifers after training on large datasets. Conventionally, OCT scans are rendered as 2D or 3D humanreadable images of which the smallest depth-resolved unit is the amplitude-scan refectivity-function profle which is difcult for humans to interpret. We set out to determine whether amplitude-scan refectivity-function profles representing disease signatures could be distinguished and classifed by a feed-forward ANN. Our classifer achieved high accuracies after training on only 24 eyes, with evidence of good generalization on unseen data. The repertoire of our classifer can now be expanded to include rare and unseen diseases and can be extended to other disciplines and industries

Structural Features of Patients with Drusen-like Deposits and Systemic Lupus Erythematosus

Background: The relevance of drusen-like deposits (DLD) in patients with systemic lupus erythematosus (SLE) is to a large extent uncertain. Their genesis is proposed to be correlated to immune-complex and complement depositions in the framework of SLE. The intention of this study was to determine potential morphological differences in the choroid and retina as well as potential microvascular changes comparing two cohorts of SLE patients divergent in the presence or absence of DLD using multimodal imaging. Methods: Both eyes of 16 SLE patients with DLD were compared to an age- and sex-matched control-group consisting of 16 SLE patients without detectable DLD. Both cohorts were treated with hydroxychloroquine (HCQ) and did not differ in the treatment duration or dosage. Using spectral-domain optical coherence tomography (SD-OCT) choroidal volume measures, choroidal vascularity indices (CVI) and retinal layer segmentation was performed and compared. In addition, by the exploitation of optical coherence tomography angiography vascular density, perfusion density of superficial and deep retinal capillary plexuses and the choriocapillaris were analyzed. For the choroidal OCT-scans, a subset of 51 healthy individuals served as a reference-group. Results: CVI measures revealed a significant reduction in eyes with DLD compared to healthy controls (0.56 (0.54–0.59) versus 0.58 (0.57–0.59) (p = 0.018) and 0.56 (0.54–0.58) versus 0.58 (0.57–0.60) (p < 0.001)). The photoreceptor cell layer presented significant thinning in both eyes of subjects with DLD compared to control subjects without DLD (68.8 ± 7.7 µm vs. 77.1 ± 7.3 µm for right eyes, p = 0.008, and 66.5 ± 10.5 µm vs. 76.1 ± 6.3 µm for left eyes, p = 0.011). OCTA scans revealed no significant changes, yet there could be observed numerically lower values in the capillary plexuses of the retina in eyes with DLD than in eyes without DLD. Conclusions: Our results illustrated significant alterations in the choroidal and retinal analyzes, suggesting a correlation between DLD and the progression of inflammatory processes in the course of SLE leading to retinal degeneration. For this reason, DLD could serve as a biomarker for a more active state of disease

Qualitative comparison of choroidal vascularity measurement algorithms

Purpose: To compare the accuracy of manual and automated binarization technique for the analysis of choroidal vasculature. Methods: This retrospective study was performed on a total of 98 eyes of 60 healthy subjects. Fovea-centered swept source optical coherence tomography (SS-OCT) scans were obtained and choroidal area was binarized using manual and automated image binarization technique separately. Choroidal vessel visualization in the binarized scans were subjectively graded (grades 0–100) by comparing them with the original OCT scan images by two masked graders. The subjective variability and repeatability was compared between two binarization method groups. Intergrader and intragrader variability was estimated using paired t-test. The degree of agreement between the grades for each observer and between the observers was evaluated using Bland–Altman plot. Results: The mean accuracy grades of the automatically binarized images were significantly (P < 0.001) higher (93.38% ± 1.70%) than that of manually binarized images (78.06% ± 2.92%). There was a statistically significant variability and poor agreement between the mean interobserver grades in the manual binarization arm. Conclusion: Automated image binarization technique is faster and appears to be more accurate in comparison to the manual method

