Module 26 Section 2

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Module 26: 

Fluorescein Angiography, Part 2

Section 2:

Descriptive Terminology

and Common Abnormalities

Descriptive Terminology

• Pseudo-fluorescence and auto-fluorescence

• Hyperfluorescence

  • transmission

  • leakage

  • pooling

  • staining

• Hypofluorescence

  • block fluorescence

  • non-perfusion

Some Common Abnormalities

• Age Related Macular Degeneration

• Diabetic Retinopathy

• Central Serous Choroidopathy

• Artery and Vein Occlusions

Descriptive terminology

Although angiographic interpretation is the doctor's job, knowing what is normal and what is abnormal in fluorescein angiography makes you a better photographer.  You should be familiar with the appearance of common pathological conditions in order to properly document the pathology.

Pseudo-fluorescence and auto-fluorescence

Pseudo-fluorescence and auto-fluorescence are pre-injection abnormalities seen when photographing the retina with the exciter and barrier filters in place before the injection begins.  Remember that a good set of FA filters should essentially filter out all light except for fluorescent light.  

Pseudo-fluorescence occurs with an aging filter set that is allowing non-fluorescent light to pass.  What you see on a pre-injection photo is retinal details that should not be seen until dye enters the eye.  Below: an example of pseudo-fluorescence.

Auto-fluorescence occurs when a highly reflective structure, such as optic nerve head drusen, is seen when photographed prior to the injection of fluorescein.  Auto-fluorescence is sometimes mentioned as a diagnostic sign of optic nerve head drusen, but some doctors think it is of little diagnostic usefulness.  If the drusen is reflective enough to demonstrate auto-fluorescence, then it is on the surface of the optic nerve head and it can easily be seen with an ophthalmoscope.  If the drusen is deeper in the optic nerve head, then it will not be reflective and it will not demonstrate auto-fluorescence.  

Below is a color photo of optic nerve head drusen and a digitally enhanced auto-fluorescence image of the same eye. 

Drusen buried deeper in the optic nerve head can be demonstrated by B-scan ultrasonography.  Drusen is also highly reflective to the ultrasound beam.  

When the B-scan gain is turned down, the bright reflection from the drusen is still visible.

Post-injection abnormalities in the angiogram present themselves as either areas of increased fluorescence (hyperfluorescence) or decreased fluorescence (hypofluorescence).

Hyperfluorescence

Hyperfluorescence can be caused by any one of four types of abnormalities, or the increase can be caused by a combination of any of the four types.

• Transmission:  This is an increase in fluorescence caused by a disruption in the continuity of the RPE layer.  We are getting a better view of the normal choroidal vessel leakage through a break in the retinal pigment layer.  A common example is caused by the de-pigmentation seen in some macular scars.

• Leakage:  Some disease processes cause leakage of serum (and dye) through the vessel walls into the retinal tissue.   Remember that fluorescein does not normally leak from retinal vessels. A common example is diabetic retinopathy as pictured below.  An angiographic hallmark of leakage is the increase in area of hyperfluorescence as the angiogram progresses.  Fluorescein can also leak from a choroidal vessel, through the RPE, into a subretinal space (e.g. a choroidal neovascular membrane)

• Pooling:  This is really one of the combination processes.  You can't really have pooling of the dye unless you have leakage of the dye from somewhere.  Pooling occurs when leaking dye collects in a sub-retinal space.  Examples of pooling would be seen with central serous choroidopathy and with late pooling in a pigment epithelial detachment, as pictured below.

• Staining:  Staining occurs when tissue absorbs fluorescein dye.  Staining of the sclera occurs normally from the dye that normally leaks from the choroidal vessels.  An example of abnormal staining occurs in the tissue of a malignant melanoma.

Hypofluorescence is caused by:

• Blocked fluorescence:  The most common example of blocked fluorescence is a retinal hemorrhage.  The blood is so dense that the dye circulation beneath cannot be see.

As is common with many angiograms, the angiogram below demonstrates several types of FA terminology. There is hypofluorescence from the blood blocking, hyperfluorecence from leaking vessels, and staining of the tissue around the optic nerve.

• Non-perfusion:  Blood vessels that are blocked decrease or eliminate the flow of dye through sections of the retina.  A retinal artery occlusion demonstrates non-perfusion of the arterial branches below the site of the occlusion.  Advanced stages of diabetic retinopathy show areas of ischema where the capillary bed has atrophied, as pictured below.

Some Common pathological conditions documented with fluorescein angiography:

For more information on posterior chamber abnormalities, see Module 24.

Age Related Macular Degeneration: 

AMD often involves a network of new blood vessels (CNV) coming from the choroid and breaking through the RPE under the retina.  It is important to document the early phase of the angiogram so that a CNV net can be demonstrated (first photo, below).  Late photos of at least 5 minutes are needed to demonstrate leakage (second photo, below).  

Diabetic Retinopathy:

Diabetic retinopathy is a disease of the blood vessels that commonly exhibits pathology beyond the limits of the posterior pole.  A diabetic survey is a systematic series of photos that covers the retina in a 45 to 60 degree arc around the macula. 

If using a narrower angle of view (e.g. Zeiss 30 degrees), relatively more photos will be needed to cover the area.  If using a wider angle of view (e.g. Topcon 50 degrees), relatively fewer photos will cover the same area.

If you don't do a survey, be sure to at least look around the area surrounding the posterior pole with the camera so that you can document abnormalties in any particular quadrant.

Whenever performing an angiogram, it is usually a good idea to document the appearance of the posterior pole in the study eye and the fellow eye.  It is particularly important with diabetic retinopathy because these are common locations of abnormalities.

Central Serous Choroidopathy:

CSC is seen most often in younger men (age 25 to 45) and is thought to be stress related.  If usually involves a finite area of leakage in or near the macula.  As with any macular problem, it is important to document the origin of the leakage in the early stages of the angiogram and the extent of the leakage in the late stages.  You may need to wait for 10 to 15 minute late photos to document a slow leaking CSC.

Artery and Vein Occlusions:

Artery and vein occlusions can occur within the optic nerve head (e.g. central retinal artery occlusion, CRAO), or in branch arteries and veins (e.g. branch vein occlusion, BVO).  The branch occlusions occur at vessel bifurcations and crossings.  Document the posterior pole, the point of the occlusion, and any areas of leakage or ischemia.

Below is pictured a BVO with an occlusion at an artery and vein crossing (arrow).  The late FA photo shows macular edema (arrow), which will be of interest to the ophthalmologist.

Below is pictured an artery occlusion.  In the color photo, the arrow points to the occlusion at the artery bifurcation and at a crossing with a vein.  The angiogram shows the area of non-perfusion downstream from the occlusion.

There are, of course, many more abnormalities that are studied with fluorescein angiography.  These common ones were given as examples of what you need to be on the lookout for if you are new to fluoresecein angiography.  Our job as angiographers is to make sure that we do a sufficient job of documenting the pathology.  It is a fascinating procedure that you can learn from, even after many years of performing fluorescein angiograms.