Fluorescein angiography is a photographic means of imaging the retina. Prior to the introduction of the OCT (ocular coherence tomography), it was the primary method of imaging the eye for the diagnosis and documentation of its condition, evaluating response to therapy, and to discovering any changes in the eye which could not be perceived clinically. It continues to be an important means of studying the blood circulation within the eye. It is still a valuable diagnostic tool for a retinal specialist.
How is a Fluorescein Angiography Performed?
Fluorescein angiography is an office procedure which takes approximately 15 to 30 minutes. A fluorescein dye is injected into a vein in the arm, and as the dye circulates throughout the body, multiple photographs are taken of the back of the eye as the dye passes through both the arteries and veins within the retina. The camera used to take the photos is equipped with special filters which allow it to project a certain wavelength of light into the eye which activates the fluorescein dye, which is then photographed as it passes through the eye. As the photographs are taken, the camera also records the time taken for the dye to first enter the artery in the eye and the time to completely fill the vein.
What is Actually Recorded on the Photographs?
Documented on the photographs is the circulation of the dye as it passes first through the arteries, then the capillaries, and finally the veins. Delays in the normal circulation time indicate either arterial or venous occlusion. Fluorescein staining of the blood vessels occurs with inflammation and/or damage to the vessel wall, and if the damage is severe or the vessels are abnormal, dye will stain and/or leak out of the blood vessels and accumulate in the retina.
Also documented by these photos is the circulation of the vascular layer under the retina, any defects in the pigmented layer of the retina, and any abnormality which disturbs the normal fluorescein pattern of the retina.
Indications for Fluorescein Angiography
As discussed above, fluorescein angiography is used to document and diagnose eye disease, as well as monitor response to therapy. Ocular coherent tomography (OCT) is currently, being used more often to perform these functions; however, there are still a number of conditions and circumstances which still require the use of fluorescein angiography. These conditions include:
- Retinal arterial occlusive disease
- Retinal venous occlusive disease
- Vascular anomalies and other diseases
- Vasculitis and autoimmune conditions of the eye
- Macular degeneration
- Temporal Arteritis
- Hereditary conditions involving the retina
- Intraocular tumors
Are There Complications to Fluorescein Angiography?
The procedure is generally uncomplicated; however, on occasion there may be side effects. When starting the injection of the fluorescein dye, there may be difficulty entering a vein to inject the dye, in which case, multiple attempts will be made before a successful and clean entry is accomplished. If a good entry is not made, there may be bleeding around the injection site, or the dye may be injected outside the vein, which can cause significant discomfort depending upon the amount of dye that is misdirected.
As the dye circulates throughout the body, the most common side effect is a mild sensation of nausea, which quickly passes after a few deep breaths. Some people may develop hives and/or some tightness in breathing which are treated with Benadryl. If these side effects are known to occur, the Benadryl is given in advance.
On very rare occasions, there may be a much more severe reaction to the dye, an anaphylactic reaction, which can be life threatening. All practices should have an emergency tray to handle this situation as well as immediate access to a 911 facility.
There are two additional, but benign, side effects of which the patient should be aware. First, there is a discoloration of the skin as the dye passes through the body. It will take on a yellow/orange appearance which lasts a few hours. Secondly, as the dye is eliminated from the body through the kidneys, the urine will appear orange.