Posterior Vitreous Detachment Flashcards
(30 cards)
Describe a PVD:
It’s a separation of vitreous from the sensory retina
Where does the PVD occur?
It occurs posterior to the vitreous base
What specifically detaches in a PVD?
The posterior hyaloid membrane detaches from the retina
What does the posterior hyaloid membrane line?
The surface of the retina from the vitreous base back to the optic nerve
In a PVD, which attachments are intact?
The attachment between the anterior hyaloid and the ora serata (vitreous base attachments)
What is the actual cause of PVD?
It’s caused by degeneration. Synchysis and synersis which cause tension on the weak attachments between the post vitreous and the retina. In the youth they’re strong but progressively weaken over time
What does weakening of the attachments cause (besides a PVD 😬)
It leads to vitreo retinal dehiscience which is a separation of vitreous from the retina which allows the vitreous to collapse in
What will happen if a hole develops in the cortex?
It allows the fluid (due to synchysis) to leak in the space between the inner limiting membrane and the posterior vitreous which is the retrovitreous space and this then causes an enlargement of the retrovitreous space and catalyses the detachment of vitreous from retina
Where do PVD’s start and what are they referred to as?
In the macula area and they are called partial detachments
Explain the development of a posterior vitreous detachment
1-in tact vitreous
2- small detachment temporal to the macula
3- detachment progressed and only fovea is attached
4-vitreous is close to complete detachment but an attachment in the middle of the fovea occurs
5- the fovea pit disappears as the vitreous pulls the fovea up
6-vitreous is fully detached from the macula but remains attached at the ONH
Where does the detachment occur?
Inward to the globe
In a PVD, which attachments survive the longest?
The attachments between the posterior vitreous and the optic nerve head
What indicates when a PVD is complete?
Detachment of the vitreous from the optic nerve head
For PVD, will all the attachments become ruptured?
No, the ones at the vitreous base will survive because they’re the strongest
What gives rise to a Weiss ring?
Detachment of the vitreous from the optic nerve head
Summarise the PVD process:
Youth= gel vitreous and vit/retinal adhesion – liquefaction without vitret dehiscience – anomalous PVD
Ageing= liquefaction and vitret dehiscience–complete PVD floaters
Explain anomalous PVD:
Degenerative changes occur without dehiscence (seperation of vitreous and retina). This then leads to residual adherence between the vitreous and retina. Making eye movements causes the adherences to come under strain due to increased mobility of the vitreous. These adherences will then detach.
What can anomalous PVD lead to?
Vitreoretinal traction which can lead to tears, holes and epiretinal membranes
Name risk factors of PVD:
Age. 8% 40-50 years
44% 60-70
86% 80-90.
No PVDs in younger than 40 patients
Myopia: 29% 40-50 and myopia increases the risk by 4-5x but also depends on the magnitude of myopia. More myopic= increased risk
Females: more at risk by 2-3x
Trauma: increases the risk. Cataract surgery especially. 58.6% got PVD within 1 year. They can develop immediately and there can be longer delays
Why does myopia increase the risk of PVD?
Because of myopic elongation and the attachments at more risk than normal patients
Explain the symptoms of PVD
It’s associated with flashing lights and floaters. Flashes are more noticeable in dim lights and in the temporal field and are thought to be caused by tugging on the sensory retina. Floaters are described as cobwebs or threads or flies and move with the eye and are more noticeable under bright and plain backgrounds. Weiss ring will show up as a large circular floater
Besides PVD and she related loss of vitreal transparency, what else causes floaters?
Vitreous haemorrhages or posterior uveitis.
Why are floaters an issue?
Because they’re a nuisance and reduce the impact on the quality of life
Why did floaters impact the quality of life for patients?
Because they cause a reduction in CS and images appear washed out
