Heimann / Foerster / Kellner Atlas of Fundus Angiography

1. Auflage 2006
ISBN: 978-3-13-257839-5
Verlag: Thieme
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 192 Seiten, ePub

Angiography of the ocular fundus is a standard examination method that should be mastered by every ophthalmologist treating posterior segment diseases.

Outstanding pictures - concise text

• Description of the most relevant disease entities seen in daily practice
• Double-page layout
• Excellent angiographic photo documentation
• Combined with significant comments on pathogenesis, indications for angiography, additional diagnostic examinations and decision making

Your advantages:

• The latest classifications of early and late AMD
• Learn standard angiographic methods
• Search for the most important angiographic patterns
• Interpret angiographies confidently
• Follow-up on recent AMD treatment regimens including intravitreal injections of VEGF-antagonists

Up-to-date application and further developments of standard techniques:

• Fluorescein angiography
• Indocyanine angiography
• Stereo-angiography

Use and limitations of evolving techniques:

• Fundus autofluorescence
• Infrared reflectance imaging
• Wide-angle imaging

Benefit from the experience of renowned lecturers in varying specialities!

Heimann, Kellner, Foerster

Zielgruppe

Ärzte

Autoren/Hrsg.

Heimann, Heinrich

Foerster, Michael H.

Kellner, Ulrich

Fachgebiete

• Medizin | Veterinärmedizin Medizin | Public Health | Pharmazie | Zahnmedizin Klinische und Innere Medizin Augenheilkunde, Optometrie
• Medizin | Veterinärmedizin Medizin | Public Health | Pharmazie | Zahnmedizin Klinische und Innere Medizin Kardiologie, Angiologie, Phlebologie
• Medizin | Veterinärmedizin Medizin | Public Health | Pharmazie | Zahnmedizin Medizinische Fachgebiete Bildgebende Verfahren, Nuklearmedizin, Strahlentherapie Radiologie, Bildgebende Verfahren

Inhaltsverzeichnis

1 Examination Methods
2 Adverse Effects of Fluorescein and Indocyanine Green Angiography
3 Age-Related Macular Degeneration and Chorioidal Neovascularization of Other Etiologies
4 Hereditary and Toxic Retinal Diseases
5 Tumors
6 Diabetic Retinopathy
7 Other Retinal Vascular Diseases
8 Diseases of the Macula and Central Retina
9 Inflammatory and Autoimmune Disorders
10 Disorders of the Optic Nerve Head

Leseproben

1.1 Fluorescein Angiography

Fluorescence and Fluorescein Angiography

The term “fluorescence” refers to solid, liquid, or gaseous matter that emits absorbed radiated energy in the form of electromagnetic radiation at similar or longer wavelengths.

In fluorescence angiography, a fluorescent substance is administered intravenously; shortly afterwards, it spreads through the choroid via the bloodstream and retinal vessels. Stimulating light enters the eye through a filter and then, as a result of the substance's fluorescence, produces light emission at varying wavelengths, which are reduced to appropriately defined emission spectra through a second filter; these can then be photographed and/or filmed.

Two different intravenous fluorescent substances are currently in use in ophthalmology: fluorescein and indocyanine green. The two substances differ in their absorption and emission spectra, in their pharmacological characteristics (particularly their binding properties to plasma proteins) and in their elimination and passage through vascular walls in the choroid and retina.

The development of the methodology and the clinical applications of fluorescein angiography are based on the work of Chao and Flocks, Novotny and Alvis, and MacLean and Maumenee. These angiographic methods have been in regular use for retinal diagnosis since the 1960s. In Germany, fluorescein angiography was first introduced, developed, and popularized by Wessing.

Sodium Fluorescein

Sodium fluorescein (C20H10O5Na2, MG 376) is the dye most commonly used for fluorescence angiography throughout the world. After agitation, the fluorescence lasts for 10-9 seconds (there is therefore no “afterglow” as in phosphorescent substances).

Both the absorption and emission spectra of sodium fluorescein depend on various factors; with intravenous administration, they are 465 nm (absorption) and 525 nm (emission).

Approximately 70–80% of the sodium fluorescein binds to plasma proteins; 20–30% does not bind. Injected fluorescein is diluted in the bloodstream by a factor of approximately 600 and disperses throughout the whole body. With the exception of the central nervous system vessels, the retina, and to a limited extent the iris, unbound sodium fluorescein can freely permeate all blood vessels in the body. A few minutes after injection, the skin, mucosa (visible up to 6 h after injection), and urine (visible up to 36 h after injection, or longer if kidney function is limited) show signs of the yellow dye. Some laboratory values can be affected until the dye is completely eliminated from the body. The elimination of sodium fluorescein predominantly takes place through the kidney rather than the liver.

Contraindications:

– Known hypersensitivity to fluorescein derivatives. Some companies specify that beta-blocker treatment is a contraindication. Beta-blockers do not interact with fluorescein directly, but allergic reactions are more difficult to treat.

