Retinal Ischemia Flashcards
What signs show ischemia
Microangiopathy, exudation and non perfusion
What are the signs of ischemia?
Cotton wool spots, venous beading, looping, +RAPD, disc oedema, bad va, Irma
What does pre-proliferation retinopathy consist of?
Ischemia but no neovasc
What are signs of pre-proliferative retinopathy?
Cotton wool spots, microaneurysms, hard exudates and haemorrhages
Explain the characteristics of Irma:
av shunt vessels that allow passage of oxygenated blood to vessel without entering ischemic tissue
- different to normal vessels in every aspect
- sit within the retina
- found near cotton wool spots and areas of low perfusion
- alterations or pre-existing capillaries and don’t leak
- subtle appearance and can miss and can be confused with new vessels but management is the same
- fluorescein ang to differentiate
- associated with neovasc
Explain the characteristics of beading
Occurs when vein runs through an area of capillary closure and can see bulge like sacs in it
Explain the characteristics of looping
Form of shunt vessel that provides alternative drainage after an occlusion due to thrombosis
What is a shunt vessel?
Vessel that’s linking an artery to a vein that controls blood flow
Explain what happens when you have ischemia in terms of VEGF?
It leads to a release of cytokine which is VEGF. Vegf activates receptors which then leads to proliferation of new vessels
What does VEGF stimulate?
It stimulates angiogenesis and increased vasopermeability
What does vasopermeability lead to?
Exudation (oedema and exudates)
What does angiogenesis lead to?
Neovasc
Which part of diabetic retinopathy includes neovasc
Proliferative diabetic retinopathy
Explain how VEGF drives neovasc
It acts on VEGF receptors on the endo cells of the vessel wall. Activation results leads to the formation of new and leaky vessels.
What’s the reason for neovasc to occur?
Misguided attempt at vascularising ischemic tissue
Explain the steps of VEGF and neovasc formation
VEGF activating themselves to VEGF receptors on the endo cells leading to basement membrane degradation leading to endo cell proliferation and tube formation = new vessel formation and tube elongation which causes an increase of exudation
Explain the characteristics of neovasc?
- fine/thread like
- crisscross paths of vessel
- new vessels loop back to join the vessel from which they arose
- arise from venous side of circulation
- located anterior and on top of NFL and obscure all layers and vessels
- Arise from veins 3-4DD from disc margin and in any 4 quadrants
What happens around the neovasc vessels
Fibrous tissue forms around the neovasc and acts as a scaffold for the new vessels
What happens when the new vessels contract?
It leads to haemorrhaging in the vitreous and pre-retinal area
When do pre-retinal and vitreous haemorrhages occur in the diabetic retinopathy process?
Proliferative retinopathy
What is the referral for pre retinal and vitreous haemorrhages?
Urgent referral
Explain the characteristics of pre-retinal haemorrhages:
- Bleed into the pre-retinal space
- well defined margins
- all underlying retina is obscured
Explain the characteristics of a vitreous haemorrhages?
- bleed into the vitreous/hyaloid body
- blurry margins
- depending on the volume of blood and how much it’s diffused through the vitreous depends on how much is obscured
Why is there blurry margins in vitreous haemorrhages?
- due to blood diffusing into 3D space in the vitreous
- optical blur due to ophthalmoscope not being able to focus on 2 places at once
How does a vitreoretinal traction occur?
Fibrous material attached to ILM of the retina and vitreous and tension on new vessels in the fibrous membrane leads to tearing of the vessels and haemorrhaging and leads to the retina being elevated with blood and fluid. The elevation is a tractional detachment
How do we differentiate a rheg detachment and a tractional detachment?
Rheg has an rpe tear leading to rpe cells escaping into the vitreous causing tobacco dust
What is the treatment for a tractional detachment?
Vitrectomy (removal of the vitreous)
