Sam Sadigh

University of Pennsylvania, Philadelphia, Pennsylvania, United States

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Publications (4)14.55 Total impact

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    ABSTRACT: Abstract Purpose/Aim: To investigate the relationship of drusen and photoreceptor abnormalities in African-American (AA) patients with intermediate non-neovascular age-related macular degeneration (AMD). Materials and methods: AA patients with intermediate AMD (n = 11; age 52-77 years) were studied with spectral-domain optical coherence tomography. Macular location and characteristics of large drusen (≥125 µm) were determined. Thickness of photoreceptor laminae was quantified overlying drusen and in other macular regions. A patient with advanced AMD (age 87) was included to illustrate the disease spectrum. Results: In this AA patient cohort, the spectrum of changes known to occur in AMD, including large drusen, sub-retinal drusenoid deposits and geographic atrophy, were identified. In intermediate AMD eyes (n = 17), there were 183 large drusen, the majority of which were pericentral in location. Overlying the drusen there was significant thinning of the photoreceptor outer nuclear layer (termed ONL(+)) as well as the inner and outer segments (IS + OS). The reductions in IS + OS thickness were directly related to ONL(+) thickness. In a fraction (∼8%) of paradrusen locations with normal lamination sampled within ∼280 µm of peak drusen height, ONL(+) was significantly thickened compared to age and retinal-location-matched normal values. Topographical maps of the macula confirmed ONL thickening in regions neighboring and distant to large drusen. Conclusions: We confirm there is a pericentral distribution of drusen across AA-AMD maculae rather than the central localization in Caucasian AMD. Reductions in the photoreceptor laminae overlying drusen are evident. ONL(+) thickening in some macular areas of AA-AMD eyes may be an early phenotypic marker for photoreceptor stress.
    Current eye research. 06/2014;
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    ABSTRACT: PURPOSE: To investigate the relationship between photoreceptor layers overlying and adjacent to large drusen in intermediate non-neovascular age-related macular degeneration (AMD). METHODS: Patients with AMD (n=41; ages 53-83 years) and elderly control subjects without eye disease (n=10; ages 51-79) were studied with SD-OCT (spectral-domain optical coherence tomography). Characteristics of large drusen (>125 µm) were measured and the thickness of photoreceptor laminae overlying drusen and in retinal regions neighboring the drusen were quantified. RESULTS: There were 750 large drusen in 63 early AMD eyes studied. The width of the drusen sampled averaged 352 (SD=153) µm and the height averaged 78 (SD=31) µm. There was significant reduction of the photoreceptor outer nuclear layer (ONL) thickness overlying 92% of the drusen. The thickness of the layer corresponding to photoreceptor inner and outer segments above drusen was also reduced, and the reduction was proportional to ONL thickness. In a substantial fraction (~20%) of normally laminated paradrusen locations sampled within ~300 µm of peak drusen height, ONL thickness was significantly increased compared to age and retinal-location-matched normal values. Topographical analyses of the macula showed ONL thickening occurring in paradrusen regions as well as retinal locations distant from drusen. CONCLUSIONS: Reductions in the photoreceptor laminae overlying drusen were detectable and this is consistent with histological studies revealing neuronal degeneration in AMD. ONL thickening in some macular areas of AMD eyes has not been previously reported and may be an early phenotypic marker for photoreceptor stress, as it has been speculated to be in hereditary retinal degenerations.
    Investigative ophthalmology & visual science 01/2013; · 3.43 Impact Factor
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    ABSTRACT: The GUCY2D gene encodes retinal membrane guanylyl cyclase (RetGC1), a key component of the phototransduction machinery in photoreceptors. Mutations in GUCY2D cause Leber congenital amaurosis type 1 (LCA1), an autosomal recessive human retinal blinding disease. The effects of RetGC1 deficiency on human rod and cone photoreceptor structure and function are currently unknown. To move LCA1 closer to clinical trials, we characterized a cohort of patients (ages 6 months-37 years) with GUCY2D mutations. In vivo analyses of retinal architecture indicated intact rod photoreceptors in all patients but abnormalities in foveal cones. By functional phenotype, there were patients with and those without detectable cone vision. Rod vision could be retained and did not correlate with the extent of cone vision or age. In patients without cone vision, rod vision functioned unsaturated under bright ambient illumination. In vitro analyses of the mutant alleles showed that in addition to the major truncation of the essential catalytic domain in RetGC1, some missense mutations in LCA1 patients result in a severe loss of function by inactivating its catalytic activity and/or ability to interact with the activator proteins, GCAPs. The differences in rod sensitivities among patients were not explained by the biochemical properties of the mutants. However, the RetGC1 mutant alleles with remaining biochemical activity in vitro were associated with retained cone vision in vivo. We postulate a relationship between the level of RetGC1 activity and the degree of cone vision abnormality, and argue for cone function being the efficacy outcome in clinical trials of gene augmentation therapy in LCA1.
    Human Molecular Genetics 10/2012; · 7.69 Impact Factor
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    ABSTRACT: We investigated the retinal disease due to mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in human patients and in an Rpgr conditional knockout (cko) mouse model. XLRP patients with RPGR-ORF15 mutations (n = 35, ages at first visit 5-72 years) had clinical examinations, and rod and cone perimetry. Rpgr-cko mice, in which the proximal promoter and first exon were deleted ubiquitously, were back-crossed onto a BALB/c background, and studied with optical coherence tomography and electroretinography (ERG). Retinal histopathology was performed on a subset. Different patterns of rod and cone dysfunction were present in patients. Frequently, there were midperipheral losses with residual rod and cone function in central and peripheral retina. Longitudinal data indicated that central rod loss preceded peripheral rod losses. Central cone-only vision with no peripheral function was a late stage. Less commonly, patients had central rod and cone dysfunction, but preserved, albeit abnormal, midperipheral rod and cone vision. Rpgr-cko mice had progressive retinal degeneration detectable in the first months of life. ERGs indicated relatively equal rod and cone disease. At late stages, there was greater inferior versus superior retinal degeneration. RPGR mutations lead to progressive loss of rod and cone vision, but show different patterns of residual photoreceptor disease expression. Knowledge of the patterns should guide treatment strategies. Rpgr-cko mice had onset of degeneration at relatively young ages and progressive photoreceptor disease. The natural history in this model will permit preclinical proof-of-concept studies to be designed and such studies should advance progress toward human therapy.
    Investigative ophthalmology & visual science 07/2012; 53(9):5594-608. · 3.43 Impact Factor