Retinal Ischemia

Question 1

What signs show ischemia

Answer 1

Microangiopathy, exudation and non perfusion

Question 2

What are the signs of ischemia?

Answer 2

Cotton wool spots, venous beading, looping, +RAPD, disc oedema, bad va, Irma

Question 3

What does pre-proliferation retinopathy consist of?

Answer 3

Ischemia but no neovasc

Question 4

What are signs of pre-proliferative retinopathy?

Answer 4

Cotton wool spots, microaneurysms, hard exudates and haemorrhages

Question 5

Explain the characteristics of Irma:

Answer 5

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

Question 6

Explain the characteristics of beading

Answer 6

Occurs when vein runs through an area of capillary closure and can see bulge like sacs in it

Question 7

Explain the characteristics of looping

Answer 7

Form of shunt vessel that provides alternative drainage after an occlusion due to thrombosis

Question 8

What is a shunt vessel?

Answer 8

Vessel that’s linking an artery to a vein that controls blood flow

Question 9

Explain what happens when you have ischemia in terms of VEGF?

Answer 9

It leads to a release of cytokine which is VEGF. Vegf activates receptors which then leads to proliferation of new vessels

Question 10

What does VEGF stimulate?

Answer 10

It stimulates angiogenesis and increased vasopermeability

Question 11

What does vasopermeability lead to?

Answer 11

Exudation (oedema and exudates)

Question 12

What does angiogenesis lead to?

Answer 12

Neovasc

Question 13

Which part of diabetic retinopathy includes neovasc

Answer 13

Proliferative diabetic retinopathy

Question 14

Explain how VEGF drives neovasc

Answer 14

It acts on VEGF receptors on the endo cells of the vessel wall. Activation results leads to the formation of new and leaky vessels.

Question 15

What’s the reason for neovasc to occur?

Answer 15

Misguided attempt at vascularising ischemic tissue

Question 16

Explain the steps of VEGF and neovasc formation

Answer 16

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

Question 17

Explain the characteristics of neovasc?

Answer 17

• 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

Question 18

What happens around the neovasc vessels

Answer 18

Fibrous tissue forms around the neovasc and acts as a scaffold for the new vessels

Question 19

What happens when the new vessels contract?

Answer 19

It leads to haemorrhaging in the vitreous and pre-retinal area

Question 20

When do pre-retinal and vitreous haemorrhages occur in the diabetic retinopathy process?

Answer 20

Proliferative retinopathy

Question 21

What is the referral for pre retinal and vitreous haemorrhages?

Answer 21

Urgent referral

Question 22

Explain the characteristics of pre-retinal haemorrhages:

Answer 22

• Bleed into the pre-retinal space
• well defined margins
• all underlying retina is obscured

Question 23

Explain the characteristics of a vitreous haemorrhages?

Answer 23

• 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

Question 24

Why is there blurry margins in vitreous haemorrhages?

Answer 24

• 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

Question 25

How does a vitreoretinal traction occur?

Answer 25

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

Question 26

How do we differentiate a rheg detachment and a tractional detachment?

Answer 26

Rheg has an rpe tear leading to rpe cells escaping into the vitreous causing tobacco dust

Question 27

What is the treatment for a tractional detachment?

Answer 27

Vitrectomy (removal of the vitreous)