Ocular Barriers Flashcards
What are the two ocular barriers of the eye?
blood-aqueous and blood-retina
What does the corneal epithelium lack that most barrier epithelium contain?
tight (zonula occluddens-type) junctions
Where does the blood-aqueous barrier take place?
the non-pigmented ciliary epithelium (tight junctions between). Also some tight junctions between the vascular endothelium of the iris vessels.
Which barrier is more effective and why?
The blood-retina barrier is more effective. The blood-aqueous barrier still allows proteins into the anterior chamber via pinocytosis and openings in the rest of the anterior uvea.
Is there a barrier for movement of solutes between the aqueous humor and vitreous?
no
Briefly characterize prostaglandin synthesis and release in the eye?
synthesized in large amounts from arachadonc acid found in cell membrane phospholipids after trauma, iridocyclitis and intraocular surgery.
What is thought to be primarily responsible for blood-aqueous barrier breakdown following anterior chamber paracentesis?
prostaglandin synthesis and release
What are the two portions of the blood-retinal barrier?
- endothelia (endothelium of the retinal vessels)
- epithelial (retinal pigment epithelium)
What is the function of the epithelial (RPE) barrier?
Prevents diffusion of choroidal tissue fluid (similar to plasma) to the retina.
How do nutrients from the choroidal tissue pass to the retina?
Via the RPE, which takes in nutrients from the choroid and has specific mechanisms to pass those nutrients onto the retinal tissue. It’s important to realize that this is appears to be an active/selective process, thus the barrier function.
How does the blood-aqueous barrier affect the retina.
It is essentially responsible for keeping substances that could potentially pass into the aqueous humor from reaching the retina. This occurs via diffusion from the anterior chamber, around the lens, and through the vitreous.
What is the most permeable point of the blood retinal-retinal barrier?
optic nerve head (substances from the choroid can pass into the nerve)
