Virteous Humour detachment

Question 1

Vitreous humour anatomy: Appearance and consistency

Answer 1

Transparent gel which fills the posterior segment of the globe.–> Water 99% to weight and a network of collagen fibres is responsible for its gel-like character.

Question 2

Vitreous humour anatomy: In contact with

Answer 2

Encircled by the hyaloid membrane–>in contact with:

1. posterior lens capsule
2. zonules
3. pars plana epithelium
4. retina ( adhesion between posterior hyaloid membrane and retina is loose, bond stronger @ larger retinal blood vessels.)
5. optic disc.

Question 3

VITREOUS DEGENERATION

Answer 3

All adults:
gradual degenerative liquefaction of the vitreous occurs.
–> Small liquid filled spaces develop in the central gel
–> These gradually coalesce to form larger liquid filled spaces which eventually involve large parts of the central gel.

Question 4

POSTERIOR VITREOUS DETACHMENT (PVD): Pathophysiology

Answer 4

Breaks develop in posterior hyaloid membrane

• -> communication between the lacunae of liquefied vitreous and potential space between the retina and the posterior hyaloid membrane
• -> Dissection of fluid into this potential space separates the posterior hyaloid membrane from the retina.

Question 5

POSTERIOR VITREOUS DETACHMENT (PVD): Epidemiology

Answer 5

Most people over 65 years of age have posterior vitreous detachments.

Question 6

POSTERIOR VITREOUS DETACHMENT (PVD): Causes

Answer 6

1. myopes
2. diabetics
3. after vitreous inflammation or haemorrhage.

Question 7

POSTERIOR VITREOUS DETACHMENT (PVD): Progression

Answer 7

Gradually/relatively rapidly and is known as posterior vitreous detachment.

Question 8

POSTERIOR VITREOUS DETACHMENT (PVD): Clinical picture

Answer 8

1. Floaters: local thickenings in the degenerative gel. (floaters > during posterior vitreous detachment)
2. Flashes of light lasting fraction of second but episodes last several minutes (days-weeks) and disappear when detachment complete: traction on retina in areas of tighter adhesion between the posterior hyaloid membrane and the retina–> traction mechanically stimulates the photoreceptors

Question 9

POSTERIOR VITREOUS DETACHMENT (PVD): Treatment

Answer 9

Flashes of light.

1. referred to an ophthalmologist within 24 hours for a thorough, dilated examination of the retina and vitreous.
2. Early detection and treatment of a retinal break will prevent subsequent retinal detachment.

shadow or curtain
sudden painless loss of vision
comfortable white eye
–> retinal detachment must be excluded.

Retinal break without detachment: Not all Rx
1. laser
2.cryotherapy.
inflammatory reaction initiated in area of the break to cause adhesion between the neuroretina and the retinal pigment epithelium.

Retinal detachment:
partial detachment –> threatens macula is indication for urgent surgery.
Detachment surgery must address each of the three causative factors:
1. The neuroretinal break: closed by reapplying the edges of the break to the RPE.
Done by appropriately positioned injected gas bubble
Externally by indenting the outer layers of the eye with explants.
2. Vitreous traction relieved: vitrectomy or explants.
3. Subretinal fluid drained.