OCT Angiography: Dye-Free Imaging of Your Retina
Understanding OCT Angiography
OCT angiography is a noninvasive imaging technology that takes detailed pictures of the blood vessels inside your eye. It captures images of both the retina (the light-sensitive tissue lining the back of the eye) and the choroid (the layer of blood vessels beneath the retina). The technology was cleared by the U.S. Food and Drug Administration for clinical use. It has rapidly gained acceptance among retina specialists since then.
Over 150 million OCT scans are performed worldwide each year (Astute Analytica, 2024). Ophthalmology accounts for approximately 64.5% of all OCT imaging use (GM Insights, 2024). OCTA represents the newest advancement within this widely used imaging family.
OCTA uses the movement of red blood cells inside your blood vessels to create images. The device rapidly scans the same area of your retina multiple times. Because red blood cells are constantly moving while the surrounding tissue stays still, the technology can separate the two. This creates what specialists call a motion-contrast image. It is essentially a map of where blood is flowing and where it is not.
The result is a three-dimensional picture of the blood vessel networks at different depths within your retina and choroid. No dye or injection is needed to produce these detailed images.
Fluorescein angiography is an older imaging test that requires a yellow-green dye to be injected into a vein in your arm. The dye travels through your bloodstream and into the blood vessels of your eye. A special camera then photographs the vessels. While effective, this test carries a small risk of allergic reactions. It can also cause temporary nausea or skin discoloration.
OCTA provides similar vascular detail without any dye injection. It also provides depth-resolved images, meaning it can show blood vessels at specific layers within the retina. However, OCTA cannot detect leakage from blood vessels, which fluorescein angiography can show. For this reason, retina specialists sometimes use both tests together.
One of the key strengths of OCTA is its ability to show blood vessels at different depths within the eye. The technology can generate separate images of several important vascular layers.
- The superficial capillary plexus (the network of tiny blood vessels near the inner surface of the retina)
- The deep capillary plexus (a deeper network of blood vessels within the retina)
- The choriocapillaris (the dense layer of blood vessels just beneath the retina)
- The foveal avascular zone, or FAZ (a small area in the center of the macula that normally has no blood vessels)
Why This Test Matters for Your Eye Health
Many retinal conditions involve subtle changes to the blood vessels in the back of the eye. These changes can occur before you notice any symptoms. OCTA allows retina specialists to detect early vascular changes that might not be visible during a standard eye exam.
In diabetic retinopathy, for example, OCTA has been instrumental in identifying early retinal changes. It offers measurable data such as perfused capillary density. This helps specialists assess how well blood is flowing through the retinal vessels. Detecting these changes early can guide treatment decisions before significant vision loss occurs.
Because OCTA is quick and does not require dye, it can be repeated at regular intervals without significant inconvenience or risk. This makes it an ideal tool for tracking how a condition changes over time. A retina specialist can compare OCTA scans from different visits to determine whether a disease is stable, improving, or getting worse.
The scan provides quantifiable measurements including vessel density, FAZ area, and FAZ circularity. These numbers give retina specialists an objective way to monitor your condition.
OCTA findings can directly influence how a retina specialist approaches treatment. The test can reveal areas of poor blood flow, abnormal new blood vessel growth (neovascularization), or microaneurysms (tiny bulges in blood vessel walls). Each of these findings may point toward a different treatment strategy.
When neovascularization is detected in conditions such as wet AMD or diabetic retinopathy, it may indicate the need for anti-VEGF injections. These medications block vascular endothelial growth factor (VEGF), a protein that drives abnormal blood vessel growth. OCTA helps retina specialists identify neovascularization and track the response to treatment over time.
Conditions Evaluated with OCT Angiography
In the wet form of age-related macular degeneration (AMD), abnormal blood vessels grow beneath or within the retina. This process is called macular neovascularization. OCTA can detect these abnormal vessels without the need for dye injection. This helps retina specialists confirm a diagnosis and monitor how well anti-VEGF treatments are working.
