How Wet Age-Related Macular Degeneration Is Diagnosed

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.

Tests to diagnose wet 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.

However, it's important to note that wet AMD is not the only cause of these symptoms. Therefore, 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 and is 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 grid can be used to perform ongoing self-eye screenings at home.

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 of the chart (such as some of the lines) appear missing, which would indicate a visual field defect.

Step-by-Step Instructions

To use the Amsler chart to test your vision and screen for possible signs of wet AMD, follow these steps:

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.

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

Eye Examination and Tests

Macular degeneration can be discovered via symptoms that you notice at home, but also can be diagnosed during a scheduled yearly eye exam.

The initial part of wet AMD diagnostic testing is an eye examination, which takes place after the eyes are dilated. If macular degeneration is present, the ophthalmologist sees the presence of drusen (cellular debris present under the retina) as well as macular pigment changes. These changes can often be observed by the eye doctor before visual symptoms occur.

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 vision screening to monitor for progression of macular degeneration. Sometimes, dry AMD can progress into wet AMD.

Screening Tools

Visual screening tools are often used for the initial evaluation of eye disorders such as AMD. The ophthalmologist uses an ophthalmoscope to visually examine 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 with the large capital E at the top), called a Snellen visual acuity test
• The Amsler grid to screen for visual distortions or missing fields of vision

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 the following.

Fluorescein Angiography (FA) and Indocyanine Green Angiography (ICG)

Both of these tests involve examining blood vessels in the eye with the assistance of dye injected intravenously (by IV) into the bloodstream.

In fluorescein angiography, yellow dye is given, which causes the blood vessels in the choroid to fluoresce, or shine brightly. This makes them easier to see.

The choroid is a layer of blood vessels located between the white of the eye (called the sclera) and the retina. The choroidal circulation is where vascular dysregulation (abnormal blood vessels) occurs in wet AMD.

Indocyanine green angiography is a similar test that utilizes green dye instead and has certain advantages compared to fluorescein.

Optical Coherence Tomography (OCT)

Optical coherence tomography is a non-invasive imaging test (no injections required) 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).

Fundus Autofluorescence Imaging (FAF)

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.

FAF 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.

Differential Diagnoses

Some of the symptoms of macular degeneration are common in other conditions. According to the American Academy of Ophthalmology, ophthalmologists should be alert for other conditions that present like wet macular degeneration. 

When a diagnostic practitioner must consider a person's signs and symptoms to differentiate between various diseases, it’s called a differential diagnosis. Differential diagnoses for wet AMD may include:

• Polypoidal choroidal vasculopathy (PCV): This is a sub-type of AMD, particularly seen in Asian populations; the genes associated with AMD have been observed in those with PVC.
• Adult-onset vitelliform macular dystrophy: 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, in many cases 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 ameliorated with corrective lenses.
• Angioid streaks: This condition involves tiny breaks in the tissue of the retina (of both eyes) that 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 can be seen with an ophthalmoscope (the instrument that is commonly used to perform an eye exam). Angioid streaks can result in blindness.
• Ocular histoplasmosis syndrome: This syndrome can develop in people who have the fungal lung infection histoplasmosis. The condition causes scarring and abnormal blood vessel growth underneath the retina. These vessels are similar 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). In some instances, CSC does not cause any symptoms if the area of sub-retinal fluid 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, much like wet AMD. This is also called choroidal neovascularization. The symptoms of choroidal neovascularization 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.

However, wet macular degeneration is an urgent matter that should be treated as soon as possible. Delaying treatment may result in permanent vision loss. If you notice any changes in your vision, be sure to see an eye care specialist as soon as possible.