Laser-based detection and depth estimation of dry and water-filled potholes: A geometric approach

In secondary Indian roads, one often encounters potholes which can be either dry or water-filled. Accordingly, to ensure safe driving, it is imperative to detect potholes and estimate their depths in either condition. In this paper, we develop a physics-based geometric framework, where such detection and depth-estimation can be accomplished using suitable laser. Specifically, we relate dry pothole depth to measured optical deviation using simple ray optics. Further, we use Snell's law of refraction to obtain a quartic equation, and its appropriate real root to relate water-filled pothole depth to the corresponding optical deviation. Here we take into account diminishing resolu- tion with increasing distance from the camera. We conclude by experimentally validating our method

New Insights on Choroidal Vascularity: A Comprehensive Topographic Approach

n/

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

Choroidal structural changes correlate with neovascular activity in neovascular age related macular degeneration

PURPOSE. To correlate changes in choroidal thickness and vascularity index with disease activity in patients with neovascular age-related macular degeneration (nAMD). METHODS. Eyes diagnosed with AMD that had two sequential visits within 12 months and that had no choroidal neovascularization (CNV) or had inactive CNV at the first visit were included. Those that had active CNV at follow-up were enrolled as cases. Eyes that did not developed a CNV or that were still inactive at the second visit were enrolled as controls. Disease activity was based on optical coherence tomography (OCT) and fluorescein angiography findings. Subfoveal choroidal thickness (SCT), mean choroidal thickness (MCT), and choroidal vascularity index (CVI) were assessed on enhanced depth imaging OCT and compared between the baseline and follow-up visit. Subgroup analysis accounting for lesion type and previous treatment, if any, were performed. RESULTS. Sixty-five eyes from 60 patients (35 females) and 50 age-and sex-matched controls were included. At the active visit, cases had an increase from 164 +/- 67 mu m to 175 +/- 70 mu m in mean +/- SD SCT and from 144 +/- 45 mu m to 152 +/- 45 mu m in MCT (both P < 0.0001). The mean CVI also increased at from 54.5% +/- 3.3% to 55.4% +/- 3.8% (P = 0.04). Controls did not show significant changes in choroidal measurements between the two visits. Mean SCT, MCT, and CVI values were similar for previously treated and treatment-naive eyes. CONCLUSIONS. Choroidal thickness and CVI significantly increased with active disease in nAMD eyes. Changes in choroidal thickness may predict CNV development or recurrence before they are otherwise evident clinically

Choroidal Structural Changes Correlate With Neovascular Activity in Neovascular Age Related Macular Degeneration.

Purpose To correlate changes in choroidal thickness and vascularity index with disease activity in patients with neovascular age-related macular degeneration (nAMD). Methods Eyes diagnosed with AMD that had two sequential visits within 12 months and that had no choroidal neovascularization (CNV) or had inactive CNV at the first visit were included. Those that had active CNV at follow-up were enrolled as cases. Eyes that did not developed a CNV or that were still inactive at the second visit were enrolled as controls. Disease activity was based on optical coherence tomography (OCT) and fluorescein angiography findings. Subfoveal choroidal thickness (SCT), mean choroidal thickness (MCT), and choroidal vascularity index (CVI) were assessed on enhanced depth imaging OCT and compared between the baseline and follow-up visit. Subgroup analysis accounting for lesion type and previous treatment, if any, were performed. Results Sixty-five eyes from 60 patients (35 females) and 50 age- and sex-matched controls were included. At the active visit, cases had an increase from 164 ± 67 μm to 175 ± 70 μm in mean ± SD SCT and from 144 ± 45 μm to 152 ± 45 μm in MCT (both P < 0.0001). The mean CVI also increased at from 54.5% ± 3.3% to 55.4% ± 3.8% (P = 0.04). Controls did not show significant changes in choroidal measurements between the two visits. Mean SCT, MCT, and CVI values were similar for previously treated and treatment-naive eyes. Conclusions Choroidal thickness and CVI significantly increased with active disease in nAMD eyes. Changes in choroidal thickness may predict CNV development or recurrence before they are otherwise evident clinically

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

Semi-automated quantification of hard exudates in colour fundus photographs diagnosed with diabetic retinopathy

Background: Hard exudates (HEs) are the classical sign of diabetic retinopathy (DR) which is one of the leading causes of blindness, especially in developing countries. Accordingly, disease screening involves examining HEs qualitatively using fundus camera. However, for monitoring the treatment response, quantification of HEs becomes crucial and hence clinicians now seek to measure the area of HEs in the digital colour fundus (CF) photographs. Against this backdrop, we proposed an algorithm to quantify HEs using CF images and compare with previously reported technique using ImageJ. Methods: CF photographs of 30 eyes (20 patients) with diabetic macular edema were obtained. A robust semi-automated algorithm was developed to quantify area covered by HEs. In particular, the proposed algorithm, a two pronged methodology, involved performing top-hat filtering, second order statistical filtering, and thresholding of the colour fundus images. Subsequently, two masked observers performed HEs measurements using previously reported ImageJ-based protocol and compared with those obtained through proposed method. Intra and inter-observer grading was performed for determining percentage area of HEs identified by the individual algorithm. Results: Of the 30 subjects, 21 were males and 9 were females with a mean age of the 50.25 ± 7.80 years (range 33-66 years). The correlation between the two measurements of semi-automated and ImageJ were 0.99 and 0.99 respectively. Previously reported method detected only 0-30% of the HEs area in 9 images, 30-60% in 12 images and 60-90% in remaining images, and more than 90% in none. In contrast, proposed method, detected 60-90% of the HEs area in 13 images and 90-100% in remaining 17 images. Conclusion: Proposed method semi-automated algorithm achieved acceptable accuracy, qualitatively and quantitatively, on a heterogeneous dataset. Further, quantitative analysis performed based on intra- and inter-observer grading showed that proposed methodology detects HEs more accurately than previously reported ImageJ-based technique. In particular, we proposed algorithm detect faint HEs also as opposed to the earlier method

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

Choroidal vascularity map in unilateral central serous chorioretinopathy: A comparison with fellow and healthy eyes

Background: To map the choroidal vascularity index and compare two eyes in patients with unilateral central serous chorioretinopathy (CSCR). Methods: This was a retrospective, observa-tional study performed in patients with unilateral CSCR. Choroidal thickness (CT) and Choroidal vascularity index (CVI) were measured and mapped in various zones according to the early treatment diabetic retinopathy (ETDRS) grid. Results: A total of 20 CSCR patients (20 study and 20 fellow eyes) were included in the study. Outer nasal region CT was seen to be significantly lower than central CT (p = 0.042) and inner nasal CT (p = 0.007); outer ring CT was significantly less than central (p = 0.04) and inner ring (p = 0.01) CT in CSCR eyes. On potting all the CVI values against the corresponding CT values, a positive correlation was seen in CSCR eyes (r = 0.54, p &lt; 0.01), which was slightly weaker in fellow eyes (r = 0.3, p &lt; 0.01) and a negative correlation was seen in healthy eyes (r = −0.262, p &lt; 0.01). Conclusions: Correlation between CVI and CT was altered in CSCR eyes as compared to fellow and normal eyes with increasing CVI towards the center of the macula and superiorly in CSCR eyes