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Visible-light optical coherence tomography-based multimodal system for quantitative fundus autofluorescence imaging
摘要： Fundus autofluorescence (FAF) imaging is commonly used in ophthalmic clinics for diagnosis and monitoring of retinal diseases. Lipofuscin in the retinal pigment epithelium (RPE), with A2E as its most abundant component and a visual cycle by-product, is the major fluorophore of FAF. Lipofuscin accumulates with age and is implicated in degenerative retinal diseases. The amount of lipofuscin in RPE can be assessed by quantitative measurement of FAF. However, the currently available FAF imaging technologies are not capable of quantifying the absolute intensity of FAF, which is essential for comparing images from different individuals, and from the same individual over time. One major technical difficulty is to compensate the signal attenuation by ocular media anterior to the RPE (pre-RPE media). FAF intensity is also influenced by fluctuations in imaging conditions such as illumination power and detector sensitivity, all of which need to be compensated. In this review, we present the concept and research progress of using visible-light optical coherence tomography-based simultaneous multimodal retinal imaging to compensate signal attenuation by pre-RPE media and the influence of parameters of the acquisition system for accurate measurement of FAF intensities.
关键词： fundus autofluorescence imaging,multimodal imaging,retinal pigment epithelium lipofuscin,Visible-light optical coherence tomography,retinal imaging,fluorescence quantification
更新于2025-09-09 09:28:46
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Human Retinal Pigment Epithelium: In Vivo Cell Morphometry, Multispectral Autofluorescence, and Relationship to Cone Mosaic
摘要： PURPOSE. To characterize in vivo morphometry and multispectral autofluorescence of the retinal pigment epithelial (RPE) cell mosaic and its relationship to cone cell topography across the macula. METHODS. RPE cell morphometrics were computed in regularly spaced regions of interest (ROIs) from contiguous short-wavelength autofluorescence (SWAF) and photoreceptor reflectance images collected across the macula in one eye of 10 normal participants (23–65 years) by using adaptive optics scanning light ophthalmoscopy (AOSLO). Infrared autofluorescence (IRAF) images of the RPE were collected with AOSLO in seven normal participants (22–65 years), with participant overlap, and compared to SWAF quantitatively and qualitatively. RESULTS. RPE cell statistics could be analyzed in 84% of SWAF ROIs. RPE cell density consistently decreased with eccentricity from the fovea (participant mean 6 SD: 6026 6 1590 cells/mm2 at fovea; 4552 6 1370 cells/mm2 and 3757 6 1290 cells/mm2 at 3.5 mm temporally and nasally, respectively). Mean cone-to-RPE cell ratio decreased rapidly from 16.6 at the foveal center to <5 by 1 mm. IRAF revealed cells in six of seven participants, in agreement with SWAF RPE cell size and location. Differences in cell fluorescent structure, contrast, and visibility beneath vasculature were observed between modalities. CONCLUSIONS. Improvements in AOSLO autofluorescence imaging permit efficient visualization of RPE cells with safe light exposures, allowing individual characterization of RPE cell morphometry that is variable between participants. The normative dataset and analysis of RPE cell IRAF and SWAF herein are essential for understanding microscopic characteristics of cell fluorescence and may assist in interpreting disease progression in RPE cells.
关键词： autofluorescence,retinal imaging,photoreceptors,retinal pigment epithelium,adaptive optics
更新于2025-09-09 09:28:46
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Degeneration of Photoreceptor Cells in Arylsulfatase G-Deficient Mice
摘要： Retinal degeneration is a common feature of several lysosomal storage disorders, including the mucopolysaccharidoses, a group of metabolic disorders that is characterized by widespread accumulation of glycosaminoglycans due to lysosomal enzyme dysfunction. We used a new mouse model of mucopolysaccharidosis IIIE to study the effect of Arylsulfatase G (ARSG) deficiency on retina integrity. The retina of Arsg knockout mice aged 1 to 24 months was studied by immunohistochemistry and Western blot analysis. Electron microscopic analyses were performed on retinas from 15- and 22-month-old animals. Photoreceptor and microglia cell numbers and retina thickness were determined to quantitatively characterize retinal degeneration in ARSG-deficient mice. Arsg knockout mice showed a progressive degeneration of photoreceptor cells starting between 1 and 6 months of age, resulting in the loss of more than 50% of photoreceptor cells in 24-month-old mice. Photoreceptor loss was accompanied by reactive astrogliosis, reactive microgliosis that was evident in the outer but not inner retina, and elevated expression levels of some lysosomal proteins. Electron microscopic analyses of retinas revealed no evidence for the presence of storage vacuoles. Of note, expression of ARSG protein in wild-type mice was detectable only in the RPE which, however, appeared morphologically unaffected in knockout mice at the electron microscopic level. To our knowledge, this is the first study demonstrating that ARSG deficiency results in progressive photoreceptor degeneration and dysregulation of various lysosomal proteins.
