VITREOUS Flashcards
Which of the following structures is NOT adjacent to the vitreous?
Trabecular meshwork
other choices: pars plana/plicata, retina, zonules
The vitreous base straddles which 2 of the following structures?
Ora serrata, pars plana
Which of the following structures is most anterior?
Egger’s line
Which of the following clinical signs/findings is most suggestive of an acute PVD?
Flashes of light
A posterior vitreous detachment is least likely to cause which of the following retinal hemorrhages?
Dot/blot
other answers: flame, preretinal, vitreous
The major component of the vitreous is _______
water
The major components of the central part of the vitreous are: _________ and __________ while the outer part mainly contains ____________ and is called the ___________ of the vitreous.
The major components of the central part of the vitreous are hyaluronic acid and water, while the outer part mainly contains collagen (type 2) fibrils and is called the cortex of the vitreous.
Where does the posterior hyaloid membrane lie?
What is it composed of? _________ and is it a membrane?
Where is it discontinuous?
The posterior hyaloid membrane lies posterior to the vitreous base
– It lies adjacent to the retina
– It is continuous except at the optic disc where it has a ring like attachment at
the margin of the optic disc
*The anterior hyaloid membrane lies anterior to the vitreous base and adjacent to:
– posterior lens capsule
– zonules
– posterior chamber
– ciliary body processes of pars plicata of the ciliary body
– anterior part of pars plana of the ciliary body
The strongest vitreous attachment is the _______
what is it attached to here? _____________
The vitreous cortex is firmly attached at the
Vitreous base - straddles pars plana and peripheral retina adjacent to the ora serrata
▪ Strongest attachment site of the vitreous cortex
Where else does the vitreous attach posteriorly?
Margin of the optic disc (prepapillary hole; ring-like attachment)
Margin of macula (oval attachment)
ILM around retinal vessels
What is Wieger’s ligament? And what forms it? And how does it change with increased age?
Wieger’s ligament (hyaloidocapsular ligament) is the circular attachment of the anterior hyaloid membrane (anterior vitreous cortex) to the posterior lens capsule
- a ring with a central potential space (Berger’s space)
- The ligament weakens with advancing age
What does the vitreous weakly attach to?
The vitreous cortex is loosely attached to the ILM EVERYWHERE ELSE along the vitreoretinal interface, under normal conditions.
Which cells of the vitreous process antigens and may thereby increase an inflammatory response?
Hyalocytes - small population of cells that lie in the vitreous cortex near the retina & ciliary body (considered a type of hyalocyte)
*greatest density at the vitreous base
What is the patellar fossa?
Depression in the anterior hyaloid
membrane of the vitreous, where the lens can sit
What is the space of Berger?
A potential space behind the lens and anterior to the patellar fossa
- can have “space” here because lens & vitreous are juxtaposed but not joined
- bounded peripherally by inner edge of Wieger’s ligament
What happens as the vitreous undergoes liquefaction?
How does the vitreous change from young age (20 yrs.) to old age during this process?
The gel portion of the vitreous decreases & the liquid portion increases due to a redistribution of the collagen as the normal eye ages. “liquefaction” of the vitreous mainly occurs in the central vitreous. Pools of liquid vitreous are called lacunae (optically empty (black) spaces filled with liquefied vitreous & will coalesce over time into larger lacunae. The collagen fibrils will also continue to aggregate into larger whitish bundles over time)
What structures form a barrier to help prevent proteins from entering the vitreous and where are they located in the eye?
To prevent leakage of proteins into the vitreous (or else proteins in vitreous would scatter light), a barrier is formed by zonula occludens junctions of RPE cells, endothelial cells of retinal capillaries & unpigmented CB epithelial cells
How does liquefaction occur since number of collagen fibrils not change throughout life? Where does it occur in the vitreous?
What is a lacuna?
see previous question
Where does a PVD usually occur? Why does the vitreous collapse? Where does the liquid vitreous end up? Be specific as to location.
With a PVD the separation occurs posterior to the vitreous base; between the posterior hyaloid membrane & the internal limiting membrane of the retina
– The vitreous detachment usually occurs at the margin of the optic disc or at the
edge of the macula (since these attachments have weakened with age)
– Following the detachment, liquid vitreous will exit through the prepapillary hole
(around optic disc) or premacular hole (around the macula) and move into the potential space between the posterior hyaloid membrane of vitreous & ILM of the retina, filling the space.
– The volume displacement of liquid vitreous into the space between vitreous & ILM leads to inward collapse of the vitreous body (referred to as vitreous syneresis) & a PVD (but the vitreous is still attached anteriorly at the vitreous base).
What is Weiss’ ring? What causes it and what does it represent?
What symptoms does Weiss’ ring create?
If the vitreous detaches from the margin of the optic disc & peripapillary glial tissue is torn and remains attached to this vitreous cortex surrounding the prepapillary hole, it will be seen by the clinician as an “annular ring” floating in the vitreous just anterior to the retina or optic nerve called a Weiss’ ring
– Weiss’ ring is caused by vitreous detaching from the optic disc edge and represents the margin of the prepapillary hole.
Weiss’ ring appears as a partial or complete grey-brownish ring commonly seen during fundus examination with BIO.
– the patient may complain of a large floater (Weiss’ ring) that obstructs his/her view
What are 3 complications of a PVD? i.e. what are these patients at risk to develop and why?
- Flashes of light (due to vitreoretinal adhesions tugging on retina and stimulating photoreceptors)
- Retinal tears (if some of the vitreoretinal adhesions do not break away cleanly as the rest of the vitreous is detaching-> tobacco dust/Shafer’s sign)
- Metamorphopsia
Which cells of the vitreous have the following functions?
