title: Clinical, histological and ultrastructural studies of the posterior hyaloid membrane.
abstract: OBJECTIVE
  To investigate the histological, immunohistochemical and ultrastructural features of the posterior hyaloid membrane (PHM) in its naturally separated state in patients without previous surgery and slit-lamp documentation of antemortem posterior vitreous detachment (PVD).
  
  
  METHODS
  A prospective study was commenced in 1992 to recruit patients with physiological PVD from an unselected group of general medical inpatients and ascertain the prevalence of PVD. Postmortem specimens subsequently available were studied to analyse the clinicopathological correlation and processed using standard techniques for histology, immunohistochemistry and electron microscopy.
  
  
  RESULTS
  Eighty-five patients were examined with ages ranging from 68 to 98 yrs (mean 83.4 yrs). The posterior hyaloid membrane had clearly separated from the retina in 66% of eyes. Twenty-nine eyes from 15 patients were subsequently studied pathologically. The posterior hyaloid membrane exhibited a uniform cellular component, most densely populated around the Weiss' ring. The cells were characterised by oval or round nuclei, indistinct cytoplasm and were only seen within, or abutting, the weakly eosinophilic posterior hyaloid membrane. The posterior aspect of the posterior hyaloid membrane showed a convoluted appearance staining lightly with haematoxylin and eosin. The detached posterior hyaloid membrane exhibited focal positivity for GFAP and type IV collagen. Electron microscopy demonstrates both fibres and basement membrane associated with the cellular component including hemi-desmosome attachment plaques between the cells and basement membrane.
  
  
  CONCLUSIONS
  This study illustrates some of the structural differences between the posterior hyaloid membrane and the cortical vitreous gel it envelopes and demonstrates the presence of cells intimately associated with the posterior hyaloid membrane in its naturally separated state. We propose the cellular population integral to the PHM to be designated as laminocytes in order to emphasise their type IV collagen/basement membrane association and planar array within the membrane which separates at posterior vitreous detachment.
authors.affiliation: Vitreoretinal Service Box 41 Addenbrooke's NHS Trust Hills Road Cambridge, UK. mps34@cam.ac.uk
authors.forename: M P
authors.initials: MP
authors.lastname: Snead
authors.forename: D R J
authors.initials: DR
authors.lastname: Snead
authors.forename: A J
authors.initials: AJ
authors.lastname: Richards
authors.forename: J B
authors.initials: JB
authors.lastname: Harrison
authors.forename: A V
authors.initials: AV
authors.lastname: Poulson
authors.forename: A H C
authors.initials: AH
authors.lastname: Morris
authors.forename: R M
authors.initials: RM
authors.lastname: Sheard
authors.forename: J D
authors.initials: JD
authors.lastname: Scott
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001485:Basement Membrane / Q000648:ultrastructure; D003094:Collagen / Q000032:analysis; D006801:Humans; D008854:Microscopy, Electron; D011446:Prospective Studies; D014822:Vitreous Body / Q000737:chemistry / Q000648:ultrastructure*; D020255:Vitreous Detachment / Q000378:metabolism / Q000473:pathology*
chemical_list: D003094:Collagen