Competency 6.1.12 Flashcards
1
Q
Physiological Sites of Vitreous Attachment
A
- The vitreous is loosely attached to the inner limiting membrane of the retina
- Stronger sites of vitreo-retinal adhesion are at:
- Vitreous base (very strong)
- Optic disc margins (fairly strong)
- Perifoveal (fairly weak)
- Peripheral Blood vessels (usually weak)
2
Q
Pathological Sites of Vitreous Attachment
A
- Lattice degeneration
- Vitreomacular traction
- Retinal neovascular vessels e.g. in DR
- Snailtrack degeneration
3
Q
What is Lattice Degeneration?
A
- is a thinning of the retina that happens over time
- most with this condition never have any symptoms or a loss in vision
- prevalent in around 8% of the population however it is found in around 40% of those who have had a retinal detachment
4
Q
How does Lattice Degeneration Cause Retinal Detachment?
A
- Lattice degeneration causes a RD by premature PVD and tractional tears.
- The vitreous overlying an area of lattice degeneration are synchytic however the attachments either side of this area are stronger than usual.
- Tears may develop after a PVD in the area affected by lattice degeneration
- Atrophic holes may lead to RD
5
Q
What is Retinoschisis?
A
- degeneration of the peripheral retina which causes the retina to split into two different layers
- split often occurs at the level of the outer plexiform layer
- results in severing of neurons and therefore a complete loss of visual function in the affected area
- present in around 5% of the population and is more common in hypermetropic patients
6
Q
Retinoschisis Symptoms
A
It is often asymptomatic as it lack the vitreo-retinal traction required to cause flashes/floaters, even if the RS is located posterior to the equator the patient seldom notices a field defect.
7
Q
Retinoschisis Signs
A
- usually bilateral
- typically begins by involving the extreme infero-temporal peripheral fundus.
- appears as a smooth dome-shaped elevation of the retina
o elevation is smooth and relatively immobile compared to the opaque and corrigated appearance of a rhegmatogenous RD - The lesion may progress until it has involved the entire circumference of the peripheral retina
o The typical form usually stays out here
o The reticular type is more likely to spread posteriorly - The presence of a pigmented demarcating line is likely to indicate RD rather than retinoschisis
8
Q
What is a Posterior Vitreous Detachment?
A
- separation of the vitreous body from its sites of attachment posteriot to the vitreous base
- This occurs due to synchysis of the vitreous humour which forms small fluid filled cavities.
- PVD is a normal age related event and PVD prevalence increases with age.
- usually be a spontaneous event, it can be induced by the likes of surgery, trauma or uveitis
9
Q
Posterior Vitreous Detachment Prevalence
A
Only around 10% of those inder 50 years of age have had a PVD however this is around 66% of those over 70 years.
10
Q
How Often Does Posterior Vitreous Detachment lead to Retinal Detachment
A
Normally 10% of those with a symptomatic PVD will have suffered a retinal tear, however if there is a haemorrhage this rises to 60%.
11
Q
The Usual Sequence of Events of a PVD
A
- Perifoveal detachment
- Foveal separation
- Detachment from posterior retina as far as equator
- Initially disc attachment may remain
- Peripheral detachment as far as vitreous base (only attachment to remain)
12
Q
Posterior Vitreous Detachment Symptoms
A
- Flashes
o Described as lightning arc-esq
o Can be induced by eye or head movement
o Mostly seen in temporal periphery
o More noticeable in dim illumination - Floaters
o Mobile vitreous opacities
o Most evident against a bright pale background
o Can be Weiss ring/vitreous blood - Blurred vision
o Can be due to dispersed haemorrhage
o Can be due to floaters on visual axis
13
Q
Posterior Vitreous Detachment Signs
A
- Posterior hyaloid membrane can sometimes be seen on posterior examination
- Haemorrhage may be indicated by small red cells in the vitreous cavity
- Weiss ring
14
Q
What is a Retinal Break?
A
- often occurs due to vitro-retinal traction at sites of adhesion, whether than be physiological or pathological
- When there is a retinal break the vitreous fluid has access to the area behind the retina.
