title: Ultrastructure of the posterior corneal stroma.
abstract: OBJECTIVE
  To reinvestigate the ultrastructure of the posterior stroma of the human cornea and to correlate the findings with the stromal behavior after big-bubble creation.
  
  
  METHODS
  Observational consecutive 3-center case series.
  
  
  METHODS
  Fresh corneoscleral buttons from human donors (n = 19) and organ-cultured corneoscleral buttons (n = 10) obtained after Descemet's membrane endothelial keratoplasty.
  
  
  METHODS
  Corneal specimens were divided into central (3 mm), mid peripheral (8 mm), and peripheral parts by trephination and processed for transmission electron microscopic and immunohistochemical analyses. A big bubble was created by air injection into the stroma of organ-cultured corneas before fixation.
  
  
  METHODS
  The distance of keratocytes to Descemet's membrane, number of collagen lamellae between keratocytes and Descemet's membrane, diameter and arrangement of collagen fibrils, thickness of stromal lamella created by air injection, and immunopositivity for collagen types III, IV, and VI.
  
  
  RESULTS
  Stromal keratocytes were observed at variable distances from Descemet's membrane, increasing from 1.5 to 12 μm (mean, 4.97±2.19 μm) in the central, 3.5 to 14 μm (mean, 8.03±2.47 μm) in the midperipheral, and 4.5 to 18 μm (mean, 9.77±2.90 μm) in the peripheral regions. The differences in mean distances were significant (P < 0.0001). The number of collagen lamellae between Descemet's membrane and most posterior keratocytes varied from 2 to 10 and the diameter of collagen fibrils averaged 23.5±1.8 nm and corresponded with that of the remaining stroma. A thin layer (0.5-1.0 μm thick) of randomly arranged, unaligned collagen fibers, which was positive for collagen types III and VI, was observed at the Descemet-stroma interface. The residual stromal sheet separated by air injection in 8 of 10 donor corneas varied in thickness from 4.5 to 27.5 μm, even within individual corneas (≤3-fold), and was composed of 5 to 11 collagen lamellae that revealed keratocytes on their anterior surface and in between.
  
  
  CONCLUSIONS
  Barring an anchoring zone of interwoven collagen fibers at the Descemet-stroma interface, the findings did not provide any evidence for the existence of a distinctive acellular pre-Descemet's stromal layer in the human cornea. The intrastromal cleavage plane after pneumodissection seems to be nonreproducibly determined by the intraindividually and interindividually variable distances of keratocytes to Descemet's membrane.
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. Electronic address: ursula.schloetzer-schrehardt@uk-erlangen.de.
authors.forename: Ursula
authors.initials: U
authors.lastname: Schlötzer-Schrehardt
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Bjoern O
authors.initials: BO
authors.lastname: Bachmann
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Theofilos
authors.initials: T
authors.lastname: Tourtas
authors.affiliation: The Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Andre A M
authors.initials: AA
authors.lastname: Torricelli
authors.affiliation: The Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Arun
authors.initials: A
authors.lastname: Singh
authors.affiliation: Jules Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California.
authors.forename: Sheyla
authors.initials: S
authors.lastname: González
authors.affiliation: Jules Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California.
authors.forename: Hua
authors.initials: H
authors.lastname: Mei
authors.affiliation: Jules Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California.
authors.forename: Sophie X
authors.initials: SX
authors.lastname: Deng
authors.affiliation: The Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Wilson
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Friedrich E
authors.initials: FE
authors.lastname: Kruse
mesh_terms: D000368:Aged; D024061:Collagen Type III / Q000378:metabolism; D024141:Collagen Type IV / Q000378:metabolism; D024142:Collagen Type VI / Q000378:metabolism; D003316:Corneal Diseases / Q000601:surgery; D060527:Corneal Keratocytes / Q000378:metabolism / Q000648:ultrastructure*; D003319:Corneal Stroma / Q000378:metabolism / Q000601:surgery / Q000648:ultrastructure*; D003886:Descemet Membrane / Q000378:metabolism / Q000648:ultrastructure*; D057111:Descemet Stripping Endothelial Keratoplasty; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D009924:Organ Culture Techniques; D014019:Tissue Donors
chemical_list: D024061:Collagen Type III; D024141:Collagen Type IV; D024142:Collagen Type VI