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Cross-Sectional and Longitudinal Assessment of Retinal Sensitivity in Patients With Childhood-Onset Stargardt Disease
摘要： Purpose: We assess cross-sectional and longitudinal microperimetry and full-field static perimetry-derived retinal sensitivity with conventional and volumetric indices of retinal function in childhood-onset Stargardt disease (STGD1). Methods: Subjects with molecularly confirmed childhood-onset STGD1 underwent full-field static perimetry and/or microperimetry using custom designed grids. Mean sensitivity (MS) and total volume (VTOT) were computed for each microperimetry test. MS, VTOT, and central field volume (V30) were computed for each full-field static perimetry test. Subjects under 18 years old at baseline were classified as children and subjects 18 years or older as adults. Results: A total of 43 children (mean age at baseline, 13.0 years; range, 8–17) and 13 adults (mean age at baseline, 23.1 years; range, 18–32) were included in the analysis. For full-field static perimetry and microperimetry for both subgroups, intraclass correlation coefficient results for MS and volumetric indices were good to excellent, indicating strong test–retest reliability. Interocular symmetry in terms of baseline measurements and the annual rate of progression was observed. A greater rate of progression was observed in childhood. Conclusions: To our knowledge, this is the first prospective study of retinal sensitivity in a large cohort of molecularly confirmed subjects with childhood-onset STGD1 demonstrating that children with STGD1 can reliably undertake detailed functional testing. Moreover, using custom designed grids and subsequent topographic analysis, volumetric indices of retinal function provide a reliable measure of retinal sensitivity.
关键词： endpoints,Stargardt disease,retina,clinical trials,ABCA4,perimetry,visual field,STGD1,Retinal sensitivity
更新于2025-09-23 15:22:29
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Expression of ABCA4 in the retinal pigment epithelium and its implications for Stargardt macular degeneration
摘要： Recessive Stargardt disease (STGD1) is an inherited blinding disorder caused by mutations in the Abca4 gene. ABCA4 is a flippase in photoreceptor outer segments (OS) that translocates retinaldehyde conjugated to phosphatidylethanolamine across OS disc membranes. Loss of ABCA4 in Abca4?/? mice and STGD1 patients causes buildup of lipofuscin in the retinal pigment epithelium (RPE) and degeneration of photoreceptors, leading to blindness. No effective treatment currently exists for STGD1. Here we show by several approaches that ABCA4 is additionally expressed in RPE cells. (i) By in situ hybridization analysis and by RNA-sequencing analysis, we show the Abca4 mRNA is expressed in human and mouse RPE cells. (ii) By quantitative immunoblotting, we show that the level of ABCA4 protein in homogenates of wild-type mouse RPE is about 1% of the level in neural retina homogenates. (iii) ABCA4 immunofluorescence is present in RPE cells of wild-type and Mertk?/? but not Abca4?/? mouse retina sections, where it colocalizes with endolysosomal proteins. To elucidate the role of ABCA4 in RPE cells, we generated a line of genetically modified mice that express ABCA4 in RPE cells but not in photoreceptors. Mice from this line on the Abca4?/? background showed partial rescue of photoreceptor degeneration and decreased lipofuscin accumulation compared with nontransgenic Abca4?/? mice. We propose that ABCA4 functions to recycle retinaldehyde released during proteolysis of rhodopsin in RPE endolysosomes following daily phagocytosis of distal photoreceptor OS. ABCA4 deficiency in the RPE may play a role in the pathogenesis of STGD1.
关键词： Stargardt disease,retinal pigment epithelium,lipofuscin,ABCA4,bisretinoid
更新于2025-09-23 15:21:21
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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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Monoallelic <i>ABCA4</i> Mutations Appear Insufficient to Cause Retinopathy: A Quantitative Autofluorescence Study
摘要： PURPOSE. To investigate the effect of ABCA4 mutation status on lipofuscin-related quantitative autofluorescence (qAF) in humans and on bisretinoid accumulation in mice. METHODS. Genotyped parents (n ? 26; age 37–64 years) of patients with biallelic ABCA4-related retinopathy underwent in-depth retinal phenotyping including qAF imaging as a surrogate measure for RPE lipofuscin accumulation. In addition, bisretinoids as the main components of autofluorescent lipofuscin at the ocular fundus were quantified in Abca4(cid:2)/(cid:2), Abca4t/(cid:2), and wild-type mice. RESULTS. Index patients showed a retinal phenotype characteristic for ABCA4-related retinopathy, including increased qAF levels. In contrast, qAF measures in carriers of only one ABCA4 mutation were not different from age-matched controls in this sample, and there was no difference between truncating and missense mutations. Also, none of these carriers presented an abnormal phenotype on conventional imaging. One parent with ABCA4-related retinopathy and increased qAF carried an additional ABCA4 mutation, explaining the phenotype under a recessive disease model (pseudodominance). Biochemical analysis in the mouse model revealed direct downstream products (A2PE-H2, at-RALdimer-PE) of the ABCA4 substrate N-Ret-PE to be similar in wild-type and Abca4t/(cid:2) mice. Both bisretinoids were 12- to 18-fold increased in Abca4(cid:2)/(cid:2) mice. Levels of A2E and A2PE in Abca4t/(cid:2) mice were in between those measured in wild-type and Abca4(cid:2)/(cid:2) mice. CONCLUSIONS. This study indicates that carriers of monoallelic ABCA4 mutations are phenotypically normal. However, biochemical analysis in the Abca4-deficient mouse model suggests detectable effects of one mutation in ABCA4 on the molecular level. The findings may have implications for therapeutic approaches such as gene replacement therapy.
关键词： quantitative fundus autofluorescence,carrier,monoallelic,phenotype,Abca4
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