Retina Imaging
There are many forms of imaging (pictures) that are used by retina specialists to diagnose and help with treatment decisions. Unlike CT scans and MRIs, these imaging tests do not usually require a separate visit. However, they extend your appointment time, and this is one reason why many visits to a retina specialist are relatively long. These tests range from simple color photographs to angiography that involves a small intravenous injection of fluorescent dye. No contrast dye or radiation is used for retina imaging.
Fundus Photography
These are simple color photographs of the retina often used to document problems and provide a baseline frame of reference for future visits. These photographs are also helpful in showing a patient the appearance of the retina and often aid in answering any patient questions. A retinal photographer or an office technician will take these photographs. Sometimes black-and-white (infrared and autofluorescence) photos may also be used.
Fluorescein Angiography
Fluorescein angiography is a type of imaging designed to show how blood flows through the vessels in your retina and is used to evaluate many different retinal disorders. It involves an injection of a yellow dye into the arm or hand that travels throughout the body. A special fluorescence filter is then used to take images of the dye in the retina.
Overall injections of fluorescein dye are very safe. However, it will turn your urine bright yellow and discolor your skin with a yellowish tint for up to 24 hours following the test. Some patients will experience mild itching of the skin following a fluorescein injection and can be treated with an antihistamine by mouth. Rarely, fluorescein angiography can lead to a serious allergic reaction that may require further treatment.
Widefield Angiogram
Iris Angiogram
Intraoperative Angiogram
Electroretinogram
Electroretinogram (ERG) is a test used in measuring the objective electrical activity of the retina. It allows your doctor to assess function, instead of the structure, as is the case with most other retinal tests.
ERG tests used to take hours. However, new, non-invasive ERG imaging is a painless, quick test that will aid in assessing underlying function and/or risk of progression of many retinal disorders and toxicities. This test was historically reserved for assessing hereditary and genetic retinal disorders but has since been demonstrated to help assess common disorders such as diabetic retinopathy and retinal detachment.
Optical Coherence Tomography
A major advance in retina imaging occurred with the development of optical coherence tomography (OCT). OCT uses a scanning laser light to capture cross-section images of the retina. It is performed in the office by a technician or retina photographer and is painless. This test is similar to photographs but gives more detailed information about the structure of the eye.
OCT is used to monitor the treatment results of patients undergoing any intravitreal injections for disease such as macular degeneration, diabetic retinopathy, or retinal vein occlusion. OCT is also often used as a screening tool in patients with decreased vision. There are no eye toxicities or side effects associated with this non-invasive image.
Indocyanine Green Angiography
Indocyanine green (ICG) is a test often performed at the same time as a fluorescein angiogram and allows your retina specialist to evaluate blood flow within the choroid, which is the blood vessel layer underneath the retina. ICG contains iodine in is avoided in patients who have an iodine or shellfish allergy. ICG has a very low rate of side effects and does not cause any skin color changes. No radiation is used for either fluorescein or ICG angiography.
Ultrasound
When the structures in front of the retina are opaque or blurred, it may be difficult for your doctor to see the retina. Therefore, an office ultrasound, usually called a B-scan, might be performed during your examination. This ultrasound is painless and involves placing a small ultrasound probe over your closed eye with some cool gel on the tip. This provides an image of the back part of your eye that includes the retina.