title: Quantitative Analysis of Outer Retinal Tubulation in Age-Related Macular Degeneration From Spectral-Domain Optical Coherence Tomography and Histology.
abstract: To assess outer retinal tubulation (ORT) morphology from spectral-domain optical coherence tomography (SD-OCT) volumes and donor eye histology, analyze ORT reflectivity, and estimate the number of cones surviving in ORT.
  
  
  
  In SD-OCT volumes from nine patients with advanced AMD, ORT was analyzed en face and in B-scans. The hyperreflective ORT border in cross-section was delineated and surface area calculated. Reflectivity was compared between ORT types (Closed, Open, Forming, and Branching). A flatmount retina from a donor with neovascular AMD was labeled to visualize the external limiting membrane that delimits ORT and allow measurements of cross-sectional cone area, center-to-center cone spacing, and cone density. The number of cones surviving in ORT was estimated.
  
  
  
  By en face SD-OCT, ORT varies in complexity and shape. Outer retinal tubulation networks almost always contain Closed cross-sections. Spectral-domain OCT volumes containing almost exclusively Closed ORTs showed no significant direction-dependent differences in hyperreflective ORT border intensity. The surface areas of partial ORT assessed by SD-OCT volumes ranged from 0.16 to 1.76 mm2. From the flatmount retina, the average cross-sectional area of cone inner segments was 49.1 ± 7.9 μm2. The average cone spacing was 7.5 ± 0.6 μm. Outer retinal tubulation cone density was 20,351 cones/mm2. The estimated number of cones in ORT in a macula ranged from 26,399 to 186,833 cones, which is 6% to 44% of the cones present in a healthy macula.
  
  
  
  These first estimates for cone density and number of cones surviving in ORT suggest that ORT formation considerably distorts the photoreceptor mosaic. Results provide additional insight into the reflectivity characteristics and number of ORT cones observable in living patients by SD-OCT, as cones persist and disease progresses.
authors.affiliation: Department of Ophthalmology University of Alabama School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States 2Vision Science Graduate Program, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Katie M
authors.initials: KM
authors.lastname: Litts
authors.affiliation: Department of Ophthalmology University of Alabama School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States 3Department of Ophthalmology, University Hospital Würzburg, Würzburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ach
authors.affiliation: Department of Ophthalmology University of Alabama School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States 4Department of Computer and Information Sciences, University of Alabama at Birmingham, Birmingham, Alabama, Unite.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Hammack
authors.affiliation: Department of Ophthalmology University of Alabama School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States 4Department of Computer and Information Sciences, University of Alabama at Birmingham, Birmingham, Alabama, Unite.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Sloan
authors.affiliation: Department of Ophthalmology University of Alabama School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Vitreous Retina Macula Consultants of New York, New York, New York, United States 6Department of Ophthalmology, New York University School of Medicine, New York, New York, United States.
authors.forename: K Bailey
authors.initials: KB
authors.lastname: Freund
authors.affiliation: Department of Ophthalmology University of Alabama School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Curcio
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D006801:Humans; D008268:Macular Degeneration / Q000473:pathology*; D008297:Male; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D017949:Retinal Cone Photoreceptor Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*