Module 25 Section 1 

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Section 2

Module 25:

Fluorescein Angiography, Part 1

Section 1:

Preparation

• Introduction

• Characteristics of fluorescein dye

• Adverse reactions

• Preparation for the fluorescein angiogram

   

  • dye preparation

  • patient preparation

  • the consent form

  • setting the camera up

Fluorescein angiography is a diagnostic test that provides visualization of the retinal blood circulation.  This test provides the ophthalmologist with information that can be obtained with no other testing modality.

Sodium fluorescein dye is injected into a vein in the arm or hand of the patient.  As the dye travels through the circulatory system of the body, a retina camera with special filters in place is used to photograph the transit of the dye through the retinal circulation.  The particular characteristics of the circulation in the various diseases of the retina provide diagnostic and treatment information.

The technique of retinal fluorescein angiography was developed by Drs. Harold Novotny and David Alvis in 1961.  The basic technique has remained unchanged, but improvements in photographic instrumentation have improved the quality of the imaging.

Sodium fluorescein was invented by Adolf Baeyer (the Bayer aspirin fellow) in 1871, and was first used as a textile dye.  It is commonly thought to be a vegetable dye, but is actually a mineral based synthetic dye distilled from coal tar.

When injected into into the bloodstream, the yellowish fluorescein solution binds with serum protein.  The fluorescein/serum solution is able to absorb blue light in the 465 to 490 nanometer range, and the electrons are elevated by the blue light to a higher energy state.  As the excited molecules return to the previous state, the yellow-green light known as fluorescence is given off.  It is this fluorescent light that we capture on film.  (We will use the term "film" generically to mean either conventional photographic emulsions or digital imaging).

Characteristics of fluorescein dye

Characteristics of fluorescein dye when injected into the bloodstream:

• Fluorescein diffuses (seeps) through the choroidal capillaries and the sclera.
• Fluorescein does not normally diffuse through the retinal pigment epithelium, the retinal blood vessels, or the larger choroidal vessels.  This is the basis for the diagnostic value of the test.
• Fluorescein diffuses through cellular spaces and stains skin and mucous membranes for up to 4 hours.  Patients should be advised of their possible yellowish or jaundiced appearance following the injection.  The intensity and duration can be reduced by drinking water.
• Fluorescein is eliminated from the body within 48 hours, mainly though the kidneys .  The patient should be advised of the bright orange/yellow color of the urine.  The fluorescein may alter the results of some blood tests if done within the 48 hour time period.

Adverse Reactions

Mild adverse reactions to fluorescein dye (<2%):

• Sneezing, itching, and hives usually occur within minutes of the injection.  Common treatment includes oral antihistamines such as diphenhydramine (Benadryl).
• Nausea and vomiting usually occurs within minutes of the injection.  Various pre-medications have been tried including Benadryl, phenergan, and reglan, without complete success.  Some think reducing the amount of fluorescein and/or the speed of the injection may reduce nausea. Early FA photos have usually been taken by time nausea begins.  If nausea occurs, pause the photos and have the patient take several deep breaths, away from the camera and with a trash can at hand in cause vomiting occurs.  Nausea usually passes within a few minutes
• Pain and swelling at the injection site due to extravasation of the dye:  In other words, the dye is injected under the skin or into the muscle tissue instead of into the vein.  The pain occurs immediately upon injection.  Treatment involves cold compresses to immediately reduce swelling, followed by warm compresses to aid circulation.

Moderate adverse reactions to fluorescein dye (<1%):

• Fainting. Any patient in danger of losing consciousness should immediately be helped to a prone position on the floor, head down, legs elevated.  Smelling salts may speed recovery.
• Plebitis.   Inflammation of the vein into which the dye was injected.  Usually resolves within a day without treatment.  Don't use this vein again for fluorescein injection.
• Seizure.  Put the patient on the floor with the head to the side and protect the patient from injury.  A folded cloth in the mouth may be helpful.  Keep the area dim and quiet until recovery, which is usually within minutes.

Major adverse reactions to fluorescein dye (<1/5000):

• This includes any potentially life-threatening situation such as bronchospasm, laryngeal edema, cardiac arrest, and anaphylactic shock.

  Although very rare with fluorescein angiography, shock and arrest must be prepared for with an up-to-date emergency kit, oxygen, and a treatment plan.  Under no circumstances should fluorescein angiography be performed without a physician within easy reach in the office or clinic.

