Flu Angiography #2: Abnormalities

Abnormalities can either involve hypofluorescence or hyperfluorescence. Defects are sub-classified according to

• type of defect (leakage, blockage etc)
• Location (retina, choroid, optic nerve)
• depth
• whether in inner retina (sharp focus) or outer retina/choroid (blurred cos you're looking through retina)

Also timing of defect. Autoflu before injection can occur if there are drusen. Drusen fluoresce a bit even without NaF. Sclera and gliomas can too. Then you have early arterial filling defects, later arterio-venous leaks and late phase abnormal staining and leaks (lack of staining indicates non-perfusion).

HYPOFLU - FILLING DEFECTS

• Indicate not enough circ. Occlusion or insufficiency of artery/vein
• @Retina - central or branch occlusion of art/vein OR hypoflu showing optic nerve atrophy
• @ON - normally there's a bright flush @ arterial phase and venous phase & late staining. In cases of ON atrophy you get hypoflu and only late staining present. This could happen in glaucoma
• Choroidal

HYPOFLU - BLOCKED TRANSMISSION

• Retinal vessels not visible eg pre-retinal haemorrhage - blockage in media or anterior retina
• Choroidal vessels not visible indicates deep retinal/subret haemorrhage

HYPERFLU - ABNORMAL VESSELS

• Dilated and or tortuous, wide & bright
• Neovascular vessels - wide, leaky, high density
• Tumour Vessels
• Aneurysms/leaks

HYPERFLU - LEAKS

• Microaneurysms - initially contained, then hazy leaks. EG Background DR
• Inflammation causing leakage like ischaemic optic neuropathy
• Choroidal Pooling - breaks in the RPE and NaF pooling in subret space eg central serous retinop.

HYPERFLU - PRE-INJECTION FLU

• Autoflu - drusen
• Pseudoflu - not really fluorescing, just bright reflective surfaces - hard exudates, coloboma

HYPERFLU - TRANSMITTED FLU

• lack of pigment, retinal atrophy
• choroidal background brighter 'window defect'
  

Flu Angiography #1

Assessment of retinal circulation is important in oc. disease. Loss of circ is the main cause of visual loss in the western world - diabetic retinopathy, ARMD etc. The flu angio reveals vascular dysfunction that you can't see and make the extent/severity more visible

NaF is non-toxic and maintains good flu. in biological tissues. 60% of it binds to protein in blood and 40% is in solution. The flu absorbs short wavel. light (blue) and emits longer (yellow/green)

Retinal flu

• Central Retinal Vessels - tight junctions in the epithelium, no NaF leaves the vessels normally
• Choriocapillaris - fenestrated epithelium. The NaF in solution passes straight out into the extracellular space and the NaF that's bound to the proteins will stay inside the capillaries
• Ciliary Body - Unbound NaF can leave vessels, join the aq. and colour the anterior chamber
• Optic Nerve - served by central retinal circulation (no leakage) but leakage in the choroid nearby will stain glial tissue and this is late staining which occurs after a few circulations of flu through the bloodstream
• Sclera - collagen is stained by flu from the choroid

Methods of Angiography

• Injection - IV, rapid concentrated inj. Arm --> Heart --> Lungs --> L Heart --> Arteries --> CRA (takes 7 secs to get there)
• Observation w/fundus camera fitted with cobalt blue filter
• Risks/side fx - staining of skin and urine, 5-10% of px nausea and vomiting, rarely serious allergic reaction

Normal Flu Angiogram

• Arterial Phase - 7-9 secs after injection. This is the arm --> retina circulation time. The stained blood appears to be flowing up the middle of the arteries ("lamellar flow"). The choroid fills in a patchy way giving background flu.
• Venous Phase - 10-12secs --> 15secs. Arteries contain NaF, the capillaries are filled and the veins also begin to flow. The flu flows along the sides of the veins. Bright background from the choroid, bright filled arteries, veins w/lamellar filling, maximal brightness @ 14-18secs
• Late Phase - diffuse NaF in the blood, veins and arteries equal in brightness, background will be diffusely stained, staining of the optic nerve and sclera. This is 4-5 minutes after injection.