Flashcards in Vitreous Deck (51):
What is the largest ocular organ?
What is the vitreous in contact with?
Ciliary body, lens, retina
The vitreous is ____% water. In regards to state, it is also ___% gel and ___% liquid.
80% gel and 20% liquid
What type of collagen forms the sieve of the vitreous?
What do Halocytes do?
Phagocytes - synthesis of collagen and glycoprotein
What do Fibrocytes do?
Together, Fibrocytes and glial cells form ___% of the cell population
What do VEGF molecules do?
Induce vasculogenesis (formation of new blood vessels)
The primary vitreous occurs in the first _______ weeks of gestation. ______ cells enter through fetal fissure and form hyaloid vessels. ______ released by lens induces vasculogenesis. _____ and _____ form collagen.
The primary vitreous occurs *3-4* weeks gestation. *Mesodermal* cells enter through fetal fissure and form hyaloid vessels. *VEGF* release by lens induces vasculogenesis. *fibroblasts* and *halocytes* form collagen.
The secondary vitreous occurs around the ______ week of gestation. ________ factor present. _____ vessels retract. Then the ______ is formed.
The secondary vitreous occurs around the *6th* week of gestation. *Anti-angiogenesis* factor present. *Hyaloid* vessels retract. Then the *Vitreous body* is formed.
What happens in the tertiary vitreous?
Formation of lens zonules
What are the four anatomical regions of the Vitreous?
3. Patellar Fossa
4. Canal of Cloquet
In the cortex of the vitreous, the average thickness is _______. There is no cortex over the ____ and it thins over the ______.
In the cortex of the vitreous, the average thickness is *200 micrometers*. There is no cortex over the *disc* and it thins over the *macula*.
The vitreous base is attached to the _______. It has a ______ broad annular region and is attached to the _______. While it has strong _______ fibers, it has weak _____ fibers.
The vitreous base is attached to the *pars plana*. It has a *1.5 mm* broad annular region and is attached to the *inner limiting membrane*. While it has strong *perpendicular* fibers, it has weak *radial* fibers.
The Patellar Fossa can be located at the _____ and is associated with the _______ and the ______.
The Patellar Fossa can be located at the *posterior surface of lens* and is associated with the *retrolental space of Berger* and the *Ligament of Wieger*.
What is the pneumonic to remember the vitreous attachments?
Big - Vitreous Base
Lions - Ligament of Wieger
Often - Optic Nerve
Pick - Peripheral Attachment
Fights - Fovea
Where is the ECM "glue" in the eye?
Between the internal limiting membrane and the posterior vitreous
What happens to the vitreous as you age? (in regards to liquidation)
At birth, the vitreous is completely gel. As we age, the vitreous slowly turns to liquid. At age 65, it is 60% liquid.
What is synchisis?
What is syneresis?
What is a Signet Ring Floater? (Weiss ring)
Detachment at the Optic Nerve. Creates a "floater" 20 degrees in the temporal visual field.
What happens in Posterior Vitreal Detachment (PVD)?
The cortical vitreous separates from the inner limiting layer of the retina due to the formation of "lakes" in the vitreous.
The sequence of events of PVD is:
2. Hole develops in the _______
3. Vitreal fluid passes into the _______
4. Detaches vitreous from the _____ of retina
5. Spreads to posterior border of ______
The sequence of events of PVD is:
2. Hole develops in the *posterior vitreal cortex*
3. Vitreal fluid passes into the *retrohyaloid space*
4. Detaches vitreous from the *ILM* of retina
5. Spreads to posterior border of *vitreous base*
What is characteristic of a Weiss Ring?
Ring shaped opacity
What is characteristic of condensation of collagen fibers?
What is characteristic of a vitreal hemorrhage?
Shower of minute red spots
What are the functions of the vitreous?
1. Support for the retina
Oxygen tension is lowest in the ____ of vitreous
In vitreous metabolism, diffusion has a _____ speed and moves in ______ directions
In vitreous metabolism, diffusion has a *slow* speed and moves in *all* directions
Substances in the _____ have trouble moving across vitreous, which prevents topically administered substances from reaching the ____. This prevents substances such as alcohol from reaching the _____
Substances in the *anterior chamber* have trouble moving across vitreous, which prevents topically administered substances from reaching the *retina*. This prevents substances such as alcohol from reaching the *vitreous center*
What is bulk flow?
Movement of water and solutes towards retina due to a pressure gradient from anterior part.
In a metabolic buffer, solutes move into the vitreous and become more _____. This creates a reservoir for _____ and metabolic metabolism
In a metabolic buffer, solutes move into the vitreous and become more *diluted*. This creates a reservoir for *ciliary body* and metabolic metabolism
how does the vitreous establish transparency?
An ordered GAG configuration and a low concentration of structural macromolecules and soluble proteins
How is the blood/vitreous barrier formed?
Tight junctions in ciliary epithelium, RPE, and endothelial blood vessels of the iris
What are the two classifications of retinal detachments? Which is more common?
1. Rhegmatogenous - most common
What are the two types of non-rhegmatogenous retinal detachment?
In rhegmatogenous retinal detachments, ___% of eyes have strong vitreal attachments, retinals tears from with ____, and there is a possibility of ____ _____.
In rhegmatogenous retinal detachments, *10%* of eyes have strong vitreal attachments, retinals tears from with *traction*, and there is a possibility of *vitreous hemorrhages*.
The vitreous transmit __% of light
What is the ligament of Wiger?
Site where the vitreous attaches to the lens
Why does the vitreous liquify with age?
An increase in randomness of arrangement of collagen fibers that leave spaces open to fill with fluid.
What is the cause of syneresis?
Eye growth as patients age
What are the two risk factors of syneresis?
1. Large myopia
2. Age (eye growth)
True/False. A 10D 10 year old myopic child is more at risk for syneresis than an emmetropic 60 year old patient.
What is the definition of a floater?
Moving vitreous opacities that are perceived when they cause a shadow on the retina
What are the two main structural supports of the lens?
2. Vitreous (cushion)
What is present in the vitreous that serves as an anti-oxidant reserve?
Which is more dangerous: tears or holes in the retina?
Which is more dangerous: holes in the superior retina or inferior retina? Why?
Superior retina because of gravity.
What percent of rhegmatogenous retinal detachments are bilateral?
Absence of the lens in the eye