- process antigens and recruit other cells and thereby further escalate an inflammatory response
- synthesize collagen
- synthesize hyaluronic acid
Hyalocytes: process antigens and recruit other cells and thereby further escalate an inflammatory response and hyaluronic acid
Fibroblasts: synthesize collagen
(CO) 1. Describe the location of the vitreous in the eye, including its boundaries.
Anterior: lens, posterior zonules & pars plicata of ciliary body
Lateral: pars plana of ciliary body & retina
Posterior: retina & optic nerve
(CO) 2. Describe the characteristics of the vitreous that account for its transparency
It is 98-99% water. Hyaluronic acid binds the water and helps maintain wide spacing between the collagen
fibrils. Mostly type 2 collagen in the form of delicate fibrils which form an organized network in the vitreous
(CO) 3. Describe the structure of the adult vitreous.
▪ Be sure to include its major contents including approximate % of water vs. solids it contains
▪ Describe its cortex & center, being sure to include:
– Location
– Components (contents) of each and how they differ from each other
– Which of them (cortex or center) forms the major part of the vitreous
– Where the cortex is thin or absent
▪ Describe the anterior & posterior hyaloid membranes and be sure to include:
– What they are made of? Are they a true membrane?
– Their location/position in the eye
▪ Be sure to include its major contents including approximate % of water vs. solids it contains
98-99% water & ~ 1-2% solids (hyaluronic acid, type 2 collagen, water-soluble proteins, electrolytes, sugars, ascorbic acid)
▪ Describe its cortex & center, being sure to include:
Peripheral part = vitreous cortex; more tightly packed with more collagen (absent over surface of optic disc; thin/absent over macula)
Central part = major volume (more water/hyaluronic acid)
▪ Describe the anterior & posterior hyaloid membranes and be sure to include:
-cover vitreous surface (not actual membranes; just collagen condensations at periphery of cortex)
Anterior: near posterior lens capsule, zonules, posterior chamber, ciliary body processes of pars plicata, anterior part of pars plana
Posterior: adjacent to retina; continuous except at optic disc (ring like attachment at margin of disc)
(CO) 4. Name /Describe the structures located at the vitreoretinal interface and explain how the vitreous cortex attaches to the retina’s ILM.
The vitreoretinal interface includes: internal limiting membrane (ILM) of retina, anchoring fibrils of vitreous cortex, vitreous cortex outer part (posterior hyaloid membrane).
The vitreous cortex is attached to the retina’s ILM via the vitreous’ anchoring fibrils.
(CO) 5. Name and describe the attachment sites of the vitreous cortex and which attachments are firmest, etc. Be sure to include:
▪ vitreous base (be sure to include its anterior–posterior extent and firmest attachment
site)
▪ Wieger’s ligament
▪ Margins of macula and optic disc
▪ Blood vessels
▪ any others discussed in class
see previous question
(CO) 6. What are the functions of the cells in the vitreous?
▪ Hyalocytes
▪ Fibroblasts
HYALOCYTES (small population cells in vitreous cortex near retina/CB)- most at vitreous base/least at equator
- type of monocytes
- synthesize GAGs, especially hyaluronic acid
- phagocytic (act like macrophages)
- process antigens like macrophages in immune response and may recruit other inflammatory cells
FIBROBLASTS- synthesize collagen
(CO) 7. Name and describe the following structures including their locations related to the vitreous: ▪ Patellar fossa ▪ Retrolental space of Berger ▪ Ligament of Wieger ▪ Cloquet's canal ▪ Area of Martegiani.
CLOQUET’S CANAL
- canal running through the center of the vitreous, from the lens to the optic disc
- represents the former location of the hyaloid artery system present during ocular development
- S-shaped course through vitreous
AREA OF MARTEGIANI
-anterior to optic disc Cloquet’s canal opens into a funnel-shaped region called the area of Martegiani; the walls of Cloquet’s canal are formed by condensation of primary vitreous & the tunica media of the hyaloid vessels that used to occupy this location during ocular development
(CO) 8. What structures form a barrier to help prevent proteins from entering the vitreous?
see previous question
(CO) 9. Describe age changes in the vitreous. Be sure to include:
▪ Changes in Wieger’s ligament with aging (weaker or stronger attachment to posterior lens capsule with aging?)
▪ Changes in % of liquid & gel vitreous from birth through advancing age
▪ What occurs during liquefaction (with lacunae formation, etc.) and be sure to be able to
discuss what the patient & doctor would see and why.
▪ Anatomically what is happening leading up to a PVD and then when the PVD occurs.
Be specific and complete.
− Be able to discuss & describe what the clinician and patient would see (and why).
Include Weiss’ ring and posterior hyaloid membrane
▪ What are some of the major complications that might occur with a PVD.
Wieger’s ligament makes weaker attachment to posterior lens capsule (hard to remove lens capsule)
The vitreous becomes more fluid with age
Young (80% gel, 20% liquid)
Age 65 (around 35% liquid, 90 over 50% liquid)
Liquefaction clinical signs:
- collagen bundles appear as white strands while the liquid vitreous lacks collagen and so appears black
- Cloquet’s canal is more mobile and therefore visible in the vitreous (see the S shape tube as pt. looks up then straight ahead)-> “ascension phenomenon”
PVD clinical signs: will be seen by the clinician as an “annular ring” floating in the vitreous just anterior to the retina or optic nerve called a Weiss’ ring (partial or complete grey-brownish ring commonly seen during fundus examination with BIO)
