DIS - Diseases of the Vitreous Humour I - Week 8 Flashcards
Describe the vitreous humour (2).
A clear avascular and acellular gel
What is the typical volume of the vitreous humour and what percent of it is water?
~4mL
99% H2O
Describe the structure of the vitreous humour. What kind of strength is conferred with this structure?
Complex parallel structure of collagen fibres
Confers antero-posterior strength
What are collagen fibres in the vitreous humour separated by and what is the significance of this?
Fibres separated by hyaluronic acid pockets, which contain water
What is the main collagen matrix of the vitreous humour held in place by? What does this improve?
It is cross-linked by type 2 collagen
Improves lateral structure and strength
What does the collagen matric of the vitreous humour provide a frame for? What does this act as and what does it attract? What is the outcome (2)?
Provides a frame for hyaluronic acid coils to anchor to
Coils act as a spring
Coils attract and bind water
-results in the formation of a gel to cushion the eye
While the vitreous humour is relatively acellular, list 6 cells you could expect to find here.
Hyalocytes
RPE cells (fibroblasts)
Myo-fibroblasts
Astrocytes
Macrophages
White blood cells
What is the vitreous humour surrounded by (aside from the retina) and what is it exactly? What is this fused with?
By a hyaloid membrane
-condensation of collagen IV fibres
-fused with the retinal internal limiting membrane
Where are the strongest adhesions of the hyaloid membrane to the eye (4)? List in order starting with strongest.
Pars plana
ONH
Foveola
Retina (BV and other)
Where is the vitreous base and how long is it?
3 to 4mm zone straddling pars plana and ora serrata
List 6 functions of the vitreous humour.
Maintains eye shape and structural support
Sustains retinal apposition
Promotes optical clarity
Provides shock absorption
Prohibits migration of cells/blood
Inhibits neovascularisation
What compound of the vitreous humour inhibits neovascularisation?
Opticin
What is the tunica vasculosa lentis, what does it do, and when does it form?
A vascular sheath to the lens, supporting active lens growth
Forms 1 month in utero
Where can the hyaloid artery be found and within what structure?
In cloquet’s canal within the tunica vasculosa lentis
Describe how the tunica vasculosa lentis forms and degenerates and when.
As the hyaloid system atrophies near term, a secondary vitreous humour forms near the retina, surrounding and compressing the primary vitreous humour into the TVL, extending from the ONH to the lens
It degenerates with time by 1 month post-natal
What are congenital abnormalities of the vitreous humour mostly due to?
Partial decay or remnants of the tunica vasculosa lentis
List the three most commn tunica vasculosa lentis remnants and where they are found.
Mittendorf dot (lens)
Bergmeister’s papilla (ONH)
Perisistent primary hyperplasic vitreous humour
Describe perisistent primary hyperplasic vitreous humour and what it encroaches on.
Thickened due to compression by secondary vitreous humour formation
Encroaches on the lens
What is a mittendorf dot? Use the SOAP acronym.
Anterior remnant of the hyaloid artery
S - patients usually asymptomatic
O - opacity and condesation just below and nasal to the posterior pole
A - advise patient and build confidence
P - none required
What slit lamp technique is best for mittendorf dots?
Best seen with red reflex, direct view for location
What is bergmeister’s papilla? Use the SOAP acronym.
Posterior remnant of the hyaloid artery
S - asymptomatic
O - remnant of the hyaloid system
A - DFE, look for traction
P - advise patient
How does bergmeister’s papilla look compared with a persistent hyaloid artery?
BP - solid mass of whitish tissue or delicate glial strands stretching over the disc
PHA - glia emanating from ONH towards lens
What is persistent hyperplasic primary vitreous humour? Is it anterior or posterior? Is it serious or benign?
When the tunica vasculosa lentis persists and proliferates
Anterior (mostly) or posterior (rare)
-potentially very serious
What are the signs of anterior persistent hyperplasic primary vitreous humour (3)?
Visual obstruction (amblyopia and strabismus)
Leukocoria (white pupil)
Fibrovascular proliferation behind the lens
List three possible diseases secondary to anterior persistent hyperplasic primary vitreous humour.
Lens swelling/cataract
2° glaucoma
2° retinal detachment
What is posterior persistent hyperplasic primary vitreous humour often associated with (3)?
Retinopathy of prematurity
Signs of retinal detachment
Posterior uveitis/inflammation
List four objective signs of posterior persistent hyperplasic primary vitreous humour.
Fibrovascular proliferation on the disc/retina
Traction on the retina/ONH from shrinkage (twisted disc appearance)
Lens opacity
2° retinal detachment
List four differential diagnoses for persistent hyperplasic primary vitreous humour.
Retinoblastoma
Retinopathy of prematurity
Cataract
Glaucoma
What is the management for persistent hyperplasic primary vitreous humour (4)?
Refer to an ophthalmologist
Provision of aphakic Rx
Manage amblyopia/BV
Note milder cases in adults - monitor traction for RD
What is a vitreous cyst (2)?
