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Examination & Diagnosis
A thorough examination by an eye doctor is the best way to determine if you have macular degeneration or if you are at risk for developing the condition.
The exam begins by testing your visual acuity or the sharpness of your vision. There are several different tests for visual acuity. The most familiar one has lines of black letters on a white chart.
Next, your eyes may be tested with an Amsler grid. This test helps your doctor determine if you are experiencing areas of distorted or reduced vision, both common symptoms of macular degeneration. If you do have macular degeneration, your doctor will use the Amsler grid to determine if your vision has changed. Your ophthalmologist may provide you with a small version of the Amsler grid such as the Yannuzzi card to carry with you in your purse or wallet.
After these visual tests, the front part of your eyes will be examined to determine if everything is healthy. Your doctor may put anesthetic drops in your eyes before measuring the pressure in each eye.
Then, drops are administered which cause your pupils to dilate. This will allow your doctor to examine the retina through the enlarged pupil. The drops typically take between 20 and 45 minutes to work, and will wear off in about 4 hours. While the pupils are dilated, it is usually difficult to read, and bright lights may be uncomfortable. Some patients use sunglasses after dilation to reduce light sensitivity.
After the dilating drops are administered and allowed time to work, the eye doctor will seat the patient at a device called a slit lamp. The slit lamp is a special microscope that enables the doctor to examine the different parts of the eye under magnification. When used with handheld lenses or special contact lenses, the slit lamp gives the examiner a highly magnified view of the retina.
The slit lamp is a microscope that gives the examiner a magnified view of the retina. Your doctor will look for drusen and other areas of the retina that appear suspicious or abnormal.
The examiner will look for drusen and other areas of the retina that might appear suspicious or abnormal. Since choroidal neovascularization (the new blood vessel growth found in the “wet” form of macular degeneration) occurs beneath the retina, the blood vessels themselves are not usually visible. But the examination can reveal clues such as: bleeding, elevation of the retina, or fluid behind the retina, that suggest the presence of choroidal neovascularization (CNV). In these cases, further testing may be necessary.
This retinal photograph shows many drusen and fluid under the retina, suggestive of choroidal neovascularization. Additional testing will be required for complete diagnosis and treatment. (Click image for full size image.)
Angiography
Angiography Video
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A technique called angiography is the most useful test for determining the presence of choroidal neovascularization (CNV). The procedure is painless and very safe. The patient will be seated at a fundus camera, which takes pictures of the retina. A small IV catheter is inserted into a large vein, usually in the arm. Several pictures are taken at this time.
The fundus camera takes pictures of the fundus, or retina. The camera may use film, or it may display the images on a computer screen.
A small IV catheter is inserted into a vein for the injection of fluorescein or ICG dye.
Then, a dye is injected into the vein. The dye circulates throughout the blood vessels of the body. As the dye enters the blood vessels of the eye, a series of photographs is taken of the retina. Special filters make the dye stand out against the background of the retina.
By looking at the pattern of the blood vessels and observing whether dye leaks from any of the vessels as time passes, your ophthalmologist can locate sites of choroidal neovascularization if they are present.
Two dyes are commonly used in ophthalmology: an orange dye called fluorescein and a green dye called indocyanine green. These dyes are different than those used for angiograms of the heart or brain. Unlike in angiography used in other parts of the body, X-rays are not used in this procedure since the examiner can look through the pupil and see the blood vessels directly.
This fluorescein angiogram shows choroidal neovascularization (CNV) in the macula. The bright area indicates dye leaking from the neovascular vessels.
The majority of treatable CNV can be seen with fluorescein dye. Fluorescein angiography is an extremely safe procedure, and it has been performed in millions of patients for over 25 years. The overwhelming majority of patients experience no symptoms when the dye is injected. A small minority may feel flushed or briefly nauseated. Rarely, someone has an allergy to fluorescein and may experience itching or other symptoms that require treatment.
Sometimes, an area of CNV is not clearly defined, or it may be obscured by overlying fluid or blood. In these cases, it is sometimes helpful to perform the angiography using a different dye called indocyanine green. As its name implies, this dye is bright green in color, and is useful for visualizing deeper blood vessels. Side effects from indocyanine green dye are rare, and similar to those from fluorescein. Indocyanine dye does contain a form of iodine, so patients allergic to iodine should tell their doctors.
This ICG angiogram shows a bright area of CNV in the macula. The CNV was not visible with fluorescein dye because of abnormal fluid beneath the retina. (Click image for full size image.)
Optical Coherence Tomography
An OCT device is used to map the anatomy of the retina.
Optical Coherence Tomography (OCT) is a new technique for imaging the retina. It is a non–invasive test which records the features of the retina and displays this information as cross-sectional views, or optical ‘slices.’ For this procedure, the patient is seated at the OCT device.
Laser light is used to map the anatomy of the retina, and the resulting computer images are saved for analysis. OCT evaluations are not a replacement for angiography, rather they are complementary techniques.
This is an OCT image of the macula of a normal, healthy eye. The depression in the center is the fovea. The colors in the OCT image represent the different layers of the retina. Note how smooth and even the layers are. (Click image for full size image.)
This is an OCT image of the macula in an eye with wet macular degeneration. The affected tissue layers beneath the retina are no longer smooth and flat. (Click image for full size image.)
Autofluorescence Imaging
Autofluorescence imaging of the retina is a new technique which involves capturing a response from molecules in the retinal pigment epithelium (RPE). There are two ways to capture these images. One uses a specialized scanning laser, and the other uses special filters attached to the fundus camera. Both types are noninvasive. The images show areas of stress and damage to the retina and can be used to monitor these changes over time.
This is an autofluorescence image of the retina in a normal, healthy eye. The macula is at the center.
This is an autofluorescence image of the retina in an eye with dry macular degeneration. The dark spot in the center shows a large area of atrophy in the macular region.
This is an autofluorescence image of the retina in an eye with wet macular degeneration. The image shows neovascularization underneath the macula.
Used with permision from the Macula Foundation, Inc.