Common anti-VEGF medications used for wet AMD include Eylea (aflibercept), Lucentis (ranibizumab), and Vabysmo (faricimab). OCTA allows retina specialists to track whether these abnormal vessels are shrinking, stable, or growing after treatment begins. It is important to note that anti-VEGF injections are used specifically for wet AMD and are not a treatment for dry AMD.
Dry AMD is a separate condition from wet AMD and involves different changes in the retina. In dry AMD, OCTA can reveal changes in the choriocapillaris that may indicate areas at risk for progression to geographic atrophy. Geographic atrophy is an advanced stage of dry AMD where retinal cells are permanently lost.
This information is valuable for determining whether a patient may benefit from newer treatments. Syfovre (pegcetacoplan), a complement inhibitor, and Izervay (avacincaptad pegol), a complement C5 inhibitor, are approved specifically for geographic atrophy. These treatments slow progression but do not restore lost vision. OCTA helps monitor the condition over time.
Diabetes can damage the small blood vessels of the retina over time. OCTA provides detailed maps of this damage. It shows areas where blood vessels have been lost or where abnormal vessels have started to grow. Retina specialists use these images to determine the stage of diabetic retinopathy and to plan treatment.
OCTA measurements such as vessel density and the size of the foveal avascular zone are key metrics. They help grade the health of the retinal microcirculation in patients with diabetes.
A retinal vein occlusion (a blockage in one of the veins that drains blood from the retina) can cause swelling, bleeding, and vision loss. OCTA helps retina specialists visualize the extent of the vascular damage. It can identify areas of poor blood flow and detect any new abnormal vessels that may have formed as a result of the blockage.
OCTA has proven useful in evaluating several additional conditions that affect the retinal blood vessels.
- Retinal arterial occlusion (a blockage in an artery supplying the retina)
- Uveitis (inflammation inside the eye that can affect retinal blood vessels)
- Macular telangiectasia (abnormal dilation of small blood vessels near the center of the retina)
What to Expect During the Test
In most cases, your eyes will be dilated with eye drops before the OCTA scan. Dilation widens your pupil and allows the device to capture a clearer image of your retina. The drops take about 15 to 30 minutes to take full effect. Your vision may be blurry and your eyes may be sensitive to light for a few hours afterward.
No fasting is required, and you can take your regular medications as usual before the appointment. If you wear contact lenses, you may be asked to remove them before the scan.
The OCTA scan itself is quick and comfortable. You will sit in front of the imaging device and rest your chin on a support. The technician will ask you to look at a small target light inside the machine. The device scans your retina using infrared light, which you cannot feel. The entire scan typically takes only a few minutes per eye.
Holding your gaze steady on the target light is important. Patient movement during the scan can cause artifacts (errors in the image) that may reduce image quality. If you have difficulty holding still, the technician may repeat the scan.
There is no recovery time needed from the OCTA scan itself. If your eyes were dilated, the effects of the drops will wear off within a few hours. You may want to bring sunglasses for the ride home.
Your retina specialist will review the OCTA images and discuss the findings with you, often at the same visit. The images are stored digitally so they can be compared with future scans to track any changes over time.
Benefits and Limitations of OCTA
OCTA offers several significant benefits compared to older imaging methods. Understanding these advantages can help explain why your retina specialist may recommend this test.
- No dye injection is needed, eliminating the risk of allergic reactions associated with fluorescein dye
- The scan is fast, typically completed in just a few minutes
- It provides depth-resolved images, allowing visualization of different vascular layers
- Results are available immediately, often reviewed during the same visit
- The test can be repeated frequently for ongoing monitoring without added risk
While OCTA is a powerful tool, it does have limitations that are important to understand. One key limitation is that OCTA cannot detect leakage from blood vessels. For conditions where leakage is critical for diagnosis, fluorescein angiography may still be necessary.
