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Optical Coherence Tomography (OCT), is one of the newest types of testing done for the examination of the retina. This test uses a laser that is non-contact and non-invasive to the eye. OCT testing is done to obtain high resolution cross-sectional images of the retina and its components.
OCT is equivalent to an ultrasound image; however it is light waves rather than sound waves that are used. The OCT instrument uses light waves to measure the thickness of the retina, the light-sensitive inner lining of the back of the eye. This results in a much higher resolution image of the retina. OCT reveals to the retina specialist straight, instantaneous, cross-sectional images of retinal tissue layers. This provides a valuable addition to the diagnostic capabilities of a variety of eye diseases particularly those associated with the retina.
OCT has been shown to be clinically useful for imaging and directly visualizing selected macular diseases including macular holes, macular edema, and age-related macular degeneration.
Typically, OCT testing is performed when the retina specialist determines that treatment is indicated with intravitreal injectables such as a steroid
or anti-VEGF's for macular degeneration. In these cases, the OCT demonstrates retinal thickening from leakage of abnormal blood vessels in age-related macular degeneration patients or a generalized thickening from occlusive or inflammatory conditions.
OCT testing is usually performed before the treatment begins, and again when the patient returns for the follow-up exam. This gives the doctor a quantitative comparison which helps to determine if further treatment is needed. OCT testing usually continues at each follow-up eye examination until the eye has stabilized for a time.
This test is usually done by a certified ophthalmic photographer.
Once the patient is comfortably positioned at the machine, a series of scans can be acquired in just a minute or two.
The scans are analyzed and printed while the patient is still present. The analysis of a scan or scan group will determine if there is a need to repeat it. If a repeat scan is needed, it is done then until an acceptable level of accuracy is obtained. Rarely would the entire session take longer than five minutes. The results are printed and attached to the patient's chart for review by the retina specialist.
Written by:
Debbie Kogler, L.D.O. Magnifiers & More
John DuBois, C.R.A. Retina Associates of Cleveland
What is Fluorescein Angiography?
Intravenous Fluorescein Angiography (IVFA) is a diagnostic procedure that uses a special camera to take serial photographs of the retina. Either film or digital cameras may be used.
A special fluorescent dye is injected into a vein in the arm or hand. The dye travels through the blood stream and appears in the retina in about 20 seconds or less. Rapid sequence pictures are taken with a blue flash for about 2 minutes to study the circulation into the eye. After several minutes, photos are taken to document the tissues in the eye once the dye has cleared.
Fluorescein dye is not iodine, nor is it radio active or radio opaque. Fluorescein angiography uses regular photography, not x-rays.
Why is Fluorescein Angiography performed?
Fluorescein angiography is very useful to study circulation patterns, abnormal blood vessels, damage to blood vessels, fluid leakage in the retina and the integrity of the pigment layer of the retina.
Every eye is different. Angiography helps the doctor understand the dynamics of the disease in your individual case, diagnose problems and pinpoint areas for potential treatment.
What are the side effects of Fluorescein Angiography?
Your skin will be yellowish for several hours, and your urine will be bright green overnight. This is caused by the dye circulating through the body and being filtered out by the kidneys.
What are the risks of Fluorescein Angiography?
Nowadays, adverse reactions are rare. The most common, although still un-common, is to feel nauseated for about a minute. This rarely leads to vomiting.
True allergic reactions such as itching and hives are rarer still. These are usually treated with antihistamines. Severe, life threatening, anaphylactic reactions are possible, but are almost unheard of.
Aftercare Instructions for IVFA
There are essentially no restrictions. Eat and drink as you normally would.
Drinking extra fluids may clear the dye more rapidly from the body, but is un-necessary.
Angiography requires dilating the pupils, so your vision may be blurred for a couple of hours.
Dark glasses should be worn outdoors. Sunshine is very un-comfortable with dilated pupils.
If you are diabetic and test your urine, the dye may cause difficulties in interpreting some test results for 24 to 34 hours. If you have dialysis soon after angiography, the fluid will have a “fluorescein green” color.
Written by:
William C. Nyberg, CRA, RBP, FOPS
Director, Ophthalmic Photography
Scheie Eye Institute
University of Pennsylvania Health System
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