Vitreous Flashcards
vitreous is ___ the eye’s volume and ___ the eye’s weight
2/3 volume of the eye
3/4 of eye weight
2 components of vitreous
water (99%) which is held in a gel-like state by hyaluronic acid and solids (1%) mainly collagenous filaments
what adds viscosity to vitreous and how does it change with age?
hyaluronic acid and we have a lot less hyalocytes as we age, so ability to hold water is reduced and vitreous becomes more fluid
vitreous viscosity is ___x viscosity of water
4x
what is the area of the strongest adhesion of vitreous to retina
vitreous base
describe the location and size of the vitreous base
- straddles ora serrata
- about 2-4mm wide
- can extend significantly posterior to ora
- usually more posterior to ora nasally
what is the vitreous base susceptible to and why?
- vitreous traction in this area can cause retinal tears or retinal dialysis (tear at ora)
- anterior limit of a PVD almost always posterior edge of vitreous base
what is a common location of tractional retinal tears (15% of them)?
posterior border of vitreous base
clinical appearance of vitreous base
- anterior border is grayish ridge on pars plana
- posterior border is hard to see but may have increased pigmentation under vitreous base if you can see it
5 areas of normal vitreo-retinal adherence
- vitreous base
- optic nerve head
- macular region
- retinal vasculature
- ILM
the 2nd strongest vitreo-retinal attachment, the ONH: has insertions where?
what does detachment cause?
- inserts into glial peripapillary ring
- detachment can disinherit this glial ring and cause Gartner’s/ Vogt’s/ Weiss ring
what type of vitreo-retinal attachment is at the macular region and how does it change with age?
- usually attached in circular ring around macular region
- this adhesion weakens with age
areas of abnormal vitreo-retinal adherence
- lattice degeneration
- chorioretinal scars
- retinal vasculature
- meridional folds
- granular tufts, tractional tufts
- unusual posterior extensions of vitreous base
the anomalous vitreo-retinal adhesions area almost always in the
equatorial region or further anteriorly
what would be the set up and technique used to evaluate the vitreous
- dark room (dark adapt) and dilated pupil
- optic section to “slice” vitreous, low mag
- angle beam at least 15-30
- use Tyndall effect (have pt shift fixation)
- observe subtle structures snd shadows directly or indirectly illuminated
symptoms of vitreous disease
- floaters
- flashes (photopsias)
- blurred vision
- metamorphopsia
what is the most common symptom of vitreous diease
floaters
sudden onset of floaters highly significant indicator for retinal tear or tear with detachment
what is muscae volitantes
a type of floater from remnants of hyaloid artery system trapped in Cloquet’s canal
what can cause white cells in vitreous
- uveal, vitreal, retinal, or optic nerve head inflammation
- iritis
what can cause pigment in vitreous?
- pathogomic of retinal tear (RPE released into vitreous called Tobacco dust or Shafer’s sign)
- uveitis
- intraocular surgery
- trauma
vitreal or pre-retinal blood strongly associated with:
retinal tear (91%) in patients without retinal vascular diseases such as diabetic retinopathy
if there is blood in the vitreous and the retina cannot be viewed, what can you do?
consider it a retinal tear until proven otherwise and a B scan may be needed to differentiate cause
what are some possible other symptoms of floaters
- asteroid hyalosis
- syneretic vitreous changes, fibrillary degeneration
- PVD
- tear film debris
- scotoma
flashes (photopsias) may signify
vitreo-retinal traction
which eyes are affected with flashes in vitreo-retinal causes vs. neurovascular
VR: unilateral
NV: bilateral
what types of flashes are seen in VR vs. NV
VR: color or black/white, bright sparks or lines, flash bulb like or lightening streak
NV: angular or zigzag patterned flashes (think chevron on side, consumed whole vision)
timing of flashes in VR vs. NV
VR: very brief (second or two)
NV: longer (minutes)
how can ambient lighting affect flashes in VR vs. NV
VR: more apparent in dark
NV: apparent in dark or light
if floaters can be elicited with eye/head movement it is more likely to be due to:
vitreal traction
what vitreal things can cause blurred vision?
- debris in vitreous such as Gartner’s ring (rapid transient blue to clear), vitreous heme, macular disruption
- chronic traction on macular region can cause CME