title: Scanning electron microscopy of the trabecular meshwork: understanding the pathogenesis of primary angle closure glaucoma.
abstract: OBJECTIVE
  To study ultrastructural changes of the trabecular meshwork in acute and chronic primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) eyes by scanning electron microscopy.
  
  
  METHODS
  Twenty-one trabecular meshwork surgical specimens from consecutive glaucomatous eyes after a trabeculectomy and five postmortem corneoscleral specimens were fixed immediately in Karnovsky solution. The tissues were washed in 0.1 M phosphate buffer saline, post-fixed in 1% osmium tetraoxide, dehydrated in acetone series (30-100%), dried and mounted.
  
  
  RESULTS
  Normal trabecular tissue showed well-defined, thin, cylindrical uveal trabecular beams with many large spaces, overlying flatter corneoscleral beams and numerous smaller spaces. In acute PACG eyes, the trabecular meshwork showed grossly swollen, irregular trabecular endothelial cells with intercellular and occasional basal separation with few spaces. Numerous activated macrophages, leucocytes and amorphous debris were present. Chronic PACG eyes had a few, thickened posterior uveal trabecular beams visible. A homogenous deposit covered the anterior uveal trabeculae and spaces. Converging, fan-shaped trabecular beam configuration corresponded to gonioscopic areas of peripheral anterior synechiae. In POAG eyes, anterior uveal trabecular beams were thin and strap-like, while those posteriorly were wide, with a homogenous deposit covering and bridging intertrabecular spaces, especially posteriorly. Underlying corneoscleral trabecular layers and spaces were visualized in some areas.
  
  
  CONCLUSIONS
  In acute PACG a marked edema of the endothelium probably contributes for the acute and marked intraocular pressure (IOP) elevation. Chronically raised IOP in chronic PACG and POAG probably results, at least in part, from decreased aqueous outflow secondary to widening and fusion of adjacent trabecular beams, together with the homogenous deposit enmeshing trabecular beams and spaces.
authors.affiliation: Glaucoma Research Facility and Clinical Services, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Ramanjit
authors.initials: R
authors.lastname: Sihota
authors.forename: Amita
authors.initials: A
authors.lastname: Goyal
authors.forename: Jasbir
authors.initials: J
authors.lastname: Kaur
authors.forename: Viney
authors.initials: V
authors.lastname: Gupta
authors.forename: Tapas C
authors.initials: TC
authors.lastname: Nag
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors; D014129:Trabecular Meshwork / Q000648:ultrastructure*