The above list is not inclusive of every possible reaction to fluorescein angiography.  It is representative of my experience with over 10,000 fluorescein angiograms.  I have actually never had a patient experience a major adverse reaction to fluorescein angiography.  However, at least one source lists the incidence of major adverse reactions as 1 in 900.

Preparation for the fluorescein angiogram

Most, if not all of the preparation for the test should be done before the patient enters the camera room.  The idea is that you want to look organized and professional.  It looks bad to be working on a camera problem or to be running out of the room for supplies while the patient is sitting there with nothing better to do than watch your every move.  

Before beginning the setup for the FA, make sure your patient is well dilated.  If not, give him another set of drops so the drops can be working while you make preparations for the test.

Log the patient information using whatever system is setup.  Patient name, birth date (or ID number), and exam date are the bare minimum that should be recorded.  Film based systems usually use a written log book.  Digital systems use a computer based database.  The name of the doctor and the diagnosis are very useful pieces of information to have in a fluorescein database.  Be aware that most digital systems have separate patient information and patient photo databases.  Be sure to back up the data on the patient info database as well as the photo database.

Dye preparation

Injectable fluorescein dye comes in 5%(10cc) , 10% (5cc), and 25% (2cc or 3cc) solutions.  I prefer the 25% solution.  Less volume has to be injected into the vein, and the higher concentration produces a bigger bolus (concentrated mass) of dye infused blood moving toward the eye.  This larger bolus produces better photographic contrast  and detail in the initial phases of the angiogram.

The dye comes packaged in either glass ampules or in glass vials with a stopper top.  The glass ampule has a glass top that must be broken off to get to the dye.

Some like to inject air into the vial with the syringe before the dye is withdrawn.  The air is then already in the vial to replace the dye as it is being drawn out and no vacuum is created.

To eliminate air bubbles from the syringe, do the following: Once the dye is in the syringe, draw a little air into the syringe.  Point the syringe upward so that the air goes to the top of the syringe.  Tap the syringe with your fingernail so that the bubbles rise to meet the air at the top of the syringe.  Now push the plunger in so that all of the air is forced out of the top of the syringe (pointing upward).

Getting the air out is actually less messy if you have the cap on the syringe (unlike the picture).  Just push the the dye so that a little goes into the cap.  This capped needle will be removed when you hook up to the butterfly.

Draw up the dye only as needed.  It is not a good idea to leave dye drawn up into a syringe for longer than the day that it will be used.  No matter how good you think your sterile technique is, transferring the dye from vial to syringe runs a risk of introducing pathogens into the dye that may multiply over an extended period of time.  Always leave a capped needle on the syringe until immediately before use.  The needle that you draw up the dye with works fine for this purpose.

You will also need a butterfly needle, an alcohol swab, a band aide, and a tourniquet for your "injection kit". (The 20g needle in the picture is for drawing up the fluorescein from a vial.)

The butterfly needle (a.k.a. "winged infusion set") has little "wings" that give you good control when finding a vein.  The long tubing allows you to easily reposition the patient and the syringe prior to the injection.  I prefer a 21 gauge butterfly needle because if is thin enough for all but the tiniest veins, and it has a large enough lumen (inner diameter) for a rapid injection.  

Have your injection kit ready to go, with the loaded syringe, before the patient comes into the room.  It is a good idea to have it hidden in a drawer, ready to go.  Some patients get queasy if they see a needle and syringe when they walk into the room.  It is even worse for some if they see you preparing the syringe in front of them.

Set your camera up for color fundus photography before the patient comes into the room.  Make sure everything is functioning and then bring the patient into the room.

Patient Preparation

It is the doctor's responsibility to explain the procedure to the patient.  No matter what the doctor does or does not tell the patient, it is the photographer's responsibility to explain the procedure again.  For most patients, the information bears repeating.  The exception would be the patient who is already very familiar with the procedure.

Most experienced ophthalmic photographers have done this procedure so many times that they have a "canned" presentation that they give to the patient who is new to fluorescein angiography.  The presentation should include the following:

• The reason for the test:  "This is a test of the retinal circulation that will give the doctor more information about your eye problem.  This information is very useful and is not available from any other procedure."
• A brief description of the procedure:  "We will take some color photos of your retina and then inject a dye in your arm and photograph the circulation of the dye in your eye."
• Possible side effects:  "The dye will turn your skin yellowish and your urine orange for several hours after the test.  A small percentage of patients experience nausea.  If this happens to you,  let me know and we can stop the test for a few minutes.  The nausea usually passes quickly.  There is a small chance that you may have a mild to moderate allergic reaction to the procedure.  There is a very small chance that you may have a severe reaction to the dye. We are prepared to treat you if needed."
• How long the procedure will take and what will happen at the conclusion of the procedure:  "The test will take approximately 20 minutes and then the doctor will come in and review the photos with you and your wife."