15
Q
Retinal Break Prevalence
A
Retinal breaks occur in around 20% of eyes with a symptomatic PVD and belived to be around 8% of eyes in the general population
16
Q
Retinal Break Timing
A
- Usually present sooner after symptoms of a PVD
- Tear formation can be delayed in rare cases
17
Q
Retinal Break Location
A
- Tears aossciated with a PVD usually located in upper retina
- More often temporal than nasal
- Macular breaks related to PVD are rare
18
Q
Retinal Break Morphology
A
- Retinal breaks may be flat or may have aossicated area of sub-retinal fluid
- If there is more than 1 disc diameter of fluid form the edge of the break then this is defined as a retinal detachment
19
Q
Types of Retinal Tears
A
- Horseshoe Tears
- Operculated Tears
- Retinal Holes
- Dialysis
- Giant Retinal Tear
20
Q
Features of Horseshoe Tears
A
o Consists of a flap
o Its apex is pulled anteriorly by the vitreous
o Base remains attached to retina
21
Q
Features of Retinal Holes
A
o Round/oval
o Usually smaller than tears
o Lower risk of RD
- If RD occurs then is usally:
slowly progressing
in a young female myope
o PVD not necessarily present
21
Q
Features of Operculated Tears
A
o The flap is completely torn away by the vitreous leaving a round/oval break
o The patch of torn away retina can be seen in the vitrous cavity
22
Q
Features of Dialysis Retinal Detachment
A
o Circumferencial tear along ora-serrata
o Usually due to trauma
o Vitreous remains attached at posterior part of break
o Appears as large RD
o Slowly progressive in absence of PVD
23
Q
Features of Giant Retinal Tear
A
o Involving 90 degrees or more of retinal circumference
o Vitreous remains attached to anterior part of break (unlike dialysis)
o Most often located at immediately posterior to ora-serrata but can be at equator
24
What is a Rhegmatogenous Retinal Detachment?
- often characterised by a retinal break often due to vitreo-retinal traction
- allows for liquified vitreous to travel under the retina which separates it from the RPE
- A RD will almost never occur in this manner if the vitreous is not liquified and there is no traction.
25
Rhegmatogenous Retinal Detachment Risk Factors
- Myopic eyes
- Vitreous degeneration
- PVD
- Lattice degeneration
- Snailtrack degeneration
- Vitreous loss during cataract surgery
26
Distribution of Breaks in Rhegmatogenous Retinal Detachment
- Where are Breaks located?
o 60% superotemporal
o 15% superonasal
o 15% inferotemporal
o 10% inferonasal
- Multiple Breaks?
o Half of eyes with retinal detachment have two holes
- Often within the same quadrant
27
Rhegmatogenous Retinal Detachment Symptoms
- Flashes and floaters (due to PVD)
o Location of photopsia is of no use in locating the primary break
- Curtain-esq peripheral VF defect appears
o Sometimes can resolve and not be present upon waking in the morning due to spontaneous absorption of SRF
o The quadrant of VF affected will often be the oppose quadrant of the primary break
o A lower VF defect if more often appreciated earlier by patient than a superior defect
- Loss of central vision
o Could indicate macular involvement
o Or obstruction of visual axis of large detachment
28
Rhegmatogenous Retinal Detachment Signs
- RAPD
o Present in eyes with extensive RD
- IOP
o Normally around 5mmHg lower than normal eye
o If extremely low then a choroidal detachment could be present
o Can be increased if there is Uveitis associated with trauma
- Iritis
o Usually mild
- Tobacco Dust
o Highly suggestive of retinal break
o Pigment cells located in anterior vitreous
- Blood cells or inflammatory cells are also highly specific
- Retinal Breaks
- Visible retinal detachment
29
Appearance of a Fresh Rhegmatogenous Retinal Detachment
- RD has a convex shape
- Slightly opaque
- corrugated appearance (due to retinal oedema)
- Loss of underlying choroidal pattern
- BVs appear darker than in flat retina
- SRF extends up until ora-serrata (unless caused by macular hole)
- Macular pseudohole
- Will be quite mobile
30
Appearance of a Longstanding Rhegmatogenous Retinal Detachment
- Retinal thinning
o Due to atrophy
- Intraretinal Cysts
o May develop if detachment has been present for about 1 year
- Subretinal Demarcation Lines
o Caused by proliferation of RPE cells at junction of flat and detached retina
o Takes around 3 months to develop
o Does not limit spread of SRF
31
What is a Tractional Retinal Detachment?
