What is fluorescein angiography?

If you have a condition affecting the retina, your doctor may order a diagnostic imaging test called a fluorescein angiogram (FA). Fluorescein angiography uses a special camera to photograph the tissues that line the back of the eye, while dye flows through and illuminates the retinal blood vessels. This allows the doctor to get a better look at fine vasculature, retinal circulation, and other structures in the back of your eye. The dye will also highlight abnormal areas of leakage or swelling in the retina, helping to diagnose conditions like age-related macular degeneration, diabetic retinopathy, retinal vascular occlusions, ocular inflammatory disease, and more. FA’s may also be used to help guide the doctor during treatment. For example, if the patient requires laser treatment such as retinal photocoagulation or photodynamic therapy, the FA may be used to highlight the exact points of vascular leakage that must be targeted during the laser treatment. Additionally, fluorescein angiography also plays an important role in clinical research, helping to advance the understanding of retinal vascular diseases and new potential treatment avenues.

What exactly is fluorescein?

Fluorescein is an organic compound and dye used for diagnostic procedures, primarily in the field of ophthalmology. However, it has historically been used in the scientific field as a dye tracer to detect and examine the flow of water, detect leaks, use in industrial plumbing, and more. It has even been used during the annual St. Patrick’s Day tradition of dyeing the Chicago River green! For use in eye angiography, the active ingredient is fluorescein sodium. The normal adult dosage for an FA is 500mg, and is typically packaged in doses of 5 milliliters of 10% or 2 milliliters of 25%. In its concentrated form, fluorescein sodium appears orange-red in color. Fluorescein responds to light between the wavelengths of or 465-490 nanometers and fluoresces, or emits light, at wavelengths of 520-530 nanometers. After fluorescein dye is injected into the venous system and makes its way up to the eye, the fluorescein is excited with a blue light in the camera, and then emits light that appears yellow-green. The camera then processes the image to present the dye as white, or light colored areas, against a dark, monotone background, thus highlighting the retinal vasculature as well as abnormal leakage or accumulation of the dye as a result of an ocular disease.

How is a fluorescein angiogram performed?

Your doctor will order a FA if they require a closer examination of the retinal blood vessels, the optic nerve, and other structures in the back of the eye. After explaining the test and answering any questions the patient may have, the doctor will create an imaging order giving specific instructions to the ophthalmic photographer including which eye(s) to focus on, which angle of view to capture, as well as areas of interest. The photographer will have the patient sign a consent for permission to proceed with the test. The photographer will typically start with some initial photographs while getting the patient lined up and focused at the camera. Next, a trained staff member will start an IV line in preparation for the fluorescein injection. The doctor administers the fluorescein and the photographer begins a timer on the camera, so as to monitor the retinal circulation. The test begins and a rapid series of photographs are acquired, capturing the dye as it flows through the blood vessels while also highlighting any abnormalities that may be present in the back of the eye. This all happens quickly, taking place in about one to two minutes. The photographer will then take a series of “late” phase photographs, which are captured after the dye has circulated for a few minutes. This allows leakage and accumulation of dye to become more pronounced in the photographs. Finally, the photographer saves the photographs, creates any necessary analysis reports, and sends them to the doctor to review. This is the typical fluorescein angiography process at RAWNY, and may differ slightly at other institutions.

What are the side effects of a fluorescein angiogram?

Immediately after the procedure, patients often experience some blurriness and light sensitivity for a few minutes, as a result of the bright lights of the camera. Patients will experience a bright yellow discoloration in their urine until the dye makes its way out of the system; usually a day or two. Sometimes the skin can also appear slightly yellow due to the dye going everywhere, including the small capillaries under the skin. Since the eyes are usually dilated at the time of the FA, and it may take anywhere from 4 to 24 hours for the dilation to wear off and vision to return to normal. 

What are the risks of a fluorescein angiogram?

Historically, adverse reactions occur in a small percentage (5-10%) of patients and range from mild to severe. Nausea and vomiting from 30 seconds to 2 minutes after the administration of the dye are the most common reactions, and are usually brief in nature. Occasionally a patient may experience an allergic reaction resulting in itching or hives. This is usually treated with antihistamines at the time the symptoms appear. Vasovagal reactions can happen in some patients, usually due to anxiety about the procedure. Severe reactions including anaphylaxis and cardiac arrest have been documented, but are extremely rare. There is insufficient data regarding the use of fluorescein in pregnant women to confirm a drug-associated risk, however, generally speaking, caution is taken when considering FA in pregnant women.

Fluorescein Angiography at RAWNY

Fluorescein angiography is a common procedure used to diagnose and assess a variety of retinal disease processes that are managed by the vitreoretinal specialists at RAWNY. We are pleased to offer fluorescein angiography on a variety of cameras that offer both high magnification views and ultra-widefield views, depending on the condition being evaluated. Currently, RAWNY has a Zeiss Clarus, an Optos California, and a Heidelberg Spectralis, all of which produce spectacular angiographic results. RAWNY also participates in a number of clinical research trials that utilize FA data collection, which are performed by skilled, certified ophthalmic photographers. 

By Margaret Whelehan

Sources:

https://www.ncbi.nlm.nih.gov/ [Internet]. Fluorescein Angiography [Updated August 25, 2023. Cited: May 30th, 2024] Available from: https://www.ncbi.nlm.nih.gov/books/NBK576378/

Alcon Fluorescite package insert. Distributed by Alcon Laboratories, Inc. Fort Worth, Texas 76134 © 2006, 2016, 2020 Alcon Inc. 

Bennett CRA, OCT-A, FOPS, Timothy J. Fundamentals of Fluorescein Angiography. Retrieved May 29th, 2024 from https://www.opsweb.org/page/FA

Drugs.com [Internet]. Fluorescein Injection Prescribing Information [Updated: 30 October 2023. Cited: 29 May 2024]. Available from: https://www.drugs.com/pro/fluorescein-injection.html