Ophthalmic Ultrasound: Seeing Inside Your Eye
Understanding Ophthalmic Ultrasound
Ophthalmic ultrasound, also called ocular ultrasound or eye ultrasound, is a diagnostic imaging technique. It uses high-frequency sound waves to produce detailed images of the structures inside and behind your eye. Unlike other imaging tests that rely on light, ultrasound can see through blood, dense cataracts, and other blockages that would otherwise prevent your retina specialist from viewing the back of your eye.
The first ocular echogram was published in 1956. Since then, ophthalmic ultrasound has grown into a vital diagnostic tool used in retina clinics worldwide. Approximately 19,000 practicing ophthalmologists in the United States serve a population increasingly affected by age-related vision disorders, sustaining strong demand for this technology (AAO, via Data Horizon Research).
During an ultrasound, a small probe sends high-frequency sound waves into your eye. These sound waves bounce off the different tissues inside your eye and return to the probe. A computer then converts these returning echoes into a picture that your retina specialist can study.
The quality of the image depends on the density of the tissues the sound waves encounter. When sound waves hit the boundary between two tissues of different densities, they reflect back more strongly. Denser structures produce brighter spots on the image, while fluid-filled spaces appear darker. This contrast allows your retina specialist to identify specific structures, abnormalities, and conditions within the eye.
There are three main types of ophthalmic ultrasound, each designed for different purposes.
- A-scan (amplitude scan) uses a single sound beam at about 8 MHz to create a one-dimensional image. Spikes on the image correspond to different tissue densities. A-scan is most often used to measure the length of the eye before cataract surgery.
- B-scan uses a sound frequency of about 10 MHz to create a two-dimensional, cross-sectional image of the eye. This is the most commonly used type in retina care. It allows a retina specialist to view the internal structure of the eye even through a dense cataract or bleeding inside the eye.
- Ultrasound biomicroscopy (UBM) uses much higher frequencies of 35 to 100 MHz. These higher frequencies provide extremely detailed images of the front part of the eye, including structures behind the iris that cannot be seen during a standard exam.
Why Ophthalmic Ultrasound Is Needed
The most common reason for an ophthalmic ultrasound is that your retina specialist cannot get a clear view of the back of your eye using standard lights and lenses. This most often happens when there is too much bleeding inside the eye, a condition called vitreous hemorrhage. Blood in the vitreous gel (the clear gel that fills the inside of the eye) blocks the view of the retina, much like fog blocks the view of a road.
Other situations that may require ultrasound include severely advanced cataracts, corneal scarring, or other conditions that make the eye's natural optical pathway cloudy. In all of these cases, ultrasound provides a way to assess the retina when no other imaging method can.
Retinal detachment is a serious condition in which the retina pulls away from its normal position at the back of the eye. Without prompt treatment, it can cause permanent vision loss. On ultrasound, a retinal detachment appears as a bright, membrane-like structure that moves in a serpentine or wave-like motion when the eye moves. This distinctive appearance helps your retina specialist quickly confirm or rule out a detachment, even when the retina cannot be seen directly.
When bleeding occurs inside the eye, it fills the vitreous cavity and blocks the view of the retina. On ultrasound, vitreous hemorrhage appears as scattered, swirling material within the eye that moves when you look in different directions. Beyond simply confirming the bleeding, ultrasound helps your retina specialist determine whether a more serious problem, such as a retinal tear or detachment, is hiding behind the blood.
Ophthalmic ultrasound plays an important role in detecting and monitoring tumors inside the eye. The reflectivity, internal structure, and sound attenuation patterns of a mass on ultrasound help distinguish between different types of growths. This information is essential for guiding treatment decisions. Ultrasound can also identify foreign bodies inside the eye after trauma, evaluate the structures behind the eye (the orbit), and assess the health of the eye wall.
Who May Need This Test
Anyone whose retina specialist cannot see the back of the eye clearly during an examination may need an ophthalmic ultrasound. This includes people with dense cataracts that block light from reaching the retina and people with corneal scarring or swelling that prevents a clear view.
Diabetic retinopathy affects approximately 9.6 million adults in the United States (CDC). People with advanced diabetic eye disease are at higher risk for vitreous hemorrhage, which can block the view of the retina. In these cases, B-scan ultrasound becomes a critical tool for evaluating the health of the retina and guiding treatment planning.
The World Health Organization reports that approximately 2.2 billion people globally experience some form of vision impairment, including many conditions that may require ultrasound evaluation (WHO). Cataracts affect more than 24.4 million Americans aged 40 and older, with that number projected to reach 38.5 million by 2030 (NEI). As these conditions become more common, the need for ophthalmic ultrasound in preoperative assessment and surgical planning continues to grow.
After eye trauma, ultrasound can help assess damage inside the eye that may not be visible during a standard exam. However, in cases of potential globe perforation (a break in the wall of the eye), even gentle ultrasound must be used with extreme caution. In those situations, other imaging methods such as a CT scan may be considered first to evaluate the eye's structural integrity.
What Happens During the Test
Ophthalmic ultrasound requires very little preparation. You do not need to fast or stop any medications before the test. Your retina specialist may ask you to remove contact lenses. In most cases, numbing eye drops (topical anesthetic) are placed on the surface of your eye before the exam begins. These drops work within seconds and keep you comfortable during the test.
For a B-scan, a small amount of gel is placed on the ultrasound probe or on the surface of your eye. In general, the B-scan probe is placed directly on the numbed eye for the best image quality. This direct contact makes it easier for both you and the examiner to confirm the exact position of your gaze during the test.
