Retinal detachment is an eye condition where the retina, the light-sensitive tissue lining the back of the eye, pulls away from its supporting layers. This separation disrupts the retina’s ability to send visual signals to the brain, leading to blurry vision or permanent vision loss if not treated promptly. When direct observation of the retina is difficult, a B-scan ultrasound helps eye care professionals assess the back of the eye and confirm conditions like retinal detachment.
What is a Retinal B-Scan?
A retinal B-scan, or Brightness scan, is a non-invasive imaging method that uses high-frequency sound waves to create a two-dimensional image of the eye’s internal structures. This technology is useful for visualizing areas of the eye obscured from direct view. For example, dense cataracts, bleeding within the eye (vitreous hemorrhage), or corneal cloudiness can block light for a traditional examination.
A specialized probe emits sound waves, typically 10 to 20 MHz, placed gently on the closed eyelid or directly on the eye after numbing drops. These sound waves travel through eye tissues. When they encounter structures with different densities, such as the boundaries between the vitreous gel and the retina, they reflect back to the probe as echoes.
The probe converts these echoes into electrical signals, which a computer processes to generate a real-time, two-dimensional image. The “brightness” in B-scan represents echo intensity: stronger echoes from denser tissues appear brighter, while weaker echoes appear in varying shades of gray or black. This allows eye care professionals to see a cross-sectional view of the eye’s internal anatomy, including the retina, vitreous, optic nerve, and choroid.
When a B-Scan is Necessary
An ophthalmologist recommends a B-scan when direct visualization of the retina and other posterior eye structures is not possible due to cloudy or opaque media within the eye. Common scenarios include severe vitreous hemorrhage, advanced cataracts, or significant corneal opacities that prevent light from entering the eye. The B-scan is also used when the pupil cannot be adequately dilated, such as in cases of severe inflammation (uveitis) or certain medications, which limits the view of the back of the eye.
It helps diagnose or monitor retinal detachment by providing a clear image of the retinal status, even when a direct view is impaired. The scan can also assess the extent of a detachment or identify other issues in the back of the eye, such as intraocular tumors or foreign bodies, that might mimic retinal detachment symptoms.
What to Expect During the Procedure
A retinal B-scan is a straightforward and painless procedure performed in an ophthalmologist’s office. The patient sits comfortably in a reclined chair. A clear, water-soluble gel is applied to the closed eyelid to ensure good contact with the ultrasound probe.
A small, handheld ultrasound probe is then gently placed on the gel-covered eyelid. If numbing drops are used, the probe may be placed directly on the eye’s surface. The technician moves the probe in different directions to capture images from various angles, allowing for a comprehensive evaluation.
The patient may be asked to move their eye in specific directions to help visualize different retinal areas. The entire process is quick, often taking less than a minute.
Interpreting the B-Scan Findings
The B-scan images provide information for diagnosing retinal detachment and distinguishing it from other conditions. A detached retina appears as a bright, reflective membrane that may show an undulating or wavy movement when the eye is dynamically scanned. This contrasts with a posterior vitreous detachment, where the vitreous gel pulls away from the retina, appearing as a less reflective membrane that moves differently.
The scan can also differentiate between types of retinal detachments, such as rhegmatogenous (caused by a tear) versus exudative (caused by fluid buildup without a tear). It also aids in distinguishing retinal detachment from other conditions with similar symptoms, like vitreous hemorrhage without a detachment or choroidal detachment.
For instance, a choroidal detachment appears as a scalloped-shaped elevation, different from a retinal detachment. The B-scan images guide the ophthalmologist in formulating an accurate diagnosis and determining the most appropriate treatment.