Pachydrusen in Indian population: A hospital-based study

Purpose: To report the prevalence of pachydrusen in Indian population and their characteristics in relation to subfoveal choroidal thickness (SFCT), choroidal vascularity index (CVI) in comparison to eyes with soft drusen and subretinal drusenoid deposits (SDD) in age-related macular degeneration (AMD). Methods: The study was a retrospective, cross-sectional study involving patients with a diagnosis of dry AMD in at least one eye. The diagnosis of soft drusen, SDD, and pachydrusen was made on the basis of color fundus photograph and optical coherence tomography (OCT). SFCT and CVI was calculated and compared among the different subtypes of drusen. Results: A total of 169 eyes (143 dry and 26 wet AMD) of 85 patients with a mean age of 67.67 ± 9.57 years were included. In eyes with dry AMD, pachydrusen were seen in 12 eyes (8.4%) with a mean (±SD) SFCT of 289.66 ± 91.01 μ. The difference in SFCT was statistically significant (P = 0.001) using analysis of variance (ANOVA) test. The eyes with pachydrusen had significantly thickened choroid compared to the eyes with SDD (30 eyes; 21.0%) or combination of soft drusen and SDD (29 eyes; 20.3%) but not soft drusen (72 eyes; 50.3%). The difference of CVI in different subgroups was significant (P = 0.03). One eye in wet AMD group had concurrent pachydrusen. Comparison of SFCT and CVI in wet AMD and fellow dry AMD eyes were not significant. Conclusion: In Indian eyes with dry AMD, prevalence of pachydrusen (8.4%) is slightly lower compared to western literature (11.7%) and is associated with thicker choroid and higher CVI

Association of Optical Coherence Tomography Angiography of Collaterals in Retinal Vein Occlusion With Major Venous Outflow Through the Deep Vascular Complex

IMPORTANCE Analysis of collateral vessel formation following retinal vein occlusion may advance our understanding of the venous outflow anatomy in the macula. OBJECTIVE To determine the location of collateral vessels with optical coherence tomography (OCT) angiography imaging. DESIGN, SETTING, AND PARTICIPANTS Observational retrospective cohort study. Collateral vessel formation was studied with OCT angiography (OCTA) in patients with retinal vein occlusion (RVO). The study took place at 2 retinal practices (Vitreous Retina Macula Consultants of New York and Stein Eye Institute, University of California, Los Angeles), with patient records retrieved from March 2015 to August 2017. Data analysis was completed in November 2017. EXPOSURES Collaterals identified with fundus photography and/or fluorescein angiography were analyzed with OCTA to determine their course through the superficial vascular plexus (SVP) and the deep vascular complex (DVC). MAIN OUTCOMES AND MEASURES Collateral vessel pathways through the SVP and DVC were analyzed with cross-sectional and en face OCT and OCTA segmentation and color-coded volume renderings prepared from raw OCTA voxel data. RESULTS From 23 eyes (22 branch and 1 hemispheric retinal vein occlusion ) of 23 patients (mean [SD] age, 73 [11] years), 101 collateral vessels were identified and analyzed (mean [SD], 4.4 [2.0]; range, 2-9 collateral per eye). On OCTA, the collaterals appeared as curvilinear dilated flow signals that connected veins across the horizontal raphe or veins on opposite sides of an occluded venous segment within the same retinal hemisphere. Of the 101 collaterals analyzed, all showed greater flow signal in the DVC, and all had some portion of their course identified within the DVC. No collaterals were found exclusively in the SVP. Volume renderings for 3 cases confirmed qualitatively that retinal collateral vessels course through the retina predominantly at the level of the DVC. CONCLUSIONS AND RELEVANCE Based on a limited number of cases, all collateral vessels associated with retinal vein occlusion were found to course through the DVC. The absence of collaterals isolated to the SVP supports a serial arrangement of the SVP and DVC, with venous drainage predominantly coursing through the DVC

Towards true-to-scale 3D reconstruction of the human face using structured light projection and off-the-shelf cameras

In recent years, 3D surface imaging has been adopted in oculofacial surgeries; 3D measurements have facilitated surgical planning and post-operative assessment. Furthermore, life-like 3D visualization has provided a promising alternative as tools of communication and training. However, such surface imaging and visualization technologies remain restricted to the legacy systems. In this paper, we present a 3D surface imaging and reconstruction system made from off-The-shelf components. Our imaging setup consists of custom-made stereo cameras and structured light projection. We demonstrate a true-To-scale 3D reconstruction of the frontal part of the head of a human subject, by capturing its multiple views. We use a non-intrusive auto-calibration method to ensure reconstruction accuracy. The paper also discusses the lighting conditions of such capture procedures, as such parameters may severely affect the performance