The Consent Form

The patient should sign an informed consent form before the procedure begins.  The form should include the following:

• The name of the procedure
• The name of the doctor ordering the procedure
• A brief "patient friendly" explanation of the procedure
• A list of possible adverse reactions to the procedure
• A warning that pregnant women should not have the test
• The date
• The patient's signature
• A witness's signature

If the patient was already dilated before being asked to read and sign the consent form, you must read and/or explain the form to the patient.  Notice that the "presentation" given to the patient was very similar to what is in the consent form.  A good pre-fluorescein presentation would qualify as explaining the contents of the consent form.  

If the patient refuses to sign the consent form, do not perform the angiography.  If you cannot answer all of the patient's questions and concerns, have the patient consult with the doctor again before proceeding.

Color fundus photos are almost always taken along with every fluorescein angiogram to document what the retina looks like with normal illumination.  It is a good idea to take these photos before the FA is performed.  This allows the photographer to practice alignment and focusing on this particular patient, and it allows the patient to become acclimated to the photographic procedure at a lower flash intensity level.  

Setting the camera up for fluorescein angiography

Almost all retina cameras have fluorescein angiography capability.  For the photographer unfamiliar with a particular camera, it is just a matter of finding where the filters are and how they insert into the light path.  There are two filters for FAs, an exciter filter (blue) and a barrier filter (greenish).  

The exciter filter must be in the light path so that blue light is projected onto the retina to excite the fluorescein molecules.  

The barrier filter is used to filter the light that comes back from the retina to the film.  The emitted fluorescent light has a peak wavelength of 520 to 530 nanometers (green light).  The barrier filter is designed to filter out all light except for the fluorescent light.  Thus there should be no light reaching the film except the fluorescent light from the retinal circulation.  When you take a pre-injection photo with the filters in place, the frame should be black.  The only exceptions would be an old set of filters that are leaking light (pseudo-fluorescence), or auto-fluorescence, which occurs with highly reflective substances such as optic nerve head drusen.

Some cameras have both filters in the viewing light path.  In this case, nothing will be visible to the photographer until dye is actually transiting the retinal vessels.  The photographer must align and focus with white light before the filters are moved into place.  You usually do not have to change your focus from the fundus photography setting.  In many situations, the focus is the same when switching from one eye to the other.  This is something that can be pre-determined from your experience having just taken fundus photos on the patient.   During the course of the angiogram, the exciter filter can be moved quickly out of light path to check focus and alignment if necessary.  

The Zeiss FF3 and FF4 cameras have the barrier filter in the camera body and not in the viewing light path.  This does allow a dim, blue view of the retina that is useful for alignment, but it does not give the photographer the intense fluorescent image of the dye transit that is produced by viewing through the barrier filter.

Because the FAs filters drastically reduce the amount of light being reflected by the retina, the viewing illumination of the camera will need to be set much higher for the procedure.  The Topcon cameras have buttons that allow independent insertion of the exciter and barrier filters into the light path.  The illumination also has separate "normal" and "fluorescein" controls.  The normal control is set lower and the fluorecein control is usually set to maximum.  The camera defaults to the normal control when the fluorescein filter is not in place, and it automatically switches to the fluorescein illumination setting when the fluorescein filter is in the light path.  This allows you to switch the the exciter filter in and out for alignment and focusing purposes without dazzling the patient with a flood of bright light.

Below:  The FA filter control panel on the Topcon.

The flash intensity level must also be set higher in order to record a detailed image of the retinal circulation.  Below is pictured a Topcon flash setting panel.  Usually a setting of 150 or 200 is necessary for fluorescein angiography.

I find it easier to maintain focus and alignment on the 50 degree setting.

If your doctor likes to have red-free photos of the retina, it is usually most convenient to take them after the color fundus photos, and before the angiogram.  Red-free photos are black & white images taken with a green filter in place (not the barrier filter, but the green filter on the filter wheel).  The green filters out the red color of the the blood vessels and make them appear darker against the background.  It makes the vessels and some abnormalities, such as nevi, easier to see.  Typically, these photos require a low flash setting, similar to the setting used for fundus photos.

This is a red free photo of a macular hole.  Notice the small "tab" in the upper right corner of this Topcon photo.  The is an orientation aid.  If the tab is in the upper right corner, you know that the photo is not flipped over or inverted.