Introduction
The vitreous is a fibrillar meshwork of ECM, making up 80% of the eye. Composed primarily of collagen fibres and hyaluronic acid, but 98-99.7% is simply just water.
- It is encased by the vitreous cortex, which is composed of densely packed collagen fibres, which is then attached to the retina.
- It attaches in the eye to various points, including the vitreous base at the ora serrata, the fovea, the peripapillary and the posterior lens capsule.
- The strongest points of attachment include the vitreous base at the ora serrata and the peripapillary vitreoretinal adhesion point.
- The precorticaovitreous is the liquified lacuna (space) found anterior to the macular area.
Specifically, the vitreous space refers to the 3D space that extends 1.5mm anteriorly and 3mm posteriorly from the ora serrata, extending internally.
Dead Giveaways
Precortical Vitreous Lacuna
The precortical space forms throughout childhood, initially beginning narrow, but slowly enlargening overtime, forming the precortical lacuna by age 8
It is a hypo-reflective space relative to the vitreous just anterior to it, and the macula.
Typically described as a boat shape, with a septum dividing it from Cloquet's canal.
In 93% of people, that septum has a connecting canal
The * indicates the precortical lacuna, ** indicates the cloquet canal, and between them is both a septum and a hole (connecting canal) connecting the two zones.
Synchysis and Syneresis
Synchysis refers to the liquefaction of the vitreous. It has been shown that 20% of the vitreous is liquid by age 40, and over 50% by ages 80 and 90. Small pockets form within the vitreous, changing the gel-like vitreous into fluid vitreous, which enlarges and coalesces over time.
Syneresis on the other hand refers to the clumping and aggregation of the collagen, causing water to be moved out and leading to the process of synchysis.
Posterior Vitreal Detachment
Typically occurs between ages 45-65 years.
The second eye typically follows within 6 months to 2 years and is typically bilateral.
May occur more often in:
Myopes
Trauma/intraocular surgery
Inflammation
Hereditary vitreoretinopathies such as Wagner's disease, Stickler's disease and FEVR
has 4 main stages
Stage 1: Perifoveal separation with adhesion of vitreous to fovea:
There is still vitreomacular adhesion, but the surrounding pocket begins to detach
Blue arrow shows vitreomacular adhesion, and yellow indicates the pocket detachment.
Stage 2: Complete separation of vitreous from macula:
The vitreous is detached from the macula, along with the precortical pocket. The vitreous is still however connected to the optic nerve
Attachment to the optic nerve present. Yellow line shows the precortical lacuna which is now detached with the vitreous cortex.
Stage 3: Extensive vitreous separation with adhesion of vitreous to disc
The adhesion is still at the disc, but is more widespread temporally. The nasal portions of the vitreous are still relatively fine
Shows the adhesion still present nasally around the disc
Stage 4: Complete PVD
Is limited by the vitreous base
Is confirmed by OCT circular tomogram, showing no points of attachment
Is also indicated by the presence of a Weiss ring, which presents as a large moving floater.
Yellow line on the circular tomogram shows a fully detached vitreous from the peripapillary region. The Weiss ring can be seen just inferonasal to the disc, as a hypo-AF and blurry flaoter. 
Shows the Weiss ring in the vitreous
diagnostic features
Vitreous Fibres:
The normal vitreous contains numerous fibres, which not only gives the vitreous it's structure and shock absorbant features, but also causes these normal age related changes
The central vitreous contains collagen fibres running anteriorly to posteriorly. Most of the central vitreous is not densely packed with collagen
The anterior base contains collagen fibres inserting perpendicularly. This is the most dense area, and thus is the strongest and most unbreakable point.
As such, most PVDs typically stop regressing at this point
Only 15% of breaks occur here.
The collagen itself is around 100-300 microns thick, surrounding the central vitreous and is composed of layers of lamellae of collagen that runs tangentially to the cortex.
The direct connecting mechanism to the retina isn't well understood, but proposes a glue molecule which connects the ILM of the retina to the cortex.
PVD Symptoms:
The biggest symptom is the large floater (Weiss ring)
Patients can also experience flashes of light, with these flashes typically appearing temporally in one eye due to traction.