High-frequency ultrasound biomicroscopy (UBM) provides high-resolution in vivo imaging of the anterior segment (Fig 2-6). Tissues visualized include the cornea, the anterior and posterior surface of the iris, the ciliary body, zonular fibers, angle structures, and the anterior lens capsule. UBM technology incorporates 50–100-MHz transducers into a B-mode clinical scanner. Paradigm Medical Industries (Salt Lake City, UT) and Ophthalmic Technologies (Toronto, ON, Canada) UBM scanners utilize 50-MHz transducers and provide axial and lateral physical resolutions of 25 μm and 50 μm, respectively. UBM allows structures to be viewed through an opaque cornea and total hyphema. The scleral spur, located where the trabecular meshwork meets an interface line between the sclera and ciliary body, is a constant landmark that aids the clinician in the examination of various angle configurations.
Figure 2-6 Ultrasound biomicroscopic visualization of the entire anterior segment, including structures behind the iris pigment epithelium, thereby permitting precise determination of the sulcus-to-sulcus measurements prior to implantation of a phakic refractive intraocular lens.
(Reproduced from Goins KM, Wagoner MD. Imaging the anterior segment. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2009, module 11.)
UBM is a helpful adjunct in the assessment of ciliary body pathology, including cysts and tumors. It is also very useful in the evaluation of various angle anomalies, including angle recession, occludable angles, pupillary block, plateau iris, malignant glaucoma, and cyclodialysis clefts. In addition, clinicians can use UBM to assist with accurate placement of phakic intraocular lenses (IOLs), identify pigment dispersion syndrome, and locate IOL haptic positions and foreign bodies in the angle. Its major advantage is its ability to visualize structures behind the iris; most of its other capabilities in visualizing the anterior segment have been supplanted by anterior segment optical coherence tomography.
Goins KM, Wagoner MD. Imaging the anterior segment. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2009, module 11.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.