title: Identification of human orbital lymphatics.
abstract: OBJECTIVE
  To identify lymphatic vessels in the human orbit.
  
  
  METHODS
  Lymphatic and blood capillaries were distinguished histochemically by light microscopy using a 5'-nucleotidase (5'-Nase) and alkaline phosphatase (ALPase) double staining method. Identification of lymphatic vessels was based on strict morphologic criteria combined with specific 5'-Nase staining.
  
  
  RESULTS
  The presence of conjunctival lymphatics was confirmed and used as a control tissue. Lymphatic vessels were identified in the lacrimal gland and in the dura mater of the optic nerve. Structures demonstrating positive 5'-Nase staining at the orbital apex were highly suggestive of lymphatics but did not meet the morphologic criteria established. Lymphatic vessels were not identified in the extraocular muscles or orbital fat.
  
  
  CONCLUSIONS
  To the authors' knowledge, this study presents the first evidence for lymphatic capillaries in the dura mater of the human optic nerve and lacrimal gland.
authors.affiliation: Department of Ophthalmology, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Gausas
authors.forename: R S
authors.initials: RS
authors.lastname: Gonnering
authors.forename: B N
authors.initials: BN
authors.lastname: Lemke
authors.forename: R K
authors.initials: RK
authors.lastname: Dortzbach
authors.forename: D D
authors.initials: DD
authors.lastname: Sherman
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism; D000273:Adipose Tissue / Q000033:anatomy & histology / Q000201:enzymology; D000469:Alkaline Phosphatase / Q000378:metabolism; D001808:Blood Vessels / Q000033:anatomy & histology / Q000201:enzymology; D003228:Conjunctiva / Q000033:anatomy & histology / Q000201:enzymology; D006801:Humans; D007124:Immunoenzyme Techniques; D007421:Intestine, Small / Q000033:anatomy & histology / Q000201:enzymology; D007765:Lacrimal Apparatus / Q000033:anatomy & histology / Q000201:enzymology; D008208:Lymphatic System / Q000033:anatomy & histology* / Q000201:enzymology; D009801:Oculomotor Muscles / Q000033:anatomy & histology / Q000201:enzymology; D009900:Optic Nerve / Q000033:anatomy & histology / Q000201:enzymology; D009915:Orbit / Q000033:anatomy & histology* / Q000201:enzymology
chemical_list: D000469:Alkaline Phosphatase; D015720:5'-Nucleotidase