What is Fluorescein Angiography?

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
  • Diabetes
  • 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.

What is an OCT?

Optical coherence tomography (OCT) is the most recent imaging innovation in ophthalmology used to study the structure of the eye.  Even more recent applications of this type of scan have been to study the anterior portion of the eye, but the primary usage has been for the evaluation of the retina, and more specifically the back of the eye.  This portion of the eye is called the posterior pole and includes the macula and the optic nerve.

There is a great similarity between ultra-sonography and optical coherence tomography, in that they both image by reflecting an impulse of energy onto the subject matter being studied and analyzing the energy reflected back.  The difference is that sonography uses sound waves, which can penetrate opaque matter, and OCT uses light waves, which only penetrate translucent matter.  Because light waves have a much shorter wave length than sound waves, there is much greater/better resolution in image presentation.

When to Use Optical Coherence Tomography

OCT is currently most often used to examine the macula in ARMD (age-related macular degeneration).  In this condition abnormalities in the retinal tissue can be identified and measured. These abnormalities include breaks in the outer retina tissues, accumulation of metabolic by-products, fluid under or in the retina, scar tissue under the retina or on the surface of the retina, and traction on the macula and/or surrounding retina.  Because of its high resolution the individuals layers of the retina can be identified, aiding in the diagnosis of the macular and retinal condition.

Other retinal diseases where an OCT is useful include;  macular holes and cases of macular pucker.

When used to evaluate the optic nerve, the OCT quantitates the amount of optic nerve damage, nerve swelling, and the degree of nerve fiber loss and location.  It can also reveal vitreous traction on the optic nerve.

An OCT is Non-Invasive and Does Not Hurt

The examination using the optical coherence tomographer is entirely benign, without any risk factors.  The patient is positioned in front of the OCT instrument and the head is placed in a frame for stabilization.  The instrument is then placed in front of the study eye, which is not touched,  and the patient is asked to look at a light target.  The Instrument, using a low intensity laser beam, scans the eye within seconds, and data is then printed out, including a cross-sectional view of the retina, a topographic view and the retinal thickness.

How often is an OCT Needed?

Besides aiding in the diagnosis of retinal and macular disease, the optical coherence tomographer is invaluable in evaluating the progression of a disease, as well as, showing if the condition is responding to treatment.  In some conditions, it may be used at each visit as continuation of treatment is based on the results of the study.  This is particularly true in the case of treating Age-related macular degeneration when an endpoint is determined when there is no longer any evidence of new vessel and all fluid has been reabsorbed.  The OCT has significantly decreased the need for fluorescein angiography, where an IV injection of fluorescein is required, followed by numerous photographs.  This procedure takes much more time and is more invasive.  It also has an additional risk, in that the patient may have an adverse effect to the fluorescein.

The use of the OCT has become a much more utilized imaging device in ophthalmology, but there continues to be a need for fluorescein angiography in certain cases where the cause of the macular damage is not revealed by the OCT. whois register . adobe creative cloud