week 3 Flashcards
Vitreous is attached to posterior lens surface by:
Vitreous is attached to posterior lens surface by Wieger’s ligament (not a true ligament)
Vitreous base divides the vitreous into:
Vitreous base divides the vitreal cortex into the anterior and posterior portions
vitreous composed of:
99% water…. increases as we get older
1% of solids: eg: proteins, hyaluronic acid, collagen filaments, hyalocytes,
albumin, glucose, absorbic acid, galactose
where is the vitreous base?
landmark is at the ora serrata and it extends anteriorly towards the pars plana and posteriorly to the peripheral retina (2 mm)
where are the anterior and posterior hyaloid membranes?
- anterior and posterior hyaloid membrane covers the vitreal cortex
- anterior is in front of vitreous base, posterior is behind it
- Ant hyaloid membrane runs from post lens surface to ora (extends from zonules to Weiger’s ligament)
- Posterior Hyaloid membrane runs from post edge of vitreal abse to ONH
what is Weiss’s ring?
detached/floating ring of Gartner at optic nerve/peripapillary vitreous attachment
3rd weakest vitreal attachment?
macular attachment
what is Cloquet’s Canal? where is it?
- S shaped optically empty space.
- runs from the lens to the optic disc.
- represents atrophic primary vitreous
- less visible with increasing age.
how can you examine the vitreous with a B scan?
B-Scan consists of focused, short wavelength, acoustic waves. Wavefront’s intraocular and orbital velocity
differs as it passes through various ocular structures.
rheology:
shift of vitreal cortex from gel to liquid
aging vitreal changes occur sooner for what type of people?
high myopes
what % of people with symptomatic PVD will develop retinal breaks?
15-35%
3 features of youthful vitreous?
avascular acellular fine collagen fibrils
what is synchisis senilis?
hyaluronic acid macromolecules break down and release water (liquefaction); allows collagen fibers to coalesce into larger fibers more visible in slit lamp
what is syneresis?
vitreous collapses and shrinks
How can “lacunae” in vit lead to PVD?
Can!lead!to PVD:!lacunae!may!coalesce!in!sup[post!cortex!and!break!through!
hyaloid!membrane.!Vitreous!collapses!and!shrinks!(Vitreal+Syneresis),!lifts!away!
from!ONH!and!macular!attachments!=!PVD
What gives vitreous its visco-elastic properties?
hyaluronic acid
what mainly contributes to strength of vitreal attachment at vit base?
alignment of fibers contributes to strength of attachment
what is vitrosin?
concentration of collagen-like material in the vitreous;
determines viscosity of vitreous, which is 4x that of water
what are lacunae made out of?
Lacunae contain hyaluronic acid and no collagen
Liquefaction and syneresis = ?
fibrillary degeneration
flashes are caused by:
phosphenes produced by traction on retina, opposite to site of traction
floaters are caused by:
Particles of vitreous, blood, retina, casting shadows on the retina
how long do floaters typically last?
~4-6w
(brain suppresses the floater so it is no longer bothersome)
**Should not change size or shape over time!
what are a few ways to check for PVD in slit lamp exam?
1) Weiss’s ring
2) optically empty space between a loose veil-like posterior membrane with direct focal illumination
“Inverted “J” space in between vitreous base and macula”
3) Look for small opacity temporal to macula
If it is Weiss’s ring, the floaters will be seen where in field?
Weiss’s ring- the floater will usually be in central vision
With symptomatic patients w/ PVD, there is a greater chance that there will be a retinal tear within ____
1 week
what can cause the vitreal heme?
- retinal tear will cause retinal vessels to bleed when the vitreous tugs on them – can also occur with a retinal detachment
- *Remember, often caused by NVE, NVD in diabetes