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[IEEE 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - New Delhi, India (2019.3.9-2019.3.15)] 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - Physics based Device Modeling of GaN High Electron Mobility Transistor (HEMT) for Terahertz Applications
摘要： Scanning laser ophthalmoscopes (SLOs) can be used for early detection of retinal diseases. With the advent of latest screening technology, the advantage of using SLO is its wide field of view, which can image a large part of the retina for better diagnosis of the retinal diseases. On the other hand, during the imaging process, artefacts such as eyelashes and eyelids are also imaged along with the retinal area. This brings a big challenge on how to exclude these artefacts. In this paper, we propose a novel approach to automatically extract out true retinal area from an SLO image based on image processing and machine learning approaches. To reduce the complexity of image processing tasks and provide a convenient primitive image pattern, we have grouped pixels into different regions based on the regional size and compactness, called superpixels. The framework then calculates image based features reflecting textural and structural information and classifies between retinal area and artefacts. The experimental evaluation results have shown good performance with an overall accuracy of 92%.
关键词： retinal artefacts extraction,Feature selection,retinal image analysis,scanning laser ophthalmoscope (SLO)
更新于2025-09-23 15:19:57
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Free Carrier Plasma GeSn Modulator for Mid-Infrared Integrated Microwave Photonics
摘要： Scanning laser ophthalmoscopes (SLOs) can be used for early detection of retinal diseases. With the advent of latest screening technology, the advantage of using SLO is its wide field of view, which can image a large part of the retina for better diagnosis of the retinal diseases. On the other hand, during the imaging process, artefacts such as eyelashes and eyelids are also imaged along with the retinal area. This brings a big challenge on how to exclude these artefacts. In this paper, we propose a novel approach to automatically extract out true retinal area from an SLO image based on image processing and machine learning approaches. To reduce the complexity of image processing tasks and provide a convenient primitive image pattern, we have grouped pixels into different regions based on the regional size and compactness, called superpixels. The framework then calculates image based features reflecting textural and structural information and classifies between retinal area and artefacts. The experimental evaluation results have shown good performance with an overall accuracy of 92%.
关键词： retinal artefacts extraction,Feature selection,retinal image analysis,scanning laser ophthalmoscope (SLO)
更新于2025-09-19 17:13:59
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MORE EFFECTIVE SCREENING FOR EPIRETINAL MEMBRANES WITH MULTICOLOR SCANNING LASER OPHTHALMOSCOPE THAN WITH COLOR FUNDUS PHOTOGRAPHS
摘要： Purpose: To assess the ability of the multicolor scanning laser ophthalmoscope (MC-SLO) to screen for epiretinal membranes (ERMs). Methods: A retrospective cross-sectional study of 35 eyes of 32 patients with an ERM detected by optical coherence tomography and 46 eyes of 23 healthy volunteers. The detection of the ERM was graded into three visibility scores—1, not visible, 2, barely visible, and 3, clearly visible—by retina specialists or by ophthalmology residents. The sensitivity and speci?city of the detection with the merged image of the MC-SLO or color fundus photographs (CFPs) were calculated. Results: The sensitivity for ERM detection in the MC-SLO and CFP were 91.4% and 65.7% by specialists and 97.1% and 60.0% by residents. The speci?city for both devices was 100% by specialists and residents. The visibility score for the MC-SLO images were signi?cantly higher than that for the CFP by both specialists and residents. In addition, the visibility score for the MC-SLO determined by residents was signi?cantly higher than that for the CFP by specialists. Conclusion: The detection of an ERM is better with the MC-SLO images than with CFP. Furthermore, the ERM detection in the MC-SLO images by residents was comparable to that by specialists.
关键词： epiretinal membrane,multicolor scanning laser ophthalmoscope
更新于2025-09-12 10:27:22
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Quantitative Fundus Autofluorescence and Optical Coherence Tomography in <i>PRPH2/RDS</i> - and <i>ABCA4</i> -Associated Disease Exhibiting Phenotypic Overlap
摘要： PURPOSE. To assess whether quantitative fundus autofluorescence (qAF), a measure of RPE lipofuscin, and spectral-domain optical coherence tomography (SD-OCT) can aid in the differentiation of patients with fundus features that could either be related to ABCA4 mutations or be part of the phenotypic spectrum of pattern dystrophies. METHODS. Autofluorescence images (308, 488-nm excitation) from 39 patients (67 eyes) were acquired with a confocal scanning laser ophthalmoscope equipped with an internal fluorescent reference and were quantified as previously described. In addition, horizontal SD-OCT images through the fovea were obtained. Patients were screened for ABCA4 and PRPH2/RDS mutations. RESULTS. ABCA4 mutations were identified in 19 patients (mean age, 37 ± 12 years) and PRPH2/RDS mutations in 8 patients (mean age, 48 ± 13 years); no known ABCA4 or PRPH2/RDS mutations were found in 12 patients (mean age, 48 ± 9 years). Differentiation of the groups using phenotypic SD-OCT and AF features (e.g., peripapillary sparing, foveal sparing) was not reliable. However, patients with ABCA4 mutations could be discriminated reasonably well from other patients when qAF values were corrected for age and race. In general, ABCA4 patients had higher qAF values than PRPH2/RDS patients, while most patients without mutations in PRPH2/RDS or ABCA4 had qAF levels within the normal range. CONCLUSIONS. The high qAF levels of ABCA4-positive patients are a hallmark of ABCA4-related disease. The reason for high qAF among many PRPH2/RDS-positive patients is not known; higher RPE lipofuscin accumulation may be a primary or secondary effect of the PRPH2/RDS mutation.