Your retina specialist will ask you to look in specific directions while the probe gently rests on or near your eye. The probe sends sound waves into the eye and captures the returning echoes. The entire process usually takes between 10 and 20 minutes. You may feel light pressure but should not feel pain.
In some cases, the ultrasound probe is placed over the closed eyelid instead of directly on the eye. This approach is preferred for children (pediatric patients) and for people who have experienced eye trauma. The closed-lid technique provides an added layer of protection for the eye while still producing useful images.
There is no recovery time needed after an ophthalmic ultrasound. The numbing drops wear off within about 15 to 30 minutes. Your vision may be slightly blurry for a short time from the gel, but this clears quickly. You can return to normal activities right away, including driving, unless your retina specialist advises otherwise based on your overall eye condition.
Understanding Your Results
On a normal B-scan ultrasound, the vitreous cavity appears as a dark, uniform space. The retina lies flat against the back wall of the eye and shows up as a thin, bright line. The optic nerve appears as a distinct structure at the back of the eye. Normal results mean that no retinal detachment, hemorrhage, tumor, or other structural abnormality was found.
Abnormal findings on ophthalmic ultrasound may include a retinal detachment (a bright membrane with serpentine motion), vitreous hemorrhage (swirling material inside the eye), a mass or tumor (a solid or partially solid structure with characteristic echo patterns), or posterior vitreous detachment (separation of the vitreous gel from the retina). Your retina specialist will explain your specific results and what they mean for your care plan.
The information gathered from an ophthalmic ultrasound directly influences treatment decisions. If a retinal detachment is found, surgical repair such as vitrectomy (a surgery to remove the gel inside the eye) or other procedures may be recommended promptly. If vitreous hemorrhage is identified without an underlying detachment, your retina specialist may recommend observation to allow the blood to clear on its own, or may plan further intervention based on the cause and severity of the bleeding.
Advances in Ophthalmic Ultrasound
Annular array devices represent one of the most recent developments in ophthalmic ultrasound. These probes use multiple sound-emitting elements that can focus at different depths, especially at higher frequencies around 20 MHz. This improvement provides sharper images with better resolution, adding important diagnostic detail at the vitreoretinal interface (where the vitreous gel meets the retina), the eye wall, and the orbit.
Ultrasound biomicroscopy (UBM) uses frequencies of 50 MHz and higher. These very high frequencies produce extremely detailed images of the front part of the eye, though they do not penetrate deeply enough to image the retina. UBM is particularly useful for evaluating structures behind the iris, such as the ciliary body and the angle where fluid drains from the eye.
The integration of artificial intelligence and machine learning into ophthalmic ultrasound is an active area of development. Automated diagnostic algorithms may soon help retina specialists analyze ultrasound images more quickly and accurately. These tools have the potential to enhance diagnostic efficiency and support earlier detection of sight-threatening conditions. As three-dimensional ultrasound imaging and real-time Doppler techniques continue to improve, the role of ultrasound in retina care is expected to expand further.
When to See a Retina Specialist
Certain vision changes can indicate a serious retinal problem that needs urgent evaluation. See a retina specialist or go to the emergency room immediately if you experience any of the following symptoms.
- A sudden increase in floaters (spots or strings drifting across your vision)
- Flashes of light in one or both eyes
- A curtain, shadow, or dark area spreading across your vision
- Sudden vision loss in one eye
You may be referred for an ophthalmic ultrasound if your retina specialist or other eye care provider cannot see the back of your eye clearly during a dilated exam. This could be due to a dense cataract, bleeding inside the eye, or other conditions that block the view. If you have diabetes, a history of retinal problems, or have experienced eye trauma, your provider may use ultrasound as part of your ongoing monitoring and care.
Questions and Answers
Ophthalmic ultrasound is considered very safe for most patients. It uses sound waves, not radiation, so there is no exposure to X-rays or other forms of ionizing radiation. The main precaution applies to people with a suspected globe perforation (a break in the wall of the eye). In those cases, even gentle pressure from the ultrasound probe could worsen the injury, so other imaging methods like CT scan are typically used first.
Most people report little to no discomfort during the test. Numbing eye drops are applied before the probe touches the surface of your eye. You may feel light pressure, but pain is uncommon. The gel used during the test may cause mild, temporary blurriness that resolves quickly. If the test is performed over a closed eyelid, you will feel only gentle pressure on the lid.
Optical coherence tomography (OCT) uses light waves to create detailed cross-sectional images of the retina. OCT provides extremely high-resolution images but requires a relatively clear optical path. If blood, a dense cataract, or other opacity blocks the light, OCT cannot produce a useful image. Ophthalmic ultrasound uses sound waves instead of light, which allows it to penetrate through opaque media. The two tests provide complementary information, and your retina specialist may use both depending on your specific situation.
A typical ophthalmic ultrasound takes about 10 to 20 minutes. There is no recovery time, and the numbing drops wear off within about 15 to 30 minutes. In most cases, you can drive and resume normal activities immediately after the test. However, if you received other treatments or dilating drops during the same visit, your retina specialist will advise you on any driving restrictions.
Some conditions require repeated ultrasound exams to monitor changes over time. For example, if you have vitreous hemorrhage, your retina specialist may perform follow-up ultrasounds to check whether the bleeding is clearing and to watch for complications like retinal detachment. If a tumor or other mass is being monitored, periodic ultrasounds help track any changes in size or characteristics. Your retina specialist will determine the appropriate schedule based on your individual condition.