title: The Project MACULA Retinal Pigment Epithelium Grading System for Histology and Optical Coherence Tomography in Age-Related Macular Degeneration.
abstract: OBJECTIVE
  To seek pathways of retinal pigment epithelium (RPE) fate in age-related macular degeneration via a morphology grading system; provide nomenclature, visualization targets, and metrics for clinical imaging and model systems.
  
  
  METHODS
  Donor eyes with geographic atrophy (GA) or choroidal neovascularization (CNV) and one GA eye with previous clinical spectral-domain optical coherence tomography (SDOCT) imaging were processed for histology, photodocumented, and annotated at predefined locations. Retinal pigment epithelial cells contained spindle-shaped melanosomes, apposed a basal lamina or basal laminar deposit (BLamD), and exhibited recognizable morphologies. Thicknesses and unbiased estimates of frequencies were obtained.
  
  
  RESULTS
  In 13 GA eyes (449 locations), 'Shedding,' 'Sloughed,' and 'Dissociated' morphologies were abundant; 22.2% of atrophic locations had 'Dissociated' RPE. In 39 CNV eyes (1363 locations), 37.3% of locations with fibrovascular/fibrocellular scar had 'Entombed' RPE; 'Sloughed,' 'Dissociated,' and 'Bilaminar' morphologies were abundant. Of abnormal RPE, CNV and GA both had ~35% 'Sloughed'/'Intraretinal,' with more Intraretinal in CNV (9.5% vs. 1.8%). 'Shedding' cells associated with granule aggregations in BLamD. The RPE layer did not thin, and BLamD remained thick, with progression. Granule-containing material consistent with three morphologies correlated to SDOCT hyperreflective foci in the previously examined GA patient.
  
  
  CONCLUSIONS
  Retinal pigment epithelium morphology indicates multiple pathways in GA and CNV. Atrophic/scarred areas have numerous cells capable of transcribing genes and generating imaging signals. Shed granule aggregates, possibly apoptotic, are visible in SDOCT, as are 'Dissociated' and 'Sloughed' cells. The significance of RPE phenotypes is addressable in longitudinal, high-resolution imaging in clinic populations. Data can motivate future molecular phenotyping studies.
authors: Department of Ophthalmology University of Alabama School of Medicine, Birmingham, Alabama, United States 2Eye Clinic, Department of Clinical Science "Luigi Sacco," Sacco Hospital, University of Milan, Milan, Italy.
authors: Emma C
authors: EC
authors: Zanzottera
authors: Department of Ophthalmology University of Alabama School of Medicine, Birmingham, Alabama, United States.
authors: Jeffrey D
authors: JD
authors: Messinger
authors: Department of Ophthalmology University of Alabama School of Medicine, Birmingham, Alabama, United States 3University Hospital Würzburg, Department of Ophthalmology, Würzburg, Germany.
authors: Thomas
authors: T
authors: Ach
authors: Department of Ophthalmology, New York University School of Medicine, New York City, New York, United States.
authors: R Theodore
authors: RT
authors: Smith
authors: Department of Ophthalmology, New York University School of Medicine, New York City, New York, United States 5Vitreous Retina Macula Consultants of New York, New York, New York, United States 6LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear.
authors: K Bailey
authors: KB
authors: Freund
authors: Department of Ophthalmology University of Alabama School of Medicine, Birmingham, Alabama, United States.
authors: Christine A
authors: CA
authors: Curcio
mesh_terms: D020256:Choroidal Neovascularization / Q000473:pathology; D057092:Geographic Atrophy / Q000473:pathology; D006801:Humans; D008268:Macular Degeneration / Q000473:pathology*; D055213:Retinal Pigment Epithelium / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*