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Age-Related Macular Degeneration
AMD is one of the leading causes of adult visual loss in the developed world. AMD occurs in a non-neovascular, atrophic "dry" form or neovascular "wet" form. Patients with "dry AMD" have subretinal deposits (drusen), pigment changes, and some retinal atrophy, but their central vision is either preserved or deteriorates slowly.
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| Normal Macula | | Dry AMD:Drusen formation under the Macula | | Wet AMD:Macula with abnormal blood vessels | |
Development of AMD
Approximately 10% of patients with the "dry" form of AMD progress to the "wet" form, characterized by neovascularization, or overgrowth of new blood vessels under the retina. These vessels leak fluid that causes scar tissue to form, which in turn compromises vision, typically the central vision that is essential for reading and functioning. Patients who manifest the neovascular form of AMD represent the majority who develop legal blindness (defined as best corrected visual acuity of 20/200 or worse in the better-seeing eye). Loss of vision has a major impact on the quality of life and independence for those afflicted, causing both economic and personal hardship.
| | How Patients See with Wet-AMD | |  | |  | | | Photos Courtesy of NEI |
Dry AMD
In the dry type of macular degeneration, the deterioration of the retina is associated with the formation of small yellow deposits under the macula, known as drusen. This phenomena leads to a thinning and drying out of the macula, which causes the loss of visual function. The amount of central vision loss is directly related to the location and amount of retinal thinning caused by the drusen. Vision loss in the dry form of AMD is usually gradual. People who develop dry AMD must carefully monitor their central vision, since this form can change into the more damaging wet form of AMD.
Dry AMD symptoms:
- Development of drusen
- Slightly blurred vision
- Difficulty recognizing faces
- More light is needed for reading and other activities
Wet AMD
Wet AMD occurs when abnormal blood vessels begin to grow underneath the retina. These new blood vessels may leak fluid or blood, thereby blurring or distorting central vision. Vision loss from wet AMD may occur faster and be more noticeable than from dry AMD. The longer these abnormal vessels leak or grow, the more detail vision will be lost. The earlier wet AMD is diagnosed, the better the patients' chance of preserving some or much of their central vision.
Wet AMD Symptoms:
- Difficulty recognizing faces at distance
- Blurred spot or blind spot in center of vision
- Rapid loss of central vision
- Straight lines appear wavy
Monitoring Your Vision with the Amsler Grid
If you have been diagnosed with dry AMD, you should use a chart called the Amsler Grid every day to monitor your vision, as dry AMD can change into the more damaging wet form. This is a simple vision test in which you will look at a chart resembling graph paper:
Cover one eye and look directly at the point in the center of the grid, observing the pattern of vertical and horizontal lines in your peripheral vision. You will look for any visual abnormalities, such as areas of distortion, darkness or blurriness. If you detect any changes when looking at the gird, you should notify your ophthalmologist immediately.
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| OPKO currently enrolling Phase 3 trial with Bevasiranib in wet AMD. |
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