Ultrasound biomicroscopy is a high-resolution ultrasound non-invasive eye exam that provides a detailed image or picture of the eye's front part. The technique uses high-energy sound waves to produce near light microscopic resolution images of the inside of the eye for a detailed examination of frontal segment structures.
The ultrasonic waves enjoy a natural benefit of not being obstructed by opaque structures and pigmentation in the eye that limit light-based tomography. Therefore, UBM can provide high-quality images of internal structures that are typically hidden and those obscured by abnormalities, such as cataracts, corneal opacities, etc.
An ultrasound biomicroscopy produces transverse or cross-sectional images of the following structures of the eye:
- Conjunctiva- The thin, transparent material covering the sclera
- Anterior chamber- The small space between the iris and the lens
- Anterior chamber angle- The angle created between the iris and the cornea
- Lens- It sits behind the iris and is responsible for focusing light onto the retina
- Posterior chamber- The area with aqueous humor between the cornea and the iris
- Ciliary body- It releases aqueous humor, the transparent fluid which maintains normal eye pressure
- Iris- The colored circle with a black hole in the middle that regulates the amount of light that enters the eye
- Sclera- It is the posterior white portion of the eye made of sturdy fibrous material. It maintains the eyeball structure and protects the interior parts
- Cornea- The transparent material that covers the iris and pupil. It functions as the outer lens and directs incoming light to the back of the eye through the pupil. It also protects internal structures of the eye
UBM uses a high-frequency ultrasound transducer which was first introduced in 1989 by Prof. Stuart Foster and Dr Charles Pavlin.
It is important to note that the technique is not useful in the case of a patient with an open corneal or scleral wound.
Also Known As
- UBM of the eye
- Ultrasound biomicroscopy (UBM)
UBM of the eye can be conducted at the eye clinic hospital or doctor's office by:
- A technician
- An optometrist
- An ophthalmologist
UBM has become an indispensable instrument in the diagnosis, treatment and management of various eye diseases and conditions. It provides critical data with minimal equipment and discomfort for the patient. In some cases, it is the only available technique for the early detection of abnormalities. However, it is best used together with methods such as OCT, which provide clear signs and set of readings of other deteriorative conditions.
UBM is particularly useful in:
UBM enables the doctor to understand the mechanism of the disease better, allowing for a more effective treatment strategy targeted at the underlying pathophysiology. The ultrasound helps the doctor to identify malignant glaucoma, pupillary block glaucoma, lens-related angle closure, plateau iris configuration, and pigment dispersion syndrome.
- Ciliary body cysts
With or without angle-closure glaucoma, primary iridociliary cysts may push the iris root and cause a pseudo plateau iris configuration. Primary ciliary body cysts happen extemporaneously and are epithelial-lined areas that arise from the pigmented epithelial layer of the ciliary body and the iris. Secondary ciliary body cysts occur due to traumatic implantation of the epithelium from parasitic or metastatic lesions, or after the prolonged use of miotics. Although in most cases the iridociliary cysts are benign and rarely require treatment or cause complications, angle-closure glaucoma can develop where there is an angle of over 180 degrees. Ultrasound biomicroscopy enables the doctor to make an accurate diagnosis by detecting cysts at the ciliary body that imitate the plateau iris syndrome. The disorder is called pseudo plateau iris syndrome and is challenging to detect clinically.
- Eye injuries
It helps to detect angle recession and to examine the iris, angles, ciliary body and the lens, particularly in a situation where there is blood in the front eye chamber which blocks the view in a slit lamp exam.
UBM helps the doctor to see the bleb and tract in cases of failed surgery and also to rule out tenon's cyst or episcleal scarring.
- Other cases include the detection and treatment of
- Nerve diseases
- Tumors of the eye
- Thyroid eye disease
- Optic nerve diseases
- Vitreoretinal diseases
- Inflammatory diseases
- Foreign bodies of the eye
Preparation & Expectation
UBM doesn't require special preparation. The doctor will apply anesthetic drops on the patient's eyes to numb them before the exam. The medication will not dilate the patient's pupils, but it can make vision blurred during the screening. There should be no pain or discomfort. It may be possible for the patient to drive half an hour after the test, but it's advisable that the patient brings someone along or makes arrangements to be driven home after the scan.
The patient will be advised not to rub their eyes until the anesthetic wears off to avoid accidental scratching of the cornea.
The patient will lie down on a couch facing up, and the doctor will apply a gel on the patient's cornea to start the scan. The doctor will put the ultrasound probe on the surface of the patient's eyeball and conduct the scan. The UBM scan takes approximately 10 minutes to complete and is entirely painless.
Ultrasound biomicroscopy provides the doctor with critical information about the state of the patient's eye.
Abnormal results may point to:
- Ciliary body anomalies
There may be opposed or very narrow iridotrabecular angles with cysts at iridociliary junction in all meridians and the iris root. Results may also show ciliary body traction or atrophy, cystic membranes, ciliary body detachments, supraciliary effusion, pars planitis, etc.
The scan may reveal pigment dispersion syndrome, pupillary block glaucoma, lens-related angle closure, plateau iris configuration, or malignant glaucoma.
- Eye injuries
There may be an angle recession or cyclodialysis cleft.
Cancer in the eye, such as melanoma
- Foreign bodies of the eye
The doctor will need to determine the cause and decide the most appropriate treatment for the patient.
Risks & Complications
UBM is a safe procedure with no known risks or complications. The patient, however, will do well to heed the doctor's warning not to rub their eye before the medication has completely worn off. It prevents corneal scratches.