Uncommon remnant of the hyaloid system or overgrowth of CB epithelium
List two signs of a vitreous cyst.
Persistent floater
Visual disturbance
How does a vitrous cyst appear?
Vague spherical mass in the vitreous humour
List three differential diagnoses for vitreous cyst.
PVD
Cells due to uveitis
Traction
What is the management for vitreous cyst (3)?
Monitor symptoms
-refer for vitrectomy or photocystotomy if problematic
What is syneresis?
Age-related liquefaction of the vitreous humour
Does syneresis occur sooner or later in myopes?
Sooner
Describe how syneresis occurs .
Involves the release of previously bound water which accumulates in lakes
This is accompanied by a collapse of the gel structure and condensation of collagen into clumps or threads
Lakes coalesce eventually
What gives most traction on the superior retina and where?
PVD at the blood vessels
What are lacunae?
Lkes of accumulated water with syneresis
What are three signs of syneresis?
Floaters from collagen condensations/water release
Posterior vitreous detachment
Traction/retinal detachment (flashes)
How does syneresis appear on slit lamp examination (2)?
Floaters appear as ghost veils
Liquefaction (things swimming around)
What is the best method to assess syneresis?
OCT for PVD
What is the management for syneresis?
Advise and monitor
What are vitreous floaters?
Any object in the vitreous humour seen by the patient
When are vitreous floaters often seen?
Lying back and looking up into the sky
What are operculum?
Floater due to retinal tissue
List 7 things that can be a floater.
Cells
Vitreous strands
Retinal tissue
Foreign bodies
Calcium phosphate
Cholesterol
Amyloid
What are four important signs/symptoms (history) that should be looked for if a patient presents with floaters?
Photopsia
Distortion
Trauma
GH issues
List four differential diagnoses for vitreous floaters.
PVD
Retinal detachment/tears
Haemorrhage asteroid hyalosis
Synchisis scintillans
Define posterior vitreous detachment.
Separation of the cortical vitreous from the ILM
Is posterior vitreous detachment more or less common in women vs men?
More common in women
Do lacunae form superiorly or inferiorly with syneresis and why is this so?
Usually superior due to gravity
What are two patient signs of posterior vitreous detachment?
A large central floater (ring shape)
Photospia
What are three things that may be found on a fundus exam for posterior vitreous detachment?
Peri-papillary large oval or partly oval floater - overlies disc
Hyaloid face well forward of the retina
Small pre-retinal or vitreal haemorrhage
-possible white retina due to traction
How should psoterior vitreous detachment be worked up during history and what three additional conditions should be considered?
Comprehensive history on recent floaters and photopsia
Consider GH (diabetes), eye trauma, and inflammatory conditions
What should you look ofr on a slit lamp exam of posterior vitreous detachment?
Vitreous face
What should you do in the absence of a floater in a case of suspected posterior vitreous detachment?
OCT
What four things can photopsia from posterior vitreous detachment indicate?
Retinal tear
RD from secondary retinal hole
Macular hole
Retinal or vitreous haemorrhage
What is the management for posterior vitreous detachment? Include review schedule.
Educate patient to return if worse
Follow up after 2/12
When should posterior vitreous detachment be referred (4)?
If it is recent and has resulted in
-visible retinal tears/tobacco dust
-persistent unexplained photopsia
-vitreous haemorrhage
Does photopsia with posterior vitreous detachment tend to subside over time or get worse?
Will eventually subside
What is asteroid hyalosis?
Lipids ebedded in a calcium phosphate matrix attached to the collagen framework
How does asteroid hyalosis appear?
Yellow/white specks that move with the framework but come back to the original position (sway)
True or false
Asteroid hyalosis is never found in eyes with posterior vitreous detachment
True
Is asteroid hyalosis common more in young or older patients?
Older
Is asteroid hyalosis typically uni- or bilateral? Are patients symptomatic?
Often unilateral and asymptomatic
List four conditions which have a suggested association with asteroid hyalosis.
Diabetes/glucose intolerance
Hypertnesion
Atherosclerosis
Hyperopia
Does asteroid hyalosis have any effect on vision?
Minor to none
What is the treatment for asteroid hyalosis?
None
What should be done if a patient have GH issues in addition to asteroid hyalosis?
Refer to GP for a workup
True or false
Synchisis scintillans is never found in eyes with posterior vitreous detachment
False
It is only found in eyes with posterior vitreous detachment
What is synchisis scintillans?
Cholesterol crystals that form in a liquid vitreous humour
When does synchisis scintillans appear in the vision and what happens after and why?
Appears with eye movement and sinks due to gravity
Is synchisis scintillans typically uni- or bilateral?
Bilateral
When does synchisis scintillans tend to occur?
In younger patients after PVD
What three conditions is synchisis scintillans associated with?
Advanced eye disease
Chronic vitreous haemorrhage
Trauma
What is the management for synchisis scintillans?
None, but monitor underlying eye condition and possible glaucoma