关键词： scanning laser ophthalmoscope,PRPH2/RDS,optical coherence tomography,quantitative fundus autofluorescence,retinal pigment epithelium,lipofuscin,recessive Stargardt disease,ABCA4,pattern dystrophy
更新于2025-09-11 14:15:04
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Flecks in Recessive Stargardt Disease: Short-Wavelength Autofluorescence, Near-Infrared Autofluorescence, and Optical Coherence Tomography
摘要： PURPOSE. We evaluated the incongruous observation whereby ?ecks in recessive Stargardt disease (STGD1) can exhibit increased short-wavelength auto?uorescence (SW-AF) that originates from retinal pigment epithelium (RPE) lipofuscin, while near-infrared AF (NIR-AF), emitted primarily from RPE melanin, is usually reduced or absent at ?eck positions. METHODS. Flecks in SW- and NIR-AF images and spectral-domain optical coherence tomography (SD-OCT) scans were studied in 19 STGD1 patients carrying disease-causing ABCA4 mutations. Fleck spatial distribution and progression were recorded in serial AF images. RESULTS. Flecks observed in SW-AF images typically colocalized with darkened foci in NIR-AF images; the NIR-AF pro?les were larger. The decreased NIR-AF signal from ?ecks preceded apparent changes in SW-AF. Spatiotemporal changes in ?eck distribution usually progressed centrifugally, but in one case centripetal expansion was observed. Flecks in SW-AF images corresponded to hyperre?ective deposits that progressively traversed photoreceptor-attributable bands in SD-OCT images. Outer nuclear layer (ONL) thickness negatively correlated with expansion of ?ecks from outer to inner retina. CONCLUSIONS. In the healthy retina, RPE lipofuscin ?uorophores form in photoreceptor cells but are transferred to RPE; thus the SW-AF signal from photoreceptor cells is negligible. In STGD1, NIR-AF imaging reveals that ?ecks are predominantly hypo?uorescent and larger and that NIR-AF darkening occurs prior to heightened SW-AF signal. These observations indicate that RPE cells associated with ?ecks in STGD1 are considerably changed or lost. Spectral-domain OCT ?ndings are indicative of ongoing photoreceptor cell degeneration. The bright SW-AF signal of ?ecks likely originates from augmented lipofuscin formation in degenerating photoreceptor cells impaired by the failure of RPE.
关键词： lipofuscin,fundus auto?uorescence,recessive Stargardt disease,optical coherence tomography,retinal pigment epithelium,ABCA4,scanning laser ophthalmoscope
更新于2025-09-09 09:28:46
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Quantitative Fundus Autofluorescence and Optical Coherence Tomography in <i>ABCA4</i> Carriers
摘要： PURPOSE. To assess whether carriers of ABCA4 mutations have increased RPE lipofuscin levels based on quantitative fundus auto?uorescence (qAF) and whether spectral-domain optical coherence tomography (SD-OCT) reveals structural abnormalities in this cohort. METHODS. Seventy-?ve individuals who are heterozygous for ABCA4 mutations (mean age, 47.3 years; range, 9–82 years) were recruited as family members of affected patients from 46 unrelated families. For comparison, 57 affected family members with biallelic ABCA4 mutations (mean age, 23.4 years; range, 6–67 years) and two noncarrier siblings were also enrolled. Auto?uorescence images (308, 488-nm excitation) were acquired with a confocal scanning laser ophthalmoscope equipped with an internal ?uorescent reference. The gray levels (GLs) of each image were calibrated to the reference, zero GL, magni?cation, and normative optical media density to yield qAF. Horizontal SD-OCT scans through the fovea were obtained and the thicknesses of the outer retinal layers were measured. RESULTS. In 60 of 65 carriers of ABCA4 mutations (age range, 9–60), qAF levels were within normal limits (95% con?dence level) observed for healthy noncarrier subjects, while qAF levels of affected family members were signi?cantly increased. Perifoveal ?eck-like abnormalities were observed in fundus AF images in four carriers, and corresponding changes were detected in the outer retinal layers in SD-OCT scans. Thicknesses of the outer retinal layers were within the normal range. CONCLUSIONS. With few exceptions, individuals heterozygous for ABCA4 mutations and between the ages of 9 and 60 years do not present with elevated qAF. In a small number of carriers, perifoveal ?eck-like changes were visible.
关键词： heterozygous carrier,retinal pigment epithelium,lipofuscin,recessive Stargardt disease,optical coherence tomography,quantitative fundus auto?uorescence,Abca4,scanning laser ophthalmoscope
更新于2025-09-04 15:30:14