– There are no medically established contraindications in pregnancy. Despite this, the examination is carried out in pregnant women only in exceptional circumstances.

– Sodium fluorescein has some limited vasoconstrictive and photosensitizing characteristics (skin irritation by sunlight after injection); however, these are not considered to be serious or significant.

Prerequisites for Fluorescein Angiography

Despite evidence of very good general tolerance of injected sodium fluorescein, the physician administering or supervising the treatment should be adequately trained in emergency procedures. Medication required during an emergency must be administered reliably and without delay. Immediate notification of the need for emergency care and implementation of it must be ensured (see Chapter 2).

Secure intravenous access is important; if extravascular or intra-arterial injection take place, severe side effects such as skin necrosis or intense yellow discoloring of the surrounding skin can be expected. Intravenous access should be maintained until the examination has been completed.

The following equipment is essential: a fundus camera with automatic film transport, or a digital camera; an electronic flash unit with an exciter filter of 465– 490 nm (the blue–green spectrum); and a recording filter of 520–530 nm (the green–yellow spectrum). Enlargement and editing of images for retinal analysis can be carried out (depending on the type of fundus camera used) using the various sizes of field available. A standard exposure setting of 30° for macular diseases is routinely used; in addition, 20° (the largest enlargement possible with a small section) and 50° or 60° exposures are also used.

Photographic documentation of the filtered, emitted light is recorded on highly sensitive black-and-white film, or in electronic image files with a digital camera system. Newer scanning laser ophthalmoscopes (SLOs) are also usually equipped to handle fluorescein angiography. Digital documentation systems have been increasingly used in practice in recent years. These have the advantages of allowing immediate assessment and editing of the images (with adjustment of contrast and brilliance) and also of providing electronic archiving and data storage, enabling fast computer-networked access to the data from several locations.

At present, however, film documentation still provides higher resolution. In private practices and most clinical centres, digital technology has established itself as the main examination method.

Experience and knowledge on the part of the photographer, along with cooperation by the patient, determine the quality of the images taken for analysis. Other factors that can have a negative effect on the quality of an angiogram are: clouding of the media; insufficient pupil dilation; too slow or insufficient injection of dye; and unreliable or badly configured equipment or faulty processing of the angiograms.

Practical Procedure

Before angiography is started, it is recommended to take a color exposure and a blank black-and-white exposure of the fundus. There should always be clarity about the structures to be examined, any potentially important phase of the angiography to be observed, and the enlargement chosen. Photographic documentation of the findings in the second eye should also be obtained in order to allow comparisons with the eye being treated and for monitoring.

Angiography starts with an intravenous bolus administration of 5 ml 10% sodium fluorescein solution (equivalent to 500 mg active agent; today's commercially available compounds usually come in ready-made solution vials). For patients with renal insufficiency, a reduced dose of 2.5 ml of the appropriate solution is recommended. A stopwatch should be used during the injection in order to plot the chronology of the exposures.

Inflow of dye into the choroidal vessels can usually be seen after 10–15 s; this is directly followed by the retinal circulation. Experienced photographers can “anticipate” the inflow of the dye and immediately start taking sequential exposures. The fast arterial and arteriovenous phase of the angiography which then follows places very high demands on the photographer, who has to take sequential exposures (starting with approximately one image per second) within a very short period of time, continuing until the maximum fluorescence is reached (this is usually 25–35 s after the start of the angiography). Angiography is concluded with the last exposures being taken 5, 10, or 15 min after the initial injection. The protocols used at different institutions vary depending on the profile of the disease and the institution carrying out the angiography.

After completion of the arteriovenous phase, additional exposures of the fundus periphery (for example, in diabetic retinopathy) or the second eye (for example, in macular degeneration) should be made in accordance with the diagnosed profile of the disease. Parallel complete angiography of both eyes is not possible with standard equipment.

After completion of the angiography, six to eight typical exposures (determined by the analysis technique used) of the individual phases of the angiography should be selected and enlarged—or, where applicable (digital angiography), digitally processed and saved for documentation purposes—and printed out. Storage of all unenlarged negatives—in other words, complete picture data—is recommended in all cases.

In situations in which the resulting images are inadequate for interpretation, the angiography can be repeated in most diseases after 2 h, at which time no fluorescence phenomena can usually be detected in the choroid vessels or in the retina. However, in larger studies, a 48-h interval is generally recommended.

Using the appropriate equipment, fluorescein angiography and indocyanine green angiography can be carried out, either in parallel or shortly after each other. Mutual interference between the fluorescence phenomena displayed does not occur, although some investigators have reported an increase in side effects during simultaneous angiography.

Interpretation

The interpretation of fluorescein angiography is a subjective method that is influenced by the timing of individual exposures, their quality, the actual exposures chosen for analysis, the way in which the picture is viewed, and finally the experience and qualification of the investigator. Interobserver and intraobserver differences in the interpretation of fluorescein angiography can occur.

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Über Autor(innen)

Heimann, Kellner, Foerster