Morphology and permeability of blood vessels in the prenatal rhesus monkey eye: How plasma components diffuse into the intraocular fluids during development

E. Townes-Anderson, G. Raviola

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


In order to identify the structures which allow blood-borne macromolecules to penetrate into the ocular chambers during development, we investigated the vasculature of prenatal rheusus monkey eyes, 30-160±2-days-old. The morphology of the blood vessels was examined with light microscopy, conventional electron microscopy, and the freeze-fracturing technique; the permeability properties of the vessels were tested with intravascular injections of horseradish peroxidase. The vessels of the prenatal intraocular blood system (the hyaloid artery, the vasa hyaloidea propria, the tunica vasculosa lentis and the pupillary membrane) and the developing retinal vessels are lined by a continuous endothelium whose cells are joined by zonular tight junctions. They are all impermeable to circulating horserdish peroxidase. In contrast, the uveal vessels are fenestrated as soon as they are formed, their endothelial cells are joined by open junctions and they are highly permeable to the tracer which diffuses throughout the uveal mesenchyme. Furthermore, fenestrated vessels of uveal origin, by extending around the margin of the optic cup, penetrate into the forming ocular chambers; we have termed these vessels intracameral uveal vessels. As the anterior segment matures, the intracameral fenestrated vessels slowly recede into the iris until, by birth, they reach no further than the root of the iris. Horseradish peroxidase diffuses into the ocular fluid both from the intracameral uveal vessels and from the connective tissue spaces of the uveal mesenchyme at the angle which freely communicate with the anterior chamber. This leakage, initially pronounced, ceases shortly before birth. We conclude (1) that diffusion from leaky uveal vessels explains the presence of large amounts of plasma components in the ocular fluids of the immature eye and (2) that the transient existence of permeable vessels at the angle contributes to the changing composition of the aqueous humor during development.

Original languageEnglish (US)
Pages (from-to)203-230
Number of pages28
JournalExperimental Eye Research
Issue number3
StatePublished - Sep 1982
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Sensory Systems
  • Cellular and Molecular Neuroscience
  • Ophthalmology


  • blood-ocular barriers
  • development
  • electron microscopy
  • freeze-fracturing
  • horseradish peroxidase
  • ocular vessels
  • permeability
  • rhesus monkey


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