- Tractional RD is caused by contraction of fibrovascular membranes in areas of vitreo-retinal traction
- PVD in eyes with DR is often incomplete and more gradual which is thought to be due to leakage of plasma into vitreous gel
- If a break occurs in a tractional RD then it assumes the characteristics of a rhegmatogenous RD and progresses rapidly.
32
Tractional Retinal Detachment Causes
- Proliferative DR
- Retinopathy of prematurity
- Penetrating posterior segment trauma
33
Tractional Retinal Detachment Symptoms
- Flashes and floaters usually absent as not associated with an acute PVD
- VF defect
o Slowly developing over months of years
34
Tractional Retinal Detachment Signs
- RD has concave form
- Breaks usually absent
- Retinal mobility is severely reduced with no shifting fluid
- Less expansion of SRF
- Highest elevation occurs at site of traction
35
What is an Exudative Retinal Detachment?
- characterised by the accumulation of SRF in the absence of a retinal break or traction
- often due to fluid leaking out of vessels out of vessels and accumulating under the retina.
- If the RPE is able to cope and pump out the fluid into choroidal circulation then there is no RD
36
Exudative Retinal Detachment Causes
- Choroidal tumours
o Intraocular tumour should be considered the cause of exudative RD until proven otherwise.
- Inflammation (incl posterior scleritis)
- Bullous central serous chorioretinopathy
- Iatrogenic
- Choroidal Neovacularisation
37
Exudative Retinal Detachment Symptoms
- no flashes as no vitreoretinal detachment
- Floaters may be present only if there is associated vitritis
- VF defect may develop suddenly and progress rapidly
38
Exudative Retinal Detachment Symptoms
- Convex profile
- Surface is smooth and not corrugated
- Very mobile
- Shifting fluid detaches the area of retina where it is located
39
What is Pneumatic Retinopexy?
- Outpatient procedure
- a bubble of gas alongside laser/cryotherapy is used to seal a rhegmatogenous RD
- This procedure is usually reserved for the treatment of uncomplicated RD with a small retinal break in the peripheral retina.
40
Advantages and Disadvantages of Pneumatic Retinopexy
Advantages:
- Quick
- Minimally invasive
Disadvantages:
- Success rated lower than conventional scleral buckling
41
What is Scleral Buckling?
Is a surgical procedure where material sutured onto the sclera creates a buckle which aims to close retinal breaks by:
- placing the RPE next to the sensory retina
- Reduce dynamic vitreoretinal traction
42
Complications of Scleral Buckling
- Diplopia
o Due to mechanical effect of buckle
o Early spontaneous resolution is typical
- CMO
o Occurs in 25% but usually responds to treatment
o Can also be epiretinal membrane
- Anterior Segment Ischaemia
o Due to vascular compromise
- Infection
- Elevated IOP
43
Indications for a Vitrectomy
- When retinal breaks cannot be visualised due to e.g haemorrhage or debris etc
o Scleral buckling prognosis is poor if any breaks are missed
- When retinal breaks are unlikely to be closed by scleral buckle alone
o Giant tears
- Tractional RD
- Prevention of tractional retinal detachment
44
Goals of a Vitrectomy
- Separate the posterior hyaloid from retinal surface
- To remove the epiretinal tissue to release retinal traction
- Close retinal breaks if present
45
Vitrectomy Complications
- Intraoperatively
o retinal breaks
o choroidal haemorrhage
- Postoperatively
o Retinal breaks and rhegmatogenous RD
o Retinal fold
o Inflammation
o Raised IOP
o Cataract
