How Wet Age-Related Macular Degeneration is Diagnosed

In This Article

Tests to diagnose wet age-related macular degeneration (AMD) include an eye examination and a self-test that can be done at home. There are also several imaging tests that an ophthalmologist can use to detect the abnormal blood vessel development (neovascularization) and bleeding that occurs in the eyes of those with wet AMD.

But, it's important to note that wet AMD is not the only cause of these symptoms. Thus, other conditions must be ruled out, before a person can be definitively diagnosed with wet AMD.

Self-Checks/At-Home Testing

The Amsler grid (sometimes referred to as the Amsler chart) is perhaps the most common test that is used at home to screen for the possibility of wet AMD. The Amsler grid had been used since 1945.

The chart displays horizontal and vertical lines used to evaluate and monitor changes in a person's central visual field. The grid was developed by a Swiss ophthalmologist named Marc Amsler.

The Amsler Chart test involves viewing an image of a grid, at regular intervals. The grid can be used to perform ongoing self-eye screenings at home.

An image of the Amsler grid can be downloaded from the American Macular Degeneration Foundation (AMDF) and printed out for use at home. You can also order a magnetic version of the Amsler chart (to hang on the refrigerator) by calling 1-855-345-6637.

When using the Amsler chart, simply check your eyes (one at a time) to see whether the lines look straight or appear wavy or distorted in any way. Other signs to check for include whether areas (such as some of the lines) of the chart appear missing, this indicates that portions of your visual field are absent.

Step by Step Instructions

The instructions for using Amsler’s Chart to test your vision and screen for possible signs of wet AMD include:

  1. Download and print out a copy of the Amsler chart
  2. Tape the chart at eye level in a place with consistent light, that is absent of glare, at about 12 to 14 inches away from you (at a comfortable reading distance).
  3.  If you wear glasses, put them on before conducting the screening.
  4. Cover one eye
  5. Fix your gaze on the dot that appears in the center of the grid.
  6. While keeping your focus on the center dot, see if there are any lines missing, or if there is a distortion (such as wavy, irregular, or fuzzy lines) that appear.
  7. Mark the chart in any area where you see the defect (such as missing lines or distortions)
  8. Be sure to only test one eye at a time
  9. When re-testing, always keep the chart at the same distance each time
  10. If the visual distortion is new, or if it worsens, be sure to contact your ophthalmologist (or other healthcare provider) right away.

The Amsler grid home test should never replace regular eye exams.

If you have noticed distortions in your vision, that are common symptoms of wet AMD, your healthcare provider may recommend further testing. Symptoms that may warrant further diagnostic tests and evaluation for wet AMD may include:

  • Hazy vision
  • Objects that appear skewed
  • Straight lines that appear wavy or curved

These visual disturbances could be a sign of AMD, but they could also be an indicator of other eye conditions.

Eye Examination and Tests

The most common scenario that leads to a diagnosis of AMD is not a person’s self-reported symptoms, but rather, the condition is most often detected during the yearly eye examination.

The initial part of wet AMD diagnostic testing is an eye examination, which takes place after the eyes are dilated. If wet AMD is present, the ophthalmologist sees the presence of drusen (tiny heaps of cell waste on the surface of the retina) as well as macular pigment changes. These changes can often be observed by the eye doctor before symptoms of wet AMD begin.

The macula is considered the functional center of the retina; it functions to process sharp, clear straight-ahead vision (as opposed to peripheral or side vision). The retina is a very thin tissue that lines the back of the eye; it contains the light-sensing cells that send visual signals to the brain.

If a person is diagnosed with dry AMD, the ophthalmologist may recommend regular screening for wet AMD, because the condition often starts as dry AMD and progresses into the wet form of the disease.

Changes in the eye (such as drusen) can often be observed by the eye doctor, even before symptoms begin. This is the reason it’s important to get regular eye exams, particularly for those over age 50 (because the risk of AMD increases with age).

Screening Tools

Visual screening tools are often used for the initial evaluation of eye disorders such as AMD. The ophthalmologist uses an ophthalmoscope or a retinoscope (handheld instrument used to examine the retina) to visually exam the eyes. There are many other tools and pieces of equipment that ophthalmologists commonly use to perform an eye exam.

Standard screening tests for wet age-related macular degeneration may include:

  • A visual acuity exam utilizing the eye chart (letter chart) that has the large capital E at the top
  • The Amsler grid to screen for visual distortions or missing fields of vision.

Genetic Testing

Genetic testing may be employed to screen those who are symptomatic (having symptoms, such as visual loss) for young onset macular degeneration, including a condition called Stargardt disease (a type of juvenile onset macular degeneration). Upon results of genetic testing, there could be an indication of a recessive gene that causes Stargardt disease, or other genetic eye disorders.

Imaging

Imaging tests are commonly used to form a definitive diagnosis of AMD. There are two forms of AMD, the wet form and the dry form. Wet AMD involves new blood vessels that are not formed correctly. These dysfunctional blood vessels burst and cause bleeding in the eye (which is the underlying cause of retinal damage in the macula—the central area of the retina— and vision loss).

This abnormal formation of blood vessels is also referred to as neovascularization. In wet AMD, neovascularization may be seen in or under the retina by means of imaging examinations.

