choroid Flashcards
what is the choroid?
the middle layer of eye in the posterior globe interior to it is the retina and external to it sclera
how does the thickness of the choroid vary?
- thickness of choroid varies with location
anteriorly near ora serrata = as little as 60um
behind macular region = choroid is thick 160um
how thick is the choroid in a myopic eye ?
myopic eye - the eye is elongated so coat is stretched making the choroid thin
what are the three coats of the back of the eye?
- sclera - made of irregular dense collagen fibres
- choroid-
- retina-
what separates the choroid and sclera?
suprachoroid- outer boundary of choroid
what separates the choroid from the retina?
Bruch’s membrane
what is between the suprachoroid and Bruch’s membrane?
3 layers of blood vessels
what are the layers of the choroid?
- suprachoroid
- stroma - Haller’s layer
- Sattler’s layer - choriocapillaris
- Bruch’s membrane
what is the choroid mainly made of ?
the choroid is mainly blood vessels
- blood vessels near the sclera are very large
- blood vessels near the retina are smaller
what are the three layers of vessels in the choroid?
Haller’s layer - large which divide into
Sattler’s - medium
choriocapillaris - smaller
what is suprachoroid
- also known as lamina suprachoroidea or lamina fusca
- composed of fine network of collagen fibres and between collagen fibres we have ciliary nerves running from front to back of eye which supply uveal tract
- also find some melanin granules
- a lot of nerves travel
what is the whole layer of blood vessels know as ?
- choroidal stroma- which is split into Haller’s layer which is split into Sattler’s internal to that is choriocapillaris
what does choroidal vessels constitute of ?
- choroidal vessels constitute a compressed hierarchy
- vessel branching occurs close together which produces a layered appearance
what does bruch’s membrane separate ?
RPE - retinal pigment epithelium from choriocapillaris
what is Bruch’s membrane made of ?
non-cellular connective tissue
what are the layer of Bruch’s membrane? from external to internal
- basal lamina - secreted by choriocapillaris
- collagen - provided by choriocapillaris
- elastin
- collagen- provided by RPE
- basal lamina - secreted by RPE-
what is the thickness of Bruch’s membrane?
2-6um
increases with age
what does choriocapillaris supply?
- choriocapillaris supplies nutrients to the outer five layers of the retina
what happens if Bruch’s membrane become thicker?
- the thickness of bruch’s membrane has some significance because if it gets thicker than the transport of nutrients from choriocapillaris into retina can become impaired
- causing Drusen
what is Drusen?
common pathology - accumulation of debris in bruch’s membrane
- Drusen can push the retina away from Bruch’s membrane and away from choriocapillaris
- can impair flow of nutriebts
what happens if Bruch’s membrane breaks?
- if it breaks you get local retinal edema - fluid gets through choriocapillaris and through the retina
what is function of Bruch’s membrane?
- limits fluid movements towards the retina under normal conditions
- very important in retinal pathologies
why is choriocapillaris important?
- provide nutrients to the outer five layers of the retina
where the 5 inner layers of retina recveive blood supply from ?
- from the central retinal artery