Macular Degeneration (cont.)
Exams and Tests
Initial tests include measurement of the sharpness of vision, or visual acuity, and an examination of the retina. During the examination of the retina, the ophthalmologist looks for specific signs of macular degeneration.
- Multiple spots in the macular region known as drusen are the hallmark of the dry form of age-related macular degeneration. These spots are accumulations of fat and cellular debris under the pigmented outer layer of the retina. They appear as white to yellow dots that will merge together with time. The spots may occasionally cause mild to moderate loss of central vision. Certain types of Drusen are a well-known risk factor for progression to the wet form of macular degeneration.
- Another sign of age-related macular degeneration is degeneration of the pigmented layer itself. Degeneration appears as thinning and loss of the retina, the pigment layer, and the choroid, the intermediate layer of the eyeball. Loss of vision tends to be moderate. It causes blind spots (called scotomas). If degeneration of the pigment layer significantly affects the center of the macula, a person can lose visual acuity permanently.
- In eyes that become complicated by the wet form of age-related macular degeneration,
exudates (fluid), blood, scarring, and new blood vessel membranes below the retina might be seen. These abnormalities may progress rapidly over days to months. Eventually, they may result in profound irreversible central vision loss. Wet age-related macular degeneration reduces vision sharpness to 20/200 or worse within two years in 70% of affected eyes.
If signs of macular degeneration are found, an ophthalmologist may take detailed pictures of the retina for future comparison. Tests may also include:
- Fluorescein angiography (FA): A special, extremely safe dye called fluorescein is injected into the arm. Then, an ophthalmologist or professional ophthalmic technician or photographer photographs the retina as the dye passes through the retina. This test determines the location of blood vessel or vascular damage and whether or not laser treatment could be potentially beneficial.
Fluorescein angiography is essential to pinpoint the exact location of any planned laser treatment. Most importantly, this test determines whether or not there are leaking blood vessels (wet macular degeneration) which, if found, can be treated with lasers or injections.
- Indocyanine green angiography (ICG): This test uses a different intravenous dye coupled with infrared wavelength photography to view the retina. The test may help to identify signs and types of wet macular degeneration that cannot be seen with fluorescein angiography.
- Optical coherence tomography (OCT): This is a noninvasive examination technique that produces a cross-sectional image of the posterior retina in vivo. Although this method is now widely applied in the diagnosis of various macular disorders, its role in evaluation and follow-up of patients with age-related macular degeneration is only now becoming more well established. OCT is particularly useful in determining the specific layers of retinal involvement as well as the presence of macular inflammation or swelling.
- Microperimetry using the Rodenstock scanning laser ophthalmoscope: This is used to quantify macular sensitivity and fixation pattern.
Visual field testing or perimetry precisely tracks the location of lost or deficient retinal function. This important test requires reasonable patient cooperation and understanding. It is useful in a wide variety of conditions including glaucoma, macular degeneration, nerve problems, and other retinal problems.
John D. Sheppard, MD, MMSc
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