关键词： Sanfilippo syndrome,mucopolysaccharidosis,retinal pigment epithelium,Arylsulfatase G,retina,neurodegeneration,photoreceptor cells
更新于2025-09-09 09:28:46
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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
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Potential Therapeutic Agents Against Retinal Diseases Caused by Aberrant Metabolism of Retinoids
摘要： The retinoid (visual) cycle is a complex enzymatic pathway that operates in the retina for the regeneration of 11-cis-retinal (11-cis-Ral), the inherent visual chromophore indispensable for vision. De?ciencies in the retinoid metabolism are involved in pathologic mechanisms of several forms of retinal diseases including age-related macular degeneration, Stargardt’s disease, and Leber’s congenital amaurosis, for which no effective cures presently exist. Nevertheless, the interference of abnormal retinoid metabolism with chemicals has been considered to be a promising strategy aimed at alleviating these retinal dysfunctions. Moreover, since gene therapy is gaining increasing importance in clinical practice, the modulation of key enzymes implicated with the retinoid cycle at a genetic level will hold great promise for the treatment of patients with degenerative diseases of the retina.
关键词： metabolism,photoreceptor,visual chromophores,retinylamine,RPE65,retinal pigment epithelium,retinoid visual cycle,gene therapy,retinoids
更新于2025-09-04 15:30:14
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Knockdown of FOXO6 inhibits high glucose–induced oxidative stress and apoptosis in retinal pigment epithelial cells
摘要： Oxidative stress and apoptosis in retinal pigment epithelium cells are involved in the pathogenesis of diabetic retinopathy (DR). Forkhead box class O 6 (FOXO6) is a member of the FOXO family that can regulate diabetes‐induced oxidative stress. However, the role of FOXO6 in DR has not been clarified. The aim of the present study was to investigate the effects of FOXO6 on high glucose (HG)‐induced oxidative stress and apoptosis in ARPE‐19 cells. The results showed that FOXO6 was overexpressed in clinical vitreous samples from DR patients and in HG‐induced ARPE‐19 cells. Knockdown of FOXO6 by small interfeing RNA targeting FOXO6 (si‐FOXO6) mitigated the HG‐induced the production of reactive oxygen species and malondialdehyde, as well as the inhibition of superoxide dismutase activity. Knockdown of FOXO6 reduced the rate of cell apoptosis in HG‐induced ARPE‐19 cells. The increase in bax expression and decrease in bcl‐2 expression caused by HG stimulation were reversed by si‐FOXO6 transfection. Furthermore, knockdown of FOXO6 enhanced the activation of Akt/Nrf2 pathway in HG‐stimulated ARPE‐19 cells. Taken together, suppression of FOXO6 protects ARPE‐19 cells from HG‐induced oxidative stress and apoptosis, which is in part mediated by the activation of Akt/Nrf2 pathway.
关键词： Akt/Nrf2 pathway,oxidative stress,retinal pigment epithelium cells,forkhead box class O 6,diabetic retinopathy,apoptosis
更新于2025-09-04 15:30:14
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Lipofuscin-mediated photodynamic stress induces adverse changes in nanomechanical properties of retinal pigment epithelium cells
摘要： Retinal pigment epithelium (RPE) is an important part of the blood-retina barrier (BRB) that separates the retina from the choroid. Although melanin granules contribute to the mechanical stability of the BRB complex, it is unknown if the age pigment lipofuscin affects mechanical properties of the tissue. To address this issue the effect of sub-lethal photic stress mediated by phagocytized lipofuscin granules, isolated from RPE of human donors, on morphology and mechanical properties of ARPE-19 cells was investigated. Nanomechanical analysis using atomic force spectroscopy revealed that irradiation of cells containing lipofuscin granules with blue light induced significant softening of the cells, which was accompanied by substantial reorganization of the cell cytoskeleton due to peroxidation of cellular proteins. Our results indicate that lipofuscin-mediated photic stress can cause significant modification of the RPE cells with the potential to disturb biological function of the BRB complex.
关键词： photic stress,lipofuscin,Retinal pigment epithelium,nanomechanical properties,blood-retina barrier
更新于2025-09-04 15:30:14
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Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology
摘要： The purpose of this study was to demonstrate polarization-sensitive optical coherence tomography (PS-OCT) for imaging pigmented structures in the posterior eye segments of albino and pigmented rats and to correlate depolarization contrast of the retinal pigment epithelium (RPE) and choroid in in vivo PS-OCT to melanin pigmentation detected in postmortem histologic serial sections. In vivo three-dimensional PS-OCT imaging was performed in adult albino and pigmented rat eyes at 70-kHz A-line rate. Degree of polarization uniformity (DOPU) fundus maps and radial DOPU pro?les were generated. Postmortem histomorphologic analysis was performed in order to investigate melanin pigmentation of the RPE and choroid. Fundus pigmentation maps were extracted from histologic serial sections. Pigmentation pro?les were correlated to DOPU pro?les of the same eyes. Strong depolarization was found in the RPE/choroid complex of pigmented rats, whereas the same structures exhibited uniform polarization in albino rats. The difference between the depolarization characteristics between albino and pigmented animals was statistically signi?cant. In the fundus pigmentation maps, optical pigment density was zero in albino rat eyes. In pigmented rat eyes, a strong negative correlation between optical pigment density and DOPU was observed. This in vivo and ex vivo investigation of posterior rat eyes indicates that melanin is the cause of depolarization in retinal PS-OCT images. It further demonstrates that melanin pigmentation in the RPE and choroid can be quanti?ed via depolarization imaging and therefore suggests that PS-OCT is a useful tool for the noninvasive quantitative assessment of pigmentary changes in vision-threatening diseases such as age-related macular degeneration.
关键词： choroid,melanin,optical coherence tomography,depolarization,retinal pigment epithelium,polarization sensitive devices
更新于2025-09-04 15:30:14