Image quality can be affected by several factors. Patient movement can cause artifacts including vessel duplication and vessel discontinuity. Media opacities such as cataracts can also interfere with signal detection. Additionally, different OCTA devices segment and analyze retinal layers differently. This means measurements from one device may not be directly comparable to another.
One specific type of artifact that can affect OCTA images is called a projection artifact. This occurs when the signal from blood vessels in the superficial retinal layers is projected onto deeper layers. It can make it appear as though blood vessels exist where none are present. Modern OCTA software includes correction tools to minimize this issue. Retina specialists remain aware of this limitation when interpreting scans.
Emerging Research and Future Directions
A collaborative initiative involving four prominent retina societies developed a consensus framework for OCTA terminology. These societies include the European Society of Retina Specialists, the Japanese Retina and Vitreous Society, the American Society of Retina Specialists, and the International Retinal Imaging Society. Retinal imaging specialists, basic researchers, and biomedical engineers worked together to standardize how OCTA images are described and analyzed.
A growing area of research explores the use of OCTA metrics as potential biomarkers for cardiovascular disease. The blood vessels in the retina are some of the smallest in the body. Changes visible on OCTA may reflect broader vascular health. A comprehensive review found 50 peer-reviewed studies examining the relationship between OCTA measurements and cardiovascular conditions (PubMed systematic review). Reduced vessel density on OCTA has been reported in patients with poorly controlled high blood pressure.
The technology continues to evolve. In September 2024, Topcon received U.S. FDA clearance for its combined OCTA, OCT, and color fundus camera system (FDA, 2024). Effective January 1, 2025, a new billing code (CPT 92137) was established specifically for OCTA. This recognizes it as a distinct diagnostic procedure. The adoption of handheld OCT devices in ophthalmology clinics reached 67% in 2023, up from 42% in 2018 (Astute Analytica, 2024). This reflects how rapidly the technology is expanding access to advanced imaging.
When to See a Retina Specialist
If you have been diagnosed with a retinal condition such as diabetic retinopathy, age-related macular degeneration, or a retinal vein occlusion, your retina specialist may recommend periodic OCTA scans. These scans help track changes in your retinal blood vessels over time. They can inform decisions about when to adjust treatment.
Certain symptoms involving your vision should prompt you to see a retina specialist or go to the emergency room immediately. These include a sudden increase in floaters, flashes of light in your vision, a curtain or shadow spreading across your field of vision, or sudden vision loss in one eye. While OCTA is a diagnostic tool rather than an emergency procedure, a retina specialist may use it along with other tests to evaluate these symptoms.
Questions and Answers
Yes. Because OCTA does not use any injected dye, it is a safe imaging option for people who have experienced allergic reactions to fluorescein or other contrast agents. The scan uses only infrared light to create images of the retinal blood vessels. If you have a history of dye allergies, let your retina specialist know so they can plan your imaging accordingly.
The scan itself typically takes only a few minutes per eye. However, your total appointment time may be longer because your eyes usually need to be dilated before the scan. Dilation takes about 15 to 30 minutes. Your retina specialist may also perform additional tests or a clinical examination during the same visit.
OCTA has replaced fluorescein angiography for many clinical situations, but it has not fully replaced it. Because OCTA cannot detect leakage from blood vessels, fluorescein angiography remains necessary for certain conditions. Many retina specialists use both tests together when needed to get the most complete picture of what is happening inside the eye.
In many cases, yes. OCTA can reveal subtle changes in retinal blood vessel density, blood flow patterns, and the size of the foveal avascular zone before these changes cause noticeable symptoms. This is one of the reasons retina specialists value OCTA as a screening and monitoring tool. It is particularly useful for patients with diabetes or other conditions that increase the risk of retinal disease.
The OCTA scan itself causes no pain or discomfort. The device does not touch your eye. The only potential discomfort comes from the dilating eye drops, which may cause a brief stinging sensation when applied. After dilation, your eyes will be more sensitive to light for several hours. Bringing sunglasses to your appointment is recommended.