Common imaging tests used to diagnose wet AMD may include:

Fundus Autofluorescence Imaging (AF)

Fundus autofluorescence imaging is a non-invasive test that utilizes the body’s natural fluorescence to examine the retina for signs of wet AMD. This test takes advantage of the body’s natural ability to light up when exposed to certain types of light; the structures that light up are called fluorophores.

AF imaging is often used to detect areas where cells waste away and die (atrophy) in the late stages of wet or dry AMD. The test illustrates atrophied areas that do not light up. These areas of atrophy often cause blind spots in the visual field in those with AMD.

Optical Coherence Tomography (OCT)

Optical coherence tomography is a non-invasive (no injections required) imaging test that shows details of the retina and provides very useful diagnostic information about the telltale signs of wet AMD (such as new/abnormal blood vessels, hemorrhaging, drusen and more).

This test requires that a person receives eye dilation drops. Then the person being examined sits down in front of the imaging equipment for images to be taken.

Indocyanine green angiography (ICGA)

Indo cyanine green angiography is a diagnostic procedure that utilizes green dye to illuminate the blood flow in the choroid. The choroid is a layer of blood vessels located between the white of the eye (called the sclera) and the retina.

The test can help with differential diagnoses because it allows for specific evaluation and analysis of the choroidal circulation. The choroidal circulation is the area in which vascular dysregulation (abnormal blood vessels) occurs in wet AMD.

Differential Diagnoses

Some signs and symptoms of AMD are common in other conditions. When a diagnostic practitioner must consider a person's signs and symptoms to differentiate between various disease entities, it’s called a differential diagnosis.

According to the American Academy of Ophthalmology, ophthalmologists should be suspicious of signs of AMD, such as fluid or blood in the macula, and check for other disease entities. Dr. Randall Wong, a retinal specialist, explains, “Most of the “fakes” are confused with macular degeneration due to the presence of choroidal neovascularization, aka the “wet” form of macular degeneration.”

Differential diagnoses for wet AMD may include:

  • Polypoidal choroidal vasculopathy (PCV): This is a sub-type of AMD, particularly seen in the Asian population; the genes associated with AMD have been observed in those with PVC.
  • Adult-onset vitelliform macular dystrophy (VMD): This is a genetic disorder of the eye that can result in vision loss that occurs progressively over time. This disorder involves fatty yellow pigment that builds up in the cells of the macula, causing an interruption in the normal functioning of the retina. The condition does not respond well to standard AMD treatment; proper diagnosis can help spare patients unnecessary treatment that is ineffective.
  • Stargardt’s disease: This is a common form of juvenile-onset macular degeneration, caused by a genetic defect that results in the death of the eye’s photoreceptors. The condition is known to progress rapidly, causing severe loss of central vision.  Although the condition can begin in early childhood, many times it’s not diagnosed until adulthood.
  • Pathological myopia: This is a condition in which shortsightedness causes degenerative (progressive deterioration or loss of function) changes in the eye; pathological myopia can result in a loss of vision that cannot be corrected with corrective lenses.
  • Angioid streaks: This condition involves tiny breaks in the tissue of the retina (of both eyes) which are seen in those with a rare condition called pseudoxanthoma elasticum. Pseudoxanthoma elasticum causes degeneration of elastic fibers in the retina, skin and blood vessels. Angioid streaks cannot be seen with an ophthalmoscope (the instrument that is commonly used to perform an eye exam) therefore the condition can easily be overlooked when the ophthalmologist performs a standard eye exam. Android streaks can result in blindness.
  • Ocular histoplasmosis syndrome: This syndrome is caused by spores that originate from the lungs and spread to the eyes. The condition causes abnormal blood vessels to grow underneath the retina. These are milar to those found in wet AMD.
  • Central serous chorioretinopathy (CSC): This is a disorder that involves an accumulation of fluid under the retina, which results in a fluid-filled detachment of the retina and vision loss (which may be temporary, but sometimes becomes long-term). Note, in some instances, CSC does not cause any symptoms, it depends upon the location of the sub-retinal (under the retina) fluid, this is true, specifically when the affected area falls outside of the macula.
  • Choroidal injury: Sometimes injuries to the eye (as well as other causes, such as eye surgery) can cause a build up of fluid between the choroid layer of the eye and the retina. This is also called choroidal effusion. The symptoms caused by choroidal effusion can sometimes mimic wet AMD. It’s important to tell your ophthalmologist if you’ve had an eye injury.

A Word From Verywell

There are many eye disorders that can mimic the signs and symptoms of wet AMD. If you have been diagnosed with wet AMD, it’s important to ensure that your diagnosis is correct. This is true of any serious or chronic (long-term) condition.

You may want to consider a second opinion—from another qualified specialist, such as an ophthalmologist—to be sure. Don’t be afraid to ask. It’s not unreasonable to surmise that a diagnosis could possibly be wrong and second opinions can ensure prompt and correct diagnosis, which equates to faster intervention and more effective treatment.

Age-related macular degeneration (AMD) is a condition that causes deterioration of the retina of the eye. It is the leading cause of vision loss in the United States and in many other countries. In fact, it impacts over 10 million Americans. That number represents more than those with glaucoma and cataracts, combined.

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Article Sources
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