Macular Degeneration Diagnosis
Macular Degeneration
Signs and Symptoms
During the early stages of age-related macular degeneration (AMD), particularly if only one eye is affected, you may not have symptoms. AMD also causes no pain that might suggest that something is wrong.
An eye doctor may be able to detect early signs of the disease before symptoms appear. Therefore, it is very important to have regular eye examinations to detect these signs as soon as possible.
Early Signs of Age-Related Macular Degeneration
At first, the dry type of macular degeneration often causes slightly blurred central vision, both close up and far. The center of vision may become fuzzy or shadowed, and this area grows larger as the disease progresses. Blind spots may develop, and people normally have more difficulty seeing color and fine detail.
In addition to the above signs, in wet macular degeneration, straight lines may appear wavy. Also, in this more severe form, central vision loss can occur rapidly, sometimes within days or weeks.
AMD can cause a variety of symptoms that can affect your daily life:
Symptoms of Age-Related Macular Degeneration
- Visual field defect
- Contrast sensitivity
- Poor tolerance for changing light levels
- Need for higher light levels
- Impaired depth perception
Visual field defect
The wide angle of vision that a healthy eye can see is called the "visual field." As AMD progresses, the center of a person's visual field may become smudged, distorted or lost. This defect causes problems with reading, driving, watching TV and recognizing faces.
Contrast sensitivity
It becomes more difficult to see textures and subtle changes in the environment. If you become unable to see slight contrasts and textures in pavements or stairs, it can be dangerous and lead to an increased risk of falls. You may have difficulty distinguishing between two colors of a similar hue when placed side by side.
Poor tolerance for changing light levels
It may become difficult for your eyes to adjust when driving and walking at sunset, or when going from a well-lighted room to a darker one. Glare can worsen the problem. For example, a bright shaft of sunlight streaming in through a window may cause everything outside the glare to "black out."
Need for higher light levels
You may find that you need brighter light levels for reading, cooking and performing day-to-day tasks.
Impaired depth perception
An inability to properly judge distances can also make walking harder, potentially leading to missteps and falls.
Macular Degeneration: Screening & Diagnosis
If you notice a change in your central vision, you should have your eyes checked by an ophthalmologist. This type of doctor specializes in the:
- Medical and surgical care of the eyes and visual system
- Prevention of eye disease and injury
To help diagnose macular degeneration, an ophthalmologist or optometrist will perform a comprehensive eye exam that may include the following tests:
Autofluorescence
Eye care professionals use autofluorescence photos to study the retina and measure the progression of geographic atrophy in patients with advanced, dry AMD.
Doctors can use this technique to monitor the retinal pigment epithelium (RPE), the deepest layer of the retina:
- RPE cells maintain the function of the light-sensitive cells in the retina (the cells that allow us to see).
- In dry AMD, the RPE layer of the retina thins, eventually causing the death of light-sensitive cells and leading to visual impairment.
- This process is called geographic atrophy, and it occurs in the advanced stage of dry AMD.
Image credit: Relishnah | Wikimedia Commons
Dilated Eye Exam
To view the back of your retina, the doctor dilates the pupils with eye drops. Dilation allows the doctor to study the retina for signs of disease and to determine if there is optic nerve damage.
Fundoscopy or Ophthalmoscopy
After dilating the pupil, the doctor aims a bright beam of light into the eye to check for problems in these parts of the eye:
- Retina: Nerve layer lining the back of the eye
- Choroid: Thin layer connecting blood vessels and nerves to other parts of the eye
- Blood vessels
- Optic disk: Small, circular area in the back eye where the optic nerve connects to the retina
Visual Acuity Test or Eye Chart Test
This test measures your sight from various distances.
Fundus Photography
After dilating the pupil, the doctor focuses light through the cornea, pupil, and lens. He or she uses a customized camera to photograph the back of the eye to look for signs of disease in the:
- Retina
- Macula: Specialized center of the retina, responsible for sight in the center of vision
- Optic nerve: Nerve that carries sensory information related to vision from the retina to the brain
Fundus photography helps the doctor measure changes between visits.
Fluorescein Angiography
If your doctor suspects that you may have the wet type of AMD, he or she may conduct this test to detect leaking blood vessels. The doctor injects fluorescent dye into your arm and traces it through the blood vessels in the retina, where the appearance of fluorescent patches can reveal leakage.
Optical Coherence Tomography (OCT)
OCT is a noninvasive technique to image the retina. OCT produces cross-sectional images of the retina so that the different layers and their thicknesses can be measured. When your doctor suspects advanced dry AMD, this technique can identify regions of the retina that are thinning, indicating the presence of geographic atrophy. Doctors also routinely use this test to assess the retina's response to various treatments.
Tonometry
This test measures the pressure inside the eye. Your doctor will give you a numbing eye drop before this test.
Amsler Grid
The Amsler grid can help detect early signs of retinal disease and also monitor changes in vision after an AMD diagnosis. During an eye exam, the eye care professional may ask you to look at an Amsler grid to check for AMD:
- The grid resembles graph paper in which straight lines intersect at right angles.
- You cover one eye and stare at a black dot in the center of the grid.
- While staring at the dot, if the straight lines in the grid appear wavy or are missing, it could be a sign of AMD.
- The grid should not in any way substitute for the advice of a qualified health care professional: it is not intended to constitute medical advice. However, you may use it for at-home monitoring. View or download a PDF of the Amsler grid eye test.
Photo: Courtesy of ForeseeHome
ForeseeHome Monitoring Device
The ForeseeHome Monitor® is the first FDA-cleared device for patients with dry AMD to monitor the disease at home. It is now a Medicare-covered service for patients enrolled in Medicare across the U.S., and who meet the eligibility criteria for dry AMD at high risk for converting to wet AMD. The device is designed to be used daily and takes approximately 3 minutes per eye. When used daily, the ForeseeHome Monitor detects changes before a patient would notice, and allows the doctor to monitor the vision for any changes that take place between regularly scheduled exams.
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