Structural Features of Patients with Drusen-like Deposits and Systemic Lupus Erythematosus

Background: The relevance of drusen-like deposits (DLD) in patients with systemic lupus erythematosus (SLE) is to a large extent uncertain. Their genesis is proposed to be correlated to immune-complex and complement depositions in the framework of SLE. The intention of this study was to determine potential morphological differences in the choroid and retina as well as potential microvascular changes comparing two cohorts of SLE patients divergent in the presence or absence of DLD using multimodal imaging. Methods: Both eyes of 16 SLE patients with DLD were compared to an age- and sex-matched control-group consisting of 16 SLE patients without detectable DLD. Both cohorts were treated with hydroxychloroquine (HCQ) and did not differ in the treatment duration or dosage. Using spectral-domain optical coherence tomography (SD-OCT) choroidal volume measures, choroidal vascularity indices (CVI) and retinal layer segmentation was performed and compared. In addition, by the exploitation of optical coherence tomography angiography vascular density, perfusion density of superficial and deep retinal capillary plexuses and the choriocapillaris were analyzed. For the choroidal OCT-scans, a subset of 51 healthy individuals served as a reference-group. Results: CVI measures revealed a significant reduction in eyes with DLD compared to healthy controls (0.56 (0.54&ndash;0.59) versus 0.58 (0.57&ndash;0.59) (p = 0.018) and 0.56 (0.54&ndash;0.58) versus 0.58 (0.57&ndash;0.60) (p &lt; 0.001)). The photoreceptor cell layer presented significant thinning in both eyes of subjects with DLD compared to control subjects without DLD (68.8 &plusmn; 7.7 &micro;m vs. 77.1 &plusmn; 7.3 &micro;m for right eyes, p = 0.008, and 66.5 &plusmn; 10.5 &micro;m vs. 76.1 &plusmn; 6.3 &micro;m for left eyes, p = 0.011). OCTA scans revealed no significant changes, yet there could be observed numerically lower values in the capillary plexuses of the retina in eyes with DLD than in eyes without DLD. Conclusions: Our results illustrated significant alterations in the choroidal and retinal analyzes, suggesting a correlation between DLD and the progression of inflammatory processes in the course of SLE leading to retinal degeneration. For this reason, DLD could serve as a biomarker for a more active state of disease

CHOROIDAL VASCULARITY INDEX AND CHOROIDAL THICKNESS IN EYES WITH RETICULAR PSEUDODRUSEN

To evaluate choroidal vascularity index (CVI), choroidal thickness, choroidal volume, and choroidal intensity in subjects with nonneovascular age-related macular degeneration (NNVAMD) with and without reticular pseudodrusen (RPD). We included 60 eyes of 35 subjects with NNVAMD (including 30 eyes of 18 subjects with RPD) and 30 eyes of 17 age-matched healthy individuals from the ongoing Amish Eye study. The choroid was segmented from dense volume spectral domain optical coherence tomography scans and choroidal thickness (microns), choroidal intensity (log units), and choroidal volume (mm) from the entire macula (6 × 6 mm) were computed. A central horizontal B-scan was binarized and the luminal and stromal portions of the choroid were segmented. Choroidal vascularity index (%) was calculated as the ratio of luminal area to total choroid area. Choroidal parameters were compared between the groups by pairwise comparisons using the Student's t-test. The CVI was significantly lower in healthy eyes compared to those with RPD (53.43 ± 8.51 vs. 54.76 ± 4.83, P < 0.001). The CVI was also significantly lower in NNVAMD eyes without RPD compared to those with RPD (50.09 ± 7.51 vs. 54.76 ± 4.83, P = 0.006). There was no difference in CVI between healthy eyes and NNVAMD eyes without RPD (P = 0.84). Choroidal thickness and choroidal volume were significantly higher in NNVAMD without RPD (P < 0.05); and significantly lower in NNVAMD with RPD (P < 0.05) when compared with normal eyes. Choroidal intensity was significantly higher in NNVAMD with RPD when compared with normal eyes (P = 0.02) and NNVAMD eyes without RPD (P = 0.001). Multiple choroidal parameters reflecting the status of the choroidal vasculature and stroma seem to be altered in eyes with RPD compared with both normal eyes and NNVAMD eyes without RPD. These findings may provide insights into the pathophysiology of RPD