How Geographic Atrophy Is Diagnosed

If you have late age-related macular degeneration (AMD), one of the things an ophthalmologist (eye doctor) will look for each visit are signs of geographic atrophy.

They commonly recommend undergoing imaging testing, ranging from retinal fundus photography (a color image of the retina) to autofluorescence imaging (which shows where geographic atrophy is occurring). These can light up problem areas and show everything from protein deposits to fluid under the retina.

This article will discuss steps you can take at home to monitor for geographic atrophy, what to expect from the ophthalmic exam, and how imaging tests can help. It will also highlight some look-alike conditions that may mimic geographic atrophy.

Self-Checks/At-Home Testing

While an ophthalmologist will play an essential role in checking to see if you have developed geographic atrophy and if it is progressing, you can also play a part. Here are some tests that can potentially help put you in control of the monitoring process.

Amsler Grid

The Amsler grid is a visual field test that can be used at home to check for blank spots in your vision daily. It is a grid-like pattern you can print out. Then, with one eye covered, you can focus on the dot at the center and look to see if any of the perpendicular lines appear to be missing.

If a portion of a line is gone, this might indicate you are losing some vision to geographic atrophy. Any vision loss detected should immediately be reported to your ophthalmologist.

Home Monitoring

You can also use a home monitoring test to check your central vision. With a system such as the ForeSee Home monitoring system (a Food and Drug Administration-cleared device), you use a device to test your vision daily. During the test, you mark where you see a disruption in a line. Then a new line will appear, and you repeat the process.

The test takes about three minutes. The results are sent to a monitoring center where they can check for any vision changes since your last test.

Physical Examination

As someone with macular degeneration, you will be regularly monitored for signs of the disease progressing. Unlike the at-home approach, where you test your vision, the ophthalmologist checks you during an office visit.

To help determine if you have signs of geographic atrophy, the ophthalmologist will put drops in your eye to dilate (widen) your pupil (the dark spot at the center of the colored iris). They will then look inside the eye to see if there are any spots on the retina (a light-sensitive layer in the back of the eye) where some of the dark pigment typically seen is gone.

By viewing this area, the ophthalmologist can confirm that this is geographic atrophy and determine how extensive the affected area may be.

On average, a physical eye exam is given roughly every six months. But every case progresses at its own rate, so a follow-up may be more or less frequent for you.

Don’t be surprised if, during the exam, the ophthalmologist asks you about environmental and other factors that may be linked to the development of geographic atrophy. Some information they may inquire about includes the following:

• If you have any family history of geographic atrophy
• Whether you are currently or have previously been a smoker
• If you take any thyroid or antacid medication
• Whether you’ve had a cataract removed (because the lens inside your eye becomes cloudy)
• If you have any history of heart problems

Labs and Tests

In making a diagnosis, an ophthalmologist will not prescribe any blood work or other laboratory testing. There are no such tests available to diagnose geographic atrophy. The ophthalmologist must make the diagnosis with a physical examination and imaging.

Imaging

You must undergo several imaging tests to determine if you have geographic atrophy, including some you may have had for macular degeneration in general. These include the following.

Fundus Autofluorescence

In geographic atrophy, there is a loss of retinal pigment epithelium. This is a pigmented layer of cells between the cells in the retina that detect light and the layer beneath that has blood vessels to nourish the retina.

Undergoing fundus autofluorescence is standard in making a diagnosis. This technology can show where the retinal pigment epithelium is present. The test shows a dark patch in areas where the retinal pigment epithelium is no longer there.

The retinal pigment epithelium contains a substance known as lipofuscin that can absorb a particular wavelength of light and, in turn, emit light of a different wavelength. This makes it possible to determine where the geographic atrophy is located.

Optical Coherence Tomography (OCT)

With optical coherence tomography (OCT), it’s possible to create a cross-sectional view of the retina on a computer screen. OCT relies on infrared light reflected off the retina to show where retinal tissue is thinning from geographic atrophy.

Retinal Fundus Photography

The retinal fundus photography technique involves getting a color image of the retina and only takes about one minute. On the fundus photograph, the ophthalmologist can identify those areas of the retina where the cells have atrophied (died). You can then compare this initial photograph to ones taken on other dates.

Differential Diagnosis

Just because some cell atrophy is seen by your ophthalmologist or found during the imaging process does not necessarily mean it results from geographic atrophy. It is also possible that the atrophy is limited and caused by anti-vascular endothelial growth factor (VEGF) injections given to treat wet macular degeneration (in which abnormal blood vessels invade the retina and leak).

Or, you may be dealing with what’s known as pattern dystrophy, an inherited disorder whose symptoms are similar to age-related macular degeneration. However, pattern dystrophy tends to be less severe than AMD. While you may still experience some blurring with pattern dystrophy, it’s possible to continue reading and driving.

Although symptoms progress with pattern dystrophy, this usually happens at a much slower pace, over decades, than AMD.

Summary

To help determine if you have geographic atrophy, an ophthalmologist will examine your eyes through a widened pupil and perform imaging tests, such as fundus autofluorescence, optical coherence tomography (OCT), and retinal fundus photography.

These tests will help show whether your retinal tissue is intact or if it has been damaged and how large the affected area is.

A Word From Verywell

If you are undergoing testing for geographic atrophy, remember that damage could be due to pattern dystrophy, a less severe condition with similar symptoms. If geographic atrophy is determined, speak to your ophthalmologist